Experimental and Numerical Investigation of Flow Control on Bluff Bodies by Passive Ventilation

In this work, the so-called Natural or Passive Ventilation drag reduction method is investigated experimentally and numerically. Passive Ventilation is performed by directly connecting the high pressure region at the front of a body to the lower pressure in the near wake using a venting duct; so far, it is able to establish a net mass flux into the wake. In particular, in aerodynamic applications it seems to be suitable to attain a global reduction of the drag of a body moving in a fluid and a reduction of turbulence levels by means of a global modification of the body wake. Velocity field investigations using Particle Image Velocimetry measurements and numerical Reynolds averaged code are employed at moderately high Reynolds numbers to clarify the effectiveness of drag reduction on a vented bluff body. The numerical and experimental results agree qualitatively, but the amount of reduction for the vented body (about 10%) is underestimated numerically. Direct balance measurements are used for comparisons.