Oscillating Turbulent Flow With or Without a Current About a Circular Cylinder

1997 ◽  
Vol 119 (2) ◽  
pp. 73-78 ◽  
Author(s):  
T. Sarpkaya ◽  
M. de Angelis ◽  
C. Hanson
Keyword(s):  
Turbulent Flows ◽  
Large Scale ◽  
Turbulence Models ◽  
Second Order ◽  
Time Dependent ◽  
Navier Stokes ◽  
Computational Accuracy ◽  
Pressure Distributions ◽  
Cfd Analyses ◽  
Predictor Corrector

CFD analyses of two benchmark, two-dimensional, sinusoidally oscillating, turbulent flows (one with zero mean and one with nonzero mean) at relatively large Reynolds and Keulegan-Carpenter numbers and relative current velocities, have been performed with CFD-ACE, a Favre-averaged Navier-Stokes (FANS) code. The primary purpose of the investigation was a critical assessment of the computational accuracy of time-dependent turbulent flows with large-scale unsteadiness. A number of turbulence models, including the standard k-ε, re-normalization group (RNG) based k-ε, and low-Reynolds number model have been employed. Among others, a second order in time, second order in space, second-level predictor-corrector finite-difference scheme has been used. The analysis produced the time-dependent in-line and transverse forces, the force coefficients, instantaneous velocity, vorticity, and pressure distributions, and streamlines. Representative results are compared with each other and with those obtained experimentally.

Comparison of Experimental and RANS-Based Numerical Studies of the Decay of Grid-Generated Turbulence

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Ivan Torrano ◽  
Mustafa Tutar ◽  
Manex Martinez-Agirre ◽  
Anthony Rouquier ◽  
Nicolas Mordant ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Large Scale ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Numerical Studies ◽  
Turbulence Decay ◽  
Moderate Reynolds Number ◽  
Scale Properties

This paper presents both experimental and numerical studies of the statistical properties of turbulent flows at moderate Reynolds number (Reλ = 100) in the context of grid-generated turbulence. In spite of the popularity of passive grids as turbulence generators, their design relies essentially on empirical laws. Here, we propose to test the ability of simple numerical simulations to capture the large scale properties (root-mean-square (rms) velocity, turbulence decay, pressure drop, etc.) of the turbulence downstream a passive grid. With this purpose, experimental measurements are compared with the three-dimensional (3D) Reynolds-Averaged Navier–Stokes (RANS) equations based turbulence model simulations. To better modeling of energy cascade of turbulence, different turbulence models, mesh resolutions, and turbulence model constants, which are determined in accordance with the experimentally measured corresponding values, are used. Both qualitative and quantitative comparisons are made with the experimental data to further assess the accuracy and capability of present numerical techniques for their use in different aerodynamic applications at moderate Re number.

scholarly journals Assessment of Numerical Methods for Plunging Breaking Wave Predictions

2021 ◽  
Vol 9 (3) ◽  
pp. 264
Author(s):  
Shanti Bhushan ◽  
Oumnia El Fajri ◽  
Graham Hubbard ◽  
Bradley Chambers ◽  
Christopher Kees
Keyword(s):  
Solitary Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Wave Crest ◽  
Breaking Wave ◽  
Rans Turbulence Models ◽  
Run Up ◽  
Better Than

This study evaluates the capability of Navier–Stokes solvers in predicting forward and backward plunging breaking, including assessment of the effect of grid resolution, turbulence model, and VoF, CLSVoF interface models on predictions. For this purpose, 2D simulations are performed for four test cases: dam break, solitary wave run up on a slope, flow over a submerged bump, and solitary wave over a submerged rectangular obstacle. Plunging wave breaking involves high wave crest, plunger formation, and splash up, followed by second plunger, and chaotic water motions. Coarser grids reasonably predict the wave breaking features, but finer grids are required for accurate prediction of the splash up events. However, instabilities are triggered at the air–water interface (primarily for the air flow) on very fine grids, which induces surface peel-off or kinks and roll-up of the plunger tips. Reynolds averaged Navier–Stokes (RANS) turbulence models result in high eddy-viscosity in the air–water region which decays the fluid momentum and adversely affects the predictions. Both VoF and CLSVoF methods predict the large-scale plunging breaking characteristics well; however, they vary in the prediction of the finer details. The CLSVoF solver predicts the splash-up event and secondary plunger better than the VoF solver; however, the latter predicts the plunger shape better than the former for the solitary wave run-up on a slope case.

