Abstract:

A hybrid Eulerian-Lagrangian solver is developed by coupling the computational fluid dynamics (CFD) method with viscous vortex particle method for complicated rotor vortex field analysis. In order to capture the detailed features of a flow field such as its three-dimensional blade tip effect, shock wave, etc., the CFD method is adopted to compute the near-body flow, while a high revolution model is established using the viscous vortex particle method to track the wake since the tip vortex has compact structural characteristics in a high Reynolds number rotor flow field. The "integrated vorticity source method" and the "boundary surface method" are used to exchange the information between the two computational domains. Using the proposed method, a standard test (Caradonna-Tung rotor) for CFD method verification is performed as an example, and numerical simulation is carried out for a hover condition in which the wake plays a more obvious role than in other flight conditions. By comparing the flow characteristics in coupled boundary and pressure coefficient distribution of the blade surface, the validity of the method is verified. Furthermore, different methods are comparatively analyzed from the aspects of the accuracy of capturing the rotor wake, vorticity dissipation characteristics and calculation time. The results show that the hybrid method possesses the advantages of both the CFD method and the Viscous Vortex Particle Method, and has a unique advantage in the rotor flow field numerical simulation.

Key words: coupled Eulerian-Lagrangian method, viscous vortex method, rotor wake, rotor flow field, helicopter