CN-121598715-B - Solving method for vibration hydrofoil motion response and fluid-solid coupling deformation

CN121598715BCN 121598715 BCN121598715 BCN 121598715BCN-121598715-B

Abstract

The application relates to the technical field of tidal current energy utilization, and discloses a method for solving oscillation hydrofoil motion response and fluid-solid coupling deformation, which comprises the steps of defining hydrofoil motion modes, structures and fluid key parameters, and defining core characteristics of pitching given motion, free heave motion and bending-twisting coupling deformation; the method comprises the steps of establishing a heave motion dynamics equation based on Newton's second law, constructing a bending coupling deformation control equation by combining a structural mechanics principle, constructing a three-dimensional numerical simulation model with a segmented grid and boundary layer encryption design, meeting calculation requirements through spanwise and time discretization, solving fluid distribution load and total lift force based on Navier-Stokes equation, solving heave motion response by adopting a fourth-order Dragon-Kutta method, and solving bending coupling deformation by adopting a Newmark-beta time integral method and a finite difference method. Therefore, the strong coupling characteristic of hydrofoil movement and fluid-solid coupling deformation can be accurately captured, and technical support is provided for design optimization and performance improvement of the oscillating hydrofoil type tidal current energy device.

Inventors

MA PENGLEI
ZHANG LEI
LIU GUIJIE
XIE YINGCHUN
NING DONGHONG
TIAN XIAOJIE

Assignees

中国海洋大学

Dates

Publication Date: 20260508
Application Date: 20260129

Claims (8)

