Calculation method and system for wave dissipation effect of salt marsh vegetation with different gradients under variable tide level

Abstract

The invention discloses a method and a system for calculating wave dissipation effects of salt marsh vegetation with different gradients under variable tide levels. The method comprises the following steps: carrying out a physical model test of wave incidence on salt marsh vegetation in a tidal flat area to obtain the energy dissipation amount after waves pass through the vegetation area and the wave reflection amount in the vegetation area; according to the salt marsh vegetation arrangement specification, the energy dissipation amount and the wave reflection amount of the tidal flat area, vegetation energy dissipation is determined. The system comprises an input module, a calculation module, a calibration module, an output module and the like, and is used for recording tide level, height difference gradient and vegetation data, calculating a wave energy attenuation rate and calibrating a calculation model so as to accurately calculate the wave dissipation effect of salt marsh vegetation under different tide level gradients. The calculation method and system provided by the invention have the characteristics of scientificity, practicability, accuracy, high efficiency and the like, and are suitable for the fields of ports, coastal protection engineering, ecological restoration, coastal zone management and the like.

Description

Technical Field

[0001] The invention belongs to the field of coastal engineering and ecological environment protection, and specifically relates to a calculation method and system for wave-breaking effects of salt marsh vegetation with different gradients under changing tide levels. Background Art

[0002] At present, the protection and ecological restoration of tidal flats have become an important issue in coastal areas. Especially in estuaries and coastal zones, tidal changes and wave erosion have had a serious impact on the stability of the coastline and the ecosystem. Although traditional hard structural protection methods, such as seawalls and retaining walls, can effectively resist wave erosion, they often damage the natural ecological environment, lead to a decline in biodiversity, and may cause other environmental problems. Therefore, there is an urgent need for a solution that can protect the coastline while restoring and enhancing the ecosystem.

[0003] As a natural wave-breaking and wave-breaking structure, salt marsh vegetation has a significant wave energy dissipation effect. Salt marsh vegetation interacts with waves through its stem and leaf structure, dissipating wave energy and reducing the impact of waves on the coastline. However, the wave-breaking effect of salt marsh vegetation is greatly affected by changes in tide level and tidal flat gradient. Changes in tide level lead to changes in water depth, which affects the wave propagation path and energy dissipation efficiency; tidal flat gradient affects the attenuation of waves during propagation. Therefore, accurately calculating the wave-breaking effect of salt marsh vegetation under different tide levels and gradient conditions is of great significance for the ecological protection and management of coastal areas.

[0004] In order to better understand and predict the wave-breaking effect of salt marsh vegetation under different tidal and gradient conditions, it is necessary to establish an accurate wave energy attenuation model. The model should comprehensively consider factors such as tidal changes, tidal flat gradients, vegetation types, density and height, and calibrate and verify model parameters through physical model tests and numerical simulations, so as to provide scientific basis and technical support. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method and system for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels, characterized in that it comprises the following steps:

[0008] Physical model tests of wave incidence on salt marsh vegetation in tidal flat areas were conducted to obtain the energy dissipation of waves after passing through the vegetation area and the amount of wave reflection in the vegetation area;

[0009] The energy dissipation of vegetation is determined based on the salt marsh vegetation layout specifications, energy dissipation and wave reflection in the tidal flat area.

[0010] To optimize the above technical solutions, the specific measures taken also include:

[0011] Furthermore, the construction process of the physical model is as follows:

[0012] Select appropriate salt marsh vegetation species in tidal flat areas and classify them according to tide levels;

[0013] The density and height of vegetation are adjusted according to the changes in tide level so that it can dissipate wave energy at different tide levels.

[0014] Furthermore, the classification according to tide level is specifically: the selected vegetation types are classified into low tide beach vegetation, mid tide beach vegetation, high tide beach vegetation and nearshore vegetation according to tide level from low to high.

