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Presenter: Dr. Peter Oshkai - Department of Mechanical Engineering and Mechanics, Lehigh University
Supervisor:

Date: Thu, February 27, 2003
Time: 11:00:00 - 00:00:00
Place: EOW 430

ABSTRACT

Abstract:

Advanced imaging techniques are employed in order to gain insight into a variety of complex flows. Applications include maneuverability and unsteady loading of high-performance fighter aircraft, loading and vibration of towing cables and oil drilling risers in the ocean environment, unsteady loading and erosion of beds of rivers and coastal regions, and noise generation and vibration in nuclear propulsion systems and large-scale power plants.

This seminar will focus on flow past surface irregularities in components of propulsion systems, as well as in valve and pipe systems in large-scale power plants, which can give rise to intolerable noise and, in certain situations, destructive vibrations. Recent advances using quantitative imaging in our laboratories have revealed the first experimental patterns of vortices due to flow-acoustic coupling, and how they can serve as an origin of noise and vibration.

Fully turbulent inflow past an irregularity, which was simulated by a shallow cavity, was investigated for the case where the axisymmetric cavity was mounted in a pipe. A technique of high-image-density particle image velocimetry was employed in conjunction with a special test section, which allows effective laser illumination and digital acquisition of patterns of particles in the flow. These patterns led to wholefield images of velocity, vorticity and streamline topology, as well as hydrodynamic contributions to the acoustic power integral, which were evaluated to provide insight into the flow physics during tone generation. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary for maintaining a flow tone.