Learning Forum

[Amirr]

Hello everyone, I am going to push a droplet in a microchannel using horizonal and vertical body forces, may somebody distinguishes and clarify the difference between these three options in a horizontally periodic 2D channel, BF_x, BF_y which are the desired body forces but in N/m^3
1) Periodic between left and right with zero pressure gradient, zero vertical and horizonal gravitational accelerations, momentum sources terms in x and y directions of BF_x, BF_y
2)Periodic between left and right with pressure gradient equals x-body force, zero vertical and horizonal gravitational acceleration, momentum sources term only in y direction of BF_y
3)Periodic between left and right with zero pressure gradient, vertical and horizonal gravitational accelerations as much as BF_x/density and BF_y/BF_x/density, no momentum sources terms in x and y directions.
Many thanks in advance

[DrAmine]

What shall we do? If there is no flow from left to the right then particles will be just under the influence of the additional body forces you are exerting on them. Assuming no momentum coupling (particles does not influence the flow) you can derive the fate of the particles. Or better: run and report:)!

[Amirr]

first thank you for your answer a droplet dynamics using VOF is captured.
pushing the droplet and the matrix phase can be done using
pressure gradient in x direction or
defined gravitational acceleration in x-direction or
a horizonal body force in the cell zone condition as a momentum source term.
my question is with tuning the values they can be completely alternative for each other?
if yes, they can be similar in result? if no, what is the difference and which one is better for me to choose

[DrAmine]

Better to use momentum source terms which you can linearize.

[Amirr]

ok, thanks DrAmine, so you agree that the three ways can be similar but you offer using momentum source term?

[DrAmine]

Momentum source is better to ensure stable runs whenever you linearize wrt transported variable.