[0015] Furthermore, the formula for vegetation energy dissipation is as follows:

[0016]

[0017] Where D v represents the energy dissipation of vegetation, is the vegetation stem and leaf correction coefficient, ρ is the fluid density, C d is the drag coefficient, d is the vegetation diameter, H is the wave height, T is the wave period, k is the wave number, h is the water depth, and h v is the vertical position and N is the vegetation density per unit area.

[0018] Furthermore, in the process of determining the vegetation energy dissipation, the tidal level change and the tidal level gradient are considered, and the formula for vegetation energy dissipation is obtained as follows:

[0019]

[0020] Where D v represents the energy dissipation of vegetation, is the vegetation stem and leaf correction coefficient, ρ is the fluid density, C d is the drag coefficient, d is the vegetation diameter, H is the wave height, T is the wave period, k is the wave number; h(t, x) represents the water depth at position x and time t, h0 is the initial tide level, A i is the amplitude of the ith tidal component, ω i is the frequency of the ith tidal component, φ i is the phase angle of the i-th tidal component, n is the number of tidal components, G(x) represents the tidal gradient, h vi and N iare the vertical position corresponding to the i-th tidal component and the vegetation density per unit area, respectively.

[0021] Furthermore, the vegetation diameter d and the vegetation density per unit area N i Determined according to the salt marsh vegetation layout specifications;

[0022] The drag coefficient C d Calibrate according to wave-breaking efficiency: Calculate the simulated wave-breaking efficiency of salt marsh vegetation according to the initial drag coefficient, and determine whether the simulated wave-breaking efficiency of salt marsh vegetation is equal to the actual wave-breaking efficiency; if they are equal, the initial drag coefficient is used as the drag coefficient C d Otherwise, adjust the initial drag coefficient until the simulated wave-breaking efficiency is equal to the actual wave-breaking efficiency, and the adjusted drag coefficient is used as the drag coefficient C d .

[0023] Accordingly, the present invention proposes a calculation system for the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels, which is characterized by comprising:

[0024] An input module is used to input tide level variation data, tidal flat gradient data and salt marsh vegetation arrangement specification data to generate a mathematical model of tide level variation and tidal flat gradient;

[0025] A calculation unit, used to obtain a calculation model of vegetation energy dissipation based on a mathematical model of tide level change and tidal flat gradient and combined with salt marsh vegetation arrangement specification data;

[0026] A calibration module is used to calibrate the calculation model to ensure that the calculation results of the calculation model are consistent with the actual results;

[0027] The output module is used to output the calculation results, including the vegetation energy dissipation of salt marsh vegetation under different tide levels and gradients.

[0028] Furthermore, the mathematical model for generating tide level changes and tidal flat gradients is specifically:

[0029] Record and input the tide level change data h(t) over time t, and generate the tide level change rate

[0030] Record and input the water depth data h(x) at different locations x on the tidal flat to generate the tidal gradient

[0031] The salt marsh vegetation arrangement specification data includes the type, density, height and distribution pattern of the vegetation.

[0032] Furthermore, the calculation model of vegetation energy dissipation is:

[0033]

[0034] Where D v represents the energy dissipation of vegetation, is the vegetation stem and leaf correction coefficient, ρ is the fluid density, C d is the drag coefficient, d is the vegetation diameter, H is the wave height, T is the wave period, k is the wave number; h(t, x) represents the water depth at position x and time t, h0 is the initial tide level, A i is the amplitude of the ith tidal component, ω i is the frequency of the ith tidal component, φ i is the phase angle of the i-th tidal component, n is the number of tidal components, G(x) represents the tidal gradient, h vi and N i are the vertical position corresponding to the i-th tidal component and the vegetation density per unit area, respectively.

[0035] Furthermore, the calibration module conducts a physical model test of wave incidence on salt marsh vegetation in the tidal flat area to obtain the energy dissipation of waves after passing through the vegetation area and the wave reflection in the vegetation area, and based on the results of the physical model test, calculates the vegetation diameter d and the vegetation density N per unit area in the model. i and the drag coefficient C d Perform calibration.

