Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
mass flowrate is non conserved
Posted 20.03.2014, 10:59 GMT-4 5 Replies
Please login with a confirmed email address before reporting spam
I was trying to simulate the water flow into a system with two inlets and three outlets and I used the ''surface integration'' io order to compute the total mass flow rate and I found that the total outgoing mass flow rate is higher (around 5%) than the incoming mass flow rate.
Thus, I decided to do a simpler case, a cylinder representing an injector, and comparing the numerical results in terms of outlet velocity with the experimental ones. Numerical results agree with the experimental but I still found that the mass flowrate through the exit surface is higher (around 1.5%) than the inlet mass flow rate.
Could it be due to the mesh resolution or not?
Thank you in advance for your help.
Antonio
Please login with a confirmed email address before reporting spam
We recommend an upgrade to the current version, 4.4, in which several mass conservation issues have been addressed.
kind regards
Niklas
Dear all,
I was trying to simulate the water flow into a system with two inlets and three outlets and I used the ''surface integration'' io order to compute the total mass flow rate and I found that the total outgoing mass flow rate is higher (around 5%) than the incoming mass flow rate.
Thus, I decided to do a simpler case, a cylinder representing an injector, and comparing the numerical results in terms of outlet velocity with the experimental ones. Numerical results agree with the experimental but I still found that the mass flowrate through the exit surface is higher (around 1.5%) than the inlet mass flow rate.
Could it be due to the mesh resolution or not?
Thank you in advance for your help.
Antonio
Please login with a confirmed email address before reporting spam
is the mass flowrate not conserved even if you increase the mesh resolution?
Does the error change with the mesh or is constant?
Regards.
--
Marino Miccio
Chemical Engineer
marinomiccio.wix.com/home
Please login with a confirmed email address before reporting spam
unfortunately I have not the possibility to use the new version for the moment and I would like to understand which kind of improvements have been done in regarding.
Best regards.
Antonio
Please login with a confirmed email address before reporting spam
in the case of the cylinder, considering the Physics controlled mesh provided by COMSOL, varying from the extremely coarse to the coarse mesh, the percentage difference decreases.
Which is not true in the case of the real geometry.
The problem is that I can not obtain a very fine mesh because of the power of the actual machine on which I am using COMSOL and I would like to understand if this difference in mass flowrate is due to the mesh limit I have or to a COMSOL issue (or both) and how it affects the quality of the simulation in order to well interpret the results I obtained.
Thank you.
Best regads.
Antonio
Please login with a confirmed email address before reporting spam
Next to that try to make your tube longer and plot streamlines sometimes they are re-entering the surface (when a object is disturbing the flow) maybe this can have an influence on the mass flow calculation?