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CN-122021135-A - Approximate analysis method based on nonlinear water elasticity response of ultra-large floating structure

CN122021135ACN 122021135 ACN122021135 ACN 122021135ACN-122021135-A

Abstract

The invention provides an approximate analysis method of nonlinear water elasticity response based on an oversized ocean floating structure (VLFS). And constructing a control equation and nonlinear boundary conditions under the coupling action of hydrodynamic force, elastic force and inertial force in a potential flow theoretical frame. VLFS is assumed to be an elastic or viscoelastic plate, and is converted into a plurality of linear sub-problems by using a Holen Analysis Method (HAM) in the case of a single module, the influence of important physical parameters on VLFS water elasticity response is analyzed, and in the case of a two-module combination connected by a hinge, how to select the module, connection rigidity and form are analyzed by adopting a finite element method so as to reduce the dynamic characteristic influence of a floating body. The invention provides an approximate analysis method combining HAM and finite element, fills the blank of the approximate analysis technology of nonlinear water elasticity response, has higher calculation efficiency on the premise of ensuring high calculation accuracy, obviously reduces time cost and economic cost, and provides important theoretical support for the design, construction, maintenance and the like of the offshore floating building.

Inventors

  • WANG PING
  • QI YUANZHI
  • Xin Youming

Assignees

  • 青岛科技大学
  • 东北大学

Dates

Publication Date
20260512
Application Date
20260112

Claims (10)

  1. 1. An approximation analysis method of nonlinear water elasticity response based on ultra-large floating structures (VERY LARGE Floating Structures, VLFS for short), characterized by comprising the steps of: Step 1, constructing a control equation and a nonlinear boundary condition under the coupling action of hydrodynamic force, elastic force and inertial force in a potential flow theoretical frame; Step 2, for the single-module situation, converting the single-module situation into a plurality of linear sub-problems by using a Holen analysis method (Homotopy Analysis Method, abbreviated as HAM), simultaneously expressing the speed potential to be solved and the board deflection as a series form, and selecting an optimal convergence control parameter value by using MATHEMATICS software to obtain a convergence approximate analysis solution; Analyzing the influence of important physical quantities such as Young's modulus, thickness, density, travelling wave amplitude and the like of the plate on the dynamic characteristics of the floating body; And 4, analyzing how to select reasonable modules, connection rigidity and form by adopting a finite element method to reduce the problem of influence of dynamic characteristics of the floating body in the case of the two-module combined floating body connected by the hinge.
  2. 2. The method of approximating a nonlinear water elasticity response based on an oversized floating structure of claim 5, wherein the oversized floating structure is assumed to be an elastic plate, The degree of winding of the elastic plate is the degree of winding, Is the pressure of the lower surface of the plate, Is the fluid density and the relationship between deflection and pressure on the lower surface of the plate is that Flexural rigidity of the plate , For the young's modulus of the panel, Is the thickness of the plate and, Is the Poisson ratio of the two-dimensional space, Is the acceleration of gravity and, , Is the board density.
  3. 3. The method of claim 1, wherein in the step 2, the mathematical model in claim 8 is converted into a zero-order deformation equation by using the Homolunar Analysis Method (HAM) based on the topology idea 。
  4. 4. The method of approximation analysis of nonlinear water elasticity response based on oversized floating structure of claim 9, wherein the As a result of the linear operator, Is a nonlinear operator; is an embedded variable. When (when) Continuously increasing from 0 to 1, two homoluns From initial guesses respectively Obtaining an accurate solution of the equation set And 。
  5. 5. The method for approximating a nonlinear water elasticity response based on an oversized floating structure according to claim 1, wherein in the step 2, based on the HAM algorithm, the method comprises the steps of Are respectively unfolded to be related to The Maclaurin series is substituted into the zero-order deformation equation, so that two sides of the equation are related to And the same power of the above is correspondingly equal to obtain a high-order deformation equation.
  6. 6. The method for approximating the nonlinear hydro-elastic response of an oversized floating structure according to claim 1, wherein in the step 3, in order to ensure the homolunar analytical series solution convergence of the infinite long plate hydro-elastic response problem in a single-layer fluid, a total square residual error corresponding to two boundary conditions is introduced 。
  7. 7. The method of approximating a nonlinear water elasticity response based on a very large floating structure according to claim 14, wherein the Representing the total number of discrete points and is provided with 。
  8. 8. The method of claim 14, wherein the total squared residual of each order approximation solution is based on an approximation of the nonlinear hydro-elastic response of an oversized floating structure With convergence of control parameters Is changed by a change in (a). For each order of solution there is always The minimum of (2) exists, i.e., there is an optimal solution. And with the order Is added to the number of the components, The value becomes rapidly smaller. Thus finally obtaining Is a solution to the optimization of (3). These results ensure that the homotopy analytical solution is convergent and accurate.
  9. 9. The method for approximating the nonlinear water elasticity response based on the ultra-large floating structure according to claim 1, wherein in the step 3, important physical quantities such as young's modulus, thickness, density, traveling wave amplitude and the like of the plate have very important influence on the dynamic characteristics of the floating body. The smaller the variation in deflection of the plate when the Young's modulus E of the plate is gradually increased from a small value, the flatter the nonlinear hydro-elastic response of the plate becomes at the peak as the thickness of the plate increases, and the smaller the variation in the nonlinear hydro-elastic response of the plate becomes. With plate density The flatter the plate deflection peaks become but the sharper the valleys become. At this time, the amplitude of the incident wave is similar to the influence of the thickness of the plate When the deflection of the plate becomes larger, the deflection of the plate becomes more sharp at the wave crest and steeper at the wave trough. The results show that the nonlinear water elastic response of the floating VLFS by utilizing the HAM research has higher feasibility and effectiveness.
  10. 10. The method for approximating the nonlinear water elasticity response based on the ultra-large floating structure according to claim 1 is characterized in that in the step 4, in addition to establishing a control equation and boundary conditions of surface kinematics and dynamics, the free boundary conditions of the plates, namely, the bending moment and equivalent shearing force at the end parts of the plates are zero, the boundary conditions at the junction of the plates and the hinges, namely, the bending moment of the plates is equal to the bending moment of the hinges, and the bending moment, shearing force and deflection of the left plate and the right plate are correspondingly equal. The boundary conditions are more and complex, the approximate analysis method is difficult to study, and the patent is designed to adopt a numerical method-a finite element method based on the previous study, so as to study how to select reasonable physical parameters to reduce the dynamic influence on nonlinear water elastic waves.

