Square column vortex-induced oscillation suppression combined structure with rear rigid plate and design method thereof

Abstract

The present application relates to a kind of rigid plate behind square column vortex-induced oscillation suppression combination structure and its design method, combination structure includes square column and the rigid plate of being set to square column rear;Its design method includes: S1 single square column vortex-induced oscillation numerical simulation in flow around;S2 square column vortex-induced oscillation numerical simulation of rigid plate combination structure behind in flow around;S3 compare single square column and square column rigid plate combination structure vortex-induced oscillation kinematics and dynamics response;S4 obtain the model parameter of square column rigid plate combination structure with the best vibration reduction, drag reduction effect.The present application can effectively reduce lift coefficient oscillation amplitude and the mean of resistance coefficient, and then reduce structural oscillation, realize vortex-induced oscillation suppression, the numerical analysis method for the rigid plate parameter design and optimization of square column behind proposed in the present application can more economically, efficiently and accurately design structure shape, size, not limit rigid flat material parameter, size, specific placement position, and the complexity of 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 rigid plate and its design method. Background Technology

[0002] Slender cylindrical structures are widely used in engineering applications, including columns in marine structures, bridges, and various high-rise buildings. When natural currents flow over a slender cylindrical structure, flow separation occurs at the structure's surface, generating periodically shedding vortices at the rear. The slender structure is thus subjected to periodically varying fluid forces and vibrates accordingly; this phenomenon is called vortex-induced oscillation. When the alternating force frequency of vortex-induced oscillation resonates with the structure's natural frequency, large-amplitude oscillations occur, causing severe damage to the slender cylindrical structure.

[0003] Vortex-induced oscillations in slender bodies are widespread in various engineering applications and can be extremely destructive. Therefore, flow control of vortex-induced oscillations is of great significance and application value. Techniques to weaken or suppress vortex-induced oscillations in cylindrical structures primarily involve controlling the periodic shedding of vortices to reduce alternating forces and thus suppress oscillations. For simple and easily achievable design goals in engineering applications, passive suppression methods such as increasing oscillation direction damping, changing cross-sectional shape, and adding vortex suppression devices have been widely used. These include fixed devices such as fairings, separation plates, and control rods to alter the flow behind the cylinder and suppress vortex shedding intensity. In addition, there are active control techniques that adjust the system's natural frequency; however, these techniques are complex and require real-time monitoring of nearby flow field information or external energy drive, limiting their application scenarios. The active and passive methods for suppressing vortex-induced oscillations described above are mainly applied to slender cylindrical structures. However, they are also widely used in rectangular cross-section cylindrical structures such as bridges and high-rise buildings.

[0004] The square prism cross-section is a typical cross-sectional form of slender prisms and has wide industrial applications. Both square and cylindrical prisms are blunt bodies, but compared to cylindrical prisms, the surface of a square prism is not as smoothly transitioned; instead, it has four sharp corners. This makes the flow boundary layer prone to separation at these corners, resulting in a more complex flow state. Consequently, methods for suppressing vortex-induced oscillations in square prisms differ somewhat from those for cylindrical prisms, and research on this topic is limited. Therefore, proposing a technique to suppress vortex-induced oscillations in square prisms has significant practical implications for engineering problems. Summary of the Invention

[0005] The technical problem to be solved by this invention is the issue of large-scale vortex-induced oscillations and forced vibration damage caused by slender rectangular cross-section cylinders (hereinafter referred to as rectangular cylinders) in a flow field. This invention proposes a combined structure and design method for suppressing vortex-induced oscillations of rectangular cylinders with a rear-mounted rigid plate. By adding a rigid planar baffle (hereinafter referred to as a rigid plate) behind the rectangular cylinder, the boundary layer separation characteristics of the flow field behind the cylinder and the shedding process of the vortex system are altered, thereby suppressing vortex-induced oscillations. Through reasonable design of the rigid plate behind the rectangular cylinder, the vortex system originally generated by flow separation can be impeded by the added plate, suppressing the interaction of the vortex system behind the rectangular cylinder, weakening the alternating force intensity of the fluid acting on the rectangular cylinder, and thus achieving the suppression of vortex-induced oscillations of the rectangular cylinder.

