Classics in CFD

• R. Löhner, H. Antil, J.M. Gimenez, S. Idelsohn and E. Onate – A Deterministic Pathogen Transmission Model Based on High-Fidelity Physics; Comp. Meth. Appl. Mech. Eng. 114929 (2022). https://doi.org/10.48550/arXiv.2202.08718
  • First ever deterministic pathogen transmission model that combines computational fluid dynamics (inhalation, exhalation, propagation in air), computational crowd dynamics (movement of pedestrians) and medical data (coughing and sneezing frequency, intensity, etc.) in order to predict transmission rates in crowded environments. Key technological breakthroughs: scalable CFD and CCD solvers, interpolation algorithms and linkage to medical data.

• R. Löhner, C. Othmer, M. Mrosek, A. Figueroa and A. Degro – Overnight Industrial LES for External Car Aerodynamics; AIAA-2020-2031 (2020). https://doi.org/10.2514/6.2020-2031
  • And we got there. Key technological breakthrough: Fast and accurate Cartesian solver with embedded grid solver.

• R. Löhner – Towards Overcoming the LES Crisis; Int. J. of Computational Fluid Dynamics 33,3, 87-97 (2019). DOI: https://doi.org/10.1080/10618562.2019.1612052
  • Yes, after 20 years of waiting we are getting there.

• R. Löhner – Improved Error and Work Estimates for High Order Elements; Int. J. Num. Meth. Fluids 72, 11, 1207-1218 (2013).
  • Somewhat controversial; it will be interesting to see what happens when the dust settles and cooler heads prevail…

• R. Löhner and A. Corrigan – Semi-Automatic Porting if a General Fortran CFD Code to GPUs: The Difficult Modules; AIAA-11-3219 (2011).
  • First large-scale production CFD code (with more than a dozen different solvers, hundreds of physics modules and more than a million lines of code) to run completely and efficiently on GPUs; key technological breakthrough: Python-based Fortran to CUDA translator

• A. Corrigan and R. Löhner – Porting of FEFLO to Multi-GPU Clusters; AIAA-11-0948 (2011).

• A. Loseille and R. Löhner – Anisotropic Adaptive Simulations in Aerodynamics; AIAA-10-0169 (2010).
  • First CFD run to compute accurately the sonic boom for an airplane flying at 11km height all the way to the ground; key elements: 3-D Euler, adaptation via local mesh modification

• Löhner, J.D. Baum, E. Mestreau, D. Sharov, C. Charman and D. Pelessone – Adaptive Embedded Unstructured Grid Methods; Int. J. Num. Meth. Eng. 60, 641-660 (2004).
  • A key idea, born in desperation (like so many), opening the way to simple embedded methods, which are now being used extensively in many fields

• O. Soto and R. Löhner – On the Computation of Flow Sensitivities From Boundary Integrals; AIAA-04-0112 (2004). (pdf)
  • If the cost function is defined on the boundary, and only the boundary moves, why is the domain required ?

• R. Löhner – Moore’s Law and the Diminishing Importance of Parallel Computing; Expressions of the IACM 13, 6-8 (2003).
  • As scientists, we are called to describe impartially what we see

• R. Löhner and M. Galle – Minimization of Indirect Addressing for Edge-Based Field Solvers; AIAA-02-0967 (2002).
  • And they said it was impossible…

• R. Löhner, C. Sacco, E. Onate and S. Idelsohn – A Finite Point Method for Compressible Flow; Int. J. Num. Meth. Eng. 53, 1765-1779 (2002).
  • First general FPM code for compressible code, combining: Delaunay and approximation-matrix based local cloud generation, Riemann solvers, limiters, edge-based data structures, shared-memory parallelization

• R. Löhner and E. Onate – An Advancing Point Grid Generation Technique; Comm. Num. Meth. Eng. 14, 1097-1108 (1998).
  • First general point generation technique

• R. Löhner, C. Yang and E. Onate – Viscous Free Surface Hydrodynamics Using Unstructured Grids; Proc. 22nd Symp. Naval Hydrodynamics Washington, D.C., August (1998).
  • First detailed EULER/RANS flowfield around an armada of ships

• J.D. Baum, H. Luo and R. Löhner – The Numerical Simulation of Strongly Unsteady Flows With Hundreds of Moving Bodies; AIAA-98-0788 (1998).
  • Never before had there been a simulation of a flowfield interacting with over 500 free-flying, contacting bodies in 3D (and comparison to experimental data)

• H. Luo, J.D. Baum and R. Löhner – A Fast, Matrix-Free Implicit Method for Compressible Flows on Unstructured Grids; J. Comp. Phys. 146, 664-690 (1998).
  • The combination of GMRES (as core solver) and LU-SGS (as pre-conditioner) produced a very fast (parallel, vector) and robust (RANS) solver

