Abstract
Wave propagation in liquid-filled pipes was investigated using time- and frequency-domain techniques. Water- and ethanol-filled copper and PVC pipes having inner diameters of 1.44 and 1.19 cm, and wall thicknesses of 0.0686 and 0.208 cm, respectively, were driven with tone bursts from a submerged hydrophone, and the resultant acoustic pressures in the liquid were measured. Group velocities in the copper pipe were observed to decrease with increasing frequency: velocities were 1124 m/s at 10 kHz and 1039 m/s at 50 kHz in water and 1052 m/s at 10 kHz and 902 m/s at 40 kHz in ethanol. Propagation in the PVC pipe was significantly slower, e.g., the estimated water group velocity at 10 kHz was 593 m/s. The estimated group velocities were then compared to those predicted by an acoustic transmission line model of the pipes. The predicted group velocities were within 13% of the estimated values for the copper tube for both liquids. The pipe systems were also excited with Gaussian noise, and exhibited bands of low spectral energy that could be attributed to the transverse resonances of the tube walls. The model predicted the upper frequency limit of these bands to within 5% of measured values.
Published Version
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