UG–a flexible software toolbox for solving partial differential equations P Bastian, K Birken, K Johannsen, S Lang, N Neuß, H Rentz-Reichert, ... Computing and Visualization in Science 1 (1), 27-40, 1997 | 546 | 1997 |

The saltpool benchmark problem–numerical simulation of saltwater upconing in a porous medium K Johannsen, W Kinzelbach, S Oswald, G Wittum Advances in Water Resources 25 (3), 335-348, 2002 | 118 | 2002 |

On the time scales of nonlinear instability in miscible displacement porous media flow MT Elenius, K Johannsen Computational Geosciences 16 (4), 901-911, 2012 | 60 | 2012 |

A contribution to risk analysis for leakage through abandoned wells in geological CO2 storage A Kopp, PJ Binning, K Johannsen, R Helmig, H Class Advances in Water Resources 33 (8), 867-879, 2010 | 54 | 2010 |

On the validity of the Boussinesq approximation for the Elder problem K Johannsen Computational Geosciences 7 (3), 169-182, 2003 | 53 | 2003 |

Numerical simulation of three-dimensional saltwater–freshwater fingering instabilities observed in a porous medium K Johannsen, S Oswald, R Held, W Kinzelbach Advances in water resources 29 (11), 1690-1704, 2006 | 45 | 2006 |

A parallel software-platform for solving problems of partial differential equations using unstructured grids and adaptive multigrid methods P Bastian, K Birken, K Johannsen, S Lang, V Reichenberger, C Wieners, ... High Performance Computing in Science and Engineering’98, 326-339, 1999 | 40 | 1999 |

Parallel solution of partial differential equations with adaptive multigrid methods on unstructured grids P Bastian, K Birken, K Johannsen, S Lang, V Reichenberger, C Wieners, ... High Performance Computing in Science and Engineering’99, 496-508, 2000 | 36 | 2000 |

Modeling transverse dispersion and variable density flow in porous media HM Nick, R Schotting, M Gutierrez-Neri, K Johannsen Transport in porous media 78 (1), 11-35, 2009 | 30 | 2009 |

Robuste Mehrgitterverfahren für die Konvektions-Diffusions-Gleichung mit wirbelbehafteter Konvektion K Johannsen Springer-Verlag, 2000 | 18 | 2000 |

Density-dependent dispersion in heterogeneous porous media Part I: A numerical study AJ Landman, K Johannsen, R Schotting Advances in water resources 30 (12), 2467-2480, 2007 | 15 | 2007 |

The Elder problem—bifurcations and steady state solutions K Johannsen Developments in Water Science 47, 485-492, 2002 | 14 | 2002 |

Co2 trapping in sloping aquafiers: High resolution numerical simulations M Elenius, HA Tchelep, K Johannsen Convective mixing in geological carbon storage, 2010 | 13 | 2010 |

A symmetric smoother for the nonsymmetric interior penalty discontinuous Galerkin discretization K Johannsen ICES Report 5, 23, 2005 | 11 | 2005 |

Advances in high-performance computing: Multigrid methods for partial differential equations and its applications P Bastian, K Johannsen, S Lang, S Nägele, C Wieners, V Reichenberger, ... High performance computing in science and engineering 2000, 506-519, 2001 | 10 | 2001 |

The Elder Problem JW Elder, CT Simmons, HJ Diersch, P Frolkovič, E Holzbecher, ... Fluids 2 (1), 11, 2017 | 8 | 2017 |

Robust smoothers for convection-diffusion problems K Johannsen Preprint IWR, University of Heidelberg, Heidelberg, Germany, 1999 | 8 | 1999 |

An aligned 3D-finite-volume method for convection-diffusion problems K Johannsen Modeling and Computation in Environmental Sciences, 227-243, 1997 | 7 | 1997 |

High-accuracy simulation of density driven flow in porous media P Bastian, K Johannsen, S Lang, C Wieners, V Reichenberger, G Wittum High Performance Computing in Science and Engineering’01, 500-511, 2002 | 6 | 2002 |

Multigrid methods for NIPG K Johannsen ICES Report, 05-31, 2005 | 5 | 2005 |