[PSUBS-MAILIST] model testing

[Marc de Piolenc via Personal_Submersibles]

I thought Froude number scaling only applied to wave drag, that is to 
surface running effects.

Marc

On 12/30/2014 5:22 AM, Sean T. Stevenson via Personal_Submersibles wrote:
> Reynolds number scaling only helps with viscous forces. Form drag
> comparisons require scaling the Froude number.
>
> Sean
>
>
>
> On December 29, 2014 12:06:49 PM PST, Cliff Redus via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>     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
>     <mailto:personal_submersibles at psubs.org> wrote:
>
>     From: hank pronk via Personal_Submersibles
>     <personal_submersibles at psubs.org
>     <mailto:personal_submersibles at psubs.org>>
>     To: personal_submersibles at psubs.org
>     <mailto: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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