Computational Physics Unit (CPU)

Members

• Head of Unit: Jan Nordström
• Former PhD students: Sofia Eriksson, Jens Berg, Per Pettersson
• Present PhD students: Samira Nikkar, Tomas Lundquist, Ossian O'Reilly, Hannes Frennander, Cristina La Cognata, Viktor Linders, Markus Wahlsten
• Post Doc: Marco Kupiainen

Ambition

• To develop mathematically based and provable convergent methods for solving time-dependent partial differential equations governing physical processes.

Main activities

• High Order Finite Difference Methods (FDM): We have developed summation-by-parts operators and penalty techniques for boundary and interface conditions. We have applied FDM to demanding problems in fluid mechanics and wave propagation.

  High speed separated flow including shocklets Colaborator Flow Research Unit, University of the Witwatersrand.

  Earthquake simulation related to Japananese tsunami Colaborator Department of Geophysics, Stanford University

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• Finite Volume Methods (FVM): We have reused the framework for the high order finite difference methods and derived summation-by-parts operators for first and second derivatives as well as suitable artificial dissipation operators.

  Unstructured mesh around high lift configuration Colaborator FOI, Swedish Defence Research Agency

  Flow in the nose region of a Naca0012 wing profile Colaborator FOI, Swedish Defence Research Agency

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• Numerical Coupling: We combine the advantages of FDM and FVM in an efficient and stable way. This numerical technique has been used in both aerodynamics (the Euler equations) and wave propagation (elastic wave equations) problems.

  Unstructured/structured mesh around rods Colaborator CTR, Center for Turbulence Research at Stanford University

  Unstructured/structured mesh around Landers fault Colaborator Department of Geophysics, Stanford University

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• Multi Physics Coupling: We develop well-posed and stable numerical coupling procedures for multiple equations sets. Lately we have considered the Navier-Stokes and the heat equation, fluid structure interaction and the elastic wave equation with friction laws.

  FSI, low accuracy misses eigenfrequency Colaborator Department of Information Technology, Uppsala University

  Conjugate heat transfer between air and gold Colaborator Department of Information Technology, Uppsala University

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• Boundary Conditions: We analyze existing techniques and derive new formulations. Lately we have focused on solid wall boundary conditions for the Navier-Stokes equations.

  Navier-Stokes solution close to solid boundary Colaborator Department of Information Technology, Uppsala University

  Weak enforcement of solid wall boundary conditions Colaborator FOI, Swedish Defence Research Agency

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• Unceartainty Quantification (UQ): We take into account various kinds of uncertainties or stochastic variations related to aerodynamic problems. Typical examples include stochastic uncertainties in the geometry of a wing, the speed of the aircraft and the angle of attack.

  Unceartainty in density for the Sod test case, Haar-wavelets Colaborator Uncertainty Quantification (UQ) Laboratory at Stanford University

  Unceartainty in density for the Sod test case, exact solution Colaborator Uncertainty Quantification (UQ) Laboratory at Stanford University

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• Fluid Mechanics of Vortices: By using the energy method on the constant coefficient compressible Navier-Stokes equations we can show why vortices decay slowly in viscous flows.

  Velocity field in a vortex Colaborator Department of Information Technology, Uppsala University

  Energy deacy for different types of flowfields Colaborator Department of Information Technology, Uppsala University

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• Propagation of nerv signals in living tissue: By solving the cable equation in combination with the Hodgkin-Huxley's equations we can simulate the propagation of nerve signals in the dendric tree.

  Nerves and somas Colaborator Department of Aeronautics and Astronautics, Stanford University

  Sketch of a nerve connecting to a soma Colaborator Department of Aeronautics and Astronautics, Stanford University

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Colaborators

• The development above have been done in a collaboration with NASA Langley Research Center, Stanford University, University of the Witwatersrand (WITS) and the Council for Scientific and Industrial Research (CSIR) in South Africa, Uppsala University, Nanospace AB and the Swedish Defence Research Agency (FOI) in Sweden.