Here's the link, https://doi.org/10.1016/j.cma.2021.114022
This is the paper name: Hu, Wei, et al. "Modeling granular material dynamics and its two-way coupling with moving solid bodies using a continuum representation and the SPH method." *Computer Methods in Applied Mechanics and Engineering* 385 (2021): 114022. On Wednesday, August 23, 2023 at 11:41:56 PM UTC-5 [email protected] wrote: > Just one more thing. I cannot access the paper that has the physical > meanings of the parameters that you mentioned since it's on the university > website. I cannot even see its name. Would you mind sharing the name of the > paper so I can search for it online. > > Thank you so much in advance, > > On Wednesday, August 23, 2023 at 9:28:26 PM UTC-7 Mohammad Wasfi wrote: > >> This is great. Thank you so much Luning. I appreciate your help! >> >> On Wednesday, August 23, 2023 at 4:11:51 PM UTC-7 [email protected] wrote: >> >>> Hello Mohammad, >>> >>> Please take a look at my reply in blue. >>> >>> 1- the bed looked too rigid. I have tried to figure out what to change >>> to get a similar bed to what is in my DEM simulation but I could not. My >>> bed in the DEM sim is generated using a PD sampler and then is allowed to >>> settle. I have noticed that there is no settling phase in the FSI >>> simulation. Is this normal for FSI simulations? What is controlling the >>> rigidity of the bed in this simulation? >>> >>> As you have mentioned, DEM and CRM are different approaches for modeling >>> granular material. For DEM, you need a settling phase, so the particles are >>> packed. For CRM approach, the entire soil bed is modeled as a continuum, >>> you don't need settling phase, in fact, whatever soil depth you got after >>> settling in DEM, you can use that thickness to model the soil bed in SPH. >>> The rigidity of the soil can be tuned using Young's Modulus, I will cover >>> more later. >>> That being said, when I looked at the CMakeCache you posted, I noticed >>> you set the flag "USE_FSI_DOUBLE" to be "ON". For the release/8.0 >>> branch (which is what I believe you are using now), there is a bug when >>> using double precision, which results in your terrain look rigid. The bug >>> was fixed in main, see here >>> <https://github.com/projectchrono/chrono/commit/46bea8f535074bcdf49ed08822e3abf098ed790d> >>> >>> . You can either make the change in your own code, or switch to single >>> precision (set USE_FSI_DOUBLE to be OFF in your cmake). >>> >>> 2- Bed properties? I have noticed that you get some of the >>> parameters from a JSON file and some of them are defined in the simulation. >>> However, it seems that FSI simulations use some different properties for >>> the bed than what is used in DEM. Is it possible to define the bed using >>> ONLY the material properties that I used in my DEM simulation (mentioned >>> above)? Also, I could not find where the particle radius is defined in the >>> simulation and was wondering if the kernelLength parameter is the same as >>> the particle radius. Finally, I would like to set all my simulation >>> parameters in my .cpp file instead of using a JSON file and was wondering >>> about the appropriate way to set such parameters (such as Young's modulus, >>> Can I have a code example?). >>> >>> Every parameters you see in JSON file can be set using APIs. For >>> parameters related to granular soil, take a look at the code here >>> <https://github.com/projectchrono/chrono/blob/release/8.0/src/chrono_fsi/ChSystemFsi.cpp#L626>. >>> >>> There's some book keeping you need to sort out, in terms of what parameters >>> are included in the struct ElasticMaterialProperties, such as particle >>> diameter, friction coefficient, Youngs modulus, etc. For more details on >>> the physical meaning of those parameters, you can read this paper >>> <https://doi-org.ezproxy.library.wisc.edu/10.1016/j.cma.2021.114022>(sec >>> 2.1.1 on the rheology, and some applications). You can use the API >>> SetElasticSPH() to modify your terrain parameters, rather than JSON. See an >>> example in demo_VEH_SPHTerrain_Obstacles.cpp >>> <https://github.com/projectchrono/chrono/blob/main/src/demos/vehicle/terrain/demo_VEH_SPHTerrain_Obstacles.cpp>. >>> >>> Note that kernelLength defines how large a neighborhood of particles