## 3 Previous Wind Tunnel Studies on NVLBs
### Dispersion Studies  
The effects of an obstacle on airflow and contaminant (CO\({}_{2}\)) dispersion around a model of NVLB was studied by [PERSON] et al. [47]. Their results showed that the obstacle decreases the contaminant concentration downstream of the building. Meanwhile, [PERSON] et al. [48] supported these results by using proposed flow parameters based on the integral values of mean velocity and turbulence intensity, related to airflow momentum in the leeward direction horizontal and vertical plume sizes. Later, [PERSON] et al. [50] observed that contaminated air might reach an upwind livestock building, even if it was generated in a downwind livestock building. This phenomenon was observed when the buildings were placed at a separation distance equal to their average height. The study of [PERSON] and [PERSON] [49] first reported fully simulated ABL characteristics in their dispersion study focused on a pig barn. This means that they simulated the velocity and turbulent profiles (including roughness length) and the longitudinal integral length scales and spectrum of turbulence, which corresponded to a rural terrain at a scale of 1:400. The main goal of their study was to simulate the dispersion of odorants from a ventilation system of a pig barn to its surroundings and to investigate the unsteadiness of this dispersion. Using a fast flame-ionisation detector (FFID), they proved that the instantaneous behaviour of the dispersion process could be modelled in a wind tunnel if ABL turbulent properties were carefully replicated. They pointed out the danger of the short averaging times used during in situ experiments, as the scatter in the results could reach more than 100%. The main outcome of their study was the determination of the driving process of the near-field dispersion of odorants from a livestock building. They found that the process is mainly driven by advection (i.e., meandering of the plume) rather than turbulent diffusion. Although they focused on outdoor dispersion, their work demonstrated the importance of wind tunnel studies for studying ABL flow and dispersion phenomena involving livestock buildings. [PERSON] et al. [55] investigated the mean (advective) pollutant transport from a naturally ventilated barn through a natural barrier filter. They aimed to find the optimal placement and configuration of this barrier in order to reduce the transport and dispersion of ammonia from such a building. They found that vertical flow structures of turbulence producedby both the buildings and the ABL moved contaminated air (by a passive gas) to higher altitudes, where it was dispersed by higher wind speeds and by these structures. Although the turbulent pollution fluxes were not included and integral length scales and spectra of ABL turbulence were not reported, this study provides important insight into pollutant transport around NVLBs. The impacts of the ABL, the presence of animals, and the openings' configuration on the pollutant dispersion within a model of a cattle barn was studied by [PERSON] et al. [57]. While the pollution of the barn was simulated by a ground-level planar source emitting a passive gas at a constant flow rate, the concentration within the building was measured using an FFID. The concentration levels inside the barn decreased proportionally with the increase in the ventilation opening width and, similarly, with a less rough ABL. It was shown that velocity fluctuations are driven by the shear layers of the flow, while the mean concentration gradients drive the concentration fluctuations. The study also demonstrated that the pollutant was not well-mixed within the building in any of the studied cases. A comparison of different methods for identifying the barn ventilation performance showed that a significant underestimation (up to a factor of 5) of the building ventilation may be obtained when using, for example, the ventilation rate index. However, the authors also pointed out the limitations of their study (only the passive pollutant and only one wind direction were simulated).