Numerical study of three-dimensional wind flow over grain storage bunkers

In Australia, grain storage bunkers fitted with covering tarpaulins are widely used. Tarpaulin billowing takes place when it is windy. It is well known that billowing has negative impacts on the life span of a tarpaulin, but also has positive effects on phosphine transport throughout the grain stack during fumigation. It is suspected that preventing billowing during fumigation would retard phosphine distribution to such an extent that contemporary phosphine dispensing protocols risk failure. Mathematically, a moving boundary condition that could represent wind induced tarpaulin billowing presents a challenging technical problem and has not been published. In this study, three-dimensional wind flow around a grain storage bunker is investigated by finite element method (FEM) based computational fluid dynamics (CFD) modelling, as the first step towards quantifying tarpaulin billowing. The Petrov-Galerkin finite element method (PG-FEM) is used to solve the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with a κ-ω turbulent closure. This study is focused on the wind induced pressure distribution and fluctuation on bunker surface at a relatively low Reynolds number of 2,000. The simplification of flow from three-dimensional to two-dimensional at the mid span of the bunker was discussed with cross flow wind direction.