本文利用數值模擬研究部分多孔性介質之矩形封閉空間中，磁流體之擴散對流現象。在多孔材介質中使用Forchiemer-Brinkman-extended Darcy模式，考慮浮力效應、多孔性介質內部黏滯效應與慣性力，定義左右壁面為絕熱，上下壁面為固定溫度及濃度，並在橫向上施加一均勻磁場做用於流場中。改變不同參數浮力強度Ra、磁場強度Ha、路易士數Le、浮力比N、多孔材熱質S及多孔材達西數Da，最後比較改良濃度擴散率前後之差異，觀察紐塞爾數Nu、希吾爾數Sh、等溫度線圖、等濃度線圖及流線函數圖的變化。
結果顯示當Ra、Da增加及N、Ha減少時會幫助熱傳及質傳。多孔材介質增加熱源S時會使熱傳量降低，但質傳量會變大。當Le逐漸增加時，熱傳量會有最大值的產生，而質傳量隨Le數增加而變大。濃度擴散率改良後會使質傳量變小，但熱傳量不一定變小。

This thesis reports the effect of magnetic field on the double diffusive natural convection in an enclosure filled with partial porous layer by numercial method. The Forchiemer-Brinkman-extended Darcy model has been used to solve the governing equation in the saturated porous region. The right and left walls are adiabatic and the top and bottom walls are fixed temperature and concentration. In addition, a uniform magnetic field is applied perpendicular to the short sides. Variation of the enclosure Nusselt numbers (Nu), Sherwood numbers (Sh), isotherms, isoconcentration lines and Streamlines due to changes Rayleigh (Ra), Hartmann (Ha), Lewis (Le), Darcy numbers (Da), buoyancy ratio (N), the heat source of porous media (S) and modified mass diffusivity.
The results shows that when Ra and Da increase and N and Ha decrease, Nu and Sh will increase. When increase S, Nu will decrease and Sh will increase. When increase Le, Nu has a maximum value but Sh will increase. After modifying mass diffusivity, Sh will decrease but Nu will increase or decrease.

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