## 4 Conclusions  
This paper brings detailed insight into distribution of airflow at the animal height and near the emission surface as well as airflow characteristics in a scale model of a naturally ventilated dairy building. Computational fluid dynamics (CFD) simulations of air velocity profiles using the standard \(k\)-\(\varepsilon\) model reasonably agreed with the measurements for a 1:100 scale model of a naturally ventilated dairy building inside a large BLWT. Different airflow patterns were observed and airflow rates were calculated under different opening combinations and wind speed conditions using the experimentally validated CFD modelling technique. The conclusions drawn from this study are summarized as follows:  
* Opening combinations play a decisive role in the distribution of fresh air inside the barn. Complete sidewall opening either with door or feeding alley openings in both leeward and windward sides showed better distribution of airflow in the summer season. In Autumn, when the middle part of the sidewall opens, after passing above the resting places and animal walking alley of windward side, major jet diverted at the wall of windward side of the feeding alley. Due to feeding alley wall, the air velocity became weaker when it touched the animal resting floors and walking alleys before leaving the leeward opening. This indicated that animals staying at the leeward side of the feeding alley may have less fresh air than those staying at the windward side.
* Inlet air can be guided by sidewall openings depending on seasonal ambient air temperatures for animal comfort and minimal emission. When opening of the bottom part of the sidewall contributed increased air velocities near emission surfaces. Therefore, the bottom part of the sidewall should not be opened until the cow comfort hampers due to hot summer.
* Different opening combinations showed that airflow rate per m\({}^{2}\) floor area was 1 to 2.5 times higher than when only middle part of the sidewall was opened. Larger sidewall openings resulted in higher airflow rate than the small openings while the effect from ridge opening and door opening were minimal in the perpendicular wind direction.  
Further studies are required to understand wind directions and surroundings effect on the airflow pattern and airflow rate of NVD buildings. Non-isothermal and transient simulations of NVD buildings should be carried out for better understanding of airflow patterns and airflow exchange rate. Further studies are needed to investigate the non-isothermal case with cows and feedstock inside the NVD building. Sensor-based opening control can be introduced in combination with CFD simulation in the near future for better management of airflow.  
Conceptualization, C.K.S., Q.Y. and T.A.; methodology, C.K.S., Q.Y. and D.J.; validation, C.K.S., Q.Y., and D.J.; formal analysis, Q.Y.; investigation, C.K.S., Q.Y. and D.J.; writing--original draft preparation, C.K.S.; writing--review and editing, Q.Y., D.J., S.H., B.A. and T.A.; supervision, S.H. and T.A.; project administration, T.A.; funding acquisition, T.A. All authors have read and agreed to the published version of the manuscript.  
This research was an accompanying study of the research projects \"EmissionsminderungNutztierhaltung\" (EMIDAT/EmiRMin) funded by German Federal Ministry of Food and Agriculture (BMEL) and the Federal Office for Agriculture and Food (BLE) and was financially supported by the Alexander-von-Humboldt Foundation (AvH) for granting fellowship for the first author.  
The authors would like to acknowledge [PERSON] and [PERSON], technicians at the Department of Engineering for Livestock Management at the Leibniz Institute for Agricultural Engineering Potsdam and Bioeconomy (ATB) for their technical and logistical support during the wind tunnel measurements.  
The authors declare no conflict of interest.