FEAP User Forum

FEAP => Programming => Topic started by: epn on September 29, 2023, 11:03:50 AM

Title: Global Equations with Sparse Solver
Post by: epn on September 29, 2023, 11:03:50 AM

Dear All,

I have recently started using global equations to apply a constraint on the average of a field over the whole finite-element domain, which works for iterative solver. However, when I have a global equations, sparse solver (dire,spar) does not work, meaning it does not converge. If I would like to fix this problem, where in the source code should I take a look at? I am using FEAP8.6.

Is it possible to partition the problem into two parts and solve the global constraints in a staggered manner?

Thanks for any input in advance.

Title: Re: Global Equations with Sparse Solver
Post by: Prof. S. Govindjee on September 29, 2023, 11:40:03 AM

How have your implemented you global constraint?

Title: Re: Global Equations with Sparse Solver
Post by: epn on September 29, 2023, 01:17:58 PM

I apply the constraint using a Lagrange multiplier as discussed in the programmers manual in Sec. 5.11 ("Global constraints on elements"). I have a user element where I add the terms associated with the constraint in the suitable locations of the element residual vector and tangent matrix. I access the Lagrange multiplier from ulg(*) array.

Title: Re: Global Equations with Sparse Solver
Post by: Prof. R.L. Taylor on September 29, 2023, 01:58:22 PM

Adding the global constraint should be possible, but will involve quite a few changes. I will look a bit to see what might be the best option.

Title: Re: Global Equations with Sparse Solver
Post by: Prof. R.L. Taylor on October 02, 2023, 06:24:14 AM

This requires more changes than I am able to do at the present time.

Title: Re: Global Equations with Sparse Solver
Post by: epn on October 07, 2023, 12:10:53 PM

Thank you for the respsone.