[PSUBS-MAILIST] model testing

Tue Dec 30 09:44:51 EST 2014

Hank, just to bring closure to this thread.  Stress on the boat due to depth scales geometrically between motel and prototype.  Drag scales based on Reynolds number.

As an example for stress, go to Psubs.org flat acrylic viewport calculator that Jon coded based on PVHO http://www.psubs.org/design/viewports/1ATMFD/

Put in a 500 ft depth and a 10" viewable diameter Di and record all results for the acrylic viewport.  Repeat with same depth but 1/10" the viewable diameter, i.e., 1" and record results.  Note that all dimension scale geometrically.  This is based on the assumption that the material is isotropic. These results would not be true for anisotropic materials like a carbon fiber layup were material properties are  directional dependent.  Additionally for carbon fiber, you would not be able to scale the scale the size of the fibers.

So if you are using an isotropic material such as steel, and can fabricate a dimensionally corrected scaled model of a component like a pressure hull including details like weld filler size, then crush depth observed in the motel test cell would match the full scale prototype.  Like any experiment, you would need multiple test to average the results.

Cliff

Cliff Redus
Redus Engineering
USA mobile:  830-931-1280
cliffordredus at sbcglobal.com 

 From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Monday, December 29, 2014 2:41 PM
Subject: Re: [PSUBS-MAILIST] model testing

I am not looking for drag comparisons, I am looking for failure due to pressure comparisons.  I though I read that the Nekton subs were built as a model first to establish crush depth.
Hank --------------------------------------------
On Mon, 12/29/14, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Subject: Re: [PSUBS-MAILIST] model testing
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Monday, December 29, 2014, 3:06 PM

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
depthon a
sphere of A516-70 steel that is 1000mm diameter & 10mm
thick as youdo 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
_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

-----Inline Attachment Follows-----

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20141230/717fa65d/attachment.html>