Dear all, We should not be using the RadauMAlpha1Beta0 with Hex elements. This stands for Radau distribution at minus 1 (i.e. not including the point at +1) but it also involves the weight 0.25 (1-x)^alpha (1+x)^beta. So the Alpha1 means you are adding a weight function of 0.5(1-x)^alpha into the integral which is naturally part of the collapsed coordinate transform but this is not required in a Hex. So in theory one could use RadauMAlpha0Beta0 (not sure if this actually exists) but would be best just to use GaussLobattoLegendre in all directions. Cheers, Spencer. From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Boyang Xia <boyang.xia@kcl.ac.uk> Date: Monday, 15 May 2023 at 16:19 To: Ehsan Asgari <eh.asgari@gmail.com> Cc: nektar-users <nektar-users@imperial.ac.uk> Subject: Re: [Nektar-users] potential bug with detailed expansion Hi, GaussRadauMAlpha1Beta0 seems to be often used in Tri and Tet with Modified_B. I am not sure if it works with Modified_A(Ideally it should). So, what is your consideration of using GaussRadauMAlpha1Beta0 on the 3rd direction of hex? Are you using the incompressible Navier-Stokes solver and VCS? Then maybe you should follow chapter 11.1.1.6 to set different number of modes and points for velocity and pressure field. https://doc.nektar.info/userguide/5.3.0/user-guidese44.html Hope it helps, or correct me if it's wrong. Thanks, Boyang ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Ehsan Asgari <eh.asgari@gmail.com> Sent: Monday, May 15, 2023 11:53 To: Jacques Xing <jacques.xing@kcl.ac.uk> Cc: nektar-users <nektar-users@imperial.ac.uk> Subject: Re: [Nektar-users] potential bug with detailed expansion Hi Jacques I have a fully hex mesh. My perception is that for hex elements, modified_a should be used. Please correct me if I'm wrong. syavash On Mon, May 15, 2023 at 3:11 PM Jacques Xing <jacques.xing@kcl.ac.uk<mailto:jacques.xing@kcl.ac.uk>> wrote: Hi Ehsan I believe that you should use Modified_B basis from GaussRadauMAlpha1Beta0 quadrature. I am also assuming that you are using prism elements for the mesh? https://doc.nektar.info/userguide/5.0.0/user-guidese7.html Best, Jacques ________________________________ From: nektar-users-bounces@imperial.ac.uk<mailto:nektar-users-bounces@imperial.ac.uk> <nektar-users-bounces@imperial.ac.uk<mailto:nektar-users-bounces@imperial.ac.uk>> on behalf of Ehsan Asgari <eh.asgari@gmail.com<mailto:eh.asgari@gmail.com>> Sent: Monday, May 15, 2023 9:29 AM To: nektar-users <nektar-users@imperial.ac.uk<mailto:nektar-users@imperial.ac.uk>> Subject: [Nektar-users] potential bug with detailed expansion This email from eh.asgari@gmail.com<mailto:eh.asgari@gmail.com> originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Dear All, When I use a "Modfied" type for expansions everything works fine. But if I specify the expansions in detailed mode: <E COMPOSITE="C[30011]" BASISTYPE="Modified_A,Modified_A,Modified_A" NUMMODES="7,7,7" POINTSTYPE="GaussLobattoLegendre,GaussLobattoLegendre,GaussRadauMAlpha1Beta0" NUMPOINTS="8,8,7" FIELDS="u,v,w" /> <E COMPOSITE="C[30011]" BASISTYPE="Modified_A,Modified_A,Modified_A" NUMMODES="6,6,6" POINTSTYPE="GaussLobattoLegendre,GaussLobattoLegendre,GaussRadauMAlpha1Beta0" NUMPOINTS="7,7,6" FIELDS="p" /> Then I get a bunch of errors: [xxx518:29773] *** Process received signal *** [xxx518:29773] Signal: Segmentation fault (11) [xxx518:29773] Signal code: Address not mapped (1) [xxx518:29773] Failing at address: 0x27b2000 I have a fully hex mesh. Could you kindly point out if something is wrong with the way I specify the expansions? Kind regards syavash