On the shear lift force acting on heavy particles in a turbulent boundary layer

Our work treats the problem of the heavy particle behaviour in a turbulent boundary layer, by means of a Lagrangian stochastic model. We focus on a question, whether the shear lift force can be neglected in the numerical simulation of the particle take-off in the turbulent boundary layer. We also compare two different expressions derived for this force, The first one was derived by Saffman (1965, Journal of Fluid Mechanics 22(2), 385-400) for a spherical particle in a shear layer and its validity was later extended by Mei (1992, International Journal of Multiphase Flow 18(1), 145-147). The second one was obtained by Cherukat and McLaughlin (1994, Journal of Fluid Mechanics 263, 1-18) for a sphere in a wall-bounded shear flow. We found, in reference to an experimental work, that the first form of the shear lift force overestimates the particle mean velocity in the near-wall region and highly underestimates both the longitudinal and normal components of the particle fluctuating velocity. Similar conclusions are obtained when the shear lift force is neglected in the calculations. The second expression for the shear induced lift force includes the effects of the wall and the obtained profiles of the particle mean velocity, particle fluctuating velocity and relative fluid-particle velocity are in good agreement with the experimental data. (C) 2000 Elsevier Science Ltd. All rights reserved.