A numerical simulation method of wave hydrodynamics in sea areas with breakwaters

Abstract

The present invention discloses a wave hydrodynamic numerical simulation method for a sea area with a breakwater, which relates to the technical field of offshore wave simulation, and includes the following steps: S1: determining the target sea area, and collecting the nautical chart data and water depth topography data of the target sea area; S2: determining the shoreline position of the target sea area, and establishing a water depth topography database of the target sea area; S3: setting the grid accuracy, and constructing a wave hydrodynamic two-dimensional model of the target sea area; S4: setting the boundary conditions for driving the wave hydrodynamic two-dimensional model, and setting the initial parameters; S5: based on the wave hydrodynamic two-dimensional model constructed in S3, the sub-grid method is used to perform numerical simulation on the target sea area, and the characteristic wave height and period data of the target sea area are obtained. The method of the present invention can ensure the calculation efficiency, and takes into account the wave transmission characteristics of the permeable oyster reef, and can accurately simulate the influence of the construction of the permeable oyster reef on the wave hydrodynamic environment field.

Description

Technical Field

[0001] The invention relates to the technical field of offshore wave simulation, and in particular to a wave hydrodynamic numerical simulation method for a sea area where a breakwater is set. Background Art

[0002] Traditional hard protective measures, such as seawalls, breakwaters and groins, have historically been used as a conventional approach to mitigate coastal hazards. However, the potential negative impacts of building traditional hard structures near the coastline are increasingly being considered in coastal management. Such hard structures can have a negative impact on coastal ecosystems and natural features such as beaches; moreover, unlike many nature-based solutions, most of these hard structures are non-adaptive and therefore cannot respond to environmental changes, such as sea level rise.

[0003] Biological shorelines based on hollow oyster reef breakwaters (oysters naturally gather and attach to older shells, rocks or underwater surfaces to form rocky oyster reef structures) have gradually developed as a sustainable method for protecting coastlines because they can suppress waves and reduce flow speeds, thereby stabilizing and increasing sedimentation, thereby reducing shoreline erosion; and artificial breakwaters built with oyster shells promote the settlement of oyster larvae, especially in areas with low-energy wave climates and abundant oyster populations.

[0004] Before constructing a permeable oyster reef breakwater, a wave hydrodynamic model is needed to simulate the changes in the wave field before and after the construction of the project, in order to evaluate the environmental impact of the breakwater construction and optimize the design. However, the current numerical simulation of wave hydrodynamics for breakwaters mostly adopts the method of changing the local water depth and roughness, and the grid of the submerged breakwater area needs to be encrypted to a very small size, which requires a large amount of calculation and is heavily dependent on computing resources. In addition, the calculation formulas based on the existing simulation methods are mostly for smooth non-permeable submerged breakwaters or riprap breakwaters composed of blocks of specific sizes. However, permeable oyster reef breakwaters have geometric complexity, porous permeability, sharp edges, and different material properties.

[0005] Therefore, how to consider the wave transmission characteristics of the permeable oyster reef breakwater, accurately simulate the impact of engineering construction on the wave hydrodynamic environment field, and improve the calculation efficiency is a technical problem that needs to be solved urgently.

[0006] In view of this, this invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings existing in the prior art, and to propose a wave hydrodynamic numerical simulation method for a sea area with a breakwater, which can ensure the calculation efficiency, take into account the wave transmission characteristics of the oyster reef breakwater, and can accurately simulate the impact of engineering construction on the wave hydrodynamic environment field.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for numerically simulating wave hydrodynamics in a sea area where a breakwater is set, wherein the breakwater is a permeable oyster reef breakwater, and the method comprises the following steps:

[0010] S1: Determine the target sea area and collect the nautical chart information and water depth and topographic data of the target sea area, where the target sea area refers to the sea area where the breakwater is planned to be arranged;

[0011] S2: Determine the shoreline position of the target sea area and establish a water depth topography database of the target sea area;

