Modeling Transition to Turbulence in Eccentric Stenotic Flows

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Sonu S. Varghese ◽  
Steven H. Frankel ◽  
Paul F. Fischer
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Turbulence Models ◽  
Transition To Turbulence ◽  
Mean Flow ◽  
Poor Agreement ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Simulation Results

Mean flow predictions obtained from a host of turbulence models were found to be in poor agreement with recent direct numerical simulation results for turbulent flow distal to an idealized eccentric stenosis. Many of the widely used turbulence models, including a large eddy simulation model, were unable to accurately capture the poststenotic transition to turbulence. The results suggest that efforts toward developing more accurate turbulence models for low-Reynolds number, separated transitional flows are necessary before such models can be used confidently under hemodynamic conditions where turbulence may develop.

scholarly journals Investigation of the velocity field downstream of a benchmark vent using numerical simulation and hot-wire anemometry

2019 ◽  
Vol 213 ◽  
pp. 02076
Author(s):  
Jan Sip ◽  
Frantisek Lizal ◽  
Jakub Elcner ◽  
Jan Pokorny ◽  
Miroslav Jicha
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Velocity Field ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulence Models ◽  
Hot Wire ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Precise Prediction

The velocity field in the area behind the automotive vent was measured by hot-wire anenemometry in detail and intensity of turbulence was calculated. Numerical simulation of the same flow field was performed using Computational fluid dynamics in commecial software STAR-CCM+. Several turbulence models were tested and compared with Large Eddy Simulation. The influence of turbulence model on the results of air flow from the vent was investigated. The comparison of simulations and experimental results showed that most precise prediction of flow field was provided by Spalart-Allmaras model. Large eddy simulation did not provide results in quality that would compensate for the increased computing cost.

A Dynamic Time Filtering Technique for Hybrid RANS-LES Simulation of Non-Stationary Turbulent Flow

2019 ◽  
Author(s):  
Tausif Jamal ◽  
D. Keith Walters
Keyword(s):  
Large Eddy Simulation ◽  
Comprehensive Evaluation ◽  
Model Performance ◽  
Turbulence Models ◽  
Mean Flow ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Filtering Technique ◽  
Dynamic Time

Abstract Unsteady turbulent wall bounded flows can produce complex flow physics including temporally varying mean pressure gradients, intermittent regions of high turbulence intensity, and interaction of different scales of motion. As a representative example, pulsating channel flow presents significant challenges for newly developed and existing turbulence models in computational fluid dynamics (CFD) simulations. The present study investigates the performance of the Dynamic Hybrid RANS-LES (DHRL) model with a newly proposed dynamic time filtering (DTF) technique, compared against an industry standard Reynolds-Averaged Navier-Stokes (RANS) model, Monotonically Integrated Large Eddy Simulation (MILES), and two conventional Hybrid RANS-LES (HRL) models. Model performance is evaluated based on comparison to previously documented Large Eddy Simulation (LES) results. Simulations are performed for a fully developed flow in a channel with time-periodic driving pressure gradient. Results highlight the relative merits of each model type and indicate that the use of a dynamic time filtering technique improves the accuracy of the DHRL model when compared to a static time filtering technique. A comprehensive evaluation of the results suggests that the DHRL-DTF method provides the most consistently accurate reproduction of the time-dependent mean flow characteristics for all models investigated.

Dissipation in Implicit Turbulence Models: A Computational Study

2003 ◽  
Author(s):  
L. G. Margolin ◽  
P. K. Smolarkiewicz ◽  
A. A. Wyszogrodzki
Keyword(s):  
Numerical Simulation ◽  
Preliminary Analysis ◽  
High Reynolds Number ◽  
Computational Study ◽  
Turbulence Models ◽  
Finite Volume Methods ◽  
Data Set ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

We describe a series of computational experiments that employ nonoscillatory finite volume methods to simulate the decay of high Reynolds number turbulence. These experiments cover a broad range of physical viscosities and numerical resolutions. We have extracted a data set from these experiments detailing the energy dissipation by physical viscosity and by the numerical algorithm. We offer a preliminary analysis of this data, including new insights into the (computational) transition between direct numerical simulation and large eddy simulation.

The Germano Large Eddy Simulation Model Used for the Simulation of Separated Flow

2003 ◽  
Author(s):  
Engin Cetindogan ◽  
Govert de With ◽  
Arne E. Holdo̸
Keyword(s):  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Computational Study ◽  
Separated Flow ◽  
Local Flow ◽  
Large Eddy Simulation Model ◽  
Slip Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

A computational study of unsteady, separated fluid flow was made using the Large Eddy Simulation (LES). As flow problem the turbulent flow past a circular cylinder at a Reynolds number of Re = 3900 was chosen. The objective of this work was to study the numerical and modelling aspects of the dynamic Germano-LES turbulence model. Before LES can be used for applications of practical relevance, such as the flow around a complete aircraft or automobile, extensive tests must be carried out on simpler configurations to understand the quality of LES. Also, the influence of different grid resolutions was examined. Due to the fact of a low Reynolds number, no-slip boundary conditions were used at solid walls. Two different subgrid scale models were applied. In recent years several simulations were carried out using the Smagorinsky-LES model but there is still a lack of experience using the dynamic Germano-LES model, which takes the local flow parameters into account. Several simulations with different parameters and grid-models were carried out both with the Germano-LES model and the Smagorinsky-LES model. Comparisons were made between these two models as well as with several experimental data taken from literature.

