Method for predicting three-dimensional motion response of floating tunnel pipe body under wave-current combined excitation

Abstract

The invention discloses a three-dimensional motion response prediction method for a floating tunnel pipe body under wave-current combined excitation, and belongs to the technical field of underwater floating tunnels. In order to solve the problem of poor prediction accuracy of motion response prediction of a floating tunnel pipe body in which a three-dimensional real model of the floating tunnel pipe body is simplified into a two-dimensional plane model, the method comprises the following steps: firstly, establishing a wave-current combined excitation three-dimensional numerical pool based on a boundary wave making method; then, carrying out overlapped grid and wave grid division based on STAR CCM +, establishing a fluid-structure interaction numerical simulation model, establishing a relation between a floating tunnel pipe body and the seabed through a tensioning catenary, further establishing a three-dimensional floating tunnel numerical model under wave-current combined excitation, and based on numerical simulation, establishing a three-dimensional floating tunnel model; and respectively performing parameter sensitivity analysis on the important nonlinear influence factors of the floating tunnel, and analyzing the influence of sensitive parameters on the vibration response characteristic rule of the floating tunnel pipe body so as to realize three-dimensional motion response prediction of the floating tunnel pipe body under wave-current combined excitation.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater suspended tunnels, and in particular relates to a method for predicting three-dimensional motion response of a suspended tunnel pipe body. Background Art

[0002] With the development of science and technology, cross-sea channels such as undersea tunnels and cross-sea bridges are being rapidly built around the world, greatly promoting economic and cultural exchanges. However, traditional cross-sea channels face many challenges, such as high construction costs, environmental impacts, and safety hazards. As an innovative solution, the Submerged Floating Tunnel (hereinafter referred to as the floating tunnel) has many advantages: low ecological impact, flexible construction, high disaster resistance, and strong ability to adapt to terrain. With the continuous advancement of technology, the application prospects of floating tunnels will be broader around the world, and it is expected to provide an effective alternative to solve the difficulties in the construction of traditional cross-sea channels.

[0003] The suspended tunnel consists of a standard segment tubular structure, an underwater anchoring system (or an above-water floating structure), and a revetment section connected to the shore. The tubular structure balances the external and internal loads during the construction and operation stages through the net buoyancy and support system, and has a complete force system. At present, suspended tunnels are divided into three types according to the support method: pier type, pontoon type, and anchor cable type. The pier type is supported by piers and is suitable for shallow water areas, but it is costly and technically difficult in deep water. The pontoon type is stable through a surface pontoon and is easily affected by wind and waves and ship collisions. The anchor cable type fixes the pipe body 20-30 meters below the water surface through underwater anchor cables. It is less affected by external factors, has strong adaptability, and has little impact on the environment. In summary, compared with pier type and pontoon type suspended tunnels, the anchor cable suspended tunnel has stronger spanning and terrain adaptability. In addition, the design and construction of its anchoring system can draw on mature marine platform technology. Therefore, the anchor cable suspended tunnel has become the most practical and promising form of suspended tunnel. When complex environmental loads act on the suspended tunnel body, the periodic loads will cause the structure to move. As a large underwater structure, the design and maintenance of the suspended tunnel must be particularly cautious. Once the structure is damaged, it will not only cause huge economic losses, but also irreparable casualties. In order to ensure the safety of pedestrians and vehicles inside the suspended tunnel body, it is necessary to ensure that the tunnel body can work safely and stably under the action of complex marine environmental loads, which is also one of the key goals of suspended tunnel design and research.

[0004] Underwater suspended tunnels are easily affected by the complex environmental loads around them. In particular, under the continuous action of ocean currents and waves, the suspended tunnel body is very likely to have dangerous motion responses such as vortex-induced resonance, which poses a great threat to the stability and safety of the suspended tunnel during normal operation. Therefore, it is an important prerequisite to ensure the safety of pedestrians and vehicles in the suspended tunnel to develop a stable and reliable numerical prediction method for the three-dimensional motion response of the suspended tunnel body under the combined excitation of waves and currents, and to deeply analyze the coupled dynamic response characteristics of the suspended tunnel body under the combined excitation of waves and currents based on this method. The research on the dynamic response of the suspended tunnel body under the combined excitation of waves and currents can be roughly divided into three categories according to the research methods: model experimental research, theoretical calculation research and numerical calculation research. Compared with model experiments and theoretical calculation methods, numerical calculation research based on computational fluid dynamics (CFD) methods has the advantages of low research cost and few empirical model coefficients, and is particularly suitable for large-scale parameter influence feature analysis. Current theoretical and computational research often simplifies the three-dimensional real model of the suspended tunnel body into a two-dimensional plane model. Although this simplified processing method can effectively reduce the computational complexity to a certain extent, it is difficult to truly reflect the three-dimensional motion response characteristics of the actual pipe structure, and further leads to an incomplete understanding of the dynamic behavior of the pipeline under the combined excitation of waves and currents. In addition, in the current model experimental research, due to the high experimental costs and limited technical conditions, researchers are usually unable to accurately capture the complex interaction between fluid and structure when analyzing the three-dimensional motion response of the suspended tunnel pipe under the combined excitation of waves and currents, which leads to an in-depth and inaccurate understanding of the dynamic behavior of the pipeline. Summary of the invention

[0005] The invention aims to solve the problem of poor prediction accuracy in the prediction of the motion response of a suspended tunnel tube body by simplifying the three-dimensional real model of the suspended tunnel tube body into a two-dimensional plane model.

