New turbulence models for air pollution problems

Computationally efficient turbulence closure schemes are formulated and evaluated. A relatively simple Eulerian diffusion model has been developed. In this model, the K -closure formulation and the E-s turbulence model are incorporated. Consequently a value of the turbulent diffusivity exhibits the expected increase with a distance downstream a ground-level source in a turbulent boundary layer. For modelling the dynamics of the convective planetary boundary layer and pollutant dispersion, a new set of equations for the second- and third-order moments is derived. In the new suggested second-order closure model the vertical turbulent transport is emphasized, that is the turbulent velocity variance 〈 w 2 〉 the variance of turbulent temperature fluctuations 〈 θ 2 〉, the horizontal turbulent kinetic energy and the spectral consumption s of the turbulent kinetic energy (TKE) E are calculated from differential transport equations, whereas other second- and third-order moments necessary for closure are found from algebraic expressions. In the third-order closure model the triple correlations 〈w 3 〉 and 〈 w 2 θ 2 〉 are determined from differential transport equations.