Application of Molecular Tagging Diagnostics to Turbulent Mixing Enhancement and Control Studies

摘要

Molecular Tagging Velocimetry (MTV) was used to study vorticity dynamics in several flows under investigation for mixing enhancement and control. The evolution of streamwise vorticity, responsible for a large increase in mixing in a confined wake flow, was measured. It was found that the streamwise vorticity has a peak value in excess of 70% of the peak spanwise vorticity. The MTV technique was extended to allow simultaneous whole field measurements of the velocity and a passive scalar on the basis of molecular tagging diagnostics. This new approach also offers a new capability for simultaneous flow visualization and vorticity mapping. The application of MTV to the study of unsteady separation resulted in boundary layer resolved measurements of flow separation in the vortex ring/wall interaction and dynamic stall over a pitching airfoil. The measurements of flow separation over a pitching airfoil, believed to be the first boundary layer resolved measurement of this phenomenon, show that the process of boundary layer separation occurs over a shorter time scale, and is more eruptive, than that captured by the computations to date.