15-dpm - Lecture 15 - Discrete Phase Modeling Applied...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Lecture 15 - Discrete Phase Modeling Applied Computational Fluid Dynamics Instructor: André Bakker http://www.bakker.org © André Bakker (2002-2006) © Fluent Inc. (2002)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Discrete phase modeling Particle tracking. Steady vs. unsteady. Coupled vs. uncoupled. Advantages and limitations. Time stepping. Discretization. Particle trajectories in a spray dryer Particle trajectories in a cyclone
Background image of page 2
3 Discrete phase model Trajectories of particles/droplets are computed in a Lagrangian frame. Exchange (couple) heat, mass, and momentum with Eulerian frame gas phase. Discrete phase volume fraction should preferably be less than 10%. Mass loading can be large (+100%). No particle-particle interaction or break up. Turbulent dispersion modeled by: Stochastic tracking. Particle cloud model. Model particle separation, spray drying, liquid fuel or coal combustion, etc. continuous phase flow field calculation particle trajectory calculation update continuous phase source terms
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 DPM theory Trajectory is calculated by integrating the particle force balance equation: typical continuous phase control volume mass, momentum and heat exchange ( 29 p i p p i p i i D p i F g u u F dt du ρ / / ) ( + - + - = drag force is a function of the relative velocity Additional forces: Pressure gradient Thermophoretic Rotating reference frame Brownian motion Saffman lift Other (user defined) Gravity force
Background image of page 4
5 Coupling between phases One-way coupling: Fluid phase influences particulate phase via drag and turbulence. Particulate phase has no influence on the gas phase. Two-way coupling: Fluid phase influences particulate phase via drag and turbulence. Particulate phase influences fluid phase via source terms of mass, momentum, and energy. Examples include: • Inert particle heating and cooling. • Droplet evaporation. • Droplet boiling. • Devolatilization. • Surface combustion.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Particle types are inert, droplet and combusting particle. Particle types Particle Type Description Inert inert/heating or cooling Droplet (oil) heating/evaporation/boiling Combusting (coal) heating; evolution of volatiles/swelling; heterogeneous surface reaction
Background image of page 6
7 Temperature particle time Inert heating law Vaporization law Boiling law T b T v T injection Heat and mass transfer to a droplet
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 volatile fraction flashes to vapor Escape Reflect Trap Particle-wall interaction Particle boundary conditions at walls, inlets, and outlets: For particle reflection, a restitution coefficient e is specified: t t t n n n v v e component: Tangential v v e component: Normal , 1 , 2 , 1 , 2 = =
Background image of page 8
9 Particle fates “Escaped” trajectories are those that terminate at a flow boundary for which the “escape” condition is set. “Incomplete” trajectories are those that were terminated when the
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/04/2010 for the course M MM4CFD taught by Professor N/a during the Fall '10 term at Uni. Nottingham.

Page1 / 37

15-dpm - Lecture 15 - Discrete Phase Modeling Applied...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online