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...

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 years 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...

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...

3 years ago | 0

| accepted

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 ...

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 ...

3 years ago | 0

| accepted

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...

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...

3 years 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 ...

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 ...

3 years ago | 1

| accepted

Answered

Euler-Bernoulli's beam ODE or PDE

Take a look at this example: beam dynamics with pdepe

Euler-Bernoulli's beam ODE or PDE

Take a look at this example: beam dynamics with pdepe

4 years ago | 0

| accepted

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...

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...

4 years 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...

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...

4 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...

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...

4 years ago | 1

| accepted

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...

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...

4 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:...

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:...

4 years ago | 1

| accepted

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...

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...

5 years ago | 0

| accepted

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...

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...

5 years ago | 1

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...

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...

5 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...

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...

5 years ago | 0

| accepted

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...

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...

5 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. ...

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. ...

5 years ago | 1

| accepted

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,...

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,...

5 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...

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...

5 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...

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...

5 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....

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....

6 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 ...

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 ...

6 years ago | 0

Answered

How to formulate boundary conditions for a PDE system?

pdepe is specifically designed for PDEs that are second-order in the spatial direction. That is why it requires you to specify b...

How to formulate boundary conditions for a PDE system?

pdepe is specifically designed for PDEs that are second-order in the spatial direction. That is why it requires you to specify b...

6 years ago | 0

Answered

Using pdepe for 1d transcient heat conduction through a composite wall

You want to model this multi-region wall with a *single* pde and then write your pde function (pdefun) so that it returns a d...

Using pdepe for 1d transcient heat conduction through a composite wall

You want to model this multi-region wall with a *single* pde and then write your pde function (pdefun) so that it returns a d...

7 years ago | 1

| accepted

Answered

Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial derivative.

I see two problems. First, your boundary conditions are incorrectly defined. They should be: pl = [ul(1);ul(2);ul(3);ul(...

Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial derivative.

I see two problems. First, your boundary conditions are incorrectly defined. They should be: pl = [ul(1);ul(2);ul(3);ul(...

7 years ago | 0

| accepted

Answered

How to solve a nonlinear Parabolic PDE IBVP

Since the problem is 1D, you can use the pdepe function.

How to solve a nonlinear Parabolic PDE IBVP

Since the problem is 1D, you can use the pdepe function.

8 years ago | 0

| accepted

Answered

pdepe: why does spatial discretization fail?

I think you want the following in your pdebc function: function [pl,ql,pr,qr] = pdebc(xl,ul,xr,ur,t) pl = ul-0.3639; ...

pdepe: why does spatial discretization fail?

I think you want the following in your pdebc function: function [pl,ql,pr,qr] = pdebc(xl,ul,xr,ur,t) pl = ul-0.3639; ...

8 years ago | 1

| accepted

Answered

PDE Toolbox solution array along a line, to then find the mean value

The evaluate function is returning only one value because the length of your x and y vectors is one. Maybe you want something l...

PDE Toolbox solution array along a line, to then find the mean value

The evaluate function is returning only one value because the length of your x and y vectors is one. Maybe you want something l...

8 years ago | 1

| accepted

Answered

Exchange Problem with PDEPE solver

Torsten said: "Usually, if e.g. material properties change at the interface, the transmission conditions are continuity of te...

Exchange Problem with PDEPE solver

Torsten said: "Usually, if e.g. material properties change at the interface, the transmission conditions are continuity of te...

8 years ago | 0