I tried converting a 7yr old MathCAD 11 spreadsheet to MathCAD 14 (then to 15) to solve a transient Heat Conduction Equation in Cylindrical Geometry.
I used the old spreadsheet (attached) to evaluate at heatup of electrical cables from an external fire source about 6-7 years ago. The standard tools (Pdesolve, CreteMesh,..) don't seem to work in later versions of MathCAD.
The current problem to be simulated is localized heat-up of a Tin foil via passing electrical current through a localized area with effective Radius Ro.
The problem involves just one function: Ttin(r,t) - temperature as a function of radius and time, one initial condition, boundary conditions near the origin and farther away, and a time varying heat input source concentrated within Ro.
The Pdesolve (....) block does not appear to generate an error message. I've tried all four of the curve-fitting solver options and cannot generate the mesh needed to generate solution plots. The Error Message is: "The number of functions must match the number of initial conditions." When I search in the MathCAD help -- there isn't much there of value.
The trace error option just refers me back to the Pdesolve block.
I also tried (in lieu of generating contour or patchplots), generating slices representing transient temperature distributions at different radial locations.
This gives the Error Messge: "All evaluations resulted in either an error or a complex result."
-- So before I dig out my old MathCAD 11 CD to get things working -- does anybody have a clue what is going on and why Pdesolve, CreateMesh seem to want more initial conditions and cannot process what should be a rather straight forward solution??
Thanks in advance!
John Bickel
It looks like you retyped that worksheet and have not used the original sheet in Matahcad 15. I guess the sheet you provided will not work in Mathcad 11 either. Look alone at the syntax of PDesolve (not providing the arguments of the functions) and it looks to me on first sight that you had used vector indices where you should have used literal indices.
Yes!
Your diagnosis is correct! Thanks!
I haven't used the Pdesolve in a number of years. Inserting the partial derivatives incorrectly was the problem. Thank you for the advice.
I am new to MATHCAD and i need assistance from anybody using the PDE solver in solving heat equation and other partial differential equations with MATHCAD version 14. Attached is an example for pdesolve about temperature waves in rod i tried solving and its showing me an error message ''The number of functions must match the number of initial conditions''.Thanks
To:
Can't tell exactly what is wrong from a Word file, though it's probably that you used the wrong sort of subscripts for the derivatives in the solve block. To upload a Mathcad file you need to zip it first (this new site hasn't got its act together in that respect yet!). See attached and image below.
Alan
You need to upload your Mathcad worksheet (zip it first) for us to be able to help further.
Note: Make sure you are using .x not [x etc for the differential subscripts.
Alan
Make sure you right click on the image box and uncheck the "Border" box.
Alan
@smdsuleiman wrote:
I have unchecked the "Border" box but the plot is still empty. Kindly help me with some other possible suggestions,i might have done somethings wrong in the 3D format
The possibilities of our crystal balls are limited.
Is has already been said that you should upload your worksheet so we can see what you have done and possibly have done wrong.
If you put the file in a zip or rar archive the upload should work even with this new forum software..
Hi Alan,
Why, if I write the differential equation in the usual way, it gives me a different solution?
Thank you very much
Franc.
Thank you! This one is a great answer!