[0036] The beneficial effects of the present invention are as follows: the present invention calculates the water depth at different times and locations by establishing a mathematical model of tidal changes and tidal flat gradients, combined with the physical characteristics of vegetation, and then calculates the energy dissipation effect of salt marsh vegetation under different tidal and gradient conditions. Such a design can calculate the wave-breaking effect of salt marsh vegetation under different tidal gradients while simultaneously considering tidal changes, tidal flat gradients, and the wave-breaking efficiency of salt marsh vegetation, thereby improving the calculation accuracy. The present invention can not only accurately predict the wave-breaking effect of vegetation, but also provide effective technical support for the protection and restoration of coastal ecosystems. The proposed calculation method and system are scientific, practical, accurate, and efficient, and are suitable for ports, coastal protection projects, ecological restoration, coastal zone management, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a flowchart of a method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels.

[0038] Figure 2 It is an architectural diagram of a system for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels.

[0039] Figure 3 This is a schematic diagram of the physical model of salt marsh vegetation.

[0040] Figure 4 It is a schematic diagram of tidal changes, gradients and vegetation arrangements. DETAILED DESCRIPTION

[0041] The present invention will now be described in further detail with reference to the accompanying drawings.

[0042] Embodiment 1

[0043] like Figure 1 As shown, this embodiment proposes a method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels, and its technical concept is as follows: for the arrangement of salt marsh vegetation with different tide levels and gradients, considering the influence of tide level changes and tidal flat gradients on the wave-breaking effect, the energy dissipation under different vegetation types and densities is determined respectively as the basic parameter for calculating the wave-breaking effect; based on the wave-breaking characteristics of vegetation, different vegetation types are numerically generalized and parameterized to determine the parameterized scheme of vegetation wave breaking; combining tide level changes, tidal flat gradients and the parameterized scheme of vegetation wave breaking, taking the wave energy dissipation formula as the calculation carrier, a method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels is constructed.

[0044] The calculation method specifically includes the following steps:

[0045] S1: Considering the tidal changes and tidal flat gradients, combined with the arrangement of salt marsh vegetation at different tidal levels and gradients, determine the energy dissipation under different vegetation types and densities; vegetation arrangement specifications include vegetation type, density, height and distribution pattern.

[0046] (1) Vegetation selection: Select appropriate salt marsh vegetation types in the tidal flat area. According to the tidal level, they can be classified into low tidal flat vegetation, mid-tidal flat vegetation, high tidal flat vegetation and nearshore vegetation. For example, low tidal flat vegetation: submerged vegetation, such as Scirpus maritimus. Mid-tidal flat vegetation: salt-tolerant vegetation, such as Suaeda salsa and Tamarix chinensis. High tidal flat vegetation: emergent vegetation, such as Phragmites australis. Nearshore vegetation: such as mangroves (Rhizophora stylosa) and coastal pines (Casuarina equisetifolia).

[0047] (2) Adjusting density and height: The density and height of vegetation are adjusted according to the changes in tide level so that it can effectively dissipate wave energy at different tide levels. The specific methods include: first, collecting tide level change data through a tide level monitoring system and establishing a tide level change model; then, according to the tide level change model, determining the optimal density and height combination of vegetation at different tide levels. The method of adjusting vegetation density includes planting vegetation of different densities in the laboratory or on-site, and evaluating its wave-breaking effect through wave tank experiments or on-site monitoring to determine the optimal density. The method of adjusting vegetation height includes selecting vegetation varieties of different heights to adapt to different tide conditions, and verifying its wave-breaking effect through experiments or monitoring.

