淹没条件下水射流涡旋特性大涡模拟及实验研究

摘要

采用大涡模拟方法对淹没条件下水射流的涡量场进行数值模拟，分析流场中涡旋的产生与扩散机制，并通过相同条件下粒子图像测速仪测量射流的涡量场，对模拟结果和方法进行验证。模拟研究泵压和围压对淹没射流涡旋特性的影响。结果表明：在射流流场中，由喷嘴出口产生一系列涡量集中的点涡旋，随着射流的前进涡旋逐渐扩散，卷吸周围介质并传递能量，卷吸范围逐渐扩大，而卷吸能力沿射流轴向呈指数衰减；随着泵压升高，整个流场中涡旋的涡量值明显增大，涡旋扩散长度直线上升；围压对涡量基本没有影响，围压的增加会使涡旋扩散区长度直线下降，减小卷吸作用范围。%The large eddy simulation was used to numerically simulate the vorticity field of submerged water jet in submerged condition, through which the mechanism of vortex generation and diffusion in the flow field was analyzed. And the simulation results and methods were validated using the particle image velocimetry ( PIV) measurement test of vorticity field under the same conditions. In this way the effect of pump pressure and confining pressure on vortex characteristics of submerged jet were studied. The results show that a series of point vortexes with large vorticity are generated by the nozzle exit in the jet flow field. With the progress of jet development, vortexes spread gradually and entrain the surrounding medium to transfer en-ergy, which causes the scope of entrainment expanded gradually and the entrainment ability decayed exponentially along the jet axis. With the pump pressure increasing, the vorticity of entire flow field increases significantly and the length of vortex diffusion climbs straight. While confining pressure has no effect on the magnitude of the vorticity, and the increase of confi-ning pressure leads to reduce the length of the vortex diffusion.