Langevin PDF simulation of particle deposition in a turbulent pipe flow

TL;DR

This paper evaluates a Langevin PDF model for particle deposition in turbulent pipe flow, highlighting the need to incorporate near-wall turbulence structures for improved accuracy.

Contribution

It introduces a phenomenological modification to the Langevin model to account for near-wall turbulent structures, improving agreement with experimental data.

Findings

Standard Langevin model insufficient for near-wall physics

Inclusion of turbulent coherent structures improves predictions

Good agreement with experimental observations achieved

Abstract

The paper deals with the description of particle deposition on walls from a turbulent flow over a large range of particle diameter, using a Langevin PDF model. The first aim of the work is to test how the present Langevin model is able to describe this phenomenon and to outline the physical as- pects which play a major role in particle deposition. The general features and characteristics of the present stochastic model are first recalled. Then, results obtained with the standard form of the model are presented along with an analysis which has been carried out to check the sensitivity of the predictions on different mean fluid quantities. These results show that the physical repre- sentation of the near-wall physics has to be improved and that, in particular, one possible route is to introduce specific features related to the near-wall coherent structures. In the following, we propose a simple phenomenological model that introduces some of the effects due to the presence of turbulent coherent structures on particles in a thin layer close to the wall. The results obtained with this phenomenological model are in good agreement with experimental evidence and this suggests to pursue in that direction, towards the development of more general and rigorous stochastic models that provide a link between a geometrical description of turbulent flow and a statistical one.