A numerical simulation method for a vortex-induced vibration tidal current power generation device

Abstract

This invention discloses a numerical simulation method for a vortex-induced vibration tidal current power generation device, comprising: creating a geometric model of the column structure and the external flow field computational domain; dividing the column component mesh and the background mesh of the external flow field computational domain, and using overlapping mesh technology to transfer flow field information between the two sets of meshes; establishing a structural dynamics model of the vortex-induced vibration of an elastically supported rigid column under the action of electromagnetic force and nonlinear restoring force; combining the computational fluid dynamics model with the structural dynamics model to perform fluid-structure interaction numerical calculations; and post-processing the calculation data after the simulation reaches its termination time. This invention considers electromagnetic force and nonlinear restoring force, calculating the displacement, velocity, acceleration, fluid forces acting on the column, and energy conversion efficiency, thereby enabling the prediction of the column's vortex-induced vibration response and energy conversion characteristics, providing a more accurate and reliable method for the analysis and design of vortex-induced vibration tidal current power generation devices.

Description

Technical Field

[0001] This invention relates to the technical field of fluid-structure interaction numerical simulation, and in particular to a numerical simulation method for a vortex-induced vibration tidal power generation device. Background Technology

[0002] When fluid flows over a blunt body, it generates alternating vortices on both sides, subjecting the structure to periodically changing fluid forces. When the structure is flexible or elastically supported, this results in reciprocating motion, which in turn alters the fluid flow pattern, thus changing the fluid forces acting on the structure's surface. This fluid-structure interaction phenomenon is called vortex-induced vibration. When the vortex shedding frequency approaches the structure's natural frequency, frequency locking may occur, inducing large-amplitude vibrations. Vortex-induced vibration is one of the main causes of fatigue failure in marine engineering structures. On the other hand, vortex-induced vibration possesses self-excited and self-sustaining characteristics, making it suitable for the development and utilization of tidal energy. The development of vortex-induced tidal energy power generation technology and the fabrication of vortex-induced tidal energy power generation devices are gradually becoming research hotspots.

[0003] Current research on vortex-induced tidal current power generation devices typically simplifies the electromagnetic force of the generator to a damping force with a constant damping coefficient. However, in actual engineering, the electromagnetic force of the generator is a damping force with a variable damping coefficient. Existing research struggles to reflect the performance of vortex-induced tidal current power generation devices under real-world operating conditions, resulting in low accuracy and reliability in predicting their performance. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem of improving the accuracy and reliability of vortex-induced vibration tidal power generation devices.

[0005] Therefore, this invention proposes a numerical simulation method for a vortex-induced vibration tidal current power generation device, comprising the following steps:

[0006] S1: Create the geometric model of the column structure and the geometric model of the external flow field calculation domain in which the column structure is located;

[0007] S2: Mesh the computational domain of the flow field near the column structure and the computational domain of the external flow field to obtain the column component mesh and the background mesh of the external flow field computational domain. The flow field information between the column component mesh and the background mesh of the external flow field computational domain is transferred through the overlapping mesh technique.

[0008] S3: Establish a structural dynamics model of vortex-induced vibration of a column under the action of electromagnetic force and nonlinear restoring force;

[0009] S4: Combine the computational fluid dynamics model with the structural dynamics model to perform fluid-structure interaction numerical calculations;

[0010] S5: After the simulation reaches its termination time, the calculated data is post-processed to obtain the response and energy conversion characteristics of the column's vortex-induced vibration.

[0011] In some embodiments of the present invention, in step S1, the geometric model of the external flow field calculation domain is established based on the geometric dimensions of the cylindrical structure. The external flow field calculation domain is a cuboid region that surrounds the cylindrical structure. The upstream of the cylindrical structure is a free flow region, and the downstream is a wake region where vortices fall off.

[0012] In some embodiments of the present invention, in step S2, the column component mesh adopts an O-type body-fitting mesh division strategy, and the component mesh region is a cylinder concentric with the column structure; when dividing the background mesh of the external flow field calculation domain, the mesh near the column and the wake region is densified; both the column component mesh and the background mesh of the external flow field calculation domain use structured meshes, and overlapping mesh technology is used to punch holes in the mesh inside the column, identify the overlapping meshes that do not participate in the calculation, and ignore them during the calculation, and interpolate through the edge mesh, so that the flow field information can be transferred between the column component mesh and the background mesh of the external flow field calculation domain.

[0013] In some embodiments of the present invention, the height of the first layer of mesh along the radial direction of the column surface in step S2 satisfies y. + ≤1, the mesh sizes in the flow direction and span direction respectively satisfy 50≤x + ≤150, 15≤z + ≤40, interpolation of flow field information between grids is performed using a distance weighting function:

[0014]

[0015] Where: φ r The flow field variables at the acceptor unit are M and φ is the number of donor units. i d represents the flow field variable at donor unit i. i This represents the distance between donor unit i and recipient unit i.

