[ocean-yang]

Hi everyone:
As a cfd beginner I have a question about the Jacobian matrix of the chemical source term.
There is a method called Chemical Explosive Model Analysis(CEMA), which judges the local combustion mode by analyzing the eigenvalues of the Jacobian matrix of the chemical source term.(reference: T. F. Lu , C.S. Yo o , J. H . Chen , C.K. Law , J. Fluid Mech. 652 (2010) 45–64 . )
Unfortunately, I only use the Fluent software, and I don’t know how to extract the chemical source term of the grid and calculate the eigenvalues of the Jacobian matrix, do I need the udf function? Or do I need to use other software?
Looking forward to the guidance of people who understand the CEMA or those who understand the calculation of Jacobian matrix in the chemical source term, and welcome everyone to provide your ideas to exchange

[guru112358]

If you are looking for quick and dirty ways to calculate Eigenvalues there are a variety of numerical methods:
for example Von Mises iterations gives the largest eigenvalue of a matrix with great simplicity


you need to hook up a UDF containing one of these routines written in C to Fluent,when the solver is running,you can make the UDF output the eigenvalues to your fluent terminal.

I have not personally worked on this sort of problem but I believe you need to use certain header files and syntax for this.

search for the fluent UDF manual,it pops up in a google search

as for extracting variables you can put something like a sensor point in Fluent

All the best!

[ocean-yang]

Thank you very much for your reply, I believe it will be of great help to me.