魚雷錨擲錨過程受海流作用下之運移特性數值分析

NUMERICAL ANALYSIS OF THE HYDRODYNAMICS CHARACTERISTICS OF TORPEDO ANCHOR INSTALLATION UNDER THE INFLUENCE OF OCEAN CURRENTS

重力安裝錨（gravity-installed anchor，GIA），為一種以錨體自重貫入底床進行安裝的錨碇基礎，其安裝效率高、成本低且不需借助額外安裝設施，而本文所使用形式為魚雷錨（torpedo anchor），在國際上已有實際運用案例。本研究旨在探討魚雷錨受海流作用下，於水中擲錨過程之物體運移數值分析，因此本文考慮外在環境條件及使用不同外型之魚雷錨，並使用計算流體力學（Computational fluid dynamics，CFD）商用軟體FLOW-3D來進行魚雷錨流固耦合作用之數值模擬，於安裝高度（即底床距錨體釋放高度）85 m，觀察物體之落下時間、衝擊速度、偏移角度以及水平位移。當海流流速愈大時，會造成魚雷錨有較大的偏移角度，進而影響物體於底床瞬間之衝擊速度，且可能發生貫入深度不足之情形，導致安裝失敗。

The gravity-installed anchor (GIA) is a type of the anchor foundation that is installed by penetrating the seabed using the weight of the anchor body. It has the advantages of high installation efficiency, low cost, and no requirement of additional installation facilities. The GIA type used in this study is the torpedo anchor, which has been ap-plied in practical cases widely. The purpose of this study is to investigate the numerical analysis of the anchor trans-porting during the installation of the torpedo anchor under the action of ocean currents. Therefore, this article con-siders external environmental conditions and the different forms of torpedo anchors by using computational fluid dynamics (CFD) software, FLOW-3D, to simulate the fluid-solid interaction effect on the torpedo anchor. The falling time, impact velocity, displaced angle, and horizontal displacement of the torpedo anchor were observed at an installation height (i.e., the distance between the seabed and the anchor release height) of 85 meters. The obtained results show that when the current velocity is greater, the torpedo anchor will have a larger displaced angle, which will affect the impact velocity of the anchor on the seabed and may cause insufficient penetration depth, leading to installation failure.