Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Plunging jets play an important role in nuclear reactor safety research. In the present paper the case of the strainer clogging issue is considered. Entrained air caused by a plunging jet has an influence of the liquid flow field and on the fibre transport in the sump. In the paper the amount of entrained air is given as an inlet boundary condition according to correlations in the literature and confirmed by own experiments. The influence of entrained air on the fibre deposition pattern at the bottom of a tank and on the mixing procedure for the case of temperature differences between jet and tank water are investigated by Computational Fluid Dynamics (CFD) calculations and compared to experiments.
The presented work is part of a joint research project performed in cooperation between the University of Applied Science Zittau/Görlitz and Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow in Zittau and the development of CFD models for its simulation in Rossendorf Whereas an overview and a description of the main concepts of this project are described by Krepper et al. 2008, 2009, the focus of the actual paper is directed on the different aspects of a jet.
The entrained air has a remarkably influence on the generation of swirls und therefore on the transport and deposition of fibres. At least qualitative conclusions concerning main effects, critical regions of fibre deposition and design improvements avoiding undesired fibre deposition can be drawn. The CFD simulation of the sump flow conditions during a real accident scenario over several 1000 seconds however will fail caused by the large computational effort.