[0012] S3: Set the grid accuracy and use the structured grid to build a two-dimensional wave hydrodynamic model of the target sea area. When the interaction between the breakwater and the waves needs to be calculated, the following wave propagation equation is used for calculation:

[0013] ,

[0014] In the formula, K t is the transmission coefficient, R c is the freeboard of the submerged breakwater, H moi is the incident effective wave height, B is the width of the embankment top, and ξ is the equivalent wave steepness coefficient;

[0015] S4: Set the boundary conditions for driving the wave hydrodynamic two-dimensional model and set the initial parameters;

[0016] S5: Based on the two-dimensional wave hydrodynamic model constructed in S3, the sub-grid method is used to perform numerical simulation of the target sea area to obtain the characteristic wave height and period data of the target sea area.

[0017] Furthermore, in S2, the shoreline position of the target sea area is determined based on the nautical chart data.

[0018] Furthermore, the wave hydrodynamic two-dimensional model in S3 is a wave hydrodynamic two-dimensional model of the target sea area where the breakwater is set up, which is constructed based on the spectral density equation.

[0019] Furthermore, a two-dimensional wave hydrodynamic model of the target sea area with a permeable breakwater is constructed based on the spectral density equation. The spectral density equation used is as follows:

[0020] ,

[0021] In the formula, N is the action density parameter, c x and c y are the propagation velocities in the x and y directions, c σ and c θare the propagation velocities in the spatial directions σ and θ respectively, S is the source term, and t is the time.

[0022] Furthermore, the calculation formula of ξ in S3 is as follows:

[0023] ,

[0024] In the formula, α is the slope of the submerged dike, L 0p The wavelength is deep water.

[0025] Further, R C / H moi The value range is as follows: -4.3 <R C / H moi <0; B / H moi The value range is as follows: B / H moi >10.

[0026] Furthermore, in S4, wave data under normal sea conditions and extreme sea conditions in the target sea area are collected to drive the boundary conditions of the wave hydrodynamic two-dimensional model.

[0027] Furthermore, the boundary conditions driving the wave hydrodynamic two-dimensional model include: the tide and wave conditions of normal sea conditions in the target sea area, and the tide and wave conditions during extreme weather periods.

[0028] Furthermore, in S3, the initial parameters include: the roughness of the target sea area, the calculation time step, and the wave breaking index.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. In the constructed two-dimensional wave hydrodynamic model, the wave propagation equation is improved to calculate the interaction between the permeable oyster reef breakwater and the waves, which makes up for the shortcomings of the traditional model in simulating by changing the local water depth and roughness, and solves the limitations of the traditional model in ignoring the geometric complexity, porous permeability, sharp edges and different material properties of the permeable oyster reef breakwater. It can more realistically and accurately reflect the wave propagation, deformation and dissipation process around the permeable oyster reef breakwater.

[0031] 2. Due to the improvement of the wave propagation equation, the sub-grid method can be used to perform numerical simulation of the target sea area, avoiding the high-resolution requirements of the traditional model for the grid. Simulation can be performed on a medium-scale grid, saving computing resources and thus ensuring computing efficiency.

[0032] 3. Taking into account the actual impact of the open oyster reef breakwater, under medium-scale grid conditions, it can quickly and accurately simulate the spatial and temporal distribution of key characteristics of the wave field such as wave height and period under different dynamic conditions, and can more realistically and accurately reflect the wave propagation, deformation and dissipation process around the breakwater, and thus more accurately evaluate the wave propagation impact of the breakwater on the surrounding sea area, providing more reliable prediction and decision-making support for the design of the breakwater and environmental impact assessment.

