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Bill Greene


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46 total contributions since 2014

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Answered
Problem about mixture of ode-pde
I have developed a PDE solver, pde1dM, that Ibelieve can solve your coupled PDE/ODE system. The solver runs in MATLAB and is s...

9 days ago | 1

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Answered
Solve heat equation with source term
T and m are referred to as dependent variables, not independent; x and t are the independent variables. This Example shows how t...

22 days ago | 0

Answered
Unable to meet integration tolerances
Your equations have a fundamental error. Just calculate the "s" term along the length at the initial temperature and the problem...

27 days ago | 0

Answered
How to solve PDE problem
Your PDE can replaced by these two PDE which is a form acceptable to pdepe. However, pdepe, or in fact any numerical method,...

1 month ago | 1

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Answered
Solving second order PDE
The reason that pdepe imposes a boundary condition of the flux equal zero at the center is that this is required for the proble...

1 month ago | 0

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Answered
PDEPE: Unable to meet integration tolerances without reducing the step size below the smallest value allowed at time t.
You are trying to solve a system of ODE which is something pdepe is not designed for. Specifically, the pdepe documentation says...

1 month ago | 0

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Answered
1D Fourier equation with temperature dependent thermal properties
function [c,f,s] = pdex1pde(x,t,T,dudx,diffr,Tfront) diffr=3.34E-10*T^4 - 9.37E-07*T^3 + 9.38E-04*T^2 - 4.80E-01*T + 2.09E+02; ...

2 months ago | 0

Answered
how can I code a system of 2 pdes and an ode for modelling a packed bed
I did some experimentation with your code. Here are a couple of comments related to the changes I made: Because the equations a...

3 months ago | 0

Answered
PDE system - pdepe system example - error or incomplete description on Matlab website?
Looks like you have found an error in this documentation page. If you look at equation 3 in the referenced paper you will see th...

8 months ago | 0

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Answered
Pdepe: Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial derivative.
Your boundary conditions (BC) are specified incorrectly; a qr(i) value of zero and pr(i)=constant is not a valid BC. Since you ...

9 months ago | 0

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Answered
PDEPE: Unable to meet integration tolerances for large values of Ra
The convergence problem you are seeing is due to the strong boundary layer effect near , i.e. the solution is undergoing a shar...

10 months ago | 0

Answered
How to define stepchanges, variable BC for different timeintervalls using pdepe?
The reason that your code didn't show a change in the BC with time is due to the programming error that Torsten pointed out. If ...

12 months ago | 1

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Answered
Euler-Bernoulli's beam ODE or PDE
Take a look at this example: beam dynamics with pdepe

1 year ago | 0

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Answered
Solving advection diffusion pde
The only problem I see with your code is in the boundary conditions. I corrected your bcfun function and have attached my versio...

1 year ago | 1

Answered
Moving boundary problem with Stefan condition (modeling mass and heat transfer for sublimation front)
I think you may be able to solve this problem using the |pdepe| function. The idea is that you model both phases as a single re...

2 years ago | 0

Answered
Error using pdepe - Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial derivative.
The fundamental cause of your problem is that your initial conditions are inconsistent with your boundary condition at |x=0|. M...

2 years ago | 0

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Answered
How to rewrite a PDE equation and set the parameters for solving the temperature changes?
I think you can use |pdepe| to solve this but you need to include both the equation for Ts and the one for Tg; in your pde funct...

2 years ago | 0

Answered
How do I solve fourth order PDE numerically?
I have created an example, which might be of help, showing how to use the |pdepe| function to solve the beam equation : <https:...

2 years ago | 1

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Answered
How to speed up LU decomposition in ode15s solver?
You didn't provide any details of exactly how you are using |ode15s| but I suspect you can substantially improve the performance...

2 years ago | 0

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Answered
what is wrong in my pdepe code ?
The problem you have described is ill-posed. The source term must be prescribed over some finite length of the domain, not simp...

2 years ago | 0

Answered
Error in using MATLAB PDEPE function - incorrect matrix sizing
The line f = [DuDx-Pe.*u(1); 0]; is creating a variable |f| with three rows rather than the correct two rows because |Du...

2 years ago | 0

Answered
Implicit formulation of finite difference with ode15s
I am still unclear on many aspects of your problem. And I am unable to access the paper you reference so that is of no help to...

2 years ago | 0

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Answered
issue with pdepe: "Spatial discretization has failed."
Beyond the problems already mentioned by Torsten, the reason for the error message is that you have listed the returned argumen...

2 years ago | 0

Answered
Step Function as Input Boundary Condition to MATLAB PDEPE solver
I suggest you smooth the sharp corners in your boundary condition profile using a Heaviside function similar to the code below. ...

2 years ago | 1

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Answered
Error in solving system of two reaction-diffusion equations?
The flux term in your pdex4pde function doesn't match the equations you show in your attached pdf. Assuming the pdf is correct,...

2 years ago | 0

Answered
How can I solve an ODE when F(x0)=F'(x0)=0 is given at an unknown point x=x0 using bvp5c?
You have a second order ODE so you need two boundary conditions. The term "boundary condition" implies that you know the locatio...

3 years ago | 0

Answered
Lack of Boundary Conditions to solve PDE (using pdepe function)
In your original code, set your boundary condition function to this: pl = [ul(1); 0]; ql = [0;1]; pr = [pi*exp(-t); 0...

3 years ago | 0

Answered
Solve a system of Partial Differential Equations using function BVP4C
It looks to me like you have 9 dependent variables and only 7 equations and boundary conditions. Clearly, that can't be solved....

3 years ago | 1

Answered
Solving 4th order PDE
You may be able to solve this in pdepe with two equations and two dependent variables h and P. The first equation would be your ...

3 years ago | 0

Answered
Why bvp4c not works?
I think you want: dydt=@(x,y)[y(2); (x-2*y(2))/3];

4 years ago | 0

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