Investigation on mode transition of rotating detonation waves and flow field stability under spatial fluctuation of inlet total pressure

To investigate the underlying mechanism of rotating detonation wave (RDW) mode transition and flow field stability under inlet total pressure spatial fluctuation, numerical simulations of premixed C2H4/air rotating detonation are performed using OpenFOAM. A sinusoidal spatial fluctuation is imposed on the inlet total pressure, and the spatial amplitude and spatial frequency are varied in a coupled manner while the mean inlet total pressure is kept constant. The results show that the final stable mode of RDWs is governed by the coupled effect of spatial amplitude and spatial frequency, rather than by either parameter alone. The underlying mechanism is associated with the formation and evolution of contact discontinuities between the fresh C2H4/air mixture and high-temperature combustion products. As the spatial frequency increases, the distribution density of contact discontinuities increases, which enhances the interactions among counter-rotating shock waves, RDWs, and oblique shock waves and promotes the transition of the high-temperature reaction zone from a discrete distribution to a more continuous distribution. The flow field stability, in terms of pressure signals, RDW velocity, heat release rate, and outlet thrust, demonstrates strong parametric coupling. Within the present parameter range, high spatial frequency combined with an appropriate medium to high spatial amplitude enhances the overall stability of the flow field.