You searched for subject:(Numerical simulation). Showing records 1 – 30 of 1838 total matches.
1. Foster, Ryan Napoleon. Web based interface for numerical simulations of nonlinear evolution equations.
▼ In Computational Science and Parallel Computing research, model equations have been developed to assist in solving problems in science and engineering. Such equations have aided researchers in developing methods used in the study of weather prediction, optical fiber communication systems, water waves, etc... Often, it is the desire of many researchers to further develop numerical methods and make these model equations, their numerical simulations and plots accessible to users through the Internet. In this thesis, I present a web based graphical user numerical simulation interface for nonlinear evolution equations such as the nonlinear Schrödinger (NLS), coupled NLS (CNLS), and the complex modified Korteweg-de Vries (CMKdV) equations. In addition, the numerical implementation of a proposed numerical scheme for the modified CNLS equation is presented. Sequential and parallel algorithms for such equations were implemented on sequential and multiprocessor machines. Index Words: Numerical Simulation, Nonlinear Schrödinger (NLS) equation, Coupled Nonlinear Schrödinger (CNLS) equation, Complex Modified Korteweg-de Vries (CMKdV) equation, Web based graphical user interface. Advisors/Committee Members: Thiab R. Taha.
Foster, Ryan Napoleon. “Web based interface for numerical simulations of nonlinear evolution equations.” 2007. Masters Thesis, University of Georgia. Accessed April 24, 2019. http://purl.galileo.usg.edu/uga_etd/foster_ryan_n_200705_ms.
Foster, Ryan Napoleon. “Web based interface for numerical simulations of nonlinear evolution equations.” 2007. Web. 24 Apr 2019.
Foster RN. Web based interface for numerical simulations of nonlinear evolution equations. [Internet] [Masters thesis]. University of Georgia; 2007. [cited 2019 Apr 24]. Available from: http://purl.galileo.usg.edu/uga_etd/foster_ryan_n_200705_ms.
2. Zhu, Yifei. Numerical Simulation of Vortex-Induced Vibrations of Free Span Pipelines Including Nonlinear Soil Models.
▼ This thesis introduces a fully three dimensional (3D) numerical simulation method of the VIV behaviors of free span pipelines by considering the nonlinear pipe-soil interaction effect. The pipeline is modeled as a tensioned beam of which the governing equations are numerically solved by applying a fully implicit discretization scheme. Reynolds Averaged Navier-Stokes (RANS) equations are numerically solved to compute the fluid domain. An overset grid method is utilized in discretizing the fluid field around the pipeline. Six computational blocks and nearly 1 million grid points are needed in the simulation. It is a good strategy to generate finer grid in the near body regions and relatively coarse grid in the far field. By exchanging motions and forces between the pipeline motion solver and the fluid solver, fluid-structure interaction is achieved. This research also includes a nonlinear soil model to simulate the pipe-soil interaction which is considered as a spring-pipeline system while the stiffness characteristics are expressed by using a nonlinear force-displacement (P-y) curves. The simulation results are compared with model tests or other numerical simulations for validation in two cases: (1) a free span pipeline of G/D=2.0 at different reduced velocities including linear and nonlinear soil models; (2) a free span pipeline of different G/D which ranges from 1.2 to 3.0. Advisors/Committee Members: Chen, Hamn-Ching (advisor), Mercier, Richard (committee member), Comech, Andrew (committee member).
Zhu, Yifei. “Numerical Simulation of Vortex-Induced Vibrations of Free Span Pipelines Including Nonlinear Soil Models.” 2017. Masters Thesis, Texas A&M University. Accessed April 24, 2019. http://hdl.handle.net/1969.1/166006.
Zhu, Yifei. “Numerical Simulation of Vortex-Induced Vibrations of Free Span Pipelines Including Nonlinear Soil Models.” 2017. Web. 24 Apr 2019.
Zhu Y. Numerical Simulation of Vortex-Induced Vibrations of Free Span Pipelines Including Nonlinear Soil Models. [Internet] [Masters thesis]. Texas A&M University; 2017. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/1969.1/166006.
3. Bejatovic, Sintia. Evaluation of Discrete Explicit Filtering for an Approximate Deconvolution Approach to LES.
In the study of computational turbulence, the success of Large Eddy Simulation (LES) is largely determined by the quality of the sub-filter scale (SFS) model and the properties of the filter used to introduce resolved and unresolved length scales. Explicit filters are desirable so that better control over the filter may be achieved, and filter operator errors can be then controlled to a desired order of accuracy. One large advantage to using an explicit filter is that the mathematical definition of the filter may be exploited when considering various SFS models or even different LES techniques. Approximate deconvolution is a technique used in LES, which performs an inverse filtering operation to partly restore the original unfiltered solution. The discrete explicit filtering technique will be used to perform the deconvolution, and numerical results will show how the approximate solution may be used to perform LES.
Advisors/Committee Members: Groth, Clinton P. T., Aerospace Science and Engineering.
Bejatovic, Sintia. “Evaluation of Discrete Explicit Filtering for an Approximate Deconvolution Approach to LES.” 2011. Masters Thesis, University of Toronto. Accessed April 24, 2019. http://hdl.handle.net/1807/27324.
Bejatovic, Sintia. “Evaluation of Discrete Explicit Filtering for an Approximate Deconvolution Approach to LES.” 2011. Web. 24 Apr 2019.
Bejatovic S. Evaluation of Discrete Explicit Filtering for an Approximate Deconvolution Approach to LES. [Internet] [Masters thesis]. University of Toronto; 2011. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/1807/27324.
4. Stiesberg, Gregory. Dynamic Simulation Of Nonlinear Hybrid Rigid-Object Systems With Intermittent Non-Holonomic Constraints: In Search Of Stable Passive Hopping .
▼ A methodology is outlined for derivation of equations of motion and development of arbitrarily accurate numerical simulations of nonlinear hybrid rigid-object systems with intermittent non-holonomic constraints. Some recently discovered high-order explicit Runge-Kutta methods are studied; a 10th order method is validated as particularly effective for integrating initial value problems typically encountered in this work. A hybrid simulation code system is developed and used to simulate simple well known mechanical systems, verifying the validity of the methodology and the accuracy of the code. One novel simulation technique demonstrated is a zero-parameter infinite sliding friction model that makes intermittent contact simulation physically self-consistent without introducing arbitrary parameters. Several simple robotics systems are simulated; a simulation of the simplest walker is compared to published results, further increasing confidence in the simulation system code. The simulation system is used to study an unpowered, uncontrolled, passive hopping device that hops down a flat inclined 5 meter ramp but cannot stand up. The hopping device seems to have a stable limit cycle since it can consistently be launched by hand and then hop un-assisted 100 consecutive times down a ramp. However, numerical simulations insist that the passive hopper actually has an unstable limit cycle, predicting exponential growth of the inevitable perturbations from hand launching will cause it to fall down quickly. An optimization-guided search for stable period-1 motions fails when applied to the set of feasible models corresponding to the physical hopping device. The apparent paradox is resolved by simulating a controller that emulates hand launching technique. The simulations convincingly show the launch technique attracts the state to a neighborhood sufficiently close to the unstable limit cycle such that when it is released, it consistently traverses a flat inclined ramp without falling. By-products of the search for stable period-1 motions are models that are substantially different than the hopping device but do have stable period-1 limit cycles; these are the first known stable and physically realizable 2D passive locomotion models that do not have a statically stable configuration. Advisors/Committee Members: Ruina,Andy Lee (committeeMember), Talman,Richard M (committeeMember).
Stiesberg, Gregory. “Dynamic Simulation Of Nonlinear Hybrid Rigid-Object Systems With Intermittent Non-Holonomic Constraints: In Search Of Stable Passive Hopping .” 2016. Thesis, Cornell University. Accessed April 24, 2019. http://hdl.handle.net/1813/43615.
Stiesberg, Gregory. “Dynamic Simulation Of Nonlinear Hybrid Rigid-Object Systems With Intermittent Non-Holonomic Constraints: In Search Of Stable Passive Hopping .” 2016. Web. 24 Apr 2019.
