Spectral analysis of wall-pressure fluctuations in turbulent two-phase flow

A closed two-phase flow loop system was designed and constructed to measure the spectral characteristics of wall pressure such as rms values, power spectral density, and axial-lateral cross correlations. In this loop, the two-phase flow entered a straight run of smooth plastic pipeline (PVC) having an inside diameter of 20.32 cm (8 in.), achieving at the test section a maximum Reynolds number in the order of 2 x 106 on a liquid basis. Measurements of the wall-pressure fluctuations in a turbulent dispersed two-phase flow were conducted using miniature semiconductor pressure transducers mounted flush with the internal surface of the rigid thick-walled metal pipe working test section. Narrow-band spatial correlations were obtained over different center band frequencies ranging from 56.22--891.24 Hz and flow velocities at liquid Reynold's number of 0.819 x 106 to 2.0878 x 106. Lower values of the mixture velocity and the intensity of the pressure fluctuations were observed for high void fraction flows. In general, two-phase flow wall-pressure fluctuations were characterized by low-amplitude frequency spectra. Axial and lateral two-phase flow correlations have shown dependence upon the flow quality (volumetric mixing ratio) and Strouhal number. Two-phase flow wall-pressure field convection showed an increase at higher two-phase flow mixing ratio. The lateral microscale of turbulence was found to be approximately five times that of the axial direction