An offshore island cluster hydrodynamic characteristic simulation method based on multi-model coupling

Abstract

The application discloses a kind of offshore island group hydrodynamic characteristic simulation method based on multi-model coupling, comprising the following steps: first, using SWAN model to simulate wave field, coupling simulation of wave simulation result in Delft3D model with tidal current, sediment. Select key area, use XBeach model to accurately simulate coastline and seabed topography evolution, realize the data nesting, exchange and coupling between multi-model, ensure the consistency of simulation result. The application can more accurately simulate the hydrodynamic and sediment transport process of the sea area around offshore island group, guide engineering practice.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ocean engineering, in particular to a water dynamic characteristic simulation method for offshore island groups based on multi-model coupling. BACKGROUND

[0002] The traffic infrastructure of offshore island groups is affected by complex water dynamics, and there is currently a lack of effective wave-flow-sand multi-scale model coupling methods, and there is also a lack of simulation research coupled with structures. And existing coupling research is mostly limited to nearshore, which cannot adapt to the complex marine environment of offshore islands, so it is difficult to accurately simulate the complex water dynamic phenomena of offshore island groups and surrounding sea areas. SUMMARY

[0003] The purpose of the present application is to solve the problem of the traffic infrastructure of offshore island groups being affected by the water environment and being difficult to simulate in the prior art, and to provide a water dynamic characteristic simulation method for offshore island groups based on multi-model coupling.

[0004] The technical solution adopted to achieve the purpose of the present application is:

[0005] A water dynamic characteristic simulation method for offshore island groups based on multi-model coupling, comprising the following steps:

[0006] Comprising the following steps:

[0007] Step 1, obtain coastline data, and process to obtain an ASCII Grid terrain file;

[0008] Step 2, based on the coastline data of step 1, obtain the part below the horizontal plane, i.e. water depth data, as the bottom boundary condition;

[0009] Step 3, obtain nearshore wave data, sediment data and tidal data;

[0010] Step 4, construct a SWAN model, input the bottom boundary condition obtained in step 2, and input the nearshore wave data obtained in step 3 as input boundary conditions, to obtain wave simulation data;

[0011] Step 5, construct a Delft3D model, import the ASCII Grid terrain file obtained in step 1, and input the tidal data obtained in step 3 as boundary conditions, run the water flow module in the Delft3D model, and output water flow simulation data;

[0012] Step 6, use the SWAN interface of the Delft3D model to couple the SWAN model of step 4 and the water flow module in the Delft3D model of step 5;

[0013] Step 7, enable the sediment transport module in the Delft3D model, define the physical parameters of the sediment according to the sediment data obtained in step 3, improve the original transport equation of the sediment transport module, input the physical parameters into the improved transport equation, and output the sediment deposition under different space-time conditions, i.e. the topographic evolution, to obtain the wave-current-sediment coupling model;

[0014] Step 8, according to the geographical position and hydrodynamic characteristics of the island, determine the key area that needs to be finely simulated;

[0015] Step 9, construct the X-Beach model for the key area in step 8, import the bottom boundary conditions obtained in step 2, import the output of the flow module in the Delft3D model in step 5 as the boundary conditions, enable the shoreline evolution module, input the improved transport equation in step 7, and establish a higher resolution coastline and seabed topographic evolution model;

[0016] Step 10, use the ESMF Earth System Model Component Standard Framework to integrate and nest the SWAN model, the X-Beach model and the Delft3D model;

[0017] Step 11, run the integrated and nested model obtained in step 10 to obtain the hydrodynamic simulation results of the sea area around the island.

[0018] In the above technical solution, the offshore island group hydrodynamic characteristic simulation method further comprises step 12, parameter calibration: performing a small-scale physical model test and analyzing the simulation results of step 11.

[0019] In the above technical solution, in step 1, high-resolution high-definition image maps are obtained using Google earth pro software, and vector boundaries drawn from Google earth pro are processed using Arcmap to finally output ASCII Grid terrain files.

[0020] In the above technical solution, in step 3, nearshore wave data, sediment data and tidal data are obtained from the National Marine Scientific Data Center or Chinatide.

[0021] In the above technical solution, in step 4, the construction of the SWAN model specifically includes the following steps:

[0022] Step 4.1, determine the grid division of the study area;

[0023] Step 4.2, substitute the bottom boundary conditions obtained in step 2;

[0024] Step 4.3, substitute the nearshore wave data obtained in step 3 as the input boundary conditions;

[0025] Step 4.4: Determine the output file format and output parameters. The output file can have a custom suffix or use the general ASCII format. Specifically, use the FRAME command to define the grid size of the output file, and use the BLOCK command to define the output file name, output time step, total output time, and output wave parameters. The output wave parameters include wave height.

