Experiments have been carried out to investigate the phenomenon of vortex shedding from the blunt trailing edge of an aerodynamic body in transonic and supersonic flow. The effect of a discharge of bleed air from a slot in the trailing edge has been included and the relationship between the vortex formation and base pressure has been considered.In transonic flow a small amount of bleed air was found to produce a rearward shift in the point of origin of the vortices with a consequent substantial increase in base pressure. The effect was less marked in supersonic flow. At higher rates of bleed two different regimes of vortex shedding were identified and increase in bleed rate caused a reduction in base pressure. For bleed rates giving near-maximum base pressure no vortex shedding occurred.
The aim of the present study is to improve the aerodynamic performance of the bobsled as a function of its shape and the relative position of the athletes inside the bobsled. This performance optimization problem is studied by means of wind tunnel testing. The aerodynamic responses of the manned and unmanned bobsleigh are analysed in terms of overall drag force measurements. Experimental results show that the proposed modi cations to the sidewalls and the nose section of the bobsled improve its drag performance. The relative position of the driver and the brakeman has a great in uence on the drag of the bobsled.
The problem of base pressure in the absence of base bleed has been investigated for a symmetrical model with a square-cut trailing edge. The model was mounted at zero angle of attack in a transonic wind tunnel covering a range of mainstream Mach number from 0.6 to 1.3. The role of vortex shedding was found to be of great importance in the prediction of base pressure. A semi-theoretical analysis for the prediction of base pressure in subsonic and transonic speeds which includes the effect of vortex shedding is proposed.
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