# Items tagged with numericnumeric Tagged Items Feed

### Finite Difference Method for PDE...

7 hours ago
0 1

Dear all

I have a PDE and its analytical solution. I want to find the numerical solution by Finite Difference Method.

I duscratize the PDE and boundary condition and Could not able to solve them togethe.

Here is the file FEM-Nu.mw

### how pdsolve time-fractional equation in maple?...

September 20 2016
0 6

hi...how i can pdsolve this equation numerically or analyticlly?

this equation is time-fractional  equation with generalized Cattaneo model

where

is the fractional derivative operator considered in the
Caputo sense.

FRACTION.mw

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September 19 2016
0 4

Hello everybody!

Please help me to solve the attached partial differential equation. I am getting an error. I do have its analytical solution and that works fine.

The error is as follows
Error, (in pdsolve/numeric/plot) unable to compute solution for t>HFloat(0.0):
solution becomes undefined, problem may be ill posed or method may be ill suited to solution

The worksheet is attached hereshortsngle.mw

### Error for (in EpResult) ...

September 14 2016
2 1

what does this mean:"Error, (in EpResult) cannot evaluate the solution further right of 0.36919453e-2, probably a singularity" as I cannot find any relevant material of this error.

I am simulating a condition and get to the final stage of calculation, and this error occurs....

### Numerical solution of a function...

September 14 2016
0 7

Hi,

This is regarding numerical solution of a function and plot. I have a function in the form of , and i need to plot it with omega (as the expression is too long i cant insert it here). Now, if i am changing the range of omega in plot command then I am getting different plots for the small values of omega. Let's say if i change the range from 1..10 to 1..50 and look at the plot in the range of 1..3 then the plots looks different. Apart from this if i change the value of Digits  from 10 to 30 or 40 then every time i am getting an entire different  plot. As the expression if too long i cant convert it to Matlab expression and plot there. How to fix these issues. Please help me regarding this.

Regarding

Sunit

### 2D Grid Interpolation...

September 13 2016
2 7

Hi,

I'm solving a 2D grid with some finite-diference methods. The result is a surface, i.e f(x,y) = z. Where X and Y and points on a grid.

I then need to integrate over this grid, i.e

int(f(x,y),[x=0..10, y=0..10])

I have tried interpolating the grid. I've used CurveFitting:-ArrayInterpolation() to interpolate points in this 2D space and then integrate over them.

I'm using a 30x30 grid, but this interpolation scheme takes far too long. The function generated from the ArrayInterpolation creates an interpolation every time a point is evaluated, which I assume is why the integral is very computationally expensive.

I would like to create a piecewise analytic function from the 2-D grid, perhaps using CurveFitting:-Spline(), however from my understanding this only works for 1D objects?

Is there any better solution for integrating a 2D numeric grid?

### How to compute the convex hull of points with both...

September 09 2016
2 10

I would like compute the vertices of the convex hull of finitely many points in some \mathbb{R}^{n}, where the coordinates of these points could be rational numbers or irrational numbers like \sqrt{2}.

I know that PolyhedralSets[ConvexHull] is a direct command, however it does not support irrational numbers. But if I transform all coordinates into floating point numbers, for some rational numbers the rounding error would be large enough to affect the result. For example, after the transform some collinear points are no longer collinear.

Thanks!

### pdsolve-numeric error...

September 08 2016
0 11

I am trying to solve a PDE using pdsolve-numeric. I am getting an error related to boundary conditions.
Please see the follwing worksheet and suggest me some solutions

pdsolve.mw

### maple takes too long(cannot maybe?) to compute thi...

September 06 2016
0 2

So I have an integral that computes perfectly in wolfram alpha but not in maple...

I will post it here

int(1/((4.532055545*10^9/f^4.14-2.311250000*10^5/f^2+(111*(1-0.2163331531e-4*f^2+2.340001656*10^(-10)*f^4))/(1+0.1081665766e-4*f^2)))*(6*10^(-21)*abs(1/f^(4/3)))^2, [f = 50 .. 1500])

If you try that exact line of code in maple, it will not compute (is stuck on evaluating)

Best Regards to all,
Zeus

### Linear Instability Analysis ...

September 02 2016
0 2

Hello Everyone,

May I ask you about this  "Error,   (in pdsolve/numeric/process_PDEs)  number of dependent variables and number of PDE must be the same". Does anyone have idea about solving linear instability equation (flow inside pipe, oscillating flow) ?

Thank you,

### How to deal with improper integrals from zero to i...

August 26 2016
0 2

Dear all,

I would like to compute numerically using Maple the following improper integral

However, Maple does seem to give a result for this integral. I have tried to compute from e.g. 0.001 as an approximation but it turns out that the integrand diverges as s goes to zero. I have also tried some options such as method = _d01amc but I get Error, (in evalf/int) powering may produce overflow.

I would appreciate it if someone here could provide with some help with regards to the computation of such improper integrals. Thank you.

### how to evaluate numerical inverse Laplace transfor...

August 26 2016
0 5

I would like to apply inverse Laplace transform to U(x,p), which is defined by

For simplicity with my calculations, I assumed p:=i*beta^2. That is why I have the following equation after applying Laplace transform

(beta=0 is not a pole, that is why I removed the last term in my calculations later. Because there is no contribution) where

Here p and beta are complex values, we can write Re(p)=-2*Re(beta)*Im(beta), Im(p)=(Re(beta))^2-(Im(beta))^2 due to p:=i*beta^2. I numerically compute the roots of h(beta), you can find the numerical values of beta (I assumed digits are 50 due to accuracy ) betap.mw

Finally, I would like to plot U(x,t) with the values t=0.8, lambda=1, L=10, k=1. For checking the figure give t=0 and observe that U(x,0)=0.

I am expecting the plot is more or less like the following figure

PS: I already tried to solve and plot the problem, but I could not find where I make a mistake. I  share the worksheet below. Thank you!

complexplot.mw

### numerical equation using loop for...

August 23 2016
0 2

hello evrey one ,

my question is how can i solve numerical equation using loop

for each beta => deolve and export via excel
thank you

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### Where is the help text for this environment variab...

August 23 2016
1 0

In a Maple Primes reply by Joel Riel on Sept. 14, 2011 he included the following command referring to warnings issued from a dsolve, numeric command having events containing a halt action:

_Env_in_maplet := true:  # incantation to suppress integrator warningsWhere can if find explanatory help for his command and any others of a similar nature?

### Error, (in dsolve/numeric/bvp/convertsys) unable t...

August 22 2016
1 2

restart;
Digits := 5;
with(ODETools);
with(student);
with(plots);
inf := 5;
with(LinearAlgebra);
equ1 := (1+2*n)*f(eta)*(diff(theta(eta), eta))/(1+3*n)-(diff(theta(eta), $(eta, 2))) = 0; equ2 := ((1+n)*(diff(f(eta), eta))^2/(1+3*n)-(1+2*n)*f(eta)*(diff(f(eta), eta, eta))/(1+3*n))/Bo+(diff(f(eta), $(eta, 3)))^n-theta(eta) = 0;
Bcs := f(0) = 0, (D(f))(0) = 0, (D(f))(inf) = 0, theta(0) = 1, theta(inf) = 0;
Bo := 1; n := 2;
SolP1 := dsolve({Bcs, equ1, equ2}, numeric);
Error, (in dsolve/numeric/bvp/convertsys) unable to convert to an explicit first-order system
SolP1(0);
SolP1(0)

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