Discrete Element Modeling - Science topic

Hello,

im trying to simulate powder flowing through a nozzle carried with a gas.

The particles are small (30µm) and the volume fracion is low.

However its important for me to simulate the interaction, which is why i activated the DEM model, but no particles are injected or tracked.

Can someone tell me what might be the cause of that happening?

Thank you!

Kind regards

Marie

Dear all,

I have experience in DEM with Trubal code, and I am wondering mastering PFC 3D to use it in my future research studies (in the area of geotechnical engineering or industrial processes). How should I start? I mean, what are the best resources on PFC 3D?

Thank you in advance,

Ahmad

I am using LAMMPS to model additive manufactured material and not clear to me how to choose and validate the potential of this sintered material at that scale. I think transferring to the DEM method.

Which is the best software to perform DEM (discrete element modellin) for debris flow and similar phenomenon.

How can we model multiphase flow of DEM (discrete element modelling) and SPH (smooth particle hydrodynamics)/ lattice boltzman method using comsol. Also if there is any other good software to perform similar problem

Dear All,

I would like to ask you, in Fluent Multi-phase flow (Eulerian), 

How secondary phase block primary phase ?

If my have very high fraction of secondary phase, the primary will be blocked or change the direction or velocity.

Anyone can explain mechanism or physics underlying this situation?

Best Regards,

Yannapol S.

Hello, everyone!

I need a software that could pack the arbitrary shaped particles (random packing).

Particle models are prepared in CAD software (see figure for example). Now I need to fill the column (cylinder) with them.

The software is highly preferrable to be free, maybe even open-source.

I heard about Blender could pack spheres, and how about user-defined particles?

Please, advice.

Dear researchers,

I am wondering how to get the grain size distribution of a granular assembly using measure logic. As I read from the manual that we can use measure dump command but it is not working. Could any one provide the support in this regard?

Looking forward to hear form you.

Regards

Shiva

I am simulating cylindrical shapes using DEM. From the literature survey, I got to know two methods, first is to create real cylindrical shape and the second is using multi sphere to approximate the cylinder shape.

I decided to use cylindrical shape. As I see in many papers, the spheres are overlapping, wouldn't this create a problem in mass distribution? How is this problem tackled?

Now say that the body is deformable, then how can I move the individual spheres accordingly?

Rock masses presents structural features that are generated as a response to the stress changes along the geological time. As it has been widely described these structures are one of the main precursors of failure in any kind of rock engineering project. Therefore, these shall be mapped, measured and identified.

It is clear that structural mapping in any project is time consuming, may be hazardous for the person on field and may not provide enough information. Therefore, remote sensing techniques have been proposed in order to obtain greater information in less time without exposing the personal to any kind of risks. This allows us to obtain significant information that we can process and obtain pretty statistical distributions (This information includes orientation, persistence and density of the fractures), that may gives us an insight of how are these fractures distributed along the rock mass.

Additionally, with the development of Discrete Fracture Networks and Discrete Element Software, we can reproduce models that considers jointed rocks masses. However, there is still long ways to go with this technology.

How close do you think that even with large volumes of information a statistical distribution can represent the structure of the rock mass?

Linear and Hertz-Mindlin Contact models are the most used models in modelling the granular material. The contact forces between two spheres are calculated based on the equations of motion (Summation of forces=0). However, does these equations account for the inertial forces (F=ma), where F is the inertial force due the acceleration of the sphere (a) with mass=m.

Hello,

I am a graduate student working on Discrete Element Modeling, and I have a simple question on modeling continuous media using DEM. As you may know, packing fraction in 3D DEM was less than 0.74, thus it may contain at least 26% porosity, which was much higher that of the majority of materials. Accordingly, I intend to know what we can do to address this problem ? Using overlapped particles to increase packing fraction works or not ?

Thanks in advance,

Huihuang

I need to measure the dissipated energy and total energy inside measure circles (RVE). PFC already has commands that calculates these energies in the whole system but there is nothing presented for the mentioned problem!!

Hello all,

My master thesis is on soil compaction simulation using DEM and for calibration of the contact model, I use Oedometer test. I simulate the Oedometer test and compare it with experimental values. The material properties of the calibrated oedometer simulation is then used in the soil compaction simulation. In Oedometer test, I use particles of radius 1mm. However, to reduce the computation time in soil compaction simulation, I scale the radius of the particles 10 times the original value(i.e. 1cm). Therefore. I should also scale up the material property values. I would like to know whether there are any relationship between the radius of the particle and the material properties like stiffness, friction coefficient etc. Thanks in advance.

I am a PhD candidate trying to use DE-LBM for modeling the behavior of a porous media (sandy soil for instance) subjected to fluid flow. I just started to understand the fundamentals of LBM. Is the LBM formulation independent of the coefficient of permeability (k)?

