scholarly journals The Effect of Schmidt Number on Turbulent Scalar Mixing in a Jet-in-Crossflow

1999 ◽  
Author(s):  
Guangbin He ◽  
Yanhu Guo ◽  
Andrew T. Hsu ◽  
A. Brankovic ◽  
S. Syed ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Momentum Flux ◽  
Schmidt Number ◽  
Stokes Equations ◽  
Scalar Fields ◽  
Spreading Rate ◽  
Navier Stokes ◽  
Appreciable Effect ◽  
Jet In Crossflow ◽  
Schmidt Numbers

The adequacy and accuracy of the constant Schmidt number assumption in predicting turbulent scalar fields in jet-in-crossflows are assessed in the present work. A round jet injected into a confined crossflow in a rectangular tunnel has been simulated using the Reynolds-Averaged Navier-Stokes equations coupled with the standard k-ε turbulence model. A semi-analytical qualitative analysis was made to guide the selection of Schmidt number values. A series of parametric studies were performed, and Schmidt numbers ranging from 0.2 to 1.5 and jet-to-crossflow momentum flux ratios from 8 to 72 were tested. The principal observation is that the Schmidt number does not have an appreciable effect on the species penetration, but it does have a significant effect on species spreading rate in jet-in-crossflows, especially for the cases where the jet-to-crossflow momentum flux ratios are relatively small. A Schmidt number of 0.2 is recommended for best agreement with data. The limitations of the standard k–ε turbulence model and the constant Schmidt number assumption are discussed.

A Numerical Study on the Turbulent Schmidt Numbers in a Jet in Crossflow

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Elizaveta M. Ivanova ◽  
Berthold E. Noll ◽  
Manfred Aigner
Keyword(s):  
Schmidt Number ◽  
Numerical Study ◽  
Scalar Fields ◽  
Navier Stokes ◽  
Rans Model ◽  
Eddy Simulation ◽  
Jet In Crossflow ◽  
Turbulent Schmidt Number ◽  
Optimal Value ◽  
Schmidt Numbers

This work presents a numerical study on the turbulent Schmidt numbers in jets in crossflow. This study contains two main parts. In the first part, the problem of the proper choice of the turbulent Schmidt number in the Reynolds-averaged Navier-Stokes (RANS) jet in crossflow mixing simulations is outlined. The results of RANS employing the shear-stress transport (SST) model of Menter and its curvature correction modification and different turbulent Schmidt number values are validated against experimental data. The dependence of the optimal value of the turbulent Schmidt number on the dynamic RANS model is studied. Furthermore, a comparison is made with the large-eddy simulation (LES) results obtained using the wall-adapted local eddy viscosity (WALE) model. The accuracy given by LES is superior in comparison to RANS results. This leads to the second part of the current study, in which the time-averaged mean and fluctuating velocity and scalar fields from LES are used for the evaluation of the turbulent viscosities, turbulent scalar diffusivities, and the turbulent Schmidt numbers in a jet in crossflow configuration. The values obtained from the LES data are compared with those given by the RANS modeling. The deviations are discussed, and the possible ways for the RANS model improvements are outlined.

A Numerical Study on the Turbulent Schmidt Numbers in a Jet in Crossflow

2012 ◽  
Author(s):  
Elizaveta Ivanova ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Schmidt Number ◽  
Numerical Study ◽  
Scalar Fields ◽  
Navier Stokes ◽  
Rans Model ◽  
Eddy Simulation ◽  
Eddy Viscosity Model ◽  
Jet In Crossflow ◽  
Turbulent Schmidt Number ◽  
Schmidt Numbers