1. The method for solving the motion response and the fluid-solid coupling deformation of the oscillating hydrofoil is characterized by comprising the following steps of: s1, defining a movement mode and core parameters of a hydrofoil, and constructing a heave movement dynamics equation and a bending-torsion coupling deformation control equation of the hydrofoil; s2, constructing a three-dimensional numerical simulation model of the hydrofoil, wherein the three-dimensional numerical simulation model comprises calculation domain setting, grid division and discretization; S3, solving the distributed fluid load of the hydrofoil surface by adopting a finite volume method based on a Navier-Stokes equation of incompressible fluid, and integrating the distributed fluid load to obtain the total lift force of the fluid at the current moment; S4, solving a heave motion response at a moment by adopting a fourth-order Longer-Kutta method based on the total fluid lift, the total hydrofoil mass and the heave parameter at the current moment, wherein the heave motion response at a moment is solved by adopting the fourth-order Longer-Kutta method based on the total fluid lift, the total hydrofoil mass and the heave parameter at the current moment, and the method comprises a step of constructing an intermediate state variable, wherein the step of calculating four heave speed derivative estimated values and heave acceleration estimated values at a starting point, a midpoint and an end point in a current time step respectively based on the heave speed at the current moment, the total fluid lift and the total hydrofoil mass, the four heave speed derivative estimated values at the starting point, the midpoint and the end point in the current time step respectively correspond to a current moment state, two intermediate moment states based on half-step prediction and a next moment state based on full-step prediction; S5, based on bending parameters, torsion parameters, force distribution parameters and structural parameters of hydrofoils at the current moment, utilizing a Newmark-beta time integral method and a finite difference method, combining solid-free boundary conditions, assembling a linear equation set, utilizing a Gaussian elimination method to solve bending deformation and torsion deformation at the next moment of each spanwise node, wherein the bending parameters, the torsion parameters, the force distribution parameters and the structural parameters of the hydrofoils at the current moment are utilized, utilizing the Newmark-beta time integral method and the finite difference method, combining the solid-free boundary conditions, assembling the linear equation set, comprising establishing an iterative equation about displacement, acceleration, torsion angle and torsion angle acceleration based on the bending parameters, utilizing the Newmark-beta time integral method, adopting a second-order space derivative and a fourth-order space derivative in a finite difference discrete torsion deformation equation, converting the differential of the spanwise node into a numerical equation, processing the boundary conditions by utilizing a virtual node method, processing i=0 and i=n, and fitting the linear equation set into a discrete deformation equation, and fitting the linear equation set after the linear equation set is assembled.
2. The method for solving the oscillating hydrofoil motion response and fluid-solid coupling deformation according to claim 1, wherein the construction logic of the iterative formula is: Based on Newmark-beta time integral principle, establishing linear prediction relation between displacement at next moment and displacement, speed and acceleration at current moment, and establishing correction logic of speed and acceleration, configured to reversely update acceleration at next moment by utilizing integral constant and displacement increment after solving displacement at next moment, and further correct speed at next moment by utilizing updated acceleration; The construction logic of the bending fourth-order derivative discrete format is that a center difference method is adopted to convert a fourth-order partial derivative term related to the spanwise position in a bending deformation control equation into a linear combination form of a target node and four node bending deflection values adjacent to the target node in the spanwise direction, and the fourth power of the grid spanwise direction step length is used as a normalization denominator; The construction logic of the torsional second derivative discrete format is that a second partial derivative term about the spanwise position in a torsional deformation control equation is converted into a linear combination form of elastic torsion angle values of a target node and two adjacent spanwise nodes by adopting a central difference method, and the square of the grid spanwise step length is used as a normalization denominator; The virtual node method processing logic is that virtual computing nodes are introduced to the outer side of a physical boundary aiming at the clamped boundary condition of a hydrofoil root and the free boundary condition of a wing tip, and a linear mapping equation of the virtual nodes and an internal physical node is established according to the displacement and derivative constraint relation at the boundary so as to eliminate an unknown item at the boundary of a differential equation set.
3. The method of claim 2, wherein constructing the heave dynamics equation and the camber coupling deformation control equation of the hydrofoil comprises: The heave motion dynamics equation is characterized in that a dynamic balance relation established based on Newton's second law is specifically defined as a product term of total mass and heave acceleration of the hydrofoil, and the product term is equivalent to a total fluid lift term acting on the surface of the hydrofoil at the current moment, so that a single degree-of-freedom translation rule of the hydrofoil under the drive of fluid load is described; The bending deformation control equation is characterized by a infinitesimal stress balance relation distributed along the hydrofoil span direction, and comprises an elastic restoring force term formed by the space fourth-order derivative of the bending rigidity and the bending deflection of the hydrofoil section, a first inertia force term formed by the time second-order derivative of unit span mass and deflection and a first damping force term formed by the time first-order derivative of the bending damping coefficient and deflection, wherein the algebraic sum of the elastic restoring force term, the first inertia force term and the first damping force term is constrained to be equal to the unit span fluid distribution lifting force at the position; The torsional deformation control equation is characterized by a moment balance relation distributed along the hydrofoil span direction, and comprises an elastic torsional moment term formed by the spatial second derivative of the torsional rigidity and the elastic torsion angle of the hydrofoil section, a second inertia moment term formed by the unit span polar inertia moment and the time second derivative of the torsion angle, and a second damping moment term formed by the torsional damping coefficient and the time first derivative of the torsion angle, wherein the linear combination of the elastic torsional moment term, the second inertia moment term and the second damping moment term is constrained to be equal to the unit span fluid distribution torque at the position.
