Space-Time Window Reconstruction in Parallel High Performance Numeric Simulations. Application for CFD (PhD Thesis)
Alin Anton · Zenodo (CERN European Organization for Nuclear Research) · 2011
THESIS SUMMARY The PhD thesis was developed under the supervision of Prof.dr.ing. Vladimir-Ioan CREȚU and publicly defended before an international committee. The work has 10 chapters, exploring the current status and motivation, problem statement, research objectives and results.Computing power, especially in supercomputers, has increased so much that processing units produce a flood of intermediate numerical information that far exceeds the storage and transfer power of a normal user. When dealing with large numerical simulations we are also dealing with parallel computing, and the results obtained are broken down into subdomains of analysis on spatially discretized geometries. The simple visualization of the results involves repositioning the solution i.e. reassembling it in the original domain and only then downloading the information in compressed format. The merit of the PhD thesis is to demonstrate for the first time that it is possible to carve out from the CFD analysis domain an area of interest in space and time, called a "space-time window", starting from interpolating the initial conditions at a given time step and by extracting values of the fields computed at the edge of this window, for boundary conditions which in turn must respect the principle of fluid mass conservation. This is a radical approach for CFD where phenomena are non-stationary in time with various turbulence patterns, but which takes into account that often the area of interest is only a window in the calculated ensemble.The "space-time" window requires a recalculation of the interior fields based on the boundary information on a regular computer away from the computational centre, but allows storage and transfer of initial conditions by the usual means of correspondence. The capture of a vortex traversing the reconstruction window was demonstrated and the recalculated internal fields confirmed the global phenomenon simulated in the computing centre. A second method of obtaining the space-time window was highlighted by intercepting traffic between computational nodes and reusing it. In both cases a substantial reduction in the amount of information needed to deduce and reconstruct an HPC result was considered and achieved, opening a new paradigm and a new working style in the analysis of this type of complex CFD simulations.