All Evaluations Result in Either...

[hberner]

I am having slight difficulty graphing this Mathcad problem. When I try, it sends me an error along the lines of "all evaluations either resulted in a complex number or error." The problem is trying to plot the concentration versus position of diffusion/flux through a thin layer membrane. I have to turn it in by tonight, so I would love any help!!

Thank you!

[Fred_Kohlhepp]

You have two more undefined functions CB1(x), and CBL.(x)

And you're trying to solve for CB(x).

Need to define the functions you're not solving for.

[hberner]

Thank you for your response! I am not sure how to define them because they are my boundary conditions?

[RichardJ]

One problem is that odesolve returns a function name, so on the LHS you need CB, not CB(x). CB is the function you then plot. Also, however, you have two undefined functions: CB1(x) and CBL(x). what are they supposed to be?

[hberner]

Ok, now I understand the LHS part. The two functions are the boundary conditions of the system. The surface concentration is denoted by CB1 while CBL is supposed to the concentration at a point (L distance) away from the starting point (CB1). I am not sure how to define these two functions. If you are willing, I would really appreciate help through a Mathcad file... even if it is not how my problem is set up, I think it would be helpful for me to see something similar.

[RichardJ]

If they are boundary conditions then

CB(0)=100

CB(0.08)=10^-7

But I don't know what they are supposed to represent in this equation:

[RichardJ · Accepted solution]

Something like this perhaps?

[hberner]

Thank you all for your help! Got it figured out!!

[ValeryOchkov]

[ValeryOchkov]

Or in Prime with units