Effects of the slatted floor layout on flow pattern in a manure pit and ammonia emission from pit-A CFD study

Abstract As an interface between the animal occupied zone and the manure pit, the slatted floor has significant influences on gaseous emissions in livestock buildings. Airflow motion above the floor may affect the air motion in manure pit under the slatted floor. This work aimed to investigate the effect of slatted floor layouts on the airflow pattern in a manure pit and the corresponding ammonia emission from the pit by means of the Computational Fluid Dynamics (CFD) simulations. Firstly, airflow patterns of the 1:8 model and 1:1 model under the same Reynolds number and jet momentum ratio conditions were compared. Then, airflow patterns and ammonia emission rates of the 1:1 model with both parallel and perpendicular slatted floor layouts in various velocities (from 0.1 to 1.6 m s−1) were investigated. The results showed that the airflow patterns between 1:8 and 1:1 model were different when either the Reynolds number or the jet momentum ratio was same. On the other hand, the flow pattern in the pit with parallel floor was very different from that in the pit with perpendicular floor, resulting the ammonia emission rates different. For the cases with the free stream velocity of greater than 0.8 m s−1, perpendicularly arranged slatted floor released less ammonia from pit than the parallelly arranged slatted floor did (up to 39.0% less when free stream velocity was 1.6 m s−1). When the free stream velocity was lower than 0.8 m s−1, the perpendicular floor layout resulted in more ammonia emission than the parallel floor layout. It was concluded that the scale effect should be carefully considered during scale model experiments and the layout of slatted floors should be properly designed based on the air velocity in the animal occupied zone.