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This paper focuses on the development of a three-dimensional panel method in time and frequency domains combined with the finite element method for analyzing the hydroelastic responses of rotating marine propellers in the wake of ships. A fully non-penetration boundary condition imposed on the deformed blade surface is conducted, in which the corrections of both the incoming flow velocities and the normal vectors imposed on the deformed and undeformed blade surface are taken into account. The added-mass and -damping matrices due to strongly coupled fluid-structure interaction are considered. Results of the present method are compared with experimental data available in the literature. It is observed that the fully non-penetration boundary condition applied on the deformed blade surface should be imposed to predict the unsteady performance of elastic propellers, which is due to the change of the added damping predicted by considering different non-penetration boundary conditions. [ABSTRACT FROM AUTHOR]

• A hybrid multi-scale/arbitrary Lagrangian-Eulerian finite element method is proposed. • The novel method is used for predicting nonlinear structural-acoustic responses. • The novel method offers valuable insights into structural-acoustic interaction mechanisms. This paper introduces a novel hybrid multi-scale/arbitrary Lagrangian-Eulerian finite element method (HMS/ALE-FEM) for addressing the nonlinear vibro-acoustic problem of a large-deformed beam in an infinite fluid. In the HMS/ALE-FEM, the vibrational response of the beam is tackled through modal superposition and a temporal multi-scale approach, while the acoustic wave emitted from the beam is addressed using the arbitrary Lagrangian-Eulerian finite element method (ALE-FEM). An alternating frequency/time domain technique is employed to handle the displacement and velocity of the moving mesh and the acoustic pressure on the beam surface. To validate the HMS/ALE-FEM, it is compared against the finite element method for beam response and the ALE-FEM for acoustic response, serving as a reference method. Taking the nonlinear vibro-acoustic problem of a buckled beam with 2:1 internal resonance as an example, the results of the HMS/ALE-FEM are compared with those of the reference method. The results show that the HMS/ALE-FEM is in good agreement with the reference method under different harmonic excitation amplitudes and frequencies. Due to the 2:1 internal resonance, double modes can be generated, and the second mode amplitudes of both beam displacement and acoustic pressure remain constant as the excitation amplitude varies. Notably, the HMS/ALE-FEM provides direct access to mode amplitude and phase information for beam displacement and acoustic pressure on the beam surface, offering valuable insights into fluid-structure interaction mechanisms in both single- and double-mode scenarios. [ABSTRACT FROM AUTHOR]

The analysis of deformations of structures immersed in water due to explosion waves is important for off-shore oil and marine applications. A challenging issue in these problems is the satisfaction of continuity conditions at the fluid/structure interface. We numerically analyze these transient problems by using the ghost fluid/solid method, and coupling the isobaric fixing technique with the real ghost fluid method. We verify accuracy of the developed algorithm by comparing predictions from it with the analytical solution for a one-dimensional problem in which a plane wave traveling in water impinges upon a water/solid interface. We show that the coupled method has first order accuracy. Numerical results for the propagation of a spherical wave interacting with a fluid/solid interface computed with the developed method are found to compare well with those from the commercial software, ANSYS, that uses the arbitrary Eulerian–Lagrangian method. It is found that the intensity of the reflected tensile wave at a solid/water interface is less than that at a solid/air interface. Factors motivating this work include (i) using only the finite difference method for numerically solving equations governing transient deformations of fluids and solids that employs the ghost fluid/solid method to accurately satisfy continuity conditions at the fluid–solid interface, (ii) avoiding the need to refine the grid near the fluid–solid interface, and (iii) having an in-house capability of modeling detonation of a charge and study the interaction of the shock wave produced with the deformable structure. A novelty of the work is that the pressure due to a shock wave is not modeled as the product of a function of time and a function of space coordinates but its spatial and temporal dependence is found by solving the fluid–structure interaction problem. [ABSTRACT FROM AUTHOR]

