Negative Mass Flow Rate
 

I have a question that I couldn't find a satisfactory answer anywhere so far,
I'm simulating the flow of water in an air conditioning distributor (so far it's one phase) so it's one inlet & four outlets.
Why am I getting a negative mass flow rate at the outlets of my model? what does it depict? Because what I can see from the vector animation is that all the vectors are pointing to the same direction (as that of the inlet) which is in harmony with my simulation & hypothesis.
I also played the simulation in CFD-Post, and the animation was quite confusing, as it kept going back & forth in two opposite directions.
Can anyone please help me with that?

Not sure I understand exactly… From the vectors you can see that the flow is actually going out of the outlets but when you measure the massflow you get a negative value as if the flow was going IN the outlets, right? How are you measuring the massflow? Are you using samples? Did you check their orientation?

No, actually when I use reports>fluxes>mass flow rate, I get negative values for the outlets. But I read here on the forums that it's normal this way, it means that my flow is leaving the domain, because if we add the flow through the inlet to the flow from the outlet (considering the directions) the net resultant should be zero.

Anyway, thanks a lot for your reply.

I am facing a bigger problem now with VOF model.
I'm simulating the 2 phase flow inside an air conditioning distributor, using water as the working fluid in 2 phases (liquid & vapor)

I want to show the contours of the volume fraction of phase 2, but I have a problem where it appears as constant throughout the whole domain (with the gradient on the left stuck on the same value, my original value of 0.35), the same thing happens with the 1st phase but with the value of 0.65.

I read on the topic & I found about patching, although all the tutorials, examples & forum posts suggest using 1 or 0 for the initial value of the 2nd phase, and it's always a simulation of water & air. So I am not sure if it applies to my case.
However, my domain has water in both phases simultaneously, from the very first point of the domain.

I don't know if the problem is my solution method : Coupled & PESTO
or that I'm not doing the patching properly, or there's something wrong with my time steps?

Or should I use a UDF? I don't know how to program those, "yet", but if u think that's the solution to my problem, then I may give it a try.

Please help me out. Any input will be helpful.