Analysis and Measurement of Unsteady Flow in Curved Pipes

(1)在雷诺数为40000的条件下，测量了半径比为2.0的90 °方形弯曲管道上、下游直管段内的三个平均速度分量。研究了从弯曲上游到下游的轴向流偏差和二次流强度。(2)本文采用雷诺应力模型，对圆管内充分发展的紊流进行了数值模拟。数值结果与作者的实验数据进行了比较。计算的速度是在中等协议与实验结果的横截面。(3)在振荡层流条件下（沃默斯利数5.5 ~ 28，迪恩数40 ~ 500），对弯管充分发展区的二次流进行了可视化。得到了二次流的流态、速度分布和涡心位置。

(1) Three components of mean velocity have been measured in a square sectioned 90 degree bend of radius ratio 2.0 with upstream and downstream straight ducts under Reynolds number 40000. The bias of the axial flow and the intensity of the secondary flow were investigated from the upstream of the bend to the downstream.(2) A Reynolds stress model is applied to a fully-developed turbulent flow in a curved circular pipe. Numerical results are compared with the authors' experimental data. Computed velocity is in moderate agreement with the experimental results over the cross section.(3) Visualization was made of the secondary flow in the fullydeveloped region of a curved pipe under oscillatory laminar flow conditions; Womersley number 5.5 to 28 and oscillatory Dean number 40 to 500. The flow pattern, the velocity profile and the vortex center of the secondary flow were made clear.