scholarly journals Tissue flow through pores: a computational study

2021 ◽  
Author(s):  
Felix Kempf ◽  
Andriy Goychuk ◽  
Erwin Frey
Keyword(s):  
Cancer Metastasis ◽  
Computational Study ◽  
Cell Sheet ◽  
Hexagonal Lattice ◽  
Major Influence ◽  
Cellular Potts Model ◽  
Local Ordering ◽  
Classical Fluids ◽  
Flow Through ◽  
Epithelial Sheet

Cell migration is of major importance for the understanding of phenomena such as morphogenesis, cancer metastasis, or wound healing. In many of these situations cells are under external confinement. In this work we show by means of computer simulations with a Cellular Potts Model (CPM) that the presence of a bottleneck in an otherwise straight channel has a major influence on the internal organisation of an invading cellular monolayer and the motion of individual cells therein. Comparable to a glass or viscoelastic material, the cell sheet is found to exhibit features of both classical solids and classical fluids. The local ordering on average corresponds to a regular hexagonal lattice, while the relative motion of cells is unbounded. Compared to an unconstricted channel, we observe that a bottleneck perturbs the formation of regular hexagonal arrangements in the epithelial sheet and leads to pile-ups and backflow of cells near the entrance to the constriction, which also affects the overall invasion speed. The scale of these various phenomena depends on the dimensions of the different channel parts, as well as the shape of the funnel domain that connects wider to narrower regions.

scholarly journals Blood Damage Through a Bileaflet Mechanical Heart Valve: A Quantitative Computational Study Using a Multiscale Suspension Flow Solver

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
B. Min Yun ◽  
Cyrus K. Aidun ◽  
Ajit P. Yoganathan
Keyword(s):  
Numerical Method ◽  
Heart Valves ◽  
Computational Study ◽  
Mechanical Heart Valve ◽  
Complex Flow ◽  
Damage Potential ◽  
Spatiotemporal Resolution ◽  
Jude Medical ◽  
Blood Damage ◽  
Flow Through

Bileaflet mechanical heart valves (BMHVs) are among the most popular prostheses to replace defective native valves. However, complex flow phenomena caused by the prosthesis are thought to induce serious thromboembolic complications. This study aims at employing a novel multiscale numerical method that models realistic sized suspended platelets for assessing blood damage potential in flow through BMHVs. A previously validated lattice-Boltzmann method (LBM) is used to simulate pulsatile flow through a 23 mm St. Jude Medical (SJM) Regent™ valve in the aortic position at very high spatiotemporal resolution with the presence of thousands of suspended platelets. Platelet damage is modeled for both the systolic and diastolic phases of the cardiac cycle. No platelets exceed activation thresholds for any of the simulations. Platelet damage is determined to be particularly high for suspended elements trapped in recirculation zones, which suggests a shift of focus in blood damage studies away from instantaneous flow fields and toward high flow mixing regions. In the diastolic phase, leakage flow through the b-datum gap is shown to cause highest damage to platelets. This multiscale numerical method may be used as a generic solver for evaluating blood damage in other cardiovascular flows and devices.

scholarly journals On the Transition From Creeping to Inertial Flow in Arrays of Cylinders

2010 ◽  
Author(s):  
K. Yazdchi ◽  
S. Srivastava ◽  
S. Luding
Keyword(s):  
Porous Media ◽  
Darcy’S Law ◽  
Computational Study ◽  
Darcy's Law ◽  
Natural Processes ◽  
Inertial Flow ◽  
Flow Through ◽  
High Reynolds ◽  
An Array Of Cylinders ◽  
Element Method

Many important natural processes involving flow through porous media are characterized by large filtration velocity. Therefore, it is important to know when the transition from viscous to the inertial flow regime actually occurs in order to obtain accurate models for these processes. In this paper, a detailed computational study of laminar and inertial, incompressible, Newtonian fluid flow across an array of cylinders is presented. Due to the non-linear contribution of inertia to the transport of momentum at the pore scale, we observe a typical departure from Darcy’s law at sufficiently high Reynolds number (Re). Our numerical results show that the weak inertia correction to Darcy’s law is not a square or a cubic term in velocity, as it is in the Forchheimer equation. Best fitted functions for the macroscopic properties of porous media in terms of microstructure and porosity are derived and comparisons are made to the Ergun and Forchheimer relations to examine their relevance in the given porosity and Re range. The results from this study can be used for verification and validation of more advanced models for particle fluid interaction and for the coupling of the discrete element method (DEM) with finite element method (FEM).

Flow Instabilities in Gas Turbine Chute Seals

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Joshua T. M. Horwood ◽  
Fabian P. Hualca ◽  
Mike Wilson ◽  
James A. Scobie ◽  
Carl M. Sangan ◽  
...  
Keyword(s):  
Large Scale ◽  
Computational Study ◽  
Leading Edge ◽  
Large Scale Structures ◽  
Strong Shear ◽  
Time Marching ◽  
Flow Through ◽  
Scale Structures ◽  
Large Scale Flow ◽  
Secondary Flow Field

Abstract The ingress of hot annulus gas into stator–rotor cavities is an important topic to engine designers. Rim-seals reduce the pressurized purge required to protect highly stressed components. This paper describes an experimental and computational study of flow through a turbine chute seal. The computations—which include a 360 deg domain—were undertaken using dlrtrace's time-marching solver. The experiments used a low Reynolds number turbine rig operating with an engine-representative flow structure. The simulations provide an excellent prediction of cavity pressure and swirl, and good overall agreement of sealing effectiveness when compared to experiment. Computation of flow within the chute seal showed strong shear gradients which influence the pressure distribution and secondary-flow field near the blade leading edge. High levels of shear across the rim-seal promote the formation of large-scale structures at the wheel-space periphery; the number and speed of which were measured experimentally and captured, qualitatively and quantitatively, by computations. A comparison of computational domains ranging from 30 deg to 360 deg indicates that steady features of the flow are largely unaffected by sector size. However, differences in large-scale flow structures were pronounced with a 60 deg sector and suggest that modeling an even number of blades in small sector simulations should be avoided.