[0033] 4. It has broad application prospects in the fields of marine engineering, coastal protection, and ecological environment protection. By providing reliable technical support for engineering design, construction, and maintenance, the solution of the present invention helps to improve the wave-breaking performance of the permeable oyster reef breakwater, reduce coastal erosion, protect the ecological environment, and contribute to the sustainable development of coastal areas. Matlab can be used to process and plot the calculation results, visualize the wave hydrodynamic environment field of the permeable oyster reef breakwater, and provide reliable technical support for engineering design, construction, and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of a numerical simulation method of wave hydrodynamics in a sea area with a permeable oyster reef breakwater;

[0035] Figure 2 The bathymetric topographic map of the target sea area for simulation;

[0036] Figure 3 K is the K calculated by the method of the present invention. t Comparison of the values ​​with the measured values;

[0037] Figure 4 : is a comparison diagram of the simulation results of the method of the present invention and the traditional method, wherein a is the comparison diagram of model A, b is the comparison diagram of Model B, and c is the comparison diagram of Model C. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0039] Embodiment 1:

[0040] A method for numerically simulating wave hydrodynamics in a sea area where a breakwater is set, wherein the breakwater is a permeable oyster reef breakwater, and the method comprises the following steps:

[0041] S1: Determine the target sea area and collect the nautical chart information and water depth and topographic data of the target sea area, where the target sea area refers to the sea area where the breakwater is planned to be arranged;

[0042] S2: Determine the shoreline position of the target sea area and establish a water depth topography database of the target sea area;

[0043] In this embodiment, according to the nautical chart data, Surfer is used to digitize the nautical chart, obtain the nautical chart water depth data of the target sea area, and unify them to the same reference surface to establish a water depth topographic database of the target sea area.

[0044] S3: Set the grid accuracy and use the structured grid to build a two-dimensional wave hydrodynamic model of the target sea area. When the interaction between the breakwater and the waves needs to be calculated, the following wave propagation equation is used for calculation:

[0045] ,

[0046] In the formula, K t is the transmission coefficient, R c is the freeboard of the submerged breakwater, H moi is the incident effective wave height, B is the width of the embankment top, and ξ is the equivalent wave steepness coefficient;

[0047] S4: Set the boundary conditions for driving the wave hydrodynamic two-dimensional model and set the initial parameters;

[0048] S5: Based on the two-dimensional wave hydrodynamic model constructed in S3, the sub-grid method is used to perform numerical simulation of the target sea area to obtain the characteristic wave height and period data of the target sea area.

[0049] In an optional embodiment, in S2, the shoreline position of the target sea area is determined based on nautical chart data.

[0050] In an optional embodiment, the wave hydrodynamic two-dimensional model in S3 is a wave hydrodynamic two-dimensional model of the target sea area where the breakwater is set up, which is constructed based on a spectral density equation.

[0051] In an optional embodiment, a two-dimensional wave hydrodynamic model of a target sea area with a permeable breakwater is constructed based on a spectral density equation, and the spectral density equation used is as follows:

[0052] ,

[0053] In the formula, N is the action density parameter, c x and c y are the propagation velocities in the x and y directions, c σ and c θ are the propagation velocities in the spatial directions σ and θ respectively, S is the source term, and t is the time.

[0054] In an optional embodiment, the calculation formula of ξ in S3 is as follows:

[0055] ,

[0056] In the formula, α is the slope of the submerged dike, L 0p The wavelength is deep water.

[0057] In an alternative embodiment, R C / H moi The value range is as follows: -4.3 <R C / H moi <0; B / H moi The value range is as follows: B / H moi >10.

[0058] In an optional embodiment, in S4, wave data under normal sea conditions and extreme sea conditions in the target sea area are collected to drive the boundary conditions of the wave hydrodynamic two-dimensional model.

[0059] In an optional embodiment, the boundary conditions driving the wave hydrodynamic two-dimensional model include: the tide level and wave conditions of normal sea conditions in the target sea area, and the tide level and wave conditions during extreme weather periods.

[0060] In an optional embodiment, in S3, the initial parameters include: the roughness of the target sea area, the calculation time step, and the wave breaking index.

[0061] The present embodiment provides a method for numerically simulating wave hydrodynamics in a sea area with a breakwater. In the constructed two-dimensional wave hydrodynamic model, the wave propagation equation is improved to calculate the interaction between the permeable oyster reef breakwater and the waves, which makes up for the deficiency of the traditional model in simulating by changing the local water depth and roughness, and solves the limitation of the traditional model in ignoring the geometric complexity, porous permeability, sharp edges and different material properties of the permeable oyster reef breakwater. The method can more realistically and accurately reflect the wave propagation, deformation and dissipation process around the permeable oyster reef breakwater.