4. The method for solving the motion response and the fluid-solid coupling deformation of the oscillating hydrofoil according to claim 1, wherein the constructing the three-dimensional numerical simulation model of the hydrofoil comprises: The calculation domain arrangement meets the condition that the distance from an inlet to the front edge of the hydrofoil is more than or equal to 2c, the distance from the rear edge of the hydrofoil to an outlet is more than or equal to 5c, the transverse range is more than or equal to 50c, the chord direction midpoint of the hydrofoil corresponds to X=0, and the span direction universe covers Z epsilon [0, L ]; the grid division adopts tetrahedron block grids, the wall surface of the hydrofoil is provided with a plurality of layers of boundary layer grids, the height of the first layer of grids is a preset height, the grid growth rate is a preset growth rate, the orthogonality of the grids is larger than or equal to a first preset value, and the torsion degree is smaller than or equal to a second preset value; The spanwise dispersion divides the hydrofoil spanwise length L into N segments to obtain N+1 nodes, and the node positions z i =i Δz; Wherein Δz=l/N; time dispersion of t n =n Δt, wherein Δt is less than or equal to 0.01T, and T is a pitching movement period.
5. The method for solving the motion response and the fluid-solid coupling deformation of the oscillating hydrofoil according to claim 1, wherein the Navier-Stokes equation based on incompressible fluid is used for solving the distributed fluid load of the hydrofoil surface by adopting a finite volume method, and integrating the distributed fluid load to obtain the total fluid lift at the current moment, and the method comprises the following steps: Writing a load extraction program through Fluent UDF, and traversing hydrofoil surface units by utilizing begin_f_loop and end_f_loop macro circulation to obtain unit span distributed lifting force Q z (z i ,t n ) and distributed torque T (z i ,t n ) at each span node; The Navier-Stokes equation includes the conservation of mass equation And momentum equation Wherein Is the fluid velocity vector, p is the fluid pressure, Is the volumetric force vector.
6. The method of solving for oscillating hydrofoil motion response and fluid-solid coupled deformations of any one of claims 1-5, further comprising: According to the heave motion response, bending deformation and torsional deformation at the next moment obtained by solving, the initial positions of grid nodes are overlapped, and the positions of the grid nodes are updated by heave translation, bending deformation and torsional deformation at the current moment; And (3) complementing the positions of the non-node grids by adopting linear interpolation, and completing continuous simulation through time step iteration.
7. The method of solving for oscillating hydrofoil motion response and fluid-solid coupled deformations of claim 6, wherein said updating grid node locations comprises: the initial position of the grid node is Superimposed heave translation Bending deformation ; When torsional deformation is superposed, the node rotates around the x-axis by the total torsion angle The coordinate correction is as follows: ; ; ; Wherein, the A local y-coordinate for the chordwise midpoint of the node relative to spanwise z i ; Is bending deflection; is the total torsion angle; is the elastic torsion angle caused by fluid-solid coupling; Is the heave displacement at the next moment.
8. A system for solving oscillating hydrofoil motion response and fluid-solid coupling deformation, comprising: The definition construction module is configured to define a movement mode and core parameters of the hydrofoil and construct a heave movement dynamics equation and a bending-torsion coupling deformation control equation of the hydrofoil; The model building module is configured to build a three-dimensional numerical simulation model of the hydrofoil and comprises calculation domain setting, grid division and discretization processing; The first calculation module is configured to solve the distributed fluid load of the hydrofoil surface by adopting a finite volume method based on a Navier-Stokes equation of incompressible fluid, and integrate the distributed fluid load to obtain the total fluid lift at the current moment; The second calculation module is configured to solve a heave motion response at a next moment by adopting a fourth-order grid-reservoir tower method based on the heave parameters of the fluid total lift, the hydrofoil total mass and the current moment, wherein the heave parameters of the fluid total lift, the hydrofoil total mass and the current moment are solved by adopting a fourth-order grid-reservoir tower method, and the method comprises a step of constructing an intermediate state variable, wherein the step of calculating four heave speed derivative estimated values and heave acceleration estimated values at a starting point, a midpoint and an end point in a current time step respectively based on the heave speed, the fluid total lift and the hydrofoil total mass at the current moment, the four heave speed derivative estimated values respectively correspond to a current moment state, two intermediate moment states based on half-step prediction and a next moment state based on full-step prediction; The third calculation module is configured to assemble a linear equation set based on bending parameters, torsion parameters, force distribution parameters and structural parameters of the hydrofoil at the current moment by utilizing a Newmark-beta time integral method and a finite difference method and combining solid-free boundary conditions, solve bending deformation and torsional deformation of each spanwise node at the next moment by utilizing a Gaussian elimination method, wherein the bending parameters, the torsional parameters, the force distribution parameters and the structural parameters of the hydrofoil at the current moment are processed by utilizing the Newmark-beta time integral method and the finite difference method and combining solid-free boundary conditions to form the linear equation set, the linear equation set comprises the steps of establishing an iterative equation about displacement, acceleration, torsion angle and angular acceleration by utilizing the Newmark-beta time integral method, discrete space derivative and four space derivative in the torsional deformation equation by utilizing the finite difference method, converting the differential of the spanwise node into a numerical number, processing boundary conditions by utilizing the Newmark-beta time integral method and the finite difference method and combining the solid-free boundary conditions, and substituting the linear equation set into a discrete deformation equation, and the linear equation set is assembled after the linear equation set is processed by utilizing the virtual node method to process boundary conditions, i=0=N=0.

