## 4 Conclusions  
The key findings of this study are as follows:  
* the experimental data on the instantaneous values of air flow velocity in a vertical, conical, flat diffuser for different initial conditions using the thermal anemometry method were obtained;
* the fields of averaged velocities in a vertical diffuser for different boundary conditions were presented, where the initial flow velocity had a noticeable effect on the velocity distribution in the vertical diffuser;
* the turbulence intensity fields TI in the vertical diffuser were presented; the TI values had a wide range of variation from 0.05 to 0.92; an increase in the initial flow velocity (from 0.4 m/s to 2.22 m/s) caused a drop in TI by an average of 15%; and the value of the initial flow velocity modified the turbulence intensity fields in the vertical diffuser;
* the change in TI along the downstream diffuser axis was shown, where the dependence TI = \(f\) (_h_) was nonlinear and was determined by the initial flow velocity;
* the spectral analysis of the function \(w_{x}=f\) (\(\tau\)) along the vertical diffuser height was performed. The dominant frequencies of the velocity pulsations f decreased from 52 Hz at \(h\) = 50 mm to 9 Hz at \(h\) = 630 mm. This indicates the predominance of large-scale turbulent structures downstream. The amplitudes of the velocity pulsations \(A_{w}\) at the dominant frequencies increased from a minimum of 0.021 m/s at \(h\) = 50 mm to a maximum of 0.095 m/s at \(h\) = 350 mm. This is due to the development of hydrodynamic instabilities and recirculation zones. The amplitude decreased due to turbulence dissipation for \(h\) > 350 mm.  
The obtained data can be used in various fields of science and technology to refine the design methods of devices with vertical conical diffusers. The described results also deepen the database on the gas-dynamic characteristics of flows in a vertical diffuser. The described results capture the relationship between the initial flow velocity, the turbulence intensity and the frequency spectrum of pulsations. This data is necessary to improve the methods of calculation and the design of diffusers for various purposes.  
Directions for further research on this topic include studying the gas dynamics of flows in a three-dimensional vertical diffuser, creating a physical and mathematical model, and obtaining data on the flow structure using an optical method--the PIV method. The development of active and passive methods (technical solutions) for controlling the gas dynamics of flows in a vertical diffuser is also a possible scientific task related to this topic.  
Conceptualization, L.P. and A.R.; methodology, L.P. and M.E.; validation, M.E. and V.T.; formal analysis, L.P. and M.E.; investigation, L.P. and M.E.; resources, A.N. and A.R.; data curation, L.P.; writing--original draft preparation, L.P. and M.E.; writing--review and editing, A.R.; visualization, L.P. and M.E.; supervision, A.R.; project administration, A.R. All authors have read and agreed to the published version of the manuscript.  
The research funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) is gratefully acknowledged.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
**Acknowledgments:** The authors would like to thank the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) for supporting this work.