Article
Physics, Fluids & Plasmas
Mahendra K. Verma, Shadab Alam
Summary: In this paper, we study the shell model of turbulence using renormalization group (RG) and find that the RG equation holds true. We also establish a relationship between the Kolmogorov constant and the wave number and velocity of shell n. The theoretical predictions are verified through numerical simulations.
Article
Computer Science, Interdisciplinary Applications
T. Fabbri, G. Balarac, V. Moureau, P. Benard
Summary: In this paper, a LES-based FSI solver is proposed for high fidelity numerical simulations of chordwise flexible blade. The solver is capable of accurately predicting the stall dynamics and computing the deformation of a solid with complex geometry. It is validated independently and successfully applied to experimental 3D complex cases with high Reynolds number.
COMPUTERS & FLUIDS
(2023)
Article
Computer Science, Interdisciplinary Applications
Tobias Tolle, Dirk Gruending, Dieter Bothe, Tomislav Maric
Summary: We propose a numerical method for calculating volume fractions from triangulated surfaces immersed in unstructured meshes. The method utilizes geometric calculations of signed distances and an approximate solution of the Laplace equation. It ensures high absolute accuracy and is applicable to triangulated surface models with technical geometrical complexity.
COMPUTER PHYSICS COMMUNICATIONS
(2022)
Article
Geography, Physical
Jason Duguay, Pascale Biron, Thomas Buffin-Belanger
Summary: Researchers analyzed aerial video and numerical simulation results, finding different types of turbulent structures form at river confluences, including vertically orientated vortices, secondary flow helical cells, and streamwise-orientated vortices. These turbulent structures interact with each other and play significant roles in the mixing processes.
EARTH SURFACE PROCESSES AND LANDFORMS
(2022)
Article
Energy & Fuels
Jana Hoffmann, Niklas Mirsch, Walter Vera-Tudela, Dario Wuethrich, Jorim Rosenberg, Marco Guenther, Stefan Pischinger, Daniel A. Weiss, Kai Herrmann
Summary: This study conducts a parametric investigation on the influence of valve lift and mass flow variation of an inlet valve on flow structures in the test engine Flex-OeCoS. The results show that valve lift has a significant impact on flow structures, while mass flow variation has a minimal effect.
Article
Engineering, Chemical
Maryam Askarishahi
Summary: The researchers developed a stable OpenFOAM solver for Immersed Boundary Method and implemented a fluid-structure interaction (FSI) coupling method to accurately calculate the fluid forcing term and particle velocity. The solver was validated for fixed and moving bodies, and the accuracy of various FSI schemes and their impact on solid and fluid flow behavior in a viscous flow were evaluated. The study also analyzed the dynamic flow behavior of colliding particles and predicted the effective restitution coefficient of particles in a viscous flow.
ADVANCED POWDER TECHNOLOGY
(2023)
Article
Engineering, Multidisciplinary
Costanza Arico, Marco Sinagra, Zied Driss, Tullio Tucciarelli
Summary: This paper introduces a new numerical methodology for solving 2D nonisothermal incompressible flows in irregular geometries, discretizing the governing equations over unstructured triangular meshes. The algorithm proposed includes prediction and correction steps, with the prediction steps using the MAST numerical Eulerian scheme and the correction steps involving solving large linear systems. The matrix coefficients are constant in time, allowing for efficient factorization and saving computational time.
APPLIED MATHEMATICAL MODELLING
(2022)
Article
Engineering, Mechanical
Buchen Wu, Jinhua Lu, HsuChew Lee, Chang Shu, Minping Wan
Summary: Thermal-fluid-structure interaction is a common issue in natural environment and manmade devices. This study develops a novel coupling approach using EIB-RTLBFS to tackle TFSI problems. The experimental results demonstrate that EIB-RTLBFS can accurately predict the nonlinear characteristics of multiphysics systems.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2022)
Article
Mechanics
H. Chen, P. Yu, C. Shu
Summary: A novel numerical method, UIB-LBFS, is proposed for simulating incompressible flows past homogeneous porous bodies. The method introduces a diffuse layer to unify the governing equations in porous and pure-fluid domains, and employs a fractional-step technique to split the computational procedure. The accuracy and reliability of the method are proven through numerical validations.
