测量每年海底渗漏释放到海洋水体及大气中的具有温室效应的甲烷的量具有重要的科学意义。文章提出了测量前调整气泡状态并用透射声波波形-幅度参数测量渗漏气泡流量的新方法。通过空间频谱分析得出声波测量窗口高度小于气泡流每秒上升的距离时, 文章所设计的声波传感系统可以有效地测量气泡流速。根据求解声波方程的Born近似方法得出了气泡直径与测量声波波长的关系, 该关系是确定测量系统结构参数的依据。实验表明, 采用蜂窝芯板为主的结构可把气泡调整为直径小于3mm且空间分布均匀的状态, 气泡流速测量精度可达±2%, 透射声波幅度与截面含气率有近线性关系; 初步验证了气泡流量测量方法的可行性。
Observations of seabed bubbles of methane, an important greenhouse gas, at a natural marine hydrocarbon seep to evaluate the global methane budget per year is very important. The objective of this paper is to develop a new approach, in which the configuration and distribution of bubbles are adjusted before flow measurement, to measure cold seepage flow on seafloor by the wave form-amplitude parameters of acoustic transmission. After the spectrum analysis we lead to the height of the measurement window through which acoustic wave transmits to the opposite wave transducer is less than the distance which bubbles go up pass per second. And the bubble speed can be effectively measured by using the acoustic sensing system designed under the proposed height of the measurement window in the paper. The relationship between the bubble diameter and the measured acoustic wavelength is obtained under the Born approximation. Diameters of bubbles become smaller than 3 mm after they go through the honeycomb-core board and other structure parts, and the distribution of bubble populations is uniform. Spatial frequency spectrum analysis is applied to establish the relationship between geometry parameters of the piezoelectric transducer and the motion of bubbles, and the measurement accuracy of bubble velocity is expected to ± 2%. The nearly linear relationship between the amplitude of sound transmission and the gas bubble flow has been established through the experiment. It turns out to be an effective method of measuring the bubble flow.
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