## [Libmesh-users] Way to Explicitly Compute Nodal Data

 [Libmesh-users] Way to Explicitly Compute Nodal Data From: Yusuke Sakamoto - 2012-07-03 01:14:16 ```Is there a good way to explicitly compute the nodal data and save them? I use LinearImplicitSystem to solve the Stokes equation for velocities and pressure. I want to use the computed nodal velocities to explicitly compute the displacements at each node using Euler's method or higher order method. Also, I want to use the displacements and velocities to explicitly compute other physical parameters, such as deformation rate, for post-processing purpose. Right now, I explicitly compute and save them in NumericVector whose length is equal to the number of nodes and put them into the system using Syetem::add_vector. If I need the value inside a local element, I just interpolate them using shape functions. However, I think there is a more efficient way using ExplicitSystem or other classes. If I am doing something unnecessary, could you tell me a better way to do it? Is there any examples? Thanks, Yusuke ```

 [Libmesh-users] Way to Explicitly Compute Nodal Data From: Yusuke Sakamoto - 2012-07-03 01:14:16 ```Is there a good way to explicitly compute the nodal data and save them? I use LinearImplicitSystem to solve the Stokes equation for velocities and pressure. I want to use the computed nodal velocities to explicitly compute the displacements at each node using Euler's method or higher order method. Also, I want to use the displacements and velocities to explicitly compute other physical parameters, such as deformation rate, for post-processing purpose. Right now, I explicitly compute and save them in NumericVector whose length is equal to the number of nodes and put them into the system using Syetem::add_vector. If I need the value inside a local element, I just interpolate them using shape functions. However, I think there is a more efficient way using ExplicitSystem or other classes. If I am doing something unnecessary, could you tell me a better way to do it? Is there any examples? Thanks, Yusuke ```
 Re: [Libmesh-users] Way to Explicitly Compute Nodal Data From: Andrew E Slaughter - 2012-07-03 01:54:07 ```I asked a similar question a few weeks ago, the thread may help you: http://sourceforge.net/mailarchive/message.php?msg_id=29370944. On Mon, Jul 2, 2012 at 9:14 PM, Yusuke Sakamoto wrote: > Is there a good way to explicitly compute the nodal data and save them? > > I use LinearImplicitSystem to solve the Stokes equation for velocities > and pressure. I want to use the computed nodal velocities to explicitly > compute the displacements at each node using Euler's method or higher > order method. Also, I want to use the displacements and velocities to > explicitly compute other physical parameters, such as deformation rate, > for post-processing purpose. > > Right now, I explicitly compute and save them in NumericVector whose > length is equal to the number of nodes and put them into the system > using Syetem::add_vector. If I need the value inside a local element, I > just interpolate them using shape functions. However, I think there is a > more efficient way using ExplicitSystem or other classes. > > If I am doing something unnecessary, could you tell me a better way to > do it? Is there any examples? > > Thanks, > > Yusuke > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Libmesh-users mailing list > Libmesh-users@... > https://lists.sourceforge.net/lists/listinfo/libmesh-users > -- Andrew E. Slaughter, PhD andrew.e.slaughter@... Materials Process Design and Control Laboratory Sibley School of Mechanical and Aerospace Engineering 169 Frank H. T. Rhodes Hall Cornell University Ithaca, NY 14853-3801 (607) 229-1829 http://aeslaughter.github.com/ ```
 Re: [Libmesh-users] Way to Explicitly Compute Nodal Data From: Derek Gaston - 2012-07-03 04:31:09 ```(warning: I'm assuming you're using shape functions with nodal degrees of freedom. Always a dangerous thing to assume!) Use an ExplicitSystem. Loop over nodes. Use node.dof_number(sys_num, var_num, 0) to get the dof_number for each variable in both your LinearImplicitSystem and ExplicitSystem (passing in the right sys_num for each one). The "0" as the third argument will get the dof index for the first component for the variable... which if you are using a shape function with nodal degrees of freedom will be the "value" DoF. Now use those dof indices to index into the solution vector of your LinearImplicit system and pull out the values of your primary variables. Do your calculation and use the dof indices from the ExplicitSystem to index into the solution vector of the ExplicitSystem to set the output from your calculations. Good thing about using a system like this is that the values will automatically come out in your output file. Derek On Mon, Jul 2, 2012 at 7:14 PM, Yusuke Sakamoto wrote: > Is there a good way to explicitly compute the nodal data and save them? > > I use LinearImplicitSystem to solve the Stokes equation for velocities > and pressure. I want to use the computed nodal velocities to explicitly > compute the displacements at each node using Euler's method or higher > order method. Also, I want to use the displacements and velocities to > explicitly compute other physical parameters, such as deformation rate, > for post-processing purpose. > > Right now, I explicitly compute and save them in NumericVector whose > length is equal to the number of nodes and put them into the system > using Syetem::add_vector. If I need the value inside a local element, I > just interpolate them using shape functions. However, I think there is a > more efficient way using ExplicitSystem or other classes. > > If I am doing something unnecessary, could you tell me a better way to > do it? Is there any examples? > > Thanks, > > Yusuke > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Libmesh-users mailing list > Libmesh-users@... > https://lists.sourceforge.net/lists/listinfo/libmesh-users > ```