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element order and convergence

Posted 27.07.2011, 19:43 GMT-4 Studies & Solvers Version 4.1 1 Reply

Sirisha Govindaraju
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I have a FSI problem that converges when I use first order elements for pressure and velocity and second order for displacements. But I am not happy with the results I am seeing. Hence I changed the element order.

I am using second order elements for the velocity and displacement and first order for pressure. Now the problem is not converging.

It should not be behaving this way because I think that increasing the order of the element should give better convergence. Am I wrong? Did anybody face a similar problem?

Thanks,
Sirisha
1 Reply Last Post 12.04.2014, 08:17 GMT-4
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Hello Sirisha Govindaraju

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Chang-Ho Han
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Posted: 1 decade ago 12.04.2014, 08:17 GMT-4
Hi.

Check the Reynolds number for the fluid flow.
If the Reynolds number is high, the convective term in Navier-Stokes eqn is dominant, which is a nonlinear term.
Then, it's better to solve with first order element in velocity.
Second order element in velocity is good when the diffusive term is dominant.
Hi. Check the Reynolds number for the fluid flow. If the Reynolds number is high, the convective term in Navier-Stokes eqn is dominant, which is a nonlinear term. Then, it's better to solve with first order element in velocity. Second order element in velocity is good when the diffusive term is dominant.

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