[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 05:09:40 CDT 2018
Hi Adam,
Thanks for your reply.
Tolerance for the different parameter taken for the case is shown below
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 is 32x10 (for the domain 2Dx2D over
cylinder )and we have resolved the boundary with y+ =3 for Re=50.
And the order of the polynomial is 5.
Hope to get your reply soon....
Regards
Alok
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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--
Alok Mishra
Research Scholar
Computational Propulsion Lab
Aerospace Department IIT Kanpur
+91-8795844555
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