本論文透過急遽遞減法(Steppest Descent Method)與套裝軟體CFD-RC的結合，配合模擬紅外線溫度感測器所量測的模型外表面溫度值為參考，來預測模型內部不規則空心體的形狀。
本論文以Fortran撰寫主程式搭配CFD-RC套裝軟體當作副程式進行數值模擬，套裝軟體CFD-RC裡的CFD-ACE+是一套工程模擬軟體，可以將系統和工程設備中的流體、熱學、化學、電、生物和機械現象聯合在一起進行模擬，優點是可以容易的設定模型的所有邊界條件還有自動產生網格的功能。
本論文有兩個主題，其一為第二章的穩態熱傳導問題，模型內部空心體形狀不隨時間變化；另一個為第三章的暫態熱傳導問題，模型內部空心體形狀將隨時間與位置做變化。兩章均在探討利用反算法預測三維模型內部空心體的邊界形狀。物理模型皆為三维均勻材質，外表正立方體，內部空心體則為未知不規則幾何形狀。
此外，吾人尚考慮不同內部形狀起始猜值與量測誤差，對上述方法於預測內部空心體邊界形狀的影響。

A three-dimensional shape identification problem (or inverse geometry problem) in estimating the unknown irregular shape of internal cavity by using the steepest descent method (SDM) and a general purpose commercial code CFD-RC is examined in this study based on the simulated measured temperature distributions on the outer surface by the simulated infrared thermography.
The commercial code CFD-RC can be applied to many engineering problems such as fluid flow、heat transfer、chemical reaction and electricity, etc. This code has the feature of auto meshing and it can be used to calculate many practical but difficult direct thermal problems.
The present thesis has two themes, in chapter two the goal is to estimate the irregular configuration of an internal cavity in a steady-state problem, while in chapter three the objective is to estimate the time and position dependent internal cavity. The geometry of the outer boundary for all the examples considered in this thesis is taken as a cube.
The numerical experiments are performed to test the validity and accuracy of the present shape identification algorithm by using different types of cavity shapes, initial guesses and measurement errors. Results show that excellent estimations on the unknown geometry of the internal cavity can be obtained.

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