The CAESAR code for aerosol resuspension in turbulent pipe flows. assessment against the storm experiments

The aim of this work is the development of a new model of aerosol resuspens ion in turbulent pipe flows, which is based on the force balance concept. T he model considers both types of aerodynamic forces, drag and lift forces, and properly balances these forces with the frictional and adhesive forces. Original aspects of the new model are that it takes into account the reduc tion of the adhesive force due to the surface roughness and the random incr ease of the lift force above its mean value due to the fluctuations of the turbulent flow. The resuspension model has been implemented in a computer c ode. CAESAR, and its performance has been verified against several experime nts of the STORM programme. In the experiments, the velocity of the how pas sing over the deposits was increased stepwise. Significant particle entrain ment was observed at the beginning of each velocity stage. Then, resuspensi on decreased sharply and became practically zero after a few tens of second s. This behaviour was correctly reproduced with CAESAR, although the durati on of the period of strong resuspension predicted with the code was shorter than the one measured in the experiments. The faster resuspension predicte d with CAESAR is due in part to the fact that the code models the resuspens ion of monolayer deposits in which all particles are exposed to the flow, w hich is not the case of the STORM experiments. (C) 2000 Elsevier Science Lt d. All rights reserved.