Scale-Resolving Simulations of a Statistically Targeted Forcing Method for Synthetic Turbulence Generation in a Freestream Turbulence

Abstract

Computational fluid dynamics results for synthetic turbulence generation of freestream turbulence by a proposed statistically targeted forcing (STF) method are presented. The STF method has been previously documented for homogeneous isotropic and anisotropic turbulence and formulated to introduce a fluctuating velocity field with a distribution of first and second moments that match a user-specified target mean velocity and Reynolds stress tensor, by incorporating deterministic time-dependent forcing terms into the momentum equation for the resolved flow. This study extends its applicability to generation of freestream turbulence in scale-resolving simulations in which flow is spatially developing. The method provides flexibility in regions where synthetic turbulence needs to be generated or damped, for use in engineering level scale-resolving simulations such as large eddy simulation (LES), and hybrid Reynolds-averaged Navier–Stokes (RANS)-LES. The objective of this study is to evaluate the performance of the proposed STF method in simulations that incorporate monotonically integrated LES (MILES), Smagorinsky (SMAG) LES subgrid stress model, and dynamic hybrid RANS-LES (DHRL) model in reproducing inflow freestream turbulent flow, and the capability of each model to reproduce proper energy decay characteristics downstream of forcing. Results are inter-rogated and compared to target statistical velocity and turbulent stress distributions for inflow turbulence and evaluated in terms of energy spectra. Analysis of the influence of STF model parameters, mesh resolution, and LES subgrid stress model on the results is investigated. Results show that the STF method can successfully reproduce desired statistical distributions in a nearly isotropic freestream turbulent flow.