【作者】 曹阳；

【导师】 程吉林； 吉庆丰；

【作者基本信息】 扬州大学 ， 水利水电工程， 2004， 硕士

【摘要】 随着我国市场经济体制的确立，以及农村种植业结构的调整，大棚蔬菜得到了飞速的发展。因此，研究大棚的断面型式对于大棚蔬菜生产的影响，具有十分现实的意义和经济价值。然而，对于蔬菜大棚形状的选取，以往一般是根据经验选择而缺乏科学的理论研究证明。 随着计算流体动力学理论和技术的迅速发展，应用三维紊流数值模拟方法来研究大棚内部流场的运动情况研究已成为可能，大棚内部流场具有典型的三维紊流特征，其计算建立在三维流动的理论基础上更加合理。 本文采用流体动力学三维紊流模型对大棚内部流场进行数值模拟。大棚内部三维流动模拟的控制方程为雷诺平均Navier-Stokes方程，并以紊流模型使方程封闭。近壁流动采用壁面函数法，方程离散采用控制体积法。对动量方程的求解，压力与速度的耦合关系采用压力修正法SIMPLE系列算法，变量的布置采用交错网格系统。 本文对拱型、屋脊型、抛物型、斜顶型大棚这四种断面型式的大棚采用上述紊流模型，对其内部流场的流动进行了数值模拟。并在流场计算结果的基础上提出了大棚一次换气时间这一新的概念，并给出了其计算模型及求解方法。大棚换气时间的基本计算思想为：在各个大棚进口内部随机放置若干示踪粒子，算出其到达大棚出口处的时间，求其平均值，即可认为大棚一次换气时间。计算结果表明：斜顶型大棚换气时间最短，抛物型大棚次之，拱形大棚再次之，屋脊型大棚换气时间最长。综合蔬菜大棚流场的三维数值模拟及换气计算结果以及大棚的实际利用效率，本文认为拱型大棚断面型式最优。 计算结果表明：本文所采用的蔬菜大棚内部流场流动的三维数值计算方法及大棚断面型式优化的研究方法是可信和可行的。更多还原

【Abstract】 With the foundation of marketplace’s economic stability in our country and the adjustment of the structure of countryside’s farming, shed vegetable develops at a rapid speed. Therefore, it has realistic sense and economic value to investigate the impact that the intersection figure of shed works on vegetable. But, we always make the choice of the shed shape according to our experience in stead of the scientifical testament in theory.With the development of Computational Fluid Dynamics (CFD),it becomes possible to use numerical simulation of three-dimensional turbulent flow in the research of velocity field inside of greenhouse. Velocity field inside of greenhouse has typical characteristic of 3D turbulent flow,so it’ calculation on velocity field is much more reasonable on the basis of the theory of 3D flow.Velocity field inside the greenhouse is studied by numerical simulation theory of 3D turbulent model of CFD. Control equations include Reynolds Navier-Stokes equation and turbulent model. The computation of near-wall flow has been conducted by wall-function. The control equations are discreted by the Finite-Volume-Method. The pressure and velocity fields are coupled with the semi-implicit pressure recorrection algorithm (SIMPLE) based on the staggered grid system..Velocity field inside of arciform greenhouse , fastigium greenhouse , parabola greenhouse and slanting crest greenhouse have been studied by numerical simulation of 3D turbulent flow. A criterion named time of exchanging gas is brought forward based on the velocity fields inside of greenhouse .The basic method is as follows: firstly,setting some paticles by random in the inlet of greenhouse; secondly, calculating the time of the paticles arriving at the outlet of greenhouse; thirdly , calculating the average time .The average time is the time of exchanging gas of greenhouse. The resultsshow: the time of exchanging gas of the slanting crest is the most shortest, the second is the parabola greenhouse, the third is the arciform greenhouse ,the fourth is the fastigium greenhouse. The arciform greenhouse is thought of the optimal shape of greenhouse based on the time of exchanging gas and the result of velocity field inside of greenhouse by numerical stimulation of 3D and using efficiency of the greenhouse.The result indicate that the method of Velocity field inside greenhouse by numerical stimulation of 3D and the method of judging which shape of the greenhouse is the most optimization are reliable.更多还原