2010. 11.10 Prof. Bum Sang Yoon()

KAIST

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IntroductionCDS NecessitySOTOP OverviewSOTOP Result

?? ?1964~69 30~120 1970~74 ?1975~76 1982~85TokyoUniv. of Tokyo 1977~80 1986~881991~92DC(NSRDC) , 1997~98 , 1999~01 2003~04DavisUC Davis 2005~

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IntroductionCDS NecessitySOTOP OverviewSOTOP Result

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1975~1985 Marine Hydrodynamics : 10-1~102 m wave~floating body interaction

1985~1995 CFD, Viscous flow, Turbulence : 10-2~10 m

1995~2005 CFD, Environmental flow : 102~105 m

2005~ Superhydrophobicity Friction drag reduction : 10-9~102 m - Multi-scale fluid mechanics -

IntroductionCDS NecessitySOTOP OverviewSOTOP Result

*** 20- -(Price Competitiveness)(Productivity)

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IntroductionCDS NecessitySOTOP OverviewSOTOP Result

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*Marine Tech Summit Dalian (2010.10.23)

flowForm drag (10~40%) : minimizedFriction drag (60~90%) : Gods region challenge ! body- In case of slender body (ex. Ship) -

*Super-hydrophobicitySuperhydrophobicity(Lotus leaf)

** ?*- Air entrapped in between water and solid surface ?-

**Hydrophobicity-2*Hydrophilic surfacecontact angle < 90Hydrophobic surface : contact angle > 90Superhydrophobic surface : contact angle > 150

*Contact Angle (POSTECH)NAOE, University of UlsanS.E.M. images of dual-scale artificial Super-Hydrophobic surface.Contact angle of a droplet on Super-Hydrophobic surface.

*Experimental SetupNAOE, University of UlsanDimensions of the models and other informationDimensions of the model The velocity of the flow from 0.075 m/s to 0.503 m/s(Reynolds number from 54,300 to 364,500)

The fore part is used to eliminate the form resistance of the flow.

3 kinds of model are usedSmooth aluminum surfaceHydrophilic surfaceSuper-Hydrophobic surface

*Air-layer Observed (1)NAOE, University of UlsanSome images of the flow under Super-Hydrophobic surface* An air layer is observed.* The air layer shrinks as the velocity of the flow increases.qc = 48.6o

*Drag ReductionNAOE, University of UlsanThe friction drags acquired from the experiment

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