Hello,

I am trying to implement the transport of (at least) one sphere (diameter ~30 micron) in a simple straight tube, with water flowing.

I am implementing the “modified bounce-back rule” to deal with moving boundaries, initially introduced by Anthony Ladd in 1994, my reference paper was written by Feng, Han and Owen in 2007 ( available here: Feng2007) .

I have two questions:

- The modified bounce back rule is defined in this paper as

f_-i (x, t + 1) = f_i (x, t_+) − Alpha_ai * e_i * v_b, where Alpha_ai = 6*w_i * p / Cs^2 (Equation 33),

but other papers give a different definition of Alpha: does anybody know which value of Alpha is the good one?

- Using this definition, I find a particle velocity which is around 10 times smaller than the velocity of the fluid, but I am pretty sure that the transported particle should reach the same velocity of the fluid. Does anybody have some explanation for this different values of velocity, or maybe a clue to solve this problem?

Any other suggestion to easily implement millions of microspheres will be appreciated!

Thank you very much,

Costanza