Watching bubbles rise in a tank Dissecting gas transport in natural waters

1. Niko Bigalke (GEOMAR) • Gregor Rehder (IOW) • Gieselher Gust (TUHH) Andreas Meyer (TUHH) Bubble workshop GEOMAR, Kiel, Germany, 8 & 9 January 2013 Watchingbubblesrise in a tank Dissecting gas transport in naturalwaters

2. Why tank experiments? • Validity • (Cost) • Easy accessibility • Versatility • Productivity • Controllability Pro: Con: Fingerprint individual parametersorproperties, thataredifficulttoassess in the real world.

3. Hydrate stability in theocean Bigalke et al., 2010

4. Interfacialhydrate - effects immobile surface mobile surface after Leifer (www.bubbleology.com)

5. Interfacialhydrate - effects immobile surface mobile surface after Leifer (www.bubbleology.com)

6. Interfacialhydrate - effects • Flowfieldaroundbubble • Motioncharacteristics (e.g. shape/pathoscillations) • Risevelocity • Shape • Gas exchangekinetics • Bubble/dropletshape • Gasexchangekinetics immobile surface mobile surface after Leifer (www.bubbleology.com)

7. Interfacialhydrate - effects • Flowfieldaroundbubble • Motioncharacteristics (e.g. shape/pathoscillations) • Risevelocity • Shape • Gas exchangekinetics • Bubble/dropletshape • Gasexchangekinetics immobile surface mobile surface after Leifer (www.bubbleology.com) • Bigalke, Rehder, Gust; Envrion. Sci. Technol. 42(14), 5241-5246, 2008 • Bigalke, Enstad, Rehder, Alendal; Deep-Sea Res. I 57(9), 1102-1110, 2010

8. P, Tcoordinatesalonggivenhydrotherm within CO2-HSF rCO2 < rSW uTexpectedtodecreasewithadaptedinjectiondepth uT CO2droplets / CH4bubbles Bigalke et al., 2008

9. DL 2 - PressureFacility • h = 140 cm • ID = 30 cm • V = 99 L • Pmax = 55 MPa • 0 °C > T > RT Housed in modified, thermostable, seaworthy, 20-foot ISO container (TUHH, G. Gust) Actuatorpanelwith Lab-View controlledpneumaticpumps

10. DL 2 - PressureFacility • Quick releasemechanism • 2 opticalwindows(onepivotable lock) • 2 16-pole SubConmicroplugs • Sampling/fluid injectionports H. Steffen Lid: Bottom: • 24-pole seaconconnector • 5 mechanicalportsfor sample handling

11. Producing & imagingbubbles streamingto HDD Top camera Piston Diffusingscreen CO2 Pump • 8 bit, ¼“ progressivescan CCD • 640 x 480 Px • 60 fps • 1:2.8, 80 mm Nikon lens • 30 Px/mm CO2container Injectornozzle Recirculation pump PMMA tube

12. Results – CO2droplets f c 17.5 MPa, 275.1 K 9.9 MPa, 276.1 K a e b g 8.3 MPa, 276.7 K 14.7 MPa, 275.6 K a d 20.2 MPa, 275.0 K 5.7 MPa, 277.9 K g 11.9 MPa, 275.9 K Chen et al., 2003

13. Results – CO2droplets f c 17.5 MPa, 275.1 K 9.9 MPa, 276.1 K e b 8.3 MPa, 276.7 K 14.7 MPa, 275.6 K a d 20.2 MPa, 275.0 K 5.7 MPa, 277.9 K g 11.9 MPa, 275.9 K Chen et al., 2003

14. Results – CO2droplets a c b Dr = 0.048 g/cm3 a b c b Dr= 0.060 g/cm3 a c • Bimodalvelocitydistributionwithin HSF • High velocitydropletswithin HSF anddroplets outside HSF equally fast • Riseratesaberrantfrom norm within HSF due tomissinghydrateskins Dr= 0.076 g/cm3

15. Results – CO2droplets a c b Dr = 0.048 g/cm3 a b c b Dr= 0.060 g/cm3 a • Dropletsdeformmoreeasilywithouthydratecoating but • Bothtypesspherical @ re < 2 mm • uTsimilar @ re < 2 mm • Thissizeregime: surface rigid even w/o hydrateskin c Dr= 0.076 g/cm3

16. Results – CH4bubbles uT

17. sphericity Results – CH4bubbles 4.0 °C uT

18. Summary • Hydrate skinformationdeepwithininside HSF isthenorm andisidentifiedbyhighersphericities in bubblesanddroplets • The numberofexceptionsincreaseswithproximitytothehydratephaseboundary • Hydrate skin formation strongly affects rise velocities  Droplets without hydrate interfaces rise at velocities of <50% higher than their equally buoyant counterparts with hydrate

19. ThankYou!