Prediction of wall shear-stress fluctuations in wall-modeled large-eddy simulation

Wall-modeled large-eddy simulation (WMLES) is emerging as a viable and affordable tool for predicting mean flow statistics in high Reynolds number turbulent boundary layers. Recently, we examined the performance of two RANS-based wall models in prediction of wall pressure and shear stress fluctuations which are important in flow/structure interaction problems. Whereas the pressure statistics were predicted with reasonable accuracy, the magnitude of wall shear stress fluctuations was severely underestimated (Park \& Moin, \emph{Phys. Rev. Fluids} \textbf{1}, 024404 (2016)). The present study expands on this finding to characterize in more detail the capabilities of wall models for predicting $\tau_w'$. Predictions of several wall models in high Reynolds number channel flows ($Re_\tau$ = 2000) will be presented. Additionally, a recent empirical inner-outer model for $\tau_w'$ (Mathis \emph{et al.}, \emph{J. Fluid Mech.} \textbf{715}:163--180 (2013)) is reconstructed using channel flow DNS database , and it is coupled to WMLES to assess its performance as a predictive model in LES.