Characteristic analysis method based on vortex-induced vibration of deep-sea mining pipe

Abstract

The invention provides a characteristic analysis method based on vortex-induced vibration of a deep-sea mining pipe. The method comprises the following steps: S1, establishing a structural model of the deep-sea mining pipe; s2, a flow field model is established through a slicing method, and the flow field acting force of a flow field acting on the deep-sea mining pipe is obtained; s3, establishing a kinematic model of the deep-sea mining pipe, and solving motion data; and S4, coupling the flow field model and the kinematic model to obtain vortex-induced vibration characteristic parameters of the deep-sea mining pipe. According to the method, a novel deep-sea mining pipe vortex-induced vibration analysis model is constructed by dividing a fluid domain through a slicing method and combining a pipe body numerical simulation method; according to the method, it is guaranteed that the mining pipe model has high accuracy and calculation precision, meanwhile, the whole flow field domain does not need to be subjected to all grid division, and needed calculation resources are greatly reduced; the pipe body establishes corresponding model calculation based on a finite element method, and after model coupling, the characteristics of the three-dimensional vertical pipe can be fitted to the maximum extent.

Description

Technical Field

[0001] The invention belongs to the technical field of marine equipment vibration analysis, and in particular relates to a characteristic analysis method based on vortex-induced vibration of a deep-sea mining pipe. Background Art

[0002] The deep seabed contains high-quality and abundant mineral resources. Therefore, major maritime countries are vigorously developing the deep-sea mining industry. The development of deep-sea mineral resources requires a complex mining system, namely the deep-sea mining system.

[0003] The deep-sea mining system is a comprehensive system for mining mineral resources on the deep seabed. The existing common deep-sea mining systems usually include mining ships, deep-sea mining pipes, lifting equipment, intermediate warehouses and other parts. Among them, the mining ship is used to control and support operations on the sea surface; the deep-sea mining pipe connects the mining ship and the seabed ore deposit to transport the mined ore or minerals to the sea surface; the lifting equipment is used to lift the minerals on the seabed onto the mining ship; the intermediate warehouse plays a role in storage or buffering during the mining process. Since the deep-sea mining system will face complex ocean current conditions during operation, it will have a great impact on the deep-sea mining pipe. Among them, vortex-induced vibration (VIV) is the main source of fatigue damage to deep-sea mining pipes. Deep-sea mining pipes play a vital role in deep-sea mining systems and bear important responsibilities for mineral transportation. Therefore, it is important to analyze the characteristics of vortex-induced vibration of the pipeline.

[0004] During operation, the upper end of the deep-sea mining pipe is connected to the surface hull structure, and the lower end is connected to the underwater mining vehicle through a hose. Therefore, it has the characteristics of free suspension, large aspect ratio, and weak bottom constraint. Compared with the traditional riser with hinged ends, the vortex-induced vibration response of the deep-sea mining pipe is more complex. Many previous studies have focused on the traditional riser with hinged ends, so the numerical model of the traditional riser is relatively mature; while the numerical model analysis of this free-end constrained deep-sea mining pipe is relatively rare.

[0005] At present, in the study of vortex-induced vibration of deep-sea mining pipes, there are cases where the discrete vortex method (DVM) is used to analyze the vortex-induced vibration of mining pipes. Among them, a key feature of DVM is that it does not require a gridded computational domain, which makes it advantageous when simulating complex geometries. However, DVM also has its limitations, because there are defects in boundary processing, which will lead to instability of numerical results and a significant decrease in calculation accuracy; and it cannot meet the conditions of instantaneous circulation conservation, that is, the change of circulation cannot be accurately maintained during the simulation process, which further affects the accuracy and stability of the calculation.

