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May 9, 2012, 22:45 |
Boundary conditions/solver
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#1 |
New Member
Christiane
Join Date: May 2012
Posts: 8
Rep Power: 14 |
Hi!
I have to simulate a screw extruder. I have set up the geometry - I have an inlet and an outlet needle. I have the inlet as one part, the screw fluid as one part and the needle part. I meshed within ANSYS workbench. Named the inlet and outlet as well as the screw wall. I set up: Using laminar flow, defining a new fluid (PCL) with values I found in the literature. For the cell zone condition I put fluid everywhere. For the screw fluid body I also tick frame rotation with rotation around - y axis with a certain speed. Boundary conditions: Inlet-pressure 7e5 Pa, outlet-pressure 0 Pa gauge pressure, screw_wall is rotating around - y axis with the same speed as the frame rotation. Solver is Presto and second order upwind momentum. Monitors is the convergence turned off. Then I initialize. And then run until stable around 4000 iteration steps. PROBLEMS that I have: 1) it is stable, but in the 10^3 range rather than 10^-4 range. 2) I tried standard/ second as well as standard/first, but the problems remains. 3) I didn't rotate the frame. And the same thing happens (stabilized at around 10^3) 4) If I make the whole extruder out of one part, then I get stabilizing in the 10^-4 to 10^-16 range for standard/second. If I use presto - I get still 10^3 and oscillating like crazy. That brought me to the thought, that something must be wrong with my parts and their connection maybe. Please give me some suggestions what I can try out next. Christiane P.S.: I just realized that by setting the extruder up out of three parts, the coordinate system is not in the same position, so that the rotation is not around the rotation axis of the screw. Ho do I solve that? Last edited by chrisausAUS; May 9, 2012 at 23:17. |
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