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

在港口设计中，一般重力波(周期约0.1-10秒)会引起各种问题，但海洋工程和土木工程研究成果对此提出了一些对策，并已解决了相当一部分问题。然而，停泊在港口的船舶受到长周期(几十秒、几分钟的周期)重力波的纵摇和横摇，其对策还不够充分，目前在系缆强度和货物装卸工作方面仍存在一些问题。从公海和近海海域传播的如此长的周期波(幅度小于几十厘米，一个周期，大约几十秒，几分钟)包括以下问题：(1)长周期涌浪的长水粒运动轨道在港口附近引起强烈的分离和早期流动，导致港口被海底的流沙掩埋。(2)…长周期重力波的波能传播和反射衰减较小，入港后大部分波能被保留，在与港口固有频率发生共振的情况下，波能增大，从而导致系泊或锚泊船舶在港内发生危险的纵摇运动。如此长周期的波浪给港口设计和锚地带来的这些严重问题开始受到人们的关注。由于目前对长周期波的成因和特征尚不清楚，因此对长周期波的研究将会有很大的进展，特别是在观测事实的基础上弄清长周期重力波的成因和特征显得尤为重要。然而，与常规重力波相比，长周期重力波周期过长，幅度过小，常规的波浪观测技术难以完成测量，为此，本研究提出了利用载波相位差分GPS精密测量三维运动的阵列式波浪观测浮标系统。在该系统中，精确测量了立交桥浮标前观测到的风向和长周期波的三维波浪信息。并通过陆上实验和计算机模拟进行了效果评估。利用该系统，可以明确长周期重力波产生的原因和特点，解决船舶系泊、锚泊或港口设计中的一些问题。在不久的将来，我们将能够根据长周期重力波来明确长周期重力波的特征以及港口和系泊船舶的安全问题。较少

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