Higher Heat Transfer Efficiency in Laminar Structured Boundary Layers than in Turbulent Boundary Layers, Numerical and Experimental Approach

Unexpected behavior has been observed in heat transfer in a concave boundary layer at a low free-stream velocity, a configuration surprisingly ignored in the literature. The boundary layer is laminar with strong embedded G\"ortler vortices. Precise measurements of the wall heat transfer in this situation demonstrate that heat transfer enhancement was extremely large even compared to the turbulent flat-plate case. Analysis demonstrates that the boundary-layer transition is dominated by the centrifugal instability at a free-stream velocity below a critical value. Further results reinforce the discussion by analysis of the influence of forced upstream perturbations coupled with a set of flow visualizations. Numerical computation of the linear and nonlinear development of steady G\"ortler vortices and their most amplified primary instability have been developed and these results are compared with the experimental measurements.