[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-mounted rigid plate includes a square column and a rigid plate of uniform thickness disposed at the rear of the square column. The rigid 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 rigid plate is rigidly connected to the square column.

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

[0010] Accordingly, the present invention also proposes a design method for the above-mentioned combined structure for suppressing vortex-induced oscillation of a square column with a rear rigid 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 a combined structure of a central column and a rear rigid plate in flow path, specifically including the following steps:

[0015] S2.1. Select rigid plates of different lengths and typical dimensions of a single square column to establish a structural and flow field analysis model for the combined structure of a square column and a rigid plate.

[0016] S2.2 Calculate the vortex-induced oscillation motion of the combined structure model with a rigid plate at the rear of the square column under the same Reynolds number Re. The lift coefficient, drag coefficient and dimensionless amplitude of the combined structure oscillation are obtained by numerical experiment under rigid plates of different lengths at the rear.

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

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

[0019] S4. Obtain the model parameters of the square column rear rigid 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 system in the flow field is controlled by the longitudinal motion equation (1).

[0021]

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

[0023] C y The lift coefficient, F y The lift force acting on the square column;

[0024] ζ y The damping ratio;

[0025] U y To reduce the speed, U y =U ∞ / f n D, f n The natural frequency of the square prism;

[0026] n y The mass ratio of the square prisms, n y =m / ρ f D 2 m is the mass of the square prism;

[0027] Damping ratio ζ y and reduction speed U y Substituting the longitudinal motion equation yields the specific square column motion equation;

[0028] 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:

[0029]

[0030]

[0031] In the formula: ρ f Where is the fluid density, p is the fluid pressure, u represents the velocity vector, t represents time, μ is the dynamic viscosity coefficient, and f is the force density;

[0032] The lattice Boltzmann method involves discretely solving the lattice Boltzmann equations. The governing equations are as follows:

[0033] f α (x+e α δ t ,t+δ t )=f α (x,t)+Φ α (4)

[0034] 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.

[0035] The interaction between the square column and the flow field is coupled using the immersed 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 force and velocity between the Lagrange point and the Eulerian point are converted using the Delta function δ(xX(s,t)) in Equations (5) and (6).

[0036]

[0037]

[0038] 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.

[0039] 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. y Drag coefficient C x The dimensionless amplitude y of the square column oscillation* ,in F x ρ is the resistance force experienced by the square prism. f The fluid density is given.

[0040] In the above method, in step S2.2, the solution for the oscillation of the square column and the flow field in the combined structure of square column with rigid plate is the same as the numerical solution method for the vortex-induced oscillation of a single square column around the flow in S1.2. The oscillation equation of the square column is shown in equation (1), and the flow field equation is shown in equation (2)-(3) or (4). The rigid plate oscillates with the square column without relative displacement. The coupling between the combined structure of square column with rigid plate and the flow field adopts the immersed boundary method, and the force and velocity conversion between the Lagrange point and the Eulerian point is performed as shown in equation (5) and (6). By coupling the solution of the oscillation equation of the square column as shown in equation (1) and the flow field equation as shown in equation (2)-(3) or (4), the lift coefficient C′ of the combined structure of square column with rigid plate is calculated. y Drag coefficient C′ x The dimensionless amplitude y of the combined structure oscillation * ′.

[0041] 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.

[0042] The beneficial effects of this invention are as follows:

[0043] 1. The vortex-induced oscillation suppression combined structure with a square column rear-mounted rigid plate designed in this invention can effectively reduce the amplitude of lift oscillations and the average drag, thereby reducing structural oscillations and achieving vortex-induced oscillation suppression. Simultaneously, the plate structure is easy to manufacture and has a simple structure, making it more suitable for practical applications in engineering fields compared to active control methods for suppressing vortex-induced oscillations. The numerical analysis method for parameter design and optimization of the square column rear-mounted rigid plate proposed in this invention can design the structural shape and size more economically, efficiently, and accurately, regardless of the rigid plate material parameters, dimensions, specific placement location, or the complexity of the flow field environment.

