A DNS Forcing Scheme Representing Anisotropic Production and Deformation in Homogeneous Turbulence

Reliable modeling of complex turbulent flows with coarse resolution LES and next-generation RANS models require accurate representation of anisotropy, a requirement driving the development of tensor eddy viscosity closures in LES, for example. Progress, however, is constrained by the absence of high fidelity reference data that represents the impact of a wide variety of mean velocity gradients on turbulence. One approach to address this shortcoming is to force homogeneous turbulence in a DNS to mimic the effects of a mean velocity gradient. Previous DNS forcing strategies to address this issue only represent one effect of a mean velocity gradient, the anisotropic production of Reynolds stress, they do not represent the resulting deformation of the turbulence. Here we propose a forcing scheme for homogeneous turbulence that represents both effects. It includes (i) a forcing term consistent with anisotropic production of Reynolds stress (ii) a term that approximates the effects of wavenumber evolution due to mean distortion. Introduction of these terms yield a statistically stationary DNS of homogeneous turbulence that approximates the turbulence arising from a mean velocity gradient. Statistical characteristics of the resulting turbulence have been analyzed and the use of this data for LES and RANS modeling will be discussed.