Computation method and control strategy of rotating separation flows in hydraulic machinery

Rotating separation flow (RSF) in hydraulic machinery is characterized by the large flow separations and complex vortical structures induced by the effects of strong rotation, large curvature and multiple wall surfaces, and conducting efficient engineering computation and putting forward effective control strategy for the RSF are important topics in the inner flow theory. To meet these engineering requirements, the studies on computational method and control strategy of the RSF are conducted in this paper. In terms of the computational method, the time-scale-driven (TSD) hybrid unsteady Reynolds-averaged Navier-Stokes / large eddy simulation (URANS/LES) modelling strategy is clarified, and an adaptive TSD hybrid model is established based on the RSF characteristics in hydraulic machinery, thereby avoiding the problem of non-monotonic grid convergence and improving the robustness. Besides, a novel vortex-feature-driven idea suitable for the RSF is further developed inspired by it. In terms of the control strategy, the secondary flow generation mechanism in a rotor domain is revealed, and the relationship between natural secondary flows and blade loading distributions is grasped. On the basis of it, an active control strategy with general significance is proposed, and a general alternate loading technique (GALT) is established. Both aspects can provide generalized paradigms with expandable potential, which are of benefit to the efficient computation and effective control of the RSF in hydraulic machinery.