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• # Flow simulation

Posted by on November 25, 2023 at 4:39 am

Sir, I have to model a velocity profile in the vacuum chamber. For that, we must select a flow based on the Reynolds number. I used the formula for Reynolds number Re = Pvd/u. For d, shall I use the diameter of the gas flow inlet or other dimensions?

3 Members · 4 Replies
• 4 Replies
• ### MIDHUN MURALI

Member
November 27, 2023 at 5:44 am

Haie Rakesh

You need to specify the hydraulic dia for eg if its rectangular section then hydraulic dia is

Dh = (4WH)/2(W+ H) where W is width and H is height

• ### rakeshguptaa0007

Member
November 28, 2023 at 9:19 am

It is a cylindrical pipe for gas flow inlet. So d = 2mm. But I am going to study the flow inside the chamber, so my doubt is whether I have to use chamber diameter?

• ### Rahul

Member
November 28, 2023 at 10:12 am

Hi Rakesh,
For internal flow, the hydraulic diameter can be calculated based on the formula mentioned by Midhun in the case of non-circular cross-sections. For circular cross-sections, such as a pipe, the formula will evaluate to the pipe diameter.
So in this case, you can generally compute the Reynolds number based on pipe diameter if you need to study internal flow. However selecting the hydraulic diameter for Re calculation depends on the problem being modeled, and it is a good practice to do a literature review to check the hydraulic diameter used for that particular problem.
Regards
Rahul
Flowthermolab Support

• ### rakeshguptaa0007

Member
November 28, 2023 at 11:05 am

Thank you…