Stiesberg G. Dynamic Simulation Of Nonlinear Hybrid Rigid-Object Systems With Intermittent Non-Holonomic Constraints: In Search Of Stable Passive Hopping . [Internet] [Thesis]. Cornell University; 2016. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/1813/43615.
5. Li, Zhaoyang. Numerical study of geometrical effects on blast furnace (BF) flow and performance.
▼ Blast furnace (BF) geometry is of significant importance to BF process because it can affect in-furnace multiphase flows, BF stability and efficiency. In the past several decades, the BFs have been frequently enlarged during their relining or rebuilding. However, thus far, the effects of BF geometrical parameters are largely known empirically and the underlying reasons for the enlargement of BF are still not obvious.This thesis presents a numerical study of BF geometrical parameters by means of the BF process model. This model is based on the one recently developed by Dong et al. . The previous model has been improved in terms of the following two aspects: (i), the raw material, operational and geometrical conditions are allowed to vary in a flexible range rather than fixed; and (ii), the variation of the stock line with BF inner state as encountered in practice is considered by controlling burden charge rate according to the global coke balance inside the considered BF.Firstly, the applicability of the improved model has been examined by comparing the predicted BF performances with those practically observed for BFs operated with different coke ratios and blast rates. The model was then used to study the effects of BF geometrical parameters on BF performances and inner states. The calculated results reveal that the enlargement of BF inner volume by mean of expanding any of the BF dimensions improves BF efficiency in terms of the achievable coke ratio. The expansion of BF lateral dimensions lowers the in-furnace pressure drop while the elongation of BF height tends to increase the packed bed resistance to gas flow against the BF operational stability and larger productivity. Certain ratios of the horizontal dimensions are desirable to maintain a well-controlled gas throughflow and smooth descent of burden materials. Therefore, the adjustments of the BF inner liners corresponding to the enlargement of BF inner volume have been proven to be reasonable and necessary.
Li, Zhaoyang. “Numerical study of geometrical effects on blast furnace (BF) flow and performance.” 2012. Masters Thesis, University of New South Wales. Accessed April 24, 2019. http://handle.unsw.edu.au/1959.4/52525 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11198/SOURCE1?view=true.
Li, Zhaoyang. “Numerical study of geometrical effects on blast furnace (BF) flow and performance.” 2012. Web. 24 Apr 2019.
Li Z. Numerical study of geometrical effects on blast furnace (BF) flow and performance. [Internet] [Masters thesis]. University of New South Wales; 2012. [cited 2019 Apr 24]. Available from: http://handle.unsw.edu.au/1959.4/52525 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11198/SOURCE1?view=true.
6. Tan, Winson. Heat-transfer-based Biomedical Devices: Synergistic Numerical Simulations and Experimentation.
▼ A synergistic multi-faceted investigation was performed to demonstrate an approach to the design of thermal-based medical devices. The synergism was achieved by the mutual interaction of numerical simulation and experimentation. Focus was directed to two independent but related biomedical devices. One of these is a non-invasive means of measuring the body core temperature under both steady state and transient circumstances. A realistic application of such a probe is the monitoring of the temperature of a patient undergoing surgery. The investigation of the novel temperature probe involved the interaction of a model of the relevant physical phenomena, which was implemented by numerical simulation. A near-congruent experimental apparatus was designed and fabricated with the view to validate the numerical results. The excellent agreement between these two independent methodologies lends strong support to the validity of the model and the utility of the results obtained. The other thermal-based device is therapeutic in that it is used to supply infusants into the human body under critical conditions. The infusants may be blood, saline, or a mixture of the two. Critical conditions demand high rates of infusion. Furthermore, the temperature of the infusants must be above a critical value to avoid the onset of hypothermia. The goal was to maximize the temperature of the delivered infusant while at the same time avoiding catastrophic events such as hemolysis which is a thermal-based necrosis of the red cells. The mutual supportive outcomes of the simulations and experiments provided strong evidence of the validity of the modeling and its numerical implementation.
Tan, Winson. “Heat-transfer-based Biomedical Devices: Synergistic Numerical Simulations and Experimentation.” 2015. Doctoral Dissertation, University of Minnesota. Accessed April 24, 2019. http://hdl.handle.net/11299/178966.
Tan, Winson. “Heat-transfer-based Biomedical Devices: Synergistic Numerical Simulations and Experimentation.” 2015. Web. 24 Apr 2019.
Tan W. Heat-transfer-based Biomedical Devices: Synergistic Numerical Simulations and Experimentation. [Internet] [Doctoral dissertation]. University of Minnesota; 2015. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/11299/178966.
7. Dougherty, Edward T. Computation and Numerics in Neurostimulation.
▼ Neurostimulation continues to demonstrate tremendous success as an intervention for neurodegenerative diseases, including Parkinson's disease, in addition to a range of other neurological and psychiatric disorders. In an effort to enhance the medical efficacy and comprehension of this form of brain therapy, modeling and computational simulation are regarded as valuable tools that enable in silico experiments for a range of neurostimulation research endeavours. To fully realize the capacities of neurostimulation simulations, several areas within computation and numerics need to be considered and addressed. Specifically, simulations of neurostimulation that incorporate (i) computational efficiency, (ii) application versatility, and (iii) characterizations of cellular-level electrophysiology would be highly propitious in supporting advancements in this medical treatment. The focus of this dissertation is on these specific areas. First, preconditioners and iterative methods for solving the linear system of equations resulting from finite element discretizations of partial differential equation based transcranial electrical stimulation models are compared. Second, a software framework designed to efficiently support the range of clinical, biomedical, and numerical simulations utilized within the neurostimulation community is presented. Third, a multiscale model that couples transcranial direct current stimulation administrations to neuronal transmembrane voltage depolarization is presented. Fourth, numerical solvers for solving ordinary differential equation based ligand-gated neurotransmitter receptor models are analyzed. A fundamental objective of this research has been to accurately emulate the unique medical characteristics of neurostimulation treatments, with minimal simplification, thereby providing optimal utility to the scientific research and medical communities. To accomplish this, numerical simulations incorporate high-resolution, MRI-derived three-dimensional head models, real-world electrode configurations and stimulation parameters, physiologically-based inhomogeneous and anisotropic tissue conductivities, and mathematical models accepted by the brain modeling community. It is my hope that this work facilitates advancements in neurostimulation simulation capabilities, and ultimately helps improve the understanding and treatment of brain disease. Advisors/Committee Members: Turner, James C. (committeechair), O'Hara, Kathleen Marie (committee member), Senger, Ryan S. (committee member), Bevan, David R. (committee member).
Dougherty, Edward T. “Computation and Numerics in Neurostimulation.” 2015. Doctoral Dissertation, Virginia Tech. Accessed April 24, 2019. http://hdl.handle.net/10919/73350.
Dougherty, Edward T. “Computation and Numerics in Neurostimulation.” 2015. Web. 24 Apr 2019.
Dougherty ET. Computation and Numerics in Neurostimulation. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/10919/73350.