[0006] In summary, in order to make the characteristic analysis of vortex-induced vibration of deep-sea mining pipes occupy less resources and provide better calculation accuracy and stability, it is also necessary to improve the vortex-induced vibration analysis method of deep-sea mining pipes. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a characteristic analysis method based on vortex-induced vibration of deep-sea mining pipe to solve the above problems.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a method for analyzing the characteristics of vortex-induced vibration of a deep-sea mining pipe, the steps comprising:

[0010] S1. Based on the geometric structure of the deep-sea mining pipe, a structural model of the deep-sea mining pipe is established by the finite element method;

[0011] S2. Establish the flow field model of the deep-sea mining pipe fluid domain by slicing method;

[0012] Calculating a fluid control equation based on the flow field model, and solving the fluid control equation to obtain a flow field force acting on the deep-sea mining pipe;

[0013] S3, establishing a kinematic model of the deep-sea mining pipe based on the structural model and the flow field force, and solving the kinematic model by a numerical solution method to obtain motion data of the deep-sea mining pipe;

[0014] S4. Based on the flow field force and the motion data, the flow field model and the kinematic model are coupled by a dynamic mesh technology to obtain a vortex-induced vibration model of a deep-sea mining pipe;

[0015] The vortex-induced vibration model of the deep-sea mining pipe is solved to obtain the vortex-induced vibration characteristic parameters of the deep-sea mining pipe.

[0016] Furthermore, the pipe body of the deep-sea mining pipe is divided into a plurality of finite element nodes;

[0017] The number of the finite element nodes is 4-6 times the number of slices divided by the slicing method.

[0018] Furthermore, in S2, the flow field model establishment process includes:

[0019] Divide the fluid domain into multiple flow field slices;

[0020] The grid is divided on each flow field slice by using overlapping grid technology and moving grid technology.

[0021] Furthermore, in the grid division of the flow field slice, the foreground grid is an O-type grid.

[0022] Furthermore, in S2, the fluid control equation is solved by the continuity equation and the NS equation.

[0023] Further, in said S3, the structural basis in said kinematic model is a beam model;

[0024] In the beam model, the tube body between two nodes is equivalent to a beam unit, and the upper end is hinged and the lower end is freely set.

[0025] Furthermore, in S3, the motion data solving step includes:

[0026] S31, discretely calculate the stiffness matrix, mass matrix, damping matrix and load column vector of each unit;

[0027] S32, based on the calculation results of S31, combining and calculating the overall stiffness matrix, mass matrix, damping matrix and load column vector of the pipe body;

[0028] S33, substituting the calculation result of S32 into the kinematic model, and obtaining the motion data by iterative solution through the Newmark-beta method.

[0029] Further, in S4, the coupling process includes:

[0030] Synchronously substituting the motion data into the fluid control equation and updating the flow field force;

[0031] The updated flow field force is substituted into the kinematic model, and the motion data is updated.

[0032] Furthermore, it also includes:

[0033] The vortex-induced vibration characteristic parameters are verified based on experimental or simulation data, and the vortex-induced vibration model of the deep-sea mining pipe is corrected by a parameter calibration method.

[0034] Furthermore, it also includes:

[0035] The vortex-induced vibration characteristic parameters are extracted, and the transverse-flow instantaneous dimensionless displacement envelope, the downstream instantaneous dimensionless displacement envelope, the displacement response duration curve, the center of mass motion trajectory and the frequency amplitude schematic diagram of the deep-sea mining pipe are drawn through the data visualization method.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention constructs a new model for vortex-induced vibration analysis of deep-sea mining pipes by dividing the fluid domain through the slicing method and combining it with the pipe body numerical simulation method; while ensuring that the mining pipe model has high accuracy and calculation precision, it is not necessary to perform full grid division on the entire flow field domain, which greatly reduces the required computing resources; the pipe body establishes the corresponding model calculation based on the finite element method, and after model coupling, it can fit the characteristics of the three-dimensional riser to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0039] Figure 1 is a flow chart of the method of the present invention;

[0040] Figure 2 Modeling flow chart for the present invention;

[0041] Figure 3 A schematic diagram of deep-sea mining pipe slice numbers and corresponding finite element nodes in a specific embodiment of the present invention;

[0042] Figure 4 The grid division of the fluid domain of the deep-sea mining pipe in the specific embodiment of the present invention;

[0043] Figure 5 A schematic diagram of setting boundary conditions for each slice in a specific embodiment of the present invention;

[0044] Figure 6 It is a schematic diagram of setting boundary conditions of the deep-sea mining pipe fluid domain in a specific embodiment of the present invention;

