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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]

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 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]

This paper investigates the structural and acoustic responses of a coupled propeller-shafting and submarine pressure hull system under different propeller force excitations. The entire system, which consists of a rigid propeller, a main shaft, two bearings and an orthogonally stiffened pressure hull, is submerged in a heavy fluid. The shaft is elastically connected to the pressure hull by a radial bearing and a thrust bearing. The theoretical model of the structural system is formulated based on a modified variational method, in which the propeller, the main shaft and the bearings are treated as a lumped mass, an elastic beam and spatially distributed spring-damper systems, respectively. The rings and stringers in the pressure hull are modeled as discrete structural elements. The acoustic field generated by the hull is calculated using a spectral Kirchhoff-Helmholtz integral formulation. A strongly coupled structure-acoustic interaction analysis is employed to achieve reasonable solutions for the coupled system. The displacement of the pressure hull and the sound pressure of the fluid are expanded in the form of a double mixed series using Fourier series and Chebyshev orthogonal polynomials, providing a flexible way for the present method to account for the individual contributions of circumferential wave modes to the vibration and acoustic responses of the pressure hull in an analytical manner. The contributions of different circumferential wave modes of the pressure hull to the structural and acoustic responses of the coupled system under axial, transversal and vertical propeller forces are investigated. Computed results are compared with those solutions obtained from the coupled finite element/boundary element method. Effects of the ring and the bearing stiffness on the acoustic responses of the coupled system are discussed. [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]