ON TURBULENT SECONDARY FLOWS INSIDE ROTATING DUCTS ORIENTED AT CERTAIN ANGLES WITH ROTATION AXIS

摘要

In the present study, the fully developed turbulent secondary flows inside rotating square duct oriented at certain angles with axis of rotation are numerically simulated using the nonlinear k-ω models. For rotating duct with θ=0° angle between sidewall plane and axis of rotation, it is noteworthy that the two vortices are generated when Ro=0.05, four vortices are presented when Ro=0.15, and only two vortices are predicted when the rotational speed is increased up to Ro=0.35. For the purpose of comparison, the linear k-ω model is also employed. It is shown that the linear and nonlinear models all produce reasonable results. However, different results are also exhibited with the two models. For example, the nonlinear model predicts less distortion region than the linear model. On the suction side, the nonlinear k-ω model produces greater gradients than the linear model. For rotating ducts with θ=30° and θ=60°, it is noticed that the stronger rotation forces the lower momentum fluid to be confined near the lower left corner, and produces larger range of high mainstream velocities.