[0006] A method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation comprises the following steps:

[0007] S1. A three-dimensional floating tunnel numerical model under wave-current combined excitation is established based on STAR CCM+, including:

[0008] S101. Establish a three-dimensional numerical water pool with wave and current joint excitation based on the boundary wave making method;

[0009] S102, Overlap grid, wave grid division, and establishment of fluid-solid coupling numerical simulation model:

[0010] First, determine the parameters, including the style and size of the floating tunnel body, anchor cable stiffness k, submergence depth d, flow velocity U, water depth h, wave amplitude A and wave period T, and then perform meshing and numerical simulation; in the process of meshing and numerical simulation, first create geometric components based on STAR CCM+, including: background basin components, wave propagation area components, floating tunnel body components and encrypted area components, generate overlapping area components in Boolean operations, and then create two areas for the geometric components, namely the background area and the overlapping area; then perform meshing, draw the background grid, overlapping grid, wave grid and encrypted grid respectively; select the overlapping grid for subsequent numerical simulation;

[0011] Then, the previously set grid file is loaded through STAR CCM+ software. First, the physical model is created. The fluid domain volume model is selected for the multiphase flow model. Two new calculation phases, water and air, are created based on the multiphase-Euler term node, and waves are created. Then, the boundary types of each surface are set according to the wave breaking type, and the overlapping grid boundaries are set to the overlap format. Then, the parameters of the suspended tunnel body and anchor chain are set in the DFBI node. Finally, the entire flow field is initialized according to the flow field data determined before the numerical simulation, and the calculation step size is selected for calculation.

[0012] S103. Based on the volume coupling module in STAR CCM+ software, the connection between the suspended tunnel body and the seabed is established through a tensioned catenary, and then a three-dimensional suspended tunnel numerical model under wave and current combined excitation is established;

[0013] S2. Based on the established three-dimensional floating tunnel numerical model under wave-current combined excitation, numerical simulation is carried out, and parameter sensitivity analysis is performed on the important nonlinear influencing factors of the floating tunnel. The influence of sensitive parameters on the vibration response characteristics of the floating tunnel body is analyzed to realize the prediction of the three-dimensional motion response of the floating tunnel body under wave-current combined excitation.

[0014] Furthermore, the process of establishing a three-dimensional numerical water pool for wave-current joint excitation based on the boundary wave making method in step 1 includes:

[0015] Firstly, a stable wave numerical pool is constructed by using the boundary wave generation method;

[0016] Next, by comparing the wavefront lift heights at different locations with the theoretical values, the computational domain size and mesh profile parameters are determined based on numerical accuracy and computational cost.

[0017] Finally, the same set of grids is used to establish a uniform incoming flow to construct a three-dimensional numerical water pool with wave-current joint excitation.

[0018] Furthermore, the process of constructing a stable wave numerical pool using the boundary wave generation method includes the following steps:

[0019] The bottom boundary of the flow field is set as the wall boundary condition, the left and right sides of the flow domain and the two front and rear symmetrical planes are set as velocity inlets, the top of the flow domain is set as the pressure outlet, and a wave-breaking zone is set at the velocity inlet boundary.

[0020] Furthermore, the wave-breaking zone is realized based on a force wave-breaking method.

[0021] Furthermore, in the process of using the same set of grids to establish a uniform incoming flow to construct a three-dimensional numerical water pool with wave-current joint excitation, it is also necessary to establish a numerical calculation model of the suspended tunnel under the action of the uniform incoming flow, and perform numerical verification to verify the reliability of the established three-dimensional numerical wave-current water pool.

[0022] Furthermore, the process of establishing the connection between the floating tunnel body and the seabed through the tensioned catenary includes:

[0023] A coordinate system Oxz is established, where O is located on the free water surface, Oz is upward and the anchor point of the anchor chain is fixed directly below O. The anchor chain moves in the Oxz plane, G is the upper mooring point of the anchor chain, X and Z are the projection lengths of the overhanging part of the anchor chain in the x and z directions, respectively, and S o is the distance between the anchor chain touchdown point and the anchor point on the seabed; the upper end of the anchor chain is subjected to a tensile force T, and the projections of T in the x and z directions are F h and F v ;

[0024] F v =S T w+V0

[0025]

[0026] Among them, F b is the bottom tension of the catenary, F k is the rigidity coefficient of the catenary, n is the correction factor, v is the vertical tension at the fixed point, v0 is the initial vertical tension at the fixed point, w is the wet weight per unit length of the anchor chain, E is the elastic modulus of the anchor chain, A is the effective cross-sectional area, V0 is the tension at the fixed point of the anchor chain, S T is the total length of the unstretched anchor chain;

[0027] Based on the above force relationship and combined with the mechanical behavior of the catenary, the overall motion response of the floating body is determined.

[0028] Furthermore, the mechanical behavior of the catenary in the overall motion response of the floating body is determined as follows:

[0029] In the mooring problem of an ocean floating body, it is first necessary to calculate and determine the initial shape of the anchor chain based on the boundary conditions at the upper end point G of the anchor chain; then, in each time step, the tension of the anchor chain is recalculated according to the change in the position of point G during the movement of the floating platform.

[0030] Furthermore, the process of performing numerical simulation based on the established three-dimensional floating tunnel numerical model under wave-current combined excitation in S2 includes:

[0031] Based on the three-dimensional numerical water pool, the corresponding wave and current parameters are set, wave and current loads are added, and then the fluid-solid coupling numerical simulation model is run until the vibration response of the suspended tunnel body reaches a stable state; the parameter sensitivity analysis of the important nonlinear influencing factors of the suspended tunnel is carried out using the fluid-solid coupling numerical simulation model.

