Error

navaneeaero · December 30, 2014, 04:46

Hi everyone

I am trying to Flapping wing analysis. I got "Error: error divergence detected in amg solver temperature" and then suddenly the lift coefficient changed to high value . Could please anyone help me to rectify this problem .

Thanks in advance

LuckyTran · December 30, 2014, 15:15

It is a general divergence error, meaning that your numerical solution diverged. It is closely related to its sibling, the floating point error exception. There are sooo many reasons why that happen.

When does the divergence occur? On the 1st iteration, after a few iterations (say 10, 30, or 100 iterations) or randomly after 10 000 iterations? Most commonly, divergence occurs early in the simulation because of general problems with the setup:

Run the check mesh and check case utilities. Is your mesh of sufficiently good quality? Are there skewed cells? Skewed cells will cause numerical instabilities.

Are your boundary conditions consistent? Setting the wrong boundary conditions will inevitably cause numerical issues to arise.

Is your initial guess, initialization, good enough? A horrible initial guess is also error prone.

You can try reducing the under-relaxation factors a bit to see if you still run into divergence.

December 30, 2014, 04:46	Error	#1
navaneeaero New Member Navaneetha Kannan Join Date: Dec 2014 Location: Coimbatore Posts: 5 Rep Power: 12	Hi everyone I am trying to Flapping wing analysis. I got "Error: error divergence detected in amg solver temperature" and then suddenly the lift coefficient changed to high value . Could please anyone help me to rectify this problem . Thanks in advance

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December 30, 2014, 15:15		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	It is a general divergence error, meaning that your numerical solution diverged. It is closely related to its sibling, the floating point error exception. There are sooo many reasons why that happen. When does the divergence occur? On the 1st iteration, after a few iterations (say 10, 30, or 100 iterations) or randomly after 10 000 iterations? Most commonly, divergence occurs early in the simulation because of general problems with the setup: Run the check mesh and check case utilities. Is your mesh of sufficiently good quality? Are there skewed cells? Skewed cells will cause numerical instabilities. Are your boundary conditions consistent? Setting the wrong boundary conditions will inevitably cause numerical issues to arise. Is your initial guess, initialization, good enough? A horrible initial guess is also error prone. You can try reducing the under-relaxation factors a bit to see if you still run into divergence.