This paper presents different CFD-simu
lations on f
lows which are re
levant for nuc
lear reactor safety using a new mode
ling approach for the interfacia
l drag at free surfaces. The deve
loped drag coefficient mode
l was imp
lemented together with the A
lgebraic Interfacia
l Area Density (AIAD) mode
l () into the three-dimensiona
l (3-D) computationa
l f
luid dynamics (CFD) code ANSYS-CFX. The app
lications considered inc
lude the prediction of counter-current f
low
limitations (CCFL) in a PWR hot
leg, the deve
lopment of hydrau
lic jump during the air¨Cwater co-current f
low in a horizonta
l channe
l, and pressurized therma
l shock (PTS) phenomena in a PWR co
ld
leg and downcomer. For the mode
ling of these tasks, an Eu
ler¨CEu
ler approach was used. This approach a
llows the use of different mode
ls depending on the
loca
l morpho
logy. In the frame of an Eu
ler¨CEu
ler simu
lation, the
loca
l morpho
logy of the phases has to be considered in the drag mode
l.
To demonstrate the feasibility of the present approach, the computed main parameters of each case were compared with experimental data. It is shown that the CFD calculations agree well with the experimental data. This indicates that the AIAD model combined with new drag force modeling is a promising way to simulate the phenomena in frame of the Euler¨CEuler approach. Moreover the further validation of the model by including mass transfer effects should be carried out.