[0032] Furthermore, the important nonlinear influencing factors of the suspended tunnel include flow velocity, wave parameters, water depth, burial depth, buoyancy-to-weight ratio and mooring angle, and size of the suspended tunnel.

[0033] Beneficial effects:

[0034] The present invention proposes a numerical prediction method for the three-dimensional motion response of a suspended tunnel tube, which can more accurately simulate the influence of wave-current combined excitation on the vibration of the tube, thereby providing more reliable data support for engineering design and safety assessment. At the same time, the present invention also innovatively proposes a high-precision numerical prediction model, which can effectively simulate the complex interaction between fluid and structure, and systematically analyze the influence characteristics of fluid on the motion of the tube, and can deeply understand the dynamic behavior of wave and current on the suspended tunnel tube, thereby providing more reliable theoretical basis and data support for actual engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the three-dimensional modeling and simulation logic diagram of the suspended tunnel body.

[0036] Figure 2 Schematic diagram of the wave-current joint excitation field.

[0037] Figure 3 Schematic diagram of overlapping grids.

[0038] Figure 4 This is a flow chart for predicting the motion response of a suspended tunnel body based on a three-dimensional numerical model.

[0039] Figure 5 Schematic diagram of the catenary.

[0040] Figure 6 It is a three-dimensional numerical water pool model in the embodiment.

[0041] Figure 7 Figure 2 is a graph of the wave surface time history curves at different monitoring points, where (a) represents the wave surface time history curve at one wavelength, (b) represents the wave surface time history curve at three times the wavelength, and (c) represents the wave surface time history curve at six times the wavelength.

[0042] Figure 8Wave surface cloud diagram in the computational domain when the wave period is 5 times.

[0043] Fig. 9 Schematic diagram of the three-dimensional model of the underwater suspended tunnel.

[0044] Fig.10 Schematic diagram of wave propagation in the flow field around the suspended tunnel tube under combined wave and current excitation.

[0045] Fig.11 This is the velocity contour of the flow field around the suspended tunnel tube under the combined excitation of waves and currents.

[0046] Fig.12 It is a horizontal swing duration curve.

[0047] Fig.13 is the sway acceleration duration curve.

[0048] Fig.14 It is the heave duration curve.

[0049] Fig.15 is the heave acceleration duration curve.

[0050] Fig.16 is the motion trajectory curve.

[0051] Fig.17 This is the wave-facing anchor chain force and its length duration curve.

[0052] Fig.18 It is the back wave anchor chain force and its length duration curve. DETAILED DESCRIPTION

[0053] In view of the problems existing in the background technology, the present invention designs a new numerical prediction method for the three-dimensional motion response of the suspended tunnel tube under wave-current combined excitation. This method can accurately predict and analyze the three-dimensional dynamic response characteristics of the suspended tunnel tube under wave-current combined excitation, thereby providing a reliable theoretical basis and technical support for the safe and stable operation of the tunnel tube. First, a wave numerical pool is built, and a uniform flow is added to the wave numerical pool to establish a three-dimensional numerical pool with wave-current combined excitation. Then, the coupled vibration response of the three-dimensional suspended tunnel tube is realized based on the DFBI (Dynamic FluidBody Interaction) model and overlapping grid technology. The following is an explanation in conjunction with a specific implementation method.

[0054] Specific implementation method 1: Combination Figure 1 and Figure 2 To explain this embodiment,

[0055] This embodiment is a method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation, comprising the following steps:

[0056] Step 1: Establish a three-dimensional numerical water pool with wave-current joint excitation based on the boundary wave method:

[0057] First, a stable wave numerical pool should be built. The present invention comprehensively considers the calculation speed, accuracy and adaptability to the incoming flow conditions and selects the velocity boundary wave method. A two-phase flow model is used to distinguish the air phase from the water phase, and the VOF (Volume of Fluid) multiphase flow method is used to capture the changes in the free liquid surface. This method can analyze the position and shape of the multiphase flow interface, and can predict the distribution and movement of the multiphase flow interface. The distribution of the phase and the position of the interface are described by the phase volume fraction. The boundary wave method is used to make waves, and the bottom boundary of the flow field is set as the wall boundary condition. The left and right sides of the flow domain and the two symmetrical planes in front and back are set as the velocity inlet, and the top of the flow domain is set as the pressure outlet. In order to prevent the influence of wave reflection at the boundary, a wave-breaking zone is set at the velocity inlet boundary. At present, the main wave-breaking methods are damping wave-breaking and force wave-breaking. Considering the calculation accuracy and computing resources, the present invention uses the force wave-breaking method. This method can not only eliminate the reflected waves on the boundary, but also set a smaller calculation domain to reduce the number of grids.

[0058] Next, by comparing the wave lift heights at different positions with the theoretical values ​​and comprehensively considering the numerical accuracy and computational cost, the appropriate computational domain size and grid profile parameters are selected to verify the wave simulation capability of the numerical water tank, and the setting of the grid parameters is confirmed by simulating the waves.

[0059] Finally, the same set of grids is used (i.e., uniform incoming flow is added after the wave generation is successful, without changing the grid) to establish uniform incoming flow to construct a three-dimensional numerical water pool with wave and current joint excitation;

[0060] Subsequently, a numerical calculation model of a suspended tunnel under the action of uniform incoming flow is established to verify the three-dimensional numerical water pool, which can be compared with previous numerical verifications to further verify the reliability of the established three-dimensional numerical wave flow water pool.

