Flow over and through pipe junctions produces unsteady loads and vortex shedding processes that in turn generate acoustic pressures whose modal amplification can contribute to structural fatigue in piping systems.&nbsp; Such flow-induced vibration (FIV) is a long-standing concern in nuclear plants and, citing recent examples, have led to delays in extended power uprate licensing due to the complexities of assessing FIV effects on steam dryers in nuclear power plants, produced strong fluctuating loads in headers, requiring modifications and reinforcements, and been identified as a major contributor to cracks in the roots of low pressure turbine blades.&nbsp; Modern computational fluid dynamics (CFD) analysis offers a means to analyze FIV phenomena and help devise design changes to attenuate FIV amplitude.&nbsp; However, well documented technical difficulties associated with low Mach number acoustics modeling [1] and the practical challenges of setting up and adequately meshing multiple candidate designs remains a deterrent to more widespread and reliable CFD-based FIV assessment.To tackle these challenges work is ongoing to develop and incorporate modified flux evaluation methods that preserve the pressure-vorticity coupling in the low Mach number region.&nbsp; Simultaneously, advances have been made in Cartesian grid techniques to provide an autonomous mesh generation capability with minimal user involvement.&nbsp; Cartesian grids combine an octree-based hierarchical decomposition of the flow domain and polygon clipping procedures to develop a surface-conforming CFD mesh.&nbsp; Since the flow mesh resolution can be controlled independently from that of the surface grid, selective refinement and mesh convergence studies are simplified.The usefulness of a Cartesian grid for internal industrial flow is demonstrated for three recent applications .&nbsp; The first examines the 3D vortex shedding dynamics and attendant acoustic response arising in flow past a T-junction.&nbsp; It compares different flux evaluation methods designed to improve low Mach number acoustics and thereby generalizes the 2D work studies in [1].&nbsp; The second case predicts the head loss resulting from reverse flow over a stationary fan and demonstrates Cartesian grid-based flow modeling on a more complex geometry.&nbsp; The final case examines the unsteady flow though a header assembly known to produce unfavorable FIV.&nbsp; In this case, vortex shedding is the primary driver of the acoustic response and options for suppressing the vortex shedding process are assessed.&nbsp;1.&nbsp; Boschitsch, A., P. Danilov, and A. Bilanin. Low Mach Number Acoustics in Nuclear Piping Systems. in American Nuclear Society Annual Meeting 2018. 2018. Philadelphia, PA: ANS.

Flow Induced Vibration Analysis and Remediation Using a Cartesian Grid Flow Solver

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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