Square column vortex-induced oscillation suppression composite structure with rear flexible plate and its design method

Abstract

This invention relates to a combined structure for suppressing vortex-induced oscillations of a square column with a rear flexible plate and its design method. The combined structure includes a square column and a flexible plate disposed at the rear of the square column. The design method includes: S1 numerical simulation of vortex-induced oscillations of a single square column in flow; S2 numerical simulation of vortex-induced oscillations of the combined structure of square column and rear flexible plate in flow; S3 comparing the kinematic and dynamic responses of vortex-induced oscillations of a single square column and the combined structure of square column and rear flexible plate; S4 obtaining the model parameters of the combined structure of square column and rear flexible plate with the best vibration reduction and drag reduction effect. The combined structure of this invention can significantly reduce the amplitude of vortex-induced oscillations and the time-averaged drag, thereby effectively improving the stability and safety of the structure. The numerical analysis method for parameter design and optimization of the square column and rear flexible plate proposed in this invention can design the shape and size of the structure more economically, efficiently, and accurately, regardless of the material parameters, size, deformation shape, specific placement position of the flexible plate, or the complexity of the flow field environment.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, specifically to a combined structure for suppressing vortex-induced oscillations of a square column with a rear-mounted flexible plate and its design method. Background Technology

[0002] Vortex-induced oscillation of a square column is caused by alternating vortices shedding off from both sides and the tail during flow around the column. The periodic force generated by these vortex shedding forces the elastically or elastically supported column to vibrate. This vibration, in turn, affects the characteristics of the wake flow field, creating a complex fluid-structure interaction problem involving passive motion. When resonance occurs, i.e., when the vibration frequency of the square column is close to the vortex shedding frequency, the structure experiences large-amplitude oscillations, severely impacting its stability and safety.

[0003] Studies of vortex-induced oscillations in a square column show that when fluid flows through it, the column experiences resistance in the direction of flow and lift perpendicular to the flow direction. The lift is caused by pulsations resulting from vortex shedding, while the resistance consists of pressure differential drag caused by the pressure difference across the column due to vortex shedding and viscous drag generated by viscosity. In vortex-induced oscillations, the vibration is primarily manifested as oscillations of the column in the direction of lift. In engineering, long-term vortex-induced oscillations in offshore platform supports and bridges can not only compromise structural stability but also cause structural damage if resonance occurs. Therefore, vortex-induced oscillation suppression has significant application value and research significance.

[0004] In studying the coupled motion of a flexible plate and a cylinder in a flow field, it was found that the flexible structure passively deforms under the influence of the incoming flow, forming complex multi-frequency vortices in its tail flow field. These vortices interact with the flexible structure, significantly affecting its dynamic characteristics. The flexible structure within the vortex street can extract energy from the vortex street, reducing the forces acting on the system to some extent. Therefore, if the square cylinder can be improved based on the characteristics of its flexible structure to reduce the alternating forces exerted on the structure by the flow field, it will greatly benefit both theoretical research and engineering applications. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the problem of large-amplitude vibrations generated during the resonance of vortex-induced oscillations of a square column. This invention provides a combined structure for suppressing vortex-induced oscillations of a square column with a rear flexible plate and its design method, thereby effectively suppressing the oscillation of the combined structure.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A combined structure for suppressing vortex-induced oscillations of a square column with a rear flexible plate includes a square column and a flexible plate disposed at the rear of the square column. The flexible plate is disposed perpendicular to the surface of the square column and is located at the midpoint of the side length of the cross-section of the square column.

[0008] In the above scheme, the flexible plate is connected to the square column hinge.

[0009] In the above scheme, the flexible plate is made of lightweight and corrosion-resistant materials.

