起始攻角附近三角翼涡破裂的演化特性研究

AN INVESTIGATION ON EVOLUTION OF VORTEX BREAKDOWN OVER DELTA-WING NEAR INCIPIENT ATTACK

用数值方法求解Ｎ－Ｓ方程，并用“亚迭代”方法保证时间方向二阶精度，数值模拟了 ７５° 后掠三角翼非定常绕流，给出了详细的涡破裂起始攻角附近涡破裂的形成、发展和演化过程． 涡破裂从开始的螺旋破裂变为向泡状破裂演化的“过渡态”，然后发展到泡状破裂，再由泡状 破裂变为向螺旋破裂演化的“过渡态”，最终发展到典型的螺旋破裂形态．从计算结果中还发 现，当泡状破裂形成后破裂点前移速度明显减慢，同时当从泡状破裂向螺旋破裂演变时，破裂 点出现后移现象．可从最近相关的实验和数值模拟结果中发现这些现象的存在．

In present paper the unsteady flow about 75° sweep delta-wing is numerically simulated by solving the Navier-Stokes equations and the second-order time precision is guaranteed by sub-iteration algorithm. The evolution process of vortex breakdown near incipient attack is given in detail. A special numerical method for initial physical flow field is designed and used in the simulation. The numerical results display that vortex breakdown can have a transition pattern towards bubble-type breakdown from spiral-type breakdown and then develop to the bubble-type breakdown. Following these is opposite transition pattern which towards spiral-type breakdown. At last the flow develops to the typical form of spiral breakdown. The results also suggest that the forward velocity of breakdown point decreases significantly when the bubble type of breakdown formed. But breakdown point can move downstream while vortex breakdown pattern evolves from bubble type to spiral type. These phenomena can be found from recently experimental and computational data. The possible explanation is that the transfer of vorticity along axial and circumference directions with the change of reverse induced-velocity results in these phenomena.