The characteristics of pulsatile turbulent flow in a 90° pipe bend with a radius ratio of Rc=4 were investigated experimentally. Experiments were conducted with a mean Reynolds number Reta=20000, Womersley numbers of α=10 and 30, and flow ratio of η=0.5. The axial and secondary flow velocities were measured by laser Doppler velocimetry in sections from upstream to downstream of the bend. The periodic changes in their distributions were investigated and the effects of α on their transitions along the bend axis were discussed. For a low α, the flow velocities exhibited periodical changes similar to a steady flow with instantaneous Re. However, with an increase in α, they changed abruptly near the bend exit and became more complex. In particular, the axial velocity distribution at the maximum flow rate exhibited a peculiar change in the latter half of the bend, changing to a depressed shape with two maxima from a triangle, and the secondary flow velocity intensified significantly near the bend exit. Simultaneously, the turbulence intensity increased, and just behind the bend exit, the region with a large value extended to the central region.

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The study clarified the value of application to industrial turbomachinery with respect to multi-materialization using wire arc additive manufacturing (WAAM). First, the tensile strength was investigated by conducting tensile tests on multi-material tensile specimens made of nickel base alloy and stainless steel, which were fabricated using WAAM, under several heat treatment conditions. Then, an axial-flow impeller with multi-material blades made of nickel base alloy and stainless steel was fabricated using WAAM and machining. Furthermore, the fabricated impeller was attached to a centrifugal pump to demonstrate that it can function as an impeller for the pump. It was concluded from these results that the multi-material technology using WAAM is an option for the fabrication of industrial turbomachinery.

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