Air Blowing into Boundary Layer of a Flat Plate with Length-Dependent Permeability

Read more A generalized analysis of the results of numerical and experimental studies of air blowing into a turbulent boundary layer through finely perforated surface consisting of alternating permeable and impermeable sections of varying length providing a sudden change in the flow conditions at the boundaries of these sections is presented. The air blowing coefficient C_b determined by the mass flow rate per unit area of the active perforated sample varied in the range from 0 to 0.008. It is shown that as C_b grows, the maximum reduction in the mean surface skin-friction coefficient C_F, which is the value through the permeable area of perforated sample, reaches about 65 %. When keeping the equal mass flow rate Q for all tested combinations, the mean skin-friction coefficient remains constant, independent of geometrical parameters of permeable and impermeable sections. Increasing the length of the last permeable section leads to the growth of relaxation region which is characterized by the reduced skin friction values on the impermeable part of the flat plate.

Keywords:
flat plate, permeable and impermeable sections, air blowing, turbulent boundary layer, skin friction.
УДК 532.526.4 + 532.546.6 + 532.526.72

Air Blowing into Boundary Layer of a Flat Plate with Length-Dependent Permeability