[0010] Accordingly, the present invention also proposes a design method for the above-mentioned combined structure for suppressing vortex-induced oscillation of the rear flexible plate, comprising the following steps:

[0011] S1. Numerical simulation of vortex-induced oscillation of a single square cylinder in a flow path, specifically including the following steps:

[0012] S1.1 Establish the structural and flow field analysis model of the square column;

[0013] S1.2. For the longitudinal motion of the square column, a structure-spring-damping model is established. Numerical experiments are conducted on the vortex-induced oscillation characteristics of a single square column under a set Reynolds number Re using computational fluid dynamics methods. The lift coefficient, drag coefficient, and dimensionless amplitude of the square column oscillation are calculated during the vortex-induced oscillation process.

[0014] S2. Numerical simulation of vortex-induced oscillation of the combined structure of the central column and the flexible plate behind it in the flow path, specifically including the following steps:

[0015] S2.1. Select flexible plates of different lengths and flexibility to establish a structural and flow field analysis model for the combined structure of square column and rear flexible plate.

[0016] S2.2 Calculate the vortex-induced oscillation motion of the combined structure model with a square column and a flexible plate at the same Reynolds number Re. Numerical experiments are conducted to obtain the lift coefficient, drag coefficient, and dimensionless amplitude of the combined structure oscillation under flexible plates of different lengths and flexibility.

[0017] S3. Comparison of the kinematic and dynamic responses of vortex-induced oscillations between a single square column and a combination structure with a flexible plate behind the square column:

[0018] Based on the calculation results of steps S1 and S2, the lift coefficient, drag coefficient, and dimensionless oscillation amplitude of a single square column and a combined structure of a column with a flexible plate at the rear with different lengths and flexibility are compared, and the vibration reduction and drag reduction effects of the combined structure with a flexible plate at the rear are analyzed.

[0019] S4. Obtain the model parameters of the square column rear flexible plate combination structure with the best vibration reduction and drag reduction effect.

[0020] In the above method, in step S1.2, the motion of the square column structure-spring-damped model in the flow field is controlled by the longitudinal motion equation (1).

[0021]

[0022] In the formula: Y is the dimensionless amplitude of the square column oscillation, Y = y / D, y is the longitudinal displacement of the square column, and D is the side length of the square column. Let represent the dimensionless velocity and dimensionless acceleration of the square column, respectively.

[0023] ξ is the damping ratio;

[0024] U * For the reduction speed, U * =U ∞ / f n D, f n U is the natural frequency of the square cylinder. ∞ The fluid velocity;

[0025] C L The lift coefficient, F L Let ρ be the lift force acting on the square prism. f For fluid density;

[0026] m * =m / ρ f D 2 is the mass ratio of the square column to the fluid, and m is the mass of the square column;

[0027] Fluid motion is solved using the Navier-Stokes equations or the lattice Boltzmann method; the motion of viscous incompressible flow fields is solved using the Navier-Stokes equations:

[0028]

[0029]

[0030] In the formula: ρ f Where is the fluid density, p is the fluid pressure, u is the velocity vector, t is time, μ is the fluid dynamic viscosity coefficient, and f is the force density;

[0031] The lattice Boltzmann method involves discretely solving the lattice Boltzmann equations. The governing equations are as follows:

[0032] f α (x+e α δ t ,t+δ t )=f α (x,t)+Φ α (4)

[0033] Where: δ t The time step is α, which represents the discrete lattice direction, and e is the time step. α Φ is the lattice velocity vector. α f represents the collision term and the external force term. α Let x be the density distribution function, x be the coordinates of the Euler point, and t be time.

[0034] The coupling between the square column and the flow field adopts the immersed boundary method. The flow field is described by an Eulerian grid and the structural boundary is described by a Lagrange grid. The effect of the complex boundary is transformed into a force source term on the Eulerian grid, and the force and velocity between the Lagrange point and the Eulerian point are converted by the Delta function δ(xX(s,t)) in Equations (5) and (6).

[0035]

[0036]

[0037] In the formula: x is the position coordinate of the Euler point, X is the position coordinate of the Lagrange point, s is the coordinate label of the Lagrange point, ds is the length of the line segment of the Lagrange boundary, u is the velocity vector, f(x,t) is the force density at the corresponding time position, and F(s,t) is the force on the solid boundary point.

