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Investigations on the Effect of Steady and Pulsed Surface. Thermal Perturbations on the Hypersonic Flow-Field Over a Flat Plate and a Sharp Cone
Interim rept. 12 Feb 2008-10 Mar 2010
INDIAN INST OF SCIENCE BANGALORE DEPT OF AEROSPACE ENGINEERING
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The effects of both steady and pulsating thermal bump presence in the vicinity of the boundary layer of generic bodies have been investigated. The variation of surface static pressure along a sharp leading edge flat plate at angle of attack 10 deg. has been measured in the presence of both steady and pulsating thermal bump. In these studies, both argon and air have been used as test gases. A heating element capable of reaching 1280 K in an area of 13 sq mm is used to generate a steady thermal bump within the boundary layer of the flat plate model. A dielectric barrier discharge DBD over an area of 10 sq mm is used for generating pulsating thermal bump 10 Wsq cm at 6, 8 and 19 kHz near the leading edge of the flat plate. The static pressure distribution along the flat plate is measured at different pulsing frequency of DBD at hypersonic Mach numbers. The pressure field in the presence of steady thermal bump appears to be oscillatory. At some locations downstream of the bump the static pressure decreased by 25 -30 while it increased by 10-15 at other locations in the vicinity of the hot spot. However substantial reductions in the downstream pressure 30 -50 have been measured on the flat plate in the presence of oscillating thermal bump. The reduction appears to be strongly dependent on the pulsing frequency. The pressure reduction seems to be better with argon as test gas compared to the experiments with dry air. Due to the effects of electromagnetic interference and inherently lower values surface convective heat transfer rates on the flat plate in the presence of oscillatory thermal bump could not be measured. However, surface heat transfer rates on a cone-cylinder model in the presence of a steady thermal bump 40 Wsq cm near the apex of the sharp cone has been measured.
APPROVED FOR PUBLIC RELEASE