I am working on a simulation of the impregnation of carbon fibers with resin.
For this, I made a multi-phase VOF model with Fluent. At the current state, the model is pretty simple. The carbon fibers are represented by four rigid circles and their motion into the resin is defined by a profile. The two phases which are involved are air and resin. The air is depicted blue, the resin red. Initially, the model consists of four fibers represented by the rigid walls and the surrounding air, the lower part of the geometry is filled with resin. The geometry is really small, the fibers have a diameter of 7 micrometers.
I activated gravity in this model. As viscosity model, I used k epsilon realizable with scalable wall functions.
The behavour of the solution riddles me quite a bit, so I would really appreciate if you could take a look on my solution mpeg which I uploaded on vimeo:
The geometry is completely closed, no pressure outlet or anything. The mpeg depicts the models behaviour for a simulated time span of a whole two hours. Note that I used variable time stepping in this simulation, so since every time step one fram was created, the animation does not depict real time. For example the motion of the fibers into the resin happens in a very short time of only 16 microseconds. The time step was really small at the beginning and began to rise up when the velocities in the model decreased. It grew up to a size of 1 second near the end of the solution.
As one can see, the gravity kind of works strangely in my model. First, there is some kind of whirl building up, which is kind of understandable. But at some point, the resin should move downwards again and the air bubbles in the resin should rise up. This does happen somewhat, but really slowly. I would have expected that to be happened after a fairly long physical time of 7200 seconds.
This is my first simulation with Fluent and my overall knowledge of this software is still pretty basic. If anyone has some thoughts to share on my solution, please be welcomed to do so.
Thanks in advance!