Modelling of seismic airgun bubble dynamics and pressure field using the Gilmore equation with additional damping factors

Seismic airguns are commonly used in geophysical exploration. More recently, they are also being used as an alternative to underwater explosions for the shock testing of defence vessels. The study of the dynamics of the bubble produced by a seismic airgun is beneficial in understanding the resultant pressure field and shockwave. The Rayleigh–Plesset and Gilmore equations for modelling spherical bubble dynamics are compared for the expansion of an initially highly pressurised gas bubble. The relationship between initial gas pressure and both the first maximum bubble radius and the first period of oscillation are presented. The separate contributions due to the presence of the airgun body, mass throttling, effective viscosity and heat diffusion to the first maximum radius and period are modelled and discussed. The effects of evaporation and condensation at the bubble wall are also considered. Gilmore's model is used to predict the radiated pressure wave of the new bubble model. The results are in fair agreement with measured data collected from full scale airgun trials.