| 英文摘要 |
Found in many important engineering applications, the juncture vortex is formed when a boundary layer passes body normal to the flow. It is a complicated three-dimensional physical phenomenon which could result in serious negative effects. In this study, we focus on the effects of free-surface waves on the formation and unsteady variation of the horseshoe vortex for a flat-plate turbulent boundary-layer flow past a wing with and without a strake. The strake employed in the present study was designed to eliminate the horseshoe vortex for the same boundary-layer flow without a free surface. We attempt to reveal its effectiveness when it is used in the free-surface flow with waves. In computations, we employed the CFD method to investigate the problem. The unsteady Reynolds-averaged Navier-Stokes (URANS) equations were discretized. The turbulence model was employed to simulate the turbulent effect and the volume of fluid (VOF) method for the free surface prediction. The structured mesh with polyhedron was generated for the computational domain. The Reynolds number was based on the chord length of the wing. A series of computations were conducted, and many interesting results obtained. Via three-dimensional graphics, we captured the flow characteristics including the horseshoe vortex system at the leading edge and the complicated flow phenomena in the wake region. It was also found that, due to the periodic change of the velocity field of waves, the stretching and vorticity of the horseshoe vortex would also change significantly, which would result in worse effects on the structure of engineering interests. However, by installing an appropriate strake on the wing, we observed that it had beneficial effects on the flow field to a great extent, such as eliminating horseshoe vortex and weakening vortex shedding. |
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