Stability evaluation of the rod in triangular array predicted by CFD

Stability boundaries of structures consisting of circular cylinder arrays in the cross-flow are different from case to case depending on geometrical and mechanical variations of the rod bundle layout as well as depending on nature of the flow field, requiring an individual set of experiments for each characteristic case. In this study, close-packed staggered rod bundle with a pitch-to-diameter ratio of 1.1 is analysed. Numerical modelling has been done to check the stability threshold (critical velocity) of a flexibly mounted rod in an otherwise fixed rods array. The computational domain consists of the rod array with 6 rows of five cylinders. The unsteady flow through triangular cylinder array has been simulated using two-dimensional URANS computations with an open source Computational Fluid Dynamics (CFD) code. The CFD calculations are coupled with the six degree-of-freedom rigid body motion solver with reduced degree-of-freedom. Results were compared with the analytically determined threshold values.