[0044] 2. In the optimal design of this invention, the dimensionless amplitude of the square column oscillation in the vortex-induced oscillation suppression structure with a rigid plate at the rear of the square column can be reduced by up to 75%, the oscillation amplitude of the lift coefficient can be reduced by 85%, and the average drag coefficient can be reduced by 34%. During use, the specific parameters of the vortex-induced oscillation suppression structure with a rigid plate at the rear of the square column can be adjusted to the optimal state according to the CFD design method used in this invention, which can effectively suppress the vortex-induced oscillation of the square column.

[0045] 3. The structure designed according to the present invention has a wide range of applications and can be used in bridge engineering, marine engineering and other fields. Attached Figure Description

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0047] Figure 1 This is a schematic diagram of the combined structure for suppressing vortex-induced oscillations of the rear rigid plate of the present invention;

[0048] Figure 2 This is the structure-spring-damping model of the square column established in the design method of this invention;

[0049] Figure 3 This is a schematic diagram of the combined structure for suppressing vortex-induced oscillations of the square column with a rear rigid plate in the flow field of the present invention.

[0050] Figure 4a This is the average flow field vorticity cloud diagram of a single square column in an embodiment of the present invention;

[0051] Figure 4b This is the average flow field pressure cloud diagram of a single square column in an embodiment of the present invention;

[0052] Figure 5a This is the average flow field vorticity cloud diagram for the square column rear plate D in this embodiment of the invention;

[0053] Figure 5b This is the average flow field pressure cloud diagram for the square column rear plate D in this embodiment of the invention. Detailed Implementation

[0054] 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.

[0055] like Figure 1 As shown, this invention proposes a combined structure for suppressing vortex-induced oscillations of a square column with a rear-mounted rigid plate. The structure includes a square column 11 and a rigid plate 12 of uniform thickness disposed at the rear of the square column. The square column and the rigid plate are rigidly connected at right angles. The rigid 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 rigid plate and the square column form a combined structure. The square column is a solid rigid body, typically constructed using lightweight, corrosion-resistant materials, and its deformation under alternating forces is negligible. The column's cross-sectional shape is square with a side length of D, and the mass ratio of the square column to n... y =2. Rigid plates are solid, rigid bodies, typically constructed using lightweight, corrosion-resistant materials. Their deformation under alternating forces is negligible. The cross-sectional shape of a rigid plate is rectangular, with a length of 0.5D-1.5D. Its width is much smaller than that of a square column, and therefore can be ignored.

[0056] Meanwhile, the rigid plate and the square column are rigidly connected to form a composite structure with a right-angle transition at the connection. The rigid plate oscillates with the square column without relative displacement, and the deformation of the entire composite structure under the action of alternating force is negligible.

[0057] In the design of the combined structure for suppressing vortex-induced oscillations, rigid plates of different lengths were selected for numerical experiments and comparative analysis to determine their structural parameters.

[0058] Accordingly, this invention also proposes a design method for the aforementioned combined structure of a square column with a rear-mounted rigid 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-mounted rigid plate. The lift coefficient, drag coefficient, and oscillation amplitude of the structures are compared, and the structural parameters of the combined structure with the square column and rear-mounted rigid plate that achieves the best vortex-induced oscillation suppression effect are selected. This design method specifically includes the following steps:

[0059] S1. Numerical simulation of vortex-induced oscillation of a single square cylinder in a flow path, specifically including the following steps:

[0060] S1.1 Establish the structural and flow field analysis model of the square column. The geometric model of the oscillating square column in the flow field is performed, and the size of the computational domain is determined based on the dimensions of the square column. On this basis, the structural and flow field analysis model of the oscillating square column is established.

