Learning Forum

[Micah Clarke]

Hello everyone, 

I'm fairly new to Ansys and am having issues when running my solver. It works fine when my materials have low resistivity (0.001-10,000 ohms.m) but as soon as it goes over around 1e7 I have solver pivot errors due to unrealistic material properties and solver pivot warning or error detected in the VOLT degree of freedom in nodes in the material with high resisitivty. Any help is appreciated. Thank you

[Reshmi Raghavan]

Hello Micah,

May I know what is the objective of the simulation that you are trying to carry out?

With a high resistivity or low conductivity value the material characterisitc of the material moves towards an insulator. Maxwell consideres a component as insualtor if the conductivity is less than 1 Siemens/m. 

In you model are you changing the inputs in design setting for the insulator definition? 

[Micah Clarke]

Hi Reshmi, 

Thank you for your response. I am just looking at the electric field between two copper plates. I when the enclosure has a material of air with a resistivity of over 10^7 ohm m it causes pivot errors. Similarly any dielectric material I place anywhere in the simulation (ideally between the plates) with a high resistivity causes the same issues. In the model I'm changing the resisitivity value in the material properties and then re-reading the upstream data

[Reshmi Raghavan]

Hello Micah,

Could you please let me know the solver you are using?

[Micah Clarke]

Hi Reshmi,

 

I have tried iterative and computer controlled and both have the same problems associated

[Reshmi Raghavan]

Hello Micah,

Please let me know if you are doing this simulation in Electrostatic solver / DC Conduction or eddy current solver.

[Micah Clarke]

 

Hi Reshmi, where is this information found? This is what I can see in my solver settings

 

[Ashish Khemka]

Hi,

Please see if the following link helps: * Error* there is at least 1 small equation solver pivot term (eg. VOLT DOF of node 575) (ansys.com)

Regards,

Ashish Khemka

[Micah Clarke]

Hi Ashish, I have seen that thread before and was wondering if there was any way without macros as that is something I have no experience in and would not know how to use at all.

Thanks

[dlooman]

Assuming the volt dof is constrained somewhere, this is usually caused by large differences in the resistivity.  There are only so many significant figures in a numerical analysis (~16) and when material properties vary by more than say 12 orders of magnitude you run into that fact of life.  Sometimes users specify an arbitrarily large value of resistivity to model a non-conductor like air or water.  A value of 1.0 is already an extremely large resistivity and the results will be more or less the same with a value of 1.0 as with 1.0e12.