key star technologies: dispersed multiphase flow
TRANSCRIPT
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KEY STAR TECHNOLOGIES:
DISPERSED MULTIPHASE FLOW
AND LIQUID FILM MODELLING DAVID GOSMAN
EXEC VP TECHNOLOGY, CD-ADAPCO
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Introduction
Atomisation modelling
Lagrangian dispersed flow modelling and validation
Wall impact modelling and validation
Liquid film modelling and validation
Further industrial application examples
Closure
CONTENTS
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INTRODUCTION
KEY METHODOLOGIES AVAILABLE IN STAR-CCM+ AND STAR-CD
1. Lagrangian modelling of dispersed multiphase flow of droplets
or solid particles.
2. Modelling of droplet or solid particle impact on walls.
3. Modelling of liquid film formation, dynamics, heat/mass transfer
in all cases with full interaction with continuous phase.
• STAR-CCM+ generally applicable (e.g. aeronautical, chemical process,
oil/gas, medical, etc)
• STAR-CD specifically targeted at reciprocating internal combustion
engine (ICE) modelling
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Aerospace (gas turbine combustor, blade erosion, icing….)
Automotive (engine combustion, exhaust aftertreatment, soiling….)
Chemical Process (spray driers, gas/liquid contactors, evaporators,
reactors…..)
Energy (coal furnaces, steam turbines, nuclear reactors……)
Oil and Gas (multiphase pipeline flow, pipeline erosion,
separators….)
Manufacturing Process (spray painting, coating, quenching…..)
… and many more
INDUSTRIAL APPLICATIONS
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ATOMISATION MODELLING - OVERVIEW
• modelling of droplet formation by breakup of liquid stream
• provides initial conditions for Lagrangian spray simulation
• built-in models for several atomiser types
• may also include internal flow in atomiser
pressure jet atomiser
pressure swirl atomiser
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range of approaches available in both STAR-CCM+ and STAR-CD:
- empirical, including user input
- phenomenological/experiment-based
- physics-based, transport equations
ATOMISATION MODELLING – OPTIONS AVAILABLE
AVAILABLE MODELS STAR-
CCM+
STA
R-CD
Typical
Application
User input – individual droplets
- distribution
✓
✓
✓
✓
general
Huh model (pressure jet) ✓ ICE
Reitz-Diwaker (pressure jet) ✓ ✓ ICE
MPI model (pressure jet) ✓ ICE
LISA model (conical spray) ✓
gas turbine
ELSA model (nozzle flow and atomisation) ✓
ICE, general
LES+VOF (high-resolution nozzle flow and
atomisation)
✓
✓
general
Liquid core
surface
nozzle
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Simulation of spray atomisation by pressure jet nozzle with STAR-CD
Includes internal nozzle flow
High-resolution VOF+LES (+cavitation)
ATOMISATION MODELLING - EXAMPLES
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LAGRANGIAN DISPERSED FLOW MODELLING – OVERVIEW
multiphase modelling of dynamics, heating, evaporation/condensation of
droplets or solid particles.
solve Lagrangian conservation equations for statistically representative
particles, along with Eulerian conservation equations for fluid phase
phase equations fully-coupled
urea injection in SCR system
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LAGRANGIAN MODELLING – SOME DETAILS
Particle momentum
Particle mass
Particle energy
Fluid momentum
Particle location
Particle and continuum fluid conservation equations
particles
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built-in models in STAR-CCM+/STAR-CD for key phenomena, including
- droplet turbulent dispersion, breakup, collision and coalescence
- interphase heat/mass transfer
- chemical reaction (coal combustion)
LAGRANGIAN MODELLING – SOME DETAILS
FEATURES MODELLED STAR-
CCM+
STAR
-CD
Particle material – fluid
- solid
✓
✓
✓
Interphase Drag ✓ ✓
Turbulent dispersion ✓ ✓
Breakup ✓ ✓
Droplet collision, coalescence ✓ ✓
Interphase heat transfer – sensible
- latent
- radiative
✓
✓
✓
✓
✓
Multicomponent mass transfer – miscible
- immiscible
✓
✓
✓
Boiling, critical point thermodynamics ✓ ✓
Electrostatic forces ✓
Particle combustion (coal) ✓
disperse
disperse
breakup
collide/coalesce
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LAGRANGIAN MODELLING – VALIDATION EXAMPLE
0,000
0,005
0,010
0,015
0,020
0,025
0,0000 0,0005 0,0010 0,0015
t(s)
liqu
id p
en
etr
atio
n (
m)
calculation (90%)
EXP
0,000
0,010
0,020
0,030
0,040
0,050
0,060
0,0000 0,0005 0,0010 0,0015
t(s)
va
po
r p
en
etr
ation
(m
)
calculation (0.1%)
EXP
Pinj = 1300 Bar
liquid penetration vapour penetration
Evaporating Diesel spray simulation
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WALL IMPACT MODELLING - OVERVIEW
prediction of regimes and outcomes of droplet or solid particle impact on
wall.
