Lab · Fluid Mechanics
Momentum & Forces Lab
One steady planar control volume. Every port states its own area, speed, direction and pressure, and the balance ΣF_ext = Σ_out ṁv − Σ_in ṁv gives the force acting ON THE FLUID. The force the fluid exerts on the surroundings is reported separately, as the equal and opposite resultant.
The fluid
For example the weight of the fluid inside the control volume. Leave at zero to omit it.
Gauge pressure is measured relative to the ambient pressure, so 0 kPa means ambient. It may legitimately be negative. No atmospheric pressure is added anywhere in this calculation.
Ports
P1
Zero flow is a valid state: only the pressure forces remain.
P2
Zero flow is a valid state: only the pressure forces remain.
Control volume
The boundary is a drawing convention, not a geometry: the arrows show where each stream crosses the control surface and in which direction it flows.