Numerical Boundary Layer and Heat Flux Characterization in the THOR and NPS RDEs

The boundary layer in Rotating Detonation Engines is periodically disturbed by a passing detonation wave and is under a constantly changing freestream pressure gradient. These two external forces combine to make the boundary layer, and thus heat flux, appear chaotic. In this paper URANS simulations of several 3D annular and 3D unwrapped RDEs are conducted and processed to characterize heat flux with isothermal walls. The results of these simulations are used to tune a boundary layer correlation which is implemented in a Method of Characteristics (MOC) solver to quickly estimate heat flux. The experimental comparison shows that first cell heights of the order of 15 nanometers are required to resolve wall heat flux in 3D URANS, and that reduced chemical mechanisms for H2-air substantially underpredict the width of detonation passing heat flux profiles, leading to large underprediction of total heat load.