Modification of turbulent flow using distributed transpiration

The long-term objective of this investigation is the development of techniques for re-arrangement and control of turbulent flows by using a suitably roughened wall. As a preliminary step towards this goal, we describe the analysis of the turbulent flow in a plane channel modified by a sinusoidal distribution of suction and blowing at the wall with zero net mass flux. The tool by which the whole investigation is carried out is the Direct Numerical Simulation of the incompressible Navier-Stokes equations. The fundamental result of this preliminary study is that the transpiration wavelength has a dramatic effect on the modification induced on the turbulent flow by the wall transpiration. Large wavelengths produce very high increases in the frictional drag, whereas smaller wavelengths can lead to a friction decrease of up to 4%-5%. © 2005 CASI.