NTERUP loop / forces / possible bug?
Posted: Wed Apr 06, 2011 1:55 pm
Hi,
I was looking at the drag and lift coefficients for laminar flow past a 2D cylinder and the effect that changing NTERUP in usini1 would have. I use the example in usproj to calculate forces.
The attached v1_merged.pdf gives the results, they're not good!
So we looked into how the forces (grep efforts in sources) are calculated and it's a sum ra(iforbr...) in 5 steps. Three of these (1st in preduv, vissec, divrij) are only performed when ITERNS=1 (the loop is performed NTERUP times). However, two parts of this are done on every loop-iteration (condli and 2nd in preduv) so I assume it's damping itelf.
Changed these with an if statement to only be performed for ITERNS = 1 and results are better, v2_merged.pdf.
By the look of it the force-array-sum is only effecting the outputted ensight file (and if you choose to use it in usproj, for example) so can't see it having much of an effect on results.
I've attached the subroutines I changed. Can someone let me know if what I've done is okay.
Cheers,
James
I was looking at the drag and lift coefficients for laminar flow past a 2D cylinder and the effect that changing NTERUP in usini1 would have. I use the example in usproj to calculate forces.
The attached v1_merged.pdf gives the results, they're not good!
So we looked into how the forces (grep efforts in sources) are calculated and it's a sum ra(iforbr...) in 5 steps. Three of these (1st in preduv, vissec, divrij) are only performed when ITERNS=1 (the loop is performed NTERUP times). However, two parts of this are done on every loop-iteration (condli and 2nd in preduv) so I assume it's damping itelf.
Changed these with an if statement to only be performed for ITERNS = 1 and results are better, v2_merged.pdf.
By the look of it the force-array-sum is only effecting the outputted ensight file (and if you choose to use it in usproj, for example) so can't see it having much of an effect on results.
I've attached the subroutines I changed. Can someone let me know if what I've done is okay.
Cheers,
James