Drag Reduction Due to Boundary-Layer Control by Combined Blowing and Suction
BOCHUM UNIV (GERMANY F R) INST FUER THERMO- UND FLUIDDYNAMIK
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A boundary system of combined blowing and suction is investigated. Blowing is applied in the front part of the body where the pressure gradient is favourable, whereas suction is applied in the rear part of the body where adverse pressure gradients exist. In order to avoid the sink drag the volume rate of suction should be equal or smaller than the blowing volume rate. Theoretical investigations of laminar flows include optimization of the blowing velocity distribution as well as second-order boundary layer effects such as pressure drag and displacement effects on friction drag. Experimental results mean velocities and shear stresses of turbulent boundary layers with very strong blowing velocities near the stagnation point of a circular cylinder are used as a basis of a simple prediction method. Experiments on a circular cylinder show considerable drag reductions due to the combined blowing and suction boundary layer control systems.
- Fluid Mechanics