臺灣博碩士論文加值系統

以小板法來計算二維物體周圍之勢流場,在此類方法中,幾何方面的處理,
簡單起見,一般將物體外形以多邊形來近似,本文則利用物體外形原來準確
之數學定義,或利用開放周期B木條曲線(open periodic B-splines)之方
法來近似,並直接計算依高斯積分法則之階數所需之高斯點座標及法向量.
另外偶流之分佈亦採高斯離散法及B木條曲線表示法處理,利用滿足
Dirichlet內表面邊界條件的方式,可建立一套與幾何外形配合以求解偶流
強度之計算方法.由初步的結果顯示:高斯離散法在物體對稱的情況下準確
度良好,但在具有攻角之不對稱情況下,具有明顯誤差;B木條曲線法由於物
體的幾何及偶流的分佈同時採用B木條曲線,且採用"次小板"的分割概念,
在對不同翼形計算時,可達相當好之準確度.

Panel method is a well-known method for dealing with two
dimensionalpotential flow problems.Due to simplicity,a body
shape is generallyrepresented by a closed polygon.In the present
paper,a body shape is represented by an exact mathematical
formulation or by the open periodicB-spline method.Gaussian
quadradure points and normal vectors needed forthe panel method
are then generated from the two geometrical definitionmethods.
Corresponding to geometrical representations,two methods are
alsoused for doublet distributions:the discrete Gaussian
distribution methodand the continuous B-spline method.Making use
of Dirichlet internal boundarycondition,a method is set up for
solving the doublet strengths in accordance with the geometrical
definitions.The results computed from the presentmethods show
that the Gaussian distribution method offers results with good
accuracy in case of symmetrical bodies while in case of
asymmetricalbodies with angle of attack the accuracy is broken
down.In the B-spline method,both the panel geometry and doublet
distributions are defined by B-spline curve,and the concept of
"sub-panel" is then adopted by splitting a panel at its
collocation point.Numerical results for different foils show
that excellent accuracies can be achieved by this method with
only a few computing point.