14-01-2011, 08:41 PM
MICROBUBBLE TECHNOLOGY
Presented by
PRASANTH C
NO: 39
S 7 MECHANICAL
[attachment=8235]Presented by
PRASANTH C
NO: 39
S 7 MECHANICAL
Introduction
Two types of Drag – Friction and Pressure Drag
Friction Drag due to friction
Pressure Drag due to Eddying motions
Stream line body –Viscous Drag
Bluff body – Pressure Drag
hy Microbubbles
Mechanisms
Local void ratio
Injection point
Boundary layer thickness
Methods for bubble generation
Venturi tube type
Tangential water jet
Foaming of dissolved air
Pros and Cons
large reduction in skin friction up to 80%
No pollutions
Can apply any surface orientation
Affected less by roll and pitch
large amount of air (order of 1000cubic metre per min)
Applications
Power saving in VLCC
Pipelines
Conclusion
small bubbles possibly decrease the overall efficiency of the microbubble drag reduction through dispersion
The understanding of the mechanism of turbulence intensity reduction by microbubbles is the key for break-through.
