Drag Reduction in Ships Using Micro bubbles Technology Abstract: Drag is a mechanical force which is generated with a solid object that is moving through a fluid. There should be movement between the object and the fluid. Drag acts in opposite direction to the direction of motion of the body.
When a body is moving then it experiences a drag force and it usually has two components, frictional drag which is called viscous drag and pressure drag which is called form drag or profile drag.
Frictional drag is generated with friction between the surfaces and the fluid on which it is flowing and it is associated with the developed boundary layers. Pressure drag is generated from the eddying motions which in the fluid with the passage of the body and is associated with the formation of a wake.
To the study drag reduction in ships, Microbubbles Technology is the latest development that reduces almost 20-80%. Microbubbles is a device of drag reduction which reduces skin friction of a solid body floating in water by injecting small bubbles into the turbulent boundary layer which is developing on the solid body. The energy required for injecting bubbles at hull bottom is not small due to large ships which have large water depth by which the bubbles have to be injected. Hence to reduce the amount of injected air microbubbles technology is applied.
The drag of a ship has two components, one is wave-making drag and another one is skin frictional drag.
To generate a drag, the solid body should be in contact with the fluid. If there is no fluid then there is no drag. Drag is produced with the difference in velocity between the fluid and the solid object. When the drag is dominated by viscous drag, then the body is said to be streamlined and when is dominated by pressure drag then the body is bluff. Viscous-drag or pressure-drag depends on the shape of the body.
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