KEY STAR TECHNOLOGIES: DISPERSED MULTIPHASE FLOW AND LIQUID FILM - - PowerPoint PPT Presentation

KEY STAR TECHNOLOGIES: DISPERSED MULTIPHASE FLOW AND LIQUID FILM MODELLING

DAVID GOSMAN EXEC VP TECHNOLOGY, CD-adapco

INTRODUCTION

KEY METHODOLOGIES AVAILABLE IN STAR-CCM+ AND STAR-CD

• 1. Lagrangian modelling of dispersed multiphase flow of droplets
• r 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,
• il/gas, medical, etc)
• STAR-CD specifically targeted at reciprocating internal combustion

engine (ICE) modelling

Aerospace Automotive Chemical Process Energy Oil and Gas Manufacturing Process … and many more

INDUSTRIAL APPLICATIONS

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

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/or atomisation) ✓ ICE, general LES/VOF (high-resolution nozzle flow and/or atomisation) ✓ ✓ general

Liquid core surface nozzle

Simulation of spray atomisation by pressure jet nozzle with STAR-CCM+ Includes flow within nozzle High-resolution VOF/LES, including cavitation

ATOMISATION MODELLING - EXAMPLES

Simulation of spray atomisation by pressure jet nozzle with STAR-CCM+ High-resolution VOF/LES, including internal nozzle flow and cavitation

ATOMISATION MODELLING - EXAMPLES

LAGRANGIAN DISPERSED FLOW MODELLING – OVERVIEW

multiphase modelling of dynamics, heating, evaporation/condensation

• f droplets or solid particles.

solve Lagrangian conservation equations for statistically representative particles, along with Eulerian conservation equations for fluid phase phase equations fully-coupled

LAGRANGIAN MODELLING – SOME DETAILS

Particle momentum Particle mass Particle energy Fluid momentum

dxd dt = ud

Particle location

Particle and continuum fluid conservation equations

particles

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

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) liquid penetration (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) vapor penetration (m) calculation (0.1%) EXP

Pinj = 1300 Bar

liquid penetration vapour penetration

Evaporating Diesel spray simulation

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……

• utcome can include deposition, secondary breakup…….

solid particle impact can lead to wall erosion

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

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- finite rate

• instantaneous

✓ ✓ user-specified particle stick/rebound/escape ✓ wall erosion rate ✓ Ice accretion rate ✓

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

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

• 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

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

✓ ✓ ✓ ✓ ✓ ✓ stripping removal ✓ ✓ edge separation removal ✓ ✓ solid particle ingestion ✓ solidification/melting ✓

Simulation of air blast atomisation using STAR-CCM+ Liquid film, stripping, Lagrangian droplets

LIQUID FILM MODELLING – VALIDATION EXAMPLES

Coarse Grid Resolution

OIL/GAS APPLICATION – PIPELINE EROSION

Simulation of undersea pipeline erosion using STAR-CCM+ Multiphase oil-water-sand mixture Lagrangian solid particle, erosion models

AUTOMOBILE APPLICATION – RAIN MANAGEMENT

Simulation of rain impact on automobile exterior Lagrangian droplets, liquid film, stripping

AUTOMOBILE APPLICATION – CATALYTIC CONVERTOR

Simulation of urea injection in automotive catalytic convertor Lagrangian spray, liquid film, boiling

Simulation of automobile spray painting process with STAR-CCM+ Lagrangian spray, overset mesh

MANUFACTURING APPLICATION – SPRAY PAINTING

MEDICAL APPLICATION – METERED DOSE INHALER

Simulation of metered dose inhaler operation with STAR-CCM+ Lagrangian spray, liquid film, evaporation

AEROSPACE APPLICATION – WING ICING

Simulation of aircraft wing icing with STAR-CCM+ Lagrangian spray, liquid film, freezing/melting

AEROSPACE APPLICATION – ENGINE NACELLE ICING

Simulation of aircraft engine icing with STAR-CCM+ Lagrangian spray, liquid film, freezing/melting, mesh morphing

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

SUMMARY