The discussion revolves around the application of Bernoulli's equation to piezometric measurements in ideal fluids, specifically comparing the behavior of inviscid (zero viscosity) and viscous fluids in horizontal pipes. Participants explore the implications of fluid viscosity on pressure measurements in piezometers and the resulting fluid heights.
Participants generally agree on the behavior of inviscid fluids leading to zero height in piezometers, but there is disagreement on the implications of viscosity and how it affects pressure measurements and fluid heights in piezometers. The discussion remains unresolved regarding certain specific cases and interpretations of pressure behavior.
Participants note that assumptions about fluid behavior, such as inviscid versus viscous flow, significantly impact the pressure distribution and resulting fluid heights in piezometers. There are unresolved questions about the conditions under which gauge pressures are measured and how they relate to hydrostatic pressures.
Do you have a specific physical problem in mind that we can focus on (involving actual equipment and hardware)?fog37 said:1) I see how a fluid at rest and a fluid in steady motion are different situations. I guess I am wondering if the isotropic pressure, at the same spatial point in the liquid, would be higher if the fluid was at rest (not a stagnation point). How different would the pressure experienced by the liquid parcels be?
That's not what you have in post #26. You have an h instead of a z. h is measured downwards and z is measured upwards. Do you not see the difference? If the datum for both elevation and depth is taken at the upper (free) surface of the fluid, then ##h=-z## and ##p=-\rho g z = \rho g h##2) Ok, but if you take the equation in your post #29 (where ##v=0##, which implies a fluid at reset) and move the term ##\rho g z## on the righthand side, we get the equation $$P=const. - \rho g z$$, which is what I have in my post #26 (different from the correct expression for hydrostatic pressure)...