The behaviour of a separated shear layer past a semi-circular leading edge flat plate, its transition and reattachment downstream to separation are investigated for different imposed pressure gradients. The experiments are carried out in a blowing tunnel for a Reynolds number of 2.44×105 (based on chord and free-stream velocity). The mean flow characteristics and the instantaneous vector field are documented using a two-component LDA and a planar PIV, whereas, surface pressures are measured with Electronically scanned pressure (ESP). The onset of separation occurs near the blend point for all values of β (flap angle deflection), however, a considerable shift is noticed in the point of reattachment. The dimensions of the separation bubble is highly susceptible to β and plays an important role in the activity of the outer shear layer. Instantaneous results from PIV show a significant unsteadiness in the shear layer at about 30% of the bubble length, which is further amplified in the second half of the bubble leading to three-dimensional motions. The reverse flow velocity is higher for a favourable pressure gradient (β = +30°) and is found to be 21% of the free stream velocity. The Reynolds number calculated based on ll (laminar shear layer length), falls in the range of 0.9×104 to 1.4×104. The numerical values concerning the criterion for separation and reattachment agree well with the available literature.
Experiments on Leading-Edge Induced Separated Shear Layer Under Various Imposed Pressure Gradients
Anand, K, Sarkar, S, & Thilakan, N. "Experiments on Leading-Edge Induced Separated Shear Layer Under Various Imposed Pressure Gradients." Proceedings of the ASME 2014 Gas Turbine India Conference. ASME 2014 Gas Turbine India Conference. New Delhi, India. December 15–17, 2014. V001T05A003. ASME. https://doi.org/10.1115/GTINDIA2014-8177
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