基于水下滑翔机的湍流观测平台研究

Research on the Turbulence Observation Platform Based on Underwater Glider

海洋湍流混合过程对大洋热盐环流具有重要调控作用,因此海洋湍流混合特征量如湍动能耗散率等物理量的定量刻画,主要通过现场湍流观测来实现。为满足长期连续海洋湍流混合观测资料的迫切需求及打破国外的技术封锁,自行研制了基于水下滑翔机的湍流观测仪。为了测试滑翔机在小尺度湍流观测方面的可行性,将一个携带有剪切探头的湍流仪安装在滑翔机本体上,并在千岛湖进行了一系列的实验。滑翔机平台的主要噪声来源于浮力调节机构中的油泵,油泵会在接近剖面的底端时开启。三轴加速度谱在30 Hz左右有明显的谱峰,说明滑翔机油泵的振动频率应该是在30 Hz左右,在其他频率点上振动较小。由剖面下潜过程(开泵)的波数谱可知,开泵时虽然对湍流观测有影响,但是振动频率在波数空间中处于无效观测谱一侧,由此说明平台的振动对剪切信号影响很小。剪切探头测得的耗散率在10-7 W/kg量级上,且都与Nasymth理论谱吻合良好,验证了滑翔机在小尺度湍流观测方面的可行性。

The ocean turbulence mixing process plays an important role in regulating ocean thermohaline circulation, so the quantitative characterization of ocean turbulence mixing characteristic parameters, such as turbulent kinetic energy dissipation rate, is mainly implemented through on-site turbulence observation. To meet the urgent demand of long-term continuous information of ocean turbulence mixing observation and break foreign blockade on technologies, we have independently developed a turbulence observation instrument based on underwater glider. In order to test the feasibility of the underwater glider in small-scale turbulence observation,an instrument with shear probe was installed on the glider body and a series of experiments were conducted in the Qiandao Lake. The noise of the glider is mainly attributed to the action of oil pump used for the buoyancy mechanism, which starts when the glider approaches the bottom of the profile. The spectrum of three axis acceleration has an obvious peak around 30 Hz, which means that the vibration frequency of the glider pump should be around 30 Hz, with smaller vibration on other frequency points. The wave number spectrum on descending section（pump on） shows that although the action of pump has an impact on turbulence observation,the vibration frequency at the side of the wave number is an invalid spectrum for observation in the space,meaning that the vibration of the platform has little impact on the observation of shear signals. The dissipation rate measured by shear probe is on the order of magnitude of 10-7 W/kg, which has a good match with the Nasymth spectrum theory, thus verifying the feasibility of small-scale turbulence observation based on underwater glider.