On the Use of Computational Fluid Dynamics to Investigate Aerosol Dispersion in an Industrial Environment: A Case Study

Abstract

Aerosol dispersion in the area surrounding an existing biological treatment facility is investigated using large-eddy simulation, with the objective to investigate the applicability of computational fluid dynamics to complex real-life problems. The aerosol sources consist of two large aeration ponds that slowly diffuse aerosols into the atmosphere. These sources are modelled as dilute concentrations of a non-buoyant non-reacting pollutant diffusing from two horizontal surfaces. The time frame of the aerosol release is restricted to the order of minutes, justifying a statistically steady inlet boundary condition. The numerical results are compared to wind-tunnel experiments for validation. The wind-tunnel flow characteristics resemble neutral atmospheric conditions with a Reynolds number, based on the boundary-layer thickness, of Re δ ≈ 2 × 10 5 . The numerical inflow conditions are based upon the wind-tunnel flow field. The predicted decay of both the mean and root-mean-square concentrations are in good agreement with experimental data; at 3 m from the ground, the plume mean concentration 200 m downwind of the source is approximately 2% of the source strength. The numerical data in the near-surface layer (0-50 m from the ground) correspond particularly well with the wind-tunnel data. Tentative deposition simulations suggest that there seems to be little difference in the deposition rates of large (1.8 × 10 −5 m) and small (3 × 10 −6 m) particles in the near-field under the flow conditions considered.

Atmospheric dispersion modelling of bioaerosols that are pathogenic to humans and livestock – A review to inform risk assessment studies

“…An air scrubber at a biological treatment plant as source gave the best fit and resulted in the highest number of cases exposed. In three subsequent studies CFD modelling was applied to investigate whether Legionellae were indeed generated from that specific source (Blatny et al, 2011(Blatny et al, , 2008Fossum et al, 2012). Modelling results were used to select optimal sampling sites in the area, thereby detecting bacteria up to 200 metres downwind (Blatny et al, 2008).…”

“…Three pragmatic approaches were identified from the studies discussed in Section 4, namely the use of: -Arbitrary emission data, thus leading to relative concentration maps (Fossum et al, 2012;Gloster et al, 1984;Lighthart and Frisch, 1976;Sorber et al, 1976;Van Leuken et al, 2015;Wallensten et al, 2010). -Realistic assumptions, such as a release of 10 15 B. anthracis spores (Craft et al, 2005;Isukapalli et al, 2008;Nicogossian et al, 2011;Stuart and Wilkening, 2005), or the use of morbidity, severity and duration of the disease as a proxy for emission (Gloster, 1983)although the reliability may be arguable.…”

On the Convergence and Capability of the Large-Eddy Simulation of Concentration Fluctuations in Passive Plumes for a Neutral Boundary Layer at Infinite Reynolds Number

“…Despite the uncertainties related to the filter and numerical implementation, in recent years LES has become a tool used in many applied atmospheric dispersion studies, including the urban environment, and for critical applications such as the release of toxic gas substances (e.g., Fossum et al. 2012 ; Nakayama et al. 2013 ; Lateb et al.…”

Can statistics of turbulent tracer dispersion be inferred from camera observations of SO<sub>2</sub> in the ultraviolet?

“…Large eddy simulation is nowadays viewed as a popular tool in many applied atmospheric dispersion studies, especially of the urban environment and for critical applications such as the release of toxic gas substances (e.g. Fossum et al, 2012;Lateb et al, 2016). LES provides access to the three dimensional turbulent flow field and it is sometimes used as a replacement for experimental measurements at high Reynolds numbers.…”