A UNIF IED EULERIAN THEORY OF TURBULENT DEPOSIT ION TO SMOOTH AND ROUGH SURFACES

Abstract--This paper presents a simple, unified theory of deposition that is applicable for particles of any size, and reproduces very closely experimentally measured variation in deposition velocity with particle relaxation time. Apart from providing physical insight, the theory offers a simple, fast and reliable computational tool of practical use to aerosol engineers. The predictions are at least as accurate as the state-of-the-art particle-tracking calculations but require much less computational time. The theory includes the effects of thermophoresis, turbophoresis, electrostatic forces, gravity, lift force and surface roughness. The theory consists of writing the particle continuity and mo-mentum conservation equations in their proper form and then performing Reynolds averaging. This procedure results in an expression for the particle flux which consists of three distinct erms for each of which a clear physical interpretation is available. The first term is a diffusive flux due to Brownian motion and turbulent fluctuation, the second is a diffusive flux due to temperature gradient (thermophoresis), and the third is a convective flux that arises primarily as an interaction between particle inertia and the inhomogeneity of the fluid turbulence field (turbophoresis). The lift force and electrostatic forces also contribute to this convective flux. It is shown that it is crucial to include the particle momentum equation in the analysis as this gives an estimate of the mentioned convectiv