CFD SIMULATION OF SHEAR STRESS AND SECONDARY FLOWS IN URETHRA

2007 ◽  
Vol 19 (02) ◽  
pp. 117-127 ◽  
Author(s):  
Yang-Yao Niu ◽  
Ding-Yu Chang
Keyword(s):  
Shear Stress ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Normal Female ◽  
Urinary System ◽  
Stress Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Peak Value ◽  
Lower Urinary

In this work, a preliminary numerical simulation of the lower urinary system using Computational Fluid Dynamics (CFD) is performed. Very few studies have been done on the simulation of three-dimensional urine through the lower urinary system. In this study, a simplified lower urinary model with rigid body assumption is proposed. The distributions of urine flow velocity, wall pressure and shear stress along the urethra are simulated based on MRI scanned uroflowmetry of a normal female. Numerical results show that violent secondary flows appear on the cross surface near the end of the urethra when the inflow rate is increased. The oscillative variation of pressure and shear stress distributions are found around the beginning section of the urethra when flow rate is at the peak value.

The simulation of single wraparound fin on a semi-cylindrical missile body

2020 ◽  
Vol 92 (3) ◽  
pp. 418-427 ◽  
Author(s):  
Nayhel Sharma ◽  
Rakesh Kumar
Keyword(s):  
Research Study ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Future Research ◽  
Aerodynamic Coefficients ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Predicted Values ◽  
Characteristic Trend ◽  
Practical Implications

Purpose The purpose of this paper is to establish a freestream computational fluid dynamics (CFD) model of a three-dimensional non-spinning semi-cylindrical missile model with a single wrap around fin in Mach 2.70-3.00M range and 0° angle of attack, and ultimately establishing itself for future research study. Design/methodology/approach In this study, the behaviour of flow around the fin was investigated using a κ-ϵ turbulence model of second-order of discretization. This was done using a highly structured mesh. Additionally, an inviscid CFD simulation involving the same boundary conditions have also been carried out for comparison. Findings The obtained values of aerodynamic coefficients and pressure contours visualizations are compared against their experimental and computational counterparts. A typical missile aerodynamic characteristic trend can be seen in the current CFD. Practical implications The predicted values of the aerodynamic coefficients of this single fin model have also been compared to those of the full missile body comprising of four fins from the previous research studies, and a similar aerodynamic trend can be seen. Originality/value This study explores the possibility of the use of turbulence modelling in a single fin model of a missile and provides a basic computational model for further understanding the flow behaviour near the fin.

Transient CFD Visualization of Fossil Fuel Combustion Simulations

2003 ◽  
Author(s):  
Brian Dotson ◽  
Kent Eshenberg ◽  
Chris Guenther ◽  
Thomas O’Brien
Keyword(s):  
Power Plants ◽  
High Efficiency ◽  
Cfd Simulation ◽  
Low Cost ◽  
Three Dimensional ◽  
Cfd Simulations ◽  
Projection System ◽  
Computational Fluid Dynamics Cfd ◽  
High Level ◽  
Wall System

The design of high-efficiency lower-emission coal-fed power plants is facilitated by the extensive use of computational fluid dynamics (CFD) simulations. This paper describes work conducted at the National Energy Technology Laboratory (NETL) and Pittsburgh Supercomputing Center (PSC) to provide an environment for the immersive three-dimensional visualization of CFD simulation results. A low-cost high-resolution projection system has been developed in the visualization lab at NETL. This multi-wall system consists of four projection screens, three of which are tiled into four quadrants. The graphics for the multi-wall system are rendered using a cluster of eight personal computers. A high-level visualization interface named Mavis has also been developed to combine the powerful 3D modules of OpenDX with methods developed at NETL for studying multiphase CFD data. With Python, a completely new OpenDX user interface was built that extends and simplifies the features of a basic graphics library.

scholarly journals CFD simulation of the aeration process and baffle influence in a full-scale commercial flat sheet module

2020 ◽  
Vol 81 (9) ◽  
pp. 2004-2010
Author(s):  
Yingchen Cao ◽  
Bowen Gu ◽  
Alexander Sonnenburg ◽  
Wilhelm Urban
Keyword(s):  
Shear Stress ◽  
Cfd Simulation ◽  
Full Scale ◽  
Membrane Module ◽  
Flat Sheet ◽  
Average Shear ◽  
Computational Fluid Dynamics Cfd ◽  
Membrane Modules ◽  
Aeration Process ◽  
A Minor

Abstract The goal of the present paper is to investigate the aeration process and the enhanced effect of baffles in a full-scale commercial membrane bioreactor (MBR) system configured with a flat sheet (FS) membrane module. Through a computational fluid dynamics (CFD) simulation, two aerated FS membrane modules for full-scale applications with 26 membrane sheets were simulated. The numerical results indicate that the presence of baffles and the distances between the baffle and the outmost membrane sheet have a minor influence on the area-weighted shear stress for full-scale MBRs. In addition, bubble size and the bottom distance between the aerator and membrane bottom do not affect the average shear stress of full-scale FS membrane modules much. However, an increase in air flow rate has a significant effect on the area-weighted shear stress. A large FS membrane module is recommended, as it could achieve the same cleaning effect as the small one with a lower specific aeration demand for membranes.

