Can we use Recurrence CFD (rCFD) in Urban Flow Modelling?
Sprache des Vortragstitels:
Pollutant transport involves extremely differing time scales, ranging from seconds (e.g. for the dynamics of local vortices) to minutes and hours (e.g. for the accumulation of pollutant concentration in an urban sub-region). Modelling such processes, necessitates a highly efficient numerical methodology covering the highly-dynamic background flow as well as superposed long-term processes.
Recurrence CFD (rCFD), aims at an efficient representation of long-term processes which slowly evolve on highly-dynamic pseudo-periodic flow fields. Historically, rCFD has been developed in the field of process-engineering and we now explore the possibility of transferring it to urban flow modelling.
In the framework of rCFD, short-term full CFD simulation deliver recurrence databases of the governing flow at different operating conditions. Based on statistical reasoning, rCFD then exploits these databases in order to either develop (i) generic flow fields or (ii) generic transport fields, which subsequently serve as basis for the long-term process under consideration. In case of unsteadily varying operating conditions, we interpolate between existing recurrence databases.
In applying rCFD to a set of single-phase and multiphase flows, we experienced a computational speed-up of two (flow-based rCFD) to four (transport-based rCFD) orders of magnitude. In many cases this dramatic speed-up allows for faster-than-real-time simulations, which run on the same high-resolution grid as the original full CFD simulation. Motivated by this dramatic computational speed-up, we incorporated such real-time rCFD simulations into process monitoring and control, by using real-time rCFD simulations as plant predictor.
In a final part of this presentation, I will present first preliminary results of applying rCFD to the ?cube with roof-stack? benchmark case from the wind-engineering community and discuss potential future risks and opportunities of using rCFD in urban flow modelling.