CFD simulation of greenhouse microclimate and crop transpiration under water restriction conditions

Abstract : In greenhouses, reducing water consumption by increasing water efficiency is of high interest. To reach this goal, predictive models of soil-plant-atmosphere water transfers may be helpful. However, almost all numerical microclimate simulations for potted plants grown in greenhouse were conducted under well-watered condition. Moreover, most models were developed for open field conditions. The aim of this work is to simulate transpiration and microclimate for plants grown in pots inside greenhouses for well-watered and water restriction conditions. In this prospect a 2D transient CFD (Computational Fluid Dynamics) model was implemented. User defined functions were implemented to take account of the crop interactions with the climate inside the greenhouse. The crop was considered as a porous medium and specific source terms for transpiration and sensible heat transfers were added. A specific submodel was also implemented to calculate the substrate water content based on the water balance between irrigation and transpiration. A particular care was paid to the modelling of the stomatal resistance. In order to get the input data and to validate the CFD simulations, an experiment was conducted during sixteen weeks inside a greenhouse equipped with ornamental plants (New Guinea Impatiens) grown in containers on shelves. Both well-watered and restriction conditions were analyzed. The results of the CFD simulations showed the ability of the model to correctly predict transpiration, air and leaf temperatures as well as air humidity inside the greenhouse for both water conditions. The CFD model could therefore be useful to test different irrigation scenarios and better manage water inputs.