Self Organization in Turbulent Boundary Layer and the Control by Suction

Abstract

The turbulent boundary layer is regarded as a thermodynamically non-equilibrium flow field with dominant dissipative processes. From the thermodynamics of irreversible processes, the rate of entropy production should be minimized in the flow field. Fluiddynamically, some self-organizing mechanism must exit so as to control the energy dissipation respond to the demand of thermodynamics. The first part of the present paper is an extension of the previous one (Aihara, Y.: J. Fluid Mech., 214 (1990)), dealing in more detail with the experimental investigation of the establishment of self-organization in the turbulent boundary layer. The second part of the paper discusses the control of turbulence by means of suction. Suction is considered an effective means of reducing the induced negative normal pressure gradient by turbulence. The experimental results involving the change of the behaviour of turbulence give us a deeper insight into the flow field, especially through the change in Reynolds stress, and at the same time provide useful information for effective turbulence control by using a small amount of suction.