Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Stack design_STS-1

Stack design_STS-1

Stack design_STS-1

Hello everyone,

For stack, designed as per STS-1, i am in a situation that critical velocity is lower than design velocity.
So far i know by introducing helical strakes or other attachments, critical velocity can be increased.

But my question is how to evaluate critical velocity after introducing strakes.

Please provide your opinion/ guidance on same.


RE: Stack design_STS-1

Further to above:

In Dennis Moss, Chapter 6: special designs, it says that Vortex shedding can be eliminated by introducing helical strakes upto top 1/3 portion of stack.

As per above, does it mean that by introducing strakes there is no need to check for vortex shedding.

If so than how to validate it on paper.


RE: Stack design_STS-1

You have asked the same question twice - this is not the done thing.
As regards you question. Introducing strakes does not negate the nedd to check for resonance. How do you know how many - their width- the spacing of these strakes? I think you should employ a qualified stack design engineer.

RE: Stack design_STS-1

In some cases, it may be practical to adjust some of the thicknesses to adjust the frequency.

RE: Stack design_STS-1

After increasing thickness of components when I checked output for STS in pvelite, it is observed that still critical velocity for vortex shedding is less than the mean critical velocity.

To investigate further for the cause of failure, I checked ovalling frequency.

But I found that ovalling frequency is more than natural frequency of vessel even with less thickness of shell components. See the attachment.

Still, I am not able to conclude the reason for failure.

I request you to explain the same if possible.


RE: Stack design_STS-1


Have you contacted the people who developed the computer program (COADE) that you are using ?

What did they have to say ?

Sr. Process Engineer

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close