Computational Study of the Downpull Force on High-Head Slide Gates

2019 ◽  
Author(s):  
Juan C. Arango Escobar ◽  
David Calderon Villegas ◽  
Aldo Benavides Moran ◽  
Alejandro Molina Ochoa
Keyword(s):  
Computational Study ◽  
Maximum Flow ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Cfd Simulations ◽  
Ansys Fluent ◽  
Flow Through ◽  
High Head ◽  
The One ◽  
Bottom Outlet

Abstract This paper presents CFD simulations of the flow through a real bottom outlet equipped with high-head slide gates. The operating head of the gates and the maximum flow rate are 70 m and 650 m3/s, respectively. The numerical simulations were performed in ANSYS-FLUENT version 19.2. VOF method was used to model the free surface flow downstream the slide gates. Hydrodynamic forces were calculated at nine gate openings for a standard 45° lip gate; the downpull coefficients obtained from the simulations were compared with estimates from Naudascher’s analytical method. According to the CFD results, the downpull force acting on the 45° lip gate is 5%–10% lower than the one estimated analytically for the analyzed gate positions. Additionally, the flow through an inverted 30° lip gate was simulated to estimate the downpull coefficient at various gate openings. These coefficients cannot be determined analytically. The methodology here described can easily be applied to different gate geometries for which design coefficients are not available.

scholarly journals Computational study on flow through truncated conical plug nozzle with base bleed

2019 ◽  
Vol 8 (2) ◽  
pp. 108-120 ◽  
Author(s):  
Prasanth P. Nair ◽  
Abhilash Suryan ◽  
Heuy Dong Kim
Keyword(s):  
Computational Study ◽  
Plug Nozzle ◽  
Flow Through ◽  
Base Bleed

Internal Jet Formation During Bubble Generation in Microchannels

2017 ◽  
Author(s):  
Felix Reichmann ◽  
Moritz Koch ◽  
Sarah Körner ◽  
Norbert Kockmann
Keyword(s):  
Bubble Surface ◽  
Surface Forces ◽  
Liquid Jets ◽  
Major Influence ◽  
Jet Formation ◽  
Bubble Generation ◽  
Structure Interaction ◽  
Bubble Breakup ◽  
Flow Through ◽  
Short Time

Bubble generation is a very dynamic process including surface forces with fluid flow and structure interaction on short time and length scales. This study describes interaction effects during bubble generation in combination with bubble flow through a nozzle for redispersion purpose. At certain flow velocities and phase ratios, liquid jets within gas bubbles have been observed in microchannels, which origin from the rear tip of the bubble cap and penetrate through the whole bubble. The penetration of the filament or thread leads to bubble surface corrugation and causes bubble breakup, when the opposite cap of the bubble is hit. In the case of micronozzles behind the contact element, jet formation within the bubble is also caused by another bubble leaving the micronozzle and probably leading to a pressure disturbance acting on the just generated bubble. First data indicate major influence parameters in jet formation; however, systematic investigations are following.

Topological rearrangements and flow simulation of dry ordered foams

2014 ◽  
Vol 05 (supp01) ◽  
pp. 1441007 ◽  
Author(s):  
J. S. Espinoza Ortiz ◽  
H. Belich ◽  
M. T. D. Orlando ◽  
R. E. Lagos
Keyword(s):  
Strain Rate ◽  
Critical Behavior ◽  
Potts Model ◽  
Driving Force ◽  
Flow Simulation ◽  
Two Dimensional ◽  
Fluid Regime ◽  
Cellular Potts Model ◽  
Flow Through ◽  
Liquid Foam

Flow through a narrow bent channel may induce topological rearrangements in a two-dimensional monodispersed dry liquid foam. We use the Cellular Potts Model to simulate a foam under a variable driving force in order to investigate the strain-rate response from these rearrangements. We observe a set of foams' behaviors ranging from elastic, viscoelastic to fluid regime. Bubble's topological rearrangements are localized and their cumulative rearrangements change linearly with time, thus nonavalanches critical behavior is found. The strain-rate affects the rate of topological rearrangements, its dependence on the drag force is nonlinear, obeying a Herschel–Bulkley-like relationship below the foam's flow point.

Modelling wound closure in an epithelial cell sheet using the cellular Potts model

2015 ◽  
Vol 7 (10) ◽  
pp. 1253-1264 ◽  
Author(s):  
Adrian R. Noppe ◽  
Anthony P. Roberts ◽  
Alpha S. Yap ◽  
Guillermo A. Gomez ◽  
Zoltan Neufeld
Keyword(s):  
Epithelial Cell ◽  
Potts Model ◽  
Wound Closure ◽  
Cell Layer ◽  
Cell Sheet ◽  
Two Dimensional ◽  
Cellular Potts Model ◽  
Epithelial Cell Layer

We use a two-dimensional cellular Potts model to represent the behavior of an epithelial cell layer and describe its dynamics in response to a microscopic wound.

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