本研究分別使用質點影像測速儀(Particle Image Velocimetry)與紅外線測溫儀(Infrared Thermography)量測一渦輪機葉片中180度銳轉平滑壁面正方形冷卻雙通道的紊流場結構與壁溫分布。雷諾數(Reynolds number)在量測紊流場結構時訂於5300；而在量測壁溫分布時，雷諾數則從5000變化至20000。除了平均速度(U_st, U_sp, and U_ver)與紊動速度(u_st, u_sp, and u_ver)之外，本研究將會探討轉彎效應對於紐賽數比(Nu⁄〖Nu〗_∞ )和高階紊流統計參數的影響，其中高階紊流統計參數包含雷諾剪應力((u_st u_sp ) ̅, and (u_sp u_ver ) ̅)、紊流動能(k)、歪斜度(S)、平坦度(F)、紊流時間與長度尺度(τ_st, τ_sp, τ_ver, and λ_ver)、紊流能量頻譜(E)、以及紊流動能產生項。
研究結果顯示在轉彎區到轉彎後一倍水力直徑之間，F會隨著S的上升而下降，反之亦然，此結果並未見於先前單通道的文獻。除此之外，透過一維的時間頻譜分析可以發現在轉彎區正中央的剪力層上有一260Hz的主頻(Predominant Frequency)。利用流場可視化可以發現此主頻與剪力層上渦旋的產生頻率相符合。而與此渦旋相關的τ_sp側向分布也被進一步的發現與轉彎區的Nu⁄〖Nu〗_∞ 側向分布有著高度相關性。
透過相關係數(Pearson Product-Moment Correlation)的計算，本研究可以定量的分析出與Nu⁄〖Nu〗_∞ 有著高度、中度、和低度相關性的流力參數，分別為平均渦度大小((|ω| ) ̅)、(√((〖U_st〗^2+〖U_sp〗^2)), u_sp, u_ver, k, (u_sp u_ver ) ̅, τ_sp, and τ_ver)、和(U_ver, u_st, (u_st u_sp ) ̅, S, F, τ_st, λ_ver)。根據以上結果，本研究首先提出一描述本180度銳轉平滑壁面正方形雙通道中(|ω| ) ̅和Nu⁄〖Nu〗_∞ 之關係的經驗公式。

Turbulent flow structures and heat transfer in a 180-deg sharp turning two-pass internal coolant passage of a turbine blade are investigated experimentally by particle image velocimetry (PIV) and infrared thermography (IRT) techniques. The coolant passage has a square cross-section and smooth wall. The Reynolds number (〖Re〗_b) based on bulk mean velocity (U_b) and duct hydraulic diameter (D_H) for PIV and IRT measurements are respectively 5300 and 5000-20000. In addition to the mean velocity (U_st, U_sp, and U_ver) and fluctuating velocity (u_st, u_sp, and u_ver), the turn effects on the Nusselt number ratio (Nu⁄〖Nu〗_∞ ) and spanwise distributions of high-order turbulence statistics including Reynolds shear stresses ((u_st u_sp ) ̅, and (u_sp u_ver ) ̅), turbulent kinetic energy (k), skewness factor (S), flatness factor (F), integral scale (τ_st, τ_sp, τ_ver, and λ_ver), energy spectrum (E), and production term of turbulent kinetic energy are explored in the present study.
The results show that F in between the pre-turn and post-turn 1D_H decreases with increasing S and vice versa, which has not been previously reported for single-pass duct flow. Meanwhile, from both 1-D longitudinal and spanwise temporal spectra, a predominant frequency of 260Hz is spotted at the divider tip shear layer and qualitatively verified by flow visualization. As a relevant parameter of shedding vortex, the spanwise profiles of τ_sp are further found to be in strong correlation with the spanwise Nu⁄〖Nu〗_∞ distributions.
Using Pearson product-moment correlation, the present study is capable of quantitatively identifying the highly, moderately, and weakly correlated fluid flow parameters on Nu⁄〖Nu〗_∞ as mean vorticity magnitude ((|ω| ) ̅), (√((〖U_st〗^2+〖U_sp〗^2)), u_sp, u_ver, k, (u_sp u_ver ) ̅, τ_sp, and τ_ver), and (U_ver, u_st, (u_st u_sp ) ̅, S, F, τ_st, λ_ver), respectively. Based on these parameters, an empirical correlation formula between (|ω| ) ̅ and Nu⁄〖Nu〗_∞ in the present two-pass smooth square duct with 180-deg sharp turn is proposed for the first time.

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