Direct Numerical Simulations of the Turbulence Evolution in a Uniformly Sheared and Stably Stratified Flow

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Aerodynamics and Fluid Mechanics | Engineering


Direct numerical simulations (DNS) are performed to investigate the evolution of turbulence in a uniformly sheared and stably stratified flow. The spatial discretization is accomplished by a spectral collocation method, and the solution is advanced in time with a third-order Runge–Kutta scheme. The turbulence evolution is found to depend strongly on at least three parameters: the gradient Richardson number Ri, the initial value of the Taylor microscale Reynolds numberReλ, and the initial value of the shear number SK/K is found to follow approximately an exponential law. The shear number SK/Reλ indicated that the turbulence growth rate tends to become insensitive to Reλ at the higher end of the Reλ range studied here. The dependence of the critical Richardson number Ricr, which separates asymptotic growth of the turbulent kinetic energy K from asymptotic decay, on the initial values of the Reynolds number Reλ and the shear number SK/0.04<Ricr