[0016] In some embodiments of the present invention, step S3 further includes: using computational fluid dynamics, the flow field around the column is solved using the unsteady incompressible Navier-Stokes equations, and the turbulence is solved using a large eddy simulation local eddy viscosity wall adaptive model.

[0017] In some embodiments of the present invention, in step S3, the discretization of the fluid control equations employs the finite volume method, utilizes the PIMPLE algorithm to handle pressure-velocity coupling, discretizes the transient terms using an implicit second-order backward scheme, and discretizes the convection terms using a second-order linear upwind stable transport scheme. An adaptive time step is selected to satisfy the Courant-Friedrichs-Lewy condition, maximizing the Courant number Co. max <1.

[0018] In some embodiments of the present invention, step S3 further includes determining initial conditions and boundary conditions, initializing calculation parameters, and conducting numerical simulation; calculating the fluid force on the column by integrating the pressure and viscous force acting on the surface of the column, and incorporating the fluid force into the structural dynamics model.

[0019] In some embodiments of the present invention, the structural dynamics model in step S3 is as follows:

[0020]

[0021] In the formula: m is the mass of the vibrating system, b represents the structural damping coefficient of the system, and b em F represents the electromagnetic damping coefficient of the system, k is the linear stiffness of the system, c is the nonlinear stiffness, and F is the electromagnetic damping coefficient of the system. y The force exerted on the column is the transverse fluid force. Vortex-induced tidal current power generation devices often use permanent magnet linear generators for energy conversion. The electromagnetic force of a permanent magnet linear generator is essentially a damping force with a variable damping coefficient. According to Faraday's law of electromagnetic induction and the single magnetic dipole approximation, the electromagnetic damping coefficient b... em It can be represented as:

[0022]

[0023] Where a represents the coil radius, μ is the magnetic dipole moment, N represents the number of coil turns, L represents the coil length, and R is the load resistance; the boundary conditions are determined as follows: the inlet boundary adopts the velocity inlet boundary condition, the outlet boundary adopts the pressure outlet boundary condition, the lateral boundary condition adopts the free slip boundary condition, the surface of the cylinder adopts the no slip boundary condition, and the spanwise boundary adopts the periodic boundary condition; the cylinder is initially in a stationary state.

[0024] In some embodiments of the present invention, in step S4, the structural dynamics model of vortex-induced vibration under the action of electromagnetic force and nonlinear restoring force is solved by the Newmark numerical integration method, and the displacement, velocity and acceleration of the column vibration can be obtained; it is determined whether the termination time has been reached. If the termination time has not been reached, the flow field mesh is updated, and steps S3-S4 are repeated on the updated mesh to solve for the next time step.

[0025] In some embodiments of the present invention, in step S4, the Newmark method used relates the displacement, velocity, and deceleration from step n to step n+1 in the following manner:

[0026]

[0027]

[0028] By selecting suitable integration parameters β = 1 / 4 and γ = 1 / 2, the numerical integration method is unconditionally stable and has second-order accuracy.

[0029] In some embodiments of the present invention, the post-processing in step S5 includes: extracting the displacement, velocity response and fluid force of the column; obtaining the energy conversion power of the column by multiplying the electromagnetic force and the vibration velocity; calculating the energy conversion efficiency of the device by using the ratio of the time-averaged power to the total energy contained in the fluid swept by the column; and using CFD flow field visualization technology to study the three-dimensional wake vortex structure of the column and the vortex shedding modes of each spanwise section.

[0030] In some embodiments of the present invention, the energy conversion efficiency of the column vortex-induced vibration in step S5 is calculated using the following formula:

[0031]

[0032] in, Here, ρ represents the time-averaged power, U represents the fluid density, and A represents the free-flow velocity. y The maximum amplitude of the column vibration is given by λ2, where D is the diameter of the cylinder and H represents the spanwise length of the cylinder. The three-dimensional wake structure of the column is identified using the λ2 criterion, and the vortex discharge mode of each spanwise section is represented by the vorticity field.

[0033] In some embodiments of the present invention, in step S1, the distance between the inlet boundary of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 10 times the column diameter, the distance between the two lateral boundaries of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 10 times the column diameter, the distance between the outlet boundary of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 30 times the column diameter, and the ratio of the spanwise length to the column diameter is determined according to the column length of the vortex-induced vibration tidal power generation device to be simulated.

[0034] The present invention also provides a vortex-induced vibration tidal current power generation device, including a processor and a memory, wherein the memory stores a computer program that can be executed by the processor to implement the method described in any of the above.

[0035] The present invention also provides a computer-readable medium storing a computer program that can be read to implement the methods described in any of the preceding claims.

