Hi Paul, I have simply used the ext_cyl.rea and .map files so I guess it is dirichlet boundary condition at the inlet (which I have set to zero in usrbc since I am looking at perturbations), periodic boundary conditions on the sides, no-slip condition on the wall of the cylinder and classical outflow condition at the outlet. I initially thought this could come from the fact I had been using a call to random_number to initialise vxp and vyp. I made sure to use dsavg to ensure that the velocity on each side of the interface between elements has the same value. It did not change anything. I also tried with a hand-made divergence-free perturbation. Did not changed anything either. I am kind of clueless, particularly because it works fine with all of my other cases. Attached are the files I am using if you want to peak a glance at them. Cheers, JC 2014-02-06 5:11 GMT+01:00 <[email protected]>:

Hi JC,

Are you trying to look at the perturbation from the steady cylinder base flow ?

Am curious about your boundary conditions (though I recognize that your bc set for the external cylinder flow shouldn't be too different from the boundary layer case)...

Just inquiring to get a better idea of what's going on.

Paul

On Wed, 5 Feb 2014, [email protected] wrote:

Hi Nek's,

...

I am trying to run a linearised DNS of the flow over a two-dimensional cylinder at Re=60 for illustration purposes using the ext_cyl example. I am however encountering some troubles... I have been able to compute the unstable steady equilibrium using a selective frequency damping approach without any trouble. However, it is quite a different story when it comes to the linearised DNS. Indeed, the perturbation velocity field blows up quite rapidly and I am not sure why. I have tried other flows (lid-driven cavity, boundary layer, ...) just to make sure I had no problem with my nek install and everything was running fine. I have also tried on three different computers to make sure it was not platform-dependent and it actually blew up every time. I have been using the linearised version of nek quite extensively for the past three years and but never had such problem.

Is there something I have missed there?

Thanks a lot, JC

-- Jean-Christophe Loiseau Homepage <https://sites.google.com/site/loiseaujc/>

_______________________________________________

Nek5000-users mailing list [email protected] https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users

-- Jean-Christophe Loiseau Homepage <https://sites.google.com/site/loiseaujc/>

Dear Paul, I am trying to modify a mesh of a given example (turJet) using pretex. After the stage of choosing a name for the session, I enter "1" and then "jet" for the name of previous session. At this stage the program crashes with a message: "Error reading parameters from file". Thanks in advance, Barak