[0026] Step 4.5, integrating the steps 4.1 to 4.4 into a .inp control file;

[0027] Step 4.6: Input the .inp control file obtained in step 4.5 into the SWAN model, run the SWAN model, and output the wave simulation data;

[0028] Step 4.7: Verify the wave simulation data in step 4.6 with the measured data.

[0029] In the above technical solution, in step 5, the construction of the water flow module in the Delft3D model specifically includes the following steps:

[0030] Step 5.1: Using the GEBCO gridded bathymetric dataset as input, create sampling points using ArcMap, and then use the Spatial Analyst tool to analyze the .xyz bathymetric scatter file.

[0031] Step 5.2: Determine the simulation area, import the ASCII grid terrain file obtained in step 1, use the grid function in the Delft3D model to draw the grid and refine the grid in the key study area, and then import the .xyz water depth scatter file obtained in step 5.1;

[0032] Step 5.3: Determine the model boundary and use the tidal data obtained in step 3 as boundary conditions;

[0033] Step 5.4, determine the simulation time and step size;

[0034] Step 5.5, use the NS equation as a solver;

[0035] Step 5.6: Run the water flow module in the Delft3D model to output the water flow simulation data;

[0036] Step 5.7: Verify the water flow simulation data obtained in step 5.6 with the measured data.

[0037] In the above technical solution, in step 7, the improved original transport equation of the sediment transport module is:

[0038]

[0039] Where ρ is the fluid density, d50 is the median particle size of sediment, ρ s is the sediment density, τ' cr is the measured shear stress, θ' cr，s is the dimensionless threshold shear stress, is the critical friction speed, Re d50 is the particle Reynolds number, ν is the kinematic viscosity of the fluid, ρ bulk is the overall density of the sediment, Fines is the dimensionless fine particle content, g is the acceleration of gravity, Re is the k Permeability Reynolds number, η′ cr is the threshold erosion rate of sediment, and k is the permeability.

[0040] In the above technical solution, in step 7, the method for constructing the sediment transport model specifically includes the following steps:

[0041] Step 7.1, enable the sediment transport module in the Delft3D model;

[0042] Step 7.2, defining the physical parameters of sediment based on the sediment data obtained in step 3;

[0043] In step 7.3, the original transport equation of the sediment transport module is improved, and the physical parameters obtained in step 7.2 are used as inputs of the improved transport equation:

[0044] Step 7.4: Run the sediment transport module in Delft3D to output the sediment deposition under different temporal and spatial conditions.

[0045] In step 7.5, the sediment deposition under different temporal and spatial conditions obtained in step 7.4 is verified by combining the measured data to obtain a wave-current-sediment coupling model.

[0046] In the above technical solution, the construction of the X-Beach model in step 9 specifically includes the following steps:

[0047] Step 9.1, import the bottom boundary conditions obtained in step 2;

[0048] In step 9.2, import the output of the water flow module in the Delft3D model in step 5.6 as boundary conditions;

[0049] Step 9.3, draw a fine grid;

[0050] Step 9.4, enable the shoreline evolution module and rewrite the original sediment transport equation into the improved transport equation in step 7.3;

[0051] Step 9.5, set deposition and erosion conditions;

[0052] In step 9.6, run X-Beach to build a higher-resolution model of the coastline and seabed topography evolution.

[0053] In the above technical solution, in step 10, the integrated nesting method specifically includes the following steps:

[0054] Step 10.1: The outer large area coarse grid is simulated using the SWAN model from step 4 to provide wave boundary conditions;

[0055] Step 10.2: Use the wave-current-sediment coupling model obtained in step 7 on the medium-resolution grid in the mid-layer near-island waters during the island shrinkage process to simulate the wave-current-sediment transport;

[0056] Step 10.3: The inner nearshore fine grid uses the XBeach model from step 9 to simulate the coastline and terrain changes;

[0057] In step 10.4, the new terrain simulated by the XBeach model is used as the bottom boundary condition of the Delft3D model. The Delft3D model recalculates the wave-flow-sediment field based on the updated bottom conditions, achieving bidirectional interactive coupling.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention can more accurately simulate the hydrodynamics and sediment transport processes in the sea areas surrounding offshore islands, establish a temporal and spatial distribution dataset of the hydrological environment of typical offshore islands, and contribute to the formation of a technical guide for the assessment of the hydrodynamic environment of offshore islands and guide engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is the velocity field in the wave-current coupling results. DETAILED DESCRIPTION

