Adjustment of subgrid-scale parameterizations to strong streamline curvature

A subgrid-scale model correction for large eddy simulations that address flowfields with embedded areas of poorly resolved strong streamline curvature effects is proposed. The devised modification is termed NaCoo and provides an isotropic correction of the subgrid-scale viscosity based on local centrifugal stability. The degree of stability is identified via a rotational Richardson number that is determined based on non-Galilean-invariant streamline curvature at every grid point. NaCoo allows for a more realistic representation of inadequately resolved coherent turbulent vortices. Its main benefits are 1) conservation of the peak vorticity in the vortex cores, 2) reduction of vortex core radius growth rates, 3) an approach to properties of tangential velocity profiles found in experiments 4) allowance for appropriate turbulence levels in the vicinity of the vortices, and 5) non suppression of vortex core meandering. The derivation of NaCoo, its properties, and sensitivity to numerical and vortex parameters are described in detail. Applications of the correction to single vortices and aircraft wake vortices in a quiescent and turbulent environment demonstrate the capabilities of the pragmatic correction.