On the Interaction of a Blasius Boundary Layer with a Roughness Element: A Comparison of Experiments and Simulations for Steady Flow

Abstract

The interaction of a Blasius boundary layer developing on a flat surface with a cylindrical roughness element of small aspect ratio and a height smaller than the local boundary layer thickness is studied for steady flow. The flow develops a horseshoe-shaped vortical structure around the roughness element as well as a recirculation zone directly downstream of the roughness element. This flow configuration was studied experimentally (J. Lemarechal et al., 2018), visualizing the flow structure through the use of temperature-sensitive paint (TSP) applied to a heated surface. The simulations using Ansys CFD aim to reproduce the previous experiments and to provide additional information, such as the wall shear stress distribution, inaccessible to the experiments alone. This contribution will focus on the development and validation of the simulation approach, including the choice of domain size and resolution as well as the heat flow from the surface to the fluid domain. The simulations match the experimental results well both qualitatively and quantitatively. For example, a comparison of the surface temperatures in the roughness element’s wake region yields a correlation coefficient of about 0.85 between the simulations and experiments.