interFoam + a scalar transport equation
 

Hello, everybody,

I am simulating the collision process between two liquid droplets, using interFoam. The two droplets has the same property, such as two water droplets in air. My objective is to obtain a sharp interface between two droplets. Using setFelds utility, the droplets can be obtained in Paraview, colored by alpha. But they are marked by same color and the interface between two droplets can't be distinguished. (See figure alpha 0 and alpha 1, 0 and 1 denoting timestep 0 and timestep 1.)

Therefore I introduced a scalar transport equation (without diffusion term) into interFoam. The scalar was named T, only a dimensionless variable but not representing temperature. In setFields dictionary, different T values are set to two droplets, and the droplets can be colored by T. But the interface between droplets and air seems to be scattered colored by T, compared to that by alpha. (See figure T 0 and T 1.)

I am a new OpenFOAM user and maybe some more details have been neglected in my work. I want to know whether I should treat that scalar T in the same way
as alpha in the solver code. Some friends may post some advice? That will be appreciated.
Thank you very much!:)

the reply from Dr. Henrik Rusche
 

''Dear Mr. Li,

You will need to follow the routes we take for alpha: Either use
interfaceCompression or MULES since the numerics used for "standard" transport
equations will be too diffusive even if you neglect the diffusion term. This is
the reason why VOF-schemes, interface capturing and level-set were invented.

Best Regards,

Henrik Rusche''

Dear Dr. Henrik Rusche,thank you very much!:)