Research Fellow

Boris Diskin

Boris Diskin
757-325-6902
NIA

Research Interests

  • Numerical optimization and design methods
  • Analysis of unstructured-grid discretizations
  • Iterative solvers on structured/unstructured grids
  • Multiscale methods for modeling turbulent flows
  • Multiscale methods for simulations of advanced materials

Education

  • Ph.D. (1998), Applied Mathematics, The Weizmann Institute of Science, Israel
  • M.S. (1993), Applied Mathematics, The Weizmann Institute of Science, Israel
  • Combined B.S and M.S. (1988), Mathematics, Institute of Nuclear Power Engineering, Russia

Current Research

  • Multidisciplinary adjoint-based design optimization for aerodynamic applications. A comprehensive methodology for adjoint-based optimization of unsteady turbulent flows has recently been developed in FUN3D. The methodology supports both compressible and incompressible flows and is amenable to massively parallel computing environments. The approach provides a general framework for performing highly efficient and discretely consistent sensitivity analysis for problems involving arbitrary combinations of overset unstructured grids, which may be static, undergoing rigid or deforming motions, or any combination thereof. General parent-child motions are also accommodated, and the accuracy of the implementation is established using an independent verification based on a complex-variable approach. The current focus of this project is to extend the adjoint-based optimization capabilities to multidisciplinary design and optimization problems including aeroacoustics, aeroelasticity, sonic-boom mitigation, rotorcraft aeromechanics, wind-energy devises, unmanned air vehicles, and other areas. This research is conducted in collaborations with the FUN3D development group at NASA LaRC.
  • Adjoint-based sensitivity analysis for chaotic flows. Sensitivity analysis is widely used in design optimization, data assimilation, inverse problems and uncertainty quantification. High fidelity simulations of chaotic systems challenge existing techniques of extracting sensitivity information from simulations. Many traditional techniques for sensitivity analysis are designed for instantaneous quantities and fail for chaotic systems, due to the “butterfly effect” of chaotic dynamics. Corrupted by the large and unusable derivatives of the instantaneous quantities, traditional sensitivity analysis methods produce erroneous results for long-time averages of chaotic unsteady flows. In this project, new ideas to overcome the challenge of sensitivity analysis in chaotic simulations are investigated. In particular, the Least Squares Shadowing technique developed at MIT is studied in application to the turbulent flow sensitivity analysis. The shadowing condition replaces the initial condition, and forces similar design variables to follow similar trajectories that “shadow” each other. Such a similarity circumvents the “butterfly effect”, avoids chaotic divergence of trajectories of similar design variables, and allows the derivative computed by Least Squares Shadowing to approximate the derivative of the true long-term averaged objective function. This project is conducted in collaboration with MIT and NASA LaRC.
  • Efficient finite-volume discretizations on unstructured grids. This study aims at developing finite-volume discretizations suitable for accurate, robust, and efficient solutions for turbulent flows on general unstructured grids with a minimal set of constraints. In this project we analyze existing discretization methods and develop improved highly robust methods with low-complexity, verified accuracy, and efficient solvers. This research involves collaborations with computational groups at NASA LaRC, Boeing, and German Aerospace Center (DLR).
  • Iterative solvers on unstructured grids. This study is concerned with developing efficient single-grid and agglomeration multigrid solvers for iterative solutions of turbulent flows on general unstructured grids. Novel, efficient, robust methods for single-grid iterations, for grid agglomeration, and for quantitative analysis of multigrid solutions have been developed and implemented. Efficient iterative solvers have been demonstrated for inviscid, laminar, and turbulent flows for representative benchmark configurations. This study is conducted in collaboration with the computational groups at NASA LaRC, German Aerospace Center (DLR), and Japan Aerospace Center (JAXA).
  • Verification of CFD solutions for turbulent flows. This project aims at establishing accurate reference solutions for benchmark turbulent flow computations. Extensive grid refinement studies have been conducted for several 2D and 3D configurations suggested at Turbulence Modeling Resource (TMR) website developed and supported at NASA LaRC. This project support Numerical Analysis section at the TMR website. Detailed referenced solutions have been computed and posted for the NACA-0012 airfoil and a flat-plate configuration. The reference solutions are used to verify advanced CFD solvers with high-order mesh adaptation capabilities. Currently, reference solutions are computed for representative 3D configurations. This research involves collaborations with computational groups at NASA LaRC and German Aerospace Center (DLR).
  • Adjoint-based dynamic grid adaptation methodology. The objective of this research is to develop a new, efficient, dynamic grid-adaptation methodology applicable to turbulent flows in complex geometries across all speed regimes. The focus areas include adjoint-based error estimation methods for unsteady flows, dynamic adaptive grid redistribution methods, combined dynamic redistribution and local refinement methods, and algorithmic enhancements to reduce the storage requirements and computational cost associated with grid adaptation. This study is conducted in collaboration with NC A&T University.

