Verifying the reliability of CFD domain decomposition technique on modelling the airflow field inside a naturally ventilated cattle barn

Conventionally, the airflow fields outside and inside the naturally ventilated livestock buildings are modelled simultaneously in one computational domain using CFD (Computational Fluid Dynamics). The presence of surrounding buildings, indoor facilities and animals for large scale cattle barns make the required computational power extremely high and even unfordable to achieve simulation results with reasonable accuracy. The Domain Decomposition Technique (DDT), dividing simulations into two separate steps, is an alternative CFD framework to provide sufficient accuracy with affordable computations at each step. The objective of this study was to verify the reliability of DDT on modelling the airflow fields inside a naturally ventilated cattle barn (NVCB) by employing wind tunnel measurements. The exterior airflow fields around the targeted NVCB, which was opened with varying opening ratios, were first simulated to obtain the airflow boundary conditions at sidewall openings by applying exterior wind conditions at the inlet of the computational domain. The interior airflow of the targeted NVCB, were secondly simulated by applying the achieved airflow boundary conditions at sidewall openings from the first step simulation. The interior airflow fields obtained by DDT were in good agreement with wind tunnel measurements. This indicates that DDT can provide an alternative for CFD application in large-scale NVCB with presence of surrounding buildings, indoor facilities and animals, though these had not been considered in this study. Science4Impact Statement This work contributes to simulation technology by providing a novel computational fluid dynamics (CFD) framework which provides sufficient accuracy on optimising microclimate inside naturally ventilated intensive livestock buildings with less computational effort. The conventional CFD framework makes the required computational power extremely high and even unfordable when the presence of surrounding buildings, indoor facilities, and animals were included in one computational domain. The proposed CFD framework, domain decomposition technique (DDT), dividing simulations into two separate steps, makes the individual CFD simulations feasible with available computational capacity when modelling gaseous emissions inside and around cattle barns. Such information can be very valuable as support for scientific advice on regulatory aspects concerning ammonia and methane emission levels at barn level. • Domain Decomposition Technique (DDT) was verified against wind tunnel measurements. • DDT provides reasonable accuracy of airflow inside naturally ventilated cattle barns. • Opening ratios of sidewalls openings affected the accuracy of DDT. • DDT facilitates CFD modelling of airflow inside naturally ventilated cattle barns.