A LAGRANGIAN SIMULATION OF PARTICLE DEPOSITION IN A TURBULENT BOUNDARY-LAYER IN THE PRESENCE OF THERMOPHORESIS

Knowledge of particle deposition in turbulent flows is often required in engineering situations. Examples include fouling of turbine blades, plate-out in nuclear reactors and soot deposition. Thus it is importa nt for numerical simulations to be able to predict particle deposition . Particle deposition is often principally determined by the forces ac ting on the particles in the boundary layer. The particle tracking fac ility in the CFD code uses the eddy lifetime model to simulate turbule nt particle dispersion, no specific boundary layer being modelled. The particle tracking code has been modified to include a boundary layer. The non-dimensional yplus, y(+), distance of the particle from the wa ll is determined and then values for the fluid velocity, fluctuating f luid velocity and eddy lifetime appropriate for a turbulent boundary l ayer used. Predictions including the boundary layer have been compared against experimental data for particle deposition in turbulent pipe f low. The results giving much better agreement. Many engineering proble ms also involve heat transfer and hence temperature gradients. Thermop horesis is a phenomena by which small particles experience a force in the opposite direction to the temperature gradient. Thus particles wil l tend to deposit on cold walls and be repulsed by hot walls. The effe ct of thermophoresis on the deposition of particles can be significant . The modifications of the particle tracking facility have been extend ed to include the effect of thermophoresis. A preliminary test case in volving the deposition of particles in a heated pipe has been simulate d. Comparison with experimental data from an extensive experimental pr ogramme undertaken at ISPRA, known as STORM (Simplified Tests on Resus pension Mechanisms), has been made. (C) 1998 Elsevier Science Inc. All rights reserved.