  During the operation of a seismic airgun source, a certain amount of
compressed high-pressure air is released from the airgun chamber into the
surrounding water, generating an expanding toroidal bubble attached to the
airgun-body. The subsequent oscillations of the bubble generate low-frequency
pressure waves, which are used to map the ocean subbottom, e.g., to locate oil
and gas reserves. The bubble dynamic behavior and the emitted pressure waves
are inevitably influenced by the airgun-body. However, the bubble-airgun-body
interaction is far from well understood. This paper investigates the strong
interaction between a long cylinder and an attached toroidal bubble via
hundreds of boundary integral simulations, aiming to provide new physical
insights for airgun-bubble dynamics. Firstly, the overall physical phenomena
are discussed and three types of bubble collapse patterns are identified,
namely (i) upward jetting due to gravity, (ii) annular jet toward the cylinder
body and (iii) weak/no jet. Thereafter, we investigate the effects of the
cylinder radius, initial bubble pressure and Froude number on the bubble
oscillation period and the pressure wave induced by the bubble. At last, the
impact of a cylinder on a Sercel type airgun-bubble is discussed with a
particular focus on the spectrum of the pressure waves.
