CFD Modeling of Airflow in a Livestock Building

In this paper, a 2D simulation for a typical livestock building is performed to assess the ammonia emission removal rate to the atmosphere. Two geometry models are used and compared in order to represent the slatted floor. In the first model the floor is modeled as a slatted floor and in the second model the traditional porous media is used. The results show that the porous floor modeling over predicts the ammonia emission by a factor of 2 compared to the slatted floor modeling. The results also show different velocity distribution under slatted floor. This suggests that modeling the slatted floor as openings or slats is necessary even though it will result in an increased computational cost. To reduce the number of grid points needed, a multi-domain mesh is used with variable resolution cells in each domain. Interface conditions are used along the boundaries of the adjacent domain. After exploring the accuracy of the porous jump assumption by comparing the velocity, and ammonia concentration in a 2D simulation, heated solid bodies are added to represent the livestock in the following simulations. The results of simulations with heat source also indicate that modeling the slatted floor with slats is necessary. Furthermore, the combination of low inlet velocity and heated objects causes the flow to be buoyancy dominated and unsteady. This unsteadiness can be common in similar buoyancy induced flows for high Rayleigh number flow. The paper concludes with tradeoffs suggested for simulation of livestock buildings.