A survey of the turbulent drag reduction using passive devices
Abstract
Turbulent skin friction drag reduction using large eddy break-up devices (LEBU) and riblets is reviewed. Drag reductions of turbulent boundary layers are observed from riblets whose height and width range from 10 to 100 and 10 to 200 viscous lengths, respectively; the maximum reduction is obtained from riblets with cusped peaks and semicircular valleys of 15 viscous lengths in height and width. Drag reduction of turbulent boundary layers using riblets is due to the local increase of the effective kinematic viscosity in the buffer layer caused by forcing the fluid to flow across the ridges of riblets. An optimum configuration of LEBU consists of 2 thin flat plates with lengths, heights, and spacing being 1, 0.8, and 5 to 8 boundary layer thicknesses, respectively. Turbulent drag reduction using LEBU is due to the passive and dynamic effect of the momentum deficit region of the wake created by the devices suppressing turbulent energy production.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- July 1984
- Bibcode:
- 1984STIN...8520268C
- Keywords:
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- Drag Reduction;
- Friction Drag;
- High Reynolds Number;
- Riblets;
- Turbulent Boundary Layer;
- Boundary Layer Flow;
- Eddy Viscosity;
- Flat Plates;
- Grooves;
- Fluid Mechanics and Heat Transfer