The unit in rayleighTaylor3D model

Hello guys, I recently want to modify this model in order to do some multiphase flow research. However, what I found is that in this model, the only input in this model for discretization is the number of blocks and relaxation times. Shown below
const T omega1 = 1.0;
const T omega2 = 1.0;
const int nx = 100;
const int ny = 100;
const int nz = 100;
const T G = 1.2;
T force = 0;
const int maxIter = 10000;
const int saveIter = 100;
const int statIter = 50;
There is no delta t or delta x. so what is the time step in this model and what is the length of the model?
Thank you u guys very much!

Dear applous6,

in lattice Boltzmann, the actual simulation is performed using dimensionless quantities, where delta t and delta x are usually set to unity. To simulate a real physical system (with physical properties), you would have to do a unit conversion. This way, dependent on the physical parameters, you would obtain appropriate dimensionless numbers (input for your simulation) such that the flow behaviour in your simulation matches the flow behaviour of the real system. In this procedure, you will obtain conversion factors to go from one system into another. Amongst others, you will obtain a conversion factor for the time which u can use to get the physical time duration of one time step.
So to answer your question, to obtain these factors you would have to make a connection to a real system and then do the unit transformation.

There are multiple threads in this forum on how to do unit conversion, so I would suggest that you read those (HINT: Search all threads not just the one in the near past which is the default option in the forum search).



Thank you very much kk, I will try to find some threads about it!