8. Graham, Jason Scott. Turbulence simulations: multiscale modeling and data-intensive computing methodologies.
▼ In this two part work, methodologies for the multiscale modeling of complex turbulent flows and data-intensive computing strategies for large-scale turbulent simulations are developed and presented. The first part of this thesis is devoted to the simulation of turbulent flows over objects characterized by hierarchies of length-scale. Flows of this type present special challenges associated with the cost of resolving small-scale geometric elements. During large eddy simulation (LES), their effects on the resolved scales must be captured realistically through subgrid-scale models. Prior work performed by Chester et al., J. Comput. Phys. 2007 proposed a technique called renormalized numerical simulation (RNS), which is applicable to objects that display scale-invariant geometric (fractal) properties. The idea of RNS is similar to that of the dynamic model used in LES to determine model parameters for the subgrid-stress tensor model in the bulk of the flow. In RNS, drag forces from the resolved elements that are obtained during the simulation are re-scaled appropriately by determining drag coefficients that are then applied to specify the drag forces associated with the subgrid-scale elements. In the current work we introduce a generalized framework for describing and implementing the RNS methodology thereby extending the methodology first presented by Chester et al., 2007. Furthermore, we present various other possible practical implementations of RNS that differ on important, technical aspects related to 1) time averaging, 2) spatial localization, and 3) numerical representation of the drag forces. The new RNS framework is then applied to fractal tree canopies consisting of fractal-like trees with both planar cross-section and three dimensional orientations. The results indicate that the propsed time averaged, local, and explicit formulation of RNS is superior to the predecessor formulation as it enables the modeling of spatially non-homogenous geometries without using a low-level branch based description and preserves the assumed dynamic similary through temporal filtering. In addition, the overall predicted drag force of the non-planar fractal trees is shown to agree well with experimental data. In addition to RNS, a methodology for generating accurate inflow conditions in multiscale turbulence simulations is present. This technique called concurrent precursor simulation (CPS) allows the synchronous generation of inflow data from an upstream precursor simulation. This approach conceptually is the same as the standard precursor simulations (Lund et al., J. Comput. Phys. 1998 and Ferrante et al., J. Comput. Phys. 2004) used in the past, however, it eliminates the I/O bottleneck of disk reads and writes by transferring sampled data directly between domains using MPI. Furthermore, issues with recycling time scales of the sample inflow library are removed since the upstream, precursor simulation is performed concurrently with the target simulation. This methodology is applied to a single fractal tree (modeled using RNS)… Advisors/Committee Members: Meneveau, Charles (advisor).
Graham, Jason Scott. “Turbulence simulations: multiscale modeling and data-intensive computing methodologies.” 2014. Thesis, Johns Hopkins University. Accessed April 24, 2019. http://jhir.library.jhu.edu/handle/1774.2/37045.
Graham, Jason Scott. “Turbulence simulations: multiscale modeling and data-intensive computing methodologies.” 2014. Web. 24 Apr 2019.
Graham JS. Turbulence simulations: multiscale modeling and data-intensive computing methodologies. [Internet] [Thesis]. Johns Hopkins University; 2014. [cited 2019 Apr 24]. Available from: http://jhir.library.jhu.edu/handle/1774.2/37045.
9. Li, Zhan. Studying the genesis of typhoon Nuri (2008) with numerical simulations and data assimilation.
▼ Forecasting tropical cyclone (TC) genesis is a challenging problem. Thisdissertation attempts to understand the following questions through studying the genesisof Typhoon Nuri (2008) with numerical simulations and data assimilation: 1) What arethe atmospheric conditions and processes that contribute to Nuri’s genesis and early rapidintensification? 2) To what extent can data assimilation improve the forecasts of Nuri’sgenesis?To address the first question, numerical simulations of Nuri’s genesis areconducted using an advanced research version of the Weather Research and Forecasting(WRF) model. First, initial and boundary conditions derived from two global analyses arefound to lead to remarkably different simulations of Nuri’s genesis in developing andnondeveloping cases. It is also found that the convective development into the pre-Nuricore region is a critical process for Nuri’s genesis. A strong midlevel vortex and a moistenvironment provide the favorable conditions for the convective development. Inducedby the persistent deep convection, diabatic heating at upper levels is produced from latentheat release. This substantial warming at upper levels results in the drop in Nuri’sminimum central sea level pressure.Next, the sensitivity of numerical simulations of Nuri’s genesis to the modelhorizontal resolution is examined. Results show that the simulation at a coarse-resolution(e.g., 12 km) better predicts Nuri’s rapid intensification than that at a higher resolution(e.g., 4 km). Specifically, the simulation at the coarser resolution produces strongconvective bursts and diabatic heating in the inner core region and also stronger warmingin the upper atmosphere, thus leading to a lower minimum sea level pressure (MSLP).Further experiments suggest that an appropriate microphysics scheme (e.g., the twomomentMorrison scheme) and a later initialization time (after Nuri’s early development)could help the high-resolution simulation better capture Nuri’s rapid intensification.Finally, numerical experiments are conducted to examine the impact of radar dataassimilation on numerical simulations of Nuri’s genesis using a four-dimensionalvariational data assimilation (4D-VAR) method. The radar data assimilation results insignificant improvements in the numerical simulation of Nuri’s genesis. Severalconfigurations of data assimilation are evaluated. Specifically, assimilation of radialvelocity leads to more improvement in intensity forecasts, whereas track forecasts arebetter simulated by the assimilation of radar-retrieved wind components. Improvedanalysis and forecasts are obtained when both radial velocity and retrieved winds areassimilated. In addition, 4D-VAR performs better than three-dimensional variational dataassimilation (3D-VAR) in radar data assimilation. The positive impact of radar dataassimilation can be attributed to the improved simulations of convective evolution andthe enhanced midlevel vortex and moisture conditions.
Li, Zhan. “Studying the genesis of typhoon Nuri (2008) with numerical simulations and data assimilation.” 2013. Doctoral Dissertation, University of Utah. Accessed April 24, 2019. http://content.lib.utah.edu/cdm/singleitem/collection/etd3/id/3482/rec/2297.
Li, Zhan. “Studying the genesis of typhoon Nuri (2008) with numerical simulations and data assimilation.” 2013. Web. 24 Apr 2019.
Li Z. Studying the genesis of typhoon Nuri (2008) with numerical simulations and data assimilation. [Internet] [Doctoral dissertation]. University of Utah; 2013. [cited 2019 Apr 24]. Available from: http://content.lib.utah.edu/cdm/singleitem/collection/etd3/id/3482/rec/2297.
10. Wilkes, Jason. Numerical simulation of Ricci flow on a class of manifolds with non-essential minimal surfaces.
▼ In the last three decades, the Ricci flow has proved to be an extremely useful tool in mathematics and physics. We explore numerically the long time existence of the Ricci-DeTurck flow and the List flow for a one-parameter family of Riemannian manifolds with non-essential minimal surfaces. This class of metrics is constructed to be an intermediate case between the corseted spheres examined by Garfinkle and Isenberg, and the RP3 geon explored by Balehowsky and Woolgar. We find that the Ricci-DeTurck flow of these manifolds depends on the value of a geometric parameter, with immortal flow below a critical parameter value, and singularity formation above it. We also examine the List flow of this family of manifolds with and without a stable minimal surface, we compare the long time existence properties to those observed in the case of the Ricci flow, and we use these results to gain insights into both the results obtained by Gulcev, Oliynyk, and Woolgar, and the general phenomena of singularity formation and critical behavior in Ricci flow.
Wilkes, Jason. “Numerical simulation of Ricci flow on a class of manifolds with non-essential minimal surfaces.” 2011. Masters Thesis, University of Alberta. Accessed April 24, 2019. https://era.library.ualberta.ca/files/12579t30w.
Wilkes, Jason. “Numerical simulation of Ricci flow on a class of manifolds with non-essential minimal surfaces.” 2011. Web. 24 Apr 2019.
Wilkes J. Numerical simulation of Ricci flow on a class of manifolds with non-essential minimal surfaces. [Internet] [Masters thesis]. University of Alberta; 2011. [cited 2019 Apr 24]. Available from: https://era.library.ualberta.ca/files/12579t30w.
11. Fick, Lambert Hendrik. Direct Numerical Simulation of Incompressible Flows in Domains of Close Packed Spheres.
▼ This study aimed to investigate and quantify turbulent flow effects for incompressible, isothermal fluid flows in computational domains consisting of regularly packed spheres using high-fidelity computational fluid dynamics. The flow domains treated in this study are analogous in an idealized sense to those encountered in pebble bed based high temperature nuclear reactors. The quantification of turbulent flow effects serves two purposes. Firstly, it assists in the development of lower-fidelity engineering tools such as Reynolds averaged Navier-Stokes based methodologies. Secondly, the quantification of turbulent flow effects adds to our fundamental understanding of the physics of incompressible flows in complex geometries. The study was conducted using an open-source spectral element computational fluid dynamics code, Nek5000, which was used to perform a series of direct numerical simulations in several flow domains representing both theoretical geometries and idealized sections of a practical reactor core at low to moderate Reynolds numbers. Selected results include the development of a high-fidelity database of numerical data for an expanded unit-cell geometry, the identification of possible very low frequency temporal dynamics in domains featuring several close packed spheres, and the calculation of turbulence statistics in a domain approximating the near-wall region of a reactor core. Advisors/Committee Members: Hassan, Y A (advisor), Anand, Nagamangala K (committee member), King, Maria D (committee member), Marlow, William H (committee member), Merzari, Elia (committee member).
