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Seismic design and qualification of advanced reactors will rely heavily on the use of verified and validated numerical models capable of capturing the interaction of the vessel, its contained fluid, and the internal equipment: fluid‐structure interaction (FSI) analysis. Analytical solutions can be used for preliminary sizing and design of such vessels but their application is limited to simple geometries and boundary conditions, and small amplitude, translational (and rotational) inputs. To validate numerical models for seismic FSI analysis in finite element codes, a comprehensive set of experiments was performed on a liquid‐filled cylindrical vessel, using a 6 degree‐of‐freedom earthquake simulator. Results in terms of sloshing frequency, damping ratio in sloshing modes, and hydrodynamic responses (wave height, hydrodynamic pressure, base shear, and base moment) for multidirectional earthquake simulator inputs are reported and compared with analytical solutions for liquid‐filled vessels. The impact of seismic (base) isolation on hydrodynamic responses was studied using earthquake simulator inputs generated using a virtual isolation system. Data from the experiments are used to validate a numerical model of the fluid‐filled vessel using the Arbitrary Lagrangian Eulerian (ALE) solver in the commercial finite element program LS‐DYNA. Validation studies are presented for multidirectional seismic inputs, including rocking motions. Lagrangian modeling approaches using an elastic material formulation for the fluid are also investigated and their limitations and possible applications are identified. The results are broadly applicable to the seismic response of base supported, liquid‐filled vessels.

Numerical models capable of generating robust estimates of isolation-system and fluid-structure responses for multidirectional, high-intensity shaking will be required for analysis, design, and risk assessment of seismically isolated advanced reactors. None of the few studies to date on base-isolated, fluid-filled vessels have generated datasets suitable for formal validation of numerical models. Earthquake-simulator experiments on a fluid-filled, cylindrical vessel, base isolated using four single concave friction pendulum bearings (SFP isolators) were performed. The dataset was used to validate a numerical model for high intensity, multidirectional seismic inputs. Fluid and isolation-system responses obtained from analysis of the numerical model were in excellent agreement with experimental results. The numerical models and outcomes from the experiments are broadly applicable to base-isolated, fluid-filled vessels, regardless of industry sector.

The acoustic fluid-structure interaction (FSI) formulation is a practical numerical approach for the seismic analysis of fluid-filled tanks. However, there are no verification and validation studies reported in the literature that demonstrate the ability of an acoustic FSI numerical model to predict responses important to structural and mechanical design for intense translational and rotational earthquake inputs. Herein, an acoustic FSI formulation is implemented in the opensource Multiphysics Object-Oriented Simulation Environment (MOOSE), and is formally verified and validated using analytical solutions and code-to-code verification, and experimental data, respectively. The analytical solutions are for small amplitude, unidirectional seismic inputs. The code-to-code verification utilizes a previously verified and validated Arbitrary Lagrangian-Eulerian (ALE) numerical model in the commercial finite element code LS-DYNA. The validation studies utilize a comprehensive data set assembled from results of 3D earthquake-simulator tests of a fluid-filled vessel. The acoustic numerical model in MOOSE is verified and validated for hydrodynamic pressures and support reactions except for cases that involve significant convective response. For small amplitude inputs, numerically predicted wave heights match those of the analytical solutions. The numerical model is not verified and validated for wave height calculations under intense 3D seismic inputs. The run times for the acoustic FSI simulations in MOOSE are an order of magnitude, or more, shorter than for the corresponding ALE simulations in LS-DYNA. The utility of the MOOSE acoustic FSI implementation is demonstrated by seismic analysis of a building equipped with a fluid-filled, advanced nuclear reactor.

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