Currently, there exists a lack of confidence in the computational simulation of turbulent separated flows at large Reynolds numbers. The most accurate computational methods available are prohibitively costly for use in engineering applications. As a result, low-cost models using the Reynolds-averaged Navier-Stokes (RANS) equations are often applied to flows far beyond those for which they were originally designed. These methods will regularly reproduce integrated flow quantities within engineering tolerances (e.g, pressure on a surface); however, such metrics are often insensitive to bluff body flow physics, and therefore, poor indicators of simulation fidelity.

Using concepts borrowed from large-eddy simulation (LES), a two-equation RANS model is modified to simulate a bluff body turbulent wake. This modification only requires the computation of one additional scalar field, adding very little to the overall computational cost. When properly inserted into the baseline RANS turbulence model, this modification mimics the fidelity of LES in a separated wake, yet reverts to the un-modified form at solid surfaces. In this manner, superior predictive capability may be achieved without the additional cost of fine spatial resolution associated with LES near solid boundaries.

In this presentation we compare simulations of the modified and baseline RANS models to both high-resolution LES and experimental data for the canonical circular cylinder wake at Reynolds number 3900. Mean value and triple-decomposition analysis reveal substantial improvements using the modified system that appear to drive the flow solution toward that of LES, as intended.

In addition, the parallelized, overset grid algorithms used in this investigation are subject to code verification via the Method of Manufactured Solutions. The presented results confirm both the spatial and temporal order of accuracy.