三維非穩態停滯點流動之熱傳遞

三維非穩態不可壓縮導電性流體於停滯點附近的流動與熱傳為主要內容，由連續方程式、動量方程式和能量方程式所導出的偏微分方程式，經由相似變換成為一組非線性的常微分方程。磁參數、非穩態參數、速度比、吸出或吹入，以及冪次r、s與m對熱特徵的影響有仔細的檢視。利用數值計算求出精確的數值解，結果以圖示表之並以物理解釋。當吸出或吹入參數fw、普朗特數Pr、速度比c、磁參數M、x方向冪次r、y方向冪次s、時間冪次m增加時，溫度分布與表面溫度梯度隨之減少，意味著對應的熱傳遞率也增加，而非穩態參數λ增加時，溫度分布有跨越現象發生。

關鍵字

導電性流體；停滯點；非穩態流動；固定表面溫度；相似變換

並列摘要

The characteristic of flow and heat transfer of a three-dimensional unsteady, incompressible, electrically-conducting fluid in the vicinity of a stagnation point is the main scope of the thesis. The surface temperature at the wall is specified as a power law form of distance in the x and y directions and of time also. The governing partial differential equations obtained from continuity, momentum and energy equations are transformed into a set of nonlinear ordinary differential equations by means of a similarity transformation. Exact solutions are obtained using numerical computations. The results are drawn graphically and intepreted physically. The influence of magnetic parameter, unsteady parameter, velocity ratio, suction or blowing and indices r, s, m on the thermal characteristic are examined in detail. When fw, Pr, c, M, r, s and m increase, both the temperature profiles and surface temperature gradients decrease, implying the corresponding enhancement of heat transfer rate. However the crossover phenomenon occurs for increasing values of unsteady parameter.