Comparison of particle-resolved DNS (PR-DNS) and non-resolved DEM/CFD simulations of flow through homogenous ensembles of fixed spherical and non‐spherical particles

2021 ◽  
Author(s):  
B. Kravets ◽  
D. Schulz ◽  
R. Jasevičius ◽  
S.R. Reinecke ◽  
T. Rosemann ◽  
...  
Keyword(s):  
Spherical Particles ◽  
Cfd Simulations ◽  
Flow Through

Formation of Hexagonal Monolayers by Flow of Bead Suspensions Into Flat Microchambers

2003 ◽  
Author(s):  
Markus Grumann ◽  
Patric Schippers ◽  
Michael Dobmeier ◽  
Stefan Ha¨berle ◽  
Andreas Geipel ◽  
...  
Keyword(s):  
Hydrodynamic Resistance ◽  
Inlet Channel ◽  
Cfd Simulations ◽  
Outlet Channel ◽  
Bead Diameter ◽  
Flow Through ◽  
Bioanalytical Assays ◽  
Pressure Driven Flow ◽  
Complete Process ◽  
Microfluidic Structure

To realize a highly parallel optical detection in bead-based bioanalytical assays, we investigate the hydrodynamic aggregation of bead suspensions in a hexagonally periodical monolayer by a pressure-driven flow through a microfluidic structure. This device consists of one inlet channel connected to a shallow chamber with a depth that only slightly exceeds the diameter of the beads. To enforce the aggregation of the beads, the flow leaves the chamber via outlet channels possessing a depth smaller than a bead diameter. This way the outlets act as barriers to the beads and force them to accumulate in the chamber. Benchmarking different chamber and outlet designs we found an optimum filing behavior for a rhombus-like aggregation chamber connected to a single outlet channel at the same width as the chamber. Here, the aperture angle of 60° fosters hexagonal aggregation patterns which leads to the highest packaging density. Reproducible filling ratios of more than 94% have been achieved. The rhombus-like chamber also shows the shows the smallest increase of the hydrodynamic resistance during filling and the best rinsing behavior which allows to minimize the volume of washing detergents used for a bioassay. Zones of accumulated beads redistribute the hydrodynamic flow through the device during the filling process. CFD-simulations, embedded in an iterative master-routine, are carried out to describe the complete process of filling and to assist the process of design optimization.

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.

Viscous flow in a cylindrical tube containing a line of spherical particles

1969 ◽  
Vol 38 (1) ◽  
pp. 75-96 ◽  
Author(s):  
Henry Wang ◽  
Richard Skalak
Keyword(s):  
Pressure Drop ◽  
Cylindrical Tube ◽  
Tube Diameter ◽  
Creeping Flow ◽  
Spherical Particles ◽  
Sphere Diameter ◽  
Wide Range ◽  
Mean Pressure ◽  
Order Of Magnitude ◽  
Flow Through

The viscous, creeping flow through a cylindrical tube of a liquid, which contains rigid, spherical particles, is investigated analytically. The spheres are located on the axis of the cylinder and are equally spaced. Solutions are derived for particles in motion and fixed, with and without fluid discharge. Numerical results are presented for the drag on each sphere and the mean pressure drop for a wide range of sizes and spacings of the spheres. The study is motivated by possible application to blood flow in capillaries, where red blood cells represent particles of the same order of magnitude as the diameter of the capillary itself. The results may also be of interest in other applications, such as sedimentation and fluidized beds. It is shown that there is little interaction between particles if the spacing is more than one tube diameter, and that the additional pressure drop over that for Poiseuille flow is less than 50% if the sphere diameter is less than 0·8 of the tube diameter.

Flow in a Mechanical Bileaflet Heart Valve at Laminar and Near-Peak Systole Flow Rates: CFD Simulations and Experiments

2005 ◽  
Vol 127 (5) ◽  
pp. 782-797 ◽  
Author(s):  
Liang Ge ◽  
Hwa-Liang Leo ◽  
Fotis Sotiropoulos ◽  
Ajit P. Yoganathan
Keyword(s):  
Heart Valve ◽  
Turbulence Modeling ◽  
Mechanical Heart Valve ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Flow Through

Time-accurate, fully 3D numerical simulations and particle image velocity laboratory experiments are carried out for flow through a fully open bileaflet mechanical heart valve under steady (nonpulsatile) inflow conditions. Flows at two different Reynolds numbers, one in the laminar regime and the other turbulent (near-peak systole flow rate), are investigated. A direct numerical simulation is carried out for the laminar flow case while the turbulent flow is investigated with two different unsteady statistical turbulence modeling approaches, unsteady Reynolds-averaged Navier-Stokes (URANS) and detached-eddy simulation (DES) approach. For both the laminar and turbulent cases the computed mean velocity profiles are in good overall agreement with the measurements. For the turbulent simulations, however, the comparisons with the measurements demonstrate clearly the superiority of the DES approach and underscore its potential as a powerful modeling tool of cardiovascular flows at physiological conditions. The study reveals numerous previously unknown features of the flow.

scholarly journals Numerical and experimental models applied to an ogee crest spillway and roller bucket stilling basin

RBRH ◽  
2020 ◽  
Vol 25 ◽  
Author(s):  
Vitor Hugo Pereira de Morais ◽  
Tiago Zenker Gireli ◽  
Paulo Vatavuk
Keyword(s):  
Experimental Models ◽  
Physical Models ◽  
Cfd Simulations ◽  
Stilling Basin ◽  
Stilling Basins ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Scale Experiment ◽  
Reduced Scale ◽  
Numerical Modeling Of Flows

