## 4 Conclusions  
In the last decade, flow and thermal analyses of airplane cabins have been performed with experimental and numerical data. Three methods are available for aircraft ventilation: mixing, displacement, and personalized ventilation. Mixing ventilation achieves good air-flow distribution but does little to combat airborne disease transport. In the present study, the authors numerically investigated the possibility of introducing a personalized ventilation diffuser, combined with mixing ventilation, to improve air quality and thermal comfort and reduce the risk of airborne diseases. Humidity is an important part of airborne pathogen transmission. Dry air allows an intensive dehydration of mucosalivary droplets and their transformation into droplet nuclei that can float for a very long time, possibly entering the breathing zone of other passengers. That is why we believe that personalized-ventilation-based solutions that provide fresh and clean air to this breathing zone represent a strategy that is worthy of consideration. A personalized ventilation circuit could also be equipped with a local humidification solution adapted to the needs of each occupant of every seat in the cabin. The aim of the present paper is to study the possibility of using a low-momentum PV system that can penetrate a passenger's convective boundary layer, improving air quality in their breathing zone. A successful implementation of such a PV solution is the first step towards increasing passenger protection against airborne pathogens. This study is part of a larger project including experimental and numerical investigations. Evaluation of the proposed PV solution was analyzed using numerical simulations supported by experimental measurements for validation purposes, allowing us to make preliminary conclusions about the efficiency of such systems. The numerical approach proposes the comparison of two models reproducing a small region inside an aircraft cabin containing four seats with virtual passengers. The jet flow delivered from the PV diffuser has low momentum and is entrained by the convective layer around the body of the virtual manikin in such way that it delivers air to the face of the virtual passenger. The presence of the PV diffuser modifies the distribution of the thermal boundary layer of the passenger at the level of the torso and head. The presence of the convective layer formed around the human body, in combination with the effect of the interaction between the PV jet flow, modifies the air flow patterns in the breathing zone in terms of velocity and temperature. The air-temperature distributions show that the small region corresponding to the potential core, located in front of the face of the passenger, is colder than its surroundings. This could be explained by the fact that the clean air issuing from the PV nozzle has not yet mixed with the ambient air, thus fulfilling its objective. This allows us to make a hypothesis related to the distribution of clean-air concentration. This study represents the preliminary step within a more complex analysis. In our study, we did not take into consideration CO\({}_{2}\) emissions from breathing, for instance, nor did we simulate aerosols. These two factors are to be considered in the next phase of our study. Conceptualization, P.D., C.I.C. and I.N. ; methodology, P.D., C.I.C. and I.N. ; software, C.I.C., F.B., P.D. and M.R.G. ; formal analysis, F.B. ; investigation, P.D. ; resources, C.I.C. and I.N. ; data curation, M.R.G. ; writing--original draft preparation, I.N. ; writing--review and editing, I.N. and P.D. ; supervision, C.I.C. and I.N. ; project administration, C.I.C. ; funding acquisition, C.I.C. and I.N. All authors have read and agreed to the published version of the manuscript.