Interaction of a heated boundary layer with a roughness element: a comparison of numerical simulations with experiments using temperature-sensitive paint

Kurzfassung

This study considers the interaction of a laminar boundary layer developing on a flat heated plate with a single cylindrical roughness element of small aspect ratio and with a height similar to the boundary layer thickness. A combined experimental and simulation approach is used. The experiments were performed in the laminar water channel at the University of Stuttgart using Temperature-Sensitive Paint (TSP). The numerical simulations by means of ANSYS Fluent complement the experimental data, allowing for a direct comparison with the measurements and adding additional information not accessible from the experiment. A heat flux density of 200 W/m^2 is used in the simulation, which closely matches the set heat flux in the experiment. Details on the experiments and simulations are available in a recent publication. The surface temperature fields show the footprints of a complex vortex system, consisting of a horseshoe vortex wrapped around the upstream section of the roughness element, a near wake structure, and trailing vortices in the far wake. Additional trailing vortices form in the wake, which critically depend on the consideration of buoyancy effects in the flow. The overall correlation coefficient of the two surface temperature fields from the TSP experiment and simulation has a value of 0.914, indicating strong agreement between the two sets of results. counter-rotating vortices in the wake of the roughness element. The additional vortex pair appearance is more pronounced with higher heat flux densities supplied to the flow, which will be elaborated on in the presentation.