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-epsilon 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 [theta(2)], the horizontal turbulent kinetic energy and the spectral consumption epsilon 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)theta] are determined from differential transport equations.