[0048] (3) Simulate the wave-breaking process of vegetation: Determine the energy dissipation and wave-breaking effect of vegetation through physical model tests. Place the physical model of salt marsh vegetation in a water tank, and then collect the designed waves, which include wave height, wave period, and wave incident direction. Artificial waves are generated according to the designed waves to carry out physical model tests of wave incident to determine the amount of energy dissipation after the waves pass through the salt marsh vegetation area and the amount of wave reflection in the salt marsh vegetation area. Specifically, a vegetation model with selected and adjusted density height is arranged in the water tank, wave conditions with different wave heights and periods are set, and the wave breaking change data before and after the waves pass through the vegetation area are recorded by a wave height meter.

[0049] S2: Considering the wave-breaking effect of salt marsh vegetation, determine the calculation formula for the wave energy attenuation rate caused by salt marsh vegetation in the wave energy dissipation model. Under certain numerical constraints (such as vegetation height, density, and layout spacing), according to the layout specifications of salt marsh vegetation in the tidal flat area, the energy dissipation is determined by the energy dissipation and wave reflection.

[0050] Considering the influence of the arrangement density of salt marsh vegetation and tidal changes on wave energy dissipation, the energy dissipation under different vegetation types and densities is determined. Among them, the higher the vegetation density, the greater the energy dissipation. The value of energy dissipation is based on the principle of conservation of wave energy to ensure the rationality of energy dissipation. The reasonable value of energy dissipation can be determined through comprehensive analysis based on the results of physical model tests and combined with the vegetation arrangement in the tidal flat area, and the determined energy dissipation can be used as the basic parameter for calculating the wave dissipation effect.

[0051] The process of determining the parameterized scheme for wave breaking by salt marsh vegetation in this embodiment includes: based on the wave breaking characteristics of salt marsh vegetation, numerically generalizing and parameterizing the wave breaking efficiency of vegetation, and determining the parameterized scheme for wave breaking by vegetation. The attenuation of wave energy caused by vegetation can be obtained by calculating the work done by vegetation on the resistance of the fluid. The principle is similar to the traditional wave breaking process. In view of this, the attenuation of wave energy caused by vegetation can be obtained by calculating the work done by vegetation on the resistance of the fluid. When using this method, it is assumed that the resistance of vegetation to the fluid plays a dominant role, and the influence of inertial force is ignored. The specific calculation process is as follows:

[0052] ①The density of wave energy is the sum of potential energy density and kinetic energy density, and the formula is:

[0053]

[0054] Among them, ρ is the fluid density, g is the acceleration due to gravity, and H is the wave height.

[0055] ② The speed at which wave energy is transferred during propagation is equal to the group velocity c g , the calculation formula is:

[0056] c g =n·c

[0057] Where c is the speed of a single wave and n is usually expressed as:

[0058]

[0059] ③The expression of wave number k is:

[0060]

[0061] Where L is the wavelength, and the expression for wavelength is:

[0062]

[0063] ④ There is a negative term in energy dissipation, represented by -D, which is:

[0064]

[0065] Where x is the length of the wave passing through the vegetation area.

[0066] ⑤ The dissipation of wave energy by vegetation is expressed as D v express:

[0067]

[0068] ⑥The total energy dissipation formula is:

[0069]

[0070] Vegetation stem and leaf correction factor It is determined by measuring the ratio of the volume of vegetation with stems and leaves to the volume of vegetation without stems and leaves.

[0071] ⑦Horizontal orbital velocity of the wave U orb The formula for (z) changing with depth is:

[0072]

[0073] U orb is the amplitude of the horizontal orbital velocity; ω = 2π / T is the angular frequency, where T is the period of the wave; a = H / 2 is the amplitude of the wave, and H is the wave height.

[0074] ⑧The final energy dissipation formula is:

[0075]

[0076] Where D v represents the energy dissipation of vegetation, is the vegetation stem and leaf correction coefficient, ρ is the fluid density, C d is the drag coefficient, d is the vegetation diameter, H is the wave height, T is the wave period, k is the wave number, h is the water depth, and h v is the vertical position and N is the vegetation density per unit area.

