基于球体模型的苹果接触点局部处理方式研究

发布时间：2018-07-03 17:40

  本文选题：苹果 + 冷链物流　； 参考：《农业机械学报》2016年11期

【摘要】：为实现新鲜果蔬采后预冷CFD数值模拟研究,以单个富士苹果为研究对象,构建果品近真实3D模型,在雷诺数为10~30 000的范围内对比真实果形与等直径球体壁面切应力、壁面阻力系数、边界层分离角度以及尾流回流区长度之间的不同,验证在CFD模拟研究中是否可直接利用等直径球体替代苹果真实形状。为实现果品与果品(或箱体壁面)接触点局部位置的最佳CFD建模,充分考虑果品之间局部传热性对温度变化的影响,本文以彼此接触的两果模型为研究对象,从壁面阻力系数、两果中心线上的温度模拟结果准确性角度确定4种不同的局部处理方式(缩小法、膨胀法、消平法和桥梁法)在不同雷诺数范围内各自最佳的局部处理尺寸范围。研究结果表明,在研究中可直接利用等直径苹果替代苹果真实形状,在整个雷诺数范围内两者之间的各种边界层物理量最大相对偏差在15%左右,桥梁法在4种接触点局部处理方式中模拟准确性最高,通过对比实验验证,温度模拟值与实测值具有较好的一致性,其最大均方根误差为1.514℃,平均相对误差在20%左右。
[Abstract]:In order to realize the CFD numerical simulation of fresh fruits and vegetables after harvest and pre-cooling, a 3D model of fruit products was constructed with a single Fuji apple as the research object. The wall shear stresses of real fruits and equal diameter spheres were compared in the range of Reynolds number of 10 ~ 30 000. The differences of wall resistance coefficient, separation angle of boundary layer and length of wake reflux zone verify whether equal diameter sphere can be directly used to replace apple real shape in CFD simulation. In order to achieve the best CFD modeling of the local position of the contact point between fruit and fruit (or box wall), and to fully consider the effect of local heat transfer between fruit products on the temperature change, this paper takes the two fruit models in contact with each other as the research object and takes the wall resistance coefficient as an example. The accuracy of the temperature simulation results on the two fruit centerlines determines four different local processing methods (reduction method, expansion method, flattening method and bridge method) in different Reynolds number range. The results show that the equal diameter apple can be directly used to replace the real shape of apple in the study. The maximum relative deviation of various boundary layer physical quantities between them in the whole Reynolds number range is about 15%. The bridge method has the best simulation accuracy among the four kinds of local processing methods of contact points. It is proved by the comparison experiment that the simulated temperature value is in good agreement with the measured value. The maximum root mean square error is 1.514 鈩，

本文编号：2094483