无阀压电微泵用平面锥管内部流动附壁效应

Coanda effect of flat taper pipe applied in valveless piezoelectric micro-pump

为研究锥管内流体流动中产生的附壁效应对其流阻系数的影响,采用数值模拟的方法对平面锥管内部流动附壁效应进行研究.结果表明：雷诺数Re在300～3000,锥管角度在5～40°时,扩散方向流动可以分为3种状态,即稳定状态、附壁状态和射流状态.锥管角度为10～35°时,锥管内流动易于发生附壁效应.Re在300～1 200时,稳定状态扩散流阻系数随着扩散角的增大迅速降低;附壁状态扩散流阻系数随着扩散角的增大缓慢增大;射流状态扩散流阻系数随着扩散角的增大而缓慢降低.Re在1 800～3 000时,附壁状态扩散流阻系数在锥管角度为30°时达到最大值.流阻系数比在稳定状态和射流状态下基本不变,在附壁状态下随着扩散角的增大迅速减小.

The impact of Coanda effect on the flow resistance coefficient of flat-walled diffusers has been studied by numerical simulation,and the results show that when Reynolds number changes in the range of300 ～ 3 000 and the diffusion angle θ of the cone tube varies from 5° to 40°,the fluid flow to the diffusion direction goes through three stages： the stable state,the wall-attachment state and the jet deflection state,when 10° θ 35°,the Coanda effect can be obtained easily. When Reynolds number ranging from 300 to1 200,with the increasing of diffusion angle,the flow resistance coefficient decreases rapidly during the stable state,increases slowly among the wall-attachment state and decreases gradually in time of the jet deflection state. While Re varies from 1 800 to 3 000,the flow resistance coefficient of the wall-attachment state reaches maximum at θ = 30°. The flow resistance coefficient ratio in steady state and jet condition state is basically unchanged,but decreases quickly during the wall-attachment state with the increasing of diffusion angle.