This work presents a numerical study on the turbulent Schmidt numbers in jets in crossflow. This study contains two main parts. In the first part the problem of the proper choice of the turbulent Schmidt number in the Reynolds-Averaged Navier-Stokes (RANS) jet in crossflow mixing simulations is outlined. The results of RANS employing the shear-stress transport (SST) model of Menter and its curvature correction modification and different turbulent Schmidt number values are validated against experimental data. The dependence of the “optimal” value of the turbulent Schmidt number on the dynamic RANS model is studied. Furthermore a comparison is made with the large-eddy simulation (LES) results obtained using the WALE (Wall-Adapted Local Eddy Viscosity) model. The accuracy given by LES is superior in comparison to RANS results. This leads to the second part of the current study, in which the time-averaged mean and fluctuating velocity and scalar fields from LES are used for the evaluation of the turbulent viscosities, turbulent scalar diffusivities, and the turbulent Schmidt numbers in a jet in crossflow configuration. The values obtained from the LES data are compared with those given by the RANS modeling. The deviations are discussed and the possible ways for the RANS model improvements are outlined.

Simulation of the Transitional Flow in a Low Pressure Gas Turbine Cascade With a High-Order Discontinuous Galerkin Method

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
A. Ghidoni ◽  
A. Colombo ◽  
S. Rebay ◽  
F. Bassi
Keyword(s):  
Discontinuous Galerkin ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Time Integration ◽  
High Order ◽  
Transitional Flow ◽  
Navier Stokes ◽  
Implicit Time ◽  
Turbine Cascade ◽  
High Reynolds

In the last decade, discontinuous Galerkin (DG) methods have been the subject of extensive research efforts because of their excellent performance in the high-order accurate discretization of advection-diffusion problems on general unstructured grids, and are nowadays finding use in several different applications. In this paper, the potential offered by a high-order accurate DG space discretization method with implicit time integration for the solution of the Reynolds-averaged Navier–Stokes equations coupled with the k-ω turbulence model is investigated in the numerical simulation of the turbulent flow through the well-known T106A turbine cascade. The numerical results demonstrate that, by exploiting high order accurate DG schemes, it is possible to compute accurate simulations of this flow on very coarse grids, with both the high-Reynolds and low-Reynolds number versions of the k-ω turbulence model.

scholarly journals Three-Dimensional Turbulent Vortex Shedding From a Surface-Mounted Square Cylinder: Predictions With Large-Eddy Simulations and URANS

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
B. A. Younis ◽  
A. Abrishamchi
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Navier Stokes Equations ◽  
Large Eddy

The paper reports on the prediction of the turbulent flow field around a three-dimensional, surface mounted, square-sectioned cylinder at Reynolds numbers in the range 104–105. The effects of turbulence are accounted for in two different ways: by performing large-eddy simulations (LES) with a Smagorinsky model for the subgrid-scale motions and by solving the unsteady form of the Reynolds-averaged Navier–Stokes equations (URANS) together with a turbulence model to determine the resulting Reynolds stresses. The turbulence model used is a two-equation, eddy-viscosity closure that incorporates a term designed to account for the interactions between the organized mean-flow periodicity and the random turbulent motions. Comparisons with experimental data show that the two approaches yield results that are generally comparable and in good accord with the experimental data. The main conclusion of this work is that the URANS approach, which is considerably less demanding in terms of computer resources than LES, can reliably be used for the prediction of unsteady separated flows provided that the effects of organized mean-flow unsteadiness on the turbulence are properly accounted for in the turbulence model.

Turbulent Flow Velocity Between Rotating Co-Axial Disks of Finite Radius

1989 ◽  
Vol 111 (3) ◽  
pp. 333-340 ◽  
Author(s):  
J. F. Louis ◽  
A. Salhi
Keyword(s):  
Turbulent Flow ◽  
Turbulence Model ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Finite Radius ◽  
Navier Stokes Equations ◽  
Rotating Cavity ◽  
Tangential Wall ◽  
Frictional Forces

The turbulent flow between two rotating co-axial disks is driven by frictional forces. The prediction of the velocity field can be expected to be very sensitive to the turbulence model used to describe the viscosity close to the walls. Numerical solutions of the Navier–Stokes equations, using a k–ε turbulence model derived from Lam and Bremhorst, are presented and compared with experimental results obtained in two different configurations: a rotating cavity and the outflow between a rotating and stationary disk. The comparison shows good overall agreement with the experimental data and substantial improvements over the results of other analyses using the k–ε models. Based on this validation, the model is applied to the flow between counterrotating disks and it gives the dependence of the radial variation of the tangential wall shear stress on Rossby number.