[0045] Figure 7 It is a schematic diagram of a deep-sea mining pipe structure model in a specific embodiment of the present invention;

[0046] Figure 8 It is a simplified schematic diagram of uniformly distributed load in a specific embodiment of the present invention;

[0047] Fig. 9 It is a schematic diagram of converting a uniform load in a unit into an equivalent load of a node using an equivalent load method in a specific embodiment of the present invention;

[0048] Fig.10 This is a numerical simulation flow chart based on the Newmark-beta method combined with self-compiled UDF in a specific embodiment of the present invention;

[0049] Fig.11This is a numerical verification of a specific embodiment of the present invention: u = 0.2m / s, a comparison diagram of the downstream displacement envelope of a hinged riser at both ends;

[0050] Fig.12 This is a numerical verification in a specific embodiment of the present invention: u=0.2m / s, a comparison diagram of the transverse flow displacement envelope of the hinged riser at both ends;

[0051] Fig.13 : is a motion characteristic diagram at slice 6 in a specific embodiment of the present invention, FIG (j) is a time curve of displacement response in the downstream direction, FIG (i) is a time curve of displacement response in the cross-stream direction, and FIG (k) is a trajectory of centroid motion;

[0052] Fig.14 It is the instantaneous dimensionless displacement envelope diagram of the riser in the transverse flow direction in a specific embodiment of the present invention (left figure: ur=18; right figure: ur=38);

[0053] Fig.15 It is a schematic diagram of the change of the maximum value of the mean value of the dimensionless displacement in the transverse direction of the bottom end of the mining pipe with ur in a specific embodiment of the present invention;

[0054] Fig.16 Schematic diagram of the frequency amplitude in the transverse direction of the mining pipe at different reduced velocities in a specific embodiment of the present invention (left figure: ur=18; right figure: ur=38). DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0057] It should also be noted that the methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products unless otherwise specified.

[0058] This embodiment proposes a characteristic analysis method based on vortex-induced vibration of deep-sea mining pipes, such as Figure 1 and Figure 2 As shown, the specific steps include:

[0059] S1. Based on the geometric structure of the deep-sea mining pipe, a structural model of the deep-sea mining pipe is established by the finite element method;

[0060] Optionally, the pipe body of the deep-sea mining pipe is divided into a plurality of finite element nodes. In this embodiment, 50 evenly distributed nodes are set for the deep-sea mining pipe (one node is set at the beginning and the end respectively), so that the pipe body is divided into 49 evenly distributed units.

[0061] S2. The flow field model of the deep-sea mining pipe fluid domain is established by the slicing method. Among them, the numerical simulation of vortex-induced vibration analysis is greatly limited by the computing performance of the computer. Therefore, the use of the quasi-three-dimensional numerical simulation method such as the slicing method can greatly reduce the amount of calculation and shorten the calculation time.

[0062] First, if Figure 3 As shown, the deep-sea mining pipe fluid domain is divided into multiple flow field slices according to the existing computing resources. Optionally, the corresponding design is combined with the aforementioned pipe body segmentation unit, and the number of finite element nodes is selected to be 4-6 times the number of slices divided by the slice method; Among them, it is also necessary to consider that it corresponds to the mode of the deep-sea mining pipe. A mode of the mining pipe requires at least three points to be used for description. Although the more nodes the better in order to improve the accuracy, too many nodes will lead to a significant increase in the amount of calculation. Therefore, it is determined to be divided into 12 slices in this implementation for balanced consideration. Among them, finite element node 3 corresponds to slice No. 1, finite element node 7 corresponds to slice No. 2, finite element node 11 corresponds to slice No. 3, finite element node 15 corresponds to slice No. 4, finite element node 19 corresponds to slice No. 5, finite element node 23 corresponds to slice No. 6, finite element node 27 corresponds to slice No. 7, finite element node 31 corresponds to slice No. 8, finite element node 35 corresponds to slice No. 9, finite element node 39 corresponds to slice No. 10, finite element node 43 corresponds to slice No. 11, and finite element node 47 corresponds to slice No. 12.

