## geopdes-users

 [Geopdes-users] Order of DoF in the 3D elesticity From: Marco Brino - 2013-01-14 09:41:18 ```Hi all, I'm trying to build Matlab IGA own codes, just for having full knowledge and control of the relative routines. Obviously I use GeoPDEs as a reference for benchmark and results. In particular, I have a 3D hollow cylinder, and I'm trying to compute its modal analysis. I obtained strange results so i tried to compare my stiffness matrix with the one calculated by GeoPDEs. The layout of the matrices appears very different, and this could be related to the order of the DoF are listed. In my code, they are: - u_1x - u_1y - u_1z - u_2x - u_2y - u_2z - ... Which is the order of the DoF in the e lasticity package of GeoPDEs? Thank you very much for the help! Kindest regards, Marco -- Marco Brino Politecnico di Torino - DIGEP Corso Duca degli Abruzzi, 24 I-10129 Torino, Italy +39 011 090 7205 +39 393 554 4537 marco.brino@... ```
 Re: [Geopdes-users] Order of DoF in the 3D elesticity From: Rafael Vázquez - 2013-01-14 11:27:58 ```Dear Marco, in GeoPDEs_elasticity the dofs for a vector component are listed consecutively: assume that you have N dofs for the scalar problem, you will have 3*N for the elasticity problem. The dofs for the first component are 1:N, for the second they are N+1:2*N, and for the third 2*N+1:3*N. I'm not sure to have understood correctly your ordering, but if your code is implemented in a coherent way, this should not give any error. By the way, are you modelling the whole cylinder without symmetry? Because a possible source of error is what you do at the boundaries. Notice that when you apply the parametrization, two of the boundaries of the square collapse into a single internal edge. You will have to set that the dofs of both sides are the same, similar to what is done in multipatch. This topic was already discussed in the mailing list. Regards, Rafa > Hi all, > > I'm trying to build Matlab IGA own codes, just for having full knowledge > and control of the relative routines. Obviously I use GeoPDEs as a > reference for benchmark and results. > > In particular, I have a 3D hollow cylinder, and I'm trying to compute > its modal analysis. I obtained strange results so i tried to compare my > stiffness matrix with the one calculated by GeoPDEs. > > The layout of the matrices appears very different, and this could be > related to the order of the DoF are listed. > > In my code, they are: > - u_1x > - u_1y > - u_1z > - u_2x > - u_2y > - u_2z > - ... > > Which is the order of the DoF in the e lasticity package of GeoPDEs? > > Thank you very much for the help! > > Kindest regards, > Marco > > -- > Marco Brino > Politecnico di Torino - DIGEP > Corso Duca degli Abruzzi, 24 > I-10129 Torino, Italy > +39 011 090 7205 > +39 393 554 4537 > marco.brino@... > > > ------------------------------------------------------------------------------ > Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, > MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current > with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft > MVPs and experts. SALE \$99.99 this month only -- learn more at: > http://p.sf.net/sfu/learnmore_122412 > _______________________________________________ > Geopdes-users mailing list > Geopdes-users@... > https://lists.sourceforge.net/lists/listinfo/geopdes-users > ```
 Re: [Geopdes-users] Order of DoF in the 3D elesticity From: Marco Brino - 2013-01-14 11:30:20 ```Thank you Rafa, so you list the DoF by components, as I guessed. I know about the boundaries, and actually I have the problem of the incoherence of results AFTER I apply the symmetry. To do it, I do the same that in FEM is done with RBE2. Anyway, I was comparing both the versions with and without the glued boundaries. Thank you very much, I will try to fit with your listing order. Kindest regards, Marco On 14/01/2013 12:06, Rafael Vázquez wrote: > Dear Marco, > in GeoPDEs_elasticity the dofs for a vector component are listed > consecutively: assume that you have N dofs for the scalar problem, you > will have 3*N for the elasticity problem. The dofs for the first component > are 1:N, for the second they are N+1:2*N, and for the third 2*N+1:3*N. I'm > not sure to have understood correctly your ordering, but if your code is > implemented in a coherent way, this should not give any error. > > By the way, are you modelling the whole cylinder without symmetry? Because > a possible source of error is what you do at the boundaries. Notice that > when you apply the parametrization, two of the boundaries of the square > collapse into a single internal edge. You will have to set that the dofs > of both sides are the same, similar to what is done in multipatch. This > topic was already discussed in the mailing list. > > Regards, > Rafa > >> Hi all, >> >> I'm trying to build Matlab IGA own codes, just for having full knowledge >> and control of the relative routines. Obviously I use GeoPDEs as a >> reference for benchmark and results. >> >> In particular, I have a 3D hollow cylinder, and I'm trying to compute >> its modal analysis. I obtained strange results so i tried to compare my >> stiffness matrix with the one calculated by GeoPDEs. >> >> The layout of the matrices appears very different, and this could be >> related to the order of the DoF are listed. >> >> In my code, they are: >> - u_1x >> - u_1y >> - u_1z >> - u_2x >> - u_2y >> - u_2z >> - ... >> >> Which is the order of the DoF in the e lasticity package of GeoPDEs? >> >> Thank you very much for the help! >> >> Kindest regards, >> Marco >> >> -- >> Marco Brino >> Politecnico di Torino - DIGEP >> Corso Duca degli Abruzzi, 24 >> I-10129 Torino, Italy >> +39 011 090 7205 >> +39 393 554 4537 >> marco.brino@... >> >> >> ------------------------------------------------------------------------------ >> Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, >> MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current >> with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft >> MVPs and experts. SALE \$99.99 this month only -- learn more at: >> http://p.sf.net/sfu/learnmore_122412 >> _______________________________________________ >> Geopdes-users mailing list >> Geopdes-users@... >> https://lists.sourceforge.net/lists/listinfo/geopdes-users >> > -- Marco Brino Politecnico di Torino - DIGEP Corso Duca degli Abruzzi, 24 I-10129 Torino, Italy +39 011 090 7205 +39 393 554 4537 marco.brino@... ```