RE: [PSUBS-MAILIST] basic hidrodynamic question

["Alec Smyth" <asmyth@hsomail.com>]

Ken,

WOW! I ran the numbers and got 684 lbs! I'll probably be decreasing the size
of my dive planes, or their max angle of attack, after running some further
calculations to make sure I've still got enough force at low speeds as well
as high.

I'm assuming that "Pa" refers to ambient pressure? Thanks also to Joe for
the book references. As a matter of fact I'd ordered "Fluid Dynamic Drag" a
couple of days ago but it has not arrived yet.

This group is terrific.

-Alec


-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Kenneth
Schulze
Sent: Tuesday, February 29, 2000 3:18 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] basic hidrodynamic question


Hi Alec,
In aerodynamic terms, try using Newtonian Impact calculation to determine
the
resulting pressure forces on the dive plane surfaces.

Cp = 2 * sin^2 (alpha)
where;
            Cp = Pressure coefficient = (P-Pa)/(.5*density*V^2)
             and alpha is the angle between the dive plane & flow direction

You can assume Cp=0 for the shadowed surface and that force will act
perpendicular
to the surface at the centroid of the dive plane.
Hope this helps,
Ken Schulze

Alec Smyth wrote:

> Hello all,
>
> Over time I've accumulated a fair little sub-related library, but I've
come
> across a VERY BASIC calculation I can't find a formula for in any of my
> books. I need to work this out as part of dimensioning the axles for my
dive
> planes.
>
> Lets say I have a perfectly flat, rectangular dive plane, with a surface
> area of 120 square inches, and I am doing 8 knots. Suddenly I incline the
> dive plane downwards by 30 degrees. What's the magnitude of the resulting
> force? I do realize the force is normal to the plane surface, and I expect
> one gets to it by calculating the pressure and then multiplying by the 120
> square inches... but that pressure is eluding me.
>
> I wonder can anyone help?
>
> Alec Smyth
>
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