[0063] Secondly, establish the flow field model, establish the viscous flow field calculation model through the application of mining pipes in actual marine engineering, and select the appropriate flow field size and grid division method, such as Figure 4 As shown, this embodiment uses overlapping grids and combined dynamic grid technology to perform grid division, and uses O-type segmentation to encrypt the foreground grid to better capture the boundary layer effect.

[0064] Finally, if Figure 5 and Figure 6 As shown, the 12 flow field slices actually divided by the mining pipe are determined, and the boundary conditions of the area of ​​each flow field slice are defined, including the inlet, outlet, wall, etc., and the fluid control equations are discretely solved.

[0065] Solution of fluid control equations: Select a suitable physical model according to the specific flow problem, such as the continuity equation, NS equation, energy equation, etc.; in this embodiment, flow-induced vortex-induced vibration is mainly considered, incompressible viscous fluid is considered, and the conversion between energies is not considered. Therefore, the continuity equation and NS equation are selected to solve the fluid control equations.

[0066] Among them, Reynolds-averaged Navier-Stokes (RANS) is an important method in computational fluid dynamics, which is used to simulate turbulent flow. Through Reynolds decomposition and time averaging, the NS equations are converted into Reynolds-averaged Navier-Stokes equations, which describe the dynamic behavior of the average velocity field. Therefore, the equation formula in Cartesian coordinates is:

[0067] Continuity equation:

[0068]

[0069] Momentum equation:

[0070]

[0071] In the formula, i and j are 1, 2 or 3, representing the components of the variables in the x, y and z directions respectively; P is the pressure in Pa; is the Hamiltonian operator; is the time-averaged velocity in m / s; is the time-averaged value of the pulsating flow velocity, in m / s; ρ is the fluid density.

[0072] The Reynolds stress in the RANS equation needs to be modeled through additional transport equations to achieve the closure of the equation. Therefore, according to the characteristics of the flow and the computing resources, a suitable turbulence model is selected, namely the SSTk-ω turbulence model: a widely used two-equation eddy viscosity model, which combines the advantages of the k-ε model and the k-ω model, and is particularly suitable for simulating adverse pressure gradients and separated flows. The transport equation of the model includes turbulent kinetic energy k and specific dissipation rate ω, and the equation formula is:

[0073]

[0074]

[0075] In the formula, is the generation term of turbulent kinetic energy k caused by the average velocity; G ω is the turbulent kinetic energy generated by the ω equation, Γ k and Γ ω represents the effective diffusion rate of k and ω, Y k and Y ωis the turbulent dissipation term due to diffusion, D ω is the orthogonal divergence term, S k and S ω is the source phase of the equation.

[0076] Therefore, the fluid control equations of the flow field are solved by Fluent software: define the fluid material properties before software calculation, select the boundary of the calculation domain, and specify appropriate boundary conditions, such as velocity inlet, pressure outlet, symmetry conditions, etc.; set the initial conditions, select the appropriate numerical solver and solution parameters in Fluent, such as time step, relaxation factor, etc., set the dynamic grid to control grid deformation, initialize the solution process, monitor indicators such as residuals to ensure the convergence and accuracy of the solution.

[0077] By using the UDF program compiled in the C language environment in Fluent, it is possible to solve the force of the viscous flow field on the fluid in the pipe structure, that is, the flow field force acting on the deep-sea mining pipe.

[0078] S3. Establish the kinematic model of the deep-sea mining pipe based on the structural model and flow field forces;

[0079] First, the structural model is further improved. Figure 7 On the basis of the double-freedom cylinder model and the riser model with hinged ends, the structural model is improved. Among them, for the riser model of this embodiment, the material and cross-sectional shape are the same along the length of the pipe, and the deep-sea mining pipe model is simplified into an Euler-Bernoulli beam model with one end hinged and the other end free (Z direction constraint) and the top end subjected to preload. The x-axis represents the downstream direction, the y-axis represents the cross-flow direction, and the z-axis represents the axial direction of the riser. Thus, a simplified diagram of the force model of the mining pipe is obtained, as shown in FIG. Figure 8 and Fig. 9 The upper end shown is fixed and the lower end is free.