[0077] Under the influence of tidal gradient, the wave energy attenuation rate caused by salt marsh vegetation can be obtained by transforming the above formula in the wave direction. The specific calculation process is as follows:

[0078] ① Tidal level change rate G(t)

[0079] The tidal level change rate G(t) can be understood as the rate of change of the tidal level relative to time, which is a key parameter in the study of tides and waves. In order to express the tidal level change rate G(t), it can be defined as the derivative of the tidal level h(t) with time, that is:

[0080]

[0081] ② Tidal gradient G(x)

[0082] Tidal gradient refers to the change in water depth (tidal level) at different locations on a tidal flat, which can be described by the relationship between water depth and horizontal distance. For example, a reference point (such as the high tide line or low tide line) is set, and the horizontal distance from the reference point to the specified location is x, and the water depth is h(x). The tidal gradient can be expressed as the rate of change of water depth relative to horizontal distance, that is:

[0083]

[0084] In order to reflect the influence of tidal level change rate and gradient in the formula, time and water depth can be combined to obtain the change of tidal level with time and horizontal distance through experimental or observational data. It is possible to consider combining the tidal level change rate G(t) with the gradient G(x) at the horizontal position x to form a comprehensive tidal level change model.

[0085] Assume that the tidal level change can be expressed as a function h(t, x), that is, the tidal level that changes with time and position. The tidal level change rate G and the horizontal gradient can be expressed as:

[0086]

[0087] Astronomical tides can be approximated as a sine wave model, describing the periodic changes of tide levels over time. This model is often used for simple tidal analysis and prediction, using a comprehensive model to represent the changes in water depth over time and location:

[0088]

[0089] Where h0 is the initial tide level, A i is the amplitude of the ith tidal component, ω i is the frequency of the ith tidal component, φ i is the phase angle of the i-th tidal component, and n represents the number of tidal components.

[0090] ③The influence of tide level on energy dissipation formula

[0091] In order to reflect the influence of tidal changes in the energy dissipation formula, the time factor can be considered when calculating the water depth h, making the energy dissipation formula more accurate. The specific formula is as follows:

[0092]

[0093] Figure 4 The changes in tide level over time and the changes in water depth at different locations on the tidal flat are shown, the tide level change rate G(t) and tide level gradient G(x) are generated, and the layout of different salt marsh vegetation is shown.

[0094] In the above formula, only the vegetation drag coefficient, vegetation diameter and number of vegetation per square meter are unknown. Therefore, this embodiment provides a specific determination method: in the wave energy attenuation rate calculation formula, the vegetation diameter d and the number of vegetation per square meter N can be set with reference to the salt marsh vegetation specifications (i.e., the type, number, size, layout position and spacing of the vegetation), and the vegetation drag coefficient C dIt needs to be calibrated according to the wave-breaking efficiency. Referring to the existing physical model test research results of the wave-breaking efficiency of salt marsh vegetation, different specifications and arrangements of vegetation lead to certain differences in its wave-breaking efficiency, and the wave height attenuation percentage caused by vegetation is between 85% and 95%. First, collect the types, quantities, sizes, layout locations and spacing of salt marsh vegetation in the tidal flat area to be studied, and refer to the existing physical model test research results of the wave-breaking efficiency of salt marsh vegetation to determine the wave-breaking efficiency of vegetation. Then, combined with the wave-breaking efficiency of vegetation, use the selected wave calculation model to conduct a sensitivity analysis on the relationship between wave energy attenuation and vegetation drag coefficient, and determine the vegetation drag coefficient C. d The reasonable value of is selected, and on this basis, the parameterization scheme of salt marsh vegetation wave breaking is determined.