[0061] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0062] A method for simulating the hydrodynamic characteristics of offshore islands based on multi-model coupling includes the following steps:

[0063] Step 1: Get shoreline data:

[0064] Use Google Earth Pro software to obtain high-resolution HD imagery, use Arcmap to process the vector boundaries drawn from Google Earth Pro, and finally output ASCII Grid terrain files;

[0065] Step 2: Based on the shoreline data in step 1, obtain the water depth data below the horizontal plane as the bottom boundary condition;

[0066] Step 3: Collection of hydrological environment data:

[0067] Obtain nearshore wave data, sediment data, and tide data from channels such as the National Marine Science Data Center and Chinatide;

[0068] Step 4: Build the SWAN model:

[0069] Step 4.1, determine the grid division of the study area;

[0070] Step 4.2, substitute the bottom boundary conditions obtained in step 2;

[0071] Step 4.3: Substitute the nearshore wave data obtained in step 3 as input boundary conditions;

[0072] Step 4.4: Determine the output file format and output parameters. The output file can have a custom suffix or use the general ASCII format. Specifically, use the FRAME command to define the grid size of the output file, and use the BLOCK command to define the output file name, output time step, total output time, and output wave parameters. The output wave parameters include wave height.

[0073] Step 4.5, integrating the steps 4.1 to 4.4 into a .inp control file;

[0074] Step 4.6: Input the .inp control file obtained in step 4.5 into SWAN, run SWAN, and output the wave simulation data;

[0075] Step 4.7, verify the wave simulation data in step 4.6 with the measured data;

[0076] Step 5: Build the Delft3D model:

[0077] Step 5.1: Using the GEBCO gridded bathymetric dataset as input, create sampling points using ArcMap, and then use the Spatial Analyst tool to analyze the .xyz bathymetric scatter file.

[0078] Step 5.2: Determine the simulation area, import the ASCII grid terrain file obtained in step 1, use the grid function of DELFT3D to draw the grid and refine the grid in the key study area, and then import the .xyz water depth scatter file obtained in step 5.1;

[0079] Step 5.3: Determine the model boundary and use the tidal data obtained in step 3 as boundary conditions;

[0080] Step 5.4, determine the simulation time and step size;

[0081] Step 5.5, use the NS equation as a solver;

[0082] Step 5.6: Run the water flow module in the Delft3D model to output the water flow simulation data;

[0083] Step 5.7, verifying the water flow simulation data obtained in step 5.6 with the measured data;

[0084] Step 6, wave-current coupling: Use the SWAN interface of the Delft3D model to couple the SWAN model in step 4 with the water flow module in the Delft3D model in step 5. The velocity field in the coupling result is as follows: Figure 1 As shown;

[0085] Step 7: Build a sediment transport model:

[0086] Step 7.1, enable the sediment transport module in the Delft3D model;

[0087] Step 7.2: Define the physical parameters of the sediment based on the sediment data obtained in step 3 and substitute them into the following step 7.3;

[0088] Step 7.3: Improve the original transport equation of the sediment transport module:

[0089]

[0090] Where ρ is the fluid density, d 50 is the median particle size of sediment, ρ s is the sediment density, τ' cr is the measured shear stress, θ' cr，s is the dimensionless threshold shear stress, is the critical friction speed, Re d50 is the particle Reynolds number, ν is the kinematic viscosity of the fluid, ρ bulk is the overall density of the sediment, Fines is the dimensionless fine particle content, g is the acceleration of gravity, Re is the k Permeability Reynolds number, η′ cr is the threshold erosion rate of sediment, and k is the permeability.

[0091] The model's inherent sediment transport equations are mostly applicable to riverbanks and estuaries, but are not suitable for sediment transport along offshore island coasts, where the hydrodynamic environment is more complex. The improved original sediment transport equation for the sediment module is specifically designed for the deep soft soil environment of offshore islands, using permeability as a starting point.

[0092] Step 7.4: Run the sediment transport module in the Delft3D model to output the sediment deposition under different temporal and spatial conditions.

[0093] In step 7.5, the sediment deposition under different temporal and spatial conditions obtained in step 7.4 is verified by combining the measured data to obtain a wave-current-sediment coupling model.

