Suryanarayana, GK and Meier, GEA (1995) Effect of ventilation on the flowfield around a sphere. Experiments in Fluids, 19 (2). pp. 78-88. ISSN 0723-4864
![]() |
PDF
suryanarayana.pdf Download (1MB) |
![]() |
Indexer Terms (Generate index codes conversion from application/pdf to indexcodes)
indexcodes.txt Download (8kB) |
Abstract
The flowfield around a sphere with and without ventilation was investigated in a wind tunnel over a range of Reynolds numbers in an incompressible flow. At supercritical Re, the pressure drag of a sphere can be nearly nullified by venting only 2 percent of the frontal area of the sphere to the base through a smooth internal duct.The drag reduction is achieved by increased pressures in the separated flow region close to the base. At high Re, the vent flow breaks through the near wake and brings about symmetry in the global flowfield. When the internal shear is increased by using a rough internal duct, the base pressure is unchanged, but the external flow is accelerated to velocities beyond that achieved by the potential flow around the basic sphere. The findings can be explained by a flow model in which the near wake is aerodynamically streamlined by a pair of counterrotating vortex rings at the base. A roughness element can be made to partially destroy the vortex system at the base and result in a steady asymmetric wake. A 1.2 mm diameter wire placed at 70 deg was found to overtrip the boundary layer and completely destroy the vortex system. Simultaneously, the turbulent separation is advanced and the drag increased.
Item Type: | Article |
---|---|
Additional Information: | Copy right for this article belongs to Springer-Verlag |
Uncontrolled Keywords: | Flow distribution;Spheres; Ventilation;Wind-tunnel-tests; Incompressible flow;Drag-reduction;Reynolds number;Air-flow; Bluff-bodies;Boundary-layer-flow |
Subjects: | ENGINEERING > Fluid Mechanics and Thermodynamics |
Depositing User: | M/S ICAST NAL |
Date Deposited: | 31 Dec 2007 |
Last Modified: | 07 Jun 2010 10:32 |
URI: | http://nal-ir.nal.res.in/id/eprint/4361 |
Actions (login required)
![]() |
View Item |