Wind-Induced Interference Effects And Wind Pressure Characteristics Of Arched Plastic Greenhouse Group

Arched plastic greenhouses are widely used in agricultural production.They are typical wind load-sensitive structures.Wind loads are often important control loads when performing structural calculations and disaster analyses.Wind-induced interference effects commonly occur among an arched plastic greenhouse group and affect the wind pressure distribution.To describe the change law of wind-induced interference effects,the influence of wind-induced interference effects on the wind pressure characteristics and wind pressure ventilation,and finally determine the wind load shape coefficients considering the interference effects,we conduct a series of numerical simulations based on proven computational fluid dynamics(CFD).Combining the Reynolds-averaged N-S equations and the Realizable k-? turbulence model,the surface average wind pressure of the models for single greenhouse and greenhouse group under different wind direction angles(0,30,45,60 and 90 degrees)and distances(2,4,6,8,10 and 12 m)is studied separately.This paper relies on the Arched Plastic Greenhouses Structure and Environmental Regulation Project of the National Bulk Vegetable Industry Technology System(CARS-23-C04).In combination with the actual production and application,the researched greenhouse is a widely used greenhouse type in China(the rise-span ratio is 3:8)and the greenhouse group model is constructed with 5 rows and 6 columns symmetrical layout.According to the wind pressure characteristics and wind-induced interference effects,this study aims to optimize the design parameters of the arched plastic greenhouses structure,evaluate the ventilation environment of the greenhouse group area,and then provide references for the wind load value,planning layout and the revision of relevant technical specifications of the greenhouse group.This paper studies wind pressure characteristics by visual means such as mean wind pressure coefficients distribution maps,quantitatively analyzes interference effects with interference factors,and measures overall ventilation effects with changes in wind pressure coefficients.The results show that:(1)The arrangement of greenhouse group causes the wind-induced interference effects,which will change wind pressure characteristics of the greenhouses.Compared with single greenhouse,the arched plastic greenhouse group forms the windinduced interference effects.Among them,there are amplification effects in the outer area of the greenhouse group,and the shielding effects are the main area in the middle of the greenhouse group.The interference effects are significantly affected by the wind direction angle and the gap distance,and specifically they decrease with the increase of distance.For the type of greenhouse studied,the effects tend to be stable but still exist when the distance between greenhouses is about 10 m.(2)The arrangement of greenhouse group weakens the wind pressure ventilation ability of the greenhouse group.The shielding effects caused by the arrangement of greenhouse group are not conducive to the wind pressure ventilation,and the changes of the incoming wind direction angle and the gap distance will obviously change the wind pressure characteristics of the greenhouse group and affect the ventilation ability.Considering that the shielding effects cannot be avoided under the arrangement of greenhouse group,the suggestions on planning and layout of the greenhouse group are put forward from the perspective of facilitating wind pressure ventilation and improving the wind environment of greenhouse group,that is,the long axis direction of the greenhouses should be perpendicular to the dominant wind direction in summer of the area where the greenhouse group is located and the gap distance should be increased appropriately.(3)The wind load shape coefficients for arched plastic greenhouses should consider the influence of wind-induced interference effects comprehensively.Based on the study of the interference effects,and referring to the assignment method of the “Code for the Design Load of Horticultural Greenhouse Structures”(GB/T 51183-2016),the wind load shape coefficients for arched plastic greenhouses(the rise-span ratio is 3:8)are given,which are convenient for design.The wind load shape coefficients of greenhouses which are located in the outer area of the greenhouse group: At 0 wind direction angle,+0.42 on the windward side,-0.78 on the middle roof,-0.26 on the leeward side and-0.48 on both sides of gables;at 90 degrees wind direction angle,+0.45 on the windward gable,-0.44 on the roof.The wind load shape coefficients of greenhouses which are located in the middle area of the greenhouse group: At 0 wind direction angle,+0.30 on the windward side,-0.71 on the middle roof,-0.26 on the leeward side and-0.48 on both sides of gables;at 90 degrees wind direction angle,+0.34 on the windward gable,-0.35 on the roof.This paper takes actual engineering in agricultural production as the background,and through the research on wind-induced interference effects and wind pressure characteristics of the greenhouse group,it proposes the wind load shape coefficients considering wind-induced interference effects and planning layout suggestions based on the dominant summer wind direction of greenhouse group.The research results can provide reference for the value of wind load,planning layout and the revision of relevant technical specifications of the greenhouse group.