Jump to content
Mechanical Engineering

Recommended Posts

Guys & Girls,

I need your help.

Problem is this: Suppose I have a round drum, rotating about its main vertical axis. Top and bottom are closed off. The drum is partially filled with a liquid. How do I calculate the force that the liquid exerts on the top end bottom lid of the drum. Let's ignore gravity.

I have attached 2 calculations I did. The picture I found somewhere on the web.

Which one of the two is wrong and why? Or are they both wrong???

Looking forward to hear from you!







Edited by Carlo Pescatori
Link to comment
Share on other sites

Dear Carlo,

Thank you for an interesting problem. I have attached my solution as a PDF file. It is certainly not guaranteed; there could certainly be algebraic errors in it. I encourage you to check it over very carefully before applying it.

Note that as I have used the Greek letter rho, it has units kg/m^3, not per liter as you did.

I'd like to know more about the origins of this problem. It would be nice if you would send me a message telling me more about where it came up.



Link to comment
Share on other sites

Dear DrD,

thank your for you clear answer!

Some background: this is a real life application of a fast spinning centrifuge. G-forces at the outer diameter of the drum are 45000m/s^2, so the liquid will nearly a cylinder. The centrifugal forces 4500x higher than the gravitation, so it is safe to leave it out of the equation for this application.

Thanks again, much appreciated! 

Link to comment
Share on other sites

Dear All,

For any of you who may have read my previous post on this question, I have to tell you that it has an error. I left out the tangential forces on the fluid element, and thus got a wrong result.

I hope to have a better result for you in a few days, but for now, do not make any use of the result posted earlier. Sorry about that!


Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Join Mechanical Engineering network

    Join us (login) to get full access : Please sign up to connect and participate.

    To download files...please login

  • Who's Online   0 Members, 0 Anonymous, 19 Guests (See full list)

  • Create New...