Niki, You aren’t seeing this in Paraview (see attached screenshot)? Also, where is the cylinder diameter defined within the *.ini file for this case. Are you referring to your setup of the source terms?
Best Regards, Zach Davis Pointwise®, Inc. Sr. Engineer, Sales & Marketing 213 South Jennings Avenue Fort Worth, TX 76104-1107 E: [email protected] P: (817) 377-2807 x1202 F: (817) 377-2799 enc > On Mar 16, 2017, at 8:22 AM, Niki Loppi <[email protected]> wrote: > > Hi Zach, > > I tried running your case for couple of outputs and did not experience the > odd behaviour in your .vtu file (attachment). However, in your mesh the > dimensions are scaled differently. For instance, the cylinder diameter is > D=~285, while the values in the .ini file are specified for D=1 used in my > mesh. > Cheers, > > Niki > > On 15/03/17 20:27, Zach Davis wrote: >> Hi Niki, >> >> Thanks for the explanation. I’ll look into this method a bit further based >> on the paper reference you provided. Something seems to be amiss with >> solution files. I’ve attached the *.pyfrm *.vtu and *.ini files I have >> generated for this case; though, the mesh is one of my own creation. If >> someone could explain what’s happening with the *.vtu file based on the >> *.pyfrm mesh input, then that would be appreciated. >> >> Best Regards, >> >> >> >> Zach Davis >> Pointwise®, Inc. >> Sr. Engineer, Sales & Marketing >> 213 South Jennings Avenue >> Fort Worth, TX 76104-1107 >> >> E: [email protected] <mailto:[email protected]> >> P: (817) 377-2807 x1202 >> F: (817) 377-2799 >> enc >> >> >> >> >> >> >> >> >> >> >>> On Mar 15, 2017, at 8:42 AM, Niki Loppi <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> Hi Zach, >>> >>> AC stands for the method of artificial compressibility. Instead of relying >>> on a Poisson based projection, the system is driven towards a divergence >>> free state by introducing artificial pressure waves through the continuity >>> equation. The formulation preserves the hyperbolic nature of the system, >>> but destroys the time accuracy, which is then recovered with dual time >>> stepping. For the ac formulation you can refer to >>> >>> http://www.sciencedirect.com/science/article/pii/S0021999116001686 >>> <http://www.sciencedirect.com/science/article/pii/S0021999116001686> >>> The artificial compressibility factor ac-zeta is the coefficient of the >>> fluxes in the continuity equation. This results in characteristics >>> >>> V + c, V, V - c, >>> >>> where c = sqrt(V^2 + ac-zeta) is the pseudo speed of sound. Thus, in the >>> current implementation ac-zeta is the free parameter that is used to >>> downscale the speed of the pseudo-waves to globally reduce the pseudo >>> system stiffness. The parameter is something that one can experiment with, >>> typical values varying from 1.25 - 10 times the freestream velocity. >>> Currently, I am looking into making ac-zeta and pseudo-dt spatially and >>> temporally varying. >>> >>> The source terms specify a sponge region near the domain edges (|y|>5, >>> x<-5, x>25) to damp the initial pressure wave that is generated when the >>> simulation is started from scratch. Please note that the sponge turns off >>> at t=5 because of the (1 - tanh(1.5*(t - 5.0)))*0.5 coefficient. You can >>> see how the sponge works if you write the solution files before t=5. >>> The plugin [soln-plugin-pseudostats] is used to output the residual of the >>> pseudo time problem to monitor the divergence. The [soln-plugin-residual] >>> on the other hand computes the "residual" of two consecutive real time >>> steps. The [soln-plugin-fluidforce] plugin can be used with the ac systems. >>> >>> Coarsening the mesh and increasing the order is something that would be >>> beneficial, especially when using a polynomial multigrid for accelerating >>> the pseudo time problem. P-multigrid should be added in the next release. >>> >>> Thanks, >>> >>> Niki >>> >>> >>> >>> >>> On 14/03/17 23:37, Zach Davis wrote: >>>> Tuesday, 14 March 2017 >>>> >>>> >>>> >>>> Peter & Freddie, >>>> >>>> I believe the mesh export