Is there something like the Poynting vector for hydraulic circuits? The Poynting vector is a representation of the energy flux in electromagnetics, showing the amount and direction of power flow at different points in space.  In electric circuits, the energy is not carried inside the wires (meaning the vector is just 0 inside them?), but by the electric and magnetic fields surrounding the wires.  The DC circuit is the simplest case:



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*Understanding Electricity and Circuits: What the Text Books Don’t Tell You

*IN A SIMPLE CIRCUIT, WHERE DOES THE ENERGY FLOW?
Is there an equivalent concept of energy flux for an equivalent hydraulic circuit?  

Does the energy flow inside the pipes in this case?  I'm guessing the energy flux has some kind of parabolic profile inside the pipes proportional to the flow rate?
 A: There is such a diagram--- it is the flux of energy in the linearized gravitational field (if you use full GR, you get complications with defining the energy). Unlike the electromagnetic case, where the electric field carry the bulk of the energy and the momentum of the charge carriers is negligible, in the gravitational case, it is the opposite.
You can also imagine electromagnetic circuits in which you accelerate very massive spheres which are very lightly charged, and use these as current carriers, and in this case, the momentum of the current carriers will not be negligible.
EDIT: To clarify, there are gravitational fields created by moving water which surround the pipe, like the electric and magnetic fields surround the current-carrying wire. There is an energy flow in these gravitational fields, which carries energy, just like the Poynting flux does. These effects are negligible for ordinary materials at ordinary density. Nearly all the energy flux (all but the tiny negligible fraction in the gravitational field) is carried by the water in the pipe, but the momentum in the water is not analogous to the Poynting vector, it is analogous to the electron momentum, which also carries a small amount of energy in a current carrying wire.
