How to use non-dimensional form of DEM equation in mfix?

MFiX
#1

Hello everyone,

I am looking into nanoparticle fluidisation and I want to use Non-dimensional form of DEM equation to reduce down DEM time step.

So, if there is any option to use dimensionless equation or do we need to change something in code.

Thanks!

#2

This is not an option in MFIX-DEM.

#3

Hey JMusser,

I dont know if I was clear in my query. I am rephrasing my question again -

I want to use the dimensionless form of DEM equation, where I will be giving all the parameters in non-dimension form like K(spring constant), time (collision time), S(intersurface distance), V(velocity) … all will be given in Non-Dimensional form.

Why I want to use non-dimensional form ?

For particle size less than 0.1 micron , collision time goes down drastically to the value of 10^-12 s. To take care of this very low time scale, Dimensionless equation reduce down time to the 10^-9 range.

Ref: https://pubs.acs.org/doi/abs/10.1021/ie051114s one of the paper using non-dimensional form of equation.

PS: It wont be available on GUI but can it be changed in source code.

#4

it sounds like they or you are making a mistake in the nondimensionalization of the governing equations. you shouldn’t get anything for free in nondim form. true you can scale it to make dt arbitrarily large, but then the same scaling should apply to tstop so you end up with an equal amount of computation to get the same nondim. result.

1 Like
#5

Thanks wfullmer,

I had realised there wont be any effect on simulation time by non-dimensionalisation of equations.

Thanks alot!