[0062] The present embodiment provides a method for numerically simulating wave hydrodynamics in a sea area with a breakwater. Due to the improved wave propagation equation, a sub-grid method can be used to perform numerical simulation on the target sea area, thus avoiding the high-resolution requirements of traditional models on grids. The method can be simulated on medium-scale grids, saving computing resources and thus ensuring computing efficiency.

[0063] In summary, the wave hydrodynamic numerical simulation method for a sea area with a breakwater in this embodiment can quickly and accurately simulate the temporal and spatial distribution of key characteristics of the wave field such as wave height and period under different dynamic conditions, and can more realistically and accurately reflect the propagation, deformation and dissipation process of waves around the breakwater, thereby more accurately evaluating the wave propagation effect of the breakwater on the surrounding sea area, and providing more reliable prediction and decision support for the design of the breakwater and environmental impact assessment.

[0064] On this basis, the wave hydrodynamic numerical simulation method for a sea area with a breakwater in this embodiment has broad application prospects in the fields of marine engineering, coastal protection, and ecological environmental protection; by providing reliable technical support for engineering design, construction, and maintenance, the wave hydrodynamic numerical simulation method for a sea area with a permeable oyster reef in this embodiment helps to improve the wave-breaking performance of oyster reef submerged breakwaters, reduce coastal erosion, protect the ecological environment, and contribute to the sustainable development of coastal areas. Matlab can be used to process and plot the calculation results, visualize the wave hydrodynamic environmental field of the permeable oyster reef submerged breakwater, and provide reliable technical support for engineering design, construction, and maintenance.

[0065] In order to verify the effectiveness of the wave hydrodynamic numerical simulation method for setting a breakwater in this embodiment, a target sea area for setting a permeable oyster reef breakwater was set up, and its water depth and topography are as follows: Figure 2 As shown, for the convenience of demonstration, six observation points O1-O6 are selected before and after the breakwater, O3 and O4 are the verification points corresponding to the actual measurement of the physical model test, O1 and O2 as well as O5 and O6 are the numerical simulation expansion points for illustrating the law, different initial input wave heights are set, and the scheme of this embodiment is used for simulation calculation. The transmission coefficient K of the simulated calculation is t (the ratio of the transmitted wave height to the incident wave height. In this embodiment, the wave height measured at the back of the wave is equivalent to the transmitted wave height, and the wave height measured at the front of the wave is equivalent to the incident wave height) and the measured projection coefficient K t For example Figure 3 As shown, the determination coefficient R 2 It is 0.98, which shows that the scheme implemented in this paper can accurately simulate the interaction between waves and the transparent oyster reef submerged breakwater.

[0066] In addition, Figure 2 Based on the water depth topography map, this embodiment also simulates and compares the effectiveness of different schemes. The input conditions and model settings of the compared models are shown in Table 1, where Model A is a direct simulation, that is, a structure with the same volume as the simulated hollow oyster reef breakwater is set at the corresponding position, Model B is a traditional model, and Model C is the scheme of this embodiment. The simulated wave height and transmission coefficient K t As shown in Table 2, the simulation results are Figure 4 shown.

[0067] Table 1 Model input conditions and model settings

[0068]

[0069] Table 2 Simulation results

[0070]

[0071] It can be seen from the data in Table 2 that the direct simulation method of high-precision simulation by changing the local water depth leads to an abnormal increase in the effective wave height behind the breakwater, and the transmission coefficients of O2 / O1, O4 / O3, and O6 / O5 are abnormally greater than 1, which is not in line with the actual law. The solution of this embodiment uses medium-precision simulation to obtain results that are closer to the physical model test, and because waves can enter through the edge of the breakwater, the transmission coefficients of O2 / O1 and O6 / O5 are larger than O4 / O3, which is in line with the objective actual law. Compared with the traditional model, the effective wave height attenuation is more significant and the transmission coefficient is smaller, which can reflect the geometric complexity, porous permeability, sharp edge, etc. of the breakwater. Enhanced effect on wave attenuation.

