Author: Adam Peplinski, KTH Royal Institute of Technology

In our previous blog post we shortly presented implementation of h-type Adaptive Mesh Refinement (AMR) scheme in the Spectral Element Method code Nek5000. At that point only steady state calculation of the nonlinear Navier-Stokes equations were supported. We continue this work extending our implementation to the time dependent problems focusing mostly on a robust parallel preconditioning strategy for the pressure equation, which for the unsteady incompressible flows is the linear sub-problem associated with the divergence-free constraint and can become very ill-conditioned.

Author: Jean-Eloi W. Lombard, Imperial College London

Building on our February 16th post, we at McLaren have been working towards the first comparison between high-order simulations computed with Nektar++ (Cantwell 2016) of the McLaren Front-Wing and PIV data.

Authors: Dr. Christian Jacobs, University of Southampton; Niclas Jansson, KTH Royal Institute of Technology

ParCFD mini-symposium: Towards Exascale in High-Order Computational Fluid Dynamics

  • "High-Fidelity Road Car & Full-Aircraft Simulations using OpenFOAM on ARCHER - Perspectives On The Need For Exa-Scale" - N. Ashton
  • "Incorporating complex physics in the Nek5000 code: reactive and multiphase flows"A. Tomboulides
  • "Towards Resilience at Exascale: Memoryconservative fault tolerance in Nektar++"C. Cantwell
  • "Future-proofing CFD codes against uncertain HPC architectures: experiences with OpenSBLI"N.D. Sandham
  • "Towards adaptive mesh refinement for the spectral element solver Nek5000" - A. Peplinksi

Author: Björn Dick, High Performance Computing Center Stuttgart - HLRS

Besides scalability, resiliency and I/O, the energy demand of HPC systems is a further obstacle on the path to exascale computing and hence also addressed by the ExaFLOW project. This is due to the fact that already the energy demand of current systems accounts for several million € per year. Furthermore, the infrastructure to provide such amounts of electric energy is expensive and not available at the centers these days. Last but not least, almost the entire electric energy is transferred to thermal energy, posing challenges with respect to heat dissipation.

Author: Dr. Christian Jacobs, University of Southampton

In simulations of fluid turbulence, small-scale structures must be sufficiently well resolved. A feature of under-resolved regions of flow is the appearance of grid-to-grid point oscillations, and such oscillations are often used to decide when/where grid refinement is required. Two new error indicators have recently been developed by SOTON as part of the ExaFLOW project, that permit the quantification of these features of under-resolution. These are both based on spectral techniques using small-scale Fourier transforms.