[Nek5000-users] Problem in obtaining eigenvalues through Arnoldi (using NEK5000 with the ARPACK library)
nek5000-users at lists.mcs.anl.gov
nek5000-users at lists.mcs.anl.gov
Fri Jul 13 05:00:28 CDT 2018
Hi Adam,
Thanks for your reply.
0.100000E-09 p021 DIVERGENCE
0.100000E-09 p022 HELMHOLTZ
0.100000E-09 p024 TOLREL
0.100000E-04 p025 TOLABS
1.00000E-06 p113 : ARNOLDI: arpack tolerance
Number of mesh element for entire domain is 1200.
The resolution in cylinder vicinity
On Thu, Jul 12, 2018 at 9:41 PM, <nek5000-users at lists.mcs.anl.gov> wrote:
> Hi;
> What is your tolerance for eigenvalue convergence? I'm unable to answer
> your question directly, as there can be number of problems. One of the
> obvious ones could be mesh resolution. You have pretty big mesh. What is
> the resolution in cylinder vicinity? What is the polynomial order? You have
> number of eigenvalues converged to machine accuracy and a few of the order
> 10**-4 in between. Those could be some spurious modes related to
> insufficient resolution. What is your Reynolds number?
> Regards
> Adam
>
>
> On 12/07/18 10:07, nek5000-users at lists.mcs.anl.gov wrote:
>
> Hi Neks
>
> I am running a 3D simulation for a flow over a cylinder. My domain
> size for simulation is 100Dx100D. where D is the diameter of a cylinder. We
> have obtained the base flow through SFD. The base flow is used to calculate
> the stability analysis through NEK5000 with the ARPACK library (Implemented
> by A. Peplinski).
>
> we have used the following parameters.....
>
> 90.0000 p111 : ARNOLDI: size of Krylov space
> 30.0000 p112 : ARNOLDI: number of eigenvectors
>
> We have run the Arnoldi with restart but we are not able to get the output
> file (eigenvalues.txt and egvext_cyl0.f0..) even after almost 20 restarts.
> Also, we tried to run with increasing the size of Krylov space but the
> eigenvalues are not converging.
>
> The log file shows no changes in converged ritz values after around 20-22
> values.
>
> The part of the log file is shown below...........
>
> Kindly, help me out and let me know where I am going wrong.....
>
> Alok Mishra
>
>
>
> ------------------------------------------------------------
> ---------------------------------------------------
>
> ARNOLDI: after 520 stepper phase
>
> _naup2: Corresponding B-norm of the residual
> --------------------------------------------
> 1 - 1: 6.623D-01
>
>
> _naup2: no. of "converged" Ritz values at this iter.
> ----------------------------------------------------
> 1 - 1: 22
>
>
> _naup2: NEV and NP are
> ----------------------
> 1 - 2: 52 128
>
>
> _naup2: "wanted" Ritz values -- real part
> -----------------------------------------
> 1 - 5: 9.905D-01 9.905D-01 9.854D-01 9.854D-01 9.855D-01
> 6 - 10: 9.855D-01 9.897D-01 9.897D-01 9.924D-01 9.930D-01
> 11 - 15: 9.930D-01 9.905D-01 9.905D-01 9.943D-01 9.943D-01
> 16 - 20: 9.938D-01 9.938D-01 9.948D-01 9.948D-01 9.949D-01
> 21 - 25: 9.949D-01 9.951D-01 9.958D-01 9.960D-01 9.962D-01
> 26 - 30: 9.962D-01 9.966D-01 9.970D-01 9.970D-01 9.969D-01
> 31 - 35: 9.969D-01 9.973D-01 9.974D-01 9.975D-01 9.976D-01
> 36 - 40: 9.976D-01 9.971D-01 9.971D-01 9.978D-01 9.979D-01
> 41 - 45: 9.979D-01 9.982D-01 9.982D-01 1.000D+00 9.908D-01
> 46 - 50: 9.908D-01 1.004D+00 1.004D+00 1.005D+00 1.005D+00
> 51 - 52: 1.006D+00 1.006D+00
>
>
> _naup2: "wanted" Ritz values -- imag part
> -----------------------------------------
> 1 - 5: 5.038D-02 -5.038D-02 -1.127D-01 1.127D-01 -1.119D-01
> 6 - 10: 1.119D-01 6.954D-02 -6.954D-02 0.000D+00 3.705D-03
> 11 - 15: -3.705D-03 -7.103D-02 7.103D-02 -9.233D-04 9.233D-04
> 16 - 20: 4.345D-02 -4.345D-02 6.799D-04 -6.799D-04 -1.821D-02
> 21 - 25: 1.821D-02 0.000D+00 0.000D+00 0.000D+00 -2.047D-03
> 26 - 30: 2.047D-03 0.000D+00 7.200D-05 -7.200D-05 2.386D-02
> 31 - 35: -2.386D-02 0.000D+00 0.000D+00 0.000D+00 -1.140D-04
> 36 - 40: 1.140D-04 3.125D-02 -3.125D-02 0.000D+00 -1.248D-04
> 41 - 45: 1.248D-04 -1.673D-03 1.673D-03 0.000D+00 -1.508D-01
> 46 - 50: 1.508D-01 -1.863D-02 1.863D-02 -2.109D-02 2.109D-02
> 51 - 52: -1.152D-02 1.152D-02
>
>
> _naup2: Ritz estimates of the "wanted" values
> ----------------------------------------------
> 1 - 5: 3.315D-02 3.315D-02 3.244D-05 3.244D-05 7.035D-05
> 6 - 10: 7.035D-05 6.072D-11 6.072D-11 1.314D-02 2.772D-06
> 11 - 15: 2.772D-06 6.796D-15 6.796D-15 9.719D-04 9.719D-04
> 16 - 20: 7.467D-17 7.467D-17 5.506D-04 5.506D-04 2.437D-16
> 21 - 25: 2.437D-16 2.977D-03 7.238D-04 6.054D-04 3.914D-11
> 26 - 30: 3.914D-11 1.827D-04 1.138D-04 1.138D-04 1.048D-16
> 31 - 35: 1.048D-16 1.198D-04 6.358D-05 3.013D-05 3.490D-07
> 36 - 40: 3.490D-07 9.960D-18 9.960D-18 1.340D-07 2.518D-10
> 41 - 45: 2.518D-10 1.827D-16 1.827D-16 1.781D-16 7.278D-17
> 46 - 50: 7.278D-17 0.000D+00 0.000D+00 0.000D+00 0.000D+00
> 51 - 52: 0.000D+00 0.000D+00
>
> Reached max iteration number; settingido=-2 for checkpointing.
> ARNOLDI:
> IDOARP = -2
> Writing checkpoint
> 0 40 OPEN: ARPm11800.f00002
> 0 40 OPEN: ARVm11800.f00002
>
> 40 2.0000E-01 done :: Write checkpoint
> file size = 621.E+00MB
> avg data-throughput = 624.1MB/s
> io-nodes = 1
>
>
> ARNOLDI: finalize
> Number of stepper cycles 520
> Time spent in ARNOLDI 60.3302609920502
> Average stepper phase time 10.9141681075096
> call outfld: ifpsco: F
>
> 40 2.0000E-01 Write checkpoint:
> 0 40 OPEN: m11800.f00001
>
> 40 2.0000E-01 done :: Write checkpoint
> file size = 4.0 MB
> avg data-throughput = 303.2MB/s
> io-nodes = 1
>
>
> end of time-step loop
>
>
>
>
>
>
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>
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--
Alok Mishra
Research Scholar
Computational Propulsion Lab
Aerospace Department IIT Kanpur
+91-8795844555
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