Capturing aerosol droplet nucleation and condensation bursts using PISO and TVD schemes

A mathematical model for single-species aerosol production and transport is formulated, and solved using an adapted PISO algorithm. The model is applied to a laminar flow diffusion chamber, using a finite volume method on a collocated grid. In tran- sient simulations, a sharp scalar front (e.g., vapor mass fraction), is shown to introduce unphysical oscillation in the solution, when applying a second order linear interpolation in the convective terms. At increased grid resolution, these oscillations are strongly at- tenuated. When applying a TVD scheme (here the MUSCL scheme), a time-accurate monotonicity-preserving solution is obtained. The numerical dissipation introduced by the MUSCL scheme implies increased spatial resolution to restore high accuracy levels. We develop a one-dimensional grid refinement algorithm, which relates the grid density in one direction to the magnitude of the scalar gradient. In combination with the MUSCL scheme, this gives accurate results, with a significant reduction in computational effort, in comparison with a uniform fine grid.