Numerical Simulation of Turbulent Flows in Ribbed Pipes

2005 ◽  
Author(s):  
Sowjanya Vijiapurapu ◽  
Jie Cui
Keyword(s):  
Turbulent Flows ◽  
Turbulence Models ◽  
Numerical Data ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Friction Resistance ◽  
Circular Pipes ◽  
Computational Fluid Dynamics Cfd ◽  
Stress Models ◽  
Type Intermediate

The Reynolds averaged Navier-Stokes (RANS) equations were solved along with three turbulence models, namely κ-ε, κ-ω, and Reynolds stress models (RSM), to study the fully developed turbulent flows in circular pipes roughened by repeated square ribs. The spacing between the ribs was varied to form three representative types of surface roughness; d–type, intermediate, and k–type. Solutions of these flows at two Reynolds numbers were obtained using the commercial computational fluid dynamics (CFD) software Fluent. The numerical results were validated against experimental measurements and other numerical data published in literature. Extensive investigation of effects of rib spacing and Reynolds number on the pressure and friction resistance, flow and turbulence distribution was presented. The performance of three turbulence models was also compared and discussed.

scholarly journals On the analysis of a geometrically selective turbulence model

2020 ◽  
Vol 9 (1) ◽  
pp. 1402-1419 ◽  
Author(s):  
Nejmeddine Chorfi ◽  
Mohamed Abdelwahed ◽  
Luigi C. Berselli
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Large Scale ◽  
Stokes Equations ◽  
A Priori ◽  
Strong Solutions ◽  
Navier Stokes ◽  
Smagorinsky Model ◽  
Navier Stokes Equations ◽  
Velocity Pressure

Abstract In this paper we propose some new non-uniformly-elliptic/damping regularizations of the Navier-Stokes equations, with particular emphasis on the behavior of the vorticity. We consider regularized systems which are inspired by the Baldwin-Lomax and by the selective Smagorinsky model based on vorticity angles, and which can be interpreted as Large Scale methods for turbulent flows. We consider damping terms which are active at the level of the vorticity. We prove the main a priori estimates and compactness results which are needed to show existence of weak and/or strong solutions, both in velocity/pressure and velocity/vorticity formulation for various systems. We start with variants of the known ones, going later on to analyze the new proposed models.

Multigrid Computation of Incompressible Flows Using Two-Equation Turbulence Models: Part II—Applications

1997 ◽  
Vol 119 (4) ◽  
pp. 900-905 ◽  
Author(s):  
X. Zheng ◽  
C. Liao ◽  
C. Liu ◽  
C. H. Sung ◽  
T. T. Huang
Keyword(s):  
Turbulent Flows ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Grid Algorithm ◽  
High Reynolds

In this paper, computational results are presented for three-dimensional high-Reynolds number turbulent flows over a simplified submarine model. The simulation is based on the solution of Reynolds-Averaged Navier-Stokes equations and two-equation turbulence models by using a preconditioned time-stepping approach. A multiblock method, in which the block loop is placed in the inner cycle of a multi-grid algorithm, is used to obtain versatility and efficiency. It was found that the calculated body drag, lift, side force coefficients and moments at various angles of attack or angles of drift are in excellent agreement with experimental data. Fast convergence has been achieved for all the cases with large angles of attack and with modest drift angles.

Studying turbulence using direct numerical simulation: 1987 Center for Turbulence Research NASA Ames/Stanford Summer Programme

1988 ◽  
Vol 190 ◽  
pp. 375-392 ◽  
Author(s):  
J. C. R. Hunt
Keyword(s):  
Boundary Layers ◽  
Turbulent Flows ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Stokes Equations ◽  
Turbulent Boundary Layers ◽  
Finite Amplitude ◽  
Wall Layer ◽  
Navier Stokes ◽  
Scale Motion

This paper is an account of a summer programme for the study of the ideas and models of turbulent flows, using the results of direct numerical stimulations of the Navier-Stokes equations. These results had been obtained on the computers and stored as accessible databases at the Center for Turbulence Research (CTR) of NASA Ames Research Center and Stanford University. At this first summer programme, some 32 visiting researchers joined those at the CTR to test hypotheses and models in five aspects of turbulence research: turbulence decomposition, bifurcation and chaos; two-point closure (or k-space) modelling; structure of turbulent boundary layers; Reynolds-stress modelling; scalar transport and reacting flows.A number of new results emerged including: computation of space and space-time correlations in isotropic turbulence can be related to each other and modelled in terms of the advection of small scales by large-scale motion; the wall layer in turbulent boundary layers is dominated by shear layers which protrude into the outer layers, and have long lifetimes; some aspects of the ejection mechanism for these layers can be described in terms of the two-dimensional finite-amplitude Navier-Stokes solutions; a self-similar form of the two-point, cross-correlation data of the turbulence in boundary layers (when normalized by the r.m.s. value at the furthest point from the wall) shows how both the blocking of eddies by the wall and straining by the mean shear control the lengthscales; the intercomponent transfer (pressure-strain) is highly localized in space, usually in regions of concentrated vorticity; conditioned pressure gradients are linear in the conditioning of velocity and independent of vorticity in homogeneous shear flow; some features of coherent structures in the boundary layer are similar to experimental measurements of structures in mixing-layers, jets and wakes.The availability of comprehensive velocity and pressure data certainly helps the investigation of concepts and models. But a striking feature of the summer programme was the diversity of interpretation of the same computed velocity fields. There are few signs of any convergence in turbulence research! But with new computational facilities the divergent approaches can at least be related to each other.

