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06-15-2014
11:23 PM

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06-15-2014
11:23 PM

MathCad 14 and PDE commands

I have the following diffusion problem form "Mathcad for Engineers" Adidharma et al. I have worked through several ODE examples successfully, however when working through the attached worksheet I receive the following errors, worksheet is attached. I have the following questions:

1)When setting up the function the derivative notation of d/dx or d/dt is allowed is this also allowed in the PDE solver?

2)In the book on Mathcad online it mentions that PDE Boundary Conditions are required to use "CRT F7" to setup a derivative, however when I do this I still have an error?

3)The online book also mentions that boundary conditions need to have literal subscripts using ".", I have tried entering the function "f" and then the literal subscipt "." followed by "x" however, this did not work?

Please advise what I am doing wrong. I have Mathcad version14. Thank you in advance.

Sincerely,

Walter

3 REPLIES 3

06-16-2014
11:53 AM

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06-16-2014
11:53 AM

You have to omit the function arguments when you call pdesolve and also when you do the 3D-plot. Its the very same as in this thread of yours: http://communities.ptc.com/message/243735#243735

The attached file should help.

06-18-2014
12:47 AM

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06-18-2014
12:47 AM

Hi Werner,

Thanks for the help but the fundemental reason that I was not able to figure out the issue is that the function with the PDEsolve needs to be re-typed in again from scratch if an error is corrected in the equations prior to the function with the PDE solve in it. Once I did this the problem was able to be solved and modfied as needed. This information is not documented in any book or other material I have come accross.

Sincerely,

Walter Stonas

Chemical Engineer

06-18-2014
03:11 AM

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06-18-2014
03:11 AM

the fundemental reason that I was not able to figure out the issue is that the function with the PDEsolve needs to be re-typed in again from scratch if an error is corrected in the equations prior to the function with the PDE solve in it.

Iits not clear to me what exactly you mean by that!? It should never be necessary to retype anything from scratch just to correct a type or some other error. If autocalc is on, changes should update the whole sheet immedeatly. Sometimes it happens that an evaluation will not update (you see x= and nothing on the RHS) or that a a subexpression still is prited in red as if an error was thrown while its already corrected. In this case pressing CTRL-F9 to recaclulate the whole sheet or F9 to recalculate the current region should do the job.