[0095] Specifically, the method for determining the vegetation drag coefficient, the vegetation diameter and the number of vegetation per square meter includes:

[0096] (1) The vegetation diameter d and the number of vegetation per square meter N are determined according to the salt marsh vegetation specifications in the plane layout of the tidal flat area. The vegetation specifications include the type, quantity, size, layout location and spacing of the vegetation.

[0097] Specifically, the size of the salt marsh vegetation was taken as the vegetation diameter, and the density of the salt marsh vegetation was taken as the number of vegetation per square meter.

[0098] (2) Establish a physical model of salt marsh vegetation based on vegetation specifications, and Figure 3 A physical model test of wave incidence was conducted to determine the actual wave-breaking efficiency of vegetation.

[0099] The vegetation specifications are scaled down in proportion, a physical model of the salt marsh vegetation is constructed, the physical model of the salt marsh vegetation is placed in a water tank, and then artificial waves are created according to the designed waves to determine the actual wave-breaking efficiency of the salt marsh vegetation.

[0100] (3) Determine the initial vegetation drag coefficient: input the wave energy attenuation rate calculation formula containing the initial vegetation drag coefficient into the wave calculation model to obtain the first calculation model, and use the first calculation model to calculate the simulated wave breaking efficiency of the salt marsh vegetation; determine whether the simulated wave breaking efficiency is equal to the actual wave breaking efficiency; if so, use the initial vegetation drag coefficient as the vegetation drag coefficient; if not, adjust the initial vegetation drag coefficient to obtain the adjusted value, and use the adjusted value as the initial vegetation drag coefficient for the next cycle, and return to the step of "inputting the wave energy attenuation rate calculation formula containing the initial vegetation drag coefficient into the wave calculation model".

[0101] It should be noted that in the wave energy attenuation rate calculation formula containing the initial vegetation drag coefficient, the vegetation diameter and the number of vegetation per square meter are the vegetation diameter and the number of vegetation per square meter determined according to the salt marsh vegetation specifications in the tidal flat area.

[0102] Next, the method proposed in this embodiment is explained in conjunction with a specific application case.

[0103] The experiment was conducted in a tidal flat area with the goal of calculating the energy dissipation of a salt marsh vegetation at different tide levels and tidal flat gradients. The vegetation type selected was reed (Phragmites australis) and its relevant parameters were as follows:

[0104] Vegetation diameter d = 0.01 m; vegetation density N = 200 plants / m2; drag coefficient C d =1.0; fluid density ρ = 1000 kg / m3; wave height H = 0.5 m; wave period T = 8 s; vertical position h v = 0.5 m; tidal flat length L = 100 m; height difference H tide =2 meters.

[0105] In addition, calculate the tidal level change rate G(x), and let the fluctuation period of the tidal level change with time be T tide , the fluctuation amplitude is A. The following parameters are provided: initial tide level h0 = 1.0 m; tide level change amplitude A = 0.5 m; fluctuation period T tide =12 hours.

[0106] The change of tide level over time can be expressed as:

[0107]

[0108] The tidal level change rate G(t) is:

[0109]

[0110] The tidal flat gradient G(x) is:

[0111]

[0112] Assume that at a specific time point t = 3 hours, the tide level h(t) and the tide level change rate G(t) are:

[0113]

[0114] Substitute the tide level h = 1.5 meters and the tidal flat gradient G (x) = 0.02 into the formula to calculate:

[0115] The wave number k is calculated as follows:

[0116]

[0117] Calculate the wavelength λ:

[0118]

[0119] Calculate the wave number k:

[0120]

[0121] Then, vegetation energy dissipation D v have:

[0122]

[0123] Therefore, under the above given conditions, the energy dissipation of reed vegetation is approximately 1.54.

[0124] The calculation in the above embodiment shows how to calculate the energy dissipation of salt marsh vegetation at different tidal levels according to the changes in tidal level and gradient. This method provides a scientific basis for studying and applying the wave-breaking effect of salt marsh vegetation.

