The stabilizing effect of surface embedded grooves on the laminar boundary layer development is studied experimentally in the inlet region of a channel flow. The stabilization is thought to be due to the ability of a grooved surface to suppress the velocity fluctuations in the spanwise direction on a restricted portion of the wetted surface which prevents vorticity development close to the solid surface. This control strategy is implemented in a groove-modified channel flow in which the front part has a grooved surface structure. The results of pressure drop measurements indicate that grooved surfaces can effectively delay laminar to turbulence transition, leading to significant reduction of the viscous drag. In the rear flat part of the groove-modified channel test section, a maximum drag reduction of DR approx- 35percent was measured. This corresponds to an overall drag reduction of DR approx- 16percent at a length Reynolds number of Re_(x) approx- 10~(6). The drag reduction effect persisted in a narrow range of flow velocities and for the reported experimental conditions corresponds to groove dimensions between 1.5 and 2 viscous length-scales.
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