Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.
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.
Laminar ar flow- fluid properties inputs- Temperature
Posted 16.12.2010, 09:35 GMT-5 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) Version 4.0a 7 Replies
Please login with a confirmed email address before reporting spam
In the Laminar flow model, fluid properties inputs, Temperature there are two options: 1. user defined , 2. from model (ht/fluid1) . I also have a heat transfer module in this simulation.
could some one explain me therre differences. (I cant find this written in any place).
also i have noticed that when i use the second option (from model), I think the flow velocity better models the material (mater in my case). but on the other hand i cant solve the model for very short times. does anyone know why?
Many thanks,
J
Please login with a confirmed email address before reporting spam
the "from model (ht/fluid1)" is simply the "T" value of the other physics (you have probably 2 physics including a Heat transfer in Fluids (ht/fluid1). This is the one to select if you couple the physics. But if you want to decide which temperature you use in your specific physics you can define it as a "user input".
A user input of fluid1.ht.T (or T2, T3... depending on its internal naming) is the same as the "from model" case
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
the only thing i dont understand is why for short times my model doesnt solve when i use temperature input from ht? but solved fine when i put in a user defined variable.
Thanks,
J
Please login with a confirmed email address before reporting spam
well have you plotted the ht.T temperature to check that it is changing with time?,
and check how the solvers are linked, if you solve all variabls (or if ht is not selected it will not solve at all and the link will be wrong), or if you solve them as a segregated set, which oones are first second, is this the right order. COMSOL makes som guesses, bu sometimes it's wrong w.r.t. your specific model.
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
i dont think its one of what you recommended: the temperature is changing, and the model is solving for both physics (fully coupeled).
what is bothering me is that after 0.001 sec the result looks great, but for 0.0001 sec the result is complete noise (looks like numerical instability).
what do you think doc?
Please login with a confirmed email address before reporting spam
mostly temperature effects are reevant in the order of seconds or minutes, OK if you are working with MEMS its faster, or liquid metal quenching.
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
I dont think its that, but it works now (after some changes to the solver). many many thanks,
J
Please login with a confirmed email address before reporting spam