Fick, Lambert Hendrik. “Direct Numerical Simulation of Incompressible Flows in Domains of Close Packed Spheres.” 2017. Thesis, Texas A&M University. Accessed April 24, 2019. http://hdl.handle.net/1969.1/161650.
Fick, Lambert Hendrik. “Direct Numerical Simulation of Incompressible Flows in Domains of Close Packed Spheres.” 2017. Web. 24 Apr 2019.
Fick LH. Direct Numerical Simulation of Incompressible Flows in Domains of Close Packed Spheres. [Internet] [Thesis]. Texas A&M University; 2017. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/1969.1/161650.
12. Jiang, Han. Experimental and Numerical Study of Polymer Scratch Behavior.
▼ As part of a larger effort to understand the fundamental knowledge of polymer scratch behavior, this dissertation is focused on both experimental study and numerical analysis of scratch deformation of a broad range of polymers, with an emphasis on the mechanical understanding of how the scratch-induced damage is formed. An instrumented progressive load scratch method recommended by ASTM/ISO standards was adopted for the experimental work. The commercial finite element (FE) method package ABAQUS was employed as a numerical simulation tool to describe the stress-strain fields, and it analyzes the deformation mechanisms during the scratch process. A thorough parametric study has been performed to assess the influence of material parameters and surface properties, such as Young's modulus, yield strength, and friction coefficient, on the polymer scratch behavior. Upon investigation of the scratch behaviors of a broad range of polymer materials, various kinds of scratch damage features are identified and correlated with the mechanical characteristics of the polymers. A generalized scratch damage mechanism map for polymers is presented. Correlation between different material types and scratch damage mechanisms is made. It is found that both the material characteristics and the stress state exerted on the scratched surface are responsible for the observed scratch damage mechanisms. The phenomenological deduction of the scratch damage process based on the stick-slip mechanism is established. A more realistic material law for the scratch analysis is also provided. To evaluate the polymer resistance against scratch visibility quantitatively, an entirely new automated on-set scratch visibility determination methodology is developed based on typical visual characteristics of human eyes. Its application on the evaluation of mar and abrasion of polymer is also explored. This new methodology can quantify polymer scratch resistance consistently and reliably regardless of the sample surface characteristics and color. Advisors/Committee Members: Sue, Hung-Jue (advisor), Whitcomb, John D. (committee member), Schwartz, Cris (committee member), Suh, Steve (committee member).
Jiang, Han. “Experimental and Numerical Study of Polymer Scratch Behavior.” 2010. Thesis, Texas A&M University. Accessed April 24, 2019. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-844.
Jiang, Han. “Experimental and Numerical Study of Polymer Scratch Behavior.” 2010. Web. 24 Apr 2019.
Jiang H. Experimental and Numerical Study of Polymer Scratch Behavior. [Internet] [Thesis]. Texas A&M University; 2010. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-844.
13. GHIMIRE, BIDUR. HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS : 高浸透能多孔質媒体中への開水路流れの水理解析法とその応用に関する研究.
GHIMIRE, BIDUR. “HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS : 高浸透能多孔質媒体中への開水路流れの水理解析法とその応用に関する研究.” 2009. Thesis, Kyoto University / 京都大学. Accessed April 24, 2019. http://hdl.handle.net/2433/85382 ; http://dx.doi.org/10.14989/doctor.k14916.
GHIMIRE, BIDUR. “HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS : 高浸透能多孔質媒体中への開水路流れの水理解析法とその応用に関する研究.” 2009. Web. 24 Apr 2019.
GHIMIRE B. HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS : 高浸透能多孔質媒体中への開水路流れの水理解析法とその応用に関する研究. [Internet] [Thesis]. Kyoto University / 京都大学; 2009. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/2433/85382 ; http://dx.doi.org/10.14989/doctor.k14916.
14. Srivastava, Kishor Kumar. Numerical Simulation of Strong Discontinuities in Conducting Plasma;.
Advisors/Committee Members: Singh, V K.
Srivastava, Kishor Kumar. “Numerical Simulation of Strong Discontinuities in Conducting Plasma;.” 1992. Thesis, Bundelkhand University. Accessed April 24, 2019. http://shodhganga.inflibnet.ac.in/handle/10603/12039.
Srivastava, Kishor Kumar. “Numerical Simulation of Strong Discontinuities in Conducting Plasma;.” 1992. Web. 24 Apr 2019.
Srivastava KK. Numerical Simulation of Strong Discontinuities in Conducting Plasma;. [Internet] [Thesis]. Bundelkhand University; 1992. [cited 2019 Apr 24]. Available from: http://shodhganga.inflibnet.ac.in/handle/10603/12039.
15. Lai, Ang-chih. Numerical model of carbon dissolution in liquid iron.
▼ In this study, a numerical model is built to investigate the factors on carbon dissolution rate and develop a lump system for carbon particle dissolution in hot liquid metal. We assume the carbon particles dissolve in the molten iron is a quasi-steady process. Therefore, the steady state model has been developed. The simulation data shows the distribution of mass dissolution rate at the particle surface is significantly affected by the flow circulation behind a particle as a relative flow velocity is applied. The lump system has been developed by the correlation of Reynolds number and Schmidt number, which can predict the carbon particles dissolve at times of different state. The correlation of mass/heat transfer are as following: Sh=2.81+0.52 Re0.52 Sc0.38 Nu=0.53+0.27 ãReã034 Pr0.16 The study also established a transient model, and compare the time of dissolution between two models. Simulation results of transient model show that when the Reynolds number is smaller, the dissolution rate of carbon particles goes to be slightly longer.in addition this study also building a two dimension injection model through the simulation result of different model confirm the reliability of lump system Advisors/Committee Members: Sheng-Yen Hsu (committee member), Tsou, Ying (chair), Chien-Hsiung Tsai (chair).
Lai, Ang-chih. “Numerical model of carbon dissolution in liquid iron.” 2014. Thesis, NSYSU. Accessed April 24, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0805114-100459.
Lai, Ang-chih. “Numerical model of carbon dissolution in liquid iron.” 2014. Web. 24 Apr 2019.
Lai A. Numerical model of carbon dissolution in liquid iron. [Internet] [Thesis]. NSYSU; 2014. [cited 2019 Apr 24]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0805114-100459.
16. Shue, Nai-Shen. Numerical simulation of Large Solar Hot Water system in storage tank.
▼ This research is aimed to study the storage tank design parameters effects on the efficiency of the large solar hot water system. Detailed CFD simulation for the storage tank coupled with TRNSYS program simulation for the entire solar hot water system will be performed to study the system performance under various thermal stratification baffles design for the storage tank. The study is made for three representative cities of Taiwan by input their typical-meteorological-year data (TMY data). The results indicate the performance of a large solar hot water system can be significantly improved with proper designed thermal stratification baffles in the storage tank. Advisors/Committee Members: Huang, Jen-Chih (chair), Yang, Ru (committee member), Chen, Long-Jeng (chair).
Shue, Nai-Shen. “Numerical simulation of Large Solar Hot Water system in storage tank.” 2012. Thesis, NSYSU. Accessed April 24, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0906112-171826.
Shue, Nai-Shen. “Numerical simulation of Large Solar Hot Water system in storage tank.” 2012. Web. 24 Apr 2019.
Shue N. Numerical simulation of Large Solar Hot Water system in storage tank. [Internet] [Thesis]. NSYSU; 2012. [cited 2019 Apr 24]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0906112-171826.
