# CFD Investigation of Particle Deposition in a Horizontal Looped Turbulent Pipe Flow

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## Abstract

This paper presents comprehensive 3D numerical investigations on depositions of particles flowing through a horizontal pipe loop consisting of four bends. The multiphase mixture model available in FLUENT 6.2 was used in this study. In this numerical simulation, five different particle sizes have been used as secondary phases to calculate real multiphase effect in which inter-particle interaction has been considered. The deposition of particles along the periphery of the pipe wall was investigated as a function of particle size and fluid velocity. The simulations showed that near the upstream of the bends, maximum particle concentration occurred at the bottom of the pipe. However, downstream the bends, the maximum particle concentration occurred at an angle of 60° from the bottom. The larger particles clearly showed deposition near the bottom wall except downstream. As expected, the smaller particles showed less tendency of deposition and lesser at higher velocity. This numerical investigation showed qualitative agreement with the experiments conducted by Commonwealth Scientific and Industrial Research Organisation, Melbourne team for similar conditions.

## Keywords

CFD simulation Numerical investigation Particle deposition Two-phase flow Turbulence## List of Symbols

- \( \vec{a} \)
secondary-phase particle’s acceleration

*C*^{+}concentration of particles

- C
_{f} friction co-efficient

*D*pipe diameter

*D*_{f}fluid diffusivity

*D*_{p}particle diffusion coefficient

*d*_{p}diameter of the particles of secondary phase

- \( \vec{F} \)
body force

*f*_{drag}drag function

*k*proportional constant

*k*_{D}constant

*k*_{n}eigenvalues

*L*Length scale

*l*particle mean free path

*m*_{T}mass transfer

*n*number of phases

*P*Peclet number

*R*_{D}deposition flux

*R*_{e}entrainment flux of the particles

*Re**Reynolds number based on the friction velocity

- Re
_{f} fluid Reynolds number

*S*Stokes number

*t*_{0}initial time

*T*_{L}integral flow time scale

*T*_{P}particle integral time scale

*U*Velocity scale

*u**the friction velocity

- u*
friction velocity

*v*free-flight velocity

- \( {\vec{v}_{{dr,k}}} \)
drift velocity for secondary phase

*V*_{f}pipe average fluid velocity

*v*_{f}*′*fluctuating velocity

*v*_{g}Particle free fall velocity

*v*_{g}gravitational settling velocity of the particle

- \( {\vec{v}_m} \)
mass-averaged velocity of the mixture

- \( {\vec{v}_{{qp}}} \)
relative velocity

- \( \left\langle {v\prime_p^2} \right\rangle \)
particle’s mean square velocity

*λ*_{K}Kolmogorov length scale

*ρ*_{m}mixture density

*ρ*_{p}densities of the particle

*α*_{k}volume fraction of phase

*ε*kinetic energy dissipation

*ɸ*angle around the pipe circumference

- γ
_{cross} crossing trajectories coefficient

*γ*_{inert}inertial coefficient

*λ*free-flight/diffusion ratio

- μ
_{m} viscosity of the mixture

*ν*_{f}kinematic viscosity

*ν*_{f}kinematic viscosity

*ρ*_{f}densities of the fluid

*τ*_{p}particle relaxation time

*τ*_{qp}particulate relaxation time

*τ*_{s}wall shear stress

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