Experimental study of heat flux in mixed convective flow over solid waves

In this experimental study, we address transport processes in a mixed convective flow over a heated wavy surface. Therefore, we combine digital particle image velocimetry (DPIV) and two-color planar laser induced fluorescence (PLIF) to simultaneously measure the velocity and temperature field. For this, we propose to use the dye combination Rhodamine B and Rhodamine 110, both excited with the Nd:YAG laser also used for the PIV measurements. We investigate the influence of mixed convection over a wavy surface on the velocity field, turbulence statistics, the temperature field and the heat flux. By computing these quantities we find a correlation between the maximum in the Reynolds stress profiles and the components of the heat flux vector, thus regions of maximum momentum and scalar transport coincide. In addition, we apply a proper orthogonal decomposition (POD) to extract the most dominant flow structures in a measurement plane above the wavy surface. This first POD mode is identified as streamwise-oriented, counter-rotating vortices whose spanwise scaling is also correlated with the maximum of heat flux.