Flow Over a Blunt Disk With Incidence: Location of Stagnation Point and Flow Separation

The flow over a blunt disk placed in a stream of air was investigated by means of detailed velocity measurements employing Laser-Doppler-Anemometry (LDA). Special attention was spent to the effect of incidence. This parameter governed the location of the stagnation point and the length of the separation bubble. For a parallel disk with finite thickness, a large separation bubble was formed at the leading edge, followed by reattached regions of the turbulent flow. With increasing incidence, the length of the separation bubble significantly decreased, and the stagnation point moved from the blunt side to the leading edge. For angle of incidence higher than a special transition value, a stagnation flow over the disk surfaces resulted without significant turbulence. In case of a heated disk, the corresponding transition of the mean convective heat transfer coefficient as function of incidence was very sharp and discontinuous.