[0038] By solving the oscillation equation of the square column as shown in equation (1) and the flow field equation as shown in equations (2)-(3) or (4) through coupling, the lift coefficient C of the square column can be calculated. L Drag coefficient C D The dimensionless amplitude Y of the square column oscillation.

[0039] In the above method, in step S2.2, the solution for the oscillation and flow field of the square column in the combined structure of the square column and the flexible plate is the same as the numerical solution method for the vortex-induced oscillation of a single square column in S1.2. The oscillation equation of the square column is shown in equation (1), and the flow field equation is shown in equations (2)-(3) or (4). The passive motion of the flexible plate is solved by the motion equation of the flexible plate. The motion equation of the flexible plate is shown in equation (7), and equation (8) represents the non-stretchable condition of the flexible plate.

[0040]

[0041]

[0042] In the formula: ρ s X is the linear density of the flexible plate. s These are the position coordinates of the flexible plate. This represents the derivative of a physical quantity along the tangent to the plate, where t is time, T is the tensile tension, and K is the coefficient of friction. b For bending stiffness, F f The force exerted on the plate by the fluid flow;

[0043] The coupling between the square column rear flexible plate combination structure and the flow field adopts the immersion boundary method, and the force and velocity between the Lagrange point and the Euler point are converted by the Delta function δ(xX(s,t)) in Equations (5) and (6);

[0044] By coupling the oscillation equation of the square column as shown in equation (1), the flow field equation as shown in equations (2)-(3) or (4), and the motion equation of the flexible plate as shown in equation (7), the lift coefficient C′ of the square column rear flexible plate combined structure is calculated. L Drag coefficient C′ D The dimensionless amplitude Y′ of the combined structure oscillation.

[0045] In the above method, in step S3, the average flow field is used to analyze the flow field characteristics. The average flow field is the flow field averaged over one oscillation cycle.

[0046] The beneficial effects of this invention are as follows:

[0047] 1. The vortex-induced oscillation suppression combined structure with a square column rear flexible plate designed in this invention can significantly reduce the amplitude of vortex-induced oscillation and the time-averaged drag, thereby effectively improving the stability and safety of the structure. The numerical analysis method for parameter design and optimization of the square column rear flexible plate proposed in this invention can design the structural shape and size more economically, efficiently, and accurately, regardless of the material parameters, size, deformation shape, specific placement location of the flexible plate, or the complexity of the flow field environment.

[0048] 2. In the optimal design of this invention, the dimensionless oscillation amplitude of the square column in the vortex-induced oscillation suppression structure with a flexible plate at the rear of the square column can be reduced by up to 76.83%, the oscillation amplitude of the lift coefficient can be reduced by 85.90%, and the average drag coefficient can be reduced by 33.31%. During use, the specific parameters of this vortex-induced oscillation suppression structure with a flexible plate at the rear of the square column can be adjusted to the optimal state using the CFD design method employed in this invention, effectively suppressing the vortex-induced oscillation of the square column.

[0049] 3. The structure designed according to the present invention has a wide range of applications and can be used in marine engineering, construction and other fields. Attached Figure Description

[0050] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0051] Figure 1 This is a schematic diagram of the combined structure for suppressing vortex-induced oscillations of the rear flexible plate of the present invention.

[0052] Figure 2 This is the structural and flow field analysis model of the square column established in the design method of this invention;

[0053] Figure 3 This is the structure-spring-damping model of the square column established in the design method of this invention;

[0054] Figure 4 This is the structural and flow field analysis model of the square column rear flexible plate combination structure established in the design method of this invention;

[0055] Figure 5 This is the average flow field vorticity diagram of a single square column in an embodiment of the present invention;

[0056] Figure 6 In this embodiment of the invention, the square column is rear-positioned with L = 1.5D, w * =1.5 Average flow field vorticity contour plot of flexible plate composite structure;

[0057] Figure 7 This is the average flow field pressure cloud map of a single square column in an embodiment of the present invention;

