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Wednesday, 14 February 2018

WHAT IS CENTRE OF BUOYANCY?

We were discussing the basic definition and derivation of total pressurecentre of pressure and buoyancy or buoyancy force in our previous posts.

Today we will see here the basic concept of centre of buoyancy with the help of this post. Further, we will see the concept of Metacentre and Metacentric height in our next post.

Centre of buoyancy

As we know that when a body is immersed in fluid, an upward force is exerted by the fluid on the body. This force will be equal to the weight of the fluid displaced by the body and this force will be termed as force of buoyancy or buoyancy.

Buoyancy force will act through the centre of gravity of the displaced fluid and that point i.e. centre of gravity of the displaced fluid will be termed as centre of buoyancy.

Therefore we can define the term centre of buoyancy as the point through which the force of buoyancy is supposed to act.

Centre of buoyancy = Centre of gravity of the displaced fluid = Centre of gravity of the portion of the body immersed in the liquid

Let us explain the term centre of buoyancy

Let us consider one vessel as displayed here in following figure. Weight of vessel will be distributed throughout the length of vessel and will act downward over the entire structure of vessel.
But, what do we consider?

We consider that complete weight of the vessel will act downward vertically through one point and that point will be termed as the centre of gravity of that vessel.

In similar way, buoyancy force will be supposed to act vertically in upward direction through a single point and that point will be termed as centre of buoyancy.
We will discuss another term i.e. Meta-centre and Meta-centric height in our next post.

Do you have any suggestions? Please write in comment box.

Reference:

Fluid mechanics, By R. K. Bansal
Image Courtesy: Google

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