The hydroelastic analysis of the propeller-shafting system in the non-uniform wake is a key step for designing a modern propeller-shafting system. The hydroelastic responses of the propeller-shafting system in the wake of ships are predicted by applying a three-dimensional time-frequency combined panel approach in conjunction with the finite element method. A fully non-penetration boundary condition applied on the deformed blade surface is conducted. The correction of both the incoming flow velocities and the normal vectors imposed on the blade surface of the transient vibration and the equilibrium positions is considered. The added-mass and -damping matrices due to strongly coupled fluid-structure interaction are derived. By comparing the present findings to numerical solutions calculated using the commercial tool Ansys Mechanical, the accuracy of the suggested technique is verified. It is observed that the added damping is higher, and the amplitudes of bearing forces are smaller, by applying the fully non-penetration boundary condition compared with the results obtained by imposing the other two simplified non-penetration conditions. This indicates that the designers need to imply the fully non-penetration condition on the deformed surfaces to predict the hydroelastic dynamics of the propeller-shafting system, especially in the case of high skew propellers. In addition, the amplitudes of the exciting forces after considering the fluid and propeller-shaft system interaction can be larger or smaller than those ignoring the interaction. The results depend on the phase difference and the mode shape. • A fluid-propeller-shafting system using a fully non-penetration condition was studied. • The correction of both the incoming flow velocity and normal vector was considered. • The fully non-penetration condition applied on deformed surfaces should be imposed. • The correction of the incoming flow velocities and the normal vectors is considered. [ABSTRACT FROM AUTHOR]

For a propeller vibrating in a fluid, the added mass and damping coefficients characterize the hydrodynamic forces and moments acting on the propeller, which are of great importance for evaluation of the vibration behaviors of submerged propellers. The present paper is concerned with the development of a numerical method for predicting the added mass and damping coefficients of a rotating marine propeller immersed in water. The three-dimensional panel method in frequency-domain is employed to establish the strongly coupled fluid-structure interaction models of the propellers to compute the added mass and damping coefficients. The relationship between the added mass and damping matrices due to the whole vibration of a rotating propeller and the local vibrations of the propeller blades is considered. Results of the present method are compared with those experimental and numerical data available in the literature. Very good agreement is achieved. The differences of the added mass and damping coefficients due to propeller vibrations of two types are analyzed. The results show that the added mass and damping coefficients of a submerged rotating propeller are functions of the ratio of oscillation frequency of rigid propeller f v to the blade frequency f b , and the advance ratio. In addition, the non-penetration boundary conditions should be imposed on the deformed blade surface for predicting the added mass and damping coefficients m 32 , m 62 , c 32 and c 62 , where m 32 ( c 32 ) and m 62 ( c 62 ) denote mass (damping) coefficients related to the lateral force and bending moment in the z direction induced by the transversal vibration in the y direction. Absolute values of all coefficients in the added mass matrix decrease as the ratio f v / f b is increased, and the absolute values of the coefficients in the added damping matrix increases with an increase in the advance ratio. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of a numerical model for the analysis of nonlinear fluid–structure interaction problems of large-deformable curvilinear fiber-reinforced composite laminated plates in viscous flows. A higher-order shear deformation zig-zag theory in conjunction with nonlinear von Kármán strains is employed to accommodate the large deformations of variable stiffness composite laminated plates. An implicit partitioned fluid–structure interaction method based on an arbitrary Lagrangian-Eulerian framework is adopted for dealing with the coupling of the large-deformable plate and the viscous flow. The validity of the proposed model and method is confirmed by comparing the computed results of a two-layered plate with those available solutions in the literature. Effects of material properties and fiber paths of composite plates on the periodic limit cycle oscillation and the wake-flow vortices are examined. It is found that symmetrical lay-ups of the constant stiffness composite laminated plates can produce asymmetrical flapping shapes, resulting in asymmetrical hairpin vortex structures in the wake flow. For a variable stiffness composite laminated plate, the flexibility of the leading or trailing sections can be adjusted by the curved fiber path, which in turn leads to changes in the plate flapping shapes. [ABSTRACT FROM AUTHOR]

• Two synchronizations (PLO, TLO) are identified in vortex-induced vibrations. • PLO and TLO patterns are influenced by cubic stiffness and rotating velocity. • Strong nonlinearity alters synchronization and induces separation bubble breaks. • Rotating velocity suppresses quadrupole sound modes. • Nonlinear stiffness triggers higher-order harmonic sound. The paper investigates the flow-induced vibration and sound wave propagation of a rotationally oscillating circular cylinder resting on a nonlinear elastic support and subject to compressible viscous flow with Reynolds number of R e = 150 and Mach number of M a = 0.2. An implicitly coupled fluid-structure interaction method based on an arbitrary Lagrangian-Eulerian framework is adopted to predict the dynamic responses of the cylinder. Direct numerical simulations of Navier-Stokes equations are performed to resolve the unsteady flow and sound waves. A nonlinear forced synchronization phenomenon, referred to as 'lock-on', occurring between nonlinear vortex-induced vibration and rotational excitation of the cylinder is examined. Two synchronization regions are identified, the primary lock-on and the tertiary lock-on. It is found that the nonlinear elastic mount significantly affects the synchronous patterns of the cylinder by amplifying higher-order harmonic components of the vibration response of the cylinder and altering the separating bubbles in the wake. Moreover, large rotational excitation of the cylinder delays the boundary layer separation, altering the shedding vortex patterns. Asynchronization between the rotational excitation and the vibration of the cylinder modulates the sound waves, while the synchronization produces dipole sound propagation modes containing high-order harmonic wave components. [ABSTRACT FROM AUTHOR]

