Application of Composite Grid Approach in Computing Flow around Ship with Appendage

使用組合式網格計算具附屬物船舶之周圍流場

10.6124/TAASRC.200003_32(1).09

趙修武(Shiu-Wu Chau)；周顯光(Shean-Kwang Chou)；呂崇湧(Chung-Yung Lu)

組合式網格 ； 網格重疊 ； 紊流計算 ； 具附屬物船舶周圍流場 ； composite grid method ； overlapping grid ； RANS computation ； flow around ship with appendage

中國航空太空學會學刊

32卷1期（2000 / 03 / 01）

81 - 87

英文

船艉部流場因受到強烈黏性效應之影響，必須使用Navier-Stokes方程式來解析，以提供設計與修改艉部線形的依據，艉跡流不僅用於評估艉部線形的優劣，更提供往後進行螺槳設計所需之入流資料。然而複雜的艉部形狀，常因此造成彼此嚴重歪斜之網格線，增加了求解Navier-Stokes方程式的困難，導致在計算流場產生較大之誤差。爲了避免該問題，在離散計算空間時，導入組合式網格系統，在該系統中網格與網格間可擁有不同的邊界，而允許彼此間有部分重疊，以改善網格的品質，產生較爲正交之網格。計算範例爲一雙艉鰭散装貨輪及加裝一對渦流產生器之全貨櫃輸之艉跡流計算，數值計算與船模試驗結果相當吻合，可見該法有其優越性。使用組合式網格求解流體流經複雜幾何之三維流場，可大幅減少建構數值網路所需之時間與困難度，同時由於網格品質的提高，數值計算結果亦更爲精確，使得本計算程式在評估船輝線型設計的實用性上大幅提升。

In order to deal with complex geometry, a composite grid method is developed and incorporated with the USDDC RANS solver. In the composite grid approach, the numerical grids of different zones can overlap with each other in the computational domain. More flexibility and ease in generating numerical grids can be obtained. Grid skewness can be better improved, and therefore the numerical diffusion can be also reduced. Two examples are demonstrated here to show the advantage of applying overlapping grids. At first, the numerical computation of flow around a twin-skeg bulk carrier is shown. Better numerical prediction of propeller wake by a composite grid is obviously observed compared to the one by a traditional block-structured grid. The second one shows the numerical prediction of wake improvement of a container ship by installing a pair of vortex generator on ship hull near stem. Again the numerical results agree well with wind tunnel measurements. The composite grid approach is proven to be an effective means to compute flow for complex geometry with required engineering accuracy.