[0080] Establish kinematic model; refer to Fig. 9 Coordinate system, ignoring the wave effect, the differential control equations of the motion of the tube unit length in the x and y directions are obtained, and the equation formula is:

[0081]

[0082]

[0083] Where EI is the bending stiffness, in Nm 2 ; T(z) is the axial force at different positions of the tube; c is the structural damping coefficient; m r and m f Respectively represent the mass of the standpipe per unit length and the mass of the internal flow, in kg / m; F x (z,t) and Fy (z, t) represent the fluid forces acting on the riser in the downstream and cross-flow directions respectively, and the unit is N.

[0084] Furthermore, in order to solve the motion differential control equation of the above kinematic model, it is also necessary to solve the parameters therein.

[0085] Therefore, the motion data solving steps include:

[0086] S31, discretely calculate the stiffness matrix, mass matrix, damping matrix and load column vector of each unit;

[0087] The analysis divides 49 three-dimensional space beam units along the axial direction of the deep-sea mining pipe. Each unit contains two nodes, and each node contains six degrees of freedom, that is, one unit corresponds to 12 degrees of freedom. In previous studies, the unit axis direction is selected in the x direction. In order to obtain the unit geometric stiffness matrix required in this embodiment Element elastic stiffness matrix And the unit mass matrix M e , coordinate transformation is required. In structural dynamics, the stiffness increment caused by the axial force is defined as the geometric stiffness, and the unit stiffness matrix K in the tube is e It is composed of the unit geometric stiffness matrix and the unit elastic stiffness matrix. The unit stiffness matrix calculation formula of the deep-sea mining pipe is:

[0088]

[0089] The nodal load vector matrix F of the mining pipe finite element e The formula is:

[0090]

[0091] In the formula, F x 、F y 、F z are the load vector components of the unit on the x-axis, y-axis, and z-axis respectively; M θx 、M θy 、M θz are the torque components about the x-axis, y-axis, and z-axis respectively.

[0092] When the fluid force acts on the mining pipe, the node load component of the mining pipe can be calculated from the fluid domain. Assume that the axial force on the pipe body is always zero along the axis of the pipe body without deviation. The axial force on the pipe body is related to the top tension, and the assumed magnitude gradually decreases from the top to the bottom along the axial direction of the riser. The calculation formula is:

[0093] F z =T(z)=Tw b (Lz) (9)

[0094] Where, W b It is the downward pulling force borne by the bottom of the pipe body, that is, the weight of the middle compartment in the deep-sea mining system.

[0095] S32, based on the calculation results of S31, the overall stiffness matrix, mass matrix, damping matrix and load column vector of the pipe body are calculated in combination;

[0096] By discretizing the deep-sea mining pipe into a finite number of three-dimensional elements, the governing equations of structural motion can be discretized as:

[0097]

[0098] Where, [M] is the overall mass matrix, which is assembled from the unit mass matrix; [C] is the overall damping matrix, and Rayleigh damping is used in this paper; [K] is the overall stiffness matrix, which is assembled from the unit stiffness matrix; F(t) is the overall load column vector, which is assembled from the unit load column vector; x(t) is the displacement column vector of all finite element nodes of the pipe body; is the velocity column vector of all finite element nodes of the tube body; is the acceleration column vector of all finite element nodes of the tube.

[0099] The natural frequency usually affects the structural damping, and the Rayleigh damping matrix is ​​used to calculate the structural damping.

[0100] S33, substituting the calculation result of S32 into the kinematic model, and iteratively solving the kinematic data by the numerical solution method in structural dynamics;

[0101] The numerical solution method of this embodiment adopts the Newmark-beta method to solve the motion control equation of the deep-sea mining pipe structure. By establishing the displacement {x i},speed Acceleration and the displacement {x i (t+Δt)}, speed Acceleration The recursive relationship between them is used to gradually solve the state variables of each finite element node of the pipe body at different times starting from the moment t=0.

