长圆管内旋转流流场的实验测量和数值模拟

MEASUREMENTS AND NUMERICAL SIMULATION OF THE SWIRLING FLOW FIELD IN LONG CIRCULAR PIPE

利用激光多普勒测速仪(LDV)对φ100 mm×3 500 mm圆管内的旋转流流场进行了实验测量,重点研究了切向速度与轴向速度的分布以及湍流强度分布。同时采用FLUENT软件的雷诺应力输运方程模型(BSM)对圆管的湍流流场进行数值模拟,模拟结果和实验测量基本吻合。流场测量和数值模拟结果表明:圆管内的旋转流是Rankine涡结构形态,旋转强度沿轴向存在着明显的衰减特性,且最大切向速度的径向位置沿轴向逐渐向内移动。在长径比为10的位置,轴向速度大致呈"M"状分布,且沿轴向上轴向速度在径向上的变化趋于平缓,但在轴向长径比为16的位置以后轴向速度转变为稳定的轴对称分布,且轴向速度随径向位置的增大逐渐减小。圆管内大部分空间的切向湍流强度与轴向湍流强度波动不大,但在圆管中心处较大,说明该区域气流扰动较大。

The flow field in the circular pipe with a diameter of 100 mm is measured by laser doppler velocimeter （LDV） and simulated with RSM Model. The distribution of the tangential and axial velocities and the turbulent intensity are studied. The experiment data are in good agreement with the simulation results. The resuits show that tangential velocity distribution exhibits the expected combination of the Rankine type vortex： the quasi-forced vortex and the quasi-free vortex. The swirling intensity decreases obviously along z axis and the radial position of the maximum tangential velocity in the cross section moves towards the geometrical center of the circular pipe. When z≤ 10D, the axial velocity distribution exhibits the M shape in the position of the diameter and the value fluctuation of it tums to weaken. In the region z 〉 16D, the axial velocity reduces linearly as the radial position increases. Basically, the turbulence intensity of the tangential and axial directions has slight fluctuations, but the value in the center is somewhat larger. It indicates the air flow perturbation is a little bit stronger.