[Nek5000-users] velocity projection (p94) for linear simulations

[nek5000-users at lists.mcs.anl.gov]

Hi Neks,

I am running a linear simulation with fixed dt, p93, 94, 95 > 0,
filtering and dealiasing.
However, it seems velocity projection is not affecting number of
Helmholtz iterations which is fixed after a while.

I tested for p94=0 and p94>0 and practically got the same number of
iterations (and even a slight increase in time for time step when p95>0).
However in case of p95=0 and p95>0 I can see the improvement clearly.
So, pressure projection is working fine.
I need tight tolerances, div=1.e-10, hmh=1.e-11, and reducing Hmholtz
iterations can help a lot.

Would you please clarify the situation on velocity projection in linear
cases?

Here is a sample time step :
Step1122816, t= 2.8264667E+02, DT= 2.5173018E-04, C=  0.390 6.0349E+04
5.1942E-02
  1122816 2.8264667E+02 Perturbation Solve:    1
    1122816    Hmholtz VELX:     18   8.3081E-12   1.0343E-01   1.0000E-11
    1122816    Hmholtz VELY:     17   8.0312E-12   2.3905E-01   1.0000E-11
*****   11 alpha:  1.5898E-06  2.6447E-09  1.6940E-09  1.5196E-09 
3.6127E-10  8.4097E-10  6.6903E-10 -2.2649E-10 -1.5484E-09 -3.4627E-10
******  11  4.0897E-09  1.8192E-10  2.2480E+01 alph12
   1122816 U-PRES gmres:      7  9.4727E-11  1.0000E-10  1.8192E-10 
6.8312E-03  1.5541E-02

Best,
Nima

-- 
Nima Shahriari
Linné Flow Center, Mechanics KTH
SE-100 44, Stockholm, Sweden
Phone: +46 8 7906876
E-mail: nima at mech.kth.se

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/nek5000-users/attachments/20140205/19617fc8/attachment.html>