How to solve DAE system using ode15s and a modified mass matrix

I am trying to solve a system of differential algebraic equations using ode15s. I have modified the mass matrix accordingly. But I am getting an error related to 'odemass', perhaps because my new Mass matrix is singular. Can anyone help me..

Here is the error ...

* SWITCH expression must be a scalar or string constant.

Error in odemass (line 65) switch(mass)

Error in ode23t (line 180) [Mtype, Mt, Mfun, Margs, dMoptions] = odemass(FcnHandlesUsed,odeFcn,t0,y0,...

Error in TwoD_Main2 (line 22) [z,Y] = ode23t('Alphamodel2',zspan,Y0,options); *

[Torsten]

You will have to supply your MATLAB code to get an answer to your question.

Best wishes

Torsten.

[Smaran]

Hi, I have attached the files of my code here, Please let me know where I am going wrong..

Thanks in advance. :)

Answer 1

[Torsten]

You must not return the derivatives in "Alphamodel2.m" for all values of r.

The solver supplies a scalar value for r each time "Alphamodel2" is called.

Evaluate A, S and T for the value of r supplied by the ODE-integrator.

Best wishes

Torsten.

[Smaran]

The 'r' vector I am using helps to find the values of Y at different radial positions of the modeled reactor. I request you to suggest the modifications that I am supposed to make the code run.

Thanks in advance.. :)