The preservation of air quality requires the characterization and evaluation of impacts produced by point sources that emit contaminants and its interaction with wind, climate conditions and zone geometry. Current evaluation tools as AERMOD only offer 2D evaluation with Gaussian dispersion, while the nature of air contaminant dispersion is a 3D phenomenon with thermodynamic components and interactions with terrain geometry.
OpenFOAM is an open source software to perform fluids simulations (like air or water) which allows the incorporation of several flow conditions in a 3D model in time. The software is complemented with free tools like Salome Platform for the geometry processing and ParaView for the results visualization. The OpenFOAM code uses Volume of Fluid (VoF) method, which represents with a higher detail the nature of the phenomenon of contaminant transport in the atmosphere.
We wanted to show the OpenFOAM capacities through a case study, which is the simulation of a chimney. The model is 600 m long, 200 m high and 200 m wide. The chimney is 80 m high and has a diameter of 10 m.
The air flow is aligned to the horizontal axis of higher length. The wind has a velocity of 2 m/s. The chimney is releasing 1200 m3/s of effluent. The effluent is 75°C when leaving the chimney, while the air temperature is 25°C. These parameters have been considered in the model in the kinematic viscosity values. Other parameters used were the diffusivity and the Schmidt turbulence number.
OpenFOAM has several solvers which are appropriate for this atmospheric simulation depending on the conditions needed to be modeled. In this case we have chosen a multiphase solver called twoLiquidMixingFoam which simulates two incompressible fluids.
The contamination plume was simulated for 100 seconds with results interval every 1 second. The model has 49498 nodes and 257944 tetrahedrons. For this type of model it was not necessary to parallelize the process or use multi-core computers. All the modeling work was made in a laptop with Core i5 processor.
Here we show you some animations of the atmospheric effluent.