Learning Forum

[Farah]

1. I'm working with the Under-Relaxation Factor (URF) in my 2way FSI SC simulations, where the default value is 1. If I choose a URF of 0.02, is it reliable? I don't fully understand what it means, so could someone explain it to me in simple terms?
2. Also, how about the RMS Convergence Target? (1E-08) Could you explain that as well?

My simulations often crash, and I need help maintaining convergence in this highly deformed lumen. Any advice would be greatly appreciated.

[Federico]

Hello Farah, 

Under Relaxation factor is used to tune convergence/stability of your simulation. URF values are between 0 and 1, where the lower end will help with stability but come at the cost of slower convergence, and vice versa. 

RMS Convergence Target refers to a predefined criterion used to determine when the iterative solution process has sufficiently converged. The RMS target for the quantity in question (force in your case) is a statistical measure that quantifies the average error across the computational domain. The lower this value, the more precise (not to confuse with accurate) your solution will become, at the cost of computational time.

 

[Farah]

Thank you so much Federico!

Now that you mentioned it, do you know where I can possibly test to see if my RMS convergence target is accurate and precise?