Study on boundary layer in a rotating channel

该项目的目的是弄清楚科里奥利力对旋转通道后壁和前壁上发展的二维边界层以及固定的横向/横向圆柱体后的湍流尾迹的影响，并提供旋转湍流边界层数值模拟所需的大量时间平均和湍流量的数据。在此基础上，设计了旋转风洞，并进行了定量实验，实验结果表明，旋转通道对前侧边界层的发展有促进作用，对后侧边界层的发展有抑制作用。边界层的二维性在尾部被保留，而与Taylor-Goertler型纵向涡相对应的三维在前部产生。在较高的旋转次数下，在后方观察到再椎弓根的现象。雷诺应力数据与有旋转的雷诺应力方程的预测值定性一致。在固定跨距圆柱后的旋转尾迹中，由于主流的横向速度梯度和瞬时科里奥利力引起的流动不稳定性，在较低的雷诺数下发生了脱落涡的破裂。对于沿展向布置的小展弦比圆柱后的湍流尾迹，平均速度和湍流强度的分布不是关于尾迹中心线对称的。尾迹是一种非常复杂的三维流动，这是因为在旋转通道的顶壁和底壁的边界层中存在三维分离和二次流。

The objective of project is to make clear the effects of Coriolis force on the developing two-dimensional boundary layer on trailing and leading side walls of a rotating channel, on the turbulent wake behind a fixed spanwise/transverse circular cylinder, and to offer many data on time-mean and turbulent quantities which are desirable in numer-ical simulation of rotating turbulent boundary layer. Thus, a rotating wind tunnel was designed, and quantitative experiments were performed.The experimental results indicate that the development of boundary layer on the leading side in rotating channel is promoted and suppressed on the trailing side. Two-dimensionality of the boundary layer is preserved on the trailing side, while three-dimensionality corresponding to Taylor-Goertler type longitudinal vortices is generated on the leading side. At higher rotation number, the phenomenon of relaminarization was observed on the trailing side. Reynolds stresses data agreed qualitatively with that predicted from the Reynolds stress equations with rotation.In a rotating wake behind a fixed spanwise cylinder, breakdown of shed vortices occurs at lower Reynolds number than in a non-rotating wake because of a transverse velocity gradient of primary flow and a flow instability due to instantaneous coriolis force. For a turbulent wake behind a low aspect ratio cylinder located spanwise, profiles of mean velocity and turbulence intensity are not symmetrical about the wake centerline. The wake is a very complex three-dimensional flow because of a three-dimensional separation around a cylinder and a secondary flow in a boundary layer on the top and bottom walls of a rotating channel.