Abstract
A computational-based investigation has been carried out to examine the heat transfer effects of normal and tangential blowing on blunt surfaces exposed to high Mach number flows. Experimental results from such studies where a controlled outflow is imposed upon a surface under hypersonic conditions are few and far between. Simple 3D axisymmetric configurations supporting flat front surfaces suited to accommodate uniform frontal flow or round-nosed conical bodies with a stepped shoulder to provide uniform parallel flow to the conical surface were selected from a NASA experiment for validation purposes. Uniform outflow of 0.55 to 1.0 kg/s was applied in the presence of the prevailing free stream of M=6.8 to assess the extent of heat transfer rate alleviation. The numerical simulation confirmed the experiment that the application of outflow in both cases leads to the surface heat transfer relief.
Highlights
Hypersonic vehicles experience very high heating rates near the leading edge regions
A very thin layer of coolant is introduced adjacent to the surface by blowing from a high-pressure reservoir inside the vehicle. This layer of cool fluid sandwiched in between the high-pressure flow ahead of the blunt nose and the vehicle surface acts as physical insulation but has the effect of fattening up the underlying boundary layer leading to heat transfer rate reductions
Normal and tangential blowing has been examined as a means of reducing the blunt body hypersonic heat transfer rates
Summary
Hypersonic vehicles experience very high heating rates near the leading edge regions. In terms of heat transfer rate reduction through surface blowing, some of the earlier studies were reported by Howe and Mersman [14] for transpiration cooling and by Low [15] for cooling studies on flat plates placed in supersonic flow. It was, the classic work by Pappas and Okuno [16, 17] that was able to quantify the effects of injectants heavier and lighter than the air. The results were systematically examined against the measurements provided by Nowak [20] on the above two primary configurations of interest and the two solid blunt nose axisymmetric configurations included as baseline models
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