Development of GPS Measurement System and Characteristics Analysis for Long Period Gravity Wave That Induces Long Period Oscillation of Water Surface in Harbour

一般重力波（周期约0.1 ~ 10秒）在港口设计中会引起各种问题，对此，海洋工程和土木工程的研究成果都考虑了一些对策，并已解决了相当一部分。然而，在港口停泊或停泊的船舶受到长周期重力波（周期几十秒，几分钟）的倾斜和翻滚，其应对措施是不够的，目前在系缆强度和货物装卸工作方面还存在一些问题。这种从公海和沿海水域传播的长周期波（对于振幅小于几十厘米，周期约几十秒，几分钟）包括以下问题。(1)长周期浪涌的长水粒运动轨道在港湾附近形成强烈的分离和早流，造成海底流沙埋港。(2)在靠近港湾的地方产生较强的分离和早流，对在靠近港湾的狭窄区域航行的船舶造成严重的安全问题。(3)长周期重力波的波能传播和反射衰减较小，入射到港口后保留了较大一部分波能，在与港口固有频率共振的情况下，波能可能增长。对停泊在港口内的船舶造成危险的俯仰和横摇运动。这种长周期波浪对港口设计和港口锚地造成的严重问题已开始受到人们的审视。由于长周期波的成因和特征尚不清楚，因此对长周期波的研究有望立即展开。特别是，在观测事实的基础上研究长周期重力波的成因和特征显得尤为重要。但是，由于长周期引力波的周期过长，与普通引力波相比，其振幅太小，用常规的波观测技术进行测量比较困难。为此，本研究提出了利用载波相位差分GPS精确测量三维运动的阵列波观测浮标系统。该系统对三叶草浮标前观测到的风浪方向和长周期波浪的三维波浪信息进行了精确测量。并通过陆地试验和计算机模拟对其有效性进行了评价。利用该系统，明确了长周期重力波产生的原因和特点，解决了船舶系泊、锚泊或港口设计中的一些问题。在不久的将来，利用我们所提出的GPS测量系统，我们将能够明确长周期重力波的特性，并根据长周期重力波了解港口和系泊船舶的安全问题。少

When a harbor is designed, a general gravity wave (period about 0.1-10 second degree) causes various problems, but concerning about it some countermeasures are considered by marine engineering and results of research of civil engineering, and a considerable part is already solved. However a ship anchored or moored in a harbor is pitched and rolled by a long period gravity wave (for period dozens of seconds, several minutes), it's countermeasure cannot be still enough, and now some problems on a mooring line strength and cargo handling work are still remained. Such a long period wave (for the amplitude is less than dozens of cm, a period, about dozens of seconds, several minutes) that is propagated from the open sea and coastal waters area includes the following problems.(1) A strong detachment and early flow are caused in harbor mouth neighborhood by long water particle exercise orbit of a long period surge, and they cause a harbor burying by drifting sand of bottom of the sea.(2) By a … More strong detachment and early flow near harbor mouth, it causes a serious and security problem on a ship navigating a narrow area near harbor mouth.(3) Wave energy of a long period gravity wave has a small propagation and reflection decrement, and after incidence to a harbor a greater part of the wave energy is kept and it may grow in the case of resonance with the harbor inherent frequency.Then a dangerous pitching and rolling movements for a mooring or anchoring ship in the harbor are caused by it. These serious problems for harbor design and the anchorage in a harbor caused by such a long period wave is beginning to examine. There development of a study for a long period wave is expected immediately, because the cause and characteristics of a long period wave are not made clear yet.In particular it is appear that a study to make clear the causes and the characteristics of a long period gravity wave on the basis of an observation fact is important. However it is difficult that the measurement is done by conventional wave observation technology, because a period of the long period gravity wave is too long and amplitude of it is too small compared with a normal gravity wave.Therefore in this research arrayed wave observation buoys system whose 3 dimensional movements are measured precisely by the Carrier-Phase Differential GPS is proposed. In this proposed system, a wind wave direction which is observed in before Cloverleaf-Buoy and a 3 dimensional wave information of a long period wave are measured precisely. And an evaluation of effectiveness was carried out by the experiment on land and some computer simulations. As using this proposed system, it made clear the cause and characteristics of a long period gravity wave and solve some problems about a ship's mooring and anchoring or harbor design.In near future, we will be able to clear the characteristics of the long period gravity wave and some problems about safety of port and mooring ship according to the long period gravity wave with the use of our proposed GPS Measurement System. Less