Turbulence-induced vibration of coaxial cylinders with impinging inlets

Pressure vessels submitted to turbulent flows are prone to fluid-structure interactions and vibrations. The design of a nuclear power plant comes along with the prediction of the large scale vibration pattern generated by turbulent flows exerted upon large areas of the core barrel containing the fuel assemblies. The present paper focuses on turbulent forcing in annular gaps with impinging inlets, in view of assessing the relevance of traditional models of reactor vessel studies and of improving future calculations. An analytical reference case is designed to test the pressure field homogeneity hypothesis of the literature models. Pressure fluctuations associated to the turbulent flow are measured in an experimental mock-up and calculated in CFD simulations, at a gap Reynolds number of 10⁵. The global flow pattern in the annular gap is first provided. The Power Spectrum Density of the pressure field and its convection and coherence parameters are obtained both experimentally and numerically. A fair agreement is found between the measurements and the simulations, and the flow pattern appears inhomogenous in large proportions, contrary to the traditional representation. Furthermore, the first mode of vibration of the inner cylinder is measured under turbulent forcing, and compared to the predictions of the simplified model and of CFD calculations: a fair agreement is observed. Finally, the literature model is revisited in the light of these findings, and some potential improvements are discussed.