Introductory Fluid Mechanics L8 p2 - Conservation of Mass - Control Volume Formulation

[@wakandaengineer]

Hi I have a quick question. When you are explaining the first special case (around 8:26) should density be included (outside the integral) in the final reduced form of the CoM eqn for incompressible steady or unsteady flow?

[@ronhugo6225]

You could leave it in, but it is not necessary to leave in given that the integral will evaluate to zero - volumetric flow in equals volumetric flow out [m/s * m2 = m3/s] for an incompressible fluid and thus no matter what density equals, your equation becomes 0 = density * 0. L12 p3 looks at the differential form of the continuity equation and there again you will see the density term dropping out of the equation for an incompressible flow.

[@sunmichoi6888]

Thank you so much!

[@ahsanalam7097]

Hello, you mentioned that the unit mass of 1 which is denoted by n. Now in your conversion of mass- control volume formulation in the CS portion you didnt include the n. In your previous video you had an n. Could you explain why the n got removed in the 2nd portion of the equation? (C.S)