Abstract
The direct numerical simulation (DNS) is applied to fully-developed turbulent flows in both eccentric annulus and triangular pin bundles of infinite array configuration. The DNS for flows with Re_τ=770 in an eccentric annulus suggests that local laminarization starts to prevail in the narrow gap region. The DNS is carried out for turbulent flows, with different friction Reynolds numbers up to Re_τ=1,400, in a bundle with the pitch-to-diameter ratio (P/D) equal to 1.2, and for flows with Re_τ=400 in bundles of different P/D, i.e., 1.2, 1.1 and 1.05. Discussions are made on the influences of the subchannel pin wall and the gap spacing onto the turbulence characteristics and onto the distributions of mean axial velocity, secondary flow and wall shear stress, and the local laminarization phenomena in the narrow gap region.
