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Richardson M.A.,Cranfield University | Richardson M.A.,Sensors Group | Saddington A.J.,Cranfield University | Saddington A.J.,Aeromechanical Systems Group | And 7 more authors.
AIAA Journal | Year: 2011

The possible use of a simple methodology to study laser-beam propagation in a transonic flow and observe the aero-optical effects was investigated. The experimental setup consisted the DIRCM pod, the wind tunnel, and the image acquisition system. A steady-state CFD model of the experiment was developed using a commercial finite volume code. The numerical model found that the blockage caused by the pod results in some local supersonic flow with a consequent normal shock downstream. The main sources of potential discrepancy between the predicted beam wander and the measured values are found. These include the numerical model is limited in its resolution and the laser beam as it left the wind tunnel passed through a 10-mm-thick piece of optical glass and it was not possible to determine the effect this had on the laser path. The third source is that the simulation assumes that the inflow conditions to the wind tunnel are symmetrical about the x-z plane.

Thangamani V.,Cranfield University | Thangamani V.,Aeromechanical Systems Group | Knowles K.,Cranfield University | Knowles K.,Aeromechanical Systems Group | And 2 more authors.
Journal of Aircraft | Year: 2014

The effects of scaling on cavity oscillations and control have been studied by measuring the unsteady pressure on the floor of three cavities of different scales. The cavities have a length-to-depth ratio of 5 and a length-to-width ratio of 2, and the corresponding linear dimensions are in the ratio 0.5:1:2. The experiments were conducted with clean cavities and cavities fitted with leading-edge sawtooth spoilers so as to study the influence of scaling on clean cavities as well as the effectiveness of the passive control method on different sized cavities. The results showed significant variation of certain spectral characteristics of the clean cavities. The control effectiveness of the spoilers also showed variations with a change in scale of the model. It is recommended that, before implementing a passive control device for practical applications, the device should be tested in the possible range of cavity length-to-boundary- layer-thickness ratio (L/δ) that can be experienced in actual flight. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Saddington A.J.,Cranfield University | Saddington A.J.,Aeromechanical Systems Group | Knowles K.,Cranfield University | Knowles K.,Head of Aeromechanical Systems Group
Journal of Aircraft | Year: 2013

An experimental study was conducted to measure some of the turbulence characteristics of a twin-jet fountain-upwash flow using nonintrusive particle image velocimetry. The results show that the point at which the wall jets meet is an area of large horizontal turbulent stress. The largest values of vertical turbulent stress were found in the fountain-formation region. In the wall-jet interaction region the flow was shown to be anisotropic with values of V rms/Urms reaching 2.9. Turbulent-kinetic-energy production by normal stresses was concentrated in the wall-jet interaction region whereas the fountain-formation region was the source of turbulent-kinetic energy production by shear stresses.

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