[0036] The present invention has the following beneficial effects:

[0037] This invention proposes a coupled calculation method based on a computational fluid dynamics model using the finite volume method and a structural dynamics model considering electromagnetic forces and nonlinear restoring forces. By considering electromagnetic forces and nonlinear restoring forces, the fluid dynamics model is combined with the structural dynamics model to perform fluid-structure interaction numerical calculations of vortex-induced vibration of a column. This method can obtain the displacement, velocity, acceleration, fluid forces acting on the column, and energy conversion efficiency, thereby enabling the prediction of the column's vortex-induced vibration response and energy conversion characteristics. This invention also establishes a high-fidelity numerical model of vortex-induced vibration of a three-dimensional column structure under the action of electromagnetic forces and nonlinear restoring forces, improving the accuracy and reliability of predicting the performance of vortex-induced vibration tidal power generation devices.

[0038] In some embodiments of the present invention, the electromagnetic force of a permanent magnet linear generator is simulated based on Faraday's law of electromagnetic induction and the single magnetic dipole approximation, which can reflect the performance of the eddy-induced vibration tidal power generation device under real working conditions.

[0039] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0040] Appendix Figure 1 This is a basic flowchart of the numerical simulation method for the vortex-induced vibration tidal current power generation device in this embodiment of the invention;

[0041] Appendix Figure 2 This is a schematic diagram of the column vortex-induced vibration model in an embodiment of the present invention;

[0042] Appendix Figure 3a This is a schematic diagram of the flow field computational domain mesh in an embodiment of the present invention;

[0043] Appendix Figure 3b This is a schematic diagram of the grid division around the column in an embodiment of the present invention;

[0044] Appendix Figure 4a This is a time-history curve of the column vibration displacement in an embodiment of the present invention;

[0045] Appendix Figure 4b This is a time-history curve of the energy conversion power of the column in an embodiment of the present invention;

[0046] Appendix Figure 5a This is a three-dimensional tail vortex structure diagram of the column vortex-induced vibration in an embodiment of the present invention;

[0047] Appendix Figure 5b This is a diagram of the vortex discharge mode of the 0m spanwise section of the column in an embodiment of the present invention.

[0048] Appendix Figure 5cThis is a diagram of the vortex discharge mode of the 0.0508m spanwise section of the column in an embodiment of the present invention.

[0049] Appendix Figure 5d This is a diagram of the vortex discharge mode of the 0.1016m spanwise section of the column in an embodiment of the present invention.

[0050] Appendix Figure 5e This is a diagram of the vortex discharge mode of the 0.1524m spanwise section of the column in an embodiment of the present invention.

[0051] Appendix Figure 5f This is a diagram of the vortex discharge mode of the 0.2032m spanwise section of the column in an embodiment of the present invention;

[0052] Appendix Figure 5g This is a diagram of the vortex discharge mode of the column spanwise section at 0.254m in an embodiment of the present invention. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0054] It should be noted that the directional terms such as left, right, up, down, top, and bottom used in this embodiment are only relative concepts or are based on the normal use of the product, and should not be considered as restrictive.

[0055] Nonlinear restoring forces can alter the vibration intensity and parameter range corresponding to stable vibration of a system, potentially improving the performance of vortex-induced vibration tidal power generation devices. However, research on the effect of nonlinear restoring forces on the response and energy conversion characteristics of vortex-induced vibration systems is relatively lacking. Studies considering the combined effects of electromagnetic and nonlinear restoring forces on the vortex-induced vibration of elastically supported columns are even rarer.

[0056] In recent years, with the continuous improvement of computer hardware performance and the rapid development of numerical simulation technology, the use of numerical simulation methods to solve practical engineering problems has received widespread attention. Previously, scholars both domestically and internationally have conducted extensive numerical studies on various fluid-structure interaction problems and made detailed comparisons with relevant experimental data. The errors have been controlled within acceptable limits, verifying the reliability of numerical simulation methods in studying complex fluid-structure interaction problems. Therefore, a numerical simulation method for a vortex-induced vibration tidal power generation device under the action of electromagnetic force and nonlinear restoring force is proposed.

[0057] The following embodiments of the present invention relate to the technical field of fluid-structure interaction numerical simulation, and particularly to a coupled calculation method for a computational fluid dynamics model based on the finite volume method and a structural dynamics model considering the effects of electromagnetic forces and nonlinear restoring forces.

[0058] The following embodiments of the present invention propose a numerical simulation method for a vortex-induced vibration tidal power generation device under the action of electromagnetic force and nonlinear restoring force in the field of fluid-structure interaction numerical simulation: A three-dimensional model of the cylindrical structure and the external flow field computational domain is created; the component mesh and background mesh are divided, and overlapping mesh technology is used to realize the transfer of flow field information between meshes; the unsteady incompressible Navier-Stokes equations and the large eddy simulation turbulence model are solved; a vortex-induced vibration structural dynamic model is established under the action of electromagnetic force and nonlinear restoring force, and coupled simulation is carried out, incorporating the calculated fluid forces into the structural dynamic model; the displacement, velocity, and acceleration of the cylinder are obtained by solving the structural dynamic model, and the flow field mesh is updated to continue the solution; after the termination time is reached, post-processing of the calculation results is performed. This embodiment can more realistically reflect the electromagnetic force experienced by the vortex-induced vibration tidal power generation device, and the simulation of nonlinear restoring force can be used for performance optimization and improvement of the vortex-induced vibration tidal power generation device.

