- 學位論文
具船艉水翼滑航船形靜水阻力性能數值模擬
Numerical Simulation of Planing Hull with Stern Hydrofoil in Calm Water
摘要
本研究內容包括兩大部份，首先為滑航船形的靜水數值模擬，其次為具船艉升力翼裝置的阻力數值模擬，重點為該裝置的工作原理，本研究採用計算流體力學軟體 Simerics-MP求解滑航艇周圍流場，該軟體透過有限體積法離散流場控制方程式，其中時間維度具有一階離散精度，速度場則採用二階精度離散方法。另外透過k ϵ模型描述紊流流場，以紊流黏性計算雷諾應力，達到降低計算成本的效果。壓力及速度間的耦合關係則是透過SIMPLE法加以解析，同時以流體體積法來描述兩流體交界面處的自由液面行為。在船舶阻力數值模擬中，採用系列62中的Model4667 1船形做為目標船形，模擬船速對應福勞德數落於0.4至0.9之間。藉由數值結果與實驗數據比對以驗證流場求解器的精度，計算結果顯示阻力預估與實驗的誤差皆低於10%以下。船舶航行姿態，在高速時有較大的誤差，整體而言其誤差落於合理範圍。在船艉水翼的研究中，採用源自Model4667-1船形的Affine Model，使用實船尺寸為研究目標，加裝船艉水翼後最大減阻效果約為15%左右，而此時船速落於福勞德數0.5左右。為了說明船艉水翼工作原理，將水翼的受力拆解成阻力以及升力加以分析。因為升力的部分分量提供推力，進而降低了水翼所受阻力。模擬結果亦顯示，翼形所產生的升力顯著降低滑航船形於航行時的俯仰角，尤其在福勞德數為0.9時。
並列摘要
This study includes two major parts. The first part is the resistance simulation of a planning hull in calm water. The computational fluid dynamics (CFD) approach is adopted to reduce the cost of conventional resistance test in a towing tank. The second part is the ship simulation with a stern lift device and the understanding of its working principle. This study employs the commercial software, Simerics-MP, to solve the flow field around a planing hull. The software discretizes the Navier-Stokes equations through a finite volume method where the time term is first-order approximated and the velocity field is second-order approximated. The turbulence flow field is described through a k ϵ model for reducing the computational cost in modeling turbulence. SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) scheme is used to solve the coupling relation between pressure and velocity. A volume of fluid method is used to simulate the free surface between two fluids. In the ship resistance simulation, Model 4667-1 of series 62 serves as the target hull and the simulation ship speeds are determined corresponding to Froude number ranging from 0.4 to 0.9. The simulation result is compared with experimental data for validating the flow solver. The result shows that the resistance error between CFD and experimental result is below 10%. However, the sailing attitude prediction error is higher than the resistance prediction error, especially at high Froude numbers. Generally speaking, the prediction error is within a reasonable range. For the second part, the full-scale Affine model serves as the target hull for investigating the effect of stern hydrofoil. The maximum resistance reduction effect is about 15% near Froude number 0.5 after the hydrofoil is retrofitted. In order to understand the working principle of the stern hydrofoil, the force acting on the foil is decomposed into drag and lift. The result shows that a part of lift force provides thrust for reducing the hydrofoil drag and the lift force significantly decreases the angle of running trim near Froude number at 0.9.