[0094] Step 8, select key areas: Determine the key areas that require detailed simulation based on the geographical location and hydrodynamic characteristics of the island;

[0095] Step 9: Build the X-Beach model for the key areas selected in step 8:

[0096] Step 9.1, import the bottom boundary conditions obtained in step 2;

[0097] In step 9.2, import the output of the water flow module in the Delft3D model in step 5.6 as boundary conditions;

[0098] Step 9.3, draw a fine grid;

[0099] Step 9.4: Enable the shoreline evolution module and rewrite the original sediment transport equation into the improved sediment module original transport equation in step 7.3;

[0100] Step 9.5, set deposition and erosion conditions;

[0101] Step 9.6, run the X-Beach model to build a higher-resolution model of coastline and seabed topography evolution;

[0102] Step 10: Use the ESMF Earth System Model Component Standard Framework to integrate and nest the SWAN model, X-Beach model, and Delft3D model:

[0103] Step 10.1: The outer large area coarse grid is simulated using the SWAN model from step 4 to provide wave boundary conditions;

[0104] Step 10.2: Use the wave-current-sediment coupling model obtained in step 7 on the medium-resolution grid in the mid-layer near-island waters during the island shrinkage process to simulate wave-current-sediment transport;

[0105] Step 10.3: The inner nearshore fine grid uses the XBeach model from step 9 to simulate the coastline and terrain changes;

[0106] In step 10.4, the new terrain simulated by the XBeach model is used as the bottom boundary condition of the Delft3D model. The Delft3D model recalculates the wave-flow-sediment field based on the updated bottom conditions, achieving bidirectional interactive coupling.

[0107] Step 11, simulation operation: Run the integrated nested model obtained in step 10 to obtain the hydrodynamic simulation results of the sea area around the island;

[0108] Step 12, parameter calibration: conduct a small-scale physical model test and analyze the simulation results of step 11 to verify their accuracy and reliability;

[0109] Step 13, Application Practice: Apply the simulation results to island disaster prevention planning and coastal engineering design.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for simulating the hydrodynamic characteristics of offshore islands based on multi-model coupling, characterized in that: The following steps are involved: Step 1: Obtain shoreline data and process it to obtain an ASCII Grid terrain file; Step 2: Based on the shoreline data in step 1, obtain the water depth data below the horizontal plane as the bottom boundary condition; Step 3: Obtain near-coast wave data, sediment data, and tide data; Step 4: Construct the SWAN model, substitute the bottom boundary conditions obtained in step 2 and the nearshore wave data obtained in step 3 as input boundary conditions to obtain wave simulation data; Step 5: Build the Delft3D model, import the ASCII grid terrain file obtained in step 1, connect the tidal data obtained in step 3 as boundary conditions, run the water flow module in the Delft3D model, and output the water flow simulation data; Step 6: Use the SWAN interface of the Delft3D model to couple the SWAN model in step 4 with the water flow module in the Delft3D model in step 5 using a wave-current model. Step 7: Activate the sediment transport module in the Delft3D model, define the physical parameters of the sediment based on the sediment data obtained in step 3, improve the original transport equation of the sediment transport module, input the physical parameters into the improved transport equation, output the sediment deposition under different temporal and spatial conditions, and obtain the wave-current-sediment coupling model; In step 7, the improved transport equation is: Where ρ is the fluid density, d 50 is the median particle size of sediment, ρ s is the sediment density, τ' cr is the measured shear stress, θ' cr，s is the dimensionless threshold shear stress, is the critical friction speed, Re d50 is the particle Reynolds number, ν is the kinematic viscosity of the fluid, ρ bulk is the overall density of the sediment, Fines is the dimensionless fine particle content, g is the acceleration of gravity, Re is the k Permeability Reynolds number, η′ cr is the threshold erosion rate of sediment, k is the permeability; In step 7, the operation method of the sediment transport module specifically includes the following steps: Step 7.1, enable the sediment transport module in the Delft3D model; Step 7.2, defining the physical parameters of sediment based on the sediment data obtained in step 3; In step 7.3, the original transport equation of the sediment transport module is improved, and the physical parameters obtained in step 7.2 are used as inputs of the improved transport equation: Step 7.4: Run the sediment transport module in Delft3D to output the sediment deposition under different temporal and spatial conditions. Step 7.5: Verify the sediment deposition under different temporal and spatial conditions obtained in step 7.4 by combining the measured data to obtain the wave-current-sediment coupling model; Step 8: Determine the key areas that require detailed simulation based on the geographical location and hydrodynamic characteristics of the island; Step 9: Build an X-Beach model for the key areas in Step 8. Import the bottom boundary conditions obtained in Step 2. Import the output of the water flow module in the Delft3D model in Step 5 as boundary conditions. Enable the shoreline evolution module and input the improved transport equations from Step 7 to build a higher-resolution coastline and seabed topography evolution model. The construction of the X-Beach model in step 9 specifically includes the following steps: Step 9.1, import the bottom boundary conditions obtained in step 2; In step 9.2, import the output of the water flow module in the Delft3D model in step 5.6 as boundary conditions; Step 9.3, draw a fine grid; Step 9.4, enable the shoreline evolution module and rewrite the original sediment transport equation into the improved transport equation in step 7.3; Step 9.5, set deposition and erosion conditions; Step 9.6, run X-Beach to build a higher-resolution model of coastline and seabed topography evolution; Step 10: Use the ESMF Earth System Model Component Standard Framework to integrate and nest the SWAN model, X-Beach model, and Delft3D model; In step 10, the integrated nesting method specifically includes the following steps: Step 10.1: The outer large area coarse grid is simulated using the SWAN model from step 4 to provide wave boundary conditions; Step 10.2: Use the wave-current-sediment coupling model obtained in step 7 on the medium-resolution grid in the mid-layer near-island waters during the island shrinkage process to simulate wave-current-sediment transport; Step 10.3: The inner nearshore fine grid uses the XBeach model from step 9 to simulate the coastline and terrain changes; In step 10.4, the new terrain simulated by the XBeach model is used as the bottom boundary condition of the Delft3D model. The Delft3D model recalculates the wave-flow-sediment field based on the updated bottom conditions, achieving bidirectional interactive coupling. Step 11: Run the integrated nested model obtained in step 10 to obtain the hydrodynamic simulation results of the sea area around the island.

