The total drag of bluff bodies is dominated by large separated flow structures in the wake. In this study the drag improving effects of fluidic oscillators in combination with base flaps are examined on a rectangular bluff body. Force and pressure measurements are conducted under consideration of various parameters which are complemented by extensive flow field measurements via particle image velocimetry to understand the drag reduction mechanisms within the model's wake. A net drag reduction of 15% is measured at a flap angle of 20°, a flap length of 150mm, and a momentum coefficient of 2 to 3%. However, the most efficient drag reduction is obtained at smaller flap angles with a lower momentum input. The efficacy of the flow control system depends on the appropriate combination of several parameters. The flap length has to be sufficiently long to shift the wake structure far enough downstream away from the base plate. However, any additional increase in flap length does not yield any further benefits. The flap angle has to be large enough to provide a sufficient inward deflection of the outer flow. If the angle is too large, actuation becomes inefficient due to the pressure gradient imposed by the shear layer from the model's opposite side. Furthermore, the flaps at high deflections provide additional area for the low pressure to act in streamwise direction and thereby negate the effects of actuation. The actuation intensity is best governed by the velocity ration for varying actuator spacing.
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