Abstract
Treating discontinuities at element boundaries is a significant problem in understanding high-order FEM simulation data since the physics used to model the simulation is often continuous. Recently, the family of SIAC filters, especially the L-SIAC filter, has been gaining popularity for its use in postprocessing. The computational math community, with its focus on improving the theoretical aspects of the SIAC filter, has applied the filter only on simple, fairly uniform unstructured meshes, where the largest element in the mesh is less than or equal to twice the smallest element. In many engineering applications, the unstructured meshes have varying orders of mesh resolution, but there is no literature for adapting the characteristic length of the SIAC filter to address these real-world simulation data. The central contribution of this paper is an algorithm used to calculate the characteristic length dynamically at any point in the mesh. We demonstrate that our approach has a lower error and is computationally faster than using maximum edge length over the mesh.


















Similar content being viewed by others
References
Lombard, J.-E.W., Moxey, D., Sherwin, S.J., Hoessler, J.F., Dhandapani, S., Taylor, M.J.: Implicit large-eddy simulation of a wingtip vortex. AIAA J. 54(2), 506–518 (2015)
Chooi, K., Comerford, A., Sherwin, S., Weinberg, P.: Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study. J. R. Soc. Interface 13(119), 20160234 (2016)
Docampo-Sánchez, J., Ryan, J.K., Mirzargar, M., Kirby, R.M.: Multi-dimensional filtering: reducing the dimension through rotation. SIAM J. Sci. Comput. 39(5), A2179–A2200 (2017)
Jallepalli, A., Docampo-Sánchez, J., Ryan, J.K., Haimes, R., Kirby, R.M.: On the treatment of field quantities and elemental continuity in fem solutions. IEEE Trans. Vis. Comput. Graph. 24(1), 903–912 (2017)
Mirzaee, H., King, J., Ryan, J.K., Kirby, R.M.: Smoothness-increasing accuracy-conserving filters for discontinuous Galerkin solutions over unstructured triangular meshes. SIAM J. Sci. Comput. 35(1), A212–A230 (2013)
Cantwell, C.D., Moxey, D., Comerford, A., Bolis, A., Rocco, G., Mengaldo, G., De Grazia, D., Yakovlev, S., Lombard, J.-E., Ekelschot, D., Jordi, B., Xu, H., Mohamied, Y., Eskilsson, C., Nelson, B., Vos, P., Biotto, C., Kirby, R.M., Sherwin, S.J.: Nektar++: an open-source spectral/hp element framework. Comput. Phys. Commun. 192, 205–219 (2015)
Cockburn, B., Luskin, M., Shu, C.-W., Süli, E.: Post-processing of Galerkin methods for hyperbolic problems. In: Karniadakis, G., Cockburn, B., Shu, C.-W. (eds.) Proceedings of the International Symposium on Discontinuous Galerkin Methods. Lecture Notes in Computational Science and Engineering, Newport, RI, 1999, vol. 11, pp. 291–300. Springer-Verlag, Berlin (1999)
Cockburn, B., Luskin, M., Shu, C.-W., Süli, E.: Enhanced accuracy by post-processing for finite element methods for hyperbolic equations. Math. Comput. 72(242), 577–606 (2003)
Ryan, J.K., Li, X., Kirby, R.M., Vuik, K.: One-sided position-dependent smoothness-increasing accuracy-conserving (SIAC) filtering over uniform and non-uniform meshes. J. Sci. Comput. 64(3), 773–817 (2015)
van Slingerland, P., Ryan, J.K., Vuik, C.: Position-dependent smoothness-increasing accuracy-conserving (SIAC) filtering for improving discontinuous Galerkin solutions. SIAM J. Sci. Comput. 33(2), 802–825 (2011)