Dissipation in Implicit Turbulence Models: A Computational Study

2006 ◽  
Vol 73 (3) ◽  
pp. 469-473 ◽  
Author(s):  
L. G. Margolin ◽  
P. K. Smolarkiewicz ◽  
A. A. Wyszogradzki
Keyword(s):  
Numerical Simulation ◽  
Preliminary Analysis ◽  
High Reynolds Number ◽  
Computational Study ◽  
Turbulence Models ◽  
Finite Volume Methods ◽  
Data Set ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

We describe a series of computational experiments that employ nonoscillatory finite volume methods to simulate the decay of high Reynolds number turbulence. These experiments cover a broad range of physical viscosities and numerical resolutions. We have extracted a data set from these experiments detailing the energy dissipation by physical viscosity and by the numerical algorithm. We offer a preliminary analysis of this data, including new insights into the (computational) transition between direct numerical simulation and large eddy simulation.

Application of Large-Eddy Simulation to the Study of Pulsatile Flow in a Modeled Arterial Stenosis

2001 ◽  
Vol 123 (4) ◽  
pp. 325-332 ◽  
Author(s):  
R. Mittal ◽  
S. P. Simmons ◽  
H. S. Udaykumar
Keyword(s):  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Pulsatile Flow ◽  
Arterial Stenosis ◽  
Transition To Turbulence ◽  
Frequency Spectra ◽  
Potential Implication ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Physical Features

The technique of large-eddy simulation (LES) has been applied to the study of pulsatile flow through a modeled arterial stenosis. A simple stenosis model has been used that consists of a one-sided 50 percent semicircular constriction in a planar channel. The inlet volume flux is varied sinusoidally in time in a manner similar to the laminar flow simulations of Tutty (1992). LES is used to compute flow at a peak Reynolds number of 2000 and a Strouhal number of 0.024. At this Reynolds number, the flow downstream of the stenosis transitions to turbulence and exhibits all the classic features of post-stenotic flow as described by Khalifa and Giddens (1981) and Lieber and Giddens (1990). These include the periodic shedding of shear layer vortices and transition to turbulence downstream of the stenosis. Computed frequency spectra indicate that the vortex shedding occurs at a distinct high frequency, and the potential implication of this for noninvasive diagnosis of arterial stenoses is discussed. A variety of statistics have been also extracted and a number of other physical features of the flow are described in order to demonstrate the usefulness of LES for the study of post-stenotic flows.

Very Large Eddy Simulation (VLES) of a Squealer Tipped Axial Turbine Stage

2017 ◽  
Author(s):  
Ryan Kelly ◽  
Aleksandar Jemcov ◽  
Joshua D. Cameron ◽  
Scott C. Morris ◽  
Jesse Coffman ◽  
...  
Keyword(s):  
Performance Prediction ◽  
Turbulence Models ◽  
Aerodynamic Design ◽  
Turbine Stage ◽  
Axial Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Simulation Results ◽  
Improved Performance ◽  
The University

This work presents numerical simulation results of a single stage axial turbine consisting of a nozzle and squealer tipped rotor. The VLES method is a hybrid URANS/LES method based on the standard k-ω SST and Coherent Structure LES turbulence models. The simulations were performed at the stage aerodynamic design point (ADP) and the results were validated against high-quality steady experimental data acquired at the University of Notre Dame’s axial transonic research turbine (TRT) facility. Along with the experimental validation, the VLES simulation results were further compared to those predicted using URANS highlighting the benefits of VLES compared to traditional predictive methods. All simulations were performed using a RANS-type grid density to highlight the efficiency of the VLES method and improved performance prediction.

Numerical simulation of the wake of a towed sphere in a weakly stratified fluid

2002 ◽  
Vol 473 ◽  
pp. 83-101 ◽  
Author(s):  
DOUGLAS G. DOMMERMUTH ◽  
JAMES W. ROTTMAN ◽  
GEORGE E. INNIS ◽  
EVGENY A. NOVIKOV
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Iterative Procedure ◽  
Laboratory Experiments ◽  
Stratified Fluid ◽  
Eddy Simulation ◽  
Lower Reynolds Number ◽  
Large Eddy ◽  
Initial Turbulence

We present some preliminary results from using large-eddy simulation to compute the late wake of a sphere towed at constant speed through a non-stratified and a uniformly stratified fluid. The wake is computed in each case for two values of the Reynolds number: Re = 104, which is comparable to that used in laboratory experiments, and Re = 105. An important aspect of the simulation is the use of an iterative procedure to relax the initial turbulence field so that the normal and shear turbulent stresses are properly correlated and the turbulent production and dissipation are in equilibrium. For the lower Reynolds number our results compare well with existing laboratory experimental results. For the higher Reynolds number we find that even though the turbulence is more developed and the wake contains finer structure, most of the similarity properties of the wake are unchanged compared with those observed at the lower Reynolds number.

Sign in / Sign up

Export Citation Format

Share Document