Description

Approximate analysis method based on nonlinear water elasticity response of ultra-large floating structure Technical Field The application relates to the technical field of water elasticity, in particular to analysis, calculation and simulation of nonlinear water elasticity response of a marine floating building in a complex marine environment. Background In order to fully utilize ocean resources, develop living space and defend the sea area of China, reasonably building ultra-large floating structures (VERY LARGE Floating Structures, VLFS for short) of offshore airplane sites, offshore military bases, industrial sites and the like becomes an increasingly important subject in ocean engineering and academia. VLFS the significant geometry is that the horizontal dimension is much larger than the vertical dimension, the elastic deformation and rigid displacement of VLFS under wave action are of the same magnitude, and in complex marine environments, the large amplitude wave nonlinear effect becomes very pronounced, so that the strong nonlinear hydro-elastic response of the structure becomes very significant and important. Accurately measuring the water elasticity response of VLFS in the ocean is one of the important technical problems for improving the design safety and economy of the ocean. For solving the problem of nonlinear water elasticity response, although a numerical method represented by a boundary element method, a finite element method, a difference method and a grid method achieves great achievement, the computing thinking of the method is to discretize an original equation and a boundary or initial condition, and the discretization changes the quantitative accuracy of the equation and also changes the qualitative property of the equation, so that a numerical result cannot provide any function formula relation and cannot reasonably analyze a mathematical model. For this purpose, analytical methods and analytical approximations should be developed. The approximate analysis method based on perturbation method is a main calculation method in the prior art. The essence of any perturbation method is the Taylor series expansion by small physical parameters, however in the problem of strong nonlinear hydro-elastic response, the wave steepness is no longer a small parameter as the wave amplitude becomes progressively larger, and the perturbation solution cannot be series expanded in this case. To overcome the limitation that the traditional perturbation method may fail under the strong nonlinear condition, for the single-module VLFS situation, it is an effective solution to find other methods which do not need to rely on any small parameters and can ensure the convergence of the resolution solution. Furthermore, in the case of the multi-module VLFS, since the evolution process of the nonlinear water elastic wave is very complicated at both ends of the module and at the connection of the module and the hinge, the influence of the rigidity and hinge position of the hinge on the elastic wave is studied by using a finite element method. Disclosure of Invention The invention aims to solve the problems of low efficiency and low accuracy of the existing ultra-large floating body hydro-elastic load prediction, and provides an approximate analysis method based on nonlinear hydro-elastic response of an ultra-large floating structure. The invention is realized by the following technical scheme: The invention relates to a nonlinear water elasticity response analysis method based on an oversized floating structure, which comprises the following steps: Step 1, in a potential flow theory framework, assuming that fluid is non-viscous, incompressible and motion is non-rotating, constructing a control equation and a nonlinear boundary condition under the coupling action of hydrodynamic force, elastic force and inertial force; Step 2, for the single-module elastic plate situation, the homolun analysis method provides a basic principle and a plurality of freedoms of selecting solution expression, initial guess solution and linear operators, can fully and tightly link the solution of an equation with the essence of the problem on the basis of analyzing the background of an actual problem and the type of the equation, better reflects the inherent physical meaning of the equation expression, converts a strong nonlinear water elasticity response model into a plurality of linear sub-problems, simultaneously expresses the speed potential to be solved and the deflection of the plate as series, applies MATHEMATICS software programming, selects the optimal convergence control parameter value, and further obtains the convergence approximate analysis solution; Step 3, displaying important physical quantities including important influences of fluid parameters, incident amplitude, boundary conditions of the plate, viscoelasticity parameters of the plate, young modulus, thickness, density and the like of the elastic plate on the dynamic cha