Nguyen, D.-M., Peters, J.: Nonuniform discontinuous Galerkin filters via shift and scale. SIAM J. Numer. Anal. 54(3), 1401–1422 (2016)
Mirzargar, M., Jallepalli, A., Ryan, J.K., Kirby, R.M.: Hexagonal smoothness-increasing accuracy-conserving filtering. J. Sci. Comput. 73(2–3), 1072–1093 (2017)
Li, X., Ryan, J.K., Kirby, R.M., Vuik, C.: Smoothness-increasing accuracy-conserving (SIAC) filters for derivative approximations of discontinuous Galerkin (DG) solutions over nonuniform meshes and near boundaries. J. Comput. Appl. Math. 294, 275–296 (2016)
Mirzaee, H., Ji, L., Ryan, J.K., Kirby, R.M.: Smoothness-increasing accuracy-conserving (SIAC) postprocessing for discontinuous Galerkin solutions over structured triangular meshes. SIAM J. Numer. Anal. 49(5), 1899–1920 (2011)
Steffen, M., Curtis, S., Kirby, R.M., Ryan, J.K.: Investigation of smoothness-increasing accuracy-conserving filters for improving streamline integration through discontinuous fields. IEEE Trans. Vis. Comput. Graph. 14(3), 680–692 (2008)
Walfisch, D., Ryan, J.K., Kirby, R.M., Haimes, R.: One-sided smoothness-increasing accuracy-conserving filtering for enhanced streamline integration through discontinuous fields. J. Sci. Comput. 38(2), 164–184 (2009)
King, J., Mirzaee, H., Ryan, J.K., Kirby, R.M.: Smoothness-increasing accuracy-conserving (SIAC) filtering for discontinuous Galerkin solutions: improved errors versus higher-order accuracy. J. Sci. Comput. 53(1), 129–149 (2012)
Curtis, S., Kirby, R.M., Ryan, J.K., Shu, C.-W.: Postprocessing for the discontinuous Galerkin method over nonuniform meshes. SIAM J. Sci. Comput. 30(1), 272–289 (2007)
Li, X.: Smoothness-Increasing Accuracy-Conserving Filters for Discontinuous Galerkin Methods: Challenging the Assumptions of Symmetry and Uniformity (2015)
Demlow, A., Stevenson, R.: Convergence and quasi-optimality of an adaptive finite element method for controlling \({L}^2\) errors. Numer. Math. 117(2), 185–218 (2011)
Makridakis, C.G.: On the Babuška–Osborn approach to finite element analysis: \({L}^2\) estimates for unstructured meshes. Numer. Math. 139(4), 831–844 (2018)
Geuzaine, C., Remacle, J.-F.: Gmsh: a 3-D finite element mesh generator with built-in pre-and post-processing facilities. Int. J. Numer. Methods Eng. 79(11), 1309–1331 (2009)
Karniadakis, G.E., Sherwin, S.J.: Spectral/hp Element Methods for Computational Fluid Dynamics, 2nd edn. Oxford University Press, Oxford (2005)
Sidot, A.: Spectral/hp Element Methods Applied to Vortex Structures in a Low Incidence Delta Wing Wake Compared to Experiments. M.S. thesis in Aeronautics, Imperial College London (2017)
Acknowledgements
The authors would like to thank in particular the reviewers for their valuable comments and insights; their comments very much helped us improve the paper. The authors thank Dr. Jennifer Ryan and Dr. Xiaozhou Li for their insights and recommendations. The authors also wish to thank Professor Spencer Sherwin (Imperial College London, UK), Mr. Alexandre Sidot, and the Nektar++ Group for the counter-rotating vortex data and helpful discussions. The authors acknowledge support from ARO W911NF-15-1-0222 (Program Manager Dr. Mike Coyle).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Jallepalli, A., Haimes, R. & Kirby, R.M. Adaptive Characteristic Length for L-SIAC Filtering of FEM Data. J Sci Comput 79, 542–563 (2019). https://doi.org/10.1007/s10915-018-0868-6
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10915-018-0868-6