17. Zeinijahromi, Mohamad. Development Of A Three-dimensional, Three-phase Coupled Model For Simulating Hydraulic Fracture Propagation And Long-term Recovery In Tight Gas Reservoirs.
▼ In the past decades, development of tight gas reservoirs has become more important. These low permeability reservoirs need to be stimulated effectively with hydraulic fracturing to produce economically. Stimulation design has improved with better understanding these unconventional reservoirs, advances in modeling and study of flow mechanisms. Conventional fracture propagation models predict fracture geometry based on fracture fluid mechanics, rock mechanics, petrophysics and empirical/analytical leak-off models. Reservoir flow simulators are then used to evaluate post-fracture well performances. These approaches are called de-coupled modeling. It is a challenge to couple these two processes, particularly when dealing with large amounts of input data. Furthermore decoupled modeling is a time-intensive job that requires a coordinated effort from stimulation and reservoir engineers. This approach may not work in low-permeability reservoirs because the hydraulic fracture propagation is complex, fracture fluid leak-off is pressure/reservoir/fracture dependent and there are changes in in-situ stress and permeability during and after a fracture treatment. It has been recognized that fluid loss can be computed directly by solving the multiphase flow equations in porous media. Such an approach is more general and does not have many of the assumptions in decoupled models. Models based on this approach are called coupled models. Hydraulic fracturing is an integrated process of injection of fracture fluid, fracture propagation, proppant transport, clean-up and multi-phase flow through the reservoir. Available coupled models are not fully integrated as they were developed to simulate just one or two of these steps. The main objective of this research is to develop an integrated coupled model which is capable of fully simulating reservoir flow, fracture propagation, proppant distribution, flowback, long term gas recovery and resulted stress change through a stationary reservoir/stress grid system. The model uses a three-dimensional, three-phase finite difference reservoir flow simulator coupled with a finite difference geomechanics model where both are applied on the same grid system. The model has been validated with published data in the literature. Using the developed model, parametric studies have been carried out to quantify important factors affecting fracture and recovery processes such as injection rate, treatment volume, proppant type, flowback rate and flowing bottom hole pressure (FBHP). The model enables us to simulate and compare different scenarios and suggest the optimized hydraulic fracturing design. The new findings lead to better understandings of hydraulic fracturing and well performances in tight gas reservoirs.
Zeinijahromi, Mohamad. “Development Of A Three-dimensional, Three-phase Coupled Model For Simulating Hydraulic Fracture Propagation And Long-term Recovery In Tight Gas Reservoirs.” 2013. Doctoral Dissertation, Penn State University. Accessed April 24, 2019. https://etda.libraries.psu.edu/catalog/19717.
Zeinijahromi, Mohamad. “Development Of A Three-dimensional, Three-phase Coupled Model For Simulating Hydraulic Fracture Propagation And Long-term Recovery In Tight Gas Reservoirs.” 2013. Web. 24 Apr 2019.
Zeinijahromi M. Development Of A Three-dimensional, Three-phase Coupled Model For Simulating Hydraulic Fracture Propagation And Long-term Recovery In Tight Gas Reservoirs. [Internet] [Doctoral dissertation]. Penn State University; 2013. [cited 2019 Apr 24]. Available from: https://etda.libraries.psu.edu/catalog/19717.
18. Nekouie Esfahani, Mohammadreza. Laser welding of dissimilar carbon steel to stainless steel 316L.
▼ Laser welding of metals and alloys is extensively used in industry due to its advantages of controlled heating, narrow weld bead, low heat affected zone (HAZ) and its ability to weld a wide range of metals and dissimilar metals. Laser welding of dissimilar metals such as carbon steels and stainless steel is still a challenging task, particularly due to the formation of brittle phases in the weld, martensitic formation in the HAZ and solidification cracking in the fusion zone. These issues can significantly deteriorate the strength of the welded joint. The aim of this work is to investigate the fundamental phenomena that occur inside the dissimilar weld zone and their effect on weld quality. In order to establish the key process variables, an initial study concentrated on the effect of different laser process parameters on dissimilar weld quality. In the second part of the work, a comprehensive study was performed to understand and subsequently control the alloying composition in laser dissimilar welding of austenitic stainless steel and low carbon steel. A dissimilar weld that is predominantly austenitic and homogeneous was obtained by controlling the melt pool dynamics through specific point energy and beam alignment. The significance of dilution and alloying elements on joint strength was established. A coupled CFD and FEM numerical model was developed to assist in understanding the melt pool dynamics and transportation processes of alloying elements. The model has been validated by a series of laser welding experiments using various levels of specific point energy. The laser welding characteristics in terms of geometric dimensions, surface morphology, alloying concentration, and dilution, were compared, and it is concluded that the specific point energy and laser beam position are the key parameters that can be controlled to obtain a weld bead with characteristics most suitable for industrial applications. In the third part of the work, a comparative study was performed to understand the significance of cooling rate, and alloying composition on the microstructure and phase structure of the dissimilar weld zone. Results show that the HAZ within the high carbon steel has significantly higher hardness than the weld area, which severely undermines the weld quality. A new heat treatment strategy was proposed based on the results of the numerical simulation, and it is shown to control the brittle phase formation in HAZ of high carbon steel. A series of experiments was performed to verify the developed thermo-metallurgical FEA model and a good qualitative agreement of the predicted martensitic phase distribution is shown to exist. Although this work is presented in the context of dissimilar laser welding of mild steel to stainless steel, the concept is applicable to any dissimilar fusion welding process.
Nekouie Esfahani, Mohammadreza. “Laser welding of dissimilar carbon steel to stainless steel 316L.” 2015. Doctoral Dissertation, Loughborough University. Accessed April 24, 2019. https://dspace.lboro.ac.uk/2134/19760 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677709.
Nekouie Esfahani, Mohammadreza. “Laser welding of dissimilar carbon steel to stainless steel 316L.” 2015. Web. 24 Apr 2019.
Nekouie Esfahani M. Laser welding of dissimilar carbon steel to stainless steel 316L. [Internet] [Doctoral dissertation]. Loughborough University; 2015. [cited 2019 Apr 24]. Available from: https://dspace.lboro.ac.uk/2134/19760 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677709.
19. Scherr, Thomas Foster. Numerical Investigation of Cryopreserved Zebrafish Sperm Cell Activation in Microchannels.
▼ This aim of this research project is to probe the activation process of zebrafish spermatozoa. Zebrafish are a model species for biological engineering applications, and the cryopreservation of their reproductive cells allows for inexpensive cataloging and maintenance of valuable biological material. Evaluation of cryopreservation protocols for aquatic sperm cells is typically accomplished by motility analysis after subjecting cells to a cryopreservation treatment. In zebrafish sperm cells, motility is initiated when cells come into contact with a hypo-osmotic environment. Subsequent activation analysis is currently done manually and brings with it an inherent difficulty and error. This process is slow and not ideal for high-throughput sample processing and analysis. As such, there is a critical need for an influx of enabling technologies to improve the throughput and optimization of these procedures. Microfluidics offers an intriguing solution to this problem. These devices, the size of a single 1-inch by 3-inch glass slide, offer automated, high-throughput, highly reproducible results. Additionally they utilize small sample volumes, which is important in minimizing valuable sample loss. Cells can be input into a micromixer which can rapidly dilute the extracellular environment, and then sent to an analysis chamber that acn determine the efficacy of a cryopreservation treatment. Despite its popularity in other fields, computational modeling of sperm cell activation has been nearly non-existent in literature. In this work, we model both the macroscopic aspects of particulate flow in a microchannel, and the microscopic mass transport across the cellular membrane. By tracking cells as they move throughout a simulated microdevice, we can find a history for each particle and predict cell outcomes. We are the first to introduce this combinatory model to the problem of cryoprotectant loading, where numerical modeling has well-established presence, and to the problem of zebrafish sperm cell activation. I envision the combination of microfluidics, with their controllable and reproducible flow patterns, and computational methods capturing both macro- and micro-transport, as two examples of the very enabling technologies that cryopreservation needs. While we apply these methods primarily to sperm cell analysis, the framework can be widely applied to a variety of cells and tissues.