[0061] Step 2: Overlapping grid, wave grid division and fluid-solid interaction numerical simulation:

[0062] First, a series of parameters are determined, including the style and size of the floating tunnel body, anchor cable stiffness k, submergence depth d, flow velocity U, water depth h, wave amplitude A and wave period T, followed by meshing and numerical simulation.

[0063] The meshing process is as follows:

[0064] Overlapping grids are used for subsequent numerical simulations. Overlapping grid technology uses interpolation between overlapping areas to achieve data transfer between component grids and background grids. Overlapping grids are selected for two reasons:

[0065] (1) Overlapping grid is one of the dynamic grid numerical simulation methods. It allows for more detailed grid division in key areas, improves the ability to capture local flow characteristics, and is more suitable for the study of the vibration response of suspended tunnels, laying a foundation for subsequent studies of the vibration response of suspended tunnels.

[0066] (2) By using overlapping grids, users can apply different physical models and boundary conditions to each area without having to re-divide the entire grid.

[0067] Taking the classic circular cross-section suspended tunnel body as an example, the overlapping grid division method to be used in the present invention is as follows: Figure 3 shown.

[0068] Relying on the powerful grid division technology of STAR CCM+ software, background grid, overlapping grid, wave grid and encrypted grid are drawn respectively.

[0069] The specific steps of mesh division are as follows:

[0070] 1. First, create geometric components, including background watershed components, wave propagation area components, suspended tunnel body components, and densified area components to ensure that the model meets the analysis requirements; generate overlapping area components in Boolean operations, and then create two areas for the geometric components, namely the background area and the overlapping area.

[0071] 2. You must create an interface between the background region and the overlap region. Select both the Region (summary point) > Background and Overlap nodes. Right-click on either of the selected nodes and select Create Interface > Overlap Mesh. > indicates the next step of processing.

[0072] 3. Then set the mesh parameters in the Operation bar, define the mesh type and refinement level for each region separately to ensure that it adapts to different flow characteristics. Right-click Geometry > Operation Node, then select New > Mesh > Automatic Mesh, select Background Basin Component in the Component List of the Create Automatic Mesh Operation dialog box, then select Surface Reconstruction and Cut Volume Mesh Cell Generator, click OK, and rename the new automatic mesh node to Background.

[0073] 4. Next, create a second mesh operation called Overlap by copying the Background Auto Mesh operation. Right-click the Operations > Background node and select Copy, right-click the Operations node and select Paste. Rename the copy of Background to Overlap, select Operations > Overlap, and set the Input Components to Overlap.

[0074] 5. Set the base size of the background mesh operation and apply volume control. Select Operation > Background > Default Control > Base Size node to set the base size of the mesh. Right-click Operation > Background > Custom Control node and select New > Volume Control to import the encrypted component. If you want to add multiple encrypted area meshes, repeat the above steps to create a new volume control.

[0075] 6. Set the base size for the Overlap Mesh operation and then add a volume control to refine the area around the floating tunnel body. Select Operation > Overlap > Default Controls > Base Size node and set the value to the same size as the background mesh. Create a custom volume control for the Overlap Mesh operation and rename it Tunnel Body. Select Custom Controls > Tunnel Body and set the component to Floating Tunnel Body. Then activate the Custom Size node and set the Target Size parameters.

[0076] 7. Create a volume control for the wave region: Continue with the background operation settings, create a custom volume control, and rename it Wave. Activate the Custom Size selection option for Surface Reconstruction and set the Relative Size to a basis percentage of 100.0. Select Wave>Control>Cut Volume Mesher node and activate Custom Anisotropic Size. Select Water Wave>Value>Cut Volume Mesher Anisotropic Size node and activate Custom Size (X), Custom Size (Y), and Custom Size (Z). Custom Size (X) and Custom Size (Y) are generally set to 1 / 80-1 / 100 of the wavelength, and Custom Size (Z) is generally set to 1 / 20 of the wave height.

[0077] 8. Generate and visualize the mesh: Select the Generate Volume Mesh option in the Mesh menu. To visualize the mesh, create a mesh scene, right-click the scene, and select New Scene > Mesh.

[0078] It is worth noting that in order to minimize the errors caused by interpolating variables between two grids, the same grid density order of magnitude is used in the overlapping area of ​​the overlap and background grids.

[0079] The process of the numerical simulation is as follows:

[0080] Load the previously set grid file through STAR CCM+ software, first create a physical model, select a three-dimensional, multiphase, implicit unsteady model, select the SST (Menter) K-Omega model as the turbulence model, select the fluid domain volume (VOF) model as the multiphase flow model, and select the gravity acceleration direction vertically downward with a magnitude of 9.81m / s 2 , then open the Multiphase - Euler Term node, create two new calculation phases, water and air, and create waves in the VOF Wave>Wave node.

[0081] Then, according to different wave elimination types, set the surface boundary types. The present invention adopts the force wave elimination method, which can not only eliminate the reflected waves at the boundary, but also reduce the amount of calculation by using a small-sized calculation domain. Set the wall of the suspended tunnel, the bottom boundary of the flow field, and the front and rear symmetric plane boundaries as wall boundary conditions, set the left and right sides of the flow domain as velocity inlets, and the top of the flow domain as pressure outlets, and set the overlapping grid boundaries to the overlapped grid format. Then create a DFBI rotation and translation in the Tools>Motion node, and set the suspension tunnel body and anchor chain parameters in the DFBI node. Finally, initialize the entire flow field according to the flow field data determined before the numerical simulation, and finally select an appropriate calculation step size for calculation.

