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Thermophysics and Aeromechanics

2014 year, number 4

Formation of the turbulent boundary layer at air blowing through a wall with an abrupt change in boundary conditions

V.I. Kornilov and A.V. Boiko
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
E-mail: kornilov@itam.nsc.ru
Keywords: experiment, incompressible turbulent boundary layer, flat plate, air blowing, friction, abrupt change in the boundary conditions

Abstract

Development of an incompressible turbulent boundary layer with air blowing through a finely perforated flat surface, consisting of a permeable region and impermeable region behind, was studied experimentally. The mass flow rate of injected air Q per an area unit was varied from 0 to 0.2 (kg/s)/m2. Detailed data about the internal structure of the boundary layer in the flow region, characterized by an abrupt change in the flow conditions at the boundary of permeable and impermeable regions, were obtained. A consistent decrease in the local values of skin friction coefficient along a permeable sample and with an increase in the values of Q, reaching 90% at maximal Q, is shown. The role of the flow region behind the zone with an abrupt change in the boundary conditions, essential from the viewpoint of skin friction reduction, is revealed.