Numerical simulation of the Lagrangian transport of aerosols of various genesis in urban conditions

This work is devoted to the development of a numerical model of the transport of aerosol particles in the atmospheric boundary layer, as well as its application in idealized cases and studies with a realistic urban surface. Air quality and the distribution of pollutants is one of the major urban problems, and measurement methods can be limited in the complex geometry of the city, which motivates the development of modeling methods.

The model uses the Lagrangian approach to modeling, taking into account the size and mass of each particle, the possibility of aerosol deposition and their collision with various surfaces. The particle motion equation takes into account various parameters of the atmosphere: wind direction and speed, turbulent characteristics. The influence of turbulence on the motion of aerosols can be taken into account in the model using several parametrizations – stochastic Lagrangian models of zero and first order. It is possible to simulate a huge number of particles at the same time. The algorithm is implemented in the C++ programming language.

The model can be used as a separate tool that requires information about the state of the atmosphere as input data - these can be measurement data, results of hydrodynamic modeling, analytically given values. Numerous experiments have been carried out in this mode. The model was verified on exact analytical solutions for light and heavy particles, on the data of field measurements of the concentrations of dust and sand particles. Calculations were carried out in conditions of idealized geometry of buildings (urban canyons) and in conditions of real urban development. For this, input data from RANS and LES models were used.

The developed algorithm can also be used as a module connected to hydrodynamic models. In this mode, it is possible to use the input data on atmospheric parameters with the maximum resolution in time and space. By connecting to the LES model, high-resolution simulations of aerosol transport in realistic urban environments were performed.

The work is supported by Russian Ministry of Science and Higher Education, agreement No. 075-15-2021-574 (megagrant leaded by M.Kulmala in Moscow State University, WP4), No. 075-15-2019-1621, by RSF grant 21-17-00249, by RFBR grants 20-05-00776 and 19-05-50110.