Local structure of boundary layer transition in experiments with a single streamwise vortex

• Published in: Experimental thermal and fluid science Vol. 68; pp. 381 - 391
• Main Authors: Manu, K.V., Dey, J., Mathew, Joseph
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.11.2015
• Subjects: Boundary layer; Boundary layer transition; Flat plates; Fluid dynamics; Fluid flow; Particle Image Velocimetry; Quadrant analysis; Shear layers; Shear-layer breakup; Streak instability; Streamwise vortex; Turbulence; Turbulent flow; Vortices; Wind tunnels; Streamwise vortex; Boundary layer transition; Streak instability; Quadrant analysis; Shear-layer breakup; Particle Image Velocimetry
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2015.06.013

•Response of subcritical boundary layer to isolated, embedded, streamwise vortex.•Non-inclined high shear layer rolls up and vortices tear away during transition.•Vortex passing frequency scales with square of freestream velocity.•Large ejection events in outer layer.•Some features common to FST-induced, and roughness-induced transition identified. Transition induced by an isolated streamwise vortex embedded in a flat plate boundary layer was studied experimentally. The vortex was created by a gentle hill with a Gaussian profile that spanned on half of the width of a flat plate mounted in a low turbulence wind tunnel. PIV and hot-wire anemometry data were taken. Transition occurs as a non-inclined shear layer breaks up into a sequence of vortices, close to the boundary layer edge. The passing frequency of these vortices scales with square of the freestream velocity, similar to that in single-roughness induced transition. Quadrant analysis of streamwise and wall-normal velocity fluctuations show large ejection events in the outer layer.