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DRAG REDUCTION BY DIMPLES? − A COMPLEMENTARY EXPERIMENTAL/NUMERICAL INVESTIGATION −

Hermann Lienhart
Institute of Fluid Mechanics (LSTM) Friedrich-Alexander University Erlangen-Nuremberg, Cauerstr. 4 D-91058 Erlangen-Nuremberg, Germany

Michael Breuer
Institute of Fluid Mechanics, University of Erlangen-Nurnberg, Cauerstr. 4 D−91058 Erlangen, Germany

Cagatay Koksoy
LSTM-Erlangen, Institute of Fluid Mechanics, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Cauerstrasse 4, D-91058 Erlangen, Germany

Abstract

The paper is concerned with experimental and numerical investigations on the turbulent flow over dimpled surfaces. Shallow dimples distributed regularly over the wall of a plane channel with large aspect ratio are used to study their effect on the friction drag. The resulting pressure drop in the channel was measured for smooth and dimpled walls. In addition to these investigations on internal flows, an external flow study was performed and boundary layer profiles were measured using a Pitot tube rake. Complementary to the measurements, direct numerical simulations for the internal flow configuration with and without dimples were carried out for two different grid resolutions and analyzed in detail. The objective is to clarify and prove or disprove the effect of dimples on the skin friction drag.