Spheres swelling

Hello,

please provide what is the problem (changing size of particles, computing dri from eq.9, ...).

In general, you can arbitrarily modify b.shape.radius, b.state.mass, b.state.inertia to match your needs.

There used to be a function to scale a sphere including mass (might not be what you want), but I don't remember its name cannot find it at the moment.

Cheers
Jan

Hi Jan,

I want to change radius (dri) over time of the spheres.

b.shape.radius=dri at different time point.

Best,
Mithu

The scale method, can we use different scale or does it need to be constant?

> I want to change radius (dri) over time of the spheres.
> b.shape.radius=dri at different time point.

Instant replay:
please provide what is the problem.

> The scale method, can we use different scale or does it need to be constant?

Please provide some context

Cheers
Jan

As Jan says, we really need to know what your problem is before we can give you any real advice. In general, you could do it like this from the yade input script:

def fradius(t):
   return *insert your function here(t)*

for b in O.bodies:
   if isinstance(shape, Sphere): b.shape.radius = fradius(O.time)

But if you need it to be a function of saturation, you could look at PartialSatClayEngine [1]. In that engine, the swelling of particles is an exponential function that depends on saturation level.

Another example of particle "swelling" is in ThermalEngine where it thermally expands particles according to their temperature [2].

[1] https://www.yade-dem.org/doc/yade.wrapper.html#yade.wrapper.PartialSatClayEngine
[2] https://www.yade-dem.org/doc/yade.wrapper.html#yade.wrapper.ThermalEngine

edit: the for loop on the body container would need to be put into a PyRunner FYI.

https://www.yade-dem.org/doc/tutorial-data-mining.html?highlight=pyrunner#pyrunner

Hi Both,

Thank you very much, the problem is that I do not how implement the swelling model in Yade and different option I have to implement it.

I am thinking of something similar to:

def fradius(t):
   return *insert your function here(t)*

for b in O.bodies:
   if isinstance(shape, Sphere): b.shape.radius = fradius(O.time)

would be great.

Best,
Mithu

> I do not how implement the swelling model in Yade and different option I have to implement it.

you can:
- use python and PyRunner and update particles regularly
- implement new Engine in C++
- ...

I would start with python, something like Robert's suggestion
###
O.engines = [
    ...
    PyRunner(command="swell()",iterPeriod=1), # or iterPeriod=someOtherNumber, or virtPeriod instead of iterPeriod
]

def swell():
    for b in O.bodies:
        # test if body is sphere?
        swell1(b)
def swell1(body):
    rCurrent = body.state.radius
    rNew = ... # eq. (9) using rCurrent
    body.state.radius = rNew
    # mass and inertia does change or not?
###

Cheers
Jan

Thanks Jan Stránský, that solved my question.

Hi Jan,

How do I update the mass and inertia for each iteration?

Best,
Mithu

body.state.mass = value
body.state.inertia = (x,y,z) # 3 principal values

> each iteration?

set iterPeriod to 1

Cheers
Jan