| 1. |
- Abrahamyan, Lilit, et al.
(författare)
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A Problem Solving Environment for Image-Based Computational Hemodynamics
- 2005
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Konferensbidrag (refereegranskat)abstract
- We introduce a complete problem solving environment designed for pulsatile flows in 3D complex geometries, especially arteries. Three-dimensional images from arteries, obtained from e.g. Magnetic Resonance Imaging, are segmented to obtain a geometrical description of the arteries of interest. This segmented artery is prepared for blood flow simulations in a 3D editing tool, allowing to define in- and outlets, to filter and crop part of the artery, to add certain structures ( e.g. a by-pass, or stents ), and to generate computational meshes as input to the blood flow simulators. Using dedicated fluid flow solvers the time dependent blood flow in the artery during one systole is computed. The resulting flow, pressure and shear stress fields are then analyzed using a number of visualization techniques. The whole environment can be operated from a desktop virtual reality system, and is embedded in a Grid computing environment.
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| 2. |
- Artoli, Abdel Monim, et al.
(författare)
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Accuracy versus Performance in Lattice Boltzmann BGK Accuracy versus Performance in Lattice Boltzmann BGK Simulations of Systolic Flows
- 2004
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Ingår i: Lecture Notes in Computational Science and Engineering. - 1439-7358. ; 3039, s. 548-555
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work is to tune the lattice Boltzmann BGK (LBGK) simulation parameters in order to achieve optimum accuracy and performance for. time dependent flows. We present detailed analysis of the accuracy and performance of LBGK in simulating pulsatile Newtonian flow in a straight rigid 3D tube. We compare the obtained velocity profiles and shear stress to the analytic Womersley solutions. A curved boundary condition is used for the walls and the accuracy and performance are compared to that obtained by using the bounce-back on the links. A technique to reduce compressibility errors during simulations based on reducing the Mach number is presented.
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| 3. |
- Axner, Lilit, et al.
(författare)
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Simulating Time Harmonic Flows with the Regularized L-BGK Method
- 2007
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Ingår i: International Journal of Modern Physics C. - 0129-1831. ; 18:4, s. 661-666
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Tidskriftsartikel (refereegranskat)abstract
- A recent improvement of the lattice BGK model, based on a regularization of the precollision distribution function, is applied to three dimensional Womersley flow. The accuracy and the stability of the model are essentially improved by using this regularization. A good agreement with analytical Womersley solution is presented, as well as an improvement of the accuracy over standard L-BGK. Numerical stability of the scheme for a range of Reynolds and Womersley numbers is also presented, demonstrating an enhancement of the stability range of L-BGK for this type of flows.
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| 4. |
- Axner, Lilit, et al.
(författare)
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Simulations of time harmonic blood flow in the Mesenteric artery: comparing finite element and lattice Boltzmann methods
- 2009
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Ingår i: Biomedical engineering online. - 1475-925X. ; 8:23, s. 28-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Systolic blood flow has been simulated in the abdominal aorta and the superior mesenteric artery. The simulations were carried out using two different computational hemodynamic methods: the finite element method to solve the Navier Stokes equations and the lattice Boltzmann method. Results: We have validated the lattice Boltzmann method for systolic flows by comparing the velocity and pressure profiles of simulated blood flow between methods. We have also analyzed flow-specific characteristics such as the formation of a vortex at curvatures and traces of flow. Conclusion: The lattice Boltzmann Method is as accurate as a Navier Stokes solver for computing complex blood flows. As such it is a good alternative for computational hemodynamics, certainly in situation where coupling to other models is required.
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| 5. |
- Hoenen, Olivier, et al.
(författare)
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Designing and running turbulence transport simulations using a distributed multiscale computing approach
- 2013
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Ingår i: 40th European Physical Society Conference on Plasma Physics. ; 2, s. 1094-1097
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Multiscale simulation involving slow transport and fast turbulent timescales is one amongstthree key computational challenges for Magnetic Confinement Plasmas, as identified in thePRACE report “The Scientific Case for HPC in Europe 2012-2020”. Whereas in global gy-rokinetic simulation the main challenge is parallelization efficiency (global gyrokinetic codesscaling to a huge amount of cores), the difficulty of the mulstiscale approach rely more on easeand performance of coupling single scale models together. This coupling requires generic meth-ods which have to be efficient and portable, especially when one (or more) single scale model isexecuted remotely as it may require specific hardware, bigger HPC systems or local databasesaccess.The MAPPER project is developing a software infrastructure dedicated to the design and theexecution of such distributed multiscale applications. It relies on a coupling library (MUSCLE)and few other to control the workflow execution and perform data communication betweenthe different single scale components (“kernels”). Communication is done in a transparent waywhether the kernels run locally or on a remote HPC system.We have implemented such application by using the MAPPER infrastructure and stand alonecodes developed within the EFDA Integrated Tokamak Modelling (ITM): 1-D transport equa-tions solver, 2-D geometry given by an equilibrium code, and transport coefficients given by a3-D fluxtube code. Due to the non-intrusive approach of the coupling library and to ITM efforton generic data structures, implementation of kernels is straightforward and the whole appli-cation is modular. This contribution presents the implementation, performance and preliminaryresults obtained with such multiscale method applied on present-day Tokamak configurations.
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