Re: [deal.II] Re: Thermoelastic Problem
On 5/24/19 2:46 AM, Muhammad Mashhood wrote: > Thank you for informative reply and posting this concern on the forum. I am > also interested in thermoelastic problem and new use of deal.ii. > My question is that other than the tutorial steps 26 & 18 or 20,21 & 22, is > there pre-developed application at "https://www.dealii.org/; for this field > of > study? None that immediately implements the thermoelastic problem. But there are of course many building blocks you can find in a variety of tutorial programs and code gallery programs. Best W. -- Wolfgang Bangerth email: bange...@colostate.edu www: http://www.math.colostate.edu/~bangerth/ -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/1c66e935-f866-a40e-b311-7e9239c7633a%40colostate.edu. For more options, visit https://groups.google.com/d/optout.
Re: [deal.II] Temperature osscilations for low thermal diffusivity materials
Thanks for sharing the observations Chinedu. So far I am keeping the source term off for a while i.e. not needed currently. I am sharing the result and description in the attachment. On Tuesday, May 28, 2019 at 8:15:14 AM UTC+2, Chinedu Nwaigwe wrote: > > Wolfang is right. Negligible values of diffusion or thermal coefficients > lead to a compete change in the physics of the problem. In that case if > there are source terms the solution might become negative and if there is > no source it will become steady. Things might get worse if advection term > is involved. > > > > > > > > On Mon, May 27, 2019, 21:59 Wolfgang Bangerth wrote: > >> On 5/27/19 11:01 AM, Muhammad Mashhood wrote: >> > I am working with deal.ii step-26 to implement >> temperature >> > dependent thermal diffusivity. Currently for thermal diffusivity values >> > >> > order of 1e-2 the results are quit satisfactory but if I use the low >> thermal >> > diffusivity values like the order of 1e-6 to 1e-3, I get temperature >> > oscillations (temperature going to -ve value even with all positive >> > temperature initial and boundary conditions in domain and at >> boundaries). >> > If anyone has faced the same issue in thermal conduction simulations or >> knows >> > the criteria to keep simulation stable in terms of thermal diffusivity, >> time >> > step and mesh size then kindly suggest and share the opinion. Thank you >> in >> > advance! >> >> In the limit of no thermal diffusivity, your equation ends up as an >> ordinary >> differential equation and that means that you lose stability in the H^1 >> norm >> -- in other words, you will get oscillations. That's just part of the >> nature >> of the equation. >> >> What is the situation you are trying to model that leads to such a small >> diffusivity? >> >> Best >> W. >> >> >> -- >> >> Wolfgang Bangerth email: bang...@colostate.edu >> >> www: http://www.math.colostate.edu/~bangerth/ >> >> -- >> The deal.II project is located at http://www.dealii.org/ >> For mailing list/forum options, see >> https://groups.google.com/d/forum/dealii?hl=en >> --- >> You received this message because you are subscribed to the Google Groups >> "deal.II User Group" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to dea...@googlegroups.com . >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/dealii/84cc645b-9b75-79ec-8c3b-53d428ab8fc8%40colostate.edu >> . >> For more options, visit https://groups.google.com/d/optout. >> > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/7b7f7a96-aa34-47ae-8abf-197708ebc41b%40googlegroups.com. For more options, visit https://groups.google.com/d/optout. detail Description: Binary data
Re: [deal.II] Temperature osscilations for low thermal diffusivity materials
Hi Prof. Wolfgang! Thank you for the response. Indeed the solution is quite reasonable and validated with analytical solution if diffusivity is kept bigger. Actually in my case I am using the metals and metallic alloys where the thermal diffusivity are of the range of 1e-5 to 1e-4 m^2/s (I wonder there might be an alternative way to simulate with these physical properties values). Just as a further explanation, the approach to vary the diffusivity is also in a way that it is calculated from U_old temperature vector and remains same for current time step. On Monday, May 27, 2019 at 10:58:59 PM UTC+2, Wolfgang Bangerth wrote: > > On 5/27/19 11:01 AM, Muhammad Mashhood wrote: > > I am working with deal.ii step-26 to implement > temperature > > dependent thermal diffusivity. Currently for thermal diffusivity values > > > > order of 1e-2 the results are quit satisfactory but if I use the low > thermal > > diffusivity values like the order of 1e-6 to 1e-3, I get temperature > > oscillations (temperature going to -ve value even with all positive > > temperature initial and boundary conditions in domain and at > boundaries). > > If anyone has faced the same issue in thermal conduction simulations or > knows > > the criteria to keep simulation stable in terms of thermal diffusivity, > time > > step and mesh size then kindly suggest and share the opinion. Thank you > in > > advance! > > In the limit of no thermal diffusivity, your equation ends up as an > ordinary > differential equation and that means that you lose stability in the H^1 > norm > -- in other words, you will get oscillations. That's just part of the > nature > of the equation. > > What is the situation you are trying to model that leads to such a small > diffusivity? > > Best > W. > > > -- > > Wolfgang Bangerth email: bang...@colostate.edu > > www: http://www.math.colostate.edu/~bangerth/ > > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/d85f0475-87d1-420e-930f-ad27e6eff6a7%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[deal.II] Thank you!
