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Wednesday, 5 December 2018

DRAG AND LIFT COEFFICIENT IN FLUID MECHANICS

We were discussing the basics of Boundary layer theorylaminar boundary layerturbulent boundary layerboundary layer thickness, displacement thickness and momentum thicknessenergy thickness and drag force &lift force, in the subject of fluid mechanics, in our recent posts. 

After understanding the fundamentals of drag and lift force, we will see now drag and lift coefficient, with the help of this post. 

We have already discussed that drag and lift forces will be dependent over the various factors such as density of the fluid, upstream velocity, size, shape and orientation of the body. It will be quite easy to work with appropriate dimensionless numbers. 

These dimensionless numbers will represent the drag and lift characteristics of the body and these dimensionless numbers will be termed as drag coefficient and lift coefficient. 

Drag coefficient

Drag coefficient is basically defined as the ratio of drag force to the dynamic pressure. Drag coefficient could be determined with the help of following equation as mentioned here. Drag coefficient will be represented by CD

Lift coefficient

Lift coefficient is basically defined as the ratio of lift force to the dynamic pressure. Lift coefficient could be determined with the help of following equation as mentioned here. Lift coefficient will be represented by CL
Where, 
½ ρV2 = Dynamic pressure 
CD = Co-efficient of drag 
CL = Co-efficient of lift 
A = Area of the body which is projected area of the body perpendicular to the direction of flow 
FR = Resultant force on the body 
ρ = Density of the fluid 
V = Flow velocity relative to the object 

Further we will go ahead to start a new topic i.e.continuity equation for compressible fluid flow, in the subject of fluid mechanics, with the help of 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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