[0125] Embodiment 2

[0126] like Figure 2 As shown, this embodiment proposes a calculation system for the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels, which corresponds to the calculation method proposed in the first embodiment. The system mainly includes the following modules:

[0127] (1) Input module

[0128] The input module is used to input tide level change data, tidal flat gradient data and salt marsh vegetation specification data to generate a mathematical model of tide level change and tidal flat gradient. Specifically, the input module includes the following parts:

[0129] Tidal level change input unit: records and inputs the tidal level change data h(t) over time, and generates the tidal level change rate

[0130] Tidal flat gradient input unit: records and inputs water depth (tidal level) data h(x) at different locations on the tidal flat to generate tidal level gradient

[0131] Vegetation specification input unit: record and input the type, density, height and distribution pattern of salt marsh vegetation to generate the layout specifications of salt marsh vegetation.

[0132] (2) Computation module

[0133] The calculation module is used to calculate the wave energy attenuation rate based on the tide level change and tidal flat gradient model, combined with the vegetation drag coefficient, vegetation diameter and the number of vegetation per square meter. Specifically, the calculation module includes the following parts:

[0134] Tidal change calculation unit: calculates the tidal change rate G(t) and tidal gradient G(x).

[0135] Wave energy attenuation calculation unit: based on input data and formulas Calculate the wave energy attenuation rate D v .

[0136] (3) Calibration module

[0137] The calibration module is used to calibrate the calculation model according to the test results of the physical model to ensure that the calculation results are consistent with the actual situation. Specifically, the calibration module includes the following parts:

[0138] Physical model test unit: Through physical model tests, wave energy attenuation data and reflection data under different vegetation arrangements are obtained.

[0139] Data calibration unit: Based on the results of physical model tests, the drag coefficient C in the calculation model is d , vegetation diameter d and the number of vegetation per square meter N are calibrated to ensure the accuracy of the calculation results.

[0140] (4) Output module

[0141] The output module is used to output the calculation results, including the wave energy attenuation effect of salt marsh vegetation under different tide levels and gradients. Specifically, the output module includes the following parts:

[0142] Result display unit: Displays the wave energy attenuation effect under different tide levels and gradients in the form of graphs.

[0143] Data export unit: Export the calculation results as reports for users to make further analysis and decision.

[0144] (5) Database module

[0145] The database module is used to store and manage input data, calculation results and calibration data to ensure the continuity of the system and the traceability of data. Specifically, the database module includes the following parts:

[0146] Data storage unit: stores tide level change data, tidal flat gradient data, salt marsh vegetation specification data and physical model test data.

[0147] Data management unit: Classify and manage stored data to ensure data integrity and availability.

[0148] In this system, the functions, principles and workflows of each module and unit are the same as the calculation method proposed in the first embodiment, so the repeated contents will not be repeated here.

[0149] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels, characterized in that: The steps include: Physical model tests of wave incidence on salt marsh vegetation in tidal flat areas were conducted to obtain the energy dissipation of waves after passing through the vegetation area and the amount of wave reflection in the vegetation area; The energy dissipation of vegetation is determined based on the salt marsh vegetation layout specifications, energy dissipation and wave reflection in the tidal flat area.

2. The method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 1, characterized in that: The construction process of the physical model is as follows: Select appropriate salt marsh vegetation species in tidal flat areas and classify them according to tide levels; The density and height of vegetation are adjusted according to the changes in tide level so that it can dissipate wave energy at different tide levels.

3. The method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 2, characterized in that: The classification according to tide level is specifically: the selected vegetation types are divided into low tide beach vegetation, mid tide beach vegetation, high tide beach vegetation and nearshore vegetation according to the tide level from low to high.

4. The method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 1, characterized in that: The formula for vegetation energy dissipation is as follows: Where D v represents the energy dissipation of vegetation, is the vegetation stem and leaf correction coefficient, ρ is the fluid density, C d is the drag coefficient, d is the vegetation diameter, H is the wave height, T is the wave period, k is the wave number, h is the water depth, and h v is the vertical position and N is the vegetation density per unit area.

