2 replies to this topic

[meer]

Hi All !

 

In the derivation of eq. of Continuity, in differential form using a small volume element, gravity factor effects the mass flow rate in vertical direction b'cz velocity gets effected due to gravity but this gravity factor is not considered in the derivation ????

 

Thanks

[USR]

I feel the continuity equation takes into account the mass balance for a system or may be say a control volume. The mass flow in/out of the system may take place due to any phenomena e.g. gravity or forced circulation pump. Strictly speaking gravity is rather a force and must be accounted for in force balance equations such as the momentum balance equation or the so called Navier Stokes equation. 

[meer]

Thanks dear USR !

 

Point taken... that's why gravity factor (force) comes in derivation of equation of motion but i am still not clear that in derivation of continuity equation gravity should effect velocity in the vertical direction which in turn effects the mass flow rate so this effect needs to be mentioned somehow...?