Hello,

In my work with DEM (Discrete Element Modeling) I am often approximating a shape, for example a rock, with N spheres. The normal work flow is to load in a STL file that contains the shape that I would like to approximate. I then pack the interior of the stl outline with the N spheres. I try to match the general shape but there really is no rhyme or reason in placing a sphere in a certain location with some radius.

I would like to write/use an algorithm that can find the "best" way to pack a given stl file. I have been looking into the sphere packing problem from mathematics and physics but they do no allow overlapping. 

I have been working on a program in matlab that would do this for me. Its process is as follows.

1) Import a STL file and find its bounding box.

2) Create a bounding grid with dimensions (7,7,7) (for example...)

3) Out of these points, find only the ones that are inside the Polygon

4) Pick a random point from step 3 and minimize a function F solving for the radius of the sphere (more on F in a bit)

5) Repeat steps 3 and step 4, 50 times (for example...)

6) Pick the best minimum value from the step 5s 50 values that minimized F

7) Using the x,y,z values that yielded the minimum value from step 6, reduce the grid such that the grid is now centered around the x,y,z values that minimized F the most. 

8) Repeat steps 3 through 7 until a convergence on x,y,z,r is found.

The function F was a little tricky to formulate and I don't know if it yields exactly what I want, but the general Idea is as follows.

I would like to compare the volumes of the sphere with relationship to the volume of the polygon as follows.

F = (V_s not V_p) - (V_s and V_p) + (V_p not V_s) or

F = Vol of s that is not in the polygon minus the Vol of s that is in the polygon plus the volume of the poly that is not in the spheres

My question is a combination of if anyone has ran into a similar problem and in what ways could I improve my algorithm.

Thank you for any and all suggestions!

Please let me know in what ways I can improve my question.

Hi friends,

I'm trying to model a Fixed bed reactor whose particle are cylindrical in shape. I would like to use multisphere DEM approach to create packing. Can any of you suggest me about the best among the open source software: LIGGGHTS,YADE or ESys.

Through the Google I came to know that Multisphere approach of LIGGGHTS is available for commercial users. So I can't afford it

I would like to know whether I can use Multisphere approach in YADE or ESys software.

Any help will be of great appreciation

In slope analysis, how to take the initial stress into account using DEM ,such as UDEC?

particle flow code, rock mechanics

I am working on the reduction of WOx into W by using an extended discrete element method approach and I need to model the WOx->W reactions in a single particle model. I already have some ideas, but I am constantly brainstorming. Any contributions?

I'm gonna model a 3D fractured media using ITASCA discrete element package "3DEC". The aim of the model is obtaining deformability modulus of the rock mass. As you know, there is no direct method to do that. So,... I wonder if anyone could present any helpful numerical or statistical way to obtain the deformability.

Thanks in advance.

I am looking for a program to model soil under large deformation and analyze induced excess pore water pressure due to this deformation.

Hello, 

I am looking for a recommendation to evaluate underground excavations in rock and a defined criteria to select type analysis (FEM or DEM) and perform a stress-strain analysis in tunnel section and pillar.

Thank you!

Hi All,

In qualitative level, I am expert to run model using Discrete Element Method. Recently, I have developed associated and non-associate flow rule based Elastic-viscoplastic (EVP) models under FEM, considering reconstitute as well as natural soft sensitive clay and validated my models using seven clays under conventional triaxial test along with true triaxail tests. I am interested to explore micro mechanical features of soft clays. I have used DEM during my Master's in 2007, but they were in qualitative level rather than quantitative. I have never concentrated to extract DEM parameters through experimental data and wondering, is there any one, who can extend his/her co-operation, how to calibrate DEM parameters from experimental or any guide line to extract them for quantitative research? I found couple of papers, where comparisons of DEM and triaxial compression were presented, but calibration process are still elusive.

Thanks in advance.

Mohammad Nurul Islam

I have been reading about semi-supervised techniques and would like to ask if anyone could direct me to any semi-supervised machine learning methods capable of generating probability distribution in a graph-based environment for discrete data? E.g. a Bayesian network like for semi-supervised category.

modeling of separation of grains from other unwanted parts in combine harvester

please introduce me  an easy DEM software 

I'm trying to model events happening at certain time intervals in function of the total time. For instance if a doctor visited patients every 12 hours, it would be intuitive to assume that a group of patients with a mean length of stay (LoS) of 12 hours have an average of 1.0 follow-up visit (and so forth, 1.5 visits for 18 hours etc.). In reality, the actual mean number of visits is consistently smaller because all patients below 10 hours (which would be approx. half of them for a normal distribution) receive 0 visits. Is there a "formal" method to estimate the number of visits from the LoS?

I have been suggested to round down the number of visits as an approximation but I'm not sure that would be academically acceptable... I hope this makes sense as I'm not a statistician. Thanks in advance!

To approximate numerically the solution U we consider the Galerkin space discretization and time discretizations based on the Crank-Nicolson method and on the fourth-order Padé approximation R2,2.

What are the steps required to compute the approximate solution Un+1 at the time level tn+1 using both these discretization schemes?