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 The information provided may be out of date.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.
Oscillating flow problem
Posted 22 dic 2010, 05:20 GMT-5 Computational Fluid Dynamics (CFD) Version 3.5a 1 Reply
Please login with a confirmed email address before reporting spam
Hi,
I have inlet oscillating velocity boundary condition of 20*sin(3.2892*t) at inlet and exit boundary condtion as 1 atm. pressure for a simple 3D cylindrical geometry.When I tried to solve this problem it is displaying the error 'Failed to obtain consistent initial values'.The I tried to obtain the initial values by going to the option 'Solver parametes-time stepping-time steps taken by solver-INITIALIZATION ONLY' settings.Then I ran the problem,still its showing the same error message. ie, while trying to find the consistent initial values itself it is displaying the same error.Can anyone help me in this regard...
with thanks,
S.M.Ananth
I have inlet oscillating velocity boundary condition of 20*sin(3.2892*t) at inlet and exit boundary condtion as 1 atm. pressure for a simple 3D cylindrical geometry.When I tried to solve this problem it is displaying the error 'Failed to obtain consistent initial values'.The I tried to obtain the initial values by going to the option 'Solver parametes-time stepping-time steps taken by solver-INITIALIZATION ONLY' settings.Then I ran the problem,still its showing the same error message. ie, while trying to find the consistent initial values itself it is displaying the same error.Can anyone help me in this regard...
with thanks,
S.M.Ananth
1 Reply Last Post 22 dic 2010, 06:05 GMT-5
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
outlet at 1 atm? what about your initial pressure at your subdomain? should be 1 atm , too. At least, set your pressure to zero (only pressure differencen should be taken into consideration) and, if necessary, adjust your total pressure used in your material properties.
If it is cylindrical, why you don't try 2D-axialsymmetric mode? Saves you A LOT of computational time ...
Another few remarks: 20m/s could be a tubulent flow. you are setting the velocity on the whole inlet to this sin(t...) ? This could trouble with the "wall"-condition which you set up to your wall. -> try to adjust your inlet-velocity-profil to have a zero velocity at your wall-inlet-corner (which should be smooth, of course ;) ). And ... the mesh is important :)
merry christmas!
btw CFD is not really easy ..
If it is cylindrical, why you don't try 2D-axialsymmetric mode? Saves you A LOT of computational time ...
Another few remarks: 20m/s could be a tubulent flow. you are setting the velocity on the whole inlet to this sin(t...) ? This could trouble with the "wall"-condition which you set up to your wall. -> try to adjust your inlet-velocity-profil to have a zero velocity at your wall-inlet-corner (which should be smooth, of course ;) ). And ... the mesh is important :)
merry christmas!
btw CFD is not really easy ..