Article
Engineering, Multidisciplinary
Mustafa Aggul, Alexander E. Labovsky, Kyle J. Schwiebert
Summary: This paper proposes a method to address the fluid-fluid interaction problem, where two flows are coupled through a nonlinear rigid lid condition, and one or both flows have high Reynolds numbers. The model combines the NS-omega turbulence model with a partitioning method, allowing for efficient decoupling, usage of preexisting solvers, and resolving high Reynolds number flows. The model is unconditionally stable and has optimal convergence properties. It also allows for non-filtered velocity in the interface terms, which improves the quality of the model's solution.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Cardiac & Cardiovascular Systems
Leonardo Pietrasanta, Shaokai Zheng, Dario De Marinis, David Hasler, Dominik Obrist
Summary: The development of turbulence after transcatheter aortic valve (TAV) implantation may negatively affect the long-term performance and durability of the valves. This study investigated the turbulent flow generated after TAV implantation using experimental and velocimetry techniques. The results suggest that the degree of expansion of the TAV in-situ is related to the onset of turbulence and that a smaller and less regular opening area might introduce flow instabilities that could be detrimental for the long-term performance of the valve.
FRONTIERS IN CARDIOVASCULAR MEDICINE
(2022)
Article
Computer Science, Interdisciplinary Applications
Kyle A. Schau, Chelsea Johnson, Julia Muller, Joseph C. Oefelein
Summary: This study presents an ensemble approach to generating turbulent inflow boundary conditions using the Synthetic Eddy Method. It improves signal accuracy and reduces the cost of generating the inflow signal by eliminating typical restrictions associated with the method. The approach allows flexibility in specifying synthetic eddy parameters while accurately reproducing input Reynolds stresses and desired turbulent characteristics.
COMPUTERS & FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
L. M. Yang, C. Shu, Z. Chen, Y. Y. Liu, J. Wu, X. Shen
Summary: A high-order gas kinetic flux solver (GKFS) is developed for 2D compressible flows, which evaluates numerical fluxes based on the local asymptotic solution to the Boltzmann equation. It achieves high-order accuracy through a simplified local asymptotic solution and outperforms the second-order counterpart in numerical examples, demonstrating its accuracy and capability.
Article
Thermodynamics
Farhad A. Amiri, Junfeng Zhang
Summary: The paper introduces an immersed membrane method for simulating mass transfer across flexible semipermeable membranes, effectively addressing technical challenges. By replacing the sharp membrane interface with an immersed membrane layer, the mass transfer process can be solved using a uniform numerical scheme. Validation and demonstration simulations show that the method accurately represents the membrane effect on mass transfer.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2021)
Article
Engineering, Multidisciplinary
Keiji Onishi, Makoto Tsubokura
Summary: The method proposed in this study combines the topology-free method and the immersed boundary method, which is suitable for viscous and incompressible flows at high Reynolds numbers, particularly for handling dirty and highly complex geometries. By utilizing ghost-cell technique and distributed forcing technique for boundary conditions imposition, along with an axis-projected interpolation scheme to avoid searching failures, the method achieves a topology-free immersed boundary, making it ideal for flow simulations of intricate geometries.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2021)
Article
Mathematical & Computational Biology
Thierry Mignon, Simon Mendez
Summary: At low shear rates, studying the dynamics of a single red blood cell in shear flow involves complex behaviors that require mathematical models and techniques from algebraic geometry. By rewriting existing models and determining steady-state solutions, a better understanding of the transition between different motions of red blood cells can be achieved.
MATHEMATICAL MODELLING OF NATURAL PHENOMENA
(2021)
Article
Biochemical Research Methods
Pierre Taraconat, Jean-Philippe Gineys, Damien Isebe, Franck Nicoud, Simon Mendez
Summary: Numerical results emphasize the link between cell flow-induced rotation and error in measured volume, leading to the development of two methods to identify and reject rotation-associated pulses. Detecting and rejecting rotation-induced pulses yield results comparable to hydrodynamical focusing, the gold standard implementation of the Coulter principle.
Article
Multidisciplinary Sciences
Thomas Puiseux, Anou Sewonu, Ramiro Moreno, Simon Mendez, Franck Nicoud
Summary: A numerical approach for simulating time-resolved 3D phase-contrast MRI under realistic flow conditions is presented. The Navier-Stokes and Bloch equations are solved with specific strategies to reduce computational cost. The simulated results compare favorably with experimental data.
