Calibration of Frequency-Dependent Wave Speed and Attenuation in Water Pipes Using a Dual-Sensor and Paired-IRF Approach

The propagation of pressure waves in water pipes is frequency dependent, which leads to these waves experiencing a frequency-dependent wave speed and attenuation, resulting in wave dissipation and dispersion. The effect is much more significant and complex in plastic pipes than in metal pipes, which makes most wave-based pipe condition assessment techniques ineffective for plastic pipes. In this paper, a new technique is developed to calibrate the frequency-dependent wave speed and attenuation for pressurized water pipes. Persistent hydraulic waves induced by a side-discharge valve are used as excitation. Pressure responses are measured using two pressure sensors, and a paired-impulse response function (paired-IRF) is determined through a deconvolution process. The transfer function between the two sensors is determined using the main spike in the paired-IRF trace, which contains the information on the wave propagation characteristics. The frequency-dependent wave speed and attenuation are then derived from the transfer function. The proposed new technique is validated by both numerical simulations and laboratory experiments. Three pipe configurations are considered in the experiments: (1) a high-density polyethylene (HDPE) pipe in the air; (2) an HDPE pipe buried in sand; and (3) a copper pipe in the air. The frequency-dependent wave speed and attenuation are calibrated for all three configurations and the results are distinctive from each other.