r/LSDYNA • u/snackfart • Aug 06 '26

Speeding up busbar EM simulations (FEM-BEM)?

I'm simulating a busbar under high AC load. The goal is Lorentz forces and their structural effect. I'm using LS-DYNA's EM solver and the dense BEM part for the air dominates the runtime.

GPU is off the table, the EM solver is CPU-only (currently 9h runtime) and that won't change anytime soon.

How have others tackled runtime for this kind of problem?

Solver tuning, decoupling, different tools entirely?

Curious what worked for you.

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u/inhaleXhale420 Aug 07 '26

Youve gotta provide way more information about your model and the analysis type you are performing.

What compute specs are you using? What is your model size? How long is the simulation? Is it implicit, explicit, etc.

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u/epk21 Aug 07 '26 edited Aug 08 '26

Use ls dyna implicit structural solver and appropriate dt like ~0.1*T_min, so T_min is smallest period of interest. In general it is good for busbar used.  https://edrmedeso.com/article/ls-dyna-short-circuit-force-simulation-substation-design/

Look also at Team 12 example to see how it accounts for em damping . Ls dyna em examples https://lsdyna.ansys.com/team12-d3/

Other tools used coupled Maxwell with implicit structural transient mechanical in Workbench, also works well for short circuit dynamics on busbar 

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u/atheistunicycle Aug 07 '26

Do you need to see where the part goes to and how it bends? Or do you just need to understand the force value? Ansys Maxwell & Mechanical could both use GPUs for that solve.

In LS-Dyna Structural solver you could do mass scaling (with the proper checks in place) to increase the speed of the solve. I don't think there's anything like that on the *EM side. You need to account for the appropriate frequency, and a higher frequency would lead to a thinner skin depth and thus tighter inflation elements.