Modeling And Interactive Optimization Of Greenhouse Environmental System Based On Computational Fluid Dynamics

In the field of modern agricultural engineering,greenhouse is a complex ecosystem,in which microenvironment parameters play an important role in crop production.Therefore,the modeling and optimization of the greenhouse environment system has been the focus of scholars.In order to promote crop yield and save energy consumption,it is beneficial to optimize the greenhouse environment parameters and provide the optimal setting point for the greenhouse closed-loop control system.This paper make a study of Venlo greenhouse based on mechanical ventilation system in Zhenjiang,Computational fluid dynamics software(CFD)is used to simulate indoor microenvironment under different outdoor meteorological conditions,and the effectiveness of CFD model are verified by experimental data.On this basis,a multi-objective optimization strategy is designed for greenhouse environment parameters based on data interaction mechanism.The main contents are as follows:(1)The greenhouse system is simplified based on the previous research on simulation and physical characteristics of the greenhouse.According to the actual situation of greenhouse,gas turbulence model and solar radiation model are reasonably set up,and the CFD simulation model of greenhouse environment system is established.On this basis,the spatial and temporal distribution of environmental parameters in greenhouse under the influence of ventilation rate and thermal radiation are preliminarily discussed.(2)In order to verify the reliability of the simulation model,the measurement experiment of temperature and wind speed under natural ventilation and mechanical ventilation is carried out,and the experimental results are compared with the simulation results.Comparison results show that the average error and average absolute error of temperature under natural ventilation are 9.6%and 2.3 ℃respectively,the average error and average absolute error of temperature under mechanical ventilation are 6.7%and 2 ℃ respectively,the average relative and average absolute error of wind speed are 21.1%and 0.11m/s.The distribution trend of temperature field and flow field is consistent,and the model is reliable.(3)An interactive optimization framework for greenhouse environmental parameters is designed.CFD simulation module and Matlab optimization module are integrated into optimization framework by interaction module based on C++,multi-objective optimization algorithm is used to optimize the simulation results of greenhouse.Compared to the previous method,this optimization strategy can be used to analyze the environment parameter of space-time distribution characteristics,and has the advantages of optimization of high precision,strong universality.This optimization strategy is based on the spatial and temporal distribution characteristics of the environmental parameters in greenhouse,it has the advantages of high precision and high adaptability.(4)Based on the interactive optimization framework,MOGA and MOPSO are used to optimize the environmental parameters of greenhouse.The control variables are wind speed,air temperature,solar radiation intensity and carbon dioxide injection rate,and the optimal target is temperature suitability,carbon dioxide concentration suitability and fan energy consumption.The comparison results show that both of two optimization algorithms can effectively reduce the environmental indexes in the greenhouse,and the optimization framework can provide useful reference for the actual regulation of agricultural greenhouse.