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RHABE
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Join Date: Dec 2006
Location: Germany 49° 26' N, 7° 46' O
Posts: 1950
Good Answers: 109

Mathcad Nonlinear Second Order Differential Equation?

01/11/2012 3:47 PM

Hi to experts,

I got some principal information that it is possible to solve NL Diff.Equations with mathcad.

But I have no idea how to proceed and nobody could tell me.

The equation is: p'' + p'²/p = K

This describes the compressible squeeze film damper of constant film thickness and constant channel width. The pressure along a streamline is p(x). The constant K is a function of gap, viscosity and approaching velocity. Isothermal flow for this moment, may be extended later to isentropic flow.

Also nonconstant channel dimensions to be introduced later.

Anybody who can help? Thank you

RHABE
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Pathfinder Tags: compressible squeeze film damper differential equation
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SolarEagle
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Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33392
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#1

Re: Mathcad Nonlinear Second Order Differential Equation?

01/11/2012 4:10 PM

This goes through ordinary and 2nd ord, I think this is what you want...

http://learningexchange.ptc.com/tutorial/96/solving-an-ordinary-differential-equation-using-mathcad

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 All living things seek to control their own destiny....this is the purpose of life
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RHABE
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Join Date: Dec 2006
Location: Germany 49° 26' N, 7° 46' O
Posts: 1950
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#5
In reply to #1

Re: Mathcad Nonlinear Second Order Differential Equation?

01/13/2012 4:16 PM

I tried in the 3 different versions given in Mathcad-help for ODEs.

But none works.

I can try to post the scripts here - tomorrow.

Thank you for your help

RHABE
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Sleepy
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Engineering Fields - Systems Engineering - Member for some time now, see my profile.

Join Date: Aug 2007
Location: Essex, UK
Posts: 364
Good Answers: 3
#7
In reply to #1

Re: Mathcad Nonlinear Second Order Differential Equation?

01/21/2012 1:01 PM

Solar Eagle,

Thanks for that, I am on the brink of buying a Version of MathCad, probably 15 as it will also have the PRIME extension. Your contribution is welcome as I have been havering for a while as I was not convinced that there was good support. You have just shown me that there is.

Thanks very much.

Sleepy
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RHABE
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Join Date: Dec 2006
Location: Germany 49° 26' N, 7° 46' O
Posts: 1950
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#9
In reply to #7

Re: Mathcad Nonlinear Second Order Differential Equation?

01/22/2012 5:50 AM

Sleepy,

before Mathcad I tried Maple, Mathlab and Mathematica but none did fit my thinking as good as Mathcad.

Mathcad has severe limitations - especially as I did not buy the regular support and support I have no access to the discussion forum.

For some weeks I used the free trial version and then a friendly customer came by and dropped and official version - good for me and him.

RHABE
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Sleepy
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Engineering Fields - Systems Engineering - Member for some time now, see my profile.

Join Date: Aug 2007
Location: Essex, UK
Posts: 364
Good Answers: 3
#10
In reply to #9

Re: Mathcad Nonlinear Second Order Differential Equation?

01/22/2012 12:37 PM

Thanks very much for that,

Wolfram has also opened up it's shop in a much more adventurous way.

You can now accesss both Maths and Astronomy through apps on your iPad type device and I am beginning to expreiment with PC Access.

This should provide a much more powerful system. Steve that his site uses a larger server farm than googles!!

Have a go and stay in touch please..

Sleepy
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ferquiza
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Posts: 380
#2

Re: Mathcad Nonlinear Second Order Differential Equation?

01/13/2012 12:14 PM

You want solve with mathcad or anyway?
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ferquiza
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Join Date: May 2008
Posts: 380
#3

Re: Mathcad Nonlinear Second Order Differential Equation?

01/13/2012 3:34 PM

If p(t)=t², K=6.Perhaps p means polinomial and all this is a joke, is it? course i am not interested in giving you the general solution now.-
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RHABE
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Location: Germany 49° 26' N, 7° 46' O
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#4
In reply to #3

Re: Mathcad Nonlinear Second Order Differential Equation?

01/13/2012 4:13 PM

I have Mathcad but nothing else.

p is p(x) or p(r) the pressure profile in the direction of a streamline between two approaching longitudinal (x) or circular (r) plates if an ideal gas is compressed.

RHABE
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ferquiza
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Posts: 380
#6
In reply to #4

Re: Mathcad Nonlinear Second Order Differential Equation?

01/13/2012 6:49 PM

Did you even test the given solution? Did you try a new one based on? I think would help you find more if you write your eq. as d²(½p²)/dx²=k•p .I would forget computers at this stage of your work.-
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RHABE
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Location: Germany 49° 26' N, 7° 46' O
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#8
In reply to #6

Re: Mathcad Nonlinear Second Order Differential Equation?

01/22/2012 5:42 AM

Ferquiza,

theoretical work is outside my possibilities.

Not only because I tried that only as student but this problem with damping by a compressible squeeze film damper is only one of 20 other problems.

So there is no time available for principle work.

In addition an extension to nonconstant gap and width has to be made and I doubt that there will be a closed solution.

thank you for your help

RHABE
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ferquiza (3); RHABE (4); Sleepy (2); SolarEagle (1)

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