I am new to SW and I am curios if there is any way to control time step in SW FlowSimulation.
assuming transient analysis?
if you go in calculation control > there is a manual time step option
Thank you for your answer. You replied to my question about centrifugal pump. As far as I understand the simulation of centrifugal pump is semi-transient. This question is connected with it. Since the value of torque oscillates we thought that increasing time step will solve this problem.
increasing the time step will probably make things worse
Dear Jared Conway,
Is there any possibility to change time step in a semi-transient(steady-state) analysis? We ran the simulation of centrifugal pump with casing and faced several different problems. Firstly, mass flow rate did not converge to specified value of 0.1% from total mass flow rate. Secondly, when we compare experimental and numerical values of torque, the experimental is 0.21Nm and mumerical is 0.12 Nm. Thirdly, friction focres exhibits fluctuations with amplitude of 50% of average value. However, the numerical pressure drop is in a good agreement with experimental one. We think that von Karman votices form right after the blades and this introduces such oscillations. In order to get rid of them we thought to increase time step. Thank you in advance. Any help will be appreciated.
the controls are what you are see are what you get, as such, no there are no settings to change that
best to report to your var and get a convo started with the developers
my first thoughts are that you may want to make sure that you are following all the recommendations regarding rotating regions because the solutions will be very sensitive to that and make sure when you are outputting torque you are using best practices on face selection. if some parameters are good and some aren't, i'd guess outputting method to be the issue.
Thank a lot for your answer. Now I have another questions. The first one is concerned with the outlet mass flow rate convergence criteria. What percentage of outlet mass flow rate convergence typically is acceptable? We put like 0.1% but mass flow rate do not converges. The second question is can we use transient analysis for the analysis of centrifugal pump performance?
"what convergence is acceptable" is up to you. for a large flow rate, 0.1% might be over kill. for very small, that might be too big.
when you say it doesn't converge, that could mean a great number of things. for example maybe your time step is not small enough and it is impossible to get down to 0.1%, it is hard to say without actually working through the analysis with you.
can transient simulation be used for a centrifugal pump? if you look at the help and tech references you will see that it is supported within certain guidelines. what exactly are you trying to solve and why can't it be done with steady state?
in either case, I would recommend making sure your problems solves with steady state first.
The inlet flow rate is 0.5175 l/s. The problem is as far as I understand the we cannot control time step in FlowSimulation it is rather determined by the size of the smallest
cell. In addtion, we are forced to refine mesh thoroughly since in some place we have a distance of 2 mm between impeller and inner wall of the casing(the smallest gap in blue colored region). The diameter of the impeller is 120 mm and rotationg region's diameter is 2mm larger. It seems to me that the problem is pressure fluctuations created when one of the impeller blades goes through that region near to exit and where we have the smallest gap.
correct, time step is controlled by the software generally. in a transient simulation you can manually control time step though as well. but in steady state there isn't really a "time step", it is pseudo and not controllable.
your hypothesis could certainly be correct about the issue, but the way you describe the meshing setup seems to match what is recommended by the developers. have you spoken to your var about this?
Have you finally found a solution for the mentioned problem? I am having pretty similar situation with a radial fan analysis.
i would recommend starting your own thread as your problem may be unique. in this user's case i believe the problem was geometry/flow specific
Retrieving data ...