Lateral Spreading Mechanism of a Turbulent Spot and a Turbulent Wedge

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• 作者：David Goldstein ; Jeff Chu ; Garry Brown
• 关键词：Turbulent wedge ; Turbulent spot ; Roughness ; induced transition ; Boundary layer transition
• 刊名：Flow, Turbulence and Combustion
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：98
• 期：1
• 页码：21-35
• 全文大小：
• 刊物类别：Engineering
• 刊物主题：Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer; Automotive Engineering;
• 出版者：Springer Netherlands
• ISSN：1573-1987
• 卷排序：98

文摘

We examine the spreading of turbulent spots and wedges into a surrounding laminar Blasius boundary layer. The spreading is not due to the lateral propagation of turbulent eddies but rather to a developing disturbance in the surrounding spanwise vorticity of the laminar boundary layer. We concentrate on the mechanisms for generating streamwise vorticity. In particular, inclined generally streamwise vortex tubes along the spot/wedge boundary tilt mean shear vortex lines either up or down. These lines subsequently tend to either lag back or lead forward. As the leading or lagging vortex lines continue to wrap around and reinforce the causative inclined tube, the lines arch up or down. The outboard portion of the resulting arch must acquire a vertical, ω_y, component of vorticity which induces the rollup of a new inclined tube now outboard of the first. Close to the wall the arching mechanism is inhibited by the no through flow boundary condition while far from the wall the process is inhibited by the lack of sufficient mean spanwise vorticity.