ABSTRACT Traditionally, reduced physical models are used to allow control, instrumentation and experimental evaluation of flow. More recently, computational fluid dynamics (CFD) has emerged as a tool that allows numerical modeling of flows and can complement the information provided by the physical model. The objective this paper is to validate the CFD tool in reproducing the flow through an ogee crest spillway with a roller bucket stilling basin. This validation was performed with the data from a reduced scale experiment in which measurements were made of the position of the water free surface and of the pressure loads in the spillway profile. It was verified that the CFD tool is suitable for the study of this type of flow, being able to reproduce the experimental results. In the execution of the numerical simulations, special attention was given to the influence of the mesh on the results. An important influence of the mesh was observed in some results, which shows the importance a sensitivity analysis of this parameter when performing CFD simulations. The obtained results offer the prospect of using CFD as a supporting tool for the design of spillways and stilling basins.

scholarly journals Numerical and Experimental Aerodynamic Investigation of an S-Shaped Intermediate Compressor Duct With Bleed

2021 ◽  
pp. 1-16
Author(s):  
Elias Siggeirsson ◽  
Niklas Andersson ◽  
Markus Olander Burak
Keyword(s):  
Integrated Design ◽  
Axial Flow ◽  
Experimental Facility ◽  
Cfd Simulations ◽  
Disturbed Flow ◽  
Operating Condition ◽  
Guide Vanes ◽  
Flow Through ◽  
Engine Systems ◽  
Aerodynamic Investigation

Abstract A series of CFD simulations are performed to analyse the effects a rotor off-take bleed has on the performance of an Intermediate Compressor Duct (ICD). To validate the CFD results, a comparison is made to measurements obtained from an experimental facility located at GKN Aerospace Engine Systems in Sweden. To achieve a deeper understanding of the flow physics, hybrid RANS/LES simulations are performed for a single operating condition. The CFD simulations are capable of predicting the behavior when extracting large amount of air through the bleed pipe, where an improved prediction is obtained with the hybrid simulation. The performance of the ICD is severely compromised with increased amount of bleed as the flow delivered to the downstream component is highly disturbed. The disturbed flow is caused by the extraction of axial flow through the bleed pipe, increasing the incidence into the low-pressure compressor's outlet guide vanes resulting in unfavorable velocity profiles into the ICD. This behavior causes the flow to separate at the OGV blades, where the separation increases with increase bleed. Furthermore, when including the full bleed system, significant circumferential distortions are observed, showing the necessity of the integrated design.

PIV-Measured Versus CFD-Predicted Flow Dynamics in Anatomically Realistic Cerebral Aneurysm Models

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Matthew D. Ford ◽  
Hristo N. Nikolov ◽  
Jaques S. Milner ◽  
Stephen P. Lownie ◽  
Edwin M. DeMont ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Cardiac Cycle ◽  
Flow Dynamics ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations ◽  
Flow Through

Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement between PIV and CFD suggests that CFD can reliably predict the details of the intra-aneurysmal flow dynamics observed in anatomically realistic in vitro models. Nevertheless, given the various modeling assumptions, this does not prove that they are mimicking the actual in vivo hemodynamics, and so validations against in vivo data are encouraged whenever possible.

scholarly journals Force and torque on spherical particles in micro-channel flows using computational fluid dynamics

2016 ◽  
Vol 3 (7) ◽  
pp. 160298 ◽  
Author(s):  
Jin Suo ◽  
Erin E. Edwards ◽  
Ananyaveena Anilkumar ◽  
Todd Sulchek ◽  
Don P. Giddens ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cell Adhesion ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Spherical Particles ◽  
Microfluidic Channels ◽  
Cfd Modelling ◽  
Cfd Simulations ◽  
Hemodynamic Force

To delineate the influence of hemodynamic force on cell adhesion processes, model in vitro fluidic assays that mimic physiological conditions are commonly employed. Herein, we offer a framework for solution of the three-dimensional Navier–Stokes equations using computational fluid dynamics (CFD) to estimate the forces resulting from fluid flow near a plane acting on a sphere that is either stationary or in free flow, and we compare these results to a widely used theoretical model that assumes Stokes flow with a constant shear rate. We find that while the full three-dimensional solutions using a parabolic velocity profile in CFD simulations yield similar translational velocities to those predicted by the theoretical method, the CFD approach results in approximately 50% larger rotational velocities over the wall shear stress range of 0.1–5.0 dynes cm −2 . This leads to an approximately 25% difference in force and torque calculations between the two methods. When compared with experimental measurements of translational and rotational velocities of microspheres or cells perfused in microfluidic channels, the CFD simulations yield significantly less error. We propose that CFD modelling can provide better estimations of hemodynamic force levels acting on perfused microspheres and cells in flow fields through microfluidic devices used for cell adhesion dynamics analysis.

Vapor–liquid critical flow through a layer of spherical particles

2016 ◽  
Vol 54 (2) ◽  
pp. 261-269 ◽  
Author(s):  
E. A. Tairov ◽  
B. G. Pokusaev ◽  
S. M. Bykova
Keyword(s):  
Spherical Particles ◽  
Critical Flow ◽  
Flow Through ◽  
Vapor Liquid
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