Learning Forum

[yanahiro0214]

Dear Community,

 

I am currently using DEM-SPH to calibrate the cone penetration test (CPT). However, even with the default CSF model, the SPH and DEM particles are behaving unpredictably, “bursting” like popcorn during the cone penetration process as shown in the above figures.

In realistic conditions, DEM and SPH particles should flow and remain contained within the soil apparatus rather than bouncing away. How can we reduce this divergence of particles to achieve more accurate simulation results?

Alternatively, could it be that the CSF model is not suitable for this CPT scenario?
Configuration: The setup uses Volumetric Fill, with sand (DEM) and water (SPH) particles distributed throughout the entire region. The SPH settings are currently set to default, with the CSF model applied.

Additionally, I have read that an overly large time step might cause SPH particles to diverge. Could someone advise on how to verify and adjust the time step setting currently used by Ansys Rocky?

Thank you very much for your assistance.

Best regards,
Hiroki Yanagawa

[Lucas Bertollo Baggio]

Hello Hiroki,

What is the size ratio between DEM and SPH? Try adding complexity little by little. Start with SPH-only and see if it is stable. 

• If you are simulating WCSPH, check density clip.
• If you are simulating IISPH, check pressure convergence.
• Also check geometry triangles, if skewed. Inappropriate triangle distribution or size would led to this problems.

Check DEM-only too. If the Young Modulus is too low it could be a problem.

 

Best regards,

Lucas