Study of the separated high enthalpy flow around a double cone

High enthalpy flow separation over bodies at hypersonic speeds continues to intrigue researchers, since considerable differences are observed between experiments and CFD. In the present study the separated flow field around a double cone has been investigated at nominal stagnation enthalpies of 4.2 MJ/kg and 1.6 MJ/kg. The flow around a double cone (first cone semi-apex angle = 25°; second cone semiapex angle=68°) has been visualized using highspeed image converter camera (IMACON) and double exposure holographic interferometry in the Shock Wave Research Center's (SWRC) free piston driven shock tunnel at Mach 6.99. Presence of a triple shock structure in front of the second cone, and non-linear unsteady shock structure oscillation in the flow field, are the significant results from visualization studies. Further surface convective heat transfer measurements have been carried out at a nominal Mach number of 5.75 in the Indian Institute of Science (USc), hypersonic shock tunnel HST-2. The surface heat transfer in the vicinity of transmitted shock impingement point on the second cone surface fluctuates between 100 W/cm² - 400 W/cm² (± 10 %) for nearly identical (± 8 %) free stream conditions, indicating the severe unsteadiness in the flow field. Similar unsteady fluctuations in the heat transfer and oscillatory shock structure in the flow field around the double cone are also observed in the numerical simulations carried out by solving the axi-symmetric Navier-Stokes equations.