Cai, Xuan

Deutschmann, Olaf

Wörner, Martin

English

KITopen

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association www.kit.edu9th International Conference on Multiphase Flow (ICMF 2016), May 22 to 27, 2016, Firenze, ItalyDirect Numerical Simulations for Interface-resolving of Gas-liquid Flows in Solid Sponge Structure Xuan Cai, Dr. Martin Wörner, Prof. Olaf DeutschmannKarlsruhe Institute of Technology (KIT), Germany2OutlineMotivation of Direct Numerical Simulations (DNS) for interface resolvingPhase field method and phaseFieldFoam in OpenFOAMValidation for droplet or bubble interacting with solid surfaceDNS for interface-resolving of gas-liquid flows in sponge structureSummary & outlooks3MotivationDirect numerical simulation for understanding hydrodynamic interaction of gas-liquid interfacial flows with solid surface Liquid GasSolidMultiphase reactor with structured packingsInternal Structuresponge (i.e. foam)structureGas-liquid Interfacial flow in representative domain of sponge structuredynamics of moving contact linelength scalem µm4MotivationDirect numerical simulation for understanding hydrodynamic interaction of gas-liquid interfacial flows with solid surface Volume fraction equation in VOF:on wallFor sharp-interface method, classical paradox between:• motion of contact line • no-slip boundary condition  Common remedy is to allow for slip at wall by Navier slip BCAnother strategy is to abandon “sharp-interface” and embrace “diffuse-interface” conceptLiquid GasSoliddynamics of moving contact line5Wetting boundary condition for static contact angle θeSingle-field Navier-Stokes equation: Phase field (C ) as phase indictorSmooth transition from -1 to 1 → diffuse interfaceCC = -1C =1tanh2xCxæ öç ÷= ç ÷è øPhase Field MethodPhase field evolution governed by Cahn-Hilliard equation describes motion of contact line!Φ = chemical potential [J/m3]λ = mixing energy [J/m]ε = diffuse interface thickness [m]κ = mobility [m3s/kg]6Close cooperation with Dr. Holger Marschall (TU Darmstadt, Germany)CMethod implementation and verificationVerification by extensive test cases against analytical solutions***  H. Marschall, X. Cai and M. Wörner. Conservative finite volume discretization of the two-phase Navier Stokes Cahn-Hilliard and Allen-Cahn equations on general grids with applications to dynamic wetting, 2016, in preparationPhase field method implemented in OpenFOAM (foam-extend-1.6 & 3.2)A novel OpenFOAM solver phaseFieldFoam* Validation by a series of test case for dynamics of droplet or bubble interacting with solid surfaces, such as …** X. Cai, H. Marschall, M. Wörner and O. Deutschmann, Chem. Eng. Technol. 2015,  38: 1985–19927CExperiment by Zosel 1993Diameter ≈ 3 mmPIB solution µ = 25 pa∙ssmooth PTFE surface (θe = 58º)time3D phase-field simulation withadaptive mesh refinement near interfaceDroplet base radius (r ) over timeReference: X. Cai, H. Marschall, M. Wörner and O. Deutschmann, Chem. Eng. Technol. 2015,  38: 1985–1992Validation on droplet wetting on flat surface 8CExperiment by Jansen et al. 2013Glycerin droplet volume = 3 µLAlternating stripes made of:Reference: X. Cai, H. Marschall, M. Wörner and O. Deutschmann, Chem. Eng. Technol. 2015,  38: 1985–1992Droplet wetting on chemically-patterned surface SiO2, θe = 40°PFDTS, θe = 106°timeExperimentJansen et al. 2013Lattice-Boltzmann SimulationJansen et al. 2013Phase-field SimulationCai et al. 20159Validation on cylinder-induced bubble breakupReference: X. Cai, M. Wörner, H. Marschall and O. Deutschmann, Catalysis Today, 2016, in pressExperiment Segers 2015(Prof. Kuipers, Prof. Deen,TU Eindhoven)Phase-fieldSimulationCai et al. 2016• Diameter of cylinder = 3.1 mm• Diameter of bubble = 9.1 mm10OutlineMotivation of Direct Numerical Simulations (DNS) for interface resolvingPhase field method and phaseFieldFoam in OpenFOAMValidation for droplet or bubble interacting with solid surfaceDNS for interface-resolving of gas-liquid flows in sponge structureSummary & outlooks11θe = 45°Interface-resolving for Two-phase Flow in Sponge Source: Wallenstein et al. 2015solidliquidRepresentative Elementary Volume (REV)µCT & Reconstruction S. Meinicke, KIT-TVT STL geometry for CFDTotal Sponge structureHeight: 25 – 100 mmDiameter: 100 mmIndividual liquid jetsApprox. 