A bypass wake induced laminar/turbulent transition

• Published in: European journal of mechanics, B, Fluids B, Fluids, 1999, Vol.18 (6), p.1049-1065
• Main Authors: Kyriakides, N.K., Kastrinakis, E.G., Nychas, S.G., Goulas, A.
• Format: Article
• Language: English
• Subjects: Boundary layer flow; Cylinders (shapes); Exact sciences and technology; Fluid dynamics; Fundamental areas of phenomenology (including applications); Laminar flow; laminar–turbulent transition; Physics; Rotational flow and vorticity; Separated flows; Transition to turbulence; Turbulent flows, convection, and heat transfer; turbulent production; Vortex flow; wake induced transition; Wakes
• ISSN: 0997-7546; 1873-7390
• DOI: 10.1016/S0997-7546(99)00140-5

The process of laminar to turbulent transition induced by a von Karman vortex street wake, was studied for the case of a flat plate boundary layer. The boundary layer developed under zero pressure gradient conditions. The vortex street was generated by a cylinder positioned in the free stream. An X-type hot-wire probe located in the boundary layer, measured the streamwise and normal to the wall velocity components. The measurements covered two areas; the region of transition onset and development and the region where the wake and the boundary layer merged producing a turbulent flow. The evolution of Reynolds stresses and rms-values of velocity fluctuations along the transition region are presented and discussed. From the profiles of the Reynolds stress and the mean velocity profile, a `negative' energy production region along the transition region, was identified. A quadrant splitting analysis was applied to the instantaneous Reynolds stress signals. The contributions of the elementary coherent structures to the total Reynolds stress were evaluated, for several x-positions of the near wall region. Distinct regions in the streamwise and normal to the wall directions were identified during the transition.