Bluff-body drag reduction by passive ventilation

Suryanarayana, GK and Pauer, Henning and Meier, GEA (1993) Bluff-body drag reduction by passive ventilation. Experiments in Fluids, 16. pp. 73-81.

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Abstract

The drag of a sphere at high Re can be reduced to more13; than half its value by passive ventilation from the stagnation region to the base. Simultaneously, the flow field around the base is stabilized and made symmetric, leading to reduction of unsteady aerodynamic forces. At high Kt;, the vent flow breaks through the dead water region associated with the near wake and aerodynamically13; streamlines the base. The streamlining is done by virtue of a basevortex-ring beyond the point of turbulent boundary layer separation.A mean flow model for the flow around the vented sphere is proposed.13; Smoke flow visualized on a laser light screen placed at two diameters behind the base of the sphere shows the effectiveness of themethod in suppressing the flow oscillations.The drag reduction achieved is very sensitive to the quality of the external surface and relatively insensitive to disturbances in the internal flow. Surface roughness or boundary layer tripping wire on the external flow can completely offset the benefit obtained.

Item Type:	Article
Uncontrolled Keywords:	Bluff-body;Drag reduction; Passive ventilation
Subjects:	ENGINEERING > Fluid Mechanics and Thermodynamics
Depositing User:	Mr. N A
Date Deposited:	27 Jun 2006
Last Modified:	18 Aug 2015 04:22
URI:	http://nal-ir.nal.res.in/id/eprint/1740

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