Analysis and characterization of ramp flow separation

Two-dimensional separation on 25 degrees-ramp is studied experimentally in closed-loop wind tunnel. The analysis of the flow conditions and the separation is based on wall pressure distribution, velocity fields obtained by 2D-2C PIV measurements, and velocity profiles obtained by 2C LDV measurements. The boundary layer upstream and downstream the ramp is characterized. To control the longitudinal pressure gradient, a trailing edge flap is used and the flap angle effects are studied. When the flap angle is equal to +7.5 degrees ,the flow around leading edge is symmetric, but the separation is 3D. For the case where the flap is not slanted (0 degrees), the separation is 2D. Proper orthogonal decomposition is used to characterize the separation unsteadiness.