issue from Pointwise using the PyFR exporter has >>>> been resolved in PyFR 1.6. I still seem to have issues running using the >>>> OpenCL backend which persistently complains about an invalid workgroup >>>> size. It use to work at one point, but something has changed in the >>>> intervening releases which is causing problems for me at least. I’ve >>>> tried adjusting the values per Freddie’s guidance to no avail. He also >>>> suggested a tool that might be helpful in determining the appropriate >>>> workgroup size needed for my card. Unfortunately that tool seems to be >>>> NVIDIA card specific requiring installation of NVIDIA software that won’t >>>> run on my machine. I’m using an AMD card instead, and the tool won’t >>>> compile due to missing dependencies. It’s not a pressing matter, but just >>>> something that I thought you both might want to be aware of. >>>> >>>> Nikki, >>>> >>>> I’ve looked over your incompressible 2d-cylinder case, and I was wondering >>>> if you could elaborate a bit, or point me to some reference, about how you >>>> came up with the source terms you’re using in the input file. It also >>>> appears that the [soln-plugin-pseudostats] is used in place of the >>>> [soln-plugin-residual] namelist for incompressible cases—is that right? >>>> Does the [soln-plugin-fluidforce] namelist still work for the >>>> ac-navier-stokes solver? Another question if you don’t mind—what is this >>>> artificial compressibility factor, ac-zeta and why is value of 6.0 used? >>>> Oh, and what does the ac prefix stand for? Thanks! >>>> >>>> I think it would be interesting to see how coarse of a higher-order mesh >>>> could be made for this case while increasing the polynomial solution basis >>>> such that you essentially recover the linear mesh spacing in each element, >>>> and see if you could capture one or more vortices within a single element >>>> with any noticeable diffusion over time. >>>> >>>> Best Regards, >>>> >>>> >>>> >>>> Zach Davis >>>> Pointwise®, Inc. >>>> Sr. Engineer, Sales & Marketing >>>> 213 South Jennings Avenue >>>> Fort Worth, TX 76104-1107 >>>> >>>> E: [email protected] <mailto:[email protected]> >>>> P: (817) 377-2807 x1202 >>>> F: (817) 377-2799 >>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "PyFR Mailing List" group. >>>> To unsubscribe from this group and stop receiving emails from it, send an >>>> email to [email protected] >>>> <mailto:[email protected]>. >>>> To post to this group, send email to [email protected] >>>> <mailto:[email protected]>. >>>> Visit this group at https://groups.google.com/group/pyfrmailinglist >>>> <https://groups.google.com/group/pyfrmailinglist>. >>>> For more options, visit https://groups.google.com/d/optout >>>> <https://groups.google.com/d/optout>. >>> >>> -- >>> Niki Andreas Loppi MSc >>> Postgraduate Researcher >>> Department of Aeronautics >>> Imperial College London >>> South Kensington >>> London >>> SW7 2AZ >>> UK >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "PyFR Mailing List" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to [email protected] >>> <mailto:[email protected]>. >>> To post to this group, send email to [email protected] >>> <mailto:[email protected]>. >>> Visit this group at https://groups.google.com/group/pyfrmailinglist >>> <https://groups.google.com/group/pyfrmailinglist>. >>> For more options, visit https://groups.google.com/d/optout >>> <https://groups.google.com/d/optout>. >> > > > -- > You received this message because you are subscribed to the Google Groups > "PyFR Mailing List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/pyfrmailinglist > <https://groups.google.com/group/pyfrmailinglist>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. > <0.5cylinder.png> -- You received this message because you are subscribed to the Google Groups "PyFR Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. Visit this group at https://groups.google.com/group/pyfrmailinglist. For more options, visit https://groups.google.com/d/optout.
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