Extension of the KDO turbulence/transition model to account for roughness

Abstract

Wall roughness significantly influences both laminar-turbulent transition process and fully developed turbulence. A wall roughness extension for the KDO turbulence/transition model is developed. The roughness effect is introduced via the modification of the k and νt boundary conditions. The wall is considered to be lifted to a higher position. The difference between the original position and the higher position, named as equivalent roughness height, is linked to the actual roughness height. The ratio between the two heights is determined by reasoning. With such a roughness extension, the predictions of the KDO RANS model agree well with the measurements of turbulent boundary layer with a sand grain surface, while the KDO transition model yields accurate cross-flow transition predictions of flow past a 6:1 spheroid.

Full Issue (Vol. 11, June 2023)

“…Equation 9 is slightly modified from Reference (Fang & Xu, 2022) to approximate the viscous, buffer and log layers with reasonable accuracy; however, the wake-deficit layer is over-estimated, as will be seen afterward. On the other hand, Bradshaw, 1967) (with the main shear-stress uv  and 0.09…”

A Zero-Equation Model for External Aerodynamics

“…Equation 9 is slightly modified from Reference (Fang & Xu, 2022) to approximate the viscous, buffer and log layers with reasonable accuracy; however, the wake-deficit layer is over-estimated, as will be seen afterward. On the other hand, 9) and ( 11) can be interpolated to better replicate the k profile over the whole flow domain.…”