[0059] The purpose of the following embodiments of the present invention is to provide a numerical simulation method for a vortex-induced vibration tidal power generation device under the action of electromagnetic force and nonlinear restoring force, so as to predict the vortex-induced vibration response and energy conversion characteristics of a column structure under the combined action of electromagnetic force and nonlinear restoring force, and lay the foundation for researching and improving the performance of vortex-induced vibration tidal power generation devices.

[0060] The technical solution adopted in the following embodiments of the present invention is: a numerical simulation method for a vortex-induced vibration tidal current power generation device under the action of electromagnetic force and nonlinear restoring force, such as... Figure 1 As shown, it includes the following steps:

[0061] Step 1: Create a three-dimensional geometric model of the column structure. Based on the geometric dimensions of the column structure, establish a three-dimensional external flow field computational domain model in which it is located. The three-dimensional external flow field computational domain is a cuboid region that surrounds the column structure. The upstream of the column structure is the free flow region, and the downstream is the wake region where vortex shedding occurs.

[0062] Step 2: The column component mesh is generated by meshing the flow field computational domain near the column structure. The column component mesh adopts an O-type body-fitting meshing strategy, and the component mesh region is a cylinder concentric with the column structure. Then, the external flow field background mesh is generated. The mesh obtained after meshing the external flow field computational domain is the background mesh of the external flow field computational domain. The mesh near the column and the wake region is refined. Both the component mesh and the background mesh use structured meshes and overlapping mesh technology. Holes are "cut" in the mesh located inside the column to identify the overlapping meshes that do not participate in the calculation and ignore them during the calculation. Interpolation is performed through the edge mesh to realize the transfer of flow field information between the two sets of meshes.

[0063] Step 3: Using computational fluid dynamics (CFD), the flow field around the cylinder is solved using the unsteady incompressible Navier-Stokes (NS) equations, and the turbulence is solved using the large eddy simulation (LES) wall-adapting localeddy-viscosity (WALE) model.

[0064] Step 4: Establish a structural dynamics model of vortex-induced vibration under the action of electromagnetic force and nonlinear restoring force, and couple it with the computational fluid dynamics model; determine the initial conditions and boundary conditions, initialize the calculation parameters, and carry out numerical simulation; integrate the pressure and viscous force acting on the surface of the column to obtain the fluid force on the column, and input the obtained fluid force into the established structural dynamics model;

[0065] Step 5: Solve the structural dynamics model of vortex-induced vibration under electromagnetic force and nonlinear restoring force using Newmark numerical integration to obtain the displacement, velocity and acceleration of the column vibration; determine whether the termination time has been reached. If the termination time has not been reached, update the flow field mesh. The flow field mesh is a whole, including the column component mesh and the background mesh of the external flow field computational domain, and return to step 3. Repeat steps 3-5 on the updated mesh to solve for the next time step.

[0066] Step 6: After the simulation reaches the termination time, the calculated data is post-processed to extract the displacement, velocity response and fluid force of the column. The energy conversion power of the column is obtained by multiplying the electromagnetic force and the vibration velocity. The energy conversion efficiency of the device is calculated by using the ratio of the time-averaged power to the total energy contained in the fluid swept by the column. The three-dimensional wake vortex structure of the column and the vortex shedding mode of each spanwise section are studied using CFD flow field visualization technology.

[0067] As a further limitation of this embodiment of the invention, in step S1, the distance between the inlet boundary of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 10 times the column diameter, the distance between the two lateral boundaries of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 10 times the column diameter, the distance between the outlet boundary of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 30 times the column diameter, and the ratio of the spanwise length to the column diameter is determined according to the column length of the vortex-induced vibration tidal power generation device to be simulated.

[0068] Preferably, in step 1, the distance from the inlet boundary of the external flow field calculation domain to the center of gravity of the column is 20 times the column diameter, the distance from the two lateral boundaries to the center of gravity of the column is 20 times the column diameter, the distance from the outlet boundary to the center of gravity of the column is 40 times the column diameter, and the ratio of the spanwise length to the column diameter is 5.

[0069] As a further limitation of this embodiment of the invention, the height of the first layer of mesh along the radial direction of the cylinder surface in step 2 satisfies y + ≤1, the mesh sizes in the flow direction and span direction respectively satisfy 50≤x + ≤150, 15≤z + ≤40. Interpolation of flow field information between grids is performed using a distance weighting function:

[0070]

[0071] Where: φ r The flow field variables at the acceptor unit are M and φ is the number of donor units. i d represents the flow field variable at donor unit i. i This represents the distance between donor unit i and recipient unit i.