[0082] The specific steps of numerical simulation are as follows:

[0083] (1) Import files

[0084] Open the STAR CCM+ software, select the appropriate number of working cores, load the prepared mesh file from the File option in the toolbar, and click OK.

[0085] (2) Create a Region and Set the Boundary Type

[0086] To create a region based on the background and overlapping components, select Geometry > Components > Background and Overlap nodes. Right-click any of the selected nodes and select Assign Components to Region. In the pop-up dialog box, select:

[0087] (a) Set the region mode to create a region for each component.

[0088] (b) Set the boundary mode to create one boundary for each component surface.

[0089] (c) Select Do not create interface based on contacts.

[0090] Then click Apply and then Close. Then, according to the force wave elimination method, specify the correct type for the boundaries of each region, set the floating tunnel wall and the bottom boundary of the flow field as wall boundary conditions, set the left and right sides of the flow domain and the two symmetrical planes in front and back as velocity inlets, the top of the flow domain as pressure outlets, and set the overlapping grid boundaries to the overset format.

[0091] (3) Select Physical Model:

[0092] Select the physical continuum, Continuum>Physics 1, select the following models in order, three-dimensional, implicit unsteady, multiphase, multiphase interaction (automatic selection), fluid volume (VOF), turbulence model, SST (Menter) K-Omega model, gradient (automatic selection), separated flow (automatic selection), multiphase equation of state (automatic selection), and check gravity and VOF wave in the optional models, and finally click OK.

[0093] (4) Create Euler phase:

[0094] Right-click the Continuum > Physics 1 > Model > Multiphase > Euler Phase node and select New. A new node, Phase 1, is created. Rename the Phase 1 node to Water. Next, right-click the Euler Phase > Water > Model node and select Select Model: Select Liquid from the Material combo box. Select Constant Density from the Equation of State combo box and click Close. Repeat the above steps to create a second Euler phase, selecting Gas from the Material Model and click Close. Rename the second phase to Air.

[0095] (5) Set up DFBI campaign:

[0096] Click Tools > Motion Node, right-click the Motion node, and then select New > DFBI Rotation and Translation. A new node named DFBI Rotation and Translation is added to the Motion Manager.

[0097] (6) Set up a 6-DOF body:

[0098] Select the Regions > Overlays > Physics > Motion Assignment node and set the motion to DFBI Rotation and Translation. Then right-click the DFBI > 6 DOF Body node and select New Body > 3D > Continuum. Also rename Body 1 to Suspended Tunnel.

[0099] (7) Parameter setting of suspended tunnel:

[0100] Select DFBI>6DOF Body>Suspension Tunnel node, then click the Custom Editor for Body Surface. The Suspension Tunnel - Body Surface dialog box appears, set the suspension tunnel mass in the Body Mass column. Then set the moment of inertia in the InitialValues>Motion ofInertia node, then click the Free Motion node, check X Motion, YMotion, YRotation, and activate the X-axis translation, Z-axis translation, and Y-axis rotation properties.

[0101] (8) VOF wave setting:

[0102] Right-click Continuum > Physics 1 > Model > VOF Wave > Wave Node and select New > First-Order Wave. Rename the First-Order VOF Wave 1 node to First-Order Wave. Select the First-Order Wave node and set the location of the water level.

[0103] (9) Initial Conditions settings:

[0104] Click the Continuum > Physics 1 > Initial Conditions > Volume Fraction node, select Composite in the Property Method column, then click the Volume Fraction > Composite > Air node, select Field Function in the Property Method column, select Volume Fraction of Light Fluid of First Order Wave 1 in the Scalar Function column, then click the Volume Fraction > Composite > Water node, select Field Function in the Property Method column, select Volume Fraction of Heavy Fluid of First Order Wave 1 in the Scalar Function column. Click the Initial Conditions > Velocity node, select Field Function in the Property Method column, select Velocity of First Order VOF Wave 1 in the Vector Function column. Then click the Initial Conditions > Pressure node, select Field Function in the Property Method column, and select Hydrostatic Pressure of First Order VOF Wave 1 in the Scalar Function column.

[0105] (10) Boundary Conditions settings:

[0106] Click the Region>Background>Physical Value node with your mouse, and select First-order VOF wave 1 in the Force VOF wave specification column. Then click the Background>Physical Condition node, and select Force in the VOF wave area options column. Then click the Region>Background>Boundary>inlet node, and set the velocity to Component in the Physical Conditions, click the Physical Value>Velocity node, select Field Function in the Property Method column, and select Velocity of First-order VOF wave 1 in the Vector Function column. Then in the Physical Value>Volume Fraction node, set the air and water phases to Volume Fraction ofLight Fluid ofFirst-order wave 1 and Volume FractionofHeavy Fluid ofFirst-order wave 1, respectively. The outlet and symmetry settings are the same as inlet, and repeat the above steps. Then click the top>Physical Value node, set the volume fraction and pressure. The volume fraction settings are the same as above, and select Hydrostatic Pressure ofFirst-order VOF wave 1 in the Pressure column.

[0107] (11) Solver Parameters settings:

[0108] Click on the Solver > Implicit Unsteady node and set the desired time step.

