Investigation of ventilation opening positions effect on the airflow inside and outside of a greenhouse
The wind flow over a greenhouse structure is a complex and complicated phenomenon which mainly depends on the wind characteristics (speed, direction etc.), the geometry of the structure and the type of the greenhouse. One of the main stress factors of the bearing structure of the greenhouse is the wind. For the calculation of the wind load, the wind pressure coefficient (cp) is used. A high pressure coefficient value leads to an increase of the construction weight and subsequently to an increase in the construction cost. This value must satisfy two requirements: the safety of the structure and a reduced construction cost. The ventilation flow pattern is the link between the outdoor environment and the agriculture structures microclimate. The experimental studies require expensive technical facilities and are often supplemented with numerical approaches based on modeling. Computational fluid dynamics (CFD) provides an alternative approach to calculate ventilation rates and detailed airflow distributions in and around greenhouses. The aim of this work was to investigate how the ventilation openings position affects the pressure coefficient values inside and outside of a greenhouse. Therefore, a CFD study was conducted to investigate the influence of steady flow in different Reynolds numbers on local pressure coefficients computed on a single duo pitched roof greenhouse with and without ventilation roof openings. The Navier-Stokes and continuity equations were solved numerically with the finite element method (Galerkin Method) in order to simulate the two dimensional, incompressible, viscous air flow. Numerical results, such as streamlines, distributions of stream wise (u) and crosswise (v) velocities, as well as the distributions of the pressure coefficient are presented in detail.
Fragos, V.P., Kateris, D., Ntinas, G.K., Firfiris, V. and Kotsopoulos, T.A. 2017. Investigation of ventilation opening positions effect on the airflow inside and outside of a greenhouse. Acta Hort. (ISHS) 1170:151-158
natural ventilation, computational fluid dynamics (CFD), scale models, Navier-Stokes equations, finite element method