A quantitative method for predicting the impact of large offshore floating structures on shoreline evolution

Abstract

The present invention discloses a quantitative method for predicting the impact of large offshore floating structures on shoreline evolution, aiming to provide a more accurate and efficient method for predicting the trend of shoreline evolution, so as to improve the problem in the existing beach evolution prediction model that the wave action of large offshore floating structure projects cannot be considered. The present invention is based on the dynamic spectrum balance equation. By setting multiple sections of closed breakwaters, the waves in different wave directions after the implementation of large offshore floating structure projects are simulated to determine the wave boundary conditions of the shoreline evolution model; the spatially continuously distributed wave elements are used as the open boundary of the shoreline evolution model. According to the wave classification and direction statistics data, the annual-scale wave action time and the longshore sediment transport volume are quantitatively calculated, so as to predict the impact trend of large offshore floating structure projects on beach evolution at the annual scale.

Description

Technical Field

[0001] The present invention relates to the technical field of evolution prediction, and more specifically, to a quantitative method for predicting the impact of large offshore floating structures on shoreline evolution. Background Art

[0002] Sandy beaches undertake important ecological service functions such as water purification, buffering between land and sea, and climate regulation, and play an irreplaceable role in maintaining the global ecological balance; currently, the construction of large offshore floating structure projects around sandy shorelines has become a trend for future development, and the medium- and long-term evolution of sandy coasts is mainly controlled by wave dynamics.

[0003] However, due to the large footprint of large offshore floating structures, they have an impact on the diffraction and transmission of most incoming waves, thereby changing the nearshore wave energy distribution, affecting the longshore sediment transport process in the project sea area, and having a certain impact on the beach evolution trend in the project sea area. However, the existing beach evolution prediction models cannot consider the impact of large offshore project site selection and wave dissipation by structures, thereby reducing the fidelity of the prediction models. Summary of the Invention

[0004] The present invention provides a quantitative method for predicting the impact of large offshore floating structures on shoreline evolution to solve the problem that the existing beach evolution prediction models cannot consider the impact of large offshore project site selection and wave dissipation by structures.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A quantitative method for predicting the impact of large offshore floating structures on shoreline evolution, comprising the following steps: S1, determining the wave boundary conditions; S2, generalizing important wave condition parameters; S3, determining the open boundary of the model; S4, determining the simulation time; S5, simulating the prediction results.

[0007] Preferably, the S1 specifically includes: using the dynamic spectrum balance equation, combining with wind field data to obtain a large-scale wave field in the past 10 years, simulating the waves in different wave directions after the implementation of the large offshore floating structure project by setting multiple sections of closed transmission breakwaters, and statistically analyzing the wave results to obtain the classified and directional wave data in deep water in the project sea area in the past 10 years, and determining the wave boundary conditions of the shoreline evolution model based on this.

[0008] Preferably, the project sea area includes the area outside the breaking zone and within the offshore project area.

[0009] Preferably, the transmission coefficient of the transmission breakwater is related to the geometric shape of the large floating structure and can be determined by physical experiments or numerical experiments in a water tank.

[0010] Preferably, the step S2 specifically includes: selecting the root mean square value of wave heights at all levels as the representative wave height H 1 / 10 The calculation formula of which is H 1 / 10 = m, where X and Y respectively represent the minimum wave height and the maximum wave height of this level of waves.

[0011] Preferably, the step S2 specifically includes: calculating the significant wave height and the action time, where the significant wave height H s =H 1 / 10 / 1.27; the action time (h) = frequency × 365 × 24 h / day.

[0012] Preferably, the wave direction of the waves refers to the angle between the main traveling direction of the waves and the true north direction of the earth. The action frequency of waves in each direction is obtained from the statistical data of the waves measured throughout the year in the research area, indicating the number of days when waves of this level act in a year.

[0013] Preferably, the step S3 specifically includes: assuming that the waves and the wave-generated longshore current are the most important driving forces for sediment transport in the bay, the selection (construction method) of wave parameters is the same as that of the one-line model, and the spatially continuous distributed wave elements are used as the open boundary of the model.

[0014] Preferably, in the beach evolution model, the spatially continuous distributed wave elements are used as the open boundary of the model, specifically including: given wave condition parameters at each grid node of the open boundary of the beach evolution model, including significant wave height, average period, and wave direction angle.

[0015] Preferably, the specific wave condition parameter values along the open boundary can be obtained from the calculation of wind-generated waves simulated based on the dynamic spectrum balance equation.

[0016] Preferably, the step S4 specifically includes: the simulation time is obtained by converting according to the frequency of waves at all levels, indicating the number of days when waves of this level act in a year.

