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基于球體模型的蘋果接觸點局部處理方式研究
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“十二五”國家科技支撐計劃項目 (2013BAD19B04) 和歐盟FP7項目(PIRSES-GA-2013-612659)


Local Processing Mode of Contact Points for Apples Based on Sphere Models
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    摘要:

    為實現(xiàn)新鮮果蔬采后預(yù)冷CFD數(shù)值模擬研究,以單個富士蘋果為研究對象,構(gòu)建果品近真實3D模型,,在雷諾數(shù)為10~30000的范圍內(nèi)對比真實果形與等直徑球體壁面切應(yīng)力,、壁面阻力系數(shù)、邊界層分離角度以及尾流回流區(qū)長度之間的不同,驗證在CFD模擬研究中是否可直接利用等直徑球體替代蘋果真實形狀。為實現(xiàn)果品與果品(或箱體壁面)接觸點局部位置的最佳CFD建模,充分考慮果品之間局部傳熱性對溫度變化的影響,,本文以彼此接觸的兩果模型為研究對象,從壁面阻力系數(shù),、兩果中心線上的溫度模擬結(jié)果準確性角度確定4種不同的局部處理方式(縮小法,、膨脹法、消平法和橋梁法)在不同雷諾數(shù)范圍內(nèi)各自最佳的局部處理尺寸范圍,。研究結(jié)果表明,,在研究中可直接利用等直徑蘋果替代蘋果真實形狀,在整個雷諾數(shù)范圍內(nèi)兩者之間的各種邊界層物理量最大相對偏差在15%左右,,橋梁法在4種接觸點局部處理方式中模擬準確性最高,,通過對比實驗驗證,溫度模擬值與實測值具有較好的一致性,,其最大均方根誤差為1.514℃,,平均相對誤差在20%左右。

    Abstract:

    CFD simulations have been widely used in the study of precooling process of fresh fruits and vegetables. This work established a quasi real threedimensional model of Fuji apples, by comparing the wall shear stress, drag coefficient, separation angle and recirculation length of an apple with those of an equaldiameter sphere over a large Reynolds number range (10~30000), and whether an apple can be directly replaced by an equaldiameter sphere in the study of CFD models was verifed. Moreover, to achieve the optimal CFD model of contact points between apple and apple (or the wall of boxes) and fully consider heat transferring by contact among apples, two apples contacting with each other were studied. From the accuracy of simulation results of the drag coefficient and temperature distribution along a line from the center of an apple to the center of another apple, the optimal size range of four different ways of the contact point modifications (e.g., reduction, expansion, smoothing, bridge) for different Reynolds number range was determined. The results showed that an apple can be replaced by an equaldiameter sphere in academic research, and the maximum relative deviation was about 15% for all the physical parameters in the whole range of Reynolds number; the accuracy of bridge methods was the best in four different ways of the contact point modifications. The predicted results were consistent with the measured results by comparing simulation results with those of experiments, and the maximum rootmeansquare error and average relative error for produce temperature were 1.514℃ and 21.07%, respectively.

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韓佳偉,趙春江,錢建平,張翔,范蓓蕾.基于球體模型的蘋果接觸點局部處理方式研究[J].農(nóng)業(yè)機械學(xué)報,2016,47(11):8-17. Han Jiawei, Zhao Chunjiang, Qian Jianping, Zhang Xiang, Fan Beilei. Local Processing Mode of Contact Points for Apples Based on Sphere Models[J]. Transactions of the Chinese Society for Agricultural Machinery,2016,47(11):8-17.

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  • 收稿日期:2016-05-09
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  • 在線發(fā)布日期: 2016-11-10
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