Saturday, January 2, 2016

Velocity potential function and stream function

What is potential function in fluid mechanics? 

It's a scalar function of space and time. Its negative partial derivative with respect to any direction will give the fluid velocity in that direction. 
Note that if velocity potential function exists, then the flow will be irrotational and if it satisfies laplace equation, then it represents a possible case of steady - incompressible - irrotational fluid flow. 

What is stream function in fluid mechanics? 

It's also a scalar function of space and time. Its partial derivative with respect to any direction will give the fluid velocity in the direction of right angle to it. It's applicable only for 2D flow. 
Note that if stream function exists, it represents a possible case of fluid flow and it may be rotational or irrotational and if it satisfies laplace equation, then the flow will be irrotational. 


If you don't know what laplace equation is, then Click here

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