A Reynolds-Averaged Navier-Stokes Solver in a Turbomachinery Design System

2007 ◽  
Author(s):  
Fahua Gu ◽  
Mark R. Anderson
Keyword(s):  
Turbulence Model ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Integrated Design ◽  
Navier Stokes ◽  
Design System ◽  
Navier Stokes Equations ◽  
Wall Functions ◽  
Machine Performance ◽  
Reynolds Averaged Navier Stokes

The design of turbomachinery has been focusing on the improvement of the machine efficiency and the reduction of the design cost. This paper presents an integrated design system to create the machine geometry and to predict the machine performance at different levels of approximation, including one-dimensional design and analysis, quasi-three-dimensional-(blade-to-blade, throughflow) and full-three-dimensional-steady-state CFD analysis. One of the most important components, the Reynolds-averaged Navier-Stokes solver, is described in detail. It originated from the Dawes solver with numerous enhancements. They include the use of the low speed pre-conditioned full Navier-Stokes equations, the addition of the Spalart-Allmaras turbulence model and an improvement of wall functions related with the turbulence model. The latest upwind scheme, AUSM, has been implemented too. The Dawes code has been rewritten into a multi-block solver for O, C, and H grids. This paper provides some examples to evaluate the effect of grid topology on the machine performance prediction.

Numerical Calculation on Vortex-Induced Vibration of the Circular Cylinder Using Low Reynolds Model in Hybrid Method

2009 ◽  
Author(s):  
Xingwei Zhang ◽  
Chaoying Zhou
Keyword(s):  
Numerical Calculation ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vortex Induced Vibration ◽  
Mesh Method ◽  
Volume Method

Fundamental research on interaction between flow and structure is presented for computation the fluid dynamics of different two-dimensional oscillating models. The Navier-Stokes equations are solved using finite volume method. A multigrid mesh method which was applied to the situation of flow past the stagnating or vibrating cylinder is developed to simulate this type of flow. The interactive results between flow and structure rigid cylinders have been present. The computation fluid dynamic codes mainly with low Reynolds RANS solver are used to solve the impressible viscous Navier-Stokes equations. Finite volume method which is coupled with conformal hybrid mesh method is developed to simulate this type of flow. Numerical investigation focused on the response and the fluid forces on the cylinders and also observed the different shedding model in the wake. The numerical results are compared in detail with recent experimental and computational work. Present numerical comparison also showed that solution using different turbulence model will make the result have a little discrepancy and each turbulence model has respective characteristics in numerical solution on the vortex-induced vibration of the cylinder. In addition, the formation of the 2P vortex shedding model through the lock-in region and the beginning of the shedding model transformation in numerical calculation from 2S model to 2P model has been analyzed.

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.

Dynamics of Pulsed Jet in Crossflow

2007 ◽  
Author(s):  
M. Arienti ◽  
M. C. Soteriou
Keyword(s):  
Stokes Equations ◽  
Near Field ◽  
Numerical Approach ◽  
Mie Scattering ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Pulsed Jet ◽  
Jet In Crossflow ◽  
Lagrangian Equations ◽  
Phase Doppler Interferometry

We examine the effect of time-dependent forcing on jet-in-crossflow atomization in the case of pulsed liquid injection and uniform crossflow. The dynamics of the jet is captured by a numerical approach that blends interface tracking of the liquid surface with an empirical description of the atomization process. The unsteady Reynolds-Averaged Navier-Stokes equations for the gas and the continuous (i.e., preceding breakup) liquid phase are solved simultaneously with the Lagrangian equations for the droplet trajectories. This approach captures the near field transient due to the opening (closing) of the fuel valve, as well as the convective delay of the spray in the far field. Validation is carried out with Phase Doppler Interferometry (PDI) and Mie scattering measurements at standard conditions for pulsed jets of water and ethanol in crossflow air. The discussion is focused on the shape of the convecting spray pulse and on the trends due to variations in crossflow and jet velocities.

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