[0102] Furthermore, under the control parameters δ≥0.50 and β≥0.25(0.50+δ) 2 When , the Newmark-beta method is unconditionally stable; if δ and β do not satisfy the above range, the stability of the Newmark-beta method requires the time step to satisfy the following formula:

[0103]

[0104] The vibration control equation of the flexible riser (Formula 6) is a dynamic response problem of a multi-degree-of-freedom system. The vibration control equation in the form of Formula (6) is a second-order ordinary differential equation system. This embodiment uses the Newmark-β method in the step-by-step integration method to solve the structural dynamic equation. The process is as follows:

[0105] The local stiffness matrix of each unit is obtained by integration, and mapped to the global stiffness matrix according to the node number using Matlab programming, and the overall mass matrix [M], overall stiffness matrix [K], and overall damping matrix [C] of the mining pipe are obtained;

[0106] Given the acceleration at t = 0 speed Displacement {x i} and the load vector F at the initial moment i (t);

[0107] Select the time step Δt, control parameters δ=0.5 and β=0.25, and calculate a0~a7;

[0108]

[0109]

[0110] Calculate the equivalent stiffness matrix [K′]:

[0111] [K′]=[K]+a0[M]+a1[C] (12) Calculate the equivalent load vector F at time t+Δt i ′(t+Δt):

[0112]

[0113] Solve the equivalent static equilibrium equation and find the displacement {x i (t+Δt)}:

[0114] [K′]{x i (t+Δt)}={F i ′(t+Δt)} (14) Find the velocity at time t+Δt Acceleration

[0115]

[0116]

[0117] The acceleration, velocity and displacement values ​​at time t+Δt are used as the initial quantities of the next time step, and the above process is iterated and cycled. When the number of iterations or the iteration time is met, the corresponding motion data of the deep-sea mining pipe can be obtained.

[0118] S4. Based on the flow field force and motion data, the flow field model and the kinematic model are coupled through the dynamic mesh technology to obtain the vortex-induced vibration model of the deep-sea mining pipe. The coupling process includes:

[0119] Synchronously substitute the motion data into the fluid control equations and update the flow field forces;

[0120] Substitute the updated flow field force into the kinematic model and update the motion data.

[0121] Specifically, in the Fluent field of this embodiment, the dynamic mesh technology used in the aforementioned meshing application provides a stable solution to the above problem. By calling the dynamic mesh "macro" through the UDF program, the boundary motion information of the mining pipe can be obtained, so it is only necessary to write the corresponding UDF to execute the dynamic mesh macro, and then select the best dynamic mesh modification strategy to achieve instant modification of the fluid field mesh.

[0122] Among them, the self-compiled UDF is used to extract all fluid forces and moments of the centroid of the opposite pipe section in the two-dimensional flow field. Then, through the UDF program compiled based on C language, the fluid forces extracted in the above process are regarded as uniform loads, and the forces and moments borne by the finite element nodes involving the pipe body are calculated by the equivalent load method, and finally all load column vectors are combined. Figure 8 As shown in the figure: When calculating the equivalent load of each unit of the marine mining pipe, the sum at a specific time point will be extracted according to the calculation results of the fluid domain, simplified into a uniformly distributed load, and added to the finite unit of the pipe body. The uniform load in the unit is converted into an equivalent load of the node using the equivalent load method, such as Fig. 9 As shown. Combined with the Newmark-β method to solve the calculation. The solution process is as follows Fig.10 shown.

[0123] Based on the above steps, preferably, this embodiment further includes the following steps:

[0124] S5. Verify the vortex-induced vibration characteristic parameters based on experimental or simulation data, and correct the vortex-induced vibration model of the deep-sea mining pipe through parameter calibration method.

[0125] Specifically, due to the lack of experiments on deep-sea mining pipes, in order to verify the accuracy of the numerical model, Fig.11 and Fig.12 The main control mode diagrams (d) in the downstream direction and (h) in the cross-flow direction of the numerical simulation of the vortex-induced vibration of the traditional riser using the numerical simulation method of this embodiment are respectively given, and compared with the experimental results of the vortex-induced vibration response of a certain ocean center, the numerical simulation results using the CFD method, and the research results of the coupled displacement response of the nonlinear vortex-induced vibration of the two-dimensional nonlinear dynamic model of the top tension riser; wherein, Fig.11 The middle figure (a) is the main control mode diagram in the downstream direction of the vortex-induced vibration response experiment results in the center of the ocean; Fig.11 The middle figure (b) is the main control mode diagram in the downstream direction of the numerical simulation result using the CFD method; Fig.11 The middle figure (c) is the main control mode diagram in the downstream direction of the research results of the two-dimensional nonlinear dynamic model of the top tension riser to study the coupled displacement response of nonlinear vortex-induced vibration; Fig.12 The middle figure (e) is the main control mode diagram in the cross-flow direction of the vortex-induced vibration response experimental results of a certain ocean center; Fig.12 The middle figure (f) is the main control mode diagram in the cross-flow direction of the numerical simulation results using the CFD method; Fig.12 The middle figure (g) is the main control mode diagram in the cross-flow direction of the research results of the two-dimensional nonlinear dynamic model of the top tension riser to study the coupled displacement response of nonlinear vortex-induced vibration.

