At some wall temperature the substrate is completely wetted by the liquid. At this point, the heat flux reaches its maximum, the critical heat flux (CHF) [13; 14]. This point is marked as CHF in Figure 1a. For even lower substrate temperatures a continuous, fluctuating liquid film is created and expanded. If the temperature significantly exceeds the saturation temperature, the flow in this film is influenced by nucleate boiling, leading to the generation of many small bubbles. These bubbles can significantly enhance the splash and formation of the secondary spray. Figure 1: (**a**) Phenomena of spray impact regimes at different wall temperatures, plotted against the measured heat flux of the wall. (**b**) Picture of drop rebounds from the wall with a temperature higher than Leidenfrost point. (**c**,**d**) Pictures of wetted spots of boiling liquid with a wall temperature below Leidenfrost point. With permission from [11]. In an SCR system, multiple phenomena occur simultaneously. First, a spray is injected into a turbulent flow. The individual droplets in the spray do not only interact with the gas flow, but also with each other, and with the walls of the SCR system. When the spray impinges on the surface, there are various scenarios that depend mainly on the wall temperature and the droplet velocity (see Figure 1) [5]. Under appropriate operating conditions, these droplets can form a closed film and/or leave solid deposits behind. These processes are strongly interconnected. For example, the AdBlue injection causes a decrease in the wall- and gas temperature due to spray cooling. The lower temperature in return then influences the spray wall interaction. Previous studies analyzed individual phenomena such as the urea film formation as a result of the spray-wall interaction and single-droplet-wall interaction [4; 5; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28] to better understand the hydrodynamic processes occurring in the SCR systems. Other studies examine the consequences of wall films in SCR systems, in particular the formation of solid deposits [27; 28; 29]. Nevertheless, a comprehensive understanding of film formation in SCR systems cannot be achieved by examining individual phenomena only. To the knowledge of the authors, the transient properties of AdBlue films, from single droplets to separated wetted regions, and to the formation of a closed film and its subsequent drying, have not yet been investigated in detail under generic conditions. The test rig used for the study presented here is designed to facilitate numerical simulations. Thus, the experimental results are well suited to validate numerical simulations. In the future, solvers validated in this way may be used to investigate further operating points and effects numerically as well. The joint work consisting of experiments on a test rig infrastructure suited for numerical simulations and the validation of such simulations with the experimental results is intended to contribute to understanding film-formation properties as a consequence of all individual phenomena in a generic SCR context. In order to aid design and optimization of SCR systems using computational fluid dynamics (CFD) based numerical analyses, accurate modeling of the film dynamics and deposit formation is particularly essential. Therefore, the proper numerical description of the AdBlue injection and the subsequent spray-wall interaction plays a key role for determining the result of the AdBlue impingement. For numerical modeling and analysis, Reynolds-averaged Navier-Stokes (RANS) based techniques have been widely adopted [4; 15; 23; 30; 31; 32] with limitations describing highly unsteady processes. As discussed above, the interaction of spray droplets with the system walls are governed by the properties of the incident droplets (e.g., size, velocity and incident angle) and the wall properties. Using these parameters, various impact regimes are demarcated in the literature based on comprehensive experimental data [33; 34].