Effect of static pressure on friction reduction at gas saturation on turbulent boundary layer

Abstract

The effect of static pressure on regularities of turbulent friction reduction by means of a bubble method at gas injection through a permeable wall has been experimentally studied in this work. The flat model (955 mm long) with gas saturation of the turbulent boundary layer was tested at the hydrodynamic setup of the Institute of Mechanics of Moscow State University within the ranges of flow velocity U = (4-11) m/s and static pressure P = (10-200) kPa. The Reynolds number along the plate varied within the range of (3 - 8)×106. Tangential stresses on the plate surface (plate on bottom) were measured directly by the “floating wall” sensor on tensoscales, located at the distance of 50 mm behind the porous coating. This paper presents data on local friction on the plate vs. gas flow rate, flow velocity and static pressure. It is shown that reduction of local friction at gas saturation of a turbulent boundary layer depends essentially on the static pressure, which should be taken into account by integral evaluation of method’s efficiency, considering energy losses for gas blowing through the permeable coating.