Computational fluid dynamic time evolution of crop transpiration and heat transfer inside a Venlo greenhouse

The most important factor affecting plant growth and development in greenhouses is solar radiation because, in addition to its indirect effect on the distribution of the greenhouse's internal climate, it governs two important physiological mechanisms of plants, namely the transpiration and photosynthesis. The amount of solar radiation entering the greenhouse depends on the design of the greenhouse, the thermo-physical and optical properties of the material, and the weather conditions, there are important variations in the amount of solar radiation reaching the crop, which strongly impacts climate and therefore crop activity. The aim of this paper is to develop a specific numerical submodel to simulate the distributed transpiration and microclimate inside greenhouses under day-time conditions. The numerical simulation was adopted in three dimensions (CFD), using the computer code Ansys Fluent which is based on solving the Navier-Stokes equations. A turbulence model (k-ε) was used as closure and a bi-band radiative submodel distinguishing short and long wavelength radiations was employed using the discrete ordinates (DO) method to solve the equation of heat transfer by radiation (RTE). Simulations were carried out for a 810 m² greenhouse equipped with continuous roof vents. The analysis focuses on the heterogeneity of the distributions of climatic parameters (speed, temperature and humidity). But the main point concerns the heterogeneity of the radiation reaching the canopy and the latent and sensitive heat flux inside the canopy.