Recent Publications

Journal Articles and Book Chapters

  1. Rallabhandi S. K., Nielsen E. J., and Diskin B., “Sonic Boom Mitigation through Aircraft Design and Adjoint Methodology,” AIAA Journal of Aircraft (2014), 51, pp. 502-510
  2. Nielsen E. J. and Diskin B., “Discrete Adjoint-Based Design Optimization of Unsteady Turbulent Flows on Dynamic Overset Unstructured Grids,” AIAA Journal (2013), 51(6), pp. 1355-1373
  3. Schwöppe A. and Diskin B., “Accuracy of the cell-centered grid metric in the TAU-code”, in “New Results in Numerical and Experimental Fluid Mechanics, in Notes on Numerical Fluid Mechanics and Multidisciplinary Design (2013), 121, pp. 429-437, Springer, NY
  4. Diskin B. and Thomas J. L., “Comparison of node-centered and cell-centered unstructured finite-volume discretizations: inviscid fluxes,” AIAA Journal (2011), 49(4), pp. 836-854 (doi: 10.2514/1.J050897).
  5. Thomas J. L., Diskin B., and Nishikawa H., “A critical study of agglomerated multigrid methods for diffusion on highly stretched grids,” Computers & Fluids (2011), 41(1), pp. 82-93 (doi: 10.1016/j.compfluid.2010.09.023).
  6. Diskin B., Thomas J. L., Nielsen E. J., Nishikawa H., and White J. A., “Comparison of node-centered and cell-centered unstructured finite-volume discretizations: viscous fluxes,” AIAA Journal (2010), 48(7), pp. 1326-1338.
  7. Nielsen E. J., Diskin B., and Yamaleev N. K., “Discrete adjoint-based design optimization of unsteady turbulent flows on dynamic unstructured grids,” AIAA Journal (2010), 48(6), pp. 1195-1206
  8. Nishikawa H., Diskin B., and Thomas J. L., “A critical study of agglomerated multigrid methods for diffusion,” AIAA Journal (2010), 48(4), pp. 839-847
  9. Yamaleev N. K., Diskin B., and Nielsen E. J., “Local-in-time adjoint-based methods for design optimization of unsteady flows,” Journal of Computational Physics (2010), 229(14), pp. 5394-5407
  10. Diskin B. and Thomas J. L. “Notes on accuracy of finite-volume discretization schemes on irregular grids,” Applied Numerical Mathematics (2010), 60(3), pp. 224-226
  11. Thomas J. L., Diskin B., and Ramsey C. L., “Towards Verification of Unstructured-Grid Solvers,” AIAA Journal (2008), 46(12), pp. 3070-3079
  12. Liao W., Diskin B., Peng Y., Luo L.-S. , “Textbook-efficiency multigrid solver for three-dimensional unsteady compressible Navier–Stokes equations,” Journal of Computational Physics (2008), 227(15), pp. 7160-7177

