In the context of moving control volume, which of the following statements is more relevant?
In moving control volume cases are the relative velocity, W, that carries fluid across the moving control surface, whereas it is the absolute velocity, V, that carries the fluid across the fixed control surface.
System and Control Volume:
In order to analyze the Engine, the control volume will have to move with the engine at the same velocity.
When you are solving this type of problem you will need to realize that there is a relative velocity as well as an absolute velocity.
As with a stationary control volume, there is a fluid that is moving through the control volume. However, in this case, the control volume is moving.
The relative velocity is the fluid velocity relative to the moving control volume-the fluid velocity seen by an observer riding along on the control volume.