# Does the bottom of a rotating cylinder influence the shape of the fluid surface?

Given a cylinder of fluid that is rotating the surface is of a parabolic shape. From what I can tell when deriving this the shape of the bottom of the cylinder should not influence the shape of the surface (as long as it is bellow the fluid surface). Is this true in practice? Consider a parabolic bottom very close to the shape of the fluid surface, does surface tension and other such effects distort the surface in any significant way?

• Have you tried analyzing this situation to see how it plays out? Commented Dec 30, 2020 at 21:49
• I’ve tried setting up equations but when using the same method to derive the surface shape as for a cylinder the shape of the bottom does not come into play. So either it doesn’t or my assumptions are wrong. I’ve also tried doing some quick experiments but I don’t have much equipment so I can’t see the surface shape clearly enough to tell if they are different. Commented Dec 31, 2020 at 12:52
• Your analysis already showed that the bottom surface shape does not come into play. So what's the problem? Commented Dec 31, 2020 at 13:13
• I don't know if my analysis is correct, hence why I'm asking if this is true. Especially if this is true in practice where surface tension and other effects might make a big difference. Commented Dec 31, 2020 at 17:10