A Study of Sloshing Motion and Its Reduction

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Project title

Code/計畫編號

NSC99-2221-E019-051

Translated Name/計畫中文名

沖激運動與減降研究

Project Coordinator/計畫主持人

Jiahn-Horng Chen

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Systems Engineering and Naval Architecture

Website

https://www.grb.gov.tw/search/planDetail?id=2153698

Year

2010

Start date/計畫起

01-08-2010

Expected Completion/計畫迄

01-07-2011

Bugetid/研究經費

600千元

ResearchField/研究領域

機械工程

"沖激（sloshing）為船舶流體動力學重要的議題之一，當有自由液面存在、而此液面又受到外力干擾時，就會有沖激現象出現，因此VLCC 與LNG 船舶，均有此類問題的存在。特別是近年來LNG 船舶設計與建造的快速發展，相關趨勢顯示單一液貨艙的容積將持續加大，導致沖激相關的議題更突顯出其複雜性與重要性，而這些議題在研發（包括數值預測與實驗模擬）上，均有其瓶頸亟待突破，否則相關的研究成果將無法應用到產業界。本研究計畫擬採用計算流體力學來研究沖激問題，我們特別感興趣的是槽箱幾何對沖激現象的發展與壁面衝擊壓力峰值的效應。而透過此一有系統的探討，我們冀圖從幾何形狀的變化，來進行槽箱形狀的開發與設計，以達沖激減降（sloshing reduction）的效果。本研究計畫將分三年進行。第一年將就現有液體載具的基本二維幾何形狀，進行一系列的沖激計算，從中檢視各種幾何形狀對沖激所造成的效應，包括沖激波的傳遞與沖激壓力隨時間的變化，並探討外力的作用頻率接近共振情形之下的沖激現象。第二年將就第一年所得的結論，進行載具的二維幾何斷面設計，藉以降低沖激的效應，並採用田口法進行最佳設計；檢視設計成果的指標為衝擊壓力的削減度與沖激波波幅的減降度。本年度同時要針對基本的三維幾何外型，進行相關的計算，從中檢視三維幾何外型對沖激所造成的效應。第三年將就第二年的設計結論與三維幾何外型之槽箱的沖激計算經驗，進行載具的三維設計，仍運用田口法進行參數最佳設計，並藉計算流體力學的工具加以檢驗。" "Sloshing is an important issue in marine hydrodynamics. It exists when a free surface subject to external disturbances in, for examples, liquid cargo tanks of VLCC and LNG ships. Particularly, the sloshing problem becomes more complicated and vital since the design trend of LNG ships in recent years shows that the liquid cargo tanks have become larger and larger. However, breakthroughs in both numerical simulation procedures and model test techniques need be made before some bottleneck issues can be resolved and research results can be applied to practical designs. In the present proposal, we attempt to study the sloshing problem by CFD procedure. Of particular interests are effects of the shape of tank on the sloshing development and peak impact load on the walls of tank. Through the study, we also attempt to develop and design the shape of a tank which can enhance sloshing reduction. In the first year, the sloshing phenomena arising in two-dimensional tanks will be studied. The tank shapes for which the sloshing problem will be studied include rectangle, oval, modified oval, circle, and polygon. The effects which will be investigated include sloshing wave propagation, peak impact load, and sloshing phenomena when the exciting frequency is close to the natural frequency. In the second year, the focus is on the two-dimensional tank design which will enhance sloshing reduction. The Taguchi methods of parameter design will be employed for optimal design. The key performance indices of design include the reduction of peak impact pressure and the decrease of the sloshing wave. In addition, we will also conduct the sloshing computations in three dimensional tanks of various shape in order to investigate the effects of the tank shape on the sloshing development. In the third year, we attempt to focus on the three-dimensional tank design enhancing sloshing reduction on the basis of experience gained in the first two years. Again the Taguchi methods will be employed for optimal design purpose. Verification of the design will be made through CFD computations."

Keyword(s)

二維沖激
幾何形狀效應
沖激減降
two-dimensional sloshing
geometrical effect
sloshing reduction

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A Study of Sloshing Motion and Its Reduction

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