本研究旨在探討壁面模式大渦流模擬（Wall-Modeled Large Eddy Simulation,Wm-LES）於異溫平板間紊流混合對流（Turbulent Mixed Convection with OppositelyHeated Plates）之預測能力，並以摩擦雷諾數𝑅𝐸𝜏=150 與𝑅𝐸𝜏=640 兩種條件作為研究案例。
流場設定為上壁面加熱、下壁面冷卻，使流場同時受到浮力效應與剪切作用影響，形成具有熱傳與紊流耦合特性的混合對流現象。研究中分別進行未使用壁面模型之大渦流模擬（LES）與加入壁面模型之大渦流模擬（Wm-LES），藉以評估壁面模型於不同雷諾數條件下對流場及熱傳特性的效果。
數值方法採用隱式大渦流模擬（Implicit Large Eddy Simulation, ILES），利用數值耗散取代傳統次網格尺度模型，以解析主要紊流結構並降低模型參數對結果之影響。透過壁面模型重建近壁區速度與溫度分布，使粗網格條件下仍能合理描述壁面剪應力與熱通量行為，進而降低高雷諾數模擬所需之計算成本。
研究結果透過與直接數值模擬（Direct Numerical Simulation, DNS）[9、17]資料進行比較，評估不同模擬方法之準確性。結果顯示，在 𝑅𝐸𝜏=150 條件下，由於近壁流動結構仍可被較完整解析，LES 與 Wm-LES 皆能合理預測平均速度與平均溫度分布；然而在𝑅𝐸𝜏=640 條件下，未使用壁面模型之 LES 對近壁速度梯度、紊流統計量及溫度場預測誤差明顯增加，而 Wm-LES 則能有效改善近壁區流動與熱傳預測，使平均速度剖面、雷諾應力分布及溫度分布更接近 DNS 結果。整體而言，本研究驗證了 Wm-LES 應用於異溫平板紊流混合對流模擬之可行性，並顯示其在高摩擦雷諾數條件下能有效提升近壁流場與熱傳特性的預測能力，同時兼顧計算效率。研究成果可作為未來高雷諾數熱流體問題及工程熱傳模擬中壁面模型發展與應用之參考。

This study investigates turbulent mixed convection between oppositely heated plates using the Implicit Large Eddy Simulation (ILES) approach. Simulations were performed at friction Reynolds numbersReτ= 150 andReτ = 640 to evaluate the influence of Reynolds number on the flow and thermal structures. In addition, cases with and without a wall model were considered to assess the effectiveness of wall modeling under different flow conditions. The numerical results were validated against available Direct Numerical Simulation (DNS) databases.
The results indicate that the ILES approach is capable of reproducing the major characteristics of turbulent mixed convection, including the mean velocity distribution, temperature profiles, and turbulence statistics. For 〖Re〗_τ = 150, the numerical predictions show good agreement with the DNS data, demonstrating that the main flow and thermal features can be captured accurately. As the Reynolds number increases to 〖Re〗_τ= 640, stronger turbulent mixing and buoyancy interactions are observed, leading to greater challenges in resolving the near-wall flow structures.
Comparisons between LES and wall-modeled LES reveal that the influence of the wall model depends on the Reynolds number and grid resolution. In some cases, the wall model improves the prediction of near-wall quantities and reduces the discrepancy from DNS results. However, under certain conditions, the wall model may introduce additional deviations due to the assumptions adopted in the wall treatment. These observations suggest that the applicability of wall modeling should be carefully evaluated for mixed convection flows involving both shear-driven and buoyancy-driven mechanisms.
Overall, the present study demonstrates the capability of ILES in simulating turbulent mixed convection at different Reynolds numbers and provides a systematic assessment of wall-model performance through comparisons with DNS data. The findings offer useful references for future investigations of high-Reynolds-number buoyancy-affected turbulent flows.

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