Pig Simulation: Failed to create heat source field extractor

[montanaro]

If you are having problems with the thermal simulation I'd need to see your thermal simulation settings, maybe attach a screenshot where I can see the settings?

[renardChien]

I updated the pig simulation with a Yasoon simulation. If I run the thermal simulation first I get an error message to run the acoustic simulation first, the thermal simulation. Also, the transcranial focused ultrasound tutorial uses the acoustic simulation first.

[montanaro]

Ah true, sorry I was misremembering ... Can you show me what your Thermal source settings look like?

[renardChien]

Yes. The source settings are shown here.

[montanaro]

Seems alright to me.. How big is the file? I can take a look at it if you want. You can send me the input file and I can try to take a quick look at it

[renardChien]

The file is 3 GB. If you send me your email address, I can share a link with Microsoft Onedrive and you can access it online.

[montanaro]

I'd just need the input file ... Is it still that big? I'll send you my email by private message

[renardChien]

I do not know where to find the input file. I have one file that contains the entire project.

[montanaro]

In S4L projects you have a smash file and then a folder with different _Input.h5 and _Output.h5 file ... I would need the .smash file (I incorrectly said input file earlier)

[renardChien]

Here is a link to the .smash file.

https://unigech-my.sharepoint.com/:u:/r/personal/ryan_holman_unige_ch/Documents/seft_yasoon_17082021.smash?csf=1&web=1&e=jXVqne

[montanaro]

Hi, seems I need to be in your network / university to access that link.. Won't let me download it

[renardChien]

I think I must link your email address to share the .smash file.

[montanaro]

I sent you my email by private message, let me know if you get it

[renardChien]

I added your email to the OneDrive link. You should receive an automated email.

[renardChien]

Here is snapshot for the animation of the pressure field. The video is too large to upload.

[montanaro]

Ohh I see what the issue is now ...

You need to have results in the frequency domain (steady state). It then uses this steady state result to heat the tissue

The thermal solver uses the dP/dV field (deposited energy) from the acoustic solver as an input. Since your results are only in the time domain, then this field is not available (you can check it yourself by a) looking at your Field Sensor Settings with Overall Field and see that your recording domain is only in Time Domain ... and b) when you extract Acoustic results, you only get p(x,y,z,t) and you don't get p(x,y,z,f) or dP/dV)

You should therefore change your recording domain to "Frequency Domain" or "Frequency and Time Domain"

[montanaro]

Some other notes about your simulation setup that should be useful

1. For the acoustic simulation you will need a much higher resolution - To get an idea, you are stimulating at 1 MHz and your wavelength will be approximately 1500 (speed of sound in water) / 1 MHz = 1.5 mm (your current discretization is 3mm, way too course)
2. You don't need to simulate the whole body, since the field will be localized near your target, you can limit the domain to a much smaller area encompassing the transducer and the nearby tissues directly under it (after your simulation just make sure the field near the boundaries are relatively small)
3. Get rid of air and replace it with water if possible / appropriate. The time step used in the simulation is limited by the lowest speed of sound in the simulation domain (water = 1500 m/s, air = 300m/s). I'd recommend changing the background material to water (as you already do) and getting rid of the air in Yonsoon and replacing by water (this shouldn't be a problem)
4. Thermal simulation are you sure you're using the correct simulation time? You seem to be heating it for 1microsecond only
5. Again you can maybe limit the simulation domain, but maybe you don't need to since you don't need that fine a discretization as you would for the acoustic simulation

[montanaro]

I also noticed that your transducer is composed of a source element and a reflector, to ensure you don't get back reflections you should set your reflector as a reflector (create new material property -> drag and drop reflector -> select Reflector in materials settings) and make sure the reflector is not in source settings

[renardChien]

Performing the simulation with both frequency and time domain solved the previous error.

Now, I am limited by the student license for the size of the number of cells I can simulation. I must reduce the grid size to get a better resolution. However, I cannot adjust the Boundary- and Boundary+ settings in the main grid.

For the thermal simulation time, I was only simulating for a very short time to debug the system until I could get the thermal solver to work. I plan to increase the simulation time after adjusting the grid volume to a smaller region.

[montanaro]

perfect! under the main grid settings (not the sub settings) you should be able to change the boundaries. The easiest way is to go to padding and change that to a negative number

Another trick is to just create a wireframe around the volume you want to simulate. Then in the Acoustic simulation go to grid settings and remove everything there and just add the wireframe (Note, you should remove all other materials ONLY from grid settings, they should still be elsewhere in your simulation settings - in material settings and voxel settings)