KEY STAR TECHNOLOGIES: DISPERSED MULTIPHASE FLOW AND LIQUID FILM MODELLING DAVID GOSMAN EXEC VP TECHNOLOGY, CD-adapco

Transcription

1 KEY STAR TECHNOLOGIES: DISPERSED MULTIPHASE FLOW AND LIQUID FILM MODELLING DAVID GOSMAN EXEC VP TECHNOLOGY, CD-adapco

2 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

3 INDUSTRIAL APPLICATIONS Aerospace Automotive Chemical Process Energy Oil and Gas Manufacturing Process and many more

4 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 swirl atomiser Pressure jet atomiser

5 ATOMISATION MODELLING OPTIONS AVAILABLE range of approaches available in both STAR-CCM+ and STAR-CD: - empirical, including user input - phenomenological/experiment-based - physics-based, transport equations AVAILABLE MODELS User input individual droplets - distribution STAR- CCM+ STA R-CD general Typical Application Liquid core nozzle surface 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

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

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

8 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

9 LAGRANGIAN MODELLING SOME DETAILS Particle and continuum fluid conservation equations Particle momentum Particle location Particle mass dx d dt = u d Particle energy Fluid momentum particles

10 LAGRANGIAN MODELLING SOME DETAILS 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) disperse FEATURES MODELLED STAR- CCM+ STAR -CD Particle material fluid - solid breakup Interphase Drag Turbulent dispersion Breakup Droplet collision, coalescence Interphase heat transfer sensible - latent - radiative collide/coalesce Multicomponent mass transfer miscible - immiscible Boiling, critical point thermodynamics Electrostatic forces Particle combustion (coal) disperse

11 liquid penetration (m) vapor penetration (m) LAGRANGIAN MODELLING VALIDATION EXAMPLE Evaporating Diesel spray simulation P inj = 1300 Bar 0,025 0,020 0,015 0,010 calculation (90%) 0,005 EXP 0,000 0,0000 0,0005 0,0010 0,0015 t(s) liquid penetration 0,060 0,050 0,040 0,030 0,020 calculation (0.1%) 0,010 EXP 0,000 0,0000 0,0005 0,0010 0,0015 t(s) vapour penetration

12 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

13 WALL IMPACT MODELLING SOME DETAILS Models available in both STAR-CCM+ (droplets, solid particles) and STAR-CD (droplets) Strongly experiment-based Regimes and outcomes for droplets:

14 WALL IMPACT MODELLING - OPTIONS Models for droplet and/or solid particle impact in STAR-CCM+ and STAR-CD particle material fluid - solid FEATURE MODELLED droplet impact regime identification - dry, wet wall - user specified STAR- CCM+ STAR -CD 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

15 WALL IMPACT MODELLING VALIDATION EXAMPLE Simulation of spray impingement on cold wall using STAR-CD 2.6ms 4.6ms 6.6ms 8.6ms measured calculated

16 LIQUID FILM MODELLING - OVERVIEW 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.

17 LIQUID FILM MODELLING SOME DETAILS assume film thin, laminar, locally smooth express Eulerian conservation equations in integral form across film thickness δ in wall-normal direction n, δ n φ assume normalised wall-tangential velocities and temperature, concentrations vary quadratically across film result is two-dimensional conservation equations for film thickness δ, mean velocity u mean ; temperature T mean etc as functions of wall-tangential coordinates and time. solve 2D equations by finite-volume method fast, efficient, can accommodate arbitrarily thin films.

18 LIQUID FILM MODELLING SOME DETAILS Modelling options in STAR-CCM+ and STAR-CD Features Modelled Transition from isolated droplet deposition to film STAR - CCM+ STAR -CD 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

19 LIQUID FILM MODELLING VALIDATION EXAMPLES Simulation of air blast atomisation using STAR-CCM+ Liquid film, stripping, Lagrangian droplets Coarse Grid Resolution

20 OIL/GAS APPLICATION PIPELINE EROSION Simulation of undersea pipeline erosion using STAR-CCM+ Multiphase oil-water-sand mixture Lagrangian solid particle, erosion models

21 AUTOMOBILE APPLICATION RAIN MANAGEMENT Simulation of rain impact on automobile exterior Lagrangian droplets, liquid film, stripping

22 AUTOMOBILE APPLICATION CATALYTIC CONVERTOR Simulation of urea injection in automotive catalytic convertor Lagrangian spray, liquid film, boiling

23 MANUFACTURING APPLICATION SPRAY PAINTING Simulation of automobile spray painting process with STAR-CCM+ Lagrangian spray, overset mesh

24 MEDICAL APPLICATION METERED DOSE INHALER Simulation of metered dose inhaler operation with STAR-CCM+ Lagrangian spray, liquid film, evaporation

25 AEROSPACE APPLICATION WING ICING Simulation of aircraft wing icing with STAR-CCM+ Lagrangian spray, liquid film, freezing/melting

26 AEROSPACE APPLICATION ENGINE NACELLE ICING Simulation of aircraft engine icing with STAR-CCM+ Lagrangian spray, liquid film, freezing/melting, mesh morphing

27 SUMMARY 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