[0058] Figure 8 In this embodiment of the invention, the square column is rear-positioned with L = 1.5D, w * =1.5 Average flow field pressure contour map of flexible plate composite structure. Detailed Implementation

[0059] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0060] like Figure 1 As shown, this invention proposes a combined structure for suppressing vortex-induced oscillations of a square column with a rear-mounted flexible plate. The structure includes a square column and a lightweight, corrosion-resistant flexible plate positioned at the rear of the square column. The square column and the flexible plate are hinged together. The flexible plate is perpendicular to the surface of the square column and positioned at the midpoint of the side length of the square column's cross-section. The square column and the flexible plate form a combined structure; wherein the square column has a square cross-section with a side length of D, and the mass ratio of the square column to m... * =2; The length of the flexible plate is represented by L. The thickness of the flexible plate is very small compared to its length and can be ignored. In the design of the combined structure for suppressing vortex-induced oscillation, plates with different lengths and different flexibility are selected for numerical experiments and comparative analysis to determine its structural parameters.

[0061] Accordingly, this invention also proposes a design method for the aforementioned combined structure of a square column with a rear flexible plate to suppress vortex-induced oscillations. To determine the vortex-induced oscillation suppression effect of this combined structure, computational fluid dynamics (CFD) numerical experiments are first conducted on the vortex-induced oscillation of a single square column. Then, high-fidelity numerical simulations are performed on the designed combined structure of the square column with a rear flexible plate. The lift coefficient, drag coefficient, and oscillation amplitude of the structures are compared, and the structural parameters of the combined structure of the square column with a rear flexible plate that has the best vortex-induced oscillation suppression effect are selected. This design method specifically includes the following steps:

[0062] S1. Numerical simulation of vortex-induced oscillation of a single square cylinder in a flow path, specifically including the following steps:

[0063] S1.1 Establish the structural and flow field analysis model of the square column. For example... Figure 2As shown, a geometric model of the oscillating square prism problem in the flow field is constructed, and the size of the computational domain is determined based on the dimensions of the square prism. On this basis, a structural and flow field analysis model of the oscillating square prism is established. It should be noted that... Figure 2 Middle U ∞ The value represents the fluid velocity, D represents the side length of the square column, and y on the left represents the displacement of the square column in the y direction.

[0064] S1.2 Since the vortex-induced oscillation of the square column is mainly longitudinal (perpendicular to the flow direction, i.e., the y-direction shown in the figure), only the longitudinal motion is considered. A structure-spring-damping model is established for the longitudinal motion of the square column. Numerical experiments are conducted using computational fluid dynamics (CFD) to investigate the vortex-induced oscillation characteristics of a single square column at a set Reynolds number Re. The lift coefficient, drag coefficient, and dimensionless amplitude of the square column oscillation during the vortex-induced oscillation process are calculated. Among them, the lift coefficient C... L =2F L / (ρ f U ∞ 2 D), drag coefficient C D =2F D / (ρ f U ∞ 2 D), F L F is the lift force experienced by the square column during vortex-induced oscillation. D U represents the resistance encountered during the vortex-induced oscillation of a square column. ∞ ρ is the fluid velocity. f Let be the fluid density. The dimensionless amplitude of the square column oscillation is Y = y / D, which is the ratio of the amplitude y to the side length D of the square column.

[0065] The established spring-damping model is as follows: Figure 3 As shown, its motion in the flow field is controlled by the longitudinal motion equation (1).

[0066]

[0067] In the formula: Y is the dimensionless amplitude of the square column oscillation, Y = y / D, y is the longitudinal displacement of the square column, and D is the side length of the square column. Let represent the dimensionless velocity and dimensionless acceleration of the square column, respectively.

[0068] ξ is the damping ratio;

[0069] U * For the deceleration rate, U * =U ∞ / f n D, f n U is the natural frequency of the square column. ∞ The fluid velocity;

[0070] CL The lift coefficient, F L Let ρ be the lift force acting on the square prism. f For fluid density;

[0071] m * =m / ρ f D 2 Let m be the mass ratio of the square column to the fluid, and m be the mass of the square column.