[0061] S1.2 Since the vortex-induced oscillation of the square column is mainly longitudinal (perpendicular to the flow direction), only the longitudinal motion of the square column 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... drag coefficient F y F is the lift force experienced by the square column during vortex-induced oscillation. x U represents the resistance encountered during the vortex-induced oscillation of a square column. ∞ ρ is the fluid velocity. f The fluid density is given. The dimensionless amplitude y of the square columnar oscillation is given. * =y / D, which is the ratio of the longitudinal displacement y of the square prism to the side length D of the square prism. Reynolds number Re = ρ f U ∞ D / μ, ρ f U is the fluid density, U∞ is the fluid velocity, D is the side length of the square prism, and μ is the fluid dynamic viscosity.

[0062] The established structure-spring-damping model is as follows: Figure 2 As shown, its motion in the flow field is controlled by the longitudinal motion equation (1):

[0063]

[0064] In the formula: y * The dimensionless amplitude of the square column oscillation, y * = y / D, where y is the longitudinal displacement of the square prism and D is the side length of the square prism. Let represent the dimensionless velocity and dimensionless acceleration of the square column, respectively.

[0065] F is the lift coefficient. y Let ρ be the lift force acting on the square prism. f For fluid density;

[0066] ζ y The damping ratio;

[0067] U y =U ∞ / f n D is the reduced velocity, f n U is the natural frequency of the square column, U∞ is the fluid velocity; n y =m / ρ f D 2 is the mass ratio of the square prisms, and m is the mass of the square prism;

[0068] Damping ratio ζ y and reduction speed U y Substituting the longitudinal motion equations yields the motion equations for the specific square column.

[0069] 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:

[0070]

[0071]

[0072] In the formula: ρ f ρ is the fluid density, p is the fluid pressure, u represents the velocity vector, t represents time, μ is the dynamic viscosity coefficient, and f is the force density.

[0073] The lattice Boltzmann method involves discretely solving the lattice Boltzmann equations. The governing equations are as follows:

[0074] f α (x+e α δ t ,t+δ t )=f α (x,t)+Φ α (4)

[0075] 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. αf 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.

[0076] The interaction between the square column and the flow field is coupled using the immersed 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 force and velocity between the Lagrange point and the Eulerian point are converted using the Delta function δ(xX(s,t)) in Equations (5) and (6).

[0077]

[0078]

[0079] 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.

[0080] 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. y Drag coefficient C x The dimensionless amplitude y of the square column oscillation * Since the forces acting on the square column are periodic, after comprehensive consideration, the oscillation amplitude of the square column is analyzed by the dimensionless amplitude of the oscillation, and the hydrodynamic forces acting on the square column are analyzed by the oscillation amplitude of the lift coefficient and the average value of the drag coefficient.

[0081] In this embodiment, for Re = 150, the mass ratio n y =2, reduced velocity U y Flow around a square cylinder at a value of 5, dimensionless amplitude y of oscillation of a single square cylinder. * The lift coefficient is 0.46, the lift coefficient oscillation amplitude is 1.963, and the drag coefficient average is 2.338.

[0082] S2. Numerical simulation of vortex-induced oscillation of a combined structure of a central column and a rear rigid plate in flow path, specifically including the following steps:

[0083] S2.1. Establish structural and flow field analysis models for the combined structure of a square column and a rear-mounted rigid plate using rigid plates of different lengths. For example... Figure 3 As shown, based on the dimensions of the square column and the computational domain in step S1, rigid plates of different lengths are designed and placed behind the square column. Based on this, a structural flow field analysis model of the combined structure of the square column and the rear-mounted rigid plate is established. It should be noted that... Figure 3The arrow on the left indicates the direction of free flow, and the dashed outline indicates the position of the forced displacement of the combined structure of the square column and rigid plate after the flow field.

[0084] S2.2 Calculate the vortex-induced oscillation motion of the combined structure model with a rigid 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 lengths of rigid plates behind the column.

[0085] The solution for the oscillation of the square column and the flow field in the combined structure of square column with rigid plate is the same as the numerical solution method for the vortex-induced oscillation of a single square column around the flow 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 rigid plate oscillates with the square column without relative displacement. The coupling between the combined structure of square column with rigid plate and the flow field is performed by the immersion boundary method, and the force and velocity between the Lagrange point and the Euler point are converted as shown in Equations (5) and (6).

