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EXPERIMENTAL INVESTIGATION OF BOUNDARY LAYER TURBULENCE IN A WATER FLUME

EXPERIMENTAL INVESTIGATION OF BOUNDARY LAYER TURBULENCE IN A WATER FLUME. Daniel E. Dombroski PI: John P. Crimaldi. Environmental Fluid Mechanics Laboratory, University of Colorado at Boulder. Some Background. pollutants odor signals reproduction. Environmental Fluid Mechanics:

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EXPERIMENTAL INVESTIGATION OF BOUNDARY LAYER TURBULENCE IN A WATER FLUME

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  1. EXPERIMENTAL INVESTIGATION OF BOUNDARY LAYER TURBULENCE IN A WATER FLUME Daniel E. Dombroski PI: John P. Crimaldi Environmental Fluid Mechanics Laboratory, University of Colorado at Boulder

  2. Some Background • pollutants • odor signals • reproduction • Environmental Fluid Mechanics: • - Implications of Turbulence on Natural Systems • Duality of Hydrodynamics and Chemical Signaling • Methodology & Devolopment of Techniques

  3. Projects • Accuracy of Acoustic Doppler Velocimetry (ADV) Measurements in Turbulent Boundary Layer Flows* *Dombroski and Crimaldi, Limnology & Oceanography: Methods, 2007 • Biofouling Phenomena: Growth of communities of organisms on submerged surfaces • 3D Visualization of Plume Dynamics

  4. Accuracy of Acoustic Doppler Velocimetry Acoustic Doppler Velocimeter - Commonly Used Field Instrument - ‘Economical’ ~ $10k - Relatively Low Spatio-Temp Resolution Laser Doppler Velocimeter - Precision Laboratory Instrument - ‘Pricey’ ~ $250k + - High Spatio-Temp Resolution

  5. Spalart DNS (1988) ADV Significantly Underreports Turbulence Statistics

  6. Biofouling

  7. Early Stage Fouling Plate Late Stage Fouling Plate

  8. AlgorithmStatistical analysis of stress lulls in instantaneous record Steps: (1) Calculate stress record,  =u’w’ Divide record into stress ‘lulls’, Li Calculate anchoring probability, Pa: Figure adapted from Crimaldi et al, 2002 where For discrete time intervals Δt, evaluate ψi as: Where ja = # of time steps in ta Nmax = # of samples in longest stress lull where Ni =# of samples in ith stress lull Combining, Dependent on criteria Tcrit & ta

  9. Ship Wake Wind Chop • 50Stress Calculation

  10. Flow Visualization 3D Planar Laser Induced Fluorescence • Scalar: Rhodamine 6G Passive - Moves with and diffuses relative to the flow without effecting the governing physics Conservative - Nonreactive • Plume: Bed-level, low momentum release • Think odor release at river bed

  11. 3D PLIF Schematic

  12. Flow Dynamics

  13. Coherence

  14. Relevant Scales • Experimental Resolution • Image Plane (based on CCD chip) ~ 0.1 mm • Transverse (based on laser beam) ~ 0.25 mm • Kolmogorov - smallest eddies ~ 1 mm (Estimated from dissipative & viscous scaling) • Batchelor - smallest chemical gradients ~ 0.01 mm (Estimated from Kolmogorov scale, Schmidt number)

  15. “Burst – Sweep” Action time

  16. Moving away from the plume centerline…

  17. Scalar Gradients(ie, where’s the mixing?) dC/dx dC/dy dC/dz

  18. Spatial Undersampling Correcting Artifacts

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