Answers 1
Q1.
For S1:
This must be the same as the mass flux through S2. (Otherwise, mass would accumulate
between these surfaces.)
Answer: 15.7 kg s–1 (both surfaces).
To calculate the mass flux in general, use the component of velocity normal to the area or,
equivalently, the projected area normal to the velocity):
CFD Answers 1 – 1
Q2.
Steady-state momentum principle:
force (on fluid) = (momentum flux)out – (momentum flux)in
where, for a uniform velocity:
momentum flux = mass flux × velocity
For the x-component of momentum and the fluid in a control volume encompassing the
region shown:
Hence,
Answer: 503 N.
CFD Answers 1 – 2