is >>> going to have influence on the particle of interest, which is not the same >>> as particle radius. >>> >>> 3- I was wondering about the best way to restrict motion in some of the >>> directions. Also, what is the best way to apply forces to the mesh? >>> >>> This is on the multibody dynamics setup. Note that in the single wheel >>> test demo, global x is the longitudinal direction of the wheel, and global >>> y is the lateral direction, global z is the gravity. There is a prismatic >>> joint between chassis and the axle allowing motion in z direction, >>> prismatic joint between ground and chassis with a prescribed velocity in x >>> direction, and prescribed rotation on the wheel in y direction. In this >>> example, the wheel has restricted motion in y dir. You can modify your >>> screw problem accordingly. For more examples on multibody setup, you can >>> look at the demos in demos/mbs folder. To apply force to your screw object, >>> you can modify the mass of the axle body. >>> >>> [image: single_wheel_sketch.png] >>> >>> Thank you, >>> Luning >>> >>> On Tuesday, August 22, 2023 at 11:26:13 AM UTC-5 [email protected] >>> wrote: >>> >>>> Hi, >>>> >>>> I had some questions that I was hoping you could help me with. I have >>>> been studying the FSI demos to try to better understand the FSI module. I >>>> have mostly been using the DEM engine, so I have noticed some >>>> significant differences between the DEM module and the FSI module. I am >>>> trying to duplicate a simulation that I have done in the DEM ( >>>> https://drive.google.com/file/d/1L9Br1Vf9hsFkjXqbhAZGNpgVep3p5YK_/view?usp=drive_link). >>>> >>>> In this simulation, I first initialize a bed with specific materials' >>>> properties (Young's modulus, possession ratio, static friction, rolling >>>> friction, coefficient of restitution, and cohesion energy density (the >>>> cohesion module is implemented by me)). Then I settle the bed. After the >>>> bed is settled, I drop the screw in a drop phase. After the screw is >>>> settled on the bed, I start rotating the screw at 1 rad/s while >>>> restricting its movement in the x direction and applying a down force on >>>> it. >>>> >>>> To duplicate this simulation, I started with the >>>> DEMO_FSI_SingleWheelTest where I started switching the wheel geometry to >>>> my >>>> geometry and changing the bed size to what is in the DEM simulation( >>>> https://drive.google.com/file/d/18KhOFfXNEIlgcoLTvxTi27XL5soYB4yz/view?usp=drive_link >>>> >>>> - FSI_ScrewTest.cpp). The simulation looks okay but I got stuck on many >>>> things after. I was wondering if you could help me with this stuff: >>>> >>>> 1- the bed looked too rigid. I have tried to figure out what to change >>>> to get a similar bed to what is in my DEM simulation but I could not. My >>>> bed in the DEM sim is generated using a PD sampler and then is allowed to >>>> settle. I have noticed that there is no settling phase in the FSI >>>> simulation. Is this normal for FSI simulations? What is controlling the >>>> rigidity of the bed in this simulation? >>>> >>>> 2- Bed properties? I have noticed that you get some of the >>>> parameters from a JSON file and some of them are defined in the >>>> simulation. >>>> However, it seems that FSI simulations use some different properties for >>>> the bed than what is used in DEM. Is it possible to define the bed using >>>> ONLY the material properties that I used in my DEM simulation (mentioned >>>> above)? Also, I could not find where the particle radius is defined in the >>>> simulation and was wondering if the kernelLength parameter is the same as >>>> the particle radius. Finally, I would like to set all my simulation >>>> parameters in my .cpp file instead of using a JSON file and was wondering >>>> about the appropriate way to set such parameters (such as Young's modulus, >>>> Can I have a code example?). >>>> >>>> 3- I was wondering about the best way to restrict motion in some of the >>>> directions. Also, what is the best way to apply forces to the mesh? >>>> >>>> Thank you so much for your help in advance, >>>> >>>> -- 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 on the web visit https://groups.google.com/d/msgid/projectchrono/98e9d750-121e-474d-8d06-5fe7f9f02e10n%40googlegroups.com.
