A One-Dimensional Subgrid Near Wall Treatment forTurbulent Flow CFD Simulation

Prediction of the near wall region is crucial to the accuracy of turbulent flow computational fluid dynamics (CFD) simulation. However, sufficient near-wall resolution is often prohibitive for high Reynolds number flows with complex geometries, due to high memory and processing requirements. A common approach in these cases is to use wall functions to bridge the region from the first grid node to the wall. This paper presents an alternative method that relaxes the near wall resolution requirement by solving one dimensional transport equations for velocity and turbulent kinetic energy across a locally defined subgrid contained within wall adjacent grid cells. The addition of the subgrid allows for wall adjacent primary grid sizes to vary arbitrarily from low-Re model sizing (y⁺≈1) to wall function sizing without significant loss of accuracy or increase in computational cost. The method is applied to zero pressure gradient flow over a flat plate and yields solutions comparable to low-Re modeling with high near-wall resolution. Unlike low-Re or wall function modeling, the new method is shown to be insensitive to size variations of the first primary grid cell.