[0072] Fluid motion is solved using the Navier-Stokes equations or the lattice Boltzmann method. The motion of viscous incompressible flow fields is solved using the Navier-Stokes equations:

[0073]

[0074]

[0075] In the formula: ρ f Let ρ be the fluid density, p be the fluid pressure, u be the velocity vector, t be the time, μ be the fluid dynamic viscosity coefficient, and f be the force density.

[0076] The lattice Boltzmann method involves discretely solving the lattice Boltzmann equations. The governing equations are as follows:

[0077] f α (x+e α δ t ,t+δ t )=f α (x,t)+Φ α (4)

[0078] Where: δ t The time step is α, which represents the discrete lattice direction, and e is the time step. α Φ is the lattice velocity vector. α f represents the collision term and the external force term. α Let x be the density distribution function, x be the coordinates of the Euler point, and t be time.

[0079] The coupling between the square column and the flow field adopts the immersed boundary method. The flow field is described by an Eulerian grid and the structural boundary is described by a Lagrange grid. The effect of the complex boundary is transformed into a force source term on the Eulerian grid, and the force and velocity between the Lagrange point and the Eulerian point are converted by the Delta function δ(xX(s,t)) in Equations (5) and (6).

[0080]

[0081]

[0082] In the formula: x is the position coordinate of the Euler point, X is the position coordinate of the Lagrange point, s is the coordinate label of the Lagrange point, ds is the length of the line segment of the Lagrange boundary, u is the velocity vector, f(x,t) is the force density at the corresponding time position, and F(,t) is the force on the solid boundary point.

[0083] By solving the oscillation equation of the square column as shown in equation (1) and the flow field equation as shown in equations (2)-(3) or (4) through coupling, the lift coefficient C of the square column can be calculated. L Drag coefficient C D The dimensionless amplitude Y of the square column oscillation.

[0084] Since the forces acting on the square column are periodic, after comprehensive consideration, the dimensionless amplitude of the square column is used to analyze the oscillation amplitude of the square column, and the oscillation amplitude of the lift coefficient and the mean value of the drag coefficient are used to analyze the hydrodynamic forces acting on the square column.

[0085] In this embodiment, for Re = 150, the mass ratio m * =2, Deceleration rate U * For flow around a square column with a value of 5, the dimensionless amplitude Y of the oscillation of a single square column is 0.46, the oscillation amplitude of the lift coefficient is 1.963, and the average drag coefficient is 2.338.

[0086] S2. Numerical simulation of vortex-induced oscillation of the combined structure of the central column and the flexible plate behind it in the flow path, specifically including the following steps:

[0087] S2.1. Establish structural and flow field analysis models for the combined structure of a square column and a rear flexible plate using flexible plates of different lengths and flexibility. For example... Figure 4 As shown, based on the dimensions of the square column and the computational domain in step S1, flexible plates of different lengths and flexibility are designed, and the flexible plates are placed behind the square column. On this basis, a structural flow field analysis model of the combined structure of square column and flexible plate is established.

[0088] S2.2 Calculate the vortex-induced oscillation motion of the combined structure model with a flexible plate behind the square column at the same Reynolds number Re. The lift coefficient, drag coefficient and dimensionless amplitude of the combined structure oscillation are obtained by numerical experiments under different parameters of the flexible plate behind the column.

[0089] The solution for the oscillation and flow field of the square column in the combined structure of the square column and the flexible plate is the same as the numerical solution method for the vortex-induced oscillation of a single square column in S1.2. The oscillation equation of the square column is shown in Equation (1), and the flow field equation is shown in Equations (2)-(3) or (4). The passive motion of the flexible plate is solved by the motion equation of the flexible plate, which is shown in Equation (7). Equation (8) represents the non-stretchable condition of the flexible plate.

