Learning Forum

[beginner12]

Hi Experts!

I was trying to simulate a simple diffusion simulation, but I faced several problems.

The situation is the diffusion of water vapor into media covered with the wall in simple rectangular geometry. I set the models on including laminar flow, energy, and species transport. Fluid is is the mixture of H20 and N2.

This is a simple rectangular geometry in 2D symmetry.

Left is centerline for symmetry, right and below is wall with 0 concentration, and upper line is mass flow inlet boundary with species fraction (0.2 H20, 0.8 N2). No fluid flow was applied.

I tried to conduct transient simulation so that I can check how the concentration becomes changed along with time, and I expect the concentration should be homogenous in final.

However, I got the results like this.

[Rob]

There's no massflow so nothing enters the domain. If you turn on inlet diffusion you may see an effect, but again there's no reason for Fluent to add mass to the domain. Similarly, how does the displaced material leave the domain?

[beginner12]

Thank you Rob. I thought like moisture diffusion. So, the concentration of species inside the domain was assumed to be 0 as the initial condition before interaction. I will try diffusion inlet and will see what happens!

[Rob]

Try a pressure inlet too: you're after net zero mass transfer and not zero transfer.

[beginner12]

Hi Rob, I really appreicate your response. Just for your previous comments, I cannot find inlet diffusion in type. Should I turn on different models?



Again, thank you for your advice!

[Rob]

It's in the Species panel It's not a boundary type, it's a model setting.