Experimental Investigation of Surface Flow Pattern on Truncated Cones in Mach 5 Flow: Influence of Truncation Ratio

The flow characteristics on a truncated cone with a cylinder were experimentally investigated in a Mach 5 flow with a Reynolds number 3.8 × 10, based on the cylindrical diameter. Two different truncation ratios of 0.5 and 0.7 were used. The incidence angle varied from -12 to 0 degrees with 3 degrees intervals to investigate the influence of the truncation ratio on the surface flow pattern. The measurement techniques: unsteady pressure-sensitive paint (anodized aluminium method), colour Schlieren photography, and surface oil flow were used. It was found that the distance of the external shock wave from the conical surface depends on the truncation ratio, and the surface pressure on the conical portion increases when the external shock wave moves closer to the model surface. The "external" shock wave denotes a detached shock wave and the "internal" one is the shock wave formed between the detached bow shock wave and the model surface. In the higher truncation ratio at the higher incidence angle, the internal shock wave induced by the flow separation on the conical surface impinges on the external shock wave, which results in its reflection. This reflection leads to the pressure increase on the model surface. On the other hand, this reflection does not appear in the lower truncation ratio. In spite of the different truncation ratios, the angle of the internal shock wave is identical at the same incidence angle. From the oil flow results, the wall shear stress on the leeward conical surface is lager in the higher truncation ratio model.