## 2 Materials and Methods
### Simple Theoretical Considerations  
The paper concentrates on fundamental theoretical considerations of droplet movement in a multiphase fluid flow under conditions present in the Venturi nozzle. This is an important issue as the multiphase flow, through a convergent-throat-divergent channel, is used for gas cleaning. This section deals with defining the factors that affect the motion of droplets in two-phase flow. The analysis was performed by employing the original empirical data that was gained into formulas, which are available in the literature [8; 37], and some of them characterize the turbulent flow regime. This preliminary analysis is planned to be developed further and introduced into the mathematical model that the author has been developing. The model concerns the multiphase flow through the diverging and converging channels and the throat of the Venturi. Using the mathematical model, it is possible to determine characteristics of the fluid flow that reveal variations in flow velocity, linear head loss coefficient, wall shear stress, total, local, frictional, and accelerational pressure drop, and absolute and gauge pressure along diverging and converging channels. Multiple mechanisms are responsible for the motion of droplets in the continuous phase. Vapor's molecular or turbulent diffusion can trigger this motion. The rotational movement of droplets can be caused by the gas phase velocity field and its gradients. As a result, the forces that affect the deposition or entrainment of droplets from the liquid film start to occur [38]. The inertia of a moving droplet is determined by the mass of the droplet and the thermodynamic parameters like temperature and pressure of the continuous and dispersed phases as they translate into variations in the physical properties of both media, such as density and viscosity. Because of the droplets' inertia, the velocity field and trajectory of the droplets do not match the velocity field of the gas phase. As they move, droplets coalesce or split and the statistical distribution of droplets in the flow undergoes continuous changes due to this. The paper by [PERSON], [PERSON], and [PERSON] [8] introduces a new concept of the mathematical modeling of mechanisms like diffusion and body forces acting on droplets. These mechanisms have an effect on a quantitative share of droplets in the core of the two-phase flow.An analysis of the movement of a single droplet has led to the obtaining of an equation defining the stopping distance of the droplet. By employing the model, it is possible to estimate the distance to be covered by a droplet until it separates from the mist flow and finally deposits on the channel wall. This path is called the stopping distance (horizontal travel distance) of the droplet. In [PERSON]'s turbulence model, the scale of turbulent vortexes is expressed by the length of the mixing path, \(l_{m}\) (Equation (1)) [8; 37]. However, the scale of the inertial motion of droplet is defined by its stopping distance after gas-droplet momentum transfer. If the path of the turbulent mixing of the gaseous phase  
Figure 1: Scheme of the lab stand where: 1—water supply, 2—Coriolis flow meter (see Appendix D, Table A1), 3—pneumatic air-water nozzle that generates droplets (see Appendix D, Table A2), 4—airflow meter (see Appendix D, Table A1), 5—compressor, 6—Topas LAP 332 (see Appendix D, Table A4), 7—fan, 8—measuring channel (see Appendix B, Figures A1-A3). is longer than the stopping distance of the droplet, then a dispersed phase succumbs to the turbulent diffusion of the continuous phase. Otherwise, if the stopping distance of the droplet is higher in value than the mixing path, the droplet undergoes inertial, turbulent, or turbulent-inertial diffusion. Therefore, both the gas and the droplet diffusion coefficients are analogous as they depend on the mixing path and the stopping distance, respectively. Empirical research has provided a comprehensive set of measurement data and boundary conditions that were applied for theoretical analysis.