橫搖水槽波能轉換器之初步探討

Preliminary Study on a Concept of Wave Energy Converter using Anti-rolling tank

莊朝鈞(Chao-Chun Chuang)

指導教授 ： 邱逢琛

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.10508

摘要

減搖水槽常用於抵抗船體之橫搖運動，基本構造為一Ｕ形槽，中央有連通管，其主要原理為當水槽受到搖晃時，內部裝載於兩側之水會因重力所致有平衡之趨勢，而出現流動之現象，並對乘載之水槽產生力矩，以致有平衡船體之作用。本研究應用計算流體力學套裝軟體Fluent進行二維橫搖水槽之流體動力研究分析，探討其轉換波能之機制。先以動態網格進行附加質量與減衰係數之求解驗證，以文獻P. MCIVER and D. V. EVANS (1984)與J. W. Bedel (1971)進行比對，確定計算流體動力係數之可靠性。接著驗證橫搖水槽以簡諧橫搖運動下，內部水流運動對水槽本身產生之力矩與其相對於擺動之相位差，並以E.F.G. van Daalen等人(2001)之計算結果驗證比對，確定計算內部水流對水槽本身影響力與力矩之準確性。最後利用Fluent中的波浪模擬能力，對橫搖水槽進行波浪激振力之計算。綜合各項流體動力係數與所有外力(波浪激振力與內部水流對水槽本身之力與力矩)求解最終穩定之運動方程式，並計算橫搖水槽之波能轉換效率。基於本基礎上，期望後續能以數值計算，進行橫搖水槽作為波能轉換器之實際設計與應用。

關鍵字

波能轉換器 ； 橫搖水槽 ； 計算流力 ； FLUENT

並列摘要

Anti-rolling Tank is commonly used in resisting rolling motion of ship hulls. It’s a U-shaped device including connecting pipe, so that it sometimes referred to as “U-tube.” When ships hulls encounter waves and rolling motion occurs, anti-rolling tank will roll with ship hulls. But the internal water will flow with phase lag due to gravity and damping, and the flowing motion will generate an inverse moment on the tank.
In this study, we applied ANSYS Fluent , a commercial CFD software package , to analyze a two dimensional anti-rolling tank and to explore the mechanism of internal water flow kinetic energy generation.
Firstly, we used dynamic mesh to verify the obtained solution of added mass and damping coefficient by comparing with the results published in the references of P. MCIVER and D. V. EVANS (1984) and J. W. Bedel (1971). And then we verified the calculated moment and phase difference due to internal water flow of anti-rolling tank under harmonic roll motions by comparing with the results published in the reference of E.F.G. van Daalen (2001). Finally, we used wave inlet boundary condition of Fluent to simulate waves and obtain wave exciting forces acting on the box of anti-rolling tank.
Then, we consider all the effects of external forces and moments and hydrodynamic coefficients, and solve the equations of motions to obtain the wave-induced motions of the anti-rolling tank, and calculate its wave energy converting efficiency.
Based on the results of this study, we expect that in the near future we can apply the numerical calculations to implement further practical application of wave energy converter using anti-rolling tank.

並列關鍵字

Wave Energy Converter ； Rolling-tank ； CFD ； FLUENT

參考文獻

[1] Treakle, T. W. (1998)”A Time domain numerical study of passive and active anti

rolling tanks to reduce ship motion,” MSc Thesis. Virginia Polytechnic Institute

[2] P. MCIVER and D. V. EVANS (1984) “ The occurrence of negative added mass in free-surface problems involving submerged oscillating bodies, ” Journal of Engineering Mathematics 18 (1984) , 7-22.

[3] J. W. Bedel (1971) “Improved method for the calculation of the added mass and damping coefficients of oscillating cylinders,” Naval ship research and development center.

[5] Joao Cruz , “Ocean wave energy – Current status and future prepectives” , Springer.