Experimental investigation of the wake behind a solid disk

Technical Report · Wed Dec 01 04:00:00 EST 1993

OSTI ID:10192462

Balligand, H; Higuchi, Hiroshi ^[1]

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1. Syracuse Univ., NY (United States). Dept. of Mechanical, Aerospace and Mfg. Engineering

The flow past a solid circular disk placed in time-dependent approaching stream velocity was investigated experimentally. The model was near-impulsively started from rest and moved at a constant speed. The wake behind the disk remained axisymmetric when the disk was traversed for a short distance. The scaling effect of varying the acceleration rate and the subsequent constant velocity on the wake evolution was investigated by detailed flow visualizations. The drag measurement indicated an initial maximum force dependent on the acceleration rate before it decreased toward the quasi-steady value. The model was subsequently decelerated at various rates, either to rest or to a second constant velocity. The wake overtook the disk in most cases depending of the values of both deceleration rate and velocity ratio. The force measurement showed that the drag acting on the disk became negative shortly after the onset of deceleration and reached its most negative value approximately at the end of the deceleration. The peak negative drag correlated with the deceleration rate. During the deceleration to a second velocity the drag became negative even when the vortex structure remained downstream of the disk. When the disk was subjected to constant speeds for a prolonged time, onset of asymmetry of the vortex structure occurred, eventually leading to a three-dimensional wake. Finally, the wake behind the disk was compared with the two-dimensional counterpart, using a rectangular flat plate. One of the prime motivations for studying the wake behind bluff bodies during acceleration and deceleration phases is to achieve a better understanding of the unsteady flow phenomena associated with the opening and early phase of deceleration of a parachute.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States); Syracuse Univ., NY (United States). Dept. of Mechanical, Aerospace and Mfg. Engineering
• Sponsoring Organization: USDOE, Washington, DC (United States); Department of Defense, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 10192462
• Report Number(s): SAND--90-7083; ON: DE95002317; BR: GB0103012; CNN: N62269-92-C-0229
• Country of Publication: United States
• Language: English

Related Subjects

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
450000
AERODYNAMICS
COMPARATIVE EVALUATIONS
DRAG
EXPERIMENTAL DATA
MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
PARACHUTES
TEST FACILITIES
UNSTEADY FLOW
VORTICES