MULTIPHASE TURBULENT FLOW

Numercal methodsin multphase flowsaatay GventrkSpring - 2015OverviewMultiphase Flows -Definition -Physical Background -Cohesive and Adhesive Forces -Mathematical ModellingNumerical Methods - Marker and Cell Method (MAC) - Level Set Method (LSM) - Volume of Fluid Method (VOF) - Arbitrary Lagrangian Eulerian Approach (ALE)Multiphase FlowsDefinitionMultiphase flow is a flow in which two or more phases of matter are interacting dynamically.Three-phase flow in a pipeASCOMP GmbH, TransAT

Solid liquid gas liquid liquid liquid / immiscible3Physical Backgroundwww.quest.nasa.govSurface tensionSurface tension Cohesive forces between liquid moleculesInternal pressure and minimal area Attraction of molecules on surface

Droplet on water surfaceMinuteLabFloating thin film of air. Diffuses quickly.Drop collapse eventually.4

Only cohesive forces-5

Excess capillary pressure inside the droplet accelaretes the some fraction of the drop, splits to the parts6

Excess capillary pressure inside the droplet accelaretes the some fraction of the drop, splits to the parts7Cohesive and Adhesive Forceswww.quest.nasa.govContact angleCohesive forces Molecules of same substance, resist to separationAdhesive forces Unlike moleculesContact angle Cohesion / Adhesion

Water droplet impinged on a teflon surfaceSandeep GandeAdhesion ar basarsa angle nearly zero and droplet spreads think tangential.8Mathematical ModellingContinuity equationMomentum equationThe rate of strain tensorCurvatureInterfaceInertia/Pressure gradient/Viscous forces/Surface tension/Gravitational force. CURVATUREEEEE9Numerical MethodsMarker and Cell Method (MAC, Harlow and Welch, 1965)Interface tracking Marker particlesSurface cell A cell with marker particle adjacent to an empty cell

Velocity directions10Marker and Cell Method (continued)Boundary Conditions -Free surface Velocity 1 side vacuumNo-slip BC2 sides vacuum

Vacuum side opposite to the fluid side is set to the fluid side velocity. Moves freely with the effects of gravity.11Level Set Method (LSM, Osher and Sethian, 1988)AirInterfaceWaterRe-initialize

Kapal contour mu olmak zorunda dalga falan nasl oluyor. 12Level Set Method (continued)Unit normal vectorMean curvatureDensityMomentum equationViscosityCurvatureContinuity equationSmooth the discontinuity by heaviside function.13Volume of Fluid Method (VOF, Hirt and Nichols, 1981)Fraction function - 0 C 1

Volume of Fluid Method (continued)Interface tracking

FluxInterface normal vectorDonor Acceptor? Ular vler grid noktalarnda deil de face ortalarnda deil mi? Hangi dorultu, giriyor mu kyor mu?15Volume of Fluid Method (continued)DensitySurface tension forceMomentum equationViscosityFixed grid!!! Burada rho iin smooth bir gei yaplmyor mu?16Arbitrary Lagrangian-Eulerian Approach (ALE)Mesh Follows the interface, unstructuredContinuity equationMomentum equationGeometric conservation law (GCL)Geometric conservation lawGeometric conservation law nedir consistency criteria-moving mesh-change in volume17eunisonALE simulation of the free surface due to the movement of a submerged cylinder

References - ahin M., Istanbul Technical University, Aeronautical Eng. Department, Multiphase Flows and Industrial Implications, Jan. 2011

QUESTIONS?Thanks for your attention20