本研究運用直接數值模擬（DNS）方法，深入探討了在低雷諾數條件下，等溫有限稜柱的流場和溫度場特性。我們採用了適用於大規模平行計算的正交網格結構，結合沉浸邊界法（IBM）來處理具有入射角的複雜幾何形狀，考慮了長寬比從1到7的稜柱，其中長寬比定義為稜柱高度與特徵長度（稜柱邊長D）之比值，並對模擬結果進行了驗證和比對。通過分析局部和平均紐塞數，以及利用Q-criterion和主流負方向速度來表示流場的回流情況，我們詳細研究了不同長寬比和入射角下流場的特性。在最後一章節，本文對串聯式稜柱的散熱分析進行了討論。根據模擬的分析結果條列出以下結論。
研究表明，隨著長寬比 (Aspect Ratio，AR) 的增加，三維流動結構的強度相應增強。特別是在長寬比為3時，流場處於穩定和非穩定之間的過渡狀態。棱柱後方的流場結構與尾流渦流密切相關，局部紐塞數較高的區域主要分佈在棱柱中央高度的位置，這是卡門渦流對流場產生最大影響的地方。除此之外，當長寬比為3時，卡門渦流迅速形成，從而導致平均努塞特數的增加，這表明卡門渦流對於強制對流散熱具有積極影響，同時也暗示長寬比為3可能是臨界長寬比。此外，針對稜柱的入射角研究顯示，在30°和45°的入射角下，稜柱的散熱效果能顯著提升，平均紐塞數提高了13%。在串聯式棱柱的流場中，當距離比小於5時，即S/D ≤ 5 (其中S為稜柱與稜柱之間的長度)時，流場呈現穩定對稱的特性；然而，當S/D超過5時，流場開始變得不穩定，並在尾流處出現擺動的現象。最後，在串聯式稜柱的散熱設計中，選擇具有入射角的前方稜柱能夠使整體平均紐塞數提升約19%，從而增強散熱效果。

The present study utilizes Direct Numerical Simulation (DNS) to delve into the flow and temperature field characteristics of finite rectangular prisms under low Reynolds number conditions and isothermal settings. We employ an orthogonal grid structure suitable for large-scale parallel computation and incorporate the Immersed Boundary Method (IBM) to handle complex geometric shapes with incident angles, with validation and comparison of simulation results.
Through analysis of local and average Nusselt numbers, as well as the use of Q-criterion and mainstream negative velocity to denote flow recirculation, we extensively investigate the characteristics of the flow field under different aspect ratios and incident angles, con-cluding with a discussion on the heat dissipation of tandem prisms. Our findings indicate that with increasing aspect ratio, the strength of the three-dimensional flow structures cor-respondingly increases. Particularly at an aspect ratio of 3, the flow field transitions be-tween stable and unstable states. The flow field structure behind the prism is closely relat-ed to the presence of wake vortices, with high local Nusselt numbers primarily concentrat-ed in the central region of the prism, where the Karman vortex has the greatest impact on the flow field. Moreover, the rapid formation of Karman vortices at an aspect ratio of 3 leads to an increase in the average Nusselt number, suggesting a positive influence of Karman vortices on forced convection heat dissipation and implying that an aspect ratio of 3 may be a critical value.
Additionally, optimization of heat dissipation is achievable through incident angles of 30° and 45° for the prisms, resulting in a 13% increase in the average Nusselt number. While tandem prism flow exhibits stable symmetric characteristics at S/D ≤ 5, instability and os-cillations occur when S/D exceeds 5. In the design of tandem prism heat dissipation, se-lecting prisms with incident angles can enhance the overall average Nusselt number and subsequently improve heat dissipation efficiency.

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