[PSUBS-MAILIST] model testing

[Sean T. Stevenson via Personal_Submersibles]

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 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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