Abstract:Air bubbless in water increase the compressibility several orders of magnitude above that in air-free water, thereby greatly reducing the velocity and increasing attenuation of acoustic waves, published experimental and theoretical results demonstrate that these quantities are dependent principally upon frequency, bubble size, and fractional volume of air. Below the bubble resonant frequency and in the frequency range of marine energy sources, acoustic wave velocity is essentially independent of frequency and bubble radius, being well below the velocity in air-free water. In this frequency range,. attenuation increased with increasing frequency, decreasing bubble radius, and increasing fractional air volume. A field experiment consisted of hydrophone recordings in a pond, 25 ft in depth, of signals transmitted through air bubble curtains from a water gun source. The air curtains issued from one to 13 pipes(20 ft in length and spaced at 2.67 ft intervals). Air pressures used in the pipes were 15, 25, and 50 psi. Length and complexity of the signals indicate that reverberations occurred to an increasing extent as the number of consecutive air curtains was increased. Analysis of the first pulse in the recorded signals, after approximate removal of hydrophone and recorder response, indicates that the reverberations occur principally in the air-free corridors between air curtains. This pulse broadens and its peak amplitude is delayed linearly as the number of successive air curtains is increased. The peak amplitude is decreased substantially by the first air stream and thereafter remains between 0.1 and 0, 2 of the amplitude without air curtains. The time delay increases measurably, whereas the amplitude appears insensitive to an increase in air pressure. Width of the air-free corridor, velocity in the air streams, and reflection coefficient at the air stream/corridor interface were determined, for each of the three air pressures, from signal onset times and delay time of the first pulse peak amplitude. The corridor width was approximately three times the air stream width and did not appear to vary with air pressure. Traveltime in the air stream, however, increased with air pressure and was from three to four times the traveltime in the corridor. Reflection coefficients ranged from about Q, 75 at 15 psi to 0.8 2 at 50 psi. These data were used to predict, successfully, times of multiple reflections between the outer interfaces of the outermost air curtains.
引用本文:
S. N. Domenico, 牛毓荃. 声波在水中气泡流内的传播[J]. 石油地球物理勘探, 1982, 17(2): 26-43.
S. N. Domenico. Acoustic wave propagation in air bubble streams in water. OGP, 1982, 17(2): 26-43.