Large-Eddy Simulation of Urban Flows: Porous-Media Analogy

In analogy to theoretical formulation for the microscopic fluid flows in porous media [1] we perform series of numerical simulations of urban boundary layer flows through realistic street-level building structures of the Oklahoma City downtown area. The corresponding numerical solutions relate the morphology of the real building structures to topological and geometrical properties of the physical media. We analyze the results in statistical terms of random porous media, seeking the relation between the momentum flux and the macroscopic pressure gradient; i.e., a high-Reynolds-number analogy of the Darcy’s law. We relate urban “pore-space” spatial properties (e.g., homogeneity and anisotropy) to the estimates of permeability and tortuosity. We evaluate further the utility of a porous-media analogy for parameterizing urban effects in the mesoscale weather and air-quality prediction models.