Granular flows and new rheologies

imc

Hi everyone,

I am new user of the software. I am interested in modeling ice granular flow, which has specific non linear rehology, I was wondering if the software could handle this directly or if any case it was suitable to perform a modification or an adaptation in the code to allow this behavior to be simulated.

Thanks, in adavance!

IMC

gfourtakas

Hi,

In theory you could.
The multi-phase model implemented in DualSPHysics, is a non-Newtonian model that can be adjusted by the parameters to behave as you wish (thinning, thickening, pseudo plastic etc, etc ).
Also you could have a "material strength" added to the medium.

Please see guide of DualSPHysics.

Regards,
George

imc

Hi Gorgios,

Thanks for your answer, I read your paper and the DualSPHysics guide, I found them pretty near to what I am up to, but as far as I understood no source code realease yet, and the executable has the solid body option disabled. So, since in my case I need to measure the interaction with a solid body, the code has to be modify right?, accounting for both, the new rheology and the posibility of a solid body interaction?

I was wondering if I could send you a short draft of my plan to the mail that I found in your paper to further explain, it would br great if so!

Thanks in advance!

IMC

gfourtakas

by all means, feel free to email me directly

Alex

Also note that the solid body interaction can be solved by means of DEM model which is integrated in the source code of v4.0. But interactions for objects of size higher than granular

imc

Hi Alex,

Thanks for the answer, I also look at that posibility, indeed the solid will be bigger than the granular particles, but I am planing to use a cylinder directly, sine it is just one, and just change the fluid characteristics.

Thanks!

IMC

imc

Dear Alex,

Re-reading your answer I have another question, if I want to measure the force in a moving body (big) resulting from the interaction with several small floating bodies, which would be the best way to do it?

Thanks in advance.

Alex

There are severeal tools to compute the force exerted by the FLUID onto a solid (such as ComputeForces4.exe) object, but not the force exerted by the others solids. In this last case you will have to code it in the source files.

You can also compute the final movement of an object (motion, rotation, etc) with FloatingInfo4.exe

Regards

imc

Thank you very much Alex, and does that tool works also for moving bodies (eg. rectilinear motion) or only for floating and boundary and that should also have to be coded?

Regards.

Alex

ComputeForces4.exe can be used by any boundary!
Try if you find problems, just ask
Regards

imc

Hey Alex,

So I am making some trials with the software, and I have some questions about the the PartVTK and he ComputeForces tools. If I am trying to modify the computation of the stress Sub Particle Stress tensor (Tau) in the method ComputeSpsTau taking the gradvel terms already compute to account for a different kind of rheological behavior, as far as I have checked in the method Interaction Forces(Fluid-Fluid) everything follows as per the normal momentum equation formulation in SPH with this new tau stress tensor modified.

But as I understood from the guidelines and by making tests of my own the post processing tools will used their own set of equations to make this calculations so If i modify something I should modify also this tools to get my new results right?

Alex

Yes, post-processing tools use their own equations.
For example if you are computing +ACE with PartVTK the momentum equation using artificial viscosity or Laminar+SPS will be used following the same we have implemented in DualSPHysics.

One option that may help you is using "New variables in post-processing tools defined by the user: Post-processing tools are now designed to deal with variables defined by the user. In this way, a user can create a new variable in DualSPHysics source files and one can define its own output data that can be then used by PartVTK, MeasureTool, IsoSurface… "

Basically you can create a new variable to be store in bi4 named "IMC" and the postprocessing tools allows you to read "IMC" in the section of -vars:+IMC

Regards

imc

Ok thanks for your answer.

I will check this possibility, but for example the velocities and positions should be fine then as they are extracted directly from the binary output and are not post-processed, right?

Thanks in advance,

Regards!

Alex

Yes, exactly! Velocities, position and density are just loaded from binary files.

Regards

imc

Hey Alex,

So, I made some modifications in order to store any variable from the JSphCpu class, accelerations and so on, also I change the rheologies to account for the granular behaviors I wanted. Thanks for the advise in fact I used what you suggested.

But now in order to compute the forces, I see that acctually the accelerations of the boundary particles needed are not computed in the InteractionForces methods, so I would like your opinion on what would the best option be, because I was thinking to modify the InteractionForcesFluid method to include the boundary particles as in the description of Compute Forces and store those accelerations, in my new variable, but perhaps you have a better approach.

In anycase thanks in advance!

Regards!

Alex

You are right.. that is why when we want to compute the forces exerted onto boundaries... we use the new tool ComputeForces.exe

ComputeForces.exe solves again the momentun equation using the state of the particles at each output time and computes and stores acceleration of the boundary particles... then summation * mass = force

During the SPH simulation we do not compute and store acceleration of boundaries since these are going to move as we prescribe or remain fixed.

Now you can just compute and store ace of boundaries in the same array ACE but now increasing the memory size!!! for all particles, and not only for fluid ones.

Regards