Design and characterisation of a quiet, low turbulence open jet blow down wind tunnel in ISVR

Abstract

This technical report presents the design of an open-jet, blow-down wind tunnel that was newly commissioned in the anechoic chamber at the ISVR, University of Southampton, UK. This wind tunnel is intended for the measurement of airfoil trailing edge self-noise but can be extended to other aeroacoustic applications. With the primary objectives of achieving acoustically quiet and low turbulence air jet up to 120m/s through a 150mm x 450mm nozzle, several novel noise and flow control techniques were implemented in the design. Both the acoustical and aerodynamic performances of the open jet wind tunnel were calibrated in detail after its fabrication. It is found that the background noise of the facility is adequately low for a wide range of exit jet velocity. The potential core of the free jet is characterised by a low turbulence level of about 0.1%. A benchmark test by submerging a NACA0012 airfoil with a tripped boundary layer at zero angle of attack into the potential core of the free jet was carried out. It was confirmed that the radiating
aerofoil trailing edge self-noise has levels significantly above the rig noise over a wide range of frequencies. The low noise and low turbulence characteristics of this open jet wind tunnel are comparable to the best facilities in the world, and is
believed to be the first of its kind in the UK.

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