The Wavelet Analysis On The Relation Of The Fluctuating Wall Pressure And Turbulent Coherent Structures

Using the pressure transducer of high accuracy and the Hot Wire/Film Anemometer of double sensors, synchronous measurements of velocity and wall pressure of the turbulent boundary layer on a flat plate have been carried out in a wind tunnel and a water channel. Applying the maximum energy criterion, the wavelet analysis is adopted to ascertain the relation between the scales of the coherent structures and fluctuating wall pressure of the turbulent boundary layer. The results show that the time scale corresponding to the peak value of wavelet spectra of fluctuating wall pressure is much closed to the characteristic time scale of coherent structure of the turbulent boundary layer. Therefore the analysis results of time scale of fluctuating wall pressure can be used to indicate the time features of coherent structure of the turbulent boundary layer. The momentum thickness Reynolds number Re_θare 1241, 1635. The near-wall coherent structures in the turbulent boundary layer is the most significance in wall shear turbulent flows. The traditional Fourier transform can't recognize unsteady signal of coherent structures. Wavelet transform is much more appropriate to make localized analysis at any position of a time sequence for a certain frequency range. The eddy structure can be obtained by decomposing the experimental data with scale varying, finite energy containing and localized wavelet components, which is particularly important to the turbulence physics. Here the complex Morlet wavelet has been used, which has better resolution for different scales and is appropriate to express the time and space varying characteristics of coherent structures. A device for calibrating hot film sensors in water has been designed and made. Advanced experimental techniques are applied in this work and a mistake in the instruction manual of TSI for calibration has been corrected.