Dear Will, It’s true that very low level of divergence is more difficult to achieve with ACM than with methods that rely on a global Poisson solve because explicit smoothers are not as efficient for damping low frequency modes. However, it has other advantages e.g. it is (strong) scalable unlike many Poisson/implicit methods and it has been found to outperform projection based methods in hydroacoustic splitting approach.
The P-multigrid improves the low frequency error damping. Please note that PyFR v1.7.5 is available on Github which introduced P=0 smoothing which further improves the convergence, especially for the continuity equation. Moreover, we are actively developing the ACM solver and other acceleration techniques will be introduced in the next releases. What is the scale of your simulation? If you are running a very small 2D problem you may not see great speed-ups with the accelerator. It is hard for me the answer the the mass conservation tolerance question because it is case dependent. If you are simulating a real life problem that is Ma=0.0001, yes you should drive the continuity residual to a very low level. If you are simulating for instance low speed aerodynamics with Ma=0.1 it may be not as crucial. Regards, Niki On 8 Jan 2018, at 13:48, Will <holm...@gmail.com<mailto:holm...@gmail.com>> wrote: Dear developers, For AC method in incompressible flow simulation, although with the accelerator, it seems the convergence speed is quite low, if mass conservation under a certain tolerance would be achieved in each physical time step. Hence, I wonder whether the pseudo time step should achieve the tolerance in every physical time step regarding mass conservation, if all those time steps would be in post processing. Best regards, Will -- 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 pyfrmailinglist+unsubscr...@googlegroups.com<mailto:pyfrmailinglist+unsubscr...@googlegroups.com>. To post to this group, send email to pyfrmailinglist@googlegroups.com<mailto:pyfrmailinglist@googlegroups.com>. Visit this group at https://groups.google.com/group/pyfrmailinglist. For more options, visit 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 pyfrmailinglist+unsubscr...@googlegroups.com. To post to this group, send an email to pyfrmailinglist@googlegroups.com. Visit this group at https://groups.google.com/group/pyfrmailinglist. For more options, visit https://groups.google.com/d/optout.