[0072] In addition, from Figure 4 It can be seen that the direct simulation method of performing high-precision simulation by changing the local water depth cannot effectively simulate the protective effect of the breakwater; using the traditional model for sub-grid simulation, whether it is located on the wave-facing side or the wave-back side of the breakwater, cannot effectively consider the enhanced effect of the breakwater on wave attenuation; the solution of this embodiment can provide more reliable prediction results of effective wave height and transmission coefficient.

[0073] In addition, the simulation calculation time required for Model A, B, and C is shown in Table 3.

[0074] Table 3 Simulation calculation time

[0075]

[0076] According to the data in Table 3, Model C of the embodiment has an advantage in simulation calculation time, which is of great significance for improving the wave-breaking performance of the permeable oyster reef breakwater, optimizing the design of engineering structures, reducing coastal erosion, and protecting the ecological environment, and can contribute to the sustainable development of coastal areas.

[0077] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for numerical simulation of wave hydrodynamics in a sea area with a breakwater, characterized in that: The breakwater is a permeable oyster reef breakwater, and the method comprises the following steps: S1: Determine the target sea area and collect the nautical chart information and water depth and topographic data of the target sea area, where the target sea area refers to the sea area where the breakwater is planned to be arranged; S2: Determine the shoreline position of the target sea area and establish a water depth topography database of the target sea area; S3: Set the grid accuracy and use the structured grid to build a two-dimensional wave hydrodynamic model of the target sea area. When the interaction between the breakwater and the waves needs to be calculated, the following wave propagation equation is used for calculation: ， In the formula, K t is the transmission coefficient, R c is the freeboard of the submerged breakwater, H moi is the incident effective wave height, B is the width of the embankment top, and ξ is the equivalent wave steepness coefficient; S4: Set the boundary conditions for driving the wave hydrodynamic two-dimensional model and set the initial parameters; S5: Based on the two-dimensional wave hydrodynamic model constructed in S3, the sub-grid method is used to perform numerical simulation of the target sea area to obtain the characteristic wave height and period data of the target sea area.

2. A wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 1, characterized in that: In S2, the shoreline position of the target sea area is determined based on the nautical chart data.

3. The wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 1, characterized in that: The wave hydrodynamic two-dimensional model in S3 is a wave hydrodynamic two-dimensional model of the target sea area for setting up breakwaters, which is constructed based on the spectral density equation.

4. A wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 3, characterized in that: The two-dimensional wave hydrodynamic model of the target sea area with a permeable breakwater is constructed based on the spectral density equation. The spectral density equation used is as follows: ， In the formula, N is the action density parameter, c x and c y are the propagation velocities in the x and y directions, c σ and c θ are the propagation velocities in the spatial directions σ and θ respectively, S is the source term, and t is the time.

5. The wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 1, characterized in that: The calculation formula of ξ in S3 is as follows: ， In the formula, α is the slope of the submerged dike, L 0p The wavelength is deep water.

6. A wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 5, characterized in that: R C / H moi The value range is as follows: -4.3 <R C / H moi <0; B / H moi The value range is as follows: B / H moi >10.

7. The wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 1, characterized in that: In S4, wave data under normal sea conditions and extreme sea conditions in the target sea area are collected to drive the boundary conditions of the wave hydrodynamic two-dimensional model.

8. The wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 5, characterized in that: The boundary conditions driving the two-dimensional wave hydrodynamic model include: the tidal and wave conditions of normal sea conditions in the target sea area, as well as the tidal and wave conditions during extreme weather periods.

9. The wave hydrodynamic numerical simulation method for a sea area with a breakwater according to claim 1, characterized in that: In S3, the initial parameters include: the roughness of the target sea area, the calculation time step, and the wave breaking index.

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