[PSUBS-MAILIST] model testing

[Cliff Redus via Personal_Submersibles]

Drag results between a model and full scale does not scale geometrically.  You have to scale model and full scale off the dimensionless  Reynolds number.   Reynolds number scaling enables you to scale results between model and full scale using either a water tunnel or air tunnel.

Cliff

 

 

________________________________
 From: Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Monday, December 29, 2014 1:55 PM
Subject: Re: [PSUBS-MAILIST] model testing
  


Hank,
I just ran a test on my pressure program & you get the same crush depth
on a sphere of A516-70 steel that is 1000mm diameter & 10mm thick as you
do on a sphere 100mm diameter & 1mm thick.
What I am not sure of is if you can scale up the drag results on a model.
If you have a scale model that is 1/50th & it takes X amount of force to push it 
at 3 knots, can you multiply X by 50 to get the required thrust?
Alan




________________________________
 From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Tuesday, December 30, 2014 8:43 AM
Subject: Re: [PSUBS-MAILIST] model testing
  

Hank,
      I would say no.  It would have to be so exact that it would be virtually impossible to extrapolate from the small model, and aside from that I think there are other engineering principles involved that would come into play , Sean would be the person to ask !   I know that it is done in wave tanks and wind tunnels, but in those you are looking at laminar flow and such things, not structural strength so much.  You might be able to get a rough idea of how it would start to collapse maybe.  The larger the model the better I would think.

Brian

--- personal_submersibles at psubs.org wrote:

From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: personal_submersibles at psubs.org
Subject: [PSUBS-MAILIST] model testing
Date: Mon, 29 Dec 2014 10:52:46 -0800

Hi all
If you make a scale model of a submarine in complete detail.  Scale the size and metal thickness, is it a reasonable representation of depth capabilities when pressure tested?
Hank
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