Quadrant analysis of a transitional boundary layer subject to free-stream turbulence

• Published in: Journal of fluid mechanics Vol. 658; pp. 310 - 335
• Main Authors: NOLAN, K. P., WALSH, E. J., McELIGOT, D. M.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 10.09.2010
• Subjects: Boundary layer; Boundary layers; boundary-layer transition; Exact sciences and technology; Flow velocity; Fluid dynamics; Fluid flow; Fluid mechanics; Fundamental areas of phenomenology (including applications); instability; Instrumentation for fluid dynamics; Physics; Quadrants; Reynolds number; streaks; Transition to turbulence; Turbulence; Turbulent flow; Turbulent flows, convection, and heat transfer; turbulent spots; Vorticity; Walls; streaks; turbulent spots; boundary-layer transition; instability; Test facilities; Wind tunnel test; Turbulent bursting; Particle image velocimetry; Transition flow; Experimental study; Velocity measurement; Boundary layers; Turbulent laminar transition; Flat plate
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/S0022112010001758

This paper presents analyses of particle image velocimetry measurements from a boundary layer on a flat plate subject to grid-generated free-stream turbulence. The pre-transition region and early stages of breakdown to turbulent spots are explored by means of quadrant analysis and quadrant hole analysis. By isolating the contributors to the Reynolds shear stresses, it is possible to identify coherent structures within the flow that are responsible for the production of TKE. It is found that so called ‘ejection’ events are the most significant form of disturbance, exhibiting the largest amplitude behaviour with increased negative spanwise vorticity. Sweep events become increasingly large close to the wall with increased Reynolds number and intermittency.