A method to visualise near wall fluid flow patterns using locally resolved convective heat transfer experiments

The present study demonstrates an alternative approach for describing fluid flow characteristics very close to the wall, using locally resolved convective heat transfer experiments. Heat transfer coefficients on the base surface and around a surface mounted vortex generator of delta-wing shape design, are evaluated with the transient liquid crystal measurement technique and over a range of freestream velocities. Therefore, the local values of exponent m in the equation Nux Remx, which is directly linked to the structure of the boundary layer, can be determined over the complete heat transfer area. The local distributions of exponent m are then directly compared to the footprint of the flow obtained with typical oil and dyesurface flow visualisation. The results indicate that amore appropriate interpretation of the flow structures very close to the wall is possible by analyzing the spatial variation of exponent m, which approximates better the flow pattern compared to the heat transfer coefficients. As ar esult, fluid flow topologies can be directly evaluated from the heat transfer experiments since the distributions of oil-flow visualization and exponent m are qualitatively similar.