CFD study on the impacts of geometric models of lying pigs on resistance coefficients for porous media modelling of the animal occupied zone

Computational fluid dynamics (CFD) has been widely used for studying the indoor environment of livestock houses. However, the detailed geometrical models of pigs in commercial pig production houses induce extremely high grid numbers which require huge computational capacity. Therefore, simplifying the pigs in the occupied zone into porous media model is an alternative. To use the porous media model, the resistance coefficients need to be determined. In this study, the influence of different geometric models of lying pigs under various body mass on resistance coefficients was investigated. Three simple geometric lying pig models (ellipsoid model, half ellipsoid model and half cylinder model) under different body masses (30 kg, 45 kg, 60 kg, 75 kg, 90 kg and 105 kg) were used to identify which type of simple geometric models could represent the simplified lying pig model by comparing the obtained resistance coefficients. Meanwhile, the relationship between the body mass and the resistance coefficients was also analysed. The results showed that the resistance coefficients were affected by different simple geometric models of pigs and the half ellipsoid model was the most suitable model to replace the simplified pig model. In addition, the pressure drop per unit length increased with the rise in body mass at the same air velocity and the increase was more significant at larger body mass with the same rise in body mass. The inertia resistance coefficients and body mass were highly correlated to each other. The resistance coefficients obtained in this study can be used in the indoor environment simulation of fattening pig buildings.