Hello all;

I am working on two phase flow modelling with condensation within a tube using the vof model. Scheme of implicit have been used for interface tracking between two phase at the steady state soloution.

I use outflow boundary condition type in outlet because i would like calculate drop of pressure within tube and therefor i can't use pressure outlet boundary condition and really outlet boundary has'nt no relation with external media.

I use a linear temperature distribution between 345k in inlet to 315k in outlet,but i faced with reverse flow in outflow boundary at duration of soloution process.

Can everybody answer me why this happened and how yo remedy this problem ?

Thanks in advance .

Which is the dimension of its domain? A solution is to increase the length of its domain in the main direction of flow.

Ok,

length of tube is 1.154 m and tube diameter is 0.035m but i think reason for this problem is extending of liquid boundary layer to external zone ,therefor outlet is'nt placed in fully developed zone and length is'nt sufficient for this case. Do you certify this interpretation for this problem?

I can´t imagine other solution. In my opinion you can be correct.