Transition Delay in a Hypervelocity Boundary Layer using Nonequilibrium CO2 Injection

Abstract : A new technique to delay transition to turbulence in hypervelocity air flows is introduced and investigated in this work. The main motivation for such a technique is the pressing need to reduce aerodynamic heating rates on hypersonic vehicles. Turbulent heat transfer rates can be an order of magnitude higher than laminar rates at hypersonic Mach numbers. Hence, schemes to delay transition to turbulence could provide an important means to reduce the heating rates on hypersonic vehicles. The technique presented here makes use of the recently discovered behavior of high-enthalpy nonequilibrium CO2. Seven injector geometries were built in which the injection angle, the number of orifices and the diameter of the orifices were varied. Five experimental series were conducted.