# Axisymmetric Case 3rd Velocity Component

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 June 4, 2014, 12:17 Axisymmetric Case 3rd Velocity Component #1 New Member   Join Date: Dec 2012 Posts: 12 Rep Power: 6 Hi Folks, I'm solving an axisymmetric Pipe-Flow with wedge boundary conditions. On watching the residuals, I was wondering why why all 3 velocity components are solved (see Picture below). Due to the U_y velocity residual my simulation never converges. The wedge angle is 2deg on both sides, so less than 5deg. My blockMesh looks like this: Code: ```convertToMeters 0.001; vertices ( (0 0 -315) (5.25 -0.18333404 -315) (5.25 0.18333404 -315) (0 0 -315) (0 0 0) (5.25 -0.18333404 0) (5.25 0.18333404 0) (0 0 0) (0 0 1000) (5.25 -0.18333404 1000) (5.25 0.18333404 1000) (0 0 1000) (12.5 -0.43650962 0) (12.5 0.43650962 0) (12.5 -0.43650962 1000) (12.5 0.43650962 1000) (100 -3.4920769 0) (100 3.4920769 0) (100 -3.4920769 1000) (100 3.4920769 1000) ); blocks ( hex (0 1 2 0 4 5 6 4) (3 1 158) simpleGrading (0.6 1 0.8) hex (4 5 6 4 8 9 10 8) (3 1 500) simpleGrading (0.6 1 1.5) hex (5 12 13 6 9 14 15 10) (3 1 500) simpleGrading (1.2 1 1.5) hex (12 16 17 13 14 18 19 15) (40 1 500) simpleGrading (1.5 1 1.5) ); edges ( ); boundary ( symmetry { type symmetryPlane; faces ( (0 4 4 0) (4 8 8 4) ); } inlet { type inlet; faces ( (2 0 0 1) ); } pilot { type inlet; faces ( (13 6 5 12) ); } coflow { type inlet; faces ( (17 13 12 16) ); } surrounding { type patch; faces ( (18 19 17 16) ); } wall { type wall; faces ( (2 1 5 6) ); } outlet { type outlet; faces ( (8 8 10 9) (10 15 14 9) (15 19 18 14) ); } rotper1 { type wedge; faces ( (1 5 4 0) (5 9 8 4) (12 14 9 5) (16 18 14 12) ); } rotper2 { type wedge; faces ( (6 2 0 4) (10 6 4 8) (15 13 6 10) (19 17 13 15) ); } ); mergePatchPairs ( );``` Regards Philipp

 June 8, 2014, 05:43 #2 New Member   Kumar Join Date: Jun 2013 Posts: 23 Rep Power: 6 Hi Philipp, I have noticed the same thing too and I think this behavior is very common for Axisymmetric cases with simpleFoam type solvers. I think (although I am not 100% sure) that the third velocity component (Uz) is solved to account for an axisymmetric swirl component and to include the possibility of giving a swirl component to the inlet velocity. Of course, most simple cases like pipe flows, we specify the Uz component at the inlet zero and the swirl actually doesn't develop. I think in your case, we don't need to look at the U_y residual development - we can safely conclude that the solution is converged after 600 iter. regds kumar

 June 8, 2014, 12:45 #3 New Member   Jason Moller Join Date: Sep 2013 Location: Hampshire, UK Posts: 14 Rep Power: 6 I agree with Kumar here. I've recently compared simpleFoam axisymmetric against simpleFoam with the full three-dimensional geometry. Though lacking convergence in Y, the other two components converged and matched up with the full model quite nicely. I believe there is nothing to worry about.

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