5. The method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 1, characterized in that: In the process of determining the vegetation energy dissipation, the tidal level change and the tidal level gradient are considered, and the formula for vegetation energy dissipation is obtained as follows: Where D v represents the energy dissipation of vegetation, is the vegetation stem and leaf correction coefficient, ρ is the fluid density, C d is the drag coefficient, d is the vegetation diameter, H is the wave height, T is the wave period, k is the wave number; h(t, x) represents the water depth at position x and time t, h0 is the initial tide level, A i is the amplitude of the ith tidal component, ω i is the frequency of the ith tidal component, φ i is the phase angle of the i-th tidal component, n is the number of tidal components, G(x) represents the tidal gradient, h vi and N i are the vertical position corresponding to the i-th tidal component and the vegetation density per unit area, respectively.

6. The method for calculating the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 5, characterized in that: The vegetation diameter d and the vegetation density per unit area N i Determined according to the salt marsh vegetation layout specifications; The drag coefficient C d Calibrate according to wave-breaking efficiency: Calculate the simulated wave-breaking efficiency of salt marsh vegetation according to the initial drag coefficient, and determine whether the simulated wave-breaking efficiency of salt marsh vegetation is equal to the actual wave-breaking efficiency; if they are equal, the initial drag coefficient is used as the drag coefficient C d Otherwise, adjust the initial drag coefficient until the simulated wave-breaking efficiency is equal to the actual wave-breaking efficiency, and the adjusted drag coefficient is used as the drag coefficient C d .

7. A calculation system for the wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels, characterized in that: include: An input module is used to input tide level variation data, tidal flat gradient data and salt marsh vegetation arrangement specification data to generate a mathematical model of tide level variation and tidal flat gradient; A calculation unit, used to obtain a calculation model of vegetation energy dissipation based on a mathematical model of tide level change and tidal flat gradient and combined with salt marsh vegetation arrangement specification data; A calibration module is used to calibrate the calculation model to ensure that the calculation results of the calculation model are consistent with the actual results; The output module is used to output the calculation results, including the vegetation energy dissipation of salt marsh vegetation under different tide levels and gradients.

8. A calculation system for wave-breaking effect of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 7, characterized in that: The mathematical model for generating tide level changes and tidal flat gradients is specifically: Record and input the tide level change data h(t) over time t, and generate the tide level change rate Record and input the water depth data h(x) at different locations x on the tidal flat to generate the tidal gradient The salt marsh vegetation arrangement specification data includes the type, density, height and distribution pattern of the vegetation.

9. A calculation system for wave-breaking effects of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 7, characterized in that: The calculation model of vegetation energy dissipation is: Where D v represents the energy dissipation of vegetation, is the vegetation stem and leaf correction coefficient, ρ is the fluid density, C d is the drag coefficient, d is the vegetation diameter, H is the wave height, T is the wave period, k is the wave number; h(t, x) represents the water depth at position x and time t, h0 is the initial tide level, A i is the amplitude of the ith tidal component, ω i is the frequency of the i-th tidal component, φi is the phase angle of the i-th tidal component, n is the number of tidal components, G(x) represents the tidal gradient, h vi and N i are the vertical position corresponding to the i-th tidal component and the vegetation density per unit area, respectively.

10. A calculation system for wave-breaking effects of salt marsh vegetation with different gradients under changing tide levels as claimed in claim 9, characterized in that: The calibration module conducts a physical model test of wave incidence on salt marsh vegetation in the tidal flat area to obtain the energy dissipation of waves after passing through the vegetation area and the wave reflection in the vegetation area. Based on the results of the physical model test, the vegetation diameter d and the vegetation density per unit area N in the calculation model are calculated. i and the drag coefficient C d Perform calibration.

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