This paper assesses the operability, convective heat flux, and losses of an experimentally built non-premixed 6 cm radius hydrogen-air rotating detonation combustor with an integrated short diverging wall resulting in a low subsonic or supersonic exhaust flow depending on the combustor operating mode. Traditional RDC research investigated either straight or converging–diverging nozzle sections, at a single pressure ratio condition. We prove that a converging–diverging nozzle is not required to achieve complete supersonic (Mach 1.6) exhaust and full throttle from Mach 0.6 to Mach 1.6 is possible. Unsteady Reynolds Averaged Navier Stokes simulations with a one-step chemistry and grid refinement near the walls to resolve the viscous sublayer were used to capture the boundary layer, shock and mixing losses. The combustor's operation was defined through the combustor pressure ratio, which is the ratio between the combustor plenum total pressure over the exit static pressure, and was varied from 2 to 10, and provided stable operation. A low-frequency instability at ∼2 kHz was observed at subsonic outflow due to the unsteady coupling between the downstream plenum and the upstream injector, which was absent for supersonic operation. Injector drops with value down to 40 % were found, and used to determine the isolated combustor pressure gain, and enabled a comparison to canonical two-dimensional reactive simulations. Steady and unsteady reacting and non-reacting simulations are discussed to interpret the rotating detonation combustor's injection dynamics. Subsequently, the pressure gains and losses, the combustor efficiency, and exhaust phase-locked averaged profiles of the relevant parameters are compared to premixed combustor's results, and pressure losses were found to be similar to non-premixed simulations. Finally, the convective heat flux in the detonation region is assessed based on the simulations with isothermal wall boundary conditions of 600 K, and a convective heat flux scaling law as a function of the injector total pressure is proposed.