FREE-FLIGHT MIXING AND DEPOSITION OF AEROSOLS

The mechanism for the deposition of spherical aerosols on a wall is investigated in a high resolution direct numerical simulation of low Reynolds number turbulent flow in a vertical channel. A Stokes drag force is used in the equation of motion for the aerosol and the particles are assumed to have no influence on the flow field. A particle deposits when it is one radius from the wall. This occurs mainly by an inertial-free flight from distances outside the viscous sublayer. Particle concentration profiles are presented as a function of time and as a function of distance from the channel walls. It is shown that particles accumulate in the viscous sublayer by turbophoresis and by free flights that do not carry particles to the wall. A new method for identifying free-flight particles is presented and a prediction of free-flight deposition is made using fluid velocity distributions.