在許多工程問題上常使用傳統正算方法來求解其物理量，亦就是探討將已知條件輸入系統模式來分析其輸出為何，這就是正算問題(Direct Problem)。然而在許多實際工程問題中，存在著很多物理量因為客觀條件限制或量測技術不足而無法直接計算或量測其值。因此，為了取得所需之物理量，必須利用反算法藉由其它已知的參數及物理量反求之，這就是逆向或反算問題(Inverse Problem)，而反算問題也已大量被應用於許多幾何形狀的最佳化設計，稱之為反算設計問題（Inverse Design Problem）
就船用流力上來講一般所謂正算問題亦即已知船型來計算其壓力分佈或其阻力。而反算設計問題正好相反，亦即利用已知最佳的壓力分佈或最小的興波阻力（設計者可依設計的限制條件需求而定）進而反算設計求出最佳之船型。此篇研究中利用FLOWTECH International AB公司所開發的商用套裝軟體SHIPFLOW做為吾正算問題之依據，再配合反算設計問題中之拉凡格式法（Levenberg-Marguardt Method）來對本問題建立最佳船型之預測。

For many engineering problems, the physical quantities can be obtained by using some known boundary conditions. This is the so-called “Direct Problem”. However, there are many physical quantities in the engineering problems that can not be measured or calculated directly, we should use some measurement information to estimate them. This is the so-called Inverse Problem. Something the technique of Inverse Problem can be use in Inverse Design Problem.
The direct problem for ship fluid dynamics involves the determination of the hull surface pressure distribution and resistance when the hull form is given. On the other hand the inverse design problem is concerned with the determination of the modified hull form from the given desire pressure distribution.
The present work addresses the development of FLOWTECH and an efficient method for parameter estimation, i.e. the Levenberg-Marquardt algorithm, in estimating the new hull form that satisfies the desired pressure distribution. The Levenberg-Marquardt method has proved to be a powerful algorithm in inverse calculations especially in parameters estimation.

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