FLAT-PLATE SKIN FRICTION UNDER THE CONDITIONS OF AIR BLOWING THROUGH A WALL WITH INTERMITTENT IN LENGTH PERMEABILITY

Possibility of turbulent skin-friction reduction in an incompressible boundary layer of a flat plate with air blowing through a microperforated surface consisting of alternating permeable and impermeable sections was studied experimentally and computationally. The mass flow rate of the air per unit area was varied in the range from 0 to 0.0709 kg/s/m2 , which corresponds to the maximum blowing coefficient equal to 0.00344. A consistent reduction of the local skin-friction values along the chord of the microperforated insert was found, the reduction achieving nearly 70 % at the end of the last active blowing sections, except the impermeable surface sections demonstrating, on the contrary, the skin friction increase: the longer section, the higher skin friction.

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

FLAT-PLATE SKIN FRICTION UNDER THE CONDITIONS OF AIR BLOWING THROUGH A WALL WITH INTERMITTENT IN LENGTH PERMEABILITY