I want to add a Brownian Force to my COMSOL simulation. Unfortunately, I get the warning shown below and I do not understand how to get rid of it.
I am unsure what "second-order wall extrapolation" means. Moreover, I cannot find the "Wall accuracy order list in the physics interface Advanced Settings section" addressed in the warning message.
How do I correct this warning? How can I assign a Brownian force to a domain in general?
To solve this problem, click the "Show More Options..." button right below the Model Builder caption (the button has an eye as icon). An interface will pop up. In this interface, check the checkbox "Advanced Physics Options". Leave the Interface by clicking "ok". Then, click on "Particle Tracing for Fluid Flow (fpt)". Now, there should be an "Advanced Settings" drop down menu. In it, set "Wall accuracy order" to 1.
This gets rid of the warning.