Thermo-elastic generation of ultrasound using heat-flux as BC

I try to simulate thermo-elastic generation of ultrasound. As this previous poster, I'd therefore prefer to use heat-flux as a boundary condition. Unfortunately, this issue wasn't resolved in the post.

If tried to modify the example for a thermal US transducer supplied by Chloe Allison found in another post on the topic.

If in this example I change the thermal source definition (line 165) from

defn ymxt tmpr func


defn ymxt flux func

it seems to be no longer working - temperatures and displacements are all zero. However, using "flux" and setting "cupl off" produces a fine temperature field. 

Am I doing something wrong? Is it supposed not to work using "flux"? If so, does this have physical reasons?

I appreciate any help on this.


  • Hey Clemens,

    Similarly to what Chloe wrote on the issue you linked, these issues can be difficult to debug. Can you share the files via your prefered cloud sharing service and we can take a look at it? Flux isn't something I see used a lot so I would like to inspect the files you are working withj before commenting on the potential issues.

    Best regards,


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  • Hello Oliver,

    thanks for your help. The linked zip file contains 3 examples.

    1 - works as expected using "tmpr" in the BCs (this is adapted from Chloe's example)

    2 - now using "flux" in the BCs, but only solving uncoupled - works, too (see temperature field)

    3 - same as 2 but with "cupl mech". Not working, all fields, including temperature, are now zero.

    You can use the runtime graphics to see what I mean.

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  • Have you been able to comprehend my issue?

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  • Still trying to figure out if this is a known issue or if I was doing something wrong.

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  • Hi Grunsteidl,

    Sorry haven't had a chance to look at this. Going to have a look today and get back to you when I find out more.


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  • Hi Oliver,

    it's been a while since your last post here - just as a quick reminder.
    I am still hoping to clarify the issue I posted. Have you been able to take a look?


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