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Acoustics

 Jet aeroacoustics using large eddy simulation (LES)

Jet aeroacoustics modelled with LES

 

Credit: Iffi Naqavi, Zhong-Nan Wang and James Tyacke

 

Jet noise is an important issue for aerospace industry. It is imperative to predict the flow and associated noise accurately, in order to control and reduce the jet noise emission. Large eddy simulation is used to predict the flow and noise of realistic nozzle geometries. Simulations have been performed for nozzles with increasing geometrical complexities as shown in the above figure. Single stream and coaxial nozzles are used to validate the numerical methods for flow and far-field noise predictions. A chevron nozzle and an installed jet with realistic engine features have been simulated. These features include wing, pylon, fan and internal geometry of the by-pass duct.


 

 Vertical axis wind turbines

 VAWT setup

 

VAWT beamform

Credit: Charlie Pearson

Top: VAWT model and its experimental installation. Blades have 536mm span and 55mm chord, while the turbine radius is 530mm. 

Bottom: Results of acoustic array measurements on a vertical-axis wind-turbine model in the Markham wind tunnel.  Rotation rate was 718rpm, with a flow speed of 6.6m/s, giving a tip-speed ratio of 3. Contours plot equivalent monopole source power (in dB), for the 192Hz frequency band centred on 1530Hz.

On the far left are diagrams indicating the blade orientations for each row, where the sensor array would be located below the VAWT as shown.  The two columns correspond to different configurations: without (left) and with (right) boundary-layer trips installed.   See: Pearson (2014).