[Hossein1]

Hello all,
Using VOF, I'm simulating a water droplet that falls down on a spherical static particle. I'm using 2D model in axisymmetric mode. Using the mesh shown in Fig. 1, when I give the droplet 2 m/s, the result that Fluent gives me is very similar to my experimental results (droplet detaches from the particle surface like a liquid branch as shown in Fig. 2) Pls. click to enlarge the picture.
Fig1.jpg
Fig2.jpg

However, when I increase the velocity to 5 m/s with the same mesh, Fluent cannot give good results and as you see in Fig. 3, the liquid passes over the particle like a simple barrier without detaching from it (while based on my experimental results, in 5 m/s the liquid should be detached from particle surface more compared to 2 m/s)
Fig3-V=5 crash.png

I decided to use a finer mesh. However, not only it didn't help for for 5 m/s but also with finer mesh the same problem happened even for V=2 m/s that I already got good results with the previous mesh (see Figs. 4,5)
Fig4-finer mesh.jpg
Fig5- V=2 finer mesh.png

Could you please help me to know what I should do in such a situation in order to be able to get good results for droplet velocity of 5 m/s?

Thanks for taking time to help me.

PS: time step: 3e-7, particle diameter: 2 mm, droplet diameter: 3.5 mm, particle contact angle: 118 deg