[0072] As a further limitation of this embodiment of the invention, in step 3, the discretization of the fluid control equations uses the finite volume method (FVM), and the PIMPLE algorithm is used to handle pressure-velocity coupling. The transient terms are discretized using an implicit second-order backward scheme, and the convection terms are discretized using a second-order linear-upwind stabilized transport (LUST) scheme. An adaptive time step is selected to satisfy the Courant-Friedrichs-Lewy (CFL) condition, such that the maximum Courant number Co is achieved. max <1.

[0073] As a further limitation of this embodiment of the invention, the structural dynamics model of vortex-induced vibration under the action of electromagnetic force and nonlinear restoring force in step 4 is as follows:

[0074]

[0075] In the formula: m is the mass of the vibrating system, b represents the structural damping coefficient of the system, and b em F represents the electromagnetic damping coefficient of the system, k is the linear stiffness of the system, c is the nonlinear stiffness, and F is the electromagnetic damping coefficient of the system. y This refers to the transverse fluid force acting on the column. Vortex-induced tidal power generation devices often use permanent magnet linear generators for energy conversion. The electromagnetic force of a permanent magnet linear generator is essentially a damping force with a variable damping coefficient. According to Faraday's law of electromagnetic induction and the single magnetic dipole approximation, the electromagnetic damping coefficient b... em It can be represented as:

[0076]

[0077] Where a represents the coil radius, μ is the magnetic dipole moment, N represents the number of coil turns, L represents the coil length, and R is the load resistance. The following boundary and initial conditions are adopted: the inlet boundary uses velocity inlet boundary conditions, the outlet boundary uses pressure outlet boundary conditions, the transverse boundary conditions use free slip boundary conditions, the cylinder surface uses no slip boundary conditions, the spanwise boundary uses periodic boundary conditions, and the cylinder is initially in a stationary state.

[0078] As a further limitation of this embodiment of the invention, the Newmark method used in step 5 relates the displacement, velocity, and acceleration from step n to step n+1 in the following manner:

[0079]

[0080]

[0081] By selecting suitable integration parameters β = 1 / 4 and γ = 1 / 2, the numerical integration method is unconditionally stable and has second-order accuracy.

[0082] As a further limitation of this embodiment of the invention, the energy conversion efficiency of the column vortex-induced vibration in step 6 is calculated using the following formula:

[0083]

[0084] in, Here, ρ represents the time-averaged power, U represents the fluid density, and A represents the free-flow velocity. y Let D be the maximum amplitude of the column vibration, D be the column diameter, and H be the column spanwise length. The λ² criterion is used to identify the three-dimensional wake structure of the column, and the vortex shedding mode of each spanwise section is represented by the vorticity field.

[0085] This invention also provides a vortex-induced vibration tidal current power generation device, including a processor and a memory, wherein the memory stores a computer program that can be executed by the processor to implement the method described above.

[0086] This invention also provides a computer-readable medium storing a computer program that can be read to implement the method described above.

[0087] The specific implementation methods of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0088] Example 1

[0089] In this embodiment, the vibration system has a mass m = 1.2356 kg, a linear stiffness k = 7.8044 N / m, and a nonlinear stiffness c = 3024.2282 N / m. 3The system's structural damping coefficient is b = 0.04 N·m, the coil radius is a = 0.012 m, and the magnetic dipole moment is μ = 0.00014 T·m. 3 With coil turns N = 100, coil length L = 0.115m, and load resistance R = 0.15Ω, the vortex-induced vibration response and energy conversion efficiency of a column with diameter D = 0.0508m and span length H = 0.254m under the action of electromagnetic force and nonlinear restoring force at an incoming flow velocity U = 0.1016m / s were obtained.

[0090] The basic steps of this embodiment are as follows: Figure 1 As shown:

[0091] Step 1: Create a 3D geometric model of the column structure. Based on the geometric dimensions of the column structure, establish a 3D external flow field computational domain model in which it is located, such as... Figure 2 As shown, the three-dimensional external flow field computational domain is a cuboid region enclosing the cylindrical structure. The upstream region of the cylindrical structure is a free flow region, and the downstream region is a wake region where vortices detach. The inlet boundary of the external flow field computational domain is 20 times the diameter of the cylindrical structure, the two lateral boundaries are 20 times the diameter of the cylindrical structure, and the outlet boundary is 40 times the diameter of the cylindrical structure. The spanwise length to the cylindrical diameter ratio is 5.