[0086] 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 with a rigid plate at the rear is calculated. y Drag coefficient C x v, dimensionless amplitude of the combined structural oscillation y * 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 a rigid plate at the rear, 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 in the combined structure with a rigid plate at the rear.

[0087] In this embodiment, rigid plates of different lengths were designed. A high-fidelity numerical simulation was performed on the model of the combined structure of multiple square columns with rear-mounted rigid plates, following the method described in step S2 above. Then, the oscillation amplitude of the lift coefficient, the mean drag coefficient, and the dimensionless vibration amplitude of the columns below the rear-mounted rigid plates of different lengths were statistically analyzed.

[0088] In the design parameters of the rigid plate, the length L is taken as: 0.5D, 1.0D, 1.5D.

[0089] In this embodiment, with a Reynolds number Re = 150, the dimensionless amplitude and lift coefficient vibration amplitude results of the system with rigid plates of different lengths are as follows:

[0090] Table 1. Structure of different scheme combinations

[0091]

[0092] S3. Compare the kinematic and dynamic responses of vortex-induced oscillations between a single square column and a combination of square columns with a rigid plate behind them.

[0093] 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 rigid plate behind the column of different plate lengths are compared, and the vibration reduction and drag reduction effects of the composite structure with a rigid plate behind the column are analyzed.

[0094] The flow field characteristics are analyzed using an average flow field analysis method, where the average flow field is the flow field averaged over one oscillation cycle. This is achieved through the time-averaged vorticity contour plot of the oscillation cycle. Figure 4a It can be seen that the vorticity distribution at the rear of a single square column is relatively wide, and the corresponding vibration amplitude of the square column is also very large (the upper and lower dotted lines in the figure represent the oscillation amplitude of the square column), and the corresponding time-averaged pressure distribution ( Figure 4b The data shows a large low-pressure area behind the square column, resulting in significant pressure drag and lift on each column, leading to large vortex-induced oscillations. On the other hand, by employing the rear-mounted rigid plate structure proposed in this invention, the rear rigid plate effectively reduces the vortex shedding intensity directly behind the square column and prevents the vortex from crossing the centerline of the square column behind it, thus greatly reducing the width of the rear vortex. Figure 5a This increases the pressure at the rear of the square column, effectively reducing the pressure difference between the upper / lower and front / rear sides, thereby reducing the average drag coefficient and the amplitude of the lift coefficient. Figures 5a-5b The upper and lower dashed boxes represent the oscillation amplitude of the rear rigid plate-square column composite structure when environmental parameters are the same. Figures 4a-4b The comparison shows a significant reduction in structural oscillation amplitude, effectively suppressing vortex-induced oscillation 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 rigid plate behind the square column significantly reduces the dimensionless amplitude of the oscillation, the lift coefficient oscillation amplitude, and the mean drag coefficient. Therefore, the addition of a rigid plate behind the square column demonstrates excellent vibration and drag reduction effects.

[0095] S4. Obtain the model parameters of the square column rear rigid plate combination structure with the best vibration reduction and drag reduction effect of the vortex-induced oscillation suppression structure.

[0096] After placing a rigid plate behind the square column, the dimensionless amplitude of the oscillation, the oscillation amplitude of the lift coefficient, and the mean value of the drag coefficient of the combined structure are all significantly reduced compared to a single square column. The vibration reduction and drag reduction effects vary depending on the length of the rigid plate. Numerical experimental results show that, within the current design parameter range, the vibration reduction and drag reduction effect is optimal at L = 1.0D. In the optimal scheme, the dimensionless amplitude of the square column oscillation can be reduced by up to 75%, the oscillation amplitude of the lift coefficient by 85%, and the mean drag coefficient by 34% by placing a rigid plate behind the square column.

[0097] Therefore, the specific parameters of the vortex-induced oscillation suppression combined structure with the rear rigid plate of the square column designed according to the design method of this invention are combined with Figure 1 As shown below: The side length of the square column is D, and the length of the rigid plate is L = 1.0D.