scholarly journals A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Jürgen Endres ◽  
Markus Kowarschik ◽  
Thomas Redel ◽  
Puneet Sharma ◽  
Viorel Mihalef ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Risk Of Rupture ◽  
Computational Fluid Dynamics Cfd ◽  
Subsequent Comparison

Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.

scholarly journals Developing Pulsatile Flow in a Deployed Coronary Stent

2005 ◽  
Vol 128 (3) ◽  
pp. 347-359 ◽  
Author(s):  
Divakar Rajamohan ◽  
Rupak K. Banerjee ◽  
Lloyd H. Back ◽  
Ashraf A. Ibrahim ◽  
Milind A. Jog
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulsatile Flow ◽  
Thrombus Formation ◽  
Three Dimensional ◽  
Tissue Growth ◽  
Coronary Stent ◽  
Stress Distributions ◽  
Hemodynamic Parameters ◽  
Wall Shear

A major consequence of stent implantation is restenosis that occurs due to neointimal formation. This patho-physiologic process of tissue growth may not be completely eliminated. Recent evidence suggests that there are several factors such as geometry and size of vessel, and stent design that alter hemodynamic parameters, including local wall shear stress distributions, all of which influence the restenosis process. The present three-dimensional analysis of developing pulsatile flow in a deployed coronary stent quantifies hemodynamic parameters and illustrates the changes in local wall shear stress distributions and their impact on restenosis. The present model evaluates the effect of entrance flow, where the stent is placed at the entrance region of a branched coronary artery. Stent geometry showed a complex three-dimensional variation of wall shear stress distributions within the stented region. Higher order of magnitude of wall shear stress of 530dyn∕cm2 is observed on the surface of cross-link intersections at the entrance of the stent. A low positive wall shear stress of 10dyn∕cm2 and a negative wall shear stress of −10dyn∕cm2 are seen at the immediate upstream and downstream regions of strut intersections, respectively. Modified oscillatory shear index is calculated which showed persistent recirculation at the downstream region of each strut intersection. The portions of the vessel where there is low and negative wall shear stress may represent locations of thrombus formation and platelet accumulation. The present results indicate that the immediate downstream regions of strut intersections are areas highly susceptible to restenosis, whereas a high shear stress at the strut intersection may cause platelet activation and free emboli formation.

scholarly journals Performance Assessment of Bladeless Micro-Expanders Using 3D Numerical Simulation

2019 ◽  
Vol 113 ◽  
pp. 03016 ◽  
Author(s):  
Avinash Renuke ◽  
Alberto Traverso ◽  
Matteo Pascenti
Keyword(s):  
Shear Stress ◽  
Cfd Simulation ◽  
Numerical Data ◽  
Flow Density ◽  
Cfd Analysis ◽  
Mixing Zone ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
First Time

This paper summarizes the development of fully 3D Computational Fluid Dynamics (CFD) analysis for bladeless air micro expander for 200 W and 3 kW rated power. Modelling of nozzle along with rotor is done using structured mesh. This analysis, for the first time, demonstrates the interaction between nozzle and rotor using compressible flow density-based solver. The Shear Stress Transport (SST) turbulence model is employed to resolve wall effects on the rotor and to determine the shear stress accurately. The results illustrate the flow field inside stator and rotor along with complicated mixing zone between stator and rotor. The comparison of rotor-stator CFD simulation results is done with experiments to preliminary validate the model. The losses in the turbine are discussed with the help of experimental and numerical data.

Numerical Study on the Geometric and Inertial Parameters for Oscillating Wave Surge Converters

2018 ◽  
Author(s):  
Chen-Chou Lin ◽  
Yi-Chih Chow ◽  
Shiaw-Yih Tzang ◽  
Ching-Yen Chiou ◽  
Yu-Yu Huang
Keyword(s):  
Numerical Study ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Wave Climate ◽  
Absorption Efficiency ◽  
Irregular Waves ◽  
Inertial Parameters ◽  
Flap Thickness ◽  
Computational Fluid Dynamics Cfd ◽  
Peak Value

In this paper the three-dimensional numerical simulation is conducted for Oscillating Wave Surge Converters (OWSCs) using computational fluid dynamics (CFD) software FLOW-3D, based on the wave climate of the offshore sea in northeast Taiwan, that is, 1.5 meters of wave height and 7 seconds of the wave period. The results are compared with that using the wave energy converter simulation toolbox, WEC-Sim. The effects of the parameters, including the flap thickness, flap width, the position of the mass center, and flap density, are investigated, especially their influence of the energy capturing efficiency or the capture factor (CF). The simulation results show that, bigger flap thickness (d), smaller flap width (B), smaller flap density, and lower flap’s center of mass will result in a higher efficiency for power capture performance. Among the four parameters, the flap thickness is the most dominant parameter. From hydrodynamic respect, a larger drag force may occur at the sidewalls of the thick flap, and the shear force accelerate the pitch motion of the flap, in turn increasing the absorption efficiency. From a practical design aspect, the variation of the CF around the peak value is smoother for wider flap, which suggests a broad bandwidth in receiving various wave frequency in irregular waves.