[0090]

[0091]

[0092] In the formula: ρ s X is the linear density of the flexible plate. s These are the position coordinates of the flexible plate. This represents the derivative of a physical quantity along the tangent to the plate, where t is time, T is the tensile tension, and K is the coefficient of friction. b For bending stiffness, F f The force exerted on the plate by the fluid flow;

[0093] The coupling between the square column rear flexible plate combination structure and the flow field adopts the immersion boundary method, and the force and velocity between the Lagrange point and the Euler point are converted by the Delta function δ(xX(s,t)) in Equations (5) and (6);

[0094] By coupling the oscillation equation of the square column as shown in equation (1), the flow field equation as shown in equations (2)-(3) or (4), and the motion equation of the flexible plate as shown in equation (7), the lift coefficient C′ of the square column rear flexible plate combined structure is calculated. L Drag coefficient C′ D The dimensionless amplitude Y′ of the combined structure oscillation.

[0095] Since the forces acting on the square column are periodic, after comprehensive consideration, the dimensionless amplitude of the combined structural oscillation is used to analyze the oscillation amplitude of the square column in the combined structure with the flexible plate behind it. The kinematic and dynamic characteristics of the combined structure with the flexible plate behind it are analyzed by the oscillation amplitude of the lift coefficient and the mean value of the drag coefficient.

[0096] In this embodiment, flexible plates of different lengths and flexibility are designed. A high-fidelity numerical simulation is performed on the model of the designed composite structure of multiple square columns with subsequent flexible plates, following the method described in step S2 above. Then, statistical analysis is conducted on the different lengths L and flexibility w of the subsequent plates. * The oscillation amplitude of the lift coefficient, the average drag coefficient, and the dimensionless amplitude of the oscillation of the combined mechanism under the flexible plate.

[0097] The flexibility of the board w * =2πf v ω n ,in K b f is the bending coefficient. v The vortex shedding frequency is the frequency of a single fixed square column.

[0098] In the design parameters of the flexible panel, the length L is taken as 1.2D, 1.5D, or 3D; the flexibility w * Choose: 1, 1.5, 2.

[0099] In this embodiment, under the same Reynolds number, the mean values ​​of the dimensionless amplitude, lift coefficient oscillation amplitude, and drag coefficient of the combined structure of flexible plates with different lengths and flexibility are shown in Table 1 below:

[0100] Table 1. Structure of different scheme combinations

[0101]

[0102] S3. Compare the kinematic and dynamic responses of vortex-induced oscillations between a single square column and a combination structure with a flexible plate behind the square column.

[0103] Based on the calculation results of steps S1 and S2, the lift coefficient, drag coefficient, and dimensionless oscillation amplitude of a single square column and a composite structure with a flexible plate behind the column of different lengths and flexibility are compared, and the vibration reduction and drag reduction effects of the composite structure with a flexible plate behind the column are analyzed.

[0104] The flow field characteristics are analyzed using an average flow field, where the average flow field is averaged over one oscillation cycle. When fluid flows through a single square cylinder, the pressure contour plot of the average flow field is obtained (…). Figure 7 As can be seen from the diagram, the pressure difference before and after the square column is large, and the vertical pressure has a wide range of action, resulting in a large pressure drag around the square column. This is evident from the average flow field vorticity diagram of a single square column. Figure 5 As can be seen from the diagram, the areas of vortex shedding from the sides and tail of the square column are relatively large, resulting in significant vertical vibration amplitude and stress on the column. Furthermore, the average flow field pressure cloud diagram of the square column with a flexible plate at the rear (…) Figure 8 As can be seen from the diagram, the pressure difference before and after the square column is small, and the vertical pressure distribution range is also small. This is evident from the corresponding average flow field vorticity contour plot. Figure 6 As can be seen from the diagram, the range of vortices detached from both sides and the tail of the square column is significantly reduced, thus decreasing the vertical vibration amplitude of the square column. From a kinematic and dynamic perspective, the results of steps S1 and S2 show that, compared to the vortex-induced oscillation of a single square column, the addition of a flexible plate at the rear of the square column significantly reduces the dimensionless oscillation amplitude, lift coefficient oscillation amplitude, and mean drag coefficient. Therefore, the addition of a flexible plate at the rear of the square column demonstrates excellent vibration and drag reduction effects.