[0092] Step 2: Divide the column component mesh and the computational domain background mesh, such as... Figure 3a and Figure 3b As shown, the column component mesh adopts an O-type body-fit meshing strategy, and the component mesh region is a cylinder concentric with the column structure. The height of the first layer of mesh along the radial direction of the column surface satisfies y + ≤1, the mesh sizes in the flow direction and span direction respectively satisfy 50≤x + ≤150, 15≤z + ≤40. Then, the background mesh of the external flow field is divided, and the mesh near the cylinder and in the wake region is refined. Both the component mesh and the background mesh use structured meshes. The overlapping mesh technique from the open-source computational fluid dynamics toolbox OpenFOAM is used to "dig holes" in the mesh located inside the cylinder, identifying overlapping meshes that are not included in the calculation and ignoring them during the calculation. Interpolation is performed using the edge meshes, and the interpolation of flow field information between meshes is completed using a distance weighting function to obtain the flow field variables at the receiver element:

[0093]

[0094] Where: φ r The flow field variables at the acceptor unit are M and φ is the number of donor units. i d represents the flow field variable at donor unit i. iThis represents the distance between donor unit i and recipient unit i. This enables the transfer of flow field information between the two mesh sets.

[0095] Step 3: Solve the flow field governing equations using the open-source computational fluid dynamics toolbox OpenFOAM. The flow field around the cylinder is solved using the unsteady incompressible Navier-Stokes equations. Turbulence is solved using a large eddy simulation local eddy viscosity wall adaptive model. The fluid governing equations are discretized using the finite volume method, and the PIMPLE algorithm is used to handle pressure-velocity coupling. The transient terms are discretized using an implicit second-order backward scheme, and the convection terms are discretized using a second-order linear-upwind stabilized transport (LUST) scheme. An adaptive time step is selected to satisfy the Courant-Friedrichs-Lewy (CFL) condition, maximizing the Courant number Co. max <1.

[0096] Step 4: Establish a structural dynamics model of vortex-induced vibration under the action of electromagnetic force and nonlinear restoring force:

[0097]

[0098] In the formula: m is the mass of the vibrating system, b represents the structural damping coefficient of the system, and b em F represents the electromagnetic damping coefficient of the system, k is the linear stiffness of the system, c is the nonlinear stiffness, and F is the electromagnetic damping coefficient of the system. y This refers to the transverse fluid force acting on the column. Vortex-induced tidal power generation devices often use permanent magnet linear generators for energy conversion. The electromagnetic force of a permanent magnet linear generator is essentially a damping force with a variable damping coefficient. According to Faraday's law of electromagnetic induction and the single magnetic dipole approximation, the electromagnetic damping coefficient b... em It can be represented as:

[0099]

[0100] Where a represents the coil radius, μ is the magnetic dipole moment, N represents the number of coil turns, L represents the coil length, and R is the load resistance. Initial and boundary conditions are determined, and calculation parameters are initialized: the inlet boundary uses velocity inlet boundary conditions, the outlet boundary uses pressure outlet boundary conditions, the lateral boundary conditions use free-slip boundary conditions, the cylinder surface uses no-slip boundary conditions, and the spanwise boundary uses periodic boundary conditions. The cylinder is initially in a static state, and numerical simulation is conducted.

[0101] Step 5: Using the Newmark method, relate the displacement, velocity, and acceleration from step n to step n+1 in the following way:

[0102]

[0103]

[0104] Choose suitable integration parameters β = 1 / 4 and γ = 1 / 2 to make the numerical integration method unconditionally stable and have second-order accuracy. Determine whether the termination time has been reached. If the termination time has not been reached, update the flow field mesh and return to step 3. Repeat steps 3–5 on the updated mesh to solve for the flow field at the next time step.

[0105] Step 6: After the simulation reaches its termination time, post-process the calculated data to extract the displacement, velocity response, and fluid forces acting on the column. The energy conversion power of the column is obtained by multiplying the electromagnetic force by the vibration velocity. The energy conversion efficiency of the device is calculated using the ratio of the time-averaged power to the total energy contained in the fluid swept by the column.

[0106]

[0107] in, Here, ρ represents the time-averaged power, U represents the fluid density, and A represents the free-flow velocity. y Let D be the cylinder diameter and H be the cylinder spanwise length, where D represents the maximum amplitude of the cylinder vibration. In this example, the time-history curves of the vibration displacement of the elastically supported rigid cylinder under the action of electromagnetic force and nonlinear restoring force are as follows: Figure 4a As shown, the horizontal axis represents time (seconds), and the vertical axis represents vibration displacement. The time-history curve of the energy conversion power of the column's vortex-induced vibration is shown in the figure. Figure 4b As shown, the horizontal axis represents time (seconds), and the vertical axis represents energy conversion power. The λ² criterion is used to identify the three-dimensional wake structure of the column, and the vortex shedding modes of each spanwise section are represented by vorticity fields. In this example, the three-dimensional wake structure of an elastically supported rigid column undergoing vortex-induced vibration under the action of electromagnetic force and nonlinear restoring force is shown below. Figure 5a As shown, Figure 5b A vortex shedding pattern diagram of a section at spanwise position 0m. Figure 5c A vortex pattern diagram for a cross-section of 0.0508m. Figure 5d A vortex pattern diagram with a cross-section of 0.1016m. Figure 5e A vortex pattern diagram with a cross-section of 0.1524m. Figure 5f Vortex pattern diagram with a cross-section of 0.2032m and Figure 5gThe vortex shedding mode is represented by a cross-section of 0.254m. Existing technologies typically simplify the electromagnetic force of a generator as a damping force with a constant damping coefficient, while in actual engineering, the electromagnetic force of a generator is essentially a damping force with a variable damping coefficient. Furthermore, simulation techniques for vortex-induced vibration that consider nonlinear restoring forces are still quite limited. This embodiment fully considers the roles of electromagnetic force and nonlinear restoring force in vortex-induced vibration tidal power generation devices, enabling a more realistic reflection of the response and energy conversion characteristics of these devices. Simulation of the nonlinear restoring force in the vortex-induced vibration system can be used to optimize and improve the performance of vortex-induced vibration tidal power generation devices.