Modelling of three-dimensional flow velocities in a deep hole in the East Channel of the Mackenzie Delta, Northwest Territories

2007 ◽  
Vol 34 (10) ◽  
pp. 1312-1323 ◽  
Author(s):  
Bahram Gharabaghi ◽  
Chris Inkratas ◽  
Spyros Beltaos ◽  
Bommanna Krishnappan
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Bed Shear Stress ◽  
Mackenzie Delta ◽  
Stress Distributions ◽  
Deep Hole ◽  
Flow Conditions ◽  
Scour Hole ◽  
Scour Holes ◽  
The Stability

The Mackenzie River has several anomalous deep scour holes in a number of river channels in its delta. Proposed gas pipeline crossings have renewed interest in studying the stability of these scour holes. The main goal of this research project was to study flow velocity and bed shear stress distributions for a 30 m deep hole in the East Channel of the Mackenzie Delta as a first step toward assessing the stability of the scour hole and the risk of its migration during various flow conditions. In this study, a three-dimensional (3D) finite element flow model, FLUENT, using the renormalization group (RNG) k-ε turbulence model (where k is the turbulent kinetic energy and ε is the turbulence dissipation rate) was set up for the scour hole and calibrated using detailed measurements of 3D flow velocities, obtained with an acoustic doppler current profiler. The numerical model was then applied to predict flow velocity and bed shear stress distributions in and around the scour hole for three flow conditions (720, 1000, and 1400 m3/s). Results indicate that two vortices are formed in the river elbow above the scour hole. As the flow rate changed, the sizes of the vortices varied. The region upstream of the hole experienced the greatest magnitudes of bed shear stress.Key words: computational fluid dynamics, finite element, bed shear stress, deep hole, flow reversal.

Optimization of CFD Meshing for Stented Vessel Geometries

2014 ◽  
Vol 553 ◽  
pp. 373-378 ◽  
Author(s):  
Azadeh Lotfi ◽  
Tracie J. Barber
Keyword(s):  
Cfd Simulation ◽  
Computational Cost ◽  
Three Dimensional ◽  
Coronary Bifurcation ◽  
Cfd Simulations ◽  
Coronary Stent Implantation ◽  
Bifurcation Stenting ◽  
Computational Fluid Dynamics Cfd ◽  
Blood Flow Patterns ◽  
High Computational Cost

Coronary stent implantation is the most widely used technique currently employed to treat atherosclerosis in coronary artery. Although the optimal technique for bifurcation stenting in terms of clinical outcome is still open to controversy, most previous studies have focused on the single-stenting techniques due to its simpler geometry and easier clinical implantation. While the biomedical environment in a stented coronary bifurcation is extremely challenging to model, Computational Fluid Dynamics (CFD) investigations have been used to study the effect of stent on blood flow patterns, however, in CFD simulation of double-stenting techniques, the presence of two or more stents accentuates the complexity of the geometry and the associated meshes especially in the region where two or multiple stent layers come together. Hence, in this study, complex three-dimensional geometric CFD simulations of a stented vessel have been performed in order to adopt an efficient and optimal meshing method to reduce the high computational cost. In doing so, several meshing strategies were chosen and applied.

scholarly journals CFD Simulation of Knock Onset in a Heavy-Duty Spark Ignition Gas Engine

2019 ◽  
Vol 8 (4) ◽  
pp. 9585-9593
Keyword(s):  
Fluid Dynamics ◽  
Numerical Model ◽  
Cfd Simulation ◽  
Combustion Process ◽  
Three Dimensional ◽  
Spark Ignition ◽  
Heavy Duty ◽  
Gas Engine ◽  
Optimization Study ◽  
Computational Fluid Dynamics Cfd

The paper describes a method for evaluating knocking onset with computational fluid dynamics (CFD) numerical model of the combustion process of spark ignited (SI) gas engine and methods for assessing the probability of knocking combustion based on this model. The probability of knocking combustion, which characterizes the boundary condition between normal combustion and knocking, is determined (8%). An optimization study of the influence of adjustment parameters on the probability of knocking based on a three-dimensional numerical model is carried out. The developed and tested technique allows one to monitor the tendency of the influence of various adjustment parameters on the probability of knocking in a SI gas engine.

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