[0105] S4. Obtain the model parameters of the square column rear flexible plate combination structure with the best vibration reduction and drag reduction effect of the vortex-induced oscillation suppression structure.

[0106] After placing a flexible plate behind the square column, the dimensionless amplitude of the square column's oscillation, the oscillation amplitude of the lift coefficient, and the mean values ​​of the drag coefficient are all significantly reduced compared to a single square column. The vibration reduction and drag reduction effects vary depending on the flexibility of the flexible plate. Numerical experimental results show that, within the current design parameter range, the flexible plate w behind the square column... *The optimal vibration and drag reduction effects are achieved when L = 1.5D and L = 1.5D. In the optimal scheme, the vortex-induced oscillation suppression of the square column by placing a flexible plate behind it can reduce the dimensionless oscillation amplitude of the square column by up to 76.83%, the oscillation amplitude of the lift coefficient by 85.90%, and the average drag coefficient by 33.31%.

[0107] Therefore, the specific parameters of the vortex-induced oscillation suppression combined structure of the square column rear flexible plate designed according to the design method of the present invention are combined with Figure 1 As shown below: the side length of the square prism is D, the length of the flexible plate is L = 1.5D, and the flexibility is w. * =1.5.

[0108] During use, the specific parameters of the vortex-induced oscillation suppression structure of the rear flexible plate of the square column can be determined according to... Figure 1 The CFD design method used in this invention is adjusted to its optimal state, which can effectively suppress the vortex-induced oscillation of the square column.

[0109] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A design method for a combined structure for suppressing vortex-induced oscillations of a square column with a rear-mounted flexible plate, characterized in that, Includes the following steps: S1. Numerical simulation of vortex-induced oscillation of a single square cylinder in a flow path, specifically including the following steps: S1.1 Establish the structural and flow field analysis model of the square column; S1.

2. For the longitudinal motion of the square column, a structure-spring-damping model is established. Numerical experiments are conducted on the vortex-induced oscillation characteristics of a single square column under a set Reynolds number Re using computational fluid dynamics methods. The lift coefficient, drag coefficient, and dimensionless amplitude of the square column oscillation are calculated during the vortex-induced oscillation process. S2. Numerical simulation of vortex-induced oscillation of the combined structure of the central column and the flexible plate behind it in the flow path, specifically including the following steps: S2.

1. Select flexible plates of different lengths and flexibility to establish a structural and flow field analysis model for the combined structure of square column and rear flexible plate. S2.2 Calculate the vortex-induced oscillation motion of the combined structure model with a flexible plate behind the square column at the same Reynolds number Re. The lift coefficient, drag coefficient, and dimensionless amplitude of the combined structure oscillation are obtained through numerical experiments with flexible plates of different lengths and flexibility. The passive motion of the flexible plate is solved by the equation of motion of the flexible plate, which is shown in equation (7). Equation (8) represents the non-stretchable condition of the flexible plate. Where: The linear density of the flexible board, These are the position coordinates of the flexible plate. Label the coordinates of the Lagrange points. This represents the derivative of a physical quantity along the tangent to the plate. t For time, For tensile tension, For bending stiffness, The force exerted by the fluid on the plate; S3. Comparison of the kinematic and dynamic responses of vortex-induced oscillations between a single square column and a combination structure with a flexible plate behind the square column: Based on the calculation results of steps S1 and S2, the lift coefficient, drag coefficient, and dimensionless oscillation amplitude of a single square column and a combined structure of a column with a flexible plate at the rear with different lengths and flexibility are compared, and the vibration reduction and drag reduction effects of the combined structure with a flexible plate at the rear are analyzed. S4. Obtain the model parameters of the square column rear flexible plate combination structure with the best vibration reduction and drag reduction effect.

