User-Dependent CFD Predictions of a Backward-Facing Step Flow - Report to participating teams

摘要

The backward-facing step flow with an expansion ratio of 5 has been modelled by 19 teams without benchmark solution or experimental data. Different CFD codes, turbulence models, boundary conditions, numerical schemes and convergent criteria are adopted based on the participants’ own experience in CFD simulation. The predicted non-dimensional penetration lengths as a function of Reynolds number are diverse among different teams. Even when the same turbulence model or even the laminar model is used, the difference is still notable among the results from different users. We believe that it indicates the combined effects of multiple decisions based on users’ experience may cause significant difference in CFD “experiments”. This calls for a solid approach of CFD validation and uncertainty assessment in CFD “experiments”. A standard or guideline of using CFD and uncertainty assessment is needed to minimize the errors and uncertainties in the future.