I would like to follow up on the announcement of this release by publicly saying again how much we appreciate the many contributions from those who have sent it code, bug reports, fixed grammar and typos, or have helped in any other way. Many thanks! The ChangeLog lists at least the following people to whom thanks are due (though I am certain that I am forgetting someone): Giovanni Alzetta, Mathias Anselmann, Daniel Appel, Alexander Blank, Vishal Boddu, Benjamin Brands, Pi-Yueh Chuang, T. Conrad Clevenger, Sambit Das, the Ginkgo developers, Stefano Dominici, Nivesh Dommaraju, Marc Fehling, Niklas Fehn, Isuru Fernando, Andreas Fink, Daniel Garcia-Sanchez, Rene Gassmöller, Alexander Grayver, Joshua Hanophy, Logan Harbour, Graham Harper, Daniel Jodlbauer, Stefan Kaessmair, Eldar Khattatov, Alexander Knieps, Uwe Köcher, Kurt Kremitzki, Dustin Kumor, Ross Kynch, Damien Lebrun-Grandie, Jonathan Matthews, Stefan Meggendorfer, Pratik Nayak, Lei Qiao, Ce Qin, Reza Rastak, Roland Richter, Alberto Sartori, Svenja Schoeder, Sebastian Stark, Antoni Vidal, Jiaxin Wang, Yuxiang Wang, Zhuoran Wang. Martin, on behalf of the whole deal.II developer team: Daniel Arndt, Wolfgang Bangerth, Denis Davydov, Timo Heister, Luca Heltai, Guido Kanschat, Martin Kronbichler, Matthias Maier, Jean-Paul Pelteret, Bruno Turcksin, and David Wells -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/5a8a2837-3c10-06aa-53ec-247b6e4735d3%40gmail.com. For more options, visit https://groups.google.com/d/optout.
[deal.II] deal.II version 9.1 released
Version 9.1.0 of deal.II, the object-oriented finite element library awarded the J. H. Wilkinson Prize for Numerical Software, has been released. It is available for free under an Open Source license from the deal.II homepage at https://www.dealii.org/ The major changes of this release are: - The support for automatic and symbolic differentiation within deal.II has been completely overhauled and significantly extended. The automatic differentiation facilities integrate a broad spectrum of functionality, including support in the evaluation of finite element shape functions (FEValues) and associated point and tensor data structures. Functionality from both the ADOL-C as well as Sacado library in various modes is included. For symbolic differentiation, new wrappers to the high-performance SymEngine library allow an alternative approach addressing the syntax levels of expressions to compute derivatives, rather than the algorithmic approach underlying automatic differentiations. - Full support for hp adaptivity in parallel computations. deal.II has had support for hp-adaptive methods since around 2005, but not yet in combination with MPI. In order to gain support for parallel hp adaptivity a number of algorithmic issues were addressed in this release. Details can be found in the release paper. - A new HDF5 interface has been added in order to leverage its capabilities in terms of high-performance I/O for large amount of data. The HDF5 interfaces in deal.II support read and write operations both in serial and with MPI. - GPU support was significantly extended for the current release: Added features include preconditioners for CUDAWrappers::SparseMatrix objects, support for MPI-parallel CUDA data structures, and support for constraints in the matrix-free framework (and thus also support for adaptively refined meshes). - Four new tutorial programs have been added, step-61 demonstrating an implementation of the so-called weak Galerkin method, step-62 solving the elastic wave equation with perfectly matched layers to calculate the resonance frequency and bandgap of photonic crystals, step-63 on block and point smoothers for geometric multigrid in the context of convection-diffusion problems, and step-64 implementing a Helmholtz solver with matrix-free methods running on GPUs. Furthermore, a new code gallery program solving a Bayesian inverse problem has been added. - The release contains performance improvements and bug fixes of the matrix-free framework and related geometric multigrid solvers. In particular, the implementation of the Chebyshev iteration, an often used smoother in the matrix-free