<p>The internal flow field of the rotating detonation engine is unique and complex due to the curvature of the annular combustion channel and pressure relief at the exit of the combustor. Despite this complexity, there are several prominent flow field features: the detonation wave front, the refill zone, the trailing oblique shock, and the shear layer. This paper studies the detonation wave structure, developing a model that can predict the wave structure and the wave mode based solely on the dimensions of the engine and the inlet flow conditions. The results from this model are compared to a combination of experimental and computational data in the literature. Further analysis is made with various propellants to extrapolate the effects of engine operation on the wave structure. Further work on the wave structure could lead to predicting engine performance.</p>