Light scattering and absorption properties of aerosol particles in Hong Kong

The constitutive relation for the particle Reynolds normal stress in the presence of the memory effect are derived in a form usable in the Eulerian transport equation through averaging the particle-turbulence interactions over an intermediate diffusion time scale. The memory effect in the aerosol deposition in a two-dimensional fully developed turbulent channel flow is estimated by applying the constitutive equation into the turbophoresis term. The calculated results reasonably predicted that with the memory effect a high level of fluctuating particle velocity is maintained down to much closer to the wall than with the simple equilibrium model, and an additional drift velocity towards the wall is induced very near the wall (y+ ~ 8). In the diffusional-impaction regime (0.3<(tau)p+<30), the additional drift velocity augments the deposition of particles densely accumulated in the viscous sublayer. All the calculated results are in good agreement with the available, though limited, experimental and numerical data.