context, has been revised to reduce vector accesses. Altogether, matrix-free multigrid solvers run up to 15% faster than in the previous version. - Various variants of geometric multigrid solvers and matrix-free implementations were run on up to 304,128 MPI ranks during the acceptance phase of the SuperMUC-NG supercomputer, verifying the scalability of our implementations to this scale. Some geometric multigrid data structures were revised to avoid bottlenecks showing up with more than 100k ranks. - The FE_BernardiRaugel class implements the non-standard Bernardi-Raugel element that can be used to construct a stable velocity-pressure pair for the Stokes equation. The Bernardi-Raugel element is an enriched version of the Q_1^d element with added bubble functions on each edge (in 2d) or face (in 3d). It addresses the fact that the Q_1^d - Q_0 combination is not inf-sup stable (requiring a larger velocity space), and that the Q_2^d - Q_1 combination is stable but sub-optimal since the velocity space is too large relative to the pressure space to provide additional accuracy commensurate with the cost of the large number of velocity unknowns. The Bernardi-Raugel space is intermediate to the Q_1^d and Q_2^d spaces. - The FE_NedelecSZ class is a new implementation of the Nédélec element on quadrilaterals and hexahedra. It overcomes the sign conflict issues present in traditional Nédélec elements that arise from the edge and face parameterizations used in the basis functions. Therefore, this element should provide consistent results for general quadrilateral and hexahedral elements for which the relative orientations of edges and faces (as seen from all adjacent cells) are often difficult to establish. - A new class ParsedConvergenceTable has been introduced. The class simplifies the construction of convergence tables, reading the options for the generation of the table from a parameter file. It provides a series of methods that can be used to compute the error given a reference exact solution, or the difference between two numerical solutions, or any other
Re: [deal.II] Temperature osscilations for low thermal diffusivity materials
Wolfang is right. Negligible values of diffusion or thermal coefficients lead to a compete change in the physics of the problem. In that case if there are source terms the solution might become negative and if there is no source it will become steady. Things might get worse if advection term is involved. On Mon, May 27, 2019, 21:59 Wolfgang Bangerth On 5/27/19 11:01 AM, Muhammad Mashhood wrote: > > I am working with deal.ii step-26 to implement > temperature > > dependent thermal diffusivity. Currently for thermal diffusivity values > > > > order of 1e-2 the results are quit satisfactory but if I use the low > thermal > > diffusivity values like the order of 1e-6 to 1e-3, I get temperature > > oscillations (temperature going to -ve value even with all positive > > temperature initial and boundary conditions in domain and at boundaries). > > If anyone has faced the same issue in thermal conduction simulations or > knows > > the criteria to keep simulation stable in terms of thermal diffusivity, > time > > step and mesh size then kindly suggest and share the opinion. Thank you > in > > advance! > > In the limit of no thermal diffusivity, your equation ends up as an > ordinary > differential equation and that means that you lose stability in the H^1 > norm > -- in other words, you will get oscillations. That's just part of the > nature > of the equation. > > What is the situation you are trying to model that leads to such a small > diffusivity? > > Best > W. > > > -- > > Wolfgang Bangerth email: bange...@colostate.edu > www: http://www.math.colostate.edu/~bangerth/ > > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to dealii+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/dealii/84cc645b-9b75-79ec-8c3b-53d428ab8fc8%40colostate.edu > . > For more options, visit https://groups.google.com/d/optout. > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/CAAUzbWMfZNUO1Fs2uWx_%3DOfz_6PR05%3DtGgUtEu%2Bvj4q4yibjNw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
