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Experiments on near-interface flow phenomena

CARPET 5:. Experiments on near-interface flow phenomena. María Fernandino. CARPET Seminar 2003 Computational Fluid Dynamics Applied to Reactor Process Technology. Objectives. Study turbulence characteristics near the interface of stratified air-water channel flow.

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Experiments on near-interface flow phenomena

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  1. CARPET 5: Experiments on near-interface flow phenomena María Fernandino CARPET Seminar 2003Computational Fluid Dynamics Applied to Reactor Process Technology

  2. Objectives Study turbulence characteristics near the interface of stratified air-water channel flow • mean velocities: applicability of log-law • vertical and horizontal turbulent fluctuations • Reynolds stresses • interfacial shear stress • Prediction for slip velocities • Supply wall laws for computational treatment

  3. test section Experiments (1) • Laser Doppler Velocimetry (LDV) 2D measurements in channel cross section T P P P P AIR WATER tank pump

  4. DP U+ y+ Experiments (1) viscous sublayer buffer zone ??? log region outer region

  5. U+ DP Interface region?? (1) Wall region y+ Experiments (1) Velocity profile regions:

  6. U+ DP y+ Experiments (2) (2) Why from the wall and not from interface?? corrections From the wall Possible reasons: • wall region & interface region  superposed • starting from interface: need for interfacial shear!! (scale) • different velocity profile (no viscous sublayer, etc…)

  7. ~2mm U+ DP h y+ Experiments (3) (3) Interfacial shear?? From measurements (4) Where is the interface?? Linear extrapolation to the interface (5) Is the same profile valid??

  8. Mean Velocities

  9. Fluctuations

  10. Reynolds Stresses

  11. Experiments: Summary Ready stages Next stages - PC - new acquisition card - 1 new DP-Cell - DP-Cells installed - flow meters installed Calibration of DP-Cells Interface tracking?? Learn to use laser Interface region?? (1) Wall region (3) Interfacial shear?? (4) Where is the interface?? (5) Is the same profile valid??

  12. Numerical Simulation To compare results with experiments • Method: DNS, LES Reynolds stress model Lattice Boltzmann no empirical information!!  easy to programme  intrinsically parallelizable  turbulence SGS model easy to introduce

  13. Lattice Boltzmann Method Lattice Gas Automata (LGA) Boltzmann Equation (BE) Lattice Boltzmann Equation (LBE) LBGK Equation move collide

  14. in-state out-state Lattice Boltzmann Method Hydrodynamic variables: Mass: Momentum: Boundary Conditions: in-state in-state in-state out-state out-state out-state No-slip in-state out-state Free slip

  15. Lattice Boltzmann Method Flow between parallel plates

  16. Lattice Boltzmann Method Following steps: • flow between parallel plates + turbulence model Check turbulence characteristics (fluctuations, etc) • open channel with straight interface • how to introduce waves

  17. Done up to now… • Literature survey (experimental - LBM) • Courses: (2002) - Experimental methods in process engineering - Multiphase flow modelling - Computational heat and fluid flow - Introduction to measurement techniques (Von Karman Inst.) (2003) - Viscous flow and turbulence - Advance computational fluid dynamics - Scientific writing - Turbulence phenomena in open-channel flows (self-study)

  18. Done up to now… • Experimental facility ready • Lattice Boltzmann Method - study of theory - first simple cases simulation (laminar + turbulent 2D flow)

  19. Next • experimental measurements Mean velocity profile Applicability of log-law Turbulent fluctuations – Reynolds stresses Interfacial shear • numerical simulations Flow between parallel plates – laminar Flow between parallel plates – turbulent Moving wall / free surface (straight surface) Moving surface (waves) Gas + liquid flow

  20. CARPET 5: Experiments on near-interface flow phenomena María Fernandino CARPET Seminar 2003Computational Fluid Dynamics Applied to Reactor Process Technology

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