Bubble dynamics of a seismic airgun

• Published in: Experimental thermal and fluid science Vol. 55; pp. 228 - 238
• Main Authors: de Graaf, K.L., Brandner, P.A., Penesis, I.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.05.2014; Elsevier
• Subjects: Applied geophysics; Bubble dynamics; Bubbles; Collapse; Dynamics; Earth sciences; Earth, ocean, space; Emittance; Exact sciences and technology; Internal geophysics; Mathematical analysis; Photography; Rayleigh–Taylor Instability; Seismic airgun; Signatures; Tanks; Rayleigh–Taylor Instability; Bubble dynamics; Seismic airgun; interfaces; pressure; velocity; seismic surveys; dynamics; Rayleigh―Taylor Instability; air guns; mathematical equations; imagery; instability; growth; bubbles; photography
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2014.02.018

•Development of a lab scale seismic airgun of 100bar maximum firing pressure.•Bubble physics including RTI captured with low- and high-speed photography.•Formation of re-entrant jet towards airgun body and away from nearby free surface.•Experimental data compared with modified Gilmore equation with favourable agreement. The dynamics of the bubble generated by a four port model-scale seismic airgun in an open top tank are investigated. The airgun is fired at 50 and 100bar and bubble images are captured with low- and high-speed photography. Forward- and back-lit photography allows close observation of the phenomena at the gas–water interface, and measurement of the radial growth, respectively. The development of the Rayleigh–Taylor Instability on the bubble’s surface is identified. Field pressure measurements, synchronised in time with the radial bubble growth, are presented, and features of the emitted pressure signature are associated with the physical bubble dynamics. The experimental data is compared with an analytical prediction based on the Gilmore equation and good agreement is found for bubble radius, bubble period and the pressure pulse emitted at bubble collapse. The initial shock wave and first maximum velocity were over-predicted by this method.