Towards simulating urban canyon circulations with a 2D lattice Boltzmann model

The Lattice Boltzmann (LB) method is a novel fluid modelling technique developed from cellular automata. Instead of numerically solving the continuum Navier–Stokes equations, it simulates the interactions of mesoscopic particle populations pα using discrete speeds and positions to obtain the macroscopic velocity, density and temperature fields. Localised at neighbouring grid nodes, the method handles complex geometries and multiple fluids more easily than traditional continuum CFD methods.Rothman and Zaleski (Lattice-Gas Cellular Automata: Simple Models of Complex Hydrodynamics (1997) Cambridge University Press, Cambridge) discuss LB method theory and development in more detail. To demonstrate the power of the technique, a 2D LB model is first used to perform urban canyon configuration studies at Reynolds number Re 100 for Height to Width (H/W) ratios from 0.125 to 2. Then, thermal lid driven cavity simulations for Re 100 and Rayleigh number Ra 2000 are performed for different locations of a relatively hot wall. The simulated flow fields appear qualitatively consistent with physical flows observed in wind tunnel and field studies, and indicate that LB methods generate results comparable to traditional CFD methods for the selected flow situations.