[0098] In the use of this invention, the specific parameters of the vortex-induced oscillation suppression structure of the rear rigid plate of the square column can be determined according to... Figure 1 The computational fluid dynamics (CFD) used in this invention, when optimized, can effectively suppress vortex-induced oscillations of the square column. The embodiments of the invention have been described above with reference to the accompanying drawings. However, the invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art, under the guidance of this invention, can make many modifications without departing from the spirit and scope of the claims, and all such modifications are within the protection scope of this invention.

Claims

1. A design method for a combined structure for suppressing vortex-induced oscillations of a square column with a rear-mounted rigid 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. The lift coefficient, drag coefficient, and dimensionless amplitude of the square column oscillation during the vortex-induced oscillation process are calculated. The motion of the structure-spring-damping model system of the square column in the flow field is controlled by the longitudinal motion equation (1). In the formula: The amplitude of the square column oscillation is dimensionless. = y / D , y This represents the longitudinal displacement of the square column. , Let represent the dimensionless velocity and dimensionless acceleration of the square column, respectively. The lift coefficient, , The lift force acting on the square column; The damping ratio; To reduce the speed, , The natural frequency of the square prism; The mass ratio of the square column. , m The mass of the square column; Damping ratio and reduction speed Substituting the longitudinal motion equation yields the specific square column motion equation; S2. Numerical simulation of vortex-induced oscillation of a combined structure of a central column and a rear rigid plate in flow path, specifically including the following steps: S2.

1. Select rigid plates of different lengths and typical dimensions of a single square column to establish a structural and flow field analysis model for the combined structure of a square column and a rigid plate. S2.2 Calculate the vortex-induced oscillation motion of the combined structure model with a rigid 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 experiment under rigid plates of different lengths behind the column. S3. Comparison of the kinematic and dynamic responses of vortex-induced oscillations between a single square column and a combined structure with a square column and a rigid plate behind it: Based on the calculation results of steps S1 and S2, the lift coefficient, drag coefficient, and dimensionless amplitude of square column oscillation are compared between a single square column and a combined structure of a square column with a rigid plate at the rear for different lengths, and the vibration reduction and drag reduction effects of the combined structure with a rigid plate at the rear are analyzed. S4. Obtain the model parameters of the square column rear rigid plate combination structure with the best vibration reduction and drag reduction effect.

2. The design method of the combined structure for suppressing vortex-induced oscillation of a square column with a rear rigid plate according to claim 1, characterized in that, In step S1.2, 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, Represents the velocity vector. t Indicates time, The dynamic viscosity coefficient is... 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. , t For time; The interaction between the prism 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. Converting force and velocity between Lagrange points and Euler points: In the formula: 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 solution of 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 of the square column can be calculated. drag coefficient Dimensionless amplitude of square column oscillation ,in , The resistance force experienced by the square column, The fluid density is given.

3. The design method of the combined structure for suppressing vortex-induced oscillation of a square column with a rear rigid plate according to claim 2, characterized in that, In step S2.2, the solution for the oscillation of the square column and the flow field in the combined structure of square column and rigid 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 rigid plate oscillates with the square column without relative displacement. The coupling between the combined structure of square column and rigid plate and the flow field is achieved by the immersion boundary method and by the Delta function in equations (5) and (6). Perform force and velocity conversion between Lagrange points and Euler points; 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 of the combined structure of the square column and the rigid plate is calculated. drag coefficient Dimensionless amplitude of combined structure oscillation .

4. The design method of the combined structure for suppressing vortex-induced oscillation of a square column with a rear rigid 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 rigid plate, characterized in that, The structure includes a square column and a rigid plate of uniform thickness disposed at the rear of the square column. The rigid 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 with the rear rigid plate is designed using the method described in any one of claims 1-4.

6. The combined structure for suppressing vortex-induced oscillation of a square column with a rear rigid plate according to claim 5, characterized in that, The rigid plate is rigidly connected to the square column.

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

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