Flow Control Using Thermal Bumps in Hypersonic Flow

Abstract

Experimental results of flow change caused by thermal bump in Mach 5 flow over a flat plate with sharp leading edge are presented. A circular electrical resistive heating element (16 mm in diameter) with temperature of 770K and 75W power input is embedded flush to the the flat plate at 40mm from leading edge. Quantitative results including the streamwise and spanwise surface pressure distributions and pitot pressure measurements at different locations as well as qualitative Schlieren and surface oil flow flow visualisation results are used to describe the effect of the so called ‘thermal bump’ on the flow field. A weak oblique shock wave at the upstream of the bump and thickened boundary layer at the downstream of heated area are observed in Schlieren pictures that are representative effects induced by the thermal bump reported in the literature. Oil dot and oil film results show the induced vortex structures growing from downstream of heating element to the trailing edge of flat plate. The pitot probe pressure variations are observed at 2mm and 7mm above the flat plate. The highest pitot pressure decrement of 33% appears at 2mm above the heating element. The variation also appears in surface pressure measurements but the value is quite small (less than 4%) considering the measurement uncertainties. The main frequency of 175Hz as an additional disturbance was obtained on the surface pressure signal using the FFT analysis.