Second moment closure modeling and dns of stratified shear layers

Naman Jain, Xinyi Huang, Xiang Yang, Robert Kunz, Hieu T. Pham, Sutanu Sarkar

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Buoyant shear layers are encountered in many engineering and environmental applications, and have been studied by researchers in the context of experiments and modeling for decades. Often, these flows have high Reynolds and Richardson numbers, and this leads to significant/intractable space-time resolution requirements for DNS or LES modeling. On the other hand, many of the important physical mechanisms in these systems, such as stress anisotropy, wake stabilization, and regime transition, inherently render eddy viscosity-based RANS modeling inappropriate. Accordingly, we pursue second-moment closure (SMC), i.e., full Reynolds stress/flux/variance modeling, for moderate Reynolds number non-stratified, and stratified shear layers for which DNS is possible. A range of sub-model complexity is pursued for the diffusion of stresses, density fluxes and variance, pressure strain and scrambling, and dissipation. These sub-models are evaluated in terms of how well they are represented by DNS in comparison to the exact Reynolds averaged terms, and how well they impact the accuracy of the full RANS closure. For the non-stratified case, the SMC model predicts the shear layer growth rate and Reynolds shear stress profiles accurately. Stress anisotropy and budgets are captured only qual- itatively. Comparing DNS of exact and modeled terms, inconsistencies in model performance and assumptions are observed, including inaccurate prediction of individual statistics, nonnegligible pressure diffusion, and dissipation anisotropy. For the stratified case, shear layer and gradient Richardson number growth rates, and stress, flux and variance decay rates, are captured with less accuracy than corresponding flow parameters in the non-stratified case. These studies lead to several recommendations for model improvement.

Original languageEnglish (US)
Title of host publicationFluid Mechanics; Micro and Nano Fluid Dynamics; Multiphase Flow
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791885307
DOIs
StatePublished - 2021
EventASME 2021 Fluids Engineering Division Summer Meeting, FEDSM 2021 - Virtual, Online
Duration: Aug 10 2021Aug 12 2021

Publication series

NameAmerican Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM
Volume3
ISSN (Print)0888-8116

Conference

ConferenceASME 2021 Fluids Engineering Division Summer Meeting, FEDSM 2021
CityVirtual, Online
Period8/10/218/12/21

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering

Cite this