[0109] (12) Stop Condition setting:

[0110] Click the Stop Condition > Maximum Internal Iterations node and select the maximum number of internal iterations. Then click the Stop Condition > Maximum Physical Time node and set the maximum physical time. Finally, click the Stop Condition > Maximum Steps node and disable Enable.

[0111] (13) Visual Solution of the Scene settings

[0112] Right-click the scene node and select Create a new scene.

[0113] (14) Initialize Solution settings:

[0114] Click the flag icon (Initialize Solution) or click Solution>InitializeSolution to complete the calculation initialization.

[0115] (15) Run Calculation settings:

[0116] Click the Run button with the mouse and the calculation starts.

[0117] Step 3: Establish an accurate three-dimensional floating tunnel numerical model under wave-current combined excitation:

[0118] The suspended tunnel is mainly subject to three types of forces: anchor cable tension, self-gravity and fluid force. In still water, the anchor cable will be tightened to generate pre-tension, the magnitude of which is the difference between the buoyancy of the pipe section and the gravity. The stability of the suspended tunnel requires that the anchor cable always maintains tension, that is, the vertical force on the suspended tunnel pipe under any working condition must be less than the buoyancy of the pipe section. Therefore, the anchor cable connected to the suspended tunnel can be simplified as a supporting structure that is tensile but not compressed. Existing software is usually based on static or linear force models when dealing with anchor cables in other structures (such as platforms or bridges). However, in the prediction process of the suspended tunnel, the mechanical behavior of the anchor cable exhibits significant nonlinear characteristics, especially under the action of waves and water flow, the anchor cable will undergo large nonlinear deformation, and this deformation needs to be dynamically adjusted in combination with environmental changes.

[0119] In the present invention, based on the body coupling module in the STAR CCM+ software, a connection is established between the suspended tunnel body and the seabed through a tensioned catenary. The catenary model can reasonably distribute the tension so that the vertical force of the suspended tunnel can be effectively transmitted to the seabed or the anchoring structure through the anchor cable, ensuring that the anchor cable is in a reasonable stress state and avoiding unnecessary compression force. The complexity of the suspended tunnel body lies in that it not only has to deal with the influence of fluid dynamics, but also needs to consider the mechanical behavior of the anchor cable, the buoyancy of the body itself, and the coupling between other environmental loads. This special coupling mode brings great challenges to model establishment, and also highlights the innovative depth of this application in the coupled multi-field analysis method.

[0120] Theoretical formula of tensioned catenary:

[0121] like Figure 5 The coordinate system Oxz shown, O is located on the free water surface, Oz is upward, and the seabed anchor point of the anchor chain is fixed directly below point O. Assuming that the seabed is flat, the anchor chain moves in the Oxz plane, G is the upper mooring point of the anchor chain, X and Z are the projection lengths of the overhanging part of the anchor chain in the x and z directions respectively, S o It is the distance between the anchor chain contact point and the anchor point on the seabed. The upper end of the anchor chain is subjected to a tensile force T, and the projections of T in the x and z directions are F h and F v .

[0122] F v =S T w+V0

[0123]

[0124] Among them, F b is the bottom tension of the catenary, which usually occurs at the lowest point of the catenary (i.e. the place closest to the anchor point), F k is the rigidity coefficient of the catenary, n is the correction factor, where n = 1, v is the vertical tension at the fixed point, v0 is the initial vertical tension at the fixed point, w is the wet weight per unit length of the anchor chain, E is the elastic modulus of the anchor chain, A is the effective cross-sectional area, V0 is the tension at the fixed point of the anchor chain, S T It is the total length of the unstretched anchor chain.

[0125] In the mooring problem of an ocean floating body, the initial shape of the anchor chain must first be calculated and determined based on the boundary conditions (force or position) at the upper end point G of the anchor chain. Then, in each time step, the tension of the anchor chain is recalculated according to the change in the position of point G during the movement of the floating platform, and the mechanical behavior of the catenary is obtained, and finally the overall motion response of the floating body is determined.

[0126] The present invention realizes the coupled vibration response of the three-dimensional suspended tunnel body based on the DFBI (Dynamic FluidBody Interaction) model and the overlapping grid technology. The specific implementation process is as follows:

[0127] The anchor cable suspension tunnel model was established by STAR CCM+ software modeling. A catenary was added to the body coupling module. The end position of the catenary was determined according to the mooring angle and water depth. Then, the corresponding wave and current parameters were set in the wave generation module, wave and current loads were added, and finally, the fluid-solid coupling numerical simulation model was run until the vibration response of the suspension tunnel body reached a stable state. Figure 4 As shown in the figure, this numerical model is used to perform parameter sensitivity analysis on important nonlinear influencing factors such as flow velocity, wave parameters, water depth, burial depth, buoyancy-to-weight ratio, mooring angle, and suspended tunnel size, and the characteristic laws of the sensitivity parameters affecting the vibration response of the suspended tunnel body are summarized to achieve the prediction of the three-dimensional motion response of the suspended tunnel body under wave-current combined excitation.

[0128] Example

[0129] The effect of the present invention is described by this embodiment. The motion response prediction of the suspended tunnel body based on the three-dimensional numerical model of this embodiment includes the following steps:

[0130] 1. Construct a wave-current joint excitation field:

[0131] The following is a three-dimensional numerical wave pool with a total length of 800m, a width of 160m, and a height of 100m. Figure 6 As shown in the figure, waves with a wave height of 8m, a wavelength of 100m, a wave steepness of 0.08, and a wave number of 0.01 are selected for simulation, and the grid convergence and time step convergence verifications are carried out on the water pool. Considering the numerical accuracy and computational cost, the grid size is finally determined to be 80 grids on one wavelength, 15 grids in one wave height, and a time step of 0.01s.

