Issue title: International Conference on Optical Technology
and Image Processing in Fluid, Thermal, and Combustion Flow, Yokohama, Japan,
December 1998
Affiliations: Research Associate, Department of Mechanical
Engineering,Florida A University and Florida State University, Tallahassee,
Florida 32310, USA | Don Fuqua Eminent Scholar and Professor,Department of
Mechanical Engineering, Florida A University and Florida State University,
Tallahassee, Florida 32310, USA | Professor, Department of Mechanical Engineering,
Florida A University and Florida State University, Tallahassee, Florida
32310, USA
Abstract: The characteristics of supersonic impinging jets are investigated
using Particle Image Velocimetry (PIV). The purpose of the experiments is to
understand the jet induced forces on STOVL aircraft while hovering close to the
ground. For this purpose, a large diameter circular plate was attached at the
nozzle exit. The oscillations of the impinging jet generated due to a feedback
loop are captured in the PIV images. The instantaneous velocity field
measurements are used to describe flow characteristics of the impinging jet.
The important flow features such as oscillating shock waves, slipstream shear
layers and large scale structures are captured clearly by the PIV. The presence
of large scale structures in the impinging jet induced high entrainment
velocity in the near hydrodynamic field, which resulted in lift plate suction
pressures. A passive control device is used to interfere with the acoustic
waves travelling in the ambient medium to suppress the feedback loop. As a
consequence, the large scale vortical structures disappeared completely leading
to a corresponding reduction in the entrainment.
Keywords: supersonic impinging jets, PIV, large scale structures, convection velocity, feedback control