2. The design method of the square column vortex-induced oscillation suppression combined structure with a rear flexible plate according to claim 1, characterized in that, In step S1.2, the motion of the square column structure-spring-damped model in the flow field is controlled by the longitudinal motion equation (1). In the formula: Y is the dimensionless amplitude of the square column oscillation, Y = y / D, y is the longitudinal displacement of the square column, and D is the side length of the square column. , Let represent the dimensionless velocity and dimensionless acceleration of the square column, respectively. The damping ratio; To reduce speed, , Let be the natural frequency of the square prism. The fluid velocity; The lift coefficient, , Let the lift force be the force acting on the square column. For fluid density; is the mass ratio of the square column to the fluid, and m is the mass of the square column; Fluid motion is solved using the Navier-Stokes equations or the lattice Boltzmann method; the motion of viscous incompressible flow fields is solved using the Navier-Stokes equations: In the formula: For fluid density, For fluid pressure, Let t be the velocity vector and t be the time. The fluid dynamic viscosity coefficient, Force density; The lattice Boltzmann method involves discretely solving the lattice Boltzmann equations. The governing equations are as follows: In the formula: For time step, Represents the direction of the discrete lattice. The lattice velocity vector, Indicates the collision term and the external force term. Let be the density distribution function. , For time; The coupling between the square column and the flow field is performed using the immersion boundary method. The flow field is described using an Eulerian grid, and the structural boundary is described using a Lagrange grid. The effect of the complex boundary is transformed into a force source term on the Eulerian grid, and the Delta function in equations (5) and (6) is used. Converting force and velocity between Lagrange points and Euler points: Where: Here are the coordinates of the Euler point. Here are the coordinates of the Lagrange point. Label the coordinates of the Lagrange points. It is a velocity vector. This represents the force density at the corresponding time and location. The force acting on a solid boundary point; By coupling the oscillation equation of the square column as shown in equation (1) and the flow field equation as shown in equations (2)-(3) or (4), the lift coefficient C of the square column is calculated. L Drag coefficient C D The dimensionless amplitude Y of the square column oscillation.

3. The design method of the square column vortex-induced oscillation suppression combined structure with a rear flexible plate according to claim 2, characterized in that, In step S2.2, the solution for the oscillation and flow field of the square column in the combined structure of the square column and the flexible plate is the same as the numerical solution method for the vortex-induced oscillation of a single square column in S1.

2. The square column oscillation equation is shown in equation (1), and the flow field equation is shown in equation (2)-(3) or (4). The interaction between the square column rear flexible plate composite structure and the flow field is coupled using the immersion boundary method. The flow field is described using an Eulerian grid, and the structural boundary is described using a Lagrange grid. The effect of the complex boundary is transformed into a force source term on the Eulerian grid, and the Delta function in equations (5) and (6) is used. Convert force and velocity between Lagrange points and Euler points; By coupling the oscillation equation of the square column as shown in equation (1), the flow field equation as shown in equations (2)-(3) or (4), and the motion equation of the flexible plate as shown in equation (7), the lift coefficient of the square column rear flexible plate combined structure is calculated. drag coefficient The dimensionless amplitude of the combined structure oscillation .

4. The design method of the combined structure for suppressing vortex-induced oscillation of the rear flexible plate according to claim 1, characterized in that, In step S3, the average flow field is used to analyze the flow field characteristics. The average flow field is the flow field averaged over one oscillation cycle.

5. A combined structure for suppressing vortex-induced oscillations of a square column with a rear-mounted flexible plate, characterized in that, The structure includes a square column and a flexible plate disposed at the rear of the square column. The flexible plate is disposed perpendicular to the surface of the square column and is located at the midpoint of the side length of the cross-section of the square column. The square column vortex-induced oscillation suppression combined structure of the rear flexible plate is designed using the method described in any one of claims 1-4.

6. The combined structure for suppressing vortex-induced oscillations of a square column with a rear flexible plate according to claim 5, characterized in that, The flexible plate is hinged to the square column.

7. The combined structure for suppressing vortex-induced oscillations of a square column with a rear flexible plate according to claim 5, characterized in that, The flexible board is made of lightweight and corrosion-resistant materials.

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