scholarly journals A numerical model for the time-dependent wake of a pedalling cyclist

2019 ◽  
Vol 233 (4) ◽  
pp. 514-525
Author(s):  
Martin D Griffith ◽  
Timothy N Crouch ◽  
David Burton ◽  
John Sheridan ◽  
Nicholas AT Brown ◽  
...  
Keyword(s):  
Drag Force ◽  
Large Scale ◽  
Aerodynamic Drag ◽  
Experimental Studies ◽  
Wake Flow ◽  
Time Dependent ◽  
Navier Stokes ◽  
Streamwise Vorticity ◽  
Leg Cycling ◽  
The Impact

A method for computing the wake of a pedalling cyclist is detailed and assessed through comparison with experimental studies. The large-scale time-dependent turbulent flow is simulated using the Scale Adaptive Simulation approach based on the Shear Stress Transport Reynolds-averaged Navier–Stokes model. Importantly, the motion of the legs is modelled by joining the model at the hips and knees and imposing solid body rotation and translation to the lower and upper legs. Rapid distortion of the cyclist geometry during pedalling requires frequent interpolation of the flow solution onto new meshes. The impact of numerical errors, that are inherent to this remeshing technique, on the computed aerodynamic drag force is assessed. The dynamic leg simulation was successful in reproducing the oscillation in the drag force experienced by a rider over the pedalling cycle that results from variations in the large-scale wake flow structure. Aerodynamic drag and streamwise vorticity fields obtained for both static and dynamic leg simulations are compared with similar experimental results across the crank cycle. The new technique presented here for simulating pedalling leg cycling flows offers one pathway for improving the assessment of cycling aerodynamic performance compared to using isolated static leg simulations alone, a practice common in optimising the aerodynamics of cyclists through computational fluid dynamics.

A Methodology for Simulating Compressible Turbulent Flows

2005 ◽  
Vol 73 (3) ◽  
pp. 405-412 ◽  
Author(s):  
Hermann F. Fasel ◽  
Dominic A. von Terzi ◽  
Richard D. Sandberg
Keyword(s):  
Turbulent Flows ◽  
Compressible Flows ◽  
Bluff Body ◽  
Turbulence Modeling ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Fine Grid ◽  
Local Flow

A flow simulation Methodology (FSM) is presented for computing the time-dependent behavior of complex compressible turbulent flows. The development of FSM was initiated in close collaboration with C. Speziale (then at Boston University). The objective of FSM is to provide the proper amount of turbulence modeling for the unresolved scales while directly computing the largest scales. The strategy is implemented by using state-of-the-art turbulence models (as developed for Reynolds averaged Navier-Stokes (RANS)) and scaling of the model terms with a “contribution function.” The contribution function is dependent on the local and instantaneous “physical” resolution in the computation. This physical resolution is determined during the actual simulation by comparing the size of the smallest relevant scales to the local grid size used in the computation. The contribution function is designed such that it provides no modeling if the computation is locally well resolved so that it approaches direct numerical simulations (DNS) in the fine-grid limit and such that it provides modeling of all scales in the coarse-grid limit and thus approaches a RANS calculation. In between these resolution limits, the contribution function adjusts the necessary modeling for the unresolved scales while the larger (resolved) scales are computed as in large eddy simulation (LES). However, FSM is distinctly different from LES in that it allows for a consistent transition between RANS, LES, and DNS within the same simulation depending on the local flow behavior and “physical” resolution. As a consequence, FSM should require considerably fewer grid points for a given calculation than would be necessary for a LES. This conjecture is substantiated by employing FSM to calculate the flow over a backward-facing step and a plane wake behind a bluff body, both at low Mach number, and supersonic axisymmetric wakes. These examples were chosen such that they expose, on the one hand, the inherent difficulties of simulating (physically) complex flows, and, on the other hand, demonstrate the potential of the FSM approach for simulations of turbulent compressible flows for complex geometries.

Sign in / Sign up

Export Citation Format

Share Document