[0126] By comparing them one by one, it can be found that the main control modes of the riser in the downstream and transverse directions under the simulation of the method in this embodiment are the same as the above three results, which are the second-order mode and the first-order mode respectively. The calculation results of the model in this paper are basically the same as the envelope contours of the experimental method and the numerical method, and are in better agreement with the experimental data.

[0127] When a large deviation is found in the subsequent verification process, the parameters of each model in this embodiment can be corrected by a parameter calibration method to improve the solution accuracy.

[0128] S6. Extract the characteristic parameters of vortex-induced vibration, and draw the instantaneous dimensionless displacement envelope in the transverse direction and the instantaneous dimensionless displacement envelope in the downstream direction, the displacement response duration curve, the center of mass motion trajectory and the frequency amplitude schematic diagram of the deep-sea mining pipe by using the data visualization method, such as Fig.13 shown.

[0129] Specifically, after the above calculations are completed, the results can be analyzed using Fluent's post-processing tools or in combination with other post-processing tools, and the above schematic diagram can be obtained through visual analysis. With these visualized data, optimization can be performed in actual projects to avoid resonance and major fatigue damage to mining pipes and ensure construction safety. Fig.14 , Fig.15 , Fig.16 As shown. Fig.14 In this paper, the vibration modes of mining pipes are mainly analyzed. After understanding the vibration displacement and several vibration modes of the structure, the actual vibration response of the structure under the action of external or internal vibration sources can be predicted, thereby avoiding the occurrence of resonance. Further, it can provide a basis for the optimal design of the structure, and improve the seismic performance and service life of the structure by changing design parameters such as size and material. Fig.15In the analysis, we can clearly observe the changing trend of the maximum displacement of the bottom of the mining pipe with the change of the reduced velocity. The analysis results can ensure the safety and stability of the marine riser and avoid deviations under large displacement deformation conditions, thereby ensuring the normal operation of the deepwater floating production system. Fig.16 The purpose of frequency spectrum analysis of the vibration response of a structure is to ensure the safety and reliability of the structure by simulating and analyzing the response of the structure under loads of different frequencies, especially to protect the structure from damage by predicting and avoiding resonance when facing loads that may cause resonance.

[0130] In summary, the specific embodiment of the present invention establishes a quasi-three-dimensional vortex-induced vibration model of a deep-sea mining pipe based on a double-degree-of-freedom cylinder and a traditional two-end hinged riser model. In the same time step, the fluid domain is first calculated to obtain the fluid force; the fluid force obtained by the solution is combined with the Newmark-β method into the structural motion equation of the mining pipe through a self-compiled program to solve the motion data of the mining pipe, so as to calculate the solid domain; and then the motion data is transmitted back to the fluid domain in combination with the dynamic mesh technology to update the mesh to achieve bidirectional coupling. Then enter the next time step, and realize the characteristic analysis of vortex-induced vibration of sea mining pipe through the quasi-three-dimensional numerical simulation method of coupling two-dimensional fluid domain and three-dimensional solid domain based on slicing method; construct a new model for vortex-induced vibration analysis of deep-sea mining pipe with one end fixed and one section free by dividing the two-dimensional fluid domain by slicing method and combining with the quasi-three-dimensional numerical simulation method of three-dimensional solid domain; while ensuring the high accuracy and calculation precision of the mining pipe model, because of the use of slicing technology, there is no need to perform full grid division on the entire flow field domain, which greatly reduces the computing resources required for three-dimensional simulation; in the riser structure domain, a three-dimensional calculation model of the riser is established based on the finite element method, and the riser stiffness equation is solved by the Newmark-beta method. The riser solution process is embedded in Fluent through the UDF interface and solved in combination with the slicing method, which fits the characteristics of the three-dimensional riser to the greatest extent.