Scherr, Thomas Foster. “Numerical Investigation of Cryopreserved Zebrafish Sperm Cell Activation in Microchannels.” 2014. Doctoral Dissertation, Louisiana State University. Accessed April 24, 2019. etd-04042014-211939 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1782.
Scherr, Thomas Foster. “Numerical Investigation of Cryopreserved Zebrafish Sperm Cell Activation in Microchannels.” 2014. Web. 24 Apr 2019.
Scherr TF. Numerical Investigation of Cryopreserved Zebrafish Sperm Cell Activation in Microchannels. [Internet] [Doctoral dissertation]. Louisiana State University; 2014. [cited 2019 Apr 24]. Available from: etd-04042014-211939 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1782.
20. Popov, Pavel. Advances In Particle/Finite Volume Algorithms For Turbulent Reactive Flows .
▼ In the field of turbulent reactive flow simulations, hybrid particle/finite volume large eddy simulation/probability density function (LES/PDF) methods have been shown to be highly accurate in simulating laboratory-scale flames. Their strengths lie in the combination of the large eddy simulation procedure's ability to resolve the large, non-universal scales of turbulence, combined with the fact that probability density function models for turbulent combustion require no closure for the highly non-linear chemistry source term. This work presents advances in such hybrid particle/finite volume LES/PDF algorithms for turbulent reactive flows. New time stepping, interpolation, and coupling schemes have been proposed with the goal of reducing particle mass consistency (PMC) error (defined as the discrepancy between particle mass density and resolved finite volume density) and overall simulation error. The Multi-step Second-order Runge-Kutta (MRK2) integration scheme is an ODE integration scheme designed for reducing PMC errors when applied to discontinuous velocity fields. When applied to a discontinuous velocity field such as might be produced by a state-of-the art velocity interpolation scheme, MRK2 preserves the continuity of the Lagrangian position mapping and is second-order convergent in time, as opposed to a standard second-order Runge-Kutta scheme, which is only first-order convergent in time when applied to a discontinuous velocity field. The Direct Richardson p-th order (DRp) is a conceptually new family of SDE integration schemes which are weakly p-th order accurate in time, where p is an arbitrary positive integer. Unlike standard SDE integration schemes, which are based on matching appropriate terms in the Ito-Taylor expansion of the stochastic process, the DRp schemes work via Richardson extrapolation between the probability density functions of a set of first-order accurate Euler approximations with differing time steps. In the context of the Large Eddy Simulation/Probability Density Function (LES/PDF) code developed by the Turbulence and Combustion Group at Cornell University, a PDF to LES density coupling scheme via a transported specific volume (TSV) has been developed. While coupling approaches similar to TSV have been used previously in LES/PDF application, the present implementation is the first to allow overall second-order accuracy of the LES/PDF code in space and time. New implicit and explicit schemes for PMC error reduction schemes have been developed and tested in the context of the Sandia-Sydney bluff-body flame. Implicit PMC preservation schemes include new velocity and diffusivity interpolation algorithms, and explicit PMC error correction is achieved via a corrective velocity. While corrective velocity schemes have been used previously, the present algorithm, featuring a smoothed version of the PMC error field, is capable of maintaining the same PMC error levels with a corrective velocity of lower magnitude. Finally, the LES/PDF algorithm, developed by the Turbulence and Combustion group at… Advisors/Committee Members: Vladimirsky, Alexander B. (committeeMember), Caughey, David Alan (committeeMember).
Popov, Pavel. “Advances In Particle/Finite Volume Algorithms For Turbulent Reactive Flows .” 2013. Thesis, Cornell University. Accessed April 24, 2019. http://hdl.handle.net/1813/33920.
Popov, Pavel. “Advances In Particle/Finite Volume Algorithms For Turbulent Reactive Flows .” 2013. Web. 24 Apr 2019.
Popov P. Advances In Particle/Finite Volume Algorithms For Turbulent Reactive Flows . [Internet] [Thesis]. Cornell University; 2013. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/1813/33920.
21. Korneeva, Daria Y. Numerical simulation of compressible gas flow coupled to heat conduction in two space dimensions.
Korneeva, Daria Y. “Numerical simulation of compressible gas flow coupled to heat conduction in two space dimensions.” 2011. Thesis, University of Saskatchewan. Accessed April 24, 2019. http://hdl.handle.net/10388/etd-05312011-143902.
Korneeva, Daria Y. “Numerical simulation of compressible gas flow coupled to heat conduction in two space dimensions.” 2011. Web. 24 Apr 2019.
Korneeva DY. Numerical simulation of compressible gas flow coupled to heat conduction in two space dimensions. [Internet] [Thesis]. University of Saskatchewan; 2011. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/10388/etd-05312011-143902.
22. Fang, Ruonan. Assessment of a Microslip Model for the Numerical Simulation of Underplatform Damper Dynamics.
▼ This thesis work was developed in the Department of Mechanical and Aerospace Engineering (DIMEAS) at Politecnico of Turin. It focuses on under-platform damper kinematics and its damping capabilities estimation by means of a dedicated, improved numerical model which includes the e ffects of a phenomenon called micro-slip.Taking over the advantage of AERMEC laboratory's test rigs set to investigate the relationship between the blade platform displacements and the contact forces, it was possible to assess the developed model against the observed experimental data. After an overview of the existing experimental-numerical method developed by the AERMEC group during the previous years, with particular relevance to the weaker cases in which the experimental has a minor match to the simulation, index of a possible neglected micro-slip e ffect in the contact model. Therefore the improved contact model will be established and later applied on a series of cases on two types of contact geometries. The results of simulations will be compared and analysed closely in order to have a better understanding of the working ranges in which the phenomenon of micro-slip has a wider impact on the overall energy dissipation. Advisors/Committee Members: Royston, Thomas (advisor).
Fang, Ruonan. “Assessment of a Microslip Model for the Numerical Simulation of Underplatform Damper Dynamics.” 2014. Thesis, University of Illinois – Chicago. Accessed April 24, 2019. http://hdl.handle.net/10027/19040.
Fang, Ruonan. “Assessment of a Microslip Model for the Numerical Simulation of Underplatform Damper Dynamics.” 2014. Web. 24 Apr 2019.
Fang R. Assessment of a Microslip Model for the Numerical Simulation of Underplatform Damper Dynamics. [Internet] [Thesis]. University of Illinois – Chicago; 2014. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/10027/19040.
23. Li, Sujuan. Numerical instability study of supercritical water flowing upward in two heated parallel channels.
▼ A three dimensional numerical investigation of supercritical water flowing upward in two heated parallel channels was developed using a RANS model in the Computational Fluid Dynamics (CFD) code ANSYS CFX. The standard k- turbulence model with scalable wall functions was adopted throughout this numerical study. The effects of spatial and temporal grid sizes on flow instability were studied first. Then oscillatory instabilities of nine experimental cases were predicted using the CFX code. For comparison purposes, Chatoorgoon’s 1-D non-linear SPORTS code was also used to determine the instability boundary. These new numerical results were compared with the experimental data and previous numerical results by other investigators. Additionally, the effects of changing the outlet plenum volume, the turbulent Prandtl number, the turbulence inlet conditions, the outlet K factor, the maximum iterations per time step in the transient analysis and the order of the transient scheme on the instability thresholds were examined. Advisors/Committee Members: Chatoorgoon, Vijay (Mechanical Engineering), Birouk, Madjid (Mechanical Engineering).
Li, Sujuan. “Numerical instability study of supercritical water flowing upward in two heated parallel channels.” 2016. Masters Thesis, University of Manitoba. Accessed April 24, 2019. http://hdl.handle.net/1993/31974.
Li, Sujuan. “Numerical instability study of supercritical water flowing upward in two heated parallel channels.” 2016. Web. 24 Apr 2019.
