Simulation of stably stratified turbulent channel flow using residual-based variational multiscale method and isogeometric analysis

Abstract

Stably stratified turbulent channel flow (STCF) is a canonical flow that is representative of shear-driven boundary mixing processes in geophysical settings. We examine the performance of a turbulence modeling framework composed of residual-based variational multiscale method (RBVMS) and isogeometric analysis (IGA) applied to STCF at friction Reynolds number Reτ=180. The framework is implemented with two augmentation companion features, namely weak imposition of Dirichlet boundary conditions (WD) and a new subgrid-scale (SGS) model. The performance of the modeling framework, as well as its interaction with the two companion features, are assessed in both weakly and strongly stratified regimes. In comparison to existing direct numerical simulation (DNS) data, our study reveals that RBVMS–IGA framework is able to faithfully capture the flow structures and one-point statistics in STCF simulation with relatively coarse grid resolution. The framework also demonstrates its capability of replicating intermittent flow dynamics under strong stratification. Such characteristics dynamics are reproduced robustly when the modeling framework is enhanced with WD and the new SGS model, features that are shown to generally improve numerical accuracy of simulations for the cases tested. Our results confirm the computational efficiency as well as the robustness of RBVMS–IGA framework in modeling wall-bounded stratified flows.