[0108] The application scenarios targeted by the embodiments of the present invention differ significantly from those of existing technologies. The embodiments of the present invention can be used for predicting the response and energy conversion characteristics of vortex-induced vibration tidal current power generation devices and optimizing the performance of such devices. Existing technologies, on the other hand, primarily aim to suppress vortex-induced vibration of structures and reduce its impact on the fatigue life of tall column structures. The beneficial technical effects of the present invention compared to existing technologies are as follows:

[0109] 1. In engineering, the flow field of vortex-induced vibration of a real column exhibits strong three-dimensional characteristics. This invention employs a three-dimensional numerical simulation method, which can capture the three-dimensional effects of the flow field, while existing two-dimensional methods have significant shortcomings.

[0110] 2. In solving complex high Reynolds number turbulent flows, the large eddy simulation method used in the embodiments of the present invention is more accurate than the RANS method used in the prior art.

[0111] In the simulation of vortex-induced vibration tidal current power generation devices, existing technologies typically simplify the electromagnetic force of the generator to a damping force with a constant damping coefficient. However, in actual engineering, the electromagnetic force of the generator is essentially a damping force with a variable damping coefficient. Furthermore, simulation techniques for vortex-induced vibration that consider nonlinear restoring forces are still quite limited. The embodiments of this invention fully consider the effects of electromagnetic force and nonlinear restoring force in an elastically supported rigid column vortex-induced vibration system, enabling a more realistic reflection of the response and energy conversion characteristics of the vortex-induced vibration tidal current power generation device. The simulation of the nonlinear restoring force in the vortex-induced vibration system can be used to optimize and improve the performance of the vortex-induced vibration tidal current power generation device.

[0112] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several equivalent substitutions or obvious modifications can be made without departing from the concept of the present invention, and all such modifications, achieving the same performance or purpose, should be considered within the scope of protection of the present invention.

Claims

1. A numerical simulation method for a vortex-induced vibration tidal current power generation device, characterized in that, Includes the following steps: S1: Create the geometric model of the column structure and the geometric model of the external flow field calculation domain in which the column structure is located; S2: Mesh the computational domain of the flow field near the column structure and the computational domain of the external flow field to obtain the column component mesh and the background mesh of the external flow field computational domain. The flow field information between the column component mesh and the background mesh of the external flow field computational domain is transferred through the overlapping mesh technique. S3: Establish a structural dynamics model for the vortex-induced vibration of a column under the action of electromagnetic force and nonlinear restoring force; the structural dynamics model is as follows: In the formula: m For the mass of the vibration system, b This represents the structural damping coefficient of the system. b em Represents the electromagnetic damping coefficient of the system. k For the linear stiffness of the system, c It is nonlinear stiffness. F y The transverse fluid force acting on the column; According to Faraday's law of electromagnetic induction and the single magnetic dipole approximation, the electromagnetic damping coefficient... b em It can be represented as: in, a Indicates the coil radius. μ It is the magnetic dipole moment. N Represents the number of coil turns. L Indicates the coil length. R It is the load resistor; S4: Combine the computational fluid dynamics model with the structural dynamics model to perform fluid-structure interaction numerical calculations; solve the structural dynamics model of vortex-induced vibration under the action of electromagnetic force and nonlinear restoring force by Newmark numerical integration method, and obtain the displacement, velocity and acceleration of the column vibration; Determine if the termination time has been reached. If not, update the flow field mesh and repeat steps S3–S4 on the updated mesh to solve for the next time step. S5: After the simulation reaches its termination time, the calculated data is post-processed to obtain the response and energy conversion characteristics of the column's vortex-induced vibration.

2. The numerical simulation method according to claim 1, characterized in that: In step S1, the geometric model of the external flow field calculation domain is established based on the geometric dimensions of the cylindrical structure. The external flow field calculation domain is a cuboid region that surrounds the cylindrical structure. The upstream of the cylindrical structure is a free flow region, and the downstream is a wake region where vortices fall off.

