## 3 Previous Wind Tunnel Studies on NVLBs
### The Flow Studies
#### 3.1.1 The Effect of Openings
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Study**} & **Poll. Source** & **1x** & **ABL** & **Indoor** & **Outdoor** & **Indoor** & **Outdoor** & **Main Findings** \\ \hline [PERSON] & & & & & & & Windbreak panels at the openings \\ et al. [42] & & 20 & x & x & & & improve the pig barn ventilation. \\ \hline [PERSON] & & & & & & & The position of the ventilation \\ et al. [43] & & 20 & x & x & & & opening is most important for local \\ \hline [PERSON] & & & & & & & air velocities in the animal zone. \\ et al. [47] & Point & 20 & & & & & x & An obstacle upstream of the barn \\ et al. [47] & & 20 & & & & x & & decreases the contaminant \\  & & & & & & & concentration downstream. \\ \hline [PERSON] & & & & & & & & A solid windbreak, as well as a \\ et al. [48] & & 20 & Partially & x & x & & & may, positioned upstream of the \\ et al. & & & & & & & investigated barn caused the air to \\ et al. & & & & & & & flow towards the windbreak or the \\ et al. & & & & & & & upstream barn. \\ \hline [PERSON] & & & & & & & & The near-field pollutant dispersion \\ and Leitl [49] & Point & 400 & Fully & & & & & from a building is mainly driven by the \\ et al. & & & & & & & the meandering behaviour of the \\ et al. & & & & & & & plume rather than the \\  & & & & & & & turbulent diffusion. \\ \hline [PERSON] & & 20 & Partially & x & x & x & x & A contaminant might reach an \\ et al. [50] & Point & 20 & Partially & x & x & x & x & & upward NVE, even if it was \\ et al. & & & & & & & generated by a distance equal to the \\ et al. & & & & & & & & NYLB’s average height. \\ \hline [PERSON] et al. & & & & & & & & & Perpendicularly oriented buildings \\ [51] & & 300 & Partially & x & & & & height of the mean building zone \\ et al. & & & & & & & of reduced streamwise velocity and \\ et al. & & & & & & & increased turbulence intensity in the \\ et al. & & & & & & & wake of the buildings. \\ \hline [PERSON] & & & & & & & Animal barns themselves had the \\ et al. [52] & & 150 & Partially & x & x & & & greatest impact on the flow patterns \\ et al. & & & & & & & than vegetative environmental \\ et al. & & & & & & buffers (e.g., trees or shelterbetts). \\ \hline \hline \end{tabular}
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Table 3: Related wind tunnel studies on naturally ventilated buildings. The main objective of [PERSON] et al. (2018) was to investigate the effects of the sidewall opening configurations on internal airflow fields and air velocity characteristics within the animal-occupied zone using an LDA method. They observed an up-jet airflow pattern within the building when the opening ratio was no greater than 62.71% and was located  
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\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
beenath the eaves. They also studied the opening configuration where the openings were at the bottom and constituted 44% of the entire sidewalls. In this case, uniform airspeed distributions were observed in the animal-occupied zone. They concluded that care should be taken when using these kinds of opening configurations during extreme cold and windy weather conditions. [PERSON] at al. [56] investigated the impact of the size of the openings on the discharge coefficient (Cd). They found that the Cd value is mainly dependent on the opening size for large opening configurations and not constant, as has been assumed in previous studies. Therefore, an inaccurate application of constant Cd may lead to severe errors in predicting the airflow rate in NVLBs. [PERSON] et al. [57] analysed the evolution of flow patterns within a barn using the TR-PIV method. Their results showed that the sidewall opening height and the type of ABL have a crucial impact on the flow within the barn. The size of the openings also has an impact on the coherent structures of the turbulent flow, which manifested as the well-known Kelvin-Helmholtz instability, due to the developed shear layers at the inlet openings. Larger openings produce more stable turbulent structures within the barn.