In this case, the change of kinetic energy of the carry-away motion will take place even if this motion is steady ( = 0 ). It is, however, necessary for the inlet and outlet
to be on different radius of rotation.
Fig.F-5
PARTICULARLY SIMPLE EXAMPLES: without relative motion ... = 0
Fig.F-6 and Fig.F-7
For simplicity, we shall limit our attention here to rotation around vertical axis. For other orientations of rotation axis, the actions of gravitational and centrifugal accelerations (the latter is the cemplementary effect to the really existing centripetal
acceleration) change during each revolution cycle. As a result, such a motion is unsteady and quite complicated - as long as rotation is slow. If the rotational speed is high, the gravitational acceleration may be neglected and orientation of the rotation axis ceases to be important.
It is useful to acquaint oneself with the new term in the equation forst on example cases in which most other terms become irrelevant. In Figs. F-6 and F-7 there are such cases with zero relative velocity (- velocity relative to wall of vessel or duct containing the studied fluid). This eliminates not only the kinetic energy term , but also as well as , so that the energy conservation equation retains only the terms:
- in the examples shown, the situation is even more simple by also the pressure energy term becoming unimportant.
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This is page Nr. F03 from textbook Vaclav TESAR : "BASIC FLUID MECHANICS" Any comments and suggestions concerning this text may be mailed to the author
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