3. The numerical simulation method according to claim 2, characterized in that: In step S2, the column component mesh adopts an O-type body-fitting mesh division strategy, and the component mesh area is a cylinder concentric with the column structure; When dividing the background grid of the external flow field computational domain, the grid near the cylinder and the wake region is refined; Both the column component mesh and the background mesh of the external flow field computational domain use structured meshes. Overlapping mesh technology is used to punch holes in the mesh inside the column, and the overlapping meshes that do not participate in the calculation are identified and not considered during the calculation. By interpolating through the edge mesh, flow field information can be transferred between the column component mesh and the background mesh of the external flow field computation domain.

4. The numerical simulation method according to claim 3, characterized in that: The height of the first layer of mesh along the radial direction on the surface of the cylinder described in step S2 satisfies y + ≤ 1, the grid size in the flow direction and span direction respectively satisfy 50 ≤ x + ≤ 150, 15≤ z + For values ​​≤ 40, interpolation of flow field information between grids is performed using a distance weighting function: In the formula: r It is the flow field variable at the receptor unit. M The number of donor units, i Represents donor unit i Flow field variables at that location, d i Representative donor unit i The distance between the receptor unit and the receptor unit.

5. The numerical simulation method according to claim 4, characterized in that: Step S3 also includes: Using computational fluid dynamics, the flow field around the cylinder was solved using the unsteady incompressible Navier-Stokes equations, and the turbulence was solved using a large eddy simulation local eddy viscosity wall adaptive model.

6. The numerical simulation method according to claim 5, characterized in that: In step S3, The fluid control equations are discretized using the finite volume method, with the PIMPLE algorithm used to handle pressure-velocity coupling. The transient terms are discretized using an implicit second-order backward scheme, while the convection terms are discretized using a second-order linear upwind steady-state transport scheme. An adaptive time step is selected to satisfy the Courant-Friedrichs-Lewy condition, maximizing the Courant number. Co max < 1.

7. The numerical simulation method according to claim 6, characterized in that: Step S3 also includes determining the initial and boundary conditions, initializing the calculation parameters, and conducting numerical simulation; The fluid forces acting on the column are calculated by integrating the pressure and viscous forces acting on the column surface, and these fluid forces are then incorporated into the structural dynamics model.

8. The numerical simulation method according to claim 7, characterized in that: The eddy-induced vibration tidal current power generation device uses a permanent magnet linear generator for energy conversion. The electromagnetic force of the permanent magnet linear generator is essentially a damping force with a variable damping coefficient. The boundary conditions are determined as follows: the inlet boundary uses a velocity inlet boundary condition, the outlet boundary uses a pressure outlet boundary condition, the lateral boundary condition uses a free slip boundary condition, the column surface uses a no slip boundary condition, and the spanwise boundary uses a periodic boundary condition. The column was initially in a static state.

9. The numerical simulation method according to claim 1, characterized in that: In step S4, the Newmark method used will... n Step to the first n The displacement, velocity, and deceleration of step +1 are related as follows: Select appropriate integration parameters β = 1 / 4, γ = 1 / 2, which makes the numerical integration method unconditionally stable and has second-order accuracy.

10. The numerical simulation method according to claim 9, characterized in that: The post-processing in step S5 includes: extracting the displacement, velocity response and fluid force of the column; obtaining the energy conversion power of the column by multiplying the electromagnetic force and the vibration velocity; calculating the energy conversion efficiency of the device by using the ratio of the time-averaged power to the total energy contained in the fluid swept by the column; and using CFD flow field visualization technology to study the three-dimensional wake vortex structure of the column and the vortex shedding modes of each spanwise section.

11. The numerical simulation method according to claim 10, characterized in that: The energy conversion efficiency of the column vortex-induced vibration described in step S5 is calculated using the following formula: in, The power is the time-averaged power. ρ Indicates fluid density, U Represents the free flow velocity. A y This represents the maximum amplitude of the column's vibration. D It is the diameter of the cylinder. H To represent the span of a cylinder, use λ The two criteria are used to identify the three-dimensional wake structure of the column, and the vortex discharge mode of each spanwise section is represented by the vorticity field.

12. The numerical simulation method according to claim 11, characterized in that: In step S1, the distance between the inlet boundary of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 10 times the column diameter; the distance between the two lateral boundaries of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 10 times the column diameter; the distance between the outlet boundary of the external flow field calculation domain and the center of gravity of the column is greater than or equal to 30 times the column diameter; and the ratio of the spanwise length to the column diameter is determined according to the column length of the vortex-induced vibration tidal power generation device to be simulated.

13. A vortex-induced tidal current power generation device, comprising a processor and a memory, wherein the memory stores a computer program, characterized in that, The computer program may be executed by a processor to implement the method as described in any one of claims 1-12.

14. A computer-readable medium storing a computer program, characterized in that, The computer program can be read to implement the method as described in any one of claims 1-12.

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