PIV measurement of separated flow over a blunt plate with different chord-to-thickness ratios

Influence of incident vortex street on separated flow around a finite blunt plate: PIV measurement and POD analysis

“…The shortest plate in each branch (i.e., c/t¼3, 6 and 9) corresponded to regular vortex shedding, but increasing the c/t in each branch gave rise to irregularities in vortex shedding. Through particle image velocimetry (PIV) measurements of the flow at Re¼1 Â 10 3 , Shi et al (2010) convincingly demonstrated that the separated shear layer in a system with c/t¼ 3.0 did not re-attach to the plate's surface. Instead, the separated layer gave rise to a highly unstable wake, coupled with energetic leading-edge vortices.…”

“…For a finite blunt plate in the presence of an undisturbed uniform free-stream flow, the Karman vortex street that would normally form behind a very short blunt plate can be considerably suppressed by elongating the plate in the streamwise direction. This elongation can produce entirely different vortex shedding features, depending on the chord-to-thickness ratio (Nakamura et al, 1991;Shi et al, 2010). However, in most practical situations, the flow is under considerable influence from the upstream turbulent flows, which are superimposed with the complex behavior of vortical structures.…”

“…A literature survey shows that various studies have been made on vortex shedding over finite blunt plates in the presence of undisturbed free-stream flows (Nakamura et al, 1991;Ohya et al, 1992;Shi et al, 2010;Zhang and Liu, 2012). Concerning the flow at Reynolds number Re ¼10 3 , Nakamura et al (1991) compiled the dependency of vortex shedding over a finite blunt plate on a given chord-to-thickness ratio (c/t).…”

“…The separated shear layer in a system with c/t ¼6.0 periodically re-attached to the plate's surface close to the trailing edge, resulting in intensified fluctuations of the wake immediately behind the trailing edge. In a system with c/ t ¼9.0, the separated shear layer always re-attached to the plate's surface far upstream of the trailing edge, and did so without inducing large fluctuations of the near wake (Shi et al, 2010). Recently, Zhang and Liu (2012) performed measurements of the wall-pressure fluctuations on a plate with c/t¼9.0 at Re¼1.58 Â 10 4 .…”

“…As an extension of the work by Shi et al (2010), this study was directed mainly toward understanding the influence of incident vortical structures on the global characteristics of the separated flows around finite blunt plates with different chord-to-thickness ratios. Toward this end, three systems were selected for comparative studies with and without incident vortical structures, i.e., c/t¼3.0, 6.0 and 9.…”