On the interaction of a laminar heated boundary layer with a roughness element: A comparison of experiments and simulations for steady flow

The aim of this study is a direct comparison of experimental and simulation results of two flows, a laminar boundary layer developing on a flat heated plate and the interaction of a laminar boundary layer with a single cylindrical roughness element of small aspect ratio with a height similar to the boundary layer thickness. The experiments were performed in a water channel using temperature-sensitive paint (TSP) on a heated flat plate on which the boundary layer develops. The numerical simulations are meant to complement the experimental data, allowing for a direct comparison with the experiment and adding additional information not easily accessible from the experiment. In the case of the laminar boundary layer developing over a flat heated surface, experimental TSP measurements and simulation results of the surface temperature show strong agreement and a correlation coefficient for the two temperature fields of 0.99 is obtained. In the case of a laminar boundary layer interacting with a low aspect ratio roughness element, the comparison between experimental and numerical data revealed the role played by buoyancy effects even at the small implemented temperature differences between surface and fluid. With consideration of buoyancy in the simulations, again good agreement between the experimental and simulation results is obtained with a correlation coefficient of 0.95 for the respective temperature fields. The complex vortical system identified in the flow field via the simulations was shown to be consistent with the thermal footprints measured on the heated wall in the experiments. • The development of a laminar boundary layer over a heated plate is studied experimentally and numerically and a correlation coefficient of 0.99 is obtained. • The interaction of a laminar boundary layer with a roughness element is studied experimentally and numerically and a correlation coefficient of 0.95 is obtained considering buoyancy effects. • The three-dimensional vortical structure, consisting of a horseshoe vortex around the roughness element, a recirculation zone in the near wake, and a trailing system of counter-rotating vortices in the wake is visualized. • The simulations indicate that buoyancy effects are present in this low speed experiment when the heat flux, which is required for the TSP measurement, is imposed. • The electrical heating power density transferred into the fluid domain is determined from the simulations.