1 – 10 mmLocal gas-liquid interfaceApprox. 0.1 – 1 mmDisparity of length scale up to 102 or 103! 12Computational mesh for sponge geometryOpenFOAM’s mesh generator snappyHexMesh3D view 2D cross-cutting view13Validation for single-phase gas flow Apply the solver for gas flow through sponge structureCompare our simulation results with experiment* and simpleFoam simulation** Gas flow shown by velocity vector (yellow)in a Al2O3 sponge, 80% porosity, 20 ppi*   Dietrich et al. Chem. Eng. Sci. 64 (16), 3633-3640. 2009**  Meinicke et al., 11th Int. Conf. on CFD in the Minerals & Proc. Industries 2015• U0: superficial gas velocity• ∆p /∆x : pressure drop per unit length pressure drop VS. gas velocity14Representative Elementary Volume → difficult to get inlet liquid distribution from exp.Mirroring geometry + periodic boundary conditionsInterface-resolving for Two-phase Flow in Sponge SiSiC foam, 20 ppi, 85% porosity15Representative Elementary Volume → difficult to get inlet liquid distribution from exp.Mirroring geometry + periodic boundary conditionsInterface-resolving for Two-phase Flow in Sponge SiSiC foam, 20 ppi, 85% porosity16Interface-resolving for Two-phase Flow in Sponge SiSiC foam, 20 ppi, 85% porosityß = 0.2∆p/∆x = 200 Pa/mConventionally (in experiment): inlet flow rate → pressure dropIn current periodic domain:pressure drop → inlet/domain flow rate Input to DNS: liquid saturation ß (Vliquid) / (Vliquid + Vgas)Pressure drop ∆p/∆x17Interface-resolving for Two-phase Flow in Sponge Liquid saturation ß = 0.2 and ∆p/∆x = 200 Pa/mEquilibrium contact angle = 90°18θe = 40°θe = 80°Effect of equilibrium contact angle θe (i.e. solid surface wettability) Interface-resolving for Two-phase Flow in Sponge 19Effect of contact angle Interface-resolving for Two-phase Flow in Sponge Gas-liquid interfacial area Ai vs. contact angle θefor different liquid saturation ßEffect of gas-liquid surface tension Gas-liquid interfacial area Ai vs. contact angle θefor different liquid saturation ßcontact angle ↓ gas-liquid surface tension ↓  gas-liquid interfacial area ↑ Interfacial mass transfer ↑ 20Summary and OutlookPhase Field Method and phaseFieldFoam in OpenFOAMValidation for droplet or bubble interacting with solid surfaceDNS for interface-resolving of gas-liquid flows in sponge structureProviding clear evidence that interfacial area can be increased by tuning surface wettability or interfacial tension Outlook for future work:Further investigations on other initialization strategy Derive closure relation for Euler-Euler modeling and simulationExperimental study on local interface distribution is highly needed21AcknowledgementPhD study funded by Germany Helmholtz Energy Alliance “Energy-efficient chemical multiphase processes”Partners:Dr. H. Marschall (CSI, TU Darmstadt, Germany)Dr. B. Dietrich, S. Meinicke (KIT-TVT, Karlsruhe, Germany)Prof. B. Frohnapfel, V. Fink (KIT-ISTM, Karlsruhe, Germany)Prof. P. Yue (Virginia Tech, USA)Prof. H. Alla(USTO, Oran, Algeria)

Direct Numerical Simulations for Interface-resolving of Gas-liquid Flows in Solid Sponge Structure

https://publikationen.bibliothek.kit.edu/1000055720/151031169

Direct Numerical Simulations for Interface-resolving of Gas-liquid Flows in Solid Sponge Structure

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