Parametric Geometric Design of Underwater SONAR Vehicles

水下載具是指能在水下運動從事任務的載人或是承載儀器的載具。水下載具的設計根據任務需求及操作環境的不同以及建造成本的考量，而有適用的水下載具型態。在海底地形探測中，聲納為常用的技術，藉由水下載具搭載聲納探測裝備，可延伸聲納有效作用範圍的深度，然而在深度產生改變的運動過程中，水下載具的運動姿勢會同時影響聲波的傳遞方向。本研究之目的為設計一個搭載聲納音鼓進行海底地形探測任務的水下載具，且在穩定姿勢時具有高穩定性。設計方法為利用電腦輔助設計進行系統性參數化幾何外型設計，並在重力、靜浮力、繫纜力、流體動力作用下，調整不同繫纜點及不同的重量配置，進行縱搖穩定角度及縱搖運動剛性分析。重力由載具及掛載物的重量配置而定，為使用端的可操作項，而流體動力則藉由計算流體力學方法模擬得之；靜浮力則使用本實驗室開發之浮體程式計算。將各外力項代入剛體運動方程式，以合力平衡條件求解繫纜力，並採用Euler’s method迭代計算合力矩，直至合力矩平衡時的縱搖角度即為穩定縱搖角，並量化評估在穩定縱搖角時之縱搖運動剛性。根據本研究計算結果，按實際操作要求載具必須在水平姿勢下進行探測，繫纜點往艏部移動能夠有效提高縱搖運動剛性，且重量配置的調整自由度較高；在繫纜點固定時，欲維持水平姿勢則縱向重心位置隨著載具質量的增加需往艏部移動，而縱搖運動剛性降低。The underwater vehicle is a vehicle that could carry human beings or equip instruments to carry out underwater missions. Based on different requirements of the missions, we have to choose appropriate ones for both economics and effectiveness considerations. SONAR(SOund Navigation And Ranging) is an useful technique for surveying sea-bottom topographies. Equipping the transducers with the underwater vehicle could increase the effective depth of SONAR. However, the positioning of the underwater vehicle could affect the direction of acoustic waves. The purpose of this study is to design an underwater vehicle equipped with transducers in order to survey sea-bottom topographies and with high stability at the stable pitch angle. We use CAD software to systematically design a parametric geometry shape and analyze its statical equilibrium. The gravity force depends on the weight distribution. We apply Computational Fluid Dynamics to calculate the hydrodynamic force. In addition, we apply the kinematical equations of rigid body, and substitute the computed hydrodynamic force into the Buoyancy Program developed by the NTU ESOE CAD Lab. Furthermore, we use Euler’s method to iteratively calculate mooring force and the stable pitch angle with different mooring joints or weight distributions and numerically estimate the pitch stiffness of the underwater vehicle. According to this research, if the stable pitch angle equals zero, moving the mooring joint forward could increase the pitch stiffness and the weight distributions would become more flexible. When the mooring joint is fixed, the longitudinal center of gravity has to move forward to maintain a constant stable pitch angle if the mass of underwater vehicle increases, however, the pitch stiffness would decrease