應用CFD模擬預測洋流作用下之水下滑翔機運動航跡

CFD Simulations for Trajectory Prediction of an Underwater Glider under the Influence of Ocean Currents

水下滑翔機(autonomous underwater glider，AUG)可透過自身浮力引擎作動以改變其浮力與重力平衡以及重心位置，並藉此達成其調整運動姿態與建構上浮下潛之能力；學理上，前述運動機制為AUG調整航深的方法，然而AUG為節能的水下載具，其拓展航程的主要前進力量來自於海洋洋流，因而洋流之流向與流速大小均會對AUG之航跡產生重大影響，航跡規劃對AUG蒐整海洋環境資訊工作有著不可言喻之重要性，故本研究將嘗試應用計算流體力學(CFD)之流場數值模擬方法解算洋流作動下之AUG運動航跡，以藉此分析與建構適合海洋操作環境之水下滑翔機操作模式。針對應用CFD執行洋流速度對水下滑翔機運動航跡之預測，本論文已完成初步之流場模擬分析與可行性研究，由模擬結果得知，洋流流速之變化將會對水下滑翔機之初始運動姿態、水平運動速度及每次下潛、上浮水平移動距離均會產生顯著影響，論文研究成果將有助於完成國內新型水下滑翔機之設計與開發。

The Autonomous Underwater Glider (AUG) is equipped with a self-adjusting buoyancy engine, allowing it to modify its buoyancy and center of gravity. Through this capability, the AUG can control its motion and achieve both ascending and descending movements. The theoretical mechanism employed by the AUG for adjusting its depth is based on this motion control. However, as an energy-efficient underwater vehicle, the AUG primarily relies on ocean currents for pro-pulsion, which significantly impacts its trajectory in terms of direction and speed. Therefore, trajectory planning plays an indispensable role in the AUG's mission of collecting oceanographic data, highlighting its critical importance. To address this issue, this research aims to apply Computational Fluid Dynamics (CFD) numerical simulations to predict the glider's trajectory under the influence of ocean currents. This analysis will help construct an appropriate operational mode for the underwater glider in various oceanic environments. Regarding the application of CFD to predict the underwater glider's trajectory influenced by ocean currents, the preliminary flow field simulation analysis and feasibility study have been completed. From the simulation results, it is evident that variations in ocean current velocity will have a substantial impact on the glider's initial motion attitude, horizontal speed, as well as the distance covered during each diving and ascending phase. The research findings are expected to significantly contribute to the design and development of a new domestic underwater glider.