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I have some doubt on fluid mechanics that need some confirmation. I am on the section that discusses about compressible flow and the effect of variation of flow cross section area.

It stated that that an isentropic flow would obey conservation of mass and what I wonder about is that any chance that an isentropic flow would disobey conversation of mass?

What made me wondering this was I was considering the mass flow rate of isentropic flow in converging-diverging nozzle. If my understanding towards isentropic flow is not wrong, the mass flow rate of an isentropic flow would always be constant no matter of what position it is in the nozzle.

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    $\begingroup$ If it does not obey conservation of mass then where is that mass difference stored in the condi nozzle? Oh conversation is not conservation, autocorrect / predictive type tend to have a limited vocabulary and guess the nearest word... $\endgroup$ – Solar Mike Oct 27 '17 at 18:20
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As far as I understand, especially assuming steady conditions, your mass flow rate is held constant. The thing that is normally changing is the mass flow rate per unit area, or mass flux. Knowing that maximum mass flux occurs under stagnation property conditions, you can actually use simple relationships like Fleigner's formula to solve for your mass flux and if you know your cross-sectional area then your mass flow rate.

So as far as your question, mass flow rate wouldn't change through the nozzle, just pressure and density properties that affect fluid velocity.

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