The Role of Turbulent Dissipation for Flow Control of Near-Wall Turbulence.

One of the major goals of flow control is the reduction of energy consumption in wall bounded flows by minimizing the viscous drag. In the present work it is shown that the turbulent dissipation needs to be minimized in order to obtain energy savings. Analytical considerations lead to the conclusion that this can be achieved by forcing near-wall turbulence to an axisymmetric state. To confirm this finding direct numerical simulations were carried out in which the boundary conditions were such that near-wall fluctuations were forced towards axisymmetry. Additionally, a surface structure that minimizes turbulent dissipation at the wall was designed and tested experimentally. Both, numerical and experimental investigations yield significant drag reduction. [ABSTRACT FROM AUTHOR]