The discussion revolves around the applicability of the Hagen-Poiseuille equation for vertical flow in a water tap and other scenarios involving circular cross-sections with varying diameters. Participants explore how the Navier-Stokes equations or alternative equations can describe a viscous incompressible free-falling vertical jet.
Participants express uncertainty regarding the viscosity to be used and the applicability of the Hagen-Poiseuille equation in the discussed scenarios. There is no consensus on whether the Hagen-Poiseuille equation can be applied to free-falling jets or varying cross-sections.
Participants have not established specific assumptions about the viscosity or the conditions under which the Hagen-Poiseuille equation might be valid. The discussion includes unresolved questions about the effects of varying diameters on the applicability of the equations.
If the fluid is in free fall, the hagen poiseulle equation doesn't apply because there is no stationary solid pipe wall.ChaoY said:I honestly don't know what viscosity we should use yet. We're preparing a little experiment to show that Bernoulli equation can be used to calculate velocity for liquid with low viscosity. We also want to calculate the flow rate of the jet this time with viscous liquid. The idea is to show that the Bernoulli equation becomes less effective. Now we're wondering if we could use the Hagen-Poiseuille equation to do the job instead this time considering the viscosity. Do you know if this equation still works if the circular cross section varies from two points?