[0131] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for analyzing the characteristics of vortex-induced vibration of deep-sea mining pipes, characterized in that the steps include: S1. Based on the geometric structure of the deep-sea mining pipe, a structural model of the deep-sea mining pipe is established by the finite element method; S2. Establish the flow field model of the deep-sea mining pipe fluid domain by slicing method; Calculating a fluid control equation based on the flow field model, and solving the fluid control equation to obtain a flow field force acting on the deep-sea mining pipe; S3, establishing a kinematic model of the deep-sea mining pipe based on the structural model and the flow field force, solving the kinematic model by a numerical solution method, and obtaining motion data of the deep-sea mining pipe; S4. Based on the flow field force and the motion data, the flow field model and the kinematic model are coupled by a dynamic mesh technology to obtain a vortex-induced vibration model of a deep-sea mining pipe; The vortex-induced vibration model of the deep-sea mining pipe is solved to obtain the vortex-induced vibration characteristic parameters of the deep-sea mining pipe.

2. The characteristic analysis method based on vortex-induced vibration of deep-sea mining pipe according to claim 1 is characterized in that: The pipe body of the deep-sea mining pipe is divided into a plurality of finite element nodes; The number of the finite element nodes is 4-6 times the number of slices divided by the slicing method.

3. The characteristic analysis method based on vortex-induced vibration of deep-sea mining pipe according to claim 1 is characterized in that: In S2, the flow field model establishment process includes: Divide the fluid domain into multiple flow field slices; The grid is divided on each flow field slice by using overlapping grid technology and moving grid technology.

4. The characteristic analysis method based on vortex-induced vibration of deep-sea mining pipe according to claim 3 is characterized in that: In the mesh division of the flow field slice, the foreground mesh is an O-type segmentation mesh.

5. The method for analyzing the characteristics of vortex-induced vibration of deep-sea mining pipe according to claim 1, characterized in that: In S2, the fluid control equation is solved by the continuity equation and the NS equation.

6. The characteristic analysis method based on vortex-induced vibration of deep-sea mining pipe according to claim 1 is characterized in that: In S3, the structural basis of the kinematic model is a beam model; In the beam model, the tube body between two nodes is equivalent to a beam unit, and the upper end is hinged and the lower end is freely set.

7. The method for analyzing the characteristics of vortex-induced vibration of deep-sea mining pipe according to claim 6 is characterized in that: In S3, the motion data solving step includes: S31, discretely calculate the stiffness matrix, mass matrix, damping matrix and load column vector of each unit; S32, based on the calculation results of S31, combining and calculating the overall stiffness matrix, mass matrix, damping matrix and load column vector of the pipe body; S33, substituting the calculation result of S32 into the kinematic model, and obtaining the motion data by iteratively solving through the Newmark-beta method.

8. The method for analyzing characteristics of vortex-induced vibration of deep-sea mining pipe according to claim 1, characterized in that: In S4, the coupling process includes: Synchronously substituting the motion data into the fluid control equation and updating the flow field force; The updated flow field force is substituted into the kinematic model, and the motion data is updated.

9. The method for analyzing characteristics of vortex-induced vibration of deep-sea mining pipe according to claim 1, characterized in that: Also includes: The vortex-induced vibration characteristic parameters are verified based on experimental or simulation data, and the vortex-induced vibration model of the deep-sea mining pipe is corrected by a parameter calibration method.

10. The method for analyzing characteristics of vortex-induced vibration of deep-sea mining pipe according to claim 1, characterized in that: Also includes: The vortex-induced vibration characteristic parameters are extracted, and the transverse-flow instantaneous dimensionless displacement envelope, the downstream instantaneous dimensionless displacement envelope, the displacement response duration curve, the center of mass motion trajectory and the frequency amplitude schematic diagram of the deep-sea mining pipe are drawn through the data visualization method.

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