Fluidic Control of Aerodynamic Loads on a Circular Cylinder

Changes in flow symmetry and aerodynamic loads that are effected by spanwise 2- and 3-D Coanda wall jets over a 2-D cylinder wind tunnel model of rotorcraft tail boom in cross flow are explored with emphasis on jet-flow interactions and their effects on the near wake. Whereas the 2-D wall jets are nominally spanwise-uniform, arrays of 3-D fluidically-oscillating jets effect spanwise-segmented actuation. The actuation level of the 2- and 3-D jets is characterized by the coefficient of the force effected on the cylinder in the absence of a cross flow. While for a given force coefficient, the mass flow rate of the 2-D jets is significantly higher than the 3-D jets, the operating pressure of the 2-D jets is lower than the 3-D jets, and so their fluidic actuation power is comparable. It is shown that for a given force coefficient the 3-D jets attain a higher lift increment compared to the 2-D jets that is further accentuated as the azimuthal positions of the jets increases relative to separation of the base flow. Suppression of separation and the turning of the cross flow by the jets investigated using PIV reveal differences in turbulent entrainment, pressure gradients and vorticity structure, which are also explored using POD analysis of instantaneous PIV data.