A numerical method is presented for the analysis of interactions of inviscid and compressible flows with arbitrarily shaped stationary or moving rigid solids. The fluid equations are solved on a fixed rectangular Cartesian grid by using a higher-order finite difference method based on the fifth-order WENO scheme. A constrained moving least-squares sharp interface method is proposed to enforce the Neumann-type boundary conditions on the fluid-solid interface by using a penalty term, while the Dirichlet boundary conditions are directly enforced. The solution of the fluid flow and the solid motion equations is advanced in time by staggerly using, respectively, the third-order Runge-Kutta and the implicit Newmark integration schemes. The stability and the robustness of the proposed method have been demonstrated by analyzing 5 challenging problems. For these problems, the numerical results have been found to agree well with their analytical and numerical solutions available in the literature. Effects of the support domain size and values assigned to the penalty parameter on the stability and the accuracy of the present method are also discussed. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of a numerical method for analyzing the added mass and damping of a rotating elastic marine propeller. Three-dimensional panel methods in frequency domain combined with the finite element method were employed to study the strongly coupled fluid-structure interactions of the propeller. In order to overcome the computational efficiency problem due to the asymmetric added matrices of the fluid, a mode superposition method in conjunction with Wilson- θ method was employed for calculating the structural responses of the propeller. The validity of the proposed numerical method was confirmed by comparing the present results with experimental data available in the literature and those numerical solutions computed using commercial packages ANSYS and Virtual.Lab Acoustics. The effects of the excitation frequency, inflow velocity, material parameter of propeller and the advance ratio on the added mass and damping of rotating elastic propellers were examined. The results showed that stationary flow may be sufficient for analyzing the wet modes of the propeller at a relatively high excitation frequency, and the non-penetration boundary conditions should be imposed on the deformed blade surface rather than the undeformed surface in the case of relatively lower-frequency excitations. In addition, if the inflow velocity is relatively large, the added damping due to the fluid can significantly affect the unsteady performance of the propeller. [ABSTRACT FROM AUTHOR]

Vortex-induced vibration (VIV) of a flexible composite laminated beam rigidly attached to a circular cylinder in underwater flow is investigated. A general higher-order shear deformation zig-zag theory combined with von Kármán strains is adopted to characterize the geometrical nonlinearity of the composite laminated beam. A strongly coupled, partitioned fluid-structure interaction method based on an Arbitrary Lagrangian-Eulerian (ALE) approach is employed to accommodate the evolution of the fluid domain and the dynamic coupling of the fluid and the structure. The validity of the present method is confirmed. The discrepancies in the results of the VIV of isotropic and composite laminated beams determined by different beam theories are investigated. The effects of the fiber orientation and inflow velocity on the VIV characteristics (including limit-cycle oscillation, vortex shedding frequency, and flow pattern) of composite laminated beams are discussed. Four distinct deformation configurations of composite beams are observed, i.e., the first mode-like vibration shape, double-frequency vibration shape, second mode-like vibration shape, and lower-frequency large magnitude oscillation shape. Different deformation shapes lead to differences in the wake vortex modes, including the 2S (two single vortices with opposite signs) and the 2P (two pairs of vortices) wake vortex mode. • A general higher-order shear deformation zig-zag theory is developed. • Vortex-induced vibration behaviors of composite laminated beams are analyzed. • Effects of the fiber orientation and inflow velocity on the vortex-induced vibration characteristics are examined. • Physical insight into limit-cycle oscillation, vortex shedding frequency, and flow pattern is provided. [ABSTRACT FROM AUTHOR]

The understanding of the fluid-propeller-shafting system's hydroelastic behavior is critical for underwater vehicle vibration and noise reduction. A three-dimensional panel method coupled with a three-dimensional finite element method for analyzing the hydroelastic dynamics of fully coupled propeller and shafting systems in the non-uniform flows is developed. The fully coupled fluid-propeller-shafting model is utilized to assess the applicability of the traditional uncoupled fluid-propeller (elastic vibration)/fluid-propeller (six degrees rigid body oscillation)-shafting models, which consider the elasticities of the blades and shaft separately. It is found that the designers need to consider the elastic coupling effect between the shaft and the propeller, especially in the case of high skew propellers. In addition, the uncoupled model underestimates the fluid-induced damping. • The hydroelastic performance of elastic propeller-shafting system was studied. • A panel method combined with the finite element method were employed. • The coupling effect between the shaft and high skew propellers should be considered. • Fluid induced damping may be underestimated when the coupling effect is ignored. [ABSTRACT FROM AUTHOR]

