A Mass Conserving Wind Model Evaluation With Finite Element

Abstract: This work describes a method of approximating a wind field for an urban environment for the purpose of dispersion modelling. Instead of using the classic Navier Stokes equation, a mass conserving wind model is evaluated. The model uses an empirical diagnostic study to approximate a stationary windfield that is forced to be convergence free using a least square variational technique. This work has shown that there is a way to approximate the mass conserving wind field for a large urban environment using Comsol Multiphysics and the Finite Element Method. Compared to wind tunnel experiment the large features of the main flow are present but the wind speed is underestimated. Among the iterative solvers tested Multi grid and Conjugate Gradient performed best. An urban city with 2 100 000 degrees of freedom had a solution time of around three minutes.