# Experimental Device to Evaluate Aerosol Dispersion in Venues
## 2 Materials and Methods
### CFD Simulations  
To support the experimental measurements and to arrive at a full understanding of the aerosol distribution in the venues, CFD simulations were performed. The non-isothermal, steady-state CFD simulations of the three venues were conducted on unstructured grids using Simcenter(tm) STAR-CCM+ (version 2021.2-2310). The modelling of the venues closely followed construction plans, walkthroughs, and additional information from the technical staff on site. Heat sources such as persons (assumed 80 W each), lighting, and production equipment were remodelled to match the measurement configuration. Supply air and the outside temperature were chosen based on the conditions at the day of the respective experiments. Further boundary conditions are added in Table 11. The mesh design relied on base sizes between 0.1 m and 0.3 m, with local refinements throughout the venue but especially close to heated or geometrically complex surfaces, and 4-6 prism layers were applied to support the near-wall modelling. In total, grid sizes ranged from 3.5 to 12 million finite volume cells. Mesh sensitivity was analysed for one venue (DVV) of the project where the passive scalar, temperature, TKE and momentum monitor values for three grids of increasing refinement (with base sizes of 5 cm, 10 cm, 20 cm) were observed. The differences in these monitor values were increasingly insignificant. Therefore, we chose the medium mesh density at the 10 cm base size (including prism layers and local refinements) as a reasonable trade-off. Air was treated as an incompressible, ideal gas where buoyancy effects were directly determined by the gravity model. Transport equations of flow and energy were solved with a segregated solver using the SIMPLE algorithm. Grey thermal, surface-to-surface radiation was used in combination with the segregated fluid temperature model. The realizable K-\(\epsilon\)-model with a two-Layer formulation (Wolfstein) was applied as a two-equation RANS-model. Simplified mouth regions model the inlets of the tracer aerosol, where momentum-free passive scalars enter the fluid domain. For each emitting person (equivalent to aerosol generator), a separate passive scalar equation was solved.  
Figure 5: Experimental and simulated results of the NVV. In the 3D visualization, the yellow dummy represents the position of the aerosol generator measured with the experimental setup. The cloud over the yellow dummy is showing the aerosol plume dispersing in space, calculated from numerical data. In Case A, the aerosol generator is positioned in the first row A14. E shows the position of the aerosol generator; numbers 1-7 the position of the absorbers. Absorber 1 is marked with a black cross in the 3D visualisation to indicate its position.  
The volume-averaged concentrations of the respective tracer within the hemispherical volume around the absorber's mouths (r = 0.23 m) were calculated and compared to the corresponding experimental value. Since the experiments relate the absorbed amount of NaCl to the emitted amount, a similar approach was chosen for the evaluation of the steady-state absorption of the tracer aerosol.