Hello there, Chen!
I'm a fellow user, currently working on a thesis specifically comparing SPH and SCM for lunar rover Terramechanics, so I might be able to shed some light on this. What you are observing is indeed expected behavior due to the fundamental differences in how these methods model the soil physics: - *SCM (Semi-empirical):* This method relies on relations like Bekker-Wong and Janosi-Hanamoto, deduced during the 50s and 60s. In the Janosi shear equation, the shear stress asymptotically approaches a maximum value as displacement increases. Therefore, at high slip ratios (where displacement is huge), SCM predicts that the traction force *saturates* at the soil's shear strength limit. It is a quasi-static approximation, based off the Mohr-Coulomb yield criterion. - *SPH (Physics-based / CRM):* At high slip ratios (>0.8), the wheel acts less like a rolling element and more like an excavator/pump, displacing a significant mass of soil (creating the rooster tail effect). Chrono CRM-SPH use inertial rheology and very comprehensive constituive relations and are able to capture the *inertial forces* required to accelerate these particles and the complex soil deformation/jamming. This dynamic interaction often leads to forces that continue to increase or fluctuate significantly, unlike the capped curve of SCM. It is way more costly in computational terms, but way more precise. Chrono is really good precisely by being able to run physics based simulations, so if you have hardware capability, I would recommend you to use CRM-SPH. So, to answer your question: *trust the SPH results for high-slip dynamics.* SCM is excellent for efficiency in low-slip, steady-state scenarios, but it cannot simulate the complex soil displacement and dynamic excavation that happens at high slip. If you want to dive deeper, the Chrono team has excellent resources and plenty of articles. I highly recommend checking this Workshop presentation: https://sbel.wisc.edu/wp-content/uploads/sites/569/2023/04/TR-2023-02.pdf. If you are interested in going further into the physics, I'd advise you to read into granular media. Hope this helps! Best regards, Rebeca Em segunda-feira, 8 de dezembro de 2025 às 01:42:25 UTC-3, [email protected] escreveu: > Hello > I encountered some result issues while using SPH and SCM tire longitudinal > test benches. When the tire is in the high slip zone (slip ratio>0.8), the > calculated results of the two seem to be inconsistent. The SCM results > indicate that the longitudinal force of the tire is saturated, but the SPH > calculation results show that the longitudinal force increases when the > slip ratio is greater than 0.8. > After studying the literature, I found that both of these situations have > occurred. Which simulation result should I trust? Is the reason for this > phenomenon that SCM cannot simulate soil deformation under high slip > conditions during the calculation process using empirical models? If > possible, I would greatly appreciate it if you could provide relevant > suggestions. > The attachment is a comparison of the simulation results of SPH and SCM in > the literature "An Overview of Tire Ground Contact Modeling Approaches for > Surface Mobility Applications", which is consistent with my experimental > results. > Thanks. > Chen -- You received this message because you are subscribed to the Google Groups "ProjectChrono" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/projectchrono/087f73ed-d5cf-499e-bc2b-d9995e6a24dfn%40googlegroups.com.
