Study On 3-D Turbulent Numerical Simulation On Airflow And Optimal Design Of Greenhouse

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.