Page 269 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Direct numerical simulations for liquid metal applications 239

nonuniform Cartesian grid (Angeli et al., 2015). A unit cell of a triangular lattice of
rods with a pitch-to-diameter ratio P/D ¼ 1.4 is considered as the reference geometry.
A Prandtl number Pr ¼ 0.031 is chosen as the working fluid. A friction Reynolds num-
5
ber Re τ ¼ 550 and a Rayleigh number value of Ra¼ 5 10 were imposed, resulting
in a bulk Reynolds number of about Re b ¼ 8600.
Fig. 6.1.1.9 shows the overall structure of the flow in a subchannel. Statistics were
computed on a unit flow cell corresponding to one-sixth of the base subchannel. Con-
tours of the average streamwise velocity component u x and wall-bulk temperature

Fig. 6.1.1.9 Rod bundle DNS: (A) Primary flow cell on which statistics are computed
(highlighted in red) and its contour, together with the definition of local abscissa γ used for the
profiles. Contours of time-averaged (B) u x and (C) θ w θ, on the unit flow cell and
(D) streamlines of the mean secondary flow components.