A working model for particle deposition in turbulent flow

The free flight model of particle deposition from the core of a turbulent flow on to a wall relies on the assumption that a particle starts its flight from the correct distance away from the wall. Approximate agreement with experiment is only obtained by resorting to dubious assumptions. In this paper the idea of the frequency response of a particle to turbulent fluid motion is utilised to show how the ʹcut off distance yc at which the particle begins its free flight is related to the particle and flow parameters. Experimental data are used in conjunction with theoretical arguments to show that the dimensionless cut off distance, y+c, can be correlated by an expression of the form y+c = B(d+p)2 exp(αS) where d+p is the dimensionless particle diameter, S is the ratio of particle to fluid densities, and B and α are dimensionless constants. For air carrying small particles, the constants take the values 18.1 and 2.97 × 10−4, respectively.