I am using SimFD 2014 for calculating drag. During simulation, I noticed that I can watch the "Wall Results" window and it will update the forces in real-time as the simulation proceeds. Towards the end of a simulation these values are very stable for typically several hundred iterations. However, often I notice that once the simulation stops and I re-check the wall results the value has changed by up to 10% from the "steady" value I observe during the simulation. Should I not trust the value calculated during simulation for some reason and only rely on the post-simulaton value? I'm a bit concerned and not as confident in my results as I would like to be.
Thanks!
Solved! Go to Solution.
Solved by Royce_adsk. Go to Solution.
Correction. In some simulations, the "Wall Results" shown during calculation and the values after the calculation has termiated are different by up to 25%. If it makes a difference, I am only looking at forces.
Are you using any of the 2014 service packs? When you go to the about screen, what version number is listed?
Thanks!
In the past the wall force calculator wouldn't show the pressure and shear drag during runtime. It only showed the pressure forces. Also, there was another issue at one point that if you were looking at the wall results during runtime, the widget wouldn't update when finished for the last iteration. Meaning it was 1 iteration behind until you went through and clicked on calculate again with the surfaces selected.
When it comes to resolving both of these issues and using a more accuarte method to calculate wall forces, I would suggest using this flag set at the sceneario and 'Default' level. Make sure you close down and reopen the UI and then run for at least 1 iteration to get the updated results. This option was documented in the What's New for 2014
I am using version 14.0, not sure if that also indicates any service packs?
I'll try your suggestion regarding the flag settings and see if that helps.
Thanks for the feedback!
OK, I was able to set the flag in the scenario, but it doesn't seem to show up in the default flag settings page. It is strange because if I start to type resid_bdry in the search bar it gives me the specific flag as a suggestion, but then when I select it I get no results returned in the window. What am I doing wrong?
I enabled the resid_bdry_force_calc flag for a scenario, restarted the UI and re-ran the entire simulation to check if this worked. I still get the same issue. The drag force reported by the wall calculator is stable for several hundred iterations, but after the simulation stops and I recalculate the drag force the value jumps up by ~13% (in this case). Note that I am still unable to enable the flag as default, but I wouldn't think that would change anything for a specific scenario where the flag is enabled.
I'll commuicate that with development.
You can leave it out of the default level, that should just mean that you need to click on caculate when it is done solving to get the last result and not the previous step.
You should also upgrade to SP2.