MATLAB Answers

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## How to solve diffusion equation in spherical coordinate using Matlab?

Yashar

### Yashar (view profile)

さんによって質問されました 2019 年 2 月 18 日

### Yashar (view profile)

さんによって コメントされました 2019 年 2 月 20 日
PDE toolbox in Matlab expects the equations in Cartesian coordinate. In this page it says what the general shape of the equations should be: https://nl.mathworks.com/help/pde/pde-coefficients.html
that is: I want to solve the diffusion equations: Thus, in my case m, a, and f are zero. If we are in Cartesian coordinate then d is one and c, the diffusion constant, is for example 0.001. However, I want to solve the equations in spherical coordinates. Here is a link to Laplacian in spherical coordinate:
How can I solve the diffusion equation in the spherical coordinates in Matlab? or How can I determine the matrix of coefficienct "c" in spherical coordinates?

MM2019

### MM2019 (view profile)

2019 年 2 月 20 日
I want to solve it in 3d for r, phi, and theta.
Torsten

### Torsten (view profile)

2019 年 2 月 20 日
If you create the 3d-geometry as a sphere and solve the equation in Cartesian coordinates, it will work. Why do you want to solve the equation on a 3d block and solve the equation in spherical coordinates ?
Yashar

### Yashar (view profile)

2019 年 2 月 20 日
At the end I want to solve this problem:
One molecue diffuses through a sphere, which represents a cell, and reaches the surface of the sphere. At the surface this molecule converts to another molecule which attaches to membrane that is stays at the surface and diffuses only at the surface (like a 2D diffusion however on the surface of the sphere). This problem is the simplification of a larger problem. If I can solve this simplified problem, I hope I can solve the system of PDEs in this paper ( it is open acess and the equations are in the methods sections):
Here is a snapshot of the equations that at the end I hope to solve: サインイン to comment.

R2018b