The Generation and Development of the Go¨rtler Vortices in Boundary Layer on Rotating Curved Wall

The effects of system rotation and wall curvature on the instability of the laminar boundary layer development are studied experimentally using two channels of different centerline curvature, R = 1,000 and 2,000mm. These channels of high aspect ratio are mounted on a rotating table to change the magnitude and direction of the Coriolis force exerting on the flow. Detailed measurements of the time-mean and turbulent velocity components are made using hot-wire probes and the generation, development and mixing processes of the Go¨rtler vortices in the concave side of the curved wall are clarified. Moreover, to examine the developing process of the vortices due to the system rotation in more detail, vortex generators are installed near the leading edge of the plate. The main results are summarized as follows: With the increase in the resultant force acting normal to the boundary layer, the transverse interval of the Go¨rtler vortices generation tends to be smaller in the laminar condition but the vortices tend to be looser in the downstream sections due to the secondary instability and the merge of the vortices. By decreasing the effects of the resultant forces, the behavior of the generated vortices tends to be more unstable, showing a various type of secondary instability modes. When the Coriolis force acts opposite to the centrifugal force due to the channel curvature, the occurrence of the Go¨rtler vortices is suppressed. The three-dimensional configuration of the vortices is enlarged in the transition state of the boundary layer, leading to the early transition to the turbulent state of the boundary layer. When the initial interval of the vortices is fixed by using vortex generators, the configuration of the vortices is kept almost unchanged under the condition that the resultant force of Coriolis and centrifugal ones acts to the wall. When the resultant force acts away from the wall the interval is increased and the development of the vortices is suppressed.