MOVING SURFACE BOUNDARY-LAYER CONTROL AS APPLIED TO 2-DIMENSIONAL AND 3-DIMENSIONAL BLUFF-BODIES

The concept of moving surface boundary-layer control has proved quite successful in increasing lift and delaying stall of slender bodies such as airfoil sections. This paper assesses the effectiveness of the concept in reducing drag of bluff bodies such as a two-dimensional flat plate at large angles of attack, rectangular prisms and three-dimensional models of trucks through an extensive wind tunnel test program. Results suggest that injection of momentum through moving surfaces, achieved here by the introduction of bearing-mounted, motor-driven, hollow cylinders, can significantly delay separation of the boundary layer and reduce the pressure drag. A flow visualization study, conducted in a closed-circuit water tunnel using slit lighting and polyvinylchloride tracer particles, complements the wind tunnel tests. It shows, rather dramatically, the effectiveness of the moving surface boundary-layer control.