Li S. Numerical instability study of supercritical water flowing upward in two heated parallel channels. [Internet] [Masters thesis]. University of Manitoba; 2016. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/1993/31974.
24. Chernyavskiy, Alexandr. A mathematical model of the soliton laser with external cavity.
▼ This thesis is devoted to mathematical modelling, including numerical simulation, in nonlinear laser physics. We study the concrete problem of finding optimal parameters for soliton lasers which is important for many applications. The basic mathematical tool used in our studies is the theory of nonlinear differential equations and numerical methods of their investigations.
Chernyavskiy, Alexandr. “A mathematical model of the soliton laser with external cavity.” 2015. Thesis, Linnaeus University. Accessed April 24, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-43898.
Chernyavskiy, Alexandr. “A mathematical model of the soliton laser with external cavity.” 2015. Web. 24 Apr 2019.
Chernyavskiy A. A mathematical model of the soliton laser with external cavity. [Internet] [Thesis]. Linnaeus University; 2015. [cited 2019 Apr 24]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-43898.
25. Timmer, M.A. The resonance frequency of tip-vortex cavitation:.
▼ Over time much research has been performed on the subject of cavitation. A recent development in this field is the investigation into the behaviour of the cavity within a propeller's tip-vortex. It is found that this cavity can produce a very distinct broadband sound-spectrum which can cause trouble on-board ships either by the sound itself or due to the coincidence with the natural frequencies of a ships structure, causing resonance problems. Recent research by Bosschers and Pennings have resulted in an engineering approach to the calculation of a center frequency of this specific type of cavitation sound. To validate this engineering method, measurements were performed by Pennings on a 2-bladed propeller in the cavitation tunnel at the Delft University of Technology. The purpose of these measurements was finding the resonance frequency of the tip-vortex cavity. From early measurements it was found that the self-exciting behaviour of the cavity, as it was found by Maines & Arndt, could not be reproduced. To get the cavity to generate sound, an artificial wake was introduced which resulted in the distinct broadband sound-spectrum associated with tip-vortex cavitation. To investigate whether the velocity gradient introduced by the wake is sufficiently steep to excite the natural frequencies of the vortex cavity, velocity measurements have been performed from which a steep dip in the flow velocity was found near and behind the wake generator. Also a highly fluctuating behaviour of the flow, with large deviations from the mean flow, was found. These large spreads are associated with the broadband sound spectrum that comes with tip-vortex cavitation. From this it is concluded that the wake generator, as it is used in the measurements by Pennings, gives a good approximation of a real wake. To be able to use the engineering method as a tool to predict the center frequency, a method is needed to accurately calculate the cavity radius and the associated circumferential velocity without the need of full scale tests. When such a method is available the resonance frequency associated with tip-vortex cavitation for a specific propeller can be calculated in the design stage of the ship and/or propeller. With this information available an educated trade-off can be made between the alteration of the propeller and the construction of the ship in order to prevent coinciding natural frequencies. To obtain the necessary cavitation information a numerical simulation is performed of which the results show good agreement with measurement data. With this simulation method a relatively fast and accurate prediction can be made of the center frequency of tip-vortex cavitation with the use of the engineering method. However, to grow the confidence in the results produced, further research should be performed. The current numerical simulations have been performed for a very small propeller. It would be interesting to see whether the method, as it is described and tested in this thesis, also produces good results for a… Advisors/Committee Members: Van Terwisga, T.J.C., Pennings, P.C..
Timmer, M A. “The resonance frequency of tip-vortex cavitation:.” 2015. Masters Thesis, Delft University of Technology. Accessed April 24, 2019. http://resolver.tudelft.nl/uuid:f150f227-645f-444d-bfcf-5430344018b0.
Timmer, M A. “The resonance frequency of tip-vortex cavitation:.” 2015. Web. 24 Apr 2019.
Timmer MA. The resonance frequency of tip-vortex cavitation:. [Internet] [Masters thesis]. Delft University of Technology; 2015. [cited 2019 Apr 24]. Available from: http://resolver.tudelft.nl/uuid:f150f227-645f-444d-bfcf-5430344018b0.
26. Eslami Arab, S. A Numerical Study on Design of Normal and T-Head Coastal Groins:.
▼ Groins are old and intuitive means of reducing erosion and are found along the coast worldwide, although according to CEM (Coastal Engineering Manual 2003), “they are probably the most misused and improperly designed of all coastal structures”. The original purpose of groins was to reduce local erosion, that is, to hold the width of beach in their vicinities. Despite the simplicity of groins, their interaction with the beach is complex, and existing functional design guidance is limited. On the other hand, over the past decade there have been significant advances in understanding of coastal sediment processes, predictive modeling capability, and field measurements. Therefore, with the existing numerical tools the current study will be conducted in order to achieve better insight into this specific topic, to find some design criteria for normal groins and T-shape groins. The first step in this research is to do a wide literature review to find some reliable data regarding wave height and current velocities in a groin field. An irregular wave field must be studied, since regular wave fields concentrate energy around a single frequency, so they produce exaggerated offshore bar and strong rip currents (Hulsbergen et al 1978). On the other hand, the abilities of Delft3D numerical model must be validated for modeling currents and morphological interaction of littoral zone and structures for the case. Once we comprehend the current models are capable of modeling different phenomena, a sensitivity analysis will be carried out to find some design rules for these structures. Advisors/Committee Members: Van Rijn, L.C., Walstra, D.J.R., Luijendijk, A.P.A., Zijlema, M., Stive, M.J.F..
Eslami Arab, S. “A Numerical Study on Design of Normal and T-Head Coastal Groins:.” 2009. Masters Thesis, Delft University of Technology. Accessed April 24, 2019. http://resolver.tudelft.nl/uuid:5e2f5262-8e03-40cf-bc5d-346295c64dfd.
Eslami Arab, S. “A Numerical Study on Design of Normal and T-Head Coastal Groins:.” 2009. Web. 24 Apr 2019.
Eslami Arab S. A Numerical Study on Design of Normal and T-Head Coastal Groins:. [Internet] [Masters thesis]. Delft University of Technology; 2009. [cited 2019 Apr 24]. Available from: http://resolver.tudelft.nl/uuid:5e2f5262-8e03-40cf-bc5d-346295c64dfd.
27. Maxwell, Brian McNeilly. Turbulent Combustion Modelling of Fast-Flames and Detonations Using Compressible LEM-LES .
▼ A novel approach to modelling highly compressible and reactive flows is formulated to provide high resolution closure of turbulent-scale reaction rates in the presence of very rapid transients in pressure and energy. For such flows, treatment of turbulent-micro scales are generally unattainable through traditional modelling techniques. To address this, the modelling strategy developed here is based on the Linear Eddy Model for Large Eddy Simulation (LEM-LES); a technique which has only previously been applied to weakly compressible flows. In the current formulation of the Compressible LEM-LES (CLEM-LES), special treatment of the energy balance on the model subgrid is accounted for in order for the model reaction rates to respond accordingly to strong shocks and rapid expansions, both of which may be present in reactive and supersonic flow fields. In the current study, the model implemented is verified and validated for various 1D and 2D flow configurations in a compressible Adaptive Mesh Refinement (AMR) framework. In 1D test cases, laminar and turbulent flame speeds and structure have been reproduced. Also, detonation speeds and initiation events are also captured with the model. For 2D model validation, unsteady and turbulent detonation propagation and initiation events, in a narrow channel, are simulated. Both test cases involve premixed methane-oxygen mixture at low pressures. The model is found to capture well the two-dimensional detonation cellular structure, behaviour, and initiation events that are observed in corresponding shock tube experiments. Furthermore, the effect of turbulent mixing rates is investigated though a single tuning constant. It was found that by increasing the intensity of turbulent fluctuations present, detonations exhibit larger and more irregular cell structures. Furthermore, the intensity of turbulent fluctuations is found to also have an effect on initiation events.
Maxwell, Brian McNeilly. “Turbulent Combustion Modelling of Fast-Flames and Detonations Using Compressible LEM-LES .” 2016. Thesis, University of Ottawa. Accessed April 24, 2019. http://hdl.handle.net/10393/34122.
