The Numerical Simulation Research On Wind Load Characteristics Of The Typical Greenhouse

The greenhouse is one of the main facilities among agricultural facilities. The environment in the Greenhouse and structural safety has a direct impact on agricultural economic and social benefits. With the continuous development of greenhouse, structural security studies drew so much attention from more and more people in addition to researches concerning greenhouse environment. Wind load is one of common disasters caused greenhouse damaged. Wind load in the greenhouse is the premise for gale disaster prevention and design of facilities’ structural optimization, because wind load of different roof forms is different on sensitivity. It is essential to grasp the distribution rule of wind load on greenhouse surface comprehensively, which is significant for optimized design of greenhouse environment and greenhouse selection.Because China has wide areas and unique geographical features, the selection of greenhouse structure and the calculation of wind load has no the same standards and modes. It is necessary to adopt the suitable greenhouses’structure according to the specific conditions and local climate geological conditions. Computer technology has gained a rapid improvement, especially in the theory of computational fluid dynamics. Numerical simulation technique has overcome weakness, such as traditional wind tunnel test conditions are single, the actual structure is large scale and high Reynolds number and so on. The unique advantage is obvious in the structure wind load characteristics researches. This paper summarizes the current development situations about global greenhouses and computational wind engineering, especially concerning the development about greenhouses’ wind load characteristics. On the basis of other researchers’ results, this paper has done numerical simulation study aiming at a few representative greenhouses’ wind load characteristics. In order to explore distribution rule of wind load in the different greenhouses, provide theoretical foundation for greenhouse selection in the mountainous areas on different wind load and offer scientific, reasonable, accurate and safe proof for greenhouse’s design and optimization, relevant experiments have been done to promote greenhouse’s development.This paper is mainly based on Fluent software of CFD Computing platform, carrying on the numerical simulation analysis of three different kinds of roofs, which are the arch, the spire and Venlo type, in the form of points1,3,5. The distribution of wind pressure and the corresponding coefficient is simulated across at0°,30°,60°and90°direction Angle of the roof respectively. Through the researches about wind load characteristics in the three types of greenhouse roof and coefficients comparisons among different kinds of roofs, the following conclusions could be made:(1) This simulation combined researches on CFD software simulation and engineering practice, with less cost and shorter time to obtain the valuable research conclusions, which is an economic and effective research method. And the advantages of CFD is obvious.(2) On the basis of the predecessors’researches, this paper selected the Realizable k-epsilon model and the class II site types as the common basis for researches, according to our country’s greenhouse. The conclusion is that in the0°and90°wind direction Angle, namely greenhouses windward faced into the wind direction and the direction is vertical and tangent. Flow separation of loss distribution along the flow direction is the form of columnar vortex. Behind the wind direction, the negative pressure condition took place. And the increasing change of negative pressure in the corner, the negative pressure gradient is large.(3) At the same direction angle and the same wind conditions, greenhouse surface wind pressure coefficient is different in different spans.1across has the largest positive pressure and negative pressure, across different.5,3and10across’is smaller, but not so much.(4) Inclined wind flow is the most unfavorable working condition. At the Angle of30°and60°of wind flow, negative high pressure is formed around the corner of the rear region, where arch type, peaked and Venlo greenhouse roofs contact flow, increase more than0°and90°obviously.(5) Different roof forms have different sensitivity to the same wind load. In three different types of greenhouses, spire model greenhouse is least sensitive to the wind load, and arch model greenhouse is most sensitive to the wind load, and Venlo greenhouses’sensitivity is in the middle of them.