An analytical amplitude model for negative pressure waves in gaseous media

Abstract The negative pressure wave propagation method is an established Structural Health Monitoring (SHM) technique to locate leakages and defects in pipelines. The amplitude of negative pressure waves can be exploited to obtain information about the severity of the damage (e.g. leak flow rate and leak area) and are useful to determine the smallest detectable leakage flow rate of the negative pressure wave method. The current manuscript proposes an analytical amplitude model of negative pressure waves in gaseous media. The isentropic fluid equations that represent the leak phenomena are combined with acoustical equations expressing the generation of the negative pressure waves. The presented model has been experimentally validated over a broad range of pressurization cases, gaseous media, leak sizes and pipe diameter. The derivation of the model provides insight in the physics behind the occurring phenomenon while the model reveals all parameters affecting the negative pressure wave amplitude. It is derived that, depending on the pressurization type, a different formulation has to be used to predict the amplitude of the negative pressure waves. The amplitude model is, in view of its applications, both presented in function of the leakage flow rate as well as in function geometrical size of the leak.