Turbulent Plume Diffusion in a Pipe Flow by the PDF Method

Abstract

This paper gives the new simulation results of the axisymmetric point source plume in a fully developed turbulent pipe flow by the Lagrangian Probability Density Function (PDF) method. The Lagrangian velocities of stochastic particles are modeled by a generalized Langevin equation expressed in the cylindrical coordinates. The generalized Langevin equation was originally suggested by Haworth and Pope [Phys. Fluids, 29–2, 387(1986)] and its cylindrical expression was derived by Sakai et al. [JSME Int. J., B39–4, 667(1996)]. For the molecular mixing of the scalar, two different models (i.e. the Dopazo’s deterministic model and the modified Curl’s model) are adopted. The simulated radial profiles of the mean concentration and concentration variance by two models show good agreements with the experimental data by Becker et al. [AIChE J., 15–5, 964(1966)]. It is also shown that the mixing process can be characterized well by the downstream variation of the scalar PDF profile.