Direct numerical simulation of nanoparticle coagulation in a temporal mixing layer

Direct numerical simulations of coagulating aerosols in two-dimensional, mixing layers are performed. The flows consist of the mixing of a particle-laden stream with a particle-free stream, with and without the presence of a temperature gradient. The evolution of the particle field is obtained by utilizing a sectional model to approximate the aerosol general dynamic equation. The sectional model is advantageous in that there are no a priori assumptions regarding the particle-size distribution. This representation facilitates the capture of the underlying physics in an accurate manner. The growth of particles between d_p = 1 nm and d_p = 10 nm is captured in both isothermal flows and flows with a temperature gradient. Results indicate a reduced growth rate in the core of the eddy. The increased temperature of the particle-laden stream results in an increased growth rate. The growth and stretching of the surface area separating the two streams prevents the particle field from achieving the self-preserving particle-size distribution.