Measurement & Modelling of Turbulent Length Scales in Jet Flows

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• John Fitzpatrick, Trinity College, Dublin
• Thursday 19 February 2009, 13:30-14:30
• Lecture Room 6, Engineering Department.

If you have a question about this talk, please contact kag1000.

The statistical properties of turbulent jet flows form the basis for noise prediction methodologies, particularly those based on the acoustic analogy approach. In addition to the time averaged parameters of velocity and the variance of the unsteady parameters of velocity, shear stress and kinetic energy, the spatio-temporal properties of length and time scale are important as these give information on the convection and dissipation of the turbulence. More recently, the use of frequency dependent integral scales have resulted in improvements in noise predictions. It is shown how frequency dependent values for the two-point turbulent properties are determined using a coherence function approach. The results for the length scales and the convection velocities are derived from multi-point Laser Doppler Velocimetry (LDV) and Hot-Wire Anemometry (HWA) measurements for a range of jet flow conditions including the effect of Mach number, temperature ratio and nozzle geometry. Empirical models for these properties are proposed and compared with the experimental data. The effect of modelling the frequency dependence on noise predictions is briefly examined.

This talk is part of the Engineering Department Energy, Fluids and Thermo seminars series.

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