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Stenting as porous media in anatomically accurate geometries. A comparison of models and spatial heterogeneity

Published: Aug 2020

- Best results when simulating flow diverters as porous media are obtained on models based on geometrical properties using a heterogeneous medium based on equations for flat rhomboidal wire frames. (In this paper, such model is called "R2")
- Flow diverters can be simulated with porous media with a good agreement to standard CFD simulations in less than a quarter of the time.

Submitted by Nicolás Dazeo

Heterogeneous Porous Media Simulation

Published: Nov 2018

- An anisotropic heterogeneous porous media is implemented in OpenFOAM.
- Porous media coefficients can be model as a tensor field.

Submitted by Nicolás Dazeo

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A comparative study of porous medium CFD models for flow diverter stents: Advantages and shortcomings

Published: Aug 2018

In computational fluid dynamics, there is a high interest in modeling flow diverter stents as porous media due to its reduced computational loads. One of the main difficulties of such models is proper parameter setup. Most authors assume flow diverter's wire screen as an isotropic and homogeneous medium, while others proposes anisotropic configurations, yet very little is discussed about the effect of these assumptions on model's accuracy. In this paper, we compare the effect of different models on hemodynamics in relation to their parameters. The fidelity and efficiency of the different models to capture wire screen effect on fluid flow are quantitatively analyzed and compared.

Submitted by Nicolás Dazeo

Impact of an oblique breaking wave on a wall

Author:

Jian-Jun ShuPublished: Mar 2014

The intention of this paper is to study impact force of an oblique-angledslamming wave acting on a rigid wall. In the present study the analyticalapproach is pursued based on a technique proposed by the author. A nonlineartheory in the context of potential flow is presented for determining accuratelythe free-surface profiles immediately after an oblique breaking waveimpingement on the rigid vertical wall that suddenly starts from rest. Thesmall-time expansion is taken as far as necessary to include the acceleratingeffect. The analytical solutions for the free-surface elevation are derived upto the third order. The results derived in this paper are of particularinterest to the marine and offshore engineering industries, which will find theinformation useful for the design of ships, coastal and offshore.

Retrieved from arxiv

Contemporary Approach for Simulation and Computation of Fluid Flows in
Centrifugal Hydromachines

Authors:

Alexey N. Kochevsky, Victor G. NenyaPublished: Sep 2004

The article describes various aspects of mathematical modeling of fluidflows, both in general and with reference to hydraulic machinery. The articlereviews historical development of corresponding methods of mathematicalmodeling. Implementation of these aspects in modern commercial CFD softwaretools is described together with advantages and disadvantages of implementedmethods. The conclusion is drawn concerning possibilities of computation offluid flows nowadays.

Retrieved from arxiv

Heat transport by turbulent Rayleigh-B'enard Convection in cylindrical
cells with aspect ratio one and less

Authors:

Alexei Nikolaenko, Eric Brown, Denis Funfschilling, Guenter AhlersPublished: Sep 2004

We present high-precision measurements of the Nusselt number N as a functionof the Rayleigh number R for cylindrical samples of water (Prandtl number sigma= 4.4) with a diameter D of 49.7 cm and heights L = 116.3, 74.6, and 50.6 cm,as well as for D = 24.8 cm and L = 90.2 cm. For each aspect ratio Gamma = D/L =0.28, 0.43, 0.67, and 0.98 the data cover a range of a little over a decade ofR. The maximum R ~= 10^12 and Nusselt number N ~= 600 were reached for Gamma =0.43 and D = 49.7. The data were corrected for the influence of the finiteconductivity of the top and bottom plates on the heat transport in the fluid toobtain estimates of N_infty for plates with infinite conductivity. The resultsfor N_infty and Gamma >= 0.43 are nearly independent of Gamma. For Gamma =0.275 N_infty falls about 2.5 % below the other data. For R ~<= 10^11, theeffective exponent gamma_eff of N_infty = N_0 R^gamma_eff is about 0.321,larger than those of the Grossmann-Lohse model with its current parameters byabout 0.01. For the largest Rayleigh numbers covered for Gamma = 0.98, 0.67,and 0.43, gamma_eff saturates at the asymptotic value gamma = 1/3 of theGrossmann-Lohse model. The data do not reveal any crossover to a Kraichnanregime with gamma_eff > 1/3.

Retrieved from arxiv

Complex dynamics in double-diffusive convection

Authors:

Esteban Meca, Isabel Mercader, Oriol Batiste, Laureano Ramírez-PiscinaPublished: Nov 2004

The dynamics of a small Prandtl number binary mixture in a laterally heatedcavity is studied numerically. By combining temporal integration, steady statesolving and linear stability analysis of the full PDE equations, we have beenable to locate and characterize a codimension-three degenerate Takens-Bogdanovpoint whose unfolding describes the dynamics of the system for a certain rangeof Rayleigh numbers and separation ratios near S=-1.

Retrieved from arxiv

Machine Learning for Physics-Informed Generation of Dispersed Multiphase
Flow Using Generative Adversarial Networks

Authors:

B. Siddani, S. Balachandar, W. C. Moore, Y. Yang, R. FangPublished: May 2020

Fluid flow around a random distribution of stationary spherical particles isa problem of substantial importance in the study of dispersed multiphase flows.In this paper we present a machine learning methodology using GenerativeAdversarial Network framework and Convolutional Neural Network architecture torecreate particle-resolved fluid flow around a random distribution ofmonodispersed particles. The model was applied to various Reynolds number andparticle volume fraction combinations spanning over a range of [2.69, 172.96]and [0.11, 0.45] respectively. Test performance of the model for the studiedcases is very promising.

Retrieved from arxiv

A target-fixed immersed-boundary formulation for rigid bodies
interacting with fluid flow

Authors:

Tzu-Yuan Lin, Hsin-Yu Hsieh, Hsieh-Chen TsaiPublished: Jan 2020

We present an immersed boundary projection method formulated in a body-fixedframe of reference for flow-structure interaction (FSI) problems involvingrigid bodies with complex geometries. The body-fixed formulation is aimed atmaximizing the accuracy of surface stresses on the FSI body (the target) onduring spatial and temporal discretization. The incompressible vorticityequations and Newton's equations of motion are coupled implicitly so that themethod remains stable for low solid-to-fluid mass ratios. The influence offictitious fluid inside the rigid bodies is considered and the spuriousoscillations in surface stresses are filtered to impose physically correctrigid body dynamics. Similar to many predecessors of the immersed boundaryprojection method, the resulting discrete system is solved efficiently using ablock-LU decomposition. We then validate the method with two-dimensional testproblems of a neutrally buoyant cylinder migrating in a planar Couette flow anda freely falling or rising cylindrical rigid body.

Retrieved from arxiv

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