[0017] Preferably, the step S5 specifically includes: when the simulation time is 1 year, according to the annual measured wave rose diagram, the waves in the normal wave direction and the strong wave direction of the engineering sea area are successively applied at the model boundary; when the simulation time is greater than one year, then starting from the second year, the wave conditions of the first year are repeated every year.

[0018] Preferably, the step S5 specifically includes: using the beach evolution model to conduct long-term large-scale floating structure simulation calculations, and according to the wave classification and direction statistical data, quantitatively calculating the action time of waves at all levels on an annual scale and the longshore sediment transport volume, and obtaining the prediction results of the influence of the large-scale floating structure on the beach evolution trend.

[0019] The principle and beneficial effects of this technical solution:

[0020] (1) The calculation method in the present invention can be based on the dynamic spectrum balance equation. By setting multiple sections of closed transmission breakwaters, it can simulate the waves in different wave directions after the implementation of an offshore large floating structure project, so as to determine the wave boundary conditions of the beach evolution model, realizing the regional division of waves in different wave directions and defining the boundary conditions of waves at different levels.

[0021] (2) The present invention takes the spatially continuously distributed wave elements as the open boundary of the beach evolution model. According to the wave classification and direction statistics data, it quantitatively calculates the action time of waves at each level on an annual scale and the longshore sediment transport volume, so as to predict the influence trend of the offshore large floating structure project on the beach evolution on an annual scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the step flow chart of the present invention;

[0023] Figure 2 is the representative wave height of waves at each level and its corresponding simulation time in the numerical simulation; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present invention will be further described in detail below in conjunction with the drawings and embodiments:

[0025] Example:

[0026] As Figure 2 shown, taking Hongtang Bay in Sanya City, Hainan Province as an example: The wave height of 1.5 m in the ESE direction acts for 445 hours; the wave height of 2.1 m at point A11 in the ESE direction acts for 397 hours; the wave height of 3 m at point A11 in the SW direction acts for 28.5 hours; the wave height of 4 m at point A11 in the ESE direction acts for 5.18 hours; the wave height of 3 m at point A11 in the WSW direction acts for 8.6 hours; the wave height of 4 m at point A11 in the WSW direction acts for 2.6 hours.

[0027] As Figure 1 shown, the present invention provides a quantitative method for predicting the influence of a large offshore floating structure on beach evolution, including the following steps: S1. Determine the wave boundary conditions; S2. Generalize important wave condition parameters; S3. Determine the open boundary of the model; S4. Determine the simulation time; S5. Simulate the prediction results.

[0028] As Figure 1 shown, S1 specifically includes: Using the dynamic spectrum balance equation and combining wind field data to obtain a large-scale wave field in the past 10 years. By setting multiple sections of closed transmission breakwaters, it simulates the waves in different wave directions after the implementation of the offshore large floating structure project, and statistically obtains the classified and directional wave data of deep water in the project sea area in the past 10 years, and determines the wave boundary conditions of the beach evolution model based on this.

[0029] As Figure 1As shown in the figure, the engineering sea area includes the area outside the breaker zone and within the offshore engineering area.

[0030] As Figure 1 shown in the figure, the transmission coefficient of the permeable breakwater is related to the geometric shape of the large floating structure, and can be determined by physical tests or numerical tests in a water tank.

[0031] As Figure 1 shown in the figure, S2 specifically includes: selecting the root mean square value of wave heights at each level as the representative wave height, and the calculation formula is H 1 / 10 = m, where X and Y represent the minimum wave height and the maximum wave height of this level of waves respectively.

[0032] As Figure 1 shown in the figure, S2 specifically includes: calculating the significant wave height and the action time, where the significant wave height is taken as H s =H 1 / 10 / 1.27 according to the "Hydrological Specifications for Ports and Waterways"; the action time (h) = frequency × 365 × 24 h / day.

[0033] As Figure 1 shown in the figure, the wave direction refers to the angle between the main traveling direction of the wave and the true north direction of the earth. The wave action frequency in each direction is obtained from the statistical analysis of the wave data measured throughout the year in the study area, representing the number of days when waves of this level act in a year.

[0034] As Figure 1 shown in the figure, S3 specifically includes: assuming that waves and wave-generated longshore currents are the main driving forces for sediment transport in the bay, the selection of wave parameters (construction method) is the same as that of the one-line model, and the spatially continuous wave elements are used as the open boundary of the model.

[0035] As Figure 1 shown in the figure, in the beach evolution model, the spatially continuous wave elements are used as the open boundary of the model, specifically including: giving wave condition parameters at each grid node of the open boundary of the beach evolution model, including significant wave height, average period, and wave direction angle.