[0132] In order to conveniently display the results of grid convergence verification and time step convergence verification, three wave height meters were placed at one wavelength, three wavelengths and six wavelengths of the numerical water pool, respectively. By monitoring the wave surface lift height at different positions and comparing it with the theoretical wave height, the feasibility of wave generation in the numerical water pool was verified. Figure 7 From the wave surface time history curves at different monitoring points, it can be seen that the actual value curves of the wave surface lifting height at three different positions are almost coincident with the theoretical value curves, indicating that the wave generation is successful. Figure 8 The wave surface cloud diagram in the calculation domain at 5 times the wave period shows that the wave propagation is very stable, indicating that the numerical water pool can perform long-term wave generation simulation.

[0133] 2. Construct a three-dimensional flow field around the suspended tunnel tube under wave and current combined excitation:

[0134] A circular suspended tunnel section with a diameter of 24m and a buried depth of 20m is selected. Fig. 9 As shown by Fig.10 , Fig.11 Schematic diagram of wave propagation in the flow field around the suspended tunnel body under the wave-current combined excitation and the velocity cloud diagram. It can be seen that the wave-current combined excitation field constructed by the present invention is relatively stable, and there is a coupling effect between the wave and the flow.

[0135] 3. Analysis of vibration response of suspended tunnel body under wave and current combined excitation:

[0136] The Coastal and Ocean Engineering Laboratory of the Department of Civil Engineering at Nagoya University in Japan conducted an experimental study on the dynamic response of a suspended tunnel under wave action. The present invention uses the actual classic suspended tunnel pipe segment for numerical calculation. The pipe diameter D is 0.25m, the distance d from the center of the suspended tunnel pipe to the water surface is 0.177m, the pipe segment mass m is 21kg, and the pipe segment length L is 0.68m. The mass per unit length of the anchor chain is 0.05kg / m, and the stiffness k is 2×10 3 The wave-current combined excitation field parameters are as follows: water depth h is 0.6 m, the parameters of the single wave field are amplitude A of 5.75 m, wavelength λ of 1.575 m, period T of 1 s, and the added flow velocity U is 0.2 m / s uniform flow.

[0137] The numerical simulation results of the dynamic response of the suspended tunnel body under wave-current combined excitation are as follows: Fig.12 Suspended tunnel body lateral swing history curve, Fig.13 Surge acceleration time history curve, Fig.14 Heave time curve, Fig.15 Heave acceleration time history curve, Fig.16 Suspended tunnel body trajectory curve, Fig.17 , Fig.18 From the time history curves of the anchor chain forces and their lengths facing the waves and the back waves, it can be seen that the dynamic response of the suspended tunnel body is relatively stable, and it will reciprocate along an elliptical trajectory that is approximately circular.

[0138] Researchers can use the above method to perform batch numerical simulations by adjusting the structural parameters of the suspended tunnel (such as cross-sectional shape, size, submergence depth, buoyancy-to-weight ratio and anchor angle) and environmental loads (such as waves and currents). On this basis, by analyzing the simulation data, we can deeply understand the dynamic response mechanism of the suspended tunnel body under the combined action of waves and currents. This research is not only of great significance to the stability and safety of the suspended tunnel during operation and engineering practice, but also provides valuable technical support for related fields. Based on the research results of the present invention, it will effectively promote the development of underwater suspended tunnel engineering in my country and promote the advancement and application of technology in this field.

[0139] Compared with the prior art, the technical solution of the present invention has the following advantages: 1. Current theoretical and computational research often simplifies the three-dimensional real model of the suspended tunnel pipe body into a two-dimensional plane model. Although this simplified processing method can effectively reduce the computational complexity to a certain extent, it is difficult to truly reflect the three-dimensional motion response characteristics of the real pipe body structure, and further leads to an insufficient understanding of the dynamic behavior of the pipeline under wave-current combined excitation. In order to overcome this limitation, the present invention proposes an innovative numerical prediction model for the three-dimensional motion response of the suspended tunnel pipe body. The model can more accurately simulate the influence of wave-current combined excitation on the vibration of the pipe body, thereby providing more reliable data support for engineering design and safety assessment. 2. In the current model experimental research, due to the high experimental cost and the limitations of technical conditions, researchers are usually unable to accurately capture the complex interaction between fluid and structure when analyzing the three-dimensional motion response of the suspended tunnel pipe body under wave-current combined excitation, which leads to an insufficient understanding of the dynamic behavior of the pipeline. In order to overcome this limitation, the present invention innovatively proposes a high-precision numerical prediction model, which can effectively simulate the complex interaction between fluid and structure, and systematically analyze the influence characteristics of fluid on the movement of the tube body. It can deeply understand the dynamic behavior of wave flow on the suspended tunnel tube body, thereby providing more reliable theoretical basis and data support for practical engineering design.

