The present work is aimed to free vibration characteristics of marine propeller in fluid, and analyze the influence of fluid inertial effect on propeller. The fully coupled three dimensional finite element method is applied, and the commercial finite element code, ANSYS WORKBENCH, has been used to perform modal analysis for both wet and dry configurations via fluid-structure interaction APDL commands for secondary development. On this basis, analyze a marine propeller in air and in fluid with finite element analysis, then the differences of natural vibration frequencies and vibration modes of the propeller for different boundary conditions are discussed. In addition, the natural frequencies curves are presented. Results show that the natural frequencies of propeller in fluid are significantly lower than those in air, the fluid inertia effect also has some influences on vibration mode.
Ocean engineering structures often suffer from ice disaster damages, and the mechanism of interaction between sea ice and ocean structures is complex, the sea ice own properties are also changeful. Based on field researches and statistical results we can know the ice force amplitude. The solid model was established by the ANSYS Workbench module, then simulate the interaction of ice load and ocean engineering structures to verify the safety of ocean engineering structure. This kind of treatment provides an effective method for solving the similar problems, to guarantee the safety of ocean engineering building objective. Keywords:Ocean engineering structures; anti icing safety; ice force amplitude statistics; finite element method
From the basic equation of dynamics, the precise expression of the relationship ,which is between the horizontal natural frequency and pressure load of the cantilever beam with quality attached to the free end subjecting to vertical pressures, is obtained. The approximate expression derives from the variational method. By comparing the precise numerical solution and the approximate solution of the cantilever beam with quality attached to the free end and subjecting to the vertical pressures, the conclusion of approximate linear relationship that is between the square of the natural frequency and axial force of the cantilever beam with quality attached to the free end subjecting to the vertical pressures is got. Through the comparing of theoretical results and finite element solutions, the difference between the approximate solution and the precise numerical solution is small, which can meet the requirements of accuracy on engineering. On this basis, as long as the natural frequencies of the structure at two load conditions are measured by experimental methods, elastic buckling load of the compressed beam can be identified. So the no damage test method to identify the elastic buckling load of the structures is given.
From the basic equation of dynamics, the precise expression of the relationship, which is between the horizontal natural frequency and pressure load of the beam at two ends elastic fixed and subjecting to vertical pressures, is obtained. Its approximate expression derives from the variational method. By comparing the precise numerical solution and the approximate solution of the beam at two ends elastic fixed and subjecting to vertical pressures, the conclusion of approximate linear relationship that is between the square of the natural frequency and axial force of the beam at two ends elastic fixed and subjecting to vertical pressures is got. And the difference between the approximate solution and the accurate numerical solution is small, which can meet the requirements of accuracy on engineering. On this basis, as long as the natural frequencies of the structure at two load conditions are measured by experimental methods, elastic buckling load of the compressed beam can be identified. So the no damage test method to identify the elastic buckling load of the structures is given.
From the basic equations of dynamics, the precise expression of the relationship ,which was between the horizontal natural frequency and pressure load of the simply supported beam and the beam fixed at both ends with vertical pressures, was obtained. The approximate expression of the relationship, which was between the horizontal natural frequency and pressure load of the beam fixed at both ends with vertical pressures, derived from the variational methods. By comparing the precise numerical solution and the approximate solution of the beam fixed at both ends with vertical pressures, the conclusion of approximate linear relationship that was between the square of the natural frequency and axial force of the beam fixed at both ends with vertical pressures was got. Through theoretical and experimental comparing, the difference between the approximate solution and the accurate numerical solution was small, which could meet the requirements of accuracy on engineering. On this basis, as long as the natural frequencies of the structure at two load conditions are measured by experimental methods, elastic buckling load of the compressed beam can be identified.
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