We quickly realized that this
is a case where laminar flow is applicable, since all velocities that can be
achieved via these circumstances are incredibly small. So we dismissed the
point that the flow varies.
Once we have made the orifices
(striving towards identical ones) in different places on a cylinder, we
observed (and measured) that the results are nearly identical, so we dismissed
the possibility that the position matters. The only exception is if the orifice
is on the bottom of the container, in which case the entire liquid pours out
and the phenomenon does not occur in our conditions.
After the
first observations, there were some notable similarities. Such as most
observations were made with similar containers, similar orifices and most
importantly, all were made using water as the liquid. The first question that
pops up is: “How would different fluids affect the outcome?”.
Essentially we are asking what qualities affect this process. We may begin by
understanding that at a certain point, the flow stops, and there is a portion
of fluid (in most cases water) left above the orifice, i.e. the system is in
equilibrium.
This
means that there is a force that keeps the liquid inside and stops the flow and
ideally is equal to the force pulling the liquid from the outside. This is very
different than when the orifice is on the bottom of the container, in which
case all of the fluid pours out. So this phenomenon is geometrically dependent
on the positioning of the orifice. Thus introducing the second question that
arises: “Does the size of the orifice matter, and how so?”.
We
tackled those two elementary questions as we progressed.
However, the first impressions
were enough, to be certain that the phenomenon at question is static. The first
description that we came up with fits the phenomenon for water in a cylindrical
container with a sufficiently small orifice. At the fundamental level, when the
liquid is at rest there must be a force acting on the liquid to keep it above
the orifice – the force that stems from the surface pressure.
This seems to be a good model, unfortunately it
goes directly into the final position, we’d like to investigate further
and truly understand why this is true. And we cannot just ignore the fact that
this a way to ideal system for it to be realistic.