Article
Physics, Fluids & Plasmas
P. Matteoli, F. Nicoud, S. Mendez
Summary: This study compares the impact of internal fluid viscosity and membrane viscosity on tank-treading red blood cells using numerical simulations supported by experimental data. It is found that both viscosities decrease the tank-treading frequency and have moderate effects on the cell deformation. Furthermore, direct inference of membrane viscosity as a function of shear rate is proposed based on the comparison between simulations and experiments.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Acoustics
Yunyun Sun, Florian Vixege, Khuram Faraz, Simon Mendez, Franck Nicoud, Damien Garcia, Olivier Bernard
Summary: In this article, a numerical framework for generating clinical-like color Doppler imaging (CDI) is presented. Synthetic blood vector fields and realistic clutter artifacts are simulated for evaluating and improving the quality of Doppler imaging techniques.
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
(2022)
Article
Engineering, Biomedical
Alain Berod, Christophe Chnafa, Simon Mendez, Franck Nicoud
Summary: Numerical computations of hemodynamics inside intracranial aneurysms treated by endovascular braided devices such as flow-diverters contribute to understanding and improving such treatment procedures. Nevertheless, these simulations yield high computational and meshing costs due to the heterogeneity of length scales between the dense weave of the fine struts of the device and the arterial volume.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING
(2022)
Article
Engineering, Biomedical
Florian Vixege, Alain Berod, Yunyun Sun, Simon Mendez, Olivier Bernard, Nicolas Ducros, Pierre-Yves Courand, Franck Nicoud, Damien Garcia
Summary: The iVFM technique, improved with physical constraints, accurately measures blood flow velocity in the heart and shows promising potential in assessing diastolic function in clinical settings.
PHYSICS IN MEDICINE AND BIOLOGY
(2021)
Article
Engineering, Industrial
Willy Garcia, Simon Mendez, Baptiste Fray, Alexandre Nicolas
Summary: This study evaluates the risks of Covid-19 spread in various daily-life situations involving crowds, and develops a method for inferring the global number of new infections. Factors such as crowd density and the geometric shape of queues are found to significantly affect disease transmission risks.
Article
Engineering, Biomedical
Florian Vixege, Alain Berod, Pierre-Yves Courand, Simon Mendez, Franck Nicoud, Philippe Blanc-Benon, Didier Vray, Damien Garcia
Summary: Three-dimensional intraventricular vector flow mapping (3D-iVFM) is a method for observing the velocity vector fields of blood flow in the left ventricular cavity through three-dimensional reconstruction. By using a clinical triplane echocardiographic mode, 3D-iVFM is able to recover three-component velocity vector fields in the entire ventricular volume. Our results indicate that 3D-iVFM can accurately estimate the full-volume information of left intraventricular hemodynamics and decipher the dynamics of the intraventricular vortex during systole.
PHYSICS IN MEDICINE AND BIOLOGY
(2022)
Article
Radiology, Nuclear Medicine & Medical Imaging
Morgane Garreau, Thomas Puiseux, Solenn Toupin, Daniel Giese, Simon Mendez, Franck Nicoud, Ramiro Moreno
Summary: This study evaluated hemodynamic markers obtained by accelerated GRAPPA and compressed sensing 4D flow MRI sequences under complex flow conditions. The results showed similar hemodynamic patterns between MRI and computational fluid dynamics simulations, with larger discrepancies near the boundary walls. MRI scans tended to overestimate velocity profiles and peak velocities, but showed good agreement for flow rates. Computational fluid dynamics simulations are a useful tool to assess these differences, but are sensitive to modeling parameters.
MAGNETIC RESONANCE IN MEDICINE
(2022)
Article
Engineering, Biomedical
Franck Nicoud
Summary: An adjoint-based methodology is proposed to compute the gradient of outcomes in the coagulation cascade mathematical models. The method is validated using a simple case involving 3 species and further applied to a complex model with 34 species and 45 reactions. The results show that the method produces consistent gradient estimates at a lower computational cost compared to the finite differences approximation.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING
(2023)
Article
Engineering, Biomedical
Alain Berod, Fernando Mut, Juan Cebral, Simon Mendez, Christophe Chnafa, Franck Nicoud
Summary: The study applies a heterogeneous model developed by Berod et al to evaluate the hemodynamic effects of endovascular prostheses on cerebral aneurysms. The model shows good agreement with the actual treatment outcomes and successfully reproduces the jetting-type flows generated downstream of the struts.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING
(2023)
Article
Mechanics
S. Blanchard, N. Odier, L. Gicquel, B. Cuenot, F. Nicoud
Summary: In the framework of wall-modeled large-eddy simulation (WMLES), the static Smagorinsky model predicts efficiently the wall shear stress, while more advanced static models like WALE or Sigma fail in this aspect. Smagorinsky is known to be too dissipative in the bulk flow and purely sheared flows, whereas the other models are better suited for near-wall flows.
