Testing of a non-iterative CFD modeling approach for an urban street canyon

In many cities, especially those in the third world, ambient air quality is deteriorating leading to concern about the health of city inhabitants. In urban areas with narrow streets surrounded by clusters of tall buildings, called street canyons, air pollution from traffic emissions and other sources is difficult to disperse and may accumulate resulting in high breathing-level pollutant concentrations. For these reasons it has become important to predict the flow field in urban street canyons. Various computational techniques have been used to resolve these flow fields but these techniques are often computationally intensive. For various situations including the evacuation of populated areas in the event of an accidental or deliberate release of chemical, biological and radiological agents, it is important that models should be developed that produce urban flow fields quickly. A Quasi-Computational Fluid Dynamics (Q-CFD) model has been developed and will be described in this presentation. This models solves the steady-state incompressible Reynolds-averaged Navier-Stokes equations numerically for the street canyon region. The model is fast because it solves only the pressure Poisson equation for a single iteration, which helps to get the solution of the flow field rapidly. In this presentation, we will show comparisons to experimental data and show that the single pressure iteration still leads to reasonable solutions. Since this model solves the Navier-Stokes equations numerically, it responds well to different wind directions and contains more physics than other fast-running empirical models.