[0036] As Figure 1 shown in the figure, the specific wave condition parameter values along the open boundary can be obtained from the calculation of wind-generated waves simulated based on the dynamic spectrum balance equation.

[0037] As Figure 1 shown in the figure, S4 specifically includes: the simulation time is obtained by converting according to the frequency of waves at each level, representing the number of days when waves of this level act in a year.

[0038] As Figure 1As shown, S5 specifically includes: when the simulation time is 1 year, waves in the ESE-W direction are applied successively at the model boundary; when the simulation time is more than one year, the wave conditions of the first year are repeated every year starting from the second year.

[0039] As Figure 1 shown, S5 specifically includes: using a beach evolution model to conduct long-term simulation calculations of large floating structures, quantitatively calculating the action time of waves at each level on an annual scale and the sediment transport volume along the coast according to the wave classification and direction statistics data, and obtaining the prediction results of the trend of beach evolution by the large floating structure.

[0040] The above are only embodiments of the present invention, and common general technical solutions and / or characteristics in the solutions are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, and these should also be regarded as the protection scope of the present invention, which will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application shall be subject to the content of its claims, and the specific implementation manners in the specification and the like can be used to interpret the content of the claims.

Claims

1. A quantitative method for predicting the impact of large offshore floating structures on shoreline evolution, characterized in that, It includes the following steps: S1. Determine the wave boundary conditions; S2. Generalize important wave condition parameters; S3. Determine the open boundary of the model; S4. Determine the simulation time; S5. Simulate the prediction results; Specifically, S1 includes: using the dynamic spectral balance equation, combining with wind field data to obtain the large-scale wave field in the past 10 years, simulating the waves in different wave directions after the implementation of the offshore large floating structure project by setting multiple sections of closed transmission breakwaters, statistically analyzing the wave results to obtain the hierarchical and directional wave data of deep water in the project sea area in the past 10 years, and determining the wave boundary conditions of the beach evolution model based on this; The specific content of S2 includes: selecting the root mean square value of wave heights at each level as the representative wave height, and the representative wave height H 1 / 10 is calculated by the formula H 1 / 10 = m, where X and Y represent the minimum wave height and the maximum wave height of waves at each level respectively; The said S2 specifically includes: calculating the significant wave height and the action time, where the significant wave height H s =H 1 / 10 / 1.27; the action time (h) = frequency × 365 × 24 h / day; Specifically, S3 includes: assuming that waves and wave-generated longshore currents are the main driving forces for sediment transport in the bay, the selection of wave parameters is the same as that of the one-line model, and the spatially continuous wave elements are used as the open boundary of the model; Specifically, S4 includes: the simulation time is obtained by converting according to the frequency of each level of waves, representing the number of days of the action of each level of waves in a year; Specifically, S5 includes: when the simulation time is 1 year, waves in the ENE-S direction are applied sequentially at the model boundary; when the simulation time is more than one year, the wave conditions of the first year are repeated every year starting from the second year; use the beach evolution model to conduct long-term simulation calculations of large floating structures, and quantitatively calculate the action time of each level of waves on an annual scale and the longshore sediment transport volume according to the wave hierarchical and directional statistical data, and obtain the prediction results of the influence of large floating structures on the trend of beach evolution.

2. A quantitative method for predicting the impact of a large offshore floating structure on shoreline evolution according to claim 1, characterized in that: The project sea area includes the area outside the breaking wave zone and inside the offshore engineering area.

3. A quantitative method for predicting the impact of a large offshore floating structure on shoreline evolution according to claim 1, characterized in that: The transmission coefficient of the transmission breakwater is related to the geometric shape of the large floating structure, and the transmission coefficient of the transmission breakwater is determined by physical tests or numerical tests in a water tank.

4. A quantitative method for predicting the impact of a large offshore floating structure on shoreline evolution according to claim 1, characterized in that: The wave direction of the waves refers to the angle between the main traveling direction of the waves and the true north direction of the earth, and the action frequency of waves in each direction is statistically obtained from the wave data measured throughout the year in the study area, representing the number of days of the action of each level of waves in a year.

5. A quantitative method for predicting the impact of a large offshore floating structure on shoreline evolution according to claim 1, characterized in that: Taking the spatially continuous wave elements as the open boundary of the model in the beach evolution model specifically includes: giving wave condition parameters at each grid node of the open boundary of the beach evolution model, including significant wave height, mean period, and wave direction angle.

6. A quantitative method for predicting the impact of a large offshore floating structure on shoreline evolution according to claim 1, characterized in that: The specific wave condition parameter values along the open boundary are obtained by calculating the wind-generated waves simulated based on the dynamic spectral balance equation.

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