Maxwell, Brian McNeilly. “Turbulent Combustion Modelling of Fast-Flames and Detonations Using Compressible LEM-LES .” 2016. Web. 24 Apr 2019.
Maxwell BM. Turbulent Combustion Modelling of Fast-Flames and Detonations Using Compressible LEM-LES . [Internet] [Thesis]. University of Ottawa; 2016. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/10393/34122.
28. Shallouf, Mohammad. Numerical Simulation of Airlift Pumps Operating under Two-Phase Flow Conditions for Aquaculture Systems .
▼ The airlift pump has been around since the late 18th century, yet it is rarely seen or used in industry. Recently, the aquaculture industry has shown great potential for the use of airlift pumps operating under two-phase flow conditions to increase the operating efficiency of such facilities. This thesis presents both numerical and experimental investigations of the operation and performance characteristics of an airlift pump system. Experimental verification was also performed of an airlift pump that was integrated with a fish farm raceway in an aquaculture facility. Utilizing the Volume of Fluid (VOF) multi-phase model along with the K-ε turbulence model, a numerical study using ANSYS Fluent 19.0 was performed for the two-phase flow hydrodynamics in airlift pump injectors. The study was carried out for both the two-phase flow in the pump riser, and for the flow in an open channel raceway. Also, the performance of the airlift pump was evaluated experimentally for a 2.54 cm dimeter airlift pump in the lab. The numerical results were found to be in agreement with the experiments within ±20%. These simulation results were used to scale an airlift pump to operate in a 3.5 m3 raceway system. The numerical results had an average RMS agreement of ±15% with the experimental results. The present study was found to present a great tool for optimizing the airlift pump performance, as well as modifying the design of future aquaculture systems or other two-phase flow applications Advisors/Committee Members: Ahmed, Wael (advisor).
Shallouf, Mohammad. “Numerical Simulation of Airlift Pumps Operating under Two-Phase Flow Conditions for Aquaculture Systems .” 2019. Thesis, University of Guelph. Accessed April 24, 2019. https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14753.
Shallouf, Mohammad. “Numerical Simulation of Airlift Pumps Operating under Two-Phase Flow Conditions for Aquaculture Systems .” 2019. Web. 24 Apr 2019.
Shallouf M. Numerical Simulation of Airlift Pumps Operating under Two-Phase Flow Conditions for Aquaculture Systems . [Internet] [Thesis]. University of Guelph; 2019. [cited 2019 Apr 24]. Available from: https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14753.
29. Hsu, Byron C. Analysis of Extracellular ATP Distribution in the Intervertebral Disc Using a Finite Element Model.
▼ Extracellular adenosine triphosphate (ATP) released from cells can mediate a diverse number of biological responses, such as cell secretion, inflammation, and immune reactions through signaling pathways. According to Wang et al. (2013), the extracellular ATP concentration has been measured to accumulate to a high level in the nucleus pulposus (NP) region in the intervertebral disc (IVD), approximately 165 ?M. Since extracellular ATP is involved in a variety of cellular activities, the role of ATP distribution and accumulation in the IVD should be investigated. The objective of this study is to examine the effects of mechanical compression on the distribution of extracellular ATP and its adenine derivatives in the IVD using triphasic mechano-electrochemical theory. This theory describes the mechanical behavior and transport phenomena of charged hydrated soft tissue such as the IVD. Michaelis-Menten kinetics was used to model ATP hydrolysis and incorporated into a finite element model. Experiments were performed to measure Michaelis-Menten parameters of annulus fibrosus (AF) and NP cells. Results of the ATP hydrolysis experiments show that the maximum reaction velocity, Vmax, for AF cells is significantly greater than the value for NP cells. Thus, the extracellular ATP hydrolysis rate for AF cells could be significantly greater than the rate for NP cells. By comparing the results with the findings reported by Wang et al. (2013), the theoretical analysis indicated that mechanical loading may promote ATP hydrolysis and induce an intrinsic cellular response. Based on a finite element model, this study simulates the distribution of extracellular ATP and its adenine derivatives in the IVD under mechanical loading. Advisors/Committee Members: Chun-Yuh Charles Huang, Francesco Travascio, Alicia Renee Jackson.
Hsu, Byron C. “Analysis of Extracellular ATP Distribution in the Intervertebral Disc Using a Finite Element Model.” 2014. Thesis, University of Miami. Accessed April 24, 2019. https://scholarlyrepository.miami.edu/oa_theses/486.
Hsu, Byron C. “Analysis of Extracellular ATP Distribution in the Intervertebral Disc Using a Finite Element Model.” 2014. Web. 24 Apr 2019.
Hsu BC. Analysis of Extracellular ATP Distribution in the Intervertebral Disc Using a Finite Element Model. [Internet] [Thesis]. University of Miami; 2014. [cited 2019 Apr 24]. Available from: https://scholarlyrepository.miami.edu/oa_theses/486.
30. GHIMIRE, BIDUR. HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS .
▼ In this study, a comprehensive approach including mathematical, numerical and experimental study has been taken in order to develop new models for describing free surface flow behavior in porous media. The study suggested that modeling free-surface flow in porous media is possible using a single equation capable of showing proper transition between inertial and classical Darcian flow, based on the similarity distribution functions of depth and velocity. The developed integral model inherits both the flow regimes as depicted in the analysis. For both laminar and turbulent flows through porous media, the integral models give satisfactory results. Also the proposed algorithm for numerical simulation is capable of solving various problems of free-surface flow through porous media. This study adds a new dimension to fluid flow in porous media by replacing Darcy's equation with new models that are capable of representing both Darcy and non-Darcy flow behaviors. These are new nonlinear ordinary differential equations inherited both the flow regimes investigated. Integral formulations for unsteady depth distribution, velocity and front speed under constant water level and constant flux discharge inlet conditions have been developed based on similarity law. The formulations presented provide additional analytical insight about the intrusion dynamics. It is pointed out that, based on the self-similarity analysis, the temporal intrusion processes can be categorized into the inertia-pressure (IP) and the pressure-drag (PD) regimes. The early inertia-pressure regime is followed by the pressure-drag regime. In addition, the integral models proposed can be successfully used for the solution of a host of other nonlinear problems that admit self-similarity. The analytical and numerical solutions for constant inlet water level condition are verified with experimental observations. The unsteady distributions of flow depth, inflow velocity and front speeds are compared for various porous media characterized by its corresponding porosity and permeability. Analyses indicate that the integral models clearly represent the nonlinear flow behavior in porous media both in laminar and turbulent flow conditions. The integral model results are in agreement with those obtained by similarity solution for the temporal change of velocity, depth at inlet and front positions. The thesis also presents a computational fluid dynamics (CFD) model developed for the analysis of unsteady free-surface flows through porous media. Vertical two-dimensional numerical simulations are carried out for the free-surface flow inside the porous media governed by a set of Navier-Stokes equations extended for porous media flow. This model includes the convective and local inertia terms along with viscous diffusion term and resistance term comprising Darcy's linear resistance and Forchheimer's inertial resistance terms. The Finite volume method is applied using constrained interpolated propagation (CIP) method and highly simplified marker and cell (HSMAC) type pressure… Advisors/Committee Members: 細田, 尚 (advisor), 戸田, 圭一 (advisor), 岸田, 潔 (advisor).
GHIMIRE, BIDUR. “HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS .” 2009. Thesis, Kyoto University. Accessed April 24, 2019. http://hdl.handle.net/2433/85382.
GHIMIRE, BIDUR. “HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS .” 2009. Web. 24 Apr 2019.
GHIMIRE B. HYDRAULIC ANALYSIS OF FREE-SURFACE FLOWS INTO HIGHLY PERMEABLE POROUS MEDIA AND ITS APPLICATIONS . [Internet] [Thesis]. Kyoto University; 2009. [cited 2019 Apr 24]. Available from: http://hdl.handle.net/2433/85382.