While it is known that rigid splitter plates play significant roles in flow control, the exactly roles of them in flow-induced vibration (FIV) has not been systematically investigated. This has motivated the present work to experimentally investigate the FIV of a cylinder equipped with an upstream rigid splitter plate (USP), a downstream plate (DSP) and symmetrically arranged splitter plates (SSP) in a water tunnel with Reynolds number of 1100-7700. The length of the plate is in a range of L^∗=0-3.6 (L∗ =L/D, L is the plate length, D is the cylinder diameter). The response characteristics, vortex evolution, fluid force and pressure fields are thoroughly analyzed. Both USP and DSP can succeed in oscillation mitigation and drag reduction. However, dramatic galloping is observed for DSP with L∗ = 0.4-2.2. The low pressure region forms near the downstream plate is beneficial for galloping. For USP, only vortex induced vibration (VIV) is found and the transition of response branches corresponds to the variation in oscillation frequency and phase jumps. However, the vortex mode transition from 2S to 2P disappears with long plate length. Flow visulization reveals that the upstream vortex induced by USP alters the downstream vortex shedding. Furthermore, a high pressure region forms near the tip of USP, yielding an obstructive force that suppresses the growing of oscillation. With the combination of USP and DSP, weak galloping is excited in a narrow range of L∗ = 1.0-1.8, and the linear increase is also broken due to the existence of USP.

The flow-induced vibration (FIV) of a cylinder cluster is often observed in subsea pipelines and marine risers. The motion of the cylinder clusters was often modeled as the equation of motion of a particle, which has ignored the torsion freedom. Hence, the answers to the following questions are still unavailable—what are the impacts of torsion on the FIV of a cylinder cluster? Does torsional freedom facilitate the development of new features in FIV? In the present work, the FIV of a two-tandem cylinder system was numerically studied under the consideration of torsional freedom. It was found that six well-defined regimes were formed in the FIV of the cylinder system with the increase in the reduced velocity. The formation of different regimes mainly occurred by the accouplement of two frequencies—the vortex shedding frequency and the natural frequency of the cylinder system. A quirky low frequency dominated the cross-flow vibration at some reduced velocities, significantly magnifying the cross-flow vibration and the torsional vibration. The two cylinders acted as two feet treading water alternatively, enabling the cylinder system to move further on one side at such low frequencies. The characteristics of the amplitudes and frequency responses vs U_r^* were qualitatively similar when the stiffness ratio k* was in the range of 10 ≤ k^* ≤ 50, where U_r^* was the torsional reduced velocity which was defined by the uniform velocity U divided torsional natural frequency f_rn and diameter of the cylinder D.

This study proposes an uncertainty quantification method based on deep neural networks and Catmull–Clark subdivision surfaces for vibroacoustic problems. The deep neural networks are utilized as a surrogate model to efficiently generate samples for stochastic analysis. The training data are obtained from numerical simulation by coupling the isogeometric finite element method and the isogeometric boundary element method. In the simulation, the geometric models are constructed with Catmull–Clark subdivision surfaces, and meantime, the physical fields are discretized with the same spline functions as used in geometric modelling. Multiple deep neural networks are trained to predict the sound pressure response for various parameters with different numbers and dimensions in vibroacoustic problems. Numerical examples are provided to demonstrate the effectiveness of the proposed method.

Some very useful methods for suppressing the flow-induced vibration (FIV) of a single cylinder are known to potentially have a limited efficiency for tandem-arrangement cylinders. In this paper, three splitter plates uniformly attached around a cylinder with an angle of 120° are proposed to suppress the FIVs of both a single cylinder and two tandem-arrangement cylinders in a wind tunnel at Re = 4000–45,200. The splitter plates’ length to diameter ratios, L/Ds (where L is the length of the splitter plate and D is the cylinder diameter), are set from 0.1 to 0.8. The results show that the proposed method not only effectively suppresses the vortex-induced vibration (VIV) for a single cylinder, but also successfully mitigates the wake-induced galloping (WIG) for two tandem-arrangement cylinders. The vibrations of the single cylinders are effectively suppressed, consistently achieving suppression efficiencies over 95% for L/Ds = 0.2–0.8, with a notable peak efficiency of 98.4% at L/D = 0.2. For the two tandem-arrangement cylinders at S/D = 4.0 (where S is the center-to-center spacing between the two cylinders), the suppression efficiencies of the upstream cylinder exceed 96% for L/D = 0.2–0.8, with an optimal efficiency of 97.4% at L/D = 0.6. The downstream cylinder exhibits vibration only at L/Ds = 0.1, 0.2, and 0.4, resulting in suppression efficiencies of 80.3%, 67.1%, and 91.0%. The vibrations remain fully suppressed throughout the entire reduced velocity range for L/Ds = 0.6–0.8, reaching an optimal efficiency of 98.7% at L/D = 0.6. Three regimes of f_s/f_n characteristics can be classified for the single cylinder, and the wake structures show that shear layers develop along the front plate before attaching on the cylinder and are then offset to either side of the cylinder by the two rear splitter plates, contributing to the absence of periodic vortex shedding.

This study introduces an innovative model-order reduction (MOR) technique that integrates boundary element and finite element methodologies, streamlining the analysis of wideband vibro-acoustic interactions within aquatic and aerial environments. The external acoustic phenomena are efficiently simulated via the boundary element method (BEM), while the finite element method (FEM) adeptly captures the dynamics of vibrating thin-walled structures. Furthermore, the integration of isogeometric analysis within the finite element/boundary element framework ensures geometric integrity and maintains high-order continuity for Kirchhoff–Love shell models, all without the intermediary step of meshing. Foundational to our reduced-order model is the application of the second-order Arnoldi method coupled with Taylor expansions, effectively eliminating the frequency dependence of system matrices. The proposed technique significantly enhances the computational efficiency of wideband vibro-acoustic coupling analyses, as demonstrated through numerical simulations.