2. The method for simulating the hydrodynamic characteristics of offshore islands according to claim 1, wherein: The method further includes step 12, parameter calibration: conducting a small-scale physical model test and analyzing the simulation results of step 11.

3. The method for simulating hydrodynamic characteristics of offshore islands according to claim 1, wherein: In the step 1, Google Earth Pro software is used to obtain a high-resolution high-definition image map, and Arcmap is used to process the vector boundaries drawn from Google Earth Pro, and finally an ASCII Grid terrain file is output.

4. The method for simulating hydrodynamic characteristics of offshore islands according to claim 1, wherein: In step 3, near-shore wave data, sediment data, and tide data are obtained from the National Marine Science Data Center or Chinatide.

5. The method for simulating hydrodynamic characteristics of offshore islands according to claim 1, wherein: In step 4, the construction of the SWAN model specifically includes the following steps: Step 4.1, determine the grid division of the study area; Step 4.2, substitute the bottom boundary conditions obtained in step 2; In step 4.3, substitute the nearshore wave data obtained in step 3 as the input boundary conditions; Step 4.4: Determine the output file format and output parameters. The output file can have a custom suffix or use the general ASCII format. Specifically, use the FRAME command to define the grid size of the output file, and use the BLOCK command to define the output file name, output time step, total output time, and output wave parameters. The output wave parameters include wave height. Step 4.5, integrating the steps 4.1 to 4.4 into a .inp control file; Step 4.6: Input the .inp control file obtained in step 4.5 into the SWAN model, run the SWAN model, and output the wave simulation data; Step 4.7: Verify the wave simulation data in step 4.6 with the measured data.

6. The method for simulating hydrodynamic characteristics of offshore islands according to claim 1, wherein: In step 5, the construction of the water flow module in the Delft3D model includes the following steps: Step 5.1: Using the GEBCO gridded bathymetric dataset as input, create sampling points using ArcMap, and then use the Spatial Analyst tool to analyze the .xyz bathymetric scatter file. Step 5.2: Determine the simulation area, import the ASCII grid terrain file obtained in step 1, use the grid function in the Delft3D model to draw the grid and refine the grid in the key study area, and then import the .xyz water depth scatter file obtained in step 5.1; Step 5.3: Determine the model boundary and use the tidal data obtained in step 3 as boundary conditions; Step 5.4, determine the simulation time and step size; Step 5.5, use the NS equation as a solver; Step 5.6: Run the water flow module in the Delft3D model to output the water flow simulation data; Step 5.7: Verify the water flow simulation data obtained in step 5.6 with the measured data.

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