Numerical simulation of natural ventilation in greenhouses: a comparison between finite volumes method and finite elements method.

摘要

Modelling of greenhouse climate published to date has used several computer fluid dynamic programs based on the finite volumes method (FVM). Although few commercial packages are based on the finite elements method (FEM), this has also been successfully used to model the wind and structure interaction in greenhouses. However, no comparison has been made of the codes solving the same equations governing natural ventilation of greenhouses (benchmark test), and the goal of the present contribution is to compare the numerical results calculated with a FVM program (Fluent v. 6.1.) and FEM software (ANSYS/FLOTRAN v. 9.0.). Although the equations are similar, the handling of the boundary conditions, the interpolation functions, and other numerical techniques such as the use of pressure or the iteration scheme are different. Simulation results have been compared with experimental observations in two different cases: (i) a reduced-scale single-span greenhouse with adiabatic walls was used to compare airflows and temperature distributions and (ii) air exchange rate was measured in a four-span experimental greenhouse for low wind velocities and temperature gradients. The simulated results for temperature and dynamics fields are compared with the experimental measurements with respect the meshing facilities, convergence time and the initial set of state variables. Based on this benchmark test in two dimensions, recommendations are provided for the use of each method.