A. Tapucu et al., THE EFFECT OF TURBULENT MIXING MODELS ON THE PREDICTIONS OF SUBCHANNEL CODES, Nuclear Engineering and Design, 149(1-3), 1994, pp. 221-231
In this paper, the predictions of the COBRA-IV and ASSERT-4 subchannel
codes have been compared with experimental data on void fraction, mas
s flow rate, and pressure drop obtained for two interconnected subchan
nels. COBRA-IV is based on a one-dimensional separated flow model with
the turbulent intersubchannel mixing formulated as an extension of th
e single-phase mixing model, i.e. fluctuating equal mass exchange. ASS
ERT-4 is based on a drift flux model with the turbulent mixing modelle
d by assuming an exchange of equal volumes with different densities th
us allowing a net fluctuating transverse mass flux from one subchannel
to the other. This feature is implemented in the constitutive relatio
nship for the relative velocity required by the conservation equations
. It is observed that the predictions of ASSERT-4 follow the experimen
tal trends better than COBRA-IV; therefore the approach of equal volum
e exchange constitutes an improvement over that of the equal mass exch
ange.