TIME-AVERAGED FLOW IN A CONICAL DIFFUSER WITH VORTEX GENERATOR JETS

摘要

To develop the vortex generator jet method (VGJs) for flow separation control in diffuser, a conical diffuser with vortex generator jets is studied numerically. The time-averaged flow fields characterized by the incompressible Reynolds averaged Navier-Stokes equations with the standard k ― ε turbulence model are solved using the commercial code CFX-TASC flow which employs the finite volume method. In numerical calculations, the time-averaged flow in a conical diffuser with vortex generator jets is treated firstly. Then, the effects of jet parameters such as velocity ratio and number of jets on the pressure recovery coefficient are studied, and they are compared with the experimental data obtained using a conical diffuser with the divergence angle of 18 deg. The jet velocity vector has a fixed pitch angle of 30 deg and a fixed skew angle of 90 deg. The velocity ratio is changed from 0.0 to 3.5. Interaction of longitudinal vortices with turbulent boundary layer is considered based on the detailed analyses for velocity fields and vorticity fields at different cross planes downstream of vortex generator jets. It should be noted that the time-averaged computational results show qualitative agreement with the experiments and will be used to investigate the development of the longitudinal vortices produced by vortex generator jets in a conical diffuser.