• The hydroelastic response of propeller-shafting system in water was examined. • A coupled 3-D panel method/finite element method was proposed. • Propulsion system includes propeller, shaft, coupling, stern and thrust bearings. • The coupling of the fluid, propeller, and the shaft must be considered. The control of unsteady bearing forces generated by propellers is of great importance for the reduction of vibration and noise of underwater vehicles. This paper is concerned with the development of a numerical method for analyzing the hydroelastic behaviors of fully coupled marine propeller and shafting system immersed in water. A three-dimensional panel method for fluid modeling combined with a finite element method for modeling of the shafting system is developed. The two sets of equations of the structural system and the fluid are strongly coupled by considering the non-penetration boundary condition on the wet surface of the propeller. A modal reduction technique is employed to determine the hydroelastic responses of the coupled fluid-propeller-shafting system, which overcomes the low numerical efficiency of the method due to the asymmetric added matrices of the propeller. The validity of the proposed method is confirmed by comparing the present results with those solutions obtained from finite element analysis. It is found that for the case of the driving force frequency close to the umbrella mode frequencies of the propeller and longitudinal mode frequenices of the shaft, the coupling of the fluid, propeller, and the shaft must be taken into account for predicting the dynamic response of the system. A 3-D panel method coupled with a 3-D finite element method is developed for hydroelastic analysis of elastic propeller-shafting system in water. When the driving force frequency is close to the umbrella mode frequencies of the propeller and longitudinal mode frequencies of the shaft, the coupling of the fluid, propeller, and the shaft must be taken into account for predicting the dynamic response of the system. [Display omitted] [ABSTRACT FROM AUTHOR]

• An energy approach is proposed for vibration of fluid-filled FGP cylindrical shells under arbitrary boundary conditions. • Domain participating techniques for structural and 3D fluid domains are proposed, naturally reinforcing interface constrains. • Various porosities of the shell and fluid-structure interactions are considered. • Effects of material properties and boundary conditions on vibration behaviors of FGP shells are presented. • Added mass factor are introduced and effects of material properties on fluid-structure coupling are revealed. In this paper, a novel energy approach is proposed for fully coupled fluid-structure problems of functionally graded porous (FGP) fluid-filled cylindrical shells under arbitrary boundary conditions. Kinds of continuous FG materials are considered including various patterns in which the voids distributed. A modified variational principle is developed in fluid domain as well as in structural domain, naturally reinforcing the restrains on the boundaries and interfaces between adjacent subdomains. Energy functions in structural and fluid domain are deduced based on the first-order shear deformable shell theory (FSDT) and Helmholtz equation, respectively. The fluid-structure interactions are successfully introduced with the work done by the sound pressure and displacement continuous conditions at fluid-structural interface. A semi-analytical solution is obtained by expanding the displacement and sound pressure components analytically in the circumferential direction and numerically in the axial direction. Good convergence, high accuracy, superior efficiency and flexibility in using admissible functions are demonstrated by comparing reasonably many proposed results with those in literatures or obtained by FEM/BEM. Numerous examples are developed to examine the effects of material properties and boundary conditions on free vibration of FGP cylindrical shells with and without water. With added mass factor introduced, the influences of the key parameters on the fluid-structure coupling are also presented. The slight dependences of the added mass factor on material and boundary conditions greatly broaden the applied scope of the numerical results. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of a numerical model for predicting the hydroelastic responses of marine propellers oscillating in the wake of a submarine. The added-mass and -damping matrices due to strongly coupled fluid-structure interaction were considered. Three-dimensional panel methods in time and frequency domains combined with the finite element method were employed to study the hydrodynamic performance of the propeller. The panel methods were used to evaluate the hydrodynamic forces generated by the wake, and the finite element method was applied to determine the hydroelastic response of the propeller due to the pressure fluctuation. For predicting the structural responses, a mode superposition method combined with Wilson-θ method was employed to overcome the low numerical efficiency caused by the asymmetric added mass and damping matrices. The proposed numerical model was validated by comparing with other numerical solutions. The performance of the propellers was examined by considering one-way and two-way fluid-structure interactions. [ABSTRACT FROM AUTHOR]