regime can depend on: droplet dynamics; surface temperature,
roughness, material……
outcome can include deposition, secondary breakup…….
solid particle impact can lead to wall erosion
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Models available in both STAR-CCM+ (droplets, solid particles) and STAR-CD (droplets)
Strongly experiment-based
Regimes and outcomes for droplets:
WALL IMPACT MODELLING – SOME DETAILS
Senda et al model
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Models for droplet and/or solid particle impact in STAR-CCM+ and STAR-CD
WALL IMPACT MODELLING - OPTIONS
FEATURE MODELLED STAR-
CCM+
STAR
-CD
particle material – fluid
- solid
✓
✓
✓
droplet impact regime identification
- dry, wet wall
- user specified
✓
✓
✓
✓
droplet impact outcome
- secondary droplet size, velocity
- liquid deposition rate
✓
✓
✓
✓
droplet-wall heat transfer ✓
droplet multicomponent evaporation and boiling
- finite rate
- instantaneous
✓
✓
user-specified particle stick/rebound/escape ✓ ✓
wall erosion rate ✓
Ice accretion rate ✓
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Simulation of spray impingement on cold wall using STAR-CD
WALL IMPACT MODELLING – VALIDATION EXAMPLE
2.6ms
6.6ms
4.6ms
8.6ms
measured calculated
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prediction of dynamics, heat/mass transfer, melting/solidification of thin liquid film on wall
film may be result of spray impact, condensation, melting, inlet boundary……..
interaction with adjacent fluid phase via interface boundary conditions and special deposition and stripping models.
modelled by solving Eulerian conservation equations in special way, avoiding need for fine mesh across film.
LIQUID FILM MODELLING - OVERVIEW
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• assume film thin, laminar, locally smooth
• express Eulerian conservation equations in integral form across film thickness δ
in wall-normal direction n,
• assume normalised wall-tangential velocities and
temperature, concentrations vary quadratically across film
• result is two-dimensional conservation equations for film thickness δ, mean
velocity umean; temperature Tmean etc as functions of wall-tangential coordinates
and time.
• solve 2D equations by finite-volume method – fast, efficient, can accommodate
arbitrarily thin films.
LIQUID FILM MODELLING – SOME DETAILS
δ n φ
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Modelling options in STAR-CCM+ and STAR-CD
LIQUID FILM MODELLING – SOME DETAILS
Features Modelled STAR
-
CCM+
STAR
-CD
Transition from isolated droplet deposition
to film
✓ ✓
interphase momentum transfer via
- interfacial drag
- interfacial deposition/stripping
✓
✓
✓
✓
internal and interphase energy transfer
- conduction/convection/boiling
- evaporation/condensation
- deposition/stripping
✓
✓
✓
✓
✓
✓
internal and interphase mass transfer
- multicomponent
- evaporation/condensation
- deposition/stripping
✓
✓
✓
✓
✓
✓
surface stripping ✓ ✓
edge separation ✓ ✓
solid particle ingestion ✓
solidification/melting ✓
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Simulation of air blast atomisation using STAR-CCM+
Lagrangian, liquid film, stripping
LIQUID FILM MODELLING – VALIDATION EXAMPLES
Coarse Grid Resolution
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OIL/GAS APPLICATION – PIPELINE EROSION
Simulation of undersea pipeline erosion using STAR-CCM+
Multiphase oil-water-sand mixture
Lagrangian solid particle, erosion models
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AUTOMOBILE APPLICATION – RAIN MANAGEMENT
Simulation of rain impact on automobile exterior
Lagrangian droplets, liquid film, stripping
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AUTOMOBILE APPLICATION – CATALYTIC CONVERTOR
Simulation of urea injection in automotive catalytic convertor
Lagrangian spray, liquid film with boiling
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Simulation of automobile spray painting process with STAR-CCM+
Lagrangian spray, overset mesh
MANUFACTURING APPLICATION – SPRAY PAINTING
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MEDICAL APPLICATION – METERED DOSE INHALER
Simulation of metered dose inhaler operation with STAR-CCM+
Lagrangian spray, liquid film, evaporation
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AEROSPACE APPLICATION – WING ICING
Simulation of aircraft wing icing with STAR-CCM+
Lagrangian spray, ice accretion, liquid film, freezing/melting
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AEROSPACE APPLICATION – ENGINE NACELLE ICING
Simulation of aircraft engine icing with STAR-CCM+
Lagrangian spray, ice accretion, mesh morphing
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Powerful, unique methodologies in STAR-CCM+ for simulating
dispersed multiphase and liquid film flows, separately or in
combination
Extensive and continuing validation and refinement
Many industrial applications already – but potential for much more
Further extensions envisaged, e.g.:
- combined Lagrangian ⇔VOF
- combined Liquid Film ⇔ VOF
- fast conjugate heat transfer + Liquid Film
SUMMARY
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CLOSURE