Dynamics and interactions of counter-rotating waves in rotating detonation combustors

Better understanding of non-canonical modes such as counter-rotating wave dynamics provides valuable insights for future rotating detonation engine injector design and combustion mode control. The objective of this work is to study the dynamics and interactions of counter-rotating waves in an RDC experimentally. Previous experimental and numerical data suggest that at collision points, the resulting pressure amplitude is not necessarily the result of a linear combination between the waves, but rather a more complex interaction. In this study, we analyze temporally resolved, high-speed pressure and luminosity data for two counter-rotating waves propagating at equal (2CR) and different (2CRT) speeds. This analysis employs a soft-dynamic time warping averaging scheme, which preserves the shape of the data even in the presence of lap-to-lap fluctuations. From this analysis, the non-linear pressure and luminosity interaction at collision is quantified over the wave lap and for different geometries and operating conditions. Notably, it is found that the strength of the non-linearity at collision is mode dependent and increases as one wave becomes stronger relative to the other one. Furthermore, a one-dimensional gas dynamics model is applied to capture wave collisions in an RDC. The model captures the counter-rotating wave interaction in the 2CR mode, indicating that these waves behave like shock waves. However, in the 2CRT mode, the model underestimates the collision pressure, suggesting that additional mechanisms contribute to the nonlinear interaction between the counter-rotating waves.