• J.D. Baum, H. Luo and R. Löhner, C. Yang, D. Pelessone and C. Charman – A Coupled Fluid/Structure Modeling of Shock Interaction with a Truck; AIAA-96-0795 (1996).
  • Most complex real-life 3-D fluid-structure problem at the time

• J.D. Baum, H. Luo and R. Löhner – Numerical Simulation of Blast in the World Trade Center; AIAA-95-0085 (1995).
  • Most complex 3-D transient geometry at the time
  • First unstructured grid run in CFD to approach 20 Million elements

• R. deFainchtein, S.T. Zalesak, R. Löhner and D.S. Spicer – Finite Element Simulation of a Turbulent MHD System: Comparison to a Pseudo-Spectral Simulation; Comp.Phys.Comm. 86, 25-39 (1995).
  • First real-life comparison of spectral and FEM codes for turbulent flows

• A. Shostko and R. Löhner – Three-Dimensional Parallel Unstructured Grid Generation; Int.J.Num.Meth.Eng. 38, 905-925 (1995).
  • First 2-D and 3-D parallel unstructured grid generators

• J.D. Baum. H. Luo and R. Löhner – Numerical Simulation of a Blast Inside a Boeing 747; AIAA-93-3091 (1993).
  • Most complex 3-D transient geometry at the time
  • First unstructured grid run in CFD to approach 8 Million elements

• R. Löhner, J. Camberos and M. Merriam – Parallel Unstructured Grid Generation; Comp.Meth.Appl. Mech.Eng. 95, 343-357 (1992).

• R. Löhner and J.D. Baum – Adaptive H-Refinement on 3-D Unstructured Grids for Transient Problems; Int.J.Num.Meth.Fluids 14, 1407-1419 (1992).
  • First efficient FEM use of 3-D adaptive H-refinement for highly transient problems
  • Full vectorization/auto-tasking efficiency
  • Basis of production codes FEFLO74, FEFLO96

• J.D. Baum and R. Löhner – Numerical Simulation of Shock Interaction with a Modern Main Battlefield Tank; AIAA-91-1666 (1991).
  • Most complex 3-D transient geometry at the time
  • First run to demonstrate the enormous usefulness of adaptivity for 3-D transient problems
  • First unstructured grid run in CFD to approach 2 Million elements

• R. Löhner – Three-Dimensional Fluid-Structure Interaction Using a Finite Element Solver and Adaptive Remeshing; Computer Systems in Engineering 1, 2-4, 257-272 (1990).
  • First demonstration of 3-D adaptive remeshing for transient problems
  • Basis of production codes FEFLO52, FEFLO54, FEFLO96

• R. Löhner and J. Ambrosiano – A Vectorized Particle Tracer for Unstructured Grids; J.Comp.Phys. 91, 1, 22-31 (1990).
  • First demonstration of fast tracking for unstructured-grid PIC codes

• R. Löhner, P. Parikh and C. Gumbert – Some Algorithmic Problems of Plotting Codes for Unstructured Grids; AIAA-89-1981-CP (1989).
  • First demonstration of fast plotting package for large 3-D unstructured grids
  • Basis of plotting codes FEPLOT, FEPOST, VPLOT and NASA’s FAST

• R. Löhner – Adaptive H-Refinement on 3-D Unstructured Grids for Transient Problems; AIAA-89-0365 (1989).

• R. Löhner – An Adaptive Finite Element Solver for Transient Problems with Moving Bodies; Comp.Struct. 30, 303-317 (1988).
  • First demonstration of 2-D adaptive remeshing for transient problems

• R. Löhner and P. Parikh – Three-Dimensional Grid Generation by the Advancing Front Method; Int.J.Num.Meth. Fluids 8, 1135-1149 (1988).
  • The 3-D advancing front grid generation paper
  • Basis of production codes FRGEN3D and VGRID

• R. Löhner – Some Useful Data Structures for the Generation of Unstructured Grids; Comm.Appl.Num.Meth. 4, 123-135 (1988).
  • First demonstration of fast grid generation with the advancing front method

• R. Löhner, K. Morgan, J. Peraire and M. Vahdati – Finite Element Flux-Corrected Transport (FEM-FCT) for the Euler and Navier-Stokes Equations; Int.J.Num.Meth.Fluids 7, 1093-1109 (1987).
  • The FCT paper for FEMs/unstructured grids
  • Basis of production codes FEFLO27, FEFLO28, FEFLO44, FEFLO64, FEFLO74, FEFLO96

• R. Löhner – An Adaptive Finite Element Scheme for Transient Problems in CFD; Comp.Meth.Appl.Mech.Eng. 61, 323-338 (1987).
  • First efficient FEM use of 2-D adaptive H-refinement for highly transient problems
  • Full vectorization
  • Basis of production codes FEFLO27, FEFLO28, FEFLO64

• R. Löhner, K. Morgan, J. Peraire and O.C. Zienkiewicz – Finite Element Methods for High Speed Flows; AIAA-85-1531-CP (1985).
  • This paper put Finite Element Methods for CFD on the map