Description

Solving method for vibration hydrofoil motion response and fluid-solid coupling deformation Technical Field The application relates to the technical field of tidal current energy utilization, in particular to a solving method for oscillating hydrofoil motion response and fluid-solid coupling deformation. Background The tidal current energy is taken as renewable ocean clean energy, and has the remarkable advantages of high energy density, strong stability, good predictability and the like. The oscillating hydrofoil type tidal current energy power generation device is one of core equipment for capturing tidal current energy, fluid kinetic energy is converted into mechanical energy through periodic oscillating motion of hydrofoil in tidal current, power generation is further achieved, and the energy capturing efficiency and the structural reliability directly determine engineering application value of the tidal current energy device. The oscillating hydrofoil is used as a key core component of the oscillating hydrofoil type tidal current energy device, a composite motion mode of 'given pitching motion and free heave motion' is adopted, and a pitching axis is usually arranged near the center of the hydrofoil pressure so as to reduce pitching moment and optimize energy capturing efficiency. In the actual working process, the hydrofoil can generate free heave movement under the action of fluid load, and bending and torsional deformation (namely fluid-solid coupling deformation) can also occur due to the strong coupling action of the self flexible characteristic and the fluid load, and the coupling effect of the movement and the deformation directly changes the actual attack angle distribution, the fluid load characteristic and the movement posture of the hydrofoil, so that the energy capturing efficiency and the structural fatigue life of the device are obviously influenced. Therefore, the motion response and fluid-solid coupling deformation law of the oscillating hydrofoil are accurately described, and the method is a key premise for optimizing design and improving performance of the tidal current energy device. However, the prior art has a plurality of defects in the aspects of motion and deformation analysis of the oscillating hydrofoil, and the requirements of engineering application on simulation precision and reliability are difficult to meet: firstly, the traditional research mostly adopts a rigid hydrofoil hypothesis, ignores the flexible deformation of the hydrofoil, or simplifies the deformation into bending deformation in a single direction, and does not consider the coupling effect of bending and torsion, so that a numerical simulation result has larger deviation from an actual working condition, and the influence of fluid-solid coupling effect on the hydrofoil movement and load distribution cannot be accurately reflected; Secondly, a strong coupling relation exists between the fluid load and the hydrofoil movement and deformation, and the existing solving method mostly adopts a unidirectional coupling strategy (namely, the fluid load is calculated firstly and then applied to a structure as an external load to solve the deformation), and the reaction of the change of the hydrofoil posture on the fluid flow field after the deformation is not considered, so that the accuracy of the coupling solving is insufficient; Thirdly, aiming at defects of a numerical simulation model of the oscillating hydrofoil, for example, insufficient development of incoming flow or insufficient wake diffusion caused by unreasonable setting of a calculation domain boundary, low calculation precision of fluid load caused by wall surface requirements of a grid division unadapted turbulence model, easy divergence of a solving process caused by unsatisfied stability conditions of a time and space discretization scheme, and the reliability of a simulation result is affected by the problems; fourth, a complete solving system is lacking, the prior art focuses on a single link of motion response or fluid-solid coupling deformation, a full-flow solving method from parameter definition, model establishment, load solving to motion and deformation iterative calculation and grid updating is not formed, and the method is difficult to be directly applied to engineering design and optimization. In addition, as the tidal current energy device is developed to the large-scale and large-scale direction, the performance requirement on the oscillating hydrofoil is continuously improved, and the traditional simplified model and solving method cannot meet the requirements of the device optimization design on accuracy and comprehensiveness. It should be noted that the information disclosed in the above background section is only for enhancing understanding of the background of the application and thus may include information that does not form the prior art that is already known to those of ordinary skill in the art. Disclosure of Invention The follow