[0140] The present invention may also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation, characterized in that: Includes the following step: S1. A three-dimensional floating tunnel numerical model under wave-current combined excitation is established based on STAR CCM+, including: S101. Establish a three-dimensional numerical water pool with wave and current joint excitation based on the boundary wave making method; S102, Overlap grid, wave grid division, and establishment of fluid-solid coupling numerical simulation model: First, determine the parameters, including the style and size of the floating tunnel body, anchor cable stiffness k, submergence depth d, flow velocity U, water depth h, wave amplitude A and wave period T, and then perform meshing and numerical simulation; in the process of meshing and numerical simulation, first create geometric components based on STAR CCM+, including: background basin components, wave propagation area components, floating tunnel body components and encrypted area components, generate overlapping area components in Boolean operations, and then create two areas for the geometric components, namely the background area and the overlapping area; then perform meshing, draw the background grid, overlapping grid, wave grid and encrypted grid respectively; select the overlapping grid for subsequent numerical simulation; Then, the previously set grid file is loaded through STAR CCM+ software. First, the physical model is created. The fluid domain volume model is selected for the multiphase flow model. Two new calculation phases, water and air, are created based on the multiphase-Euler term node, and waves are created. Then, the boundary types of each surface are set according to the wave breaking type, and the overlapping grid boundaries are set to the overlap format. Then, the parameters of the suspended tunnel body and anchor chain are set in the DFBI node. Finally, the entire flow field is initialized according to the flow field data determined before the numerical simulation, and the calculation step size is selected for calculation. S103. Based on the volume coupling module in STAR CCM+ software, the connection between the suspended tunnel body and the seabed is established through a tensioned catenary, and then a three-dimensional suspended tunnel numerical model under wave and current combined excitation is established; S2. Based on the established three-dimensional floating tunnel numerical model under wave-current combined excitation, numerical simulation is carried out, and parameter sensitivity analysis is performed on the important nonlinear influencing factors of the floating tunnel. The influence of sensitive parameters on the vibration response characteristics of the floating tunnel body is analyzed to realize the prediction of the three-dimensional motion response of the floating tunnel body under wave-current combined excitation.

2. The method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation according to claim 1 is characterized by: The process of establishing a three-dimensional numerical water pool with wave and current joint excitation based on the boundary wave making method in step 1 includes: Firstly, a stable wave numerical pool is constructed by using the boundary wave generation method; Next, by comparing the wavefront lift heights at different locations with the theoretical values, the computational domain size and mesh profile parameters are determined based on numerical accuracy and computational cost. Finally, the same set of grids is used to establish a uniform incoming flow to construct a three-dimensional numerical water pool with wave-current joint excitation.

3. The method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation according to claim 2 is characterized by: The process of constructing a stable wave numerical pool using the boundary wave generation method includes the following steps: The bottom boundary of the flow field is set as the wall boundary condition, the left and right sides of the flow domain and the two front and rear symmetrical planes are set as velocity inlets, the top of the flow domain is set as the pressure outlet, and a wave-breaking zone is set at the velocity inlet boundary.

4. The method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation according to claim 3 is characterized by: The wave-breaking zone is realized based on a force wave-breaking method.

5. The method for predicting the three-dimensional motion response of a suspended tunnel body under wave-current combined excitation according to claim 3 is characterized by: In the process of using the same set of grids to establish a uniform incoming flow to construct a three-dimensional numerical water pool with wave-current joint excitation, it is also necessary to establish a numerical calculation model of the suspended tunnel under the action of the uniform incoming flow, perform numerical verification, and verify the reliability of the established three-dimensional numerical wave-current water pool.

6. A method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation according to any one of claims 1 to 5, characterized in that: The process of establishing the connection between the floating tunnel body and the seabed through the tensioned catenary includes: A coordinate system Oxz is established, where O is located on the free water surface, Oz is upward and the anchor point of the anchor chain is fixed directly below O. The anchor chain moves in the Oxz plane, G is the upper mooring point of the anchor chain, X and Z are the projection lengths of the overhanging part of the anchor chain in the x and z directions, respectively, and S o is the distance between the anchor chain touchdown point and the anchor point on the seabed; the upper end of the anchor chain is subjected to a tensile force T, and the projections of T in the x and z directions are F h and F v ; Among them, F b is the bottom tension of the catenary, F k is the rigidity coefficient of the catenary, n is the correction factor, v is the vertical tension at the fixed point, v0 is the initial vertical tension at the fixed point, w is the wet weight per unit length of the anchor chain, E is the elastic modulus of the anchor chain, A is the effective cross-sectional area, V0 is the tension at the fixed point of the anchor chain, S T is the total length of the unstretched anchor chain; Based on the above force relationship and combined with the mechanical behavior of the catenary, the overall motion response of the floating body is determined.

7. The method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation according to claim 6 is characterized by: The mechanical behavior of the catenary in determining the overall motion response of the floating body is as follows: In the mooring problem of an ocean floating body, it is first necessary to calculate and determine the initial shape of the anchor chain based on the boundary conditions at the upper end point G of the anchor chain; then, in each time step, the tension of the anchor chain is recalculated according to the change in the position of point G during the movement of the floating platform.

8. A method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation according to any one of claims 1 to 5, characterized in that: The process of numerical simulation based on the established three-dimensional floating tunnel numerical model under wave-current combined excitation described in S2 includes: Based on the three-dimensional numerical water pool, the corresponding wave and current parameters are set, wave and current loads are added, and then the fluid-solid coupling numerical simulation model is run until the vibration response of the suspended tunnel body reaches a stable state; the parameter sensitivity analysis of the important nonlinear influencing factors of the suspended tunnel is carried out using the fluid-solid coupling numerical simulation model.

9. The method for predicting the three-dimensional motion response of a suspended tunnel tube under wave-current combined excitation according to claim 8 is characterized by: The important nonlinear influencing factors of the suspended tunnel include flow velocity, wave parameters, water depth, burial depth, buoyancy-to-weight ratio and mooring angle, and suspended tunnel size.

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