Referred Conference Articles

  1. Diskin B., Thomas J. L., Rumsey C. L., and Schwöppe A. “Grid Convergence for Turbulent Flows”, AIAA-2015-1746, Invited paper; SciTech-2015, Kissimmee, Florida, FL, Jan 2015
  2. Pandya, M. J., Diskin B., Thomas, J. L., and Frink N. T., “Improved Convergence and Robustness of USM3D Solutions on Mixed Element Grids”, AIAA-2015-1747, Invited paper; SciTech-2015, Kissimmee, Florida, FL, Jan 2015
  3. Diskin B. and Nishikawa H., “Evaluation of Multigrid Solutions for Turbulent Flows,” AIAA-2014-0082, Invited paper; SciTech-2014, National Harbor, MD, Jan 2014
  4. Nishikawa H., Diskin B., Thomas J. L., and Hammond D. H., “Recent Advances in Agglomerated Multigrid,” AIAA-2013-0863; 51st AIAA Aerospace Sciences Meeting, Grapevine, TX, Jan 2013
  5. Rallabhandi S. K., Nielsen E. J. and Diskin B., “Sonic Boom Mitigation through Aircraft Design and Adjoint Methodology,” AIAA-2012-3220, 42nd AIAA Fluid Dynamics Conference and Exhibit, New Orleans, LA, June 2012
  6. Nielsen E. J. and Diskin B., “Discrete Adjoint-Based Design Optimization of Unsteady Turbulent Flows on Dynamic Overset Unstructured Grids,” AIAA-2012-0554; 50th AIAA Aerospace Sciences Meeting, Nashville, TN, Jan 2012
  7. Diskin B. and Thomas J. L., “Mesh effects on accuracy of finite-volume discretization schemes,” invited paper, AIAA-2012-0609; 50th AIAA Aerospace Sciences Meeting, Nashville, TN, Jan 2012
  8. Diskin B. and Thomas J. L., “Convergence of defect-correction and multigrid iterations for inviscid flows,” AIAA-2011-3235; 20th AIAA Computational Fluid Dynamics Conference, Honolulu, Hawaii, June 2011
  9. Diskin B. and Yamaleev N. K., “Grid Adaptation Using Adjoint-Based Error Minimization,” AIAA-2011-3986; 20th AIAA Computational Fluid Dynamics Conference, Honolulu, Hawaii, June 2011
  10. Nishikawa H., Diskin B., and Thomas J. L., “Development and Application of Parallel Agglomerated Multigrid Method for Complex Geometries,” AIAA-2011-3232; 20th AIAA Computational Fluid Dynamics Conference, Honolulu, Hawaii, June 2011
  11. Schwöppe A. and Diskin B. “Genauigkeit der zell-zentrierten Netz-Metrik im TAU-Code” (in German), DLR STAB-Symposium, Berlin, Germany, Nov. 2010.
  12. Nishikawa H., Diskin B., and Thomas J. L., “Development and Application of Agglomerated Multigrid Methods for Complex Geometries,” AIAA-2010-4731; 40th AIAA Fluid Dynamics Conference and Exhibit, Chicago, IL, June 2010
  13. Yamaleev N. K., Diskin B., and Pathak K., “Error Minimization via Adjoint-Based Anisotropic Grid Adaptation” AIAA-2010-4436; 40th AIAA Fluid Dynamics Conference and Exhibit, Chicago, IL, June 2010
  14. Yamaleev N. K., Diskin B., and Pathak K., “Adjoint-Based Methodology for Anisotropic Mesh Adaptation,” 6th International Conference on Computational Fluid Dynamics, St. Petersburg, Russia, July 2010
  15. Yamaleev N. K., Diskin B., and Nielsen E. J., “Adjoint-based Methodology for Time-Dependent Optimization,” AIAA-2008-5857, 12th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, Victoria, BC, Canada, Sept 2008