4 replies to this topic

[kasri]

dear all,

Momentum is mass * velocity  = kg*m/s but we call Rvo2 also momentum =kg/ms2 .

Please explain why we called them same name which has different units.

thanks

[Bobby Strain]

rho*v² is an energy term, though not exactly. One needs a constant or two to complete the expression. You see this expression related to pressure loss in fluid flow equations. Maybe you can Google to complete the picture.

 

Bobby

[USR]

rho*v²  can be expressed as a product of rho*v and v and if you look closer rho*v is nothing but (mass/volume)*(length/time) i.e. eventually mass per unit area per unit time which is an expression for mass flux and mass flux times the other velocity term is the momentum flux, it is same as any heat flux or diffusive flux. Boy, I wish I could explain it on a piece of paper.

[Bobby Strain]

Google for Bernoulli. There it will become clear.

 

Bobby

[fallah]

kasri,

 

Agreed with USR; in fact, for example, when a compressible flow is moving inside a constant diameter pipeline its mass flux (rho*v) would be constant while relevant momentum flux (rho*v²) is increasing due to velocity increase...

Edited by fallah, 30 November 2013 - 02:15 AM.