Numerical investigation on bubble dynamics and pressure wavelet characteristics of the four-opening seismic airgun

The seismic sources generated by airguns have long been used for the marine resources and seabed geological exploration. This work investigates seismic bubble dynamics and pressure wavelet features using detailed numerical simulations of full-scale, four-port airguns within the OpenFOAM framework. The Navier–Stokes equations are spatially discretized via the finite volume method, with the volume of fluid method employed to capture the evolving bubble interface. Gas emission from the ports initially creates four separate bubbles, which subsequently merge into a single, larger bubble. Some flow details including coalescence features of the bubbles and mass throttling of the opening port are discussed. Meanwhile, it is observed that the coherent interaction induced by the four expanding bubbles can suppress the initial pressure wavelet attenuation, which might provide an innovative way to optimize the performance of the single four-opening airgun. In addition, the results from our studies on airguns with different configurations indicate that the airgun parameters including firing pressure, opening size and form, airgun volume are primary to the pressure wavelet characteristics, though some minor details outside the airgun wall can slightly affect the bubble evolution.