Flow through pipe junctions produces unsteady vortex shedding processes that can generate acoustic pressures whose modal amplification contributes to structural fatigue. Such flow-induced vibration (FIV) is an enduring concern in nuclear power plants (NPPs) and has led to delays in extended power uprate licensing, produced strong fluctuating loads in piping, and contributed to cracks in low pressure turbine blades. Modern computational fluid dynamics (CFD) analysis can analyze FIV phenomena, but the practical challenges of setting up and adequately meshing multiple candidate designs continue to deter routine and reliable CFD-based FIV assessment. Recently, CFD solvers implemented on Cartesian grids and offering autonomous mesh generation about complex geometries have made significant strides in addressing these challenges. Here, the successful application of a CFD solver (CGE) used in combination with subscale testing to rectify FIV in NPP piping, is described. The article reviews the role of CFD in FIV analysis and design, summarizes the principal analysis components of CGE, outlines the 1/8th subscale testing program used in conjunction with CFD to assess FIV, and concludes with postinstallation assessments of the modification. The concepts contained here have helped address FIV in several NPPs resulting in significant reductions in operation & maintenance (O&M) costs.

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