[run]

Hi,

I want to measure formation rate of species in OpenFOAM using the following:

dydt(n)= {Y(n-1) - Y (n+1)} / {t(n-1)-t(n+1)} //2nd order accuracy

where, Y(n-1) and Y(n+1) are mass fraction of species at time t(n-1) and t(n+1) respectively.

Could you please tell me how I can store time date and calculate dydt(n)?

Redards,
NurAlam

[dlahaye]

What do you mean by y? Mass species? Does y have a spatial variation? Is yes, in which location (patch, (sub-)volume) do you want to measure the time derivative?

Values for t(n) can be read from log file.

[run]

Originally Posted by dlahaye

What do you mean by y? Mass species? Does y have a spatial variation? Is yes, in which location (patch, (sub-)volume) do you want to measure the time derivative?

Values for t(n) can be read from log file.

Thank you for response.

Yeah, Y is specie mass fraction which is generated by solving specie transport eqution. I am running a simple case of planner channel for reacting flow where left side and right side are inlet and outlet respectively.
I want to measure time derivative of Y along the channel length. I do not understand how I use code to get this.
-NurAlam

[dlahaye]

Wonderful to read your reply.

Do you agree that dydt is a partial derivative that has a value in each cell of the mesh?

Possibly it helps to explain what your interest in dydt is. Possibly we can find other ways to obtain the same information.

[run]

Originally Posted by dlahaye

Wonderful to read your reply.

Do you agree that dydt is a partial derivative that has a value in each cell of the mesh?

Possibly it helps to explain what your interest in dydt is. Possibly we can find other ways to obtain the same information.

Yeah, you are right.