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.