Quantitative method for predicting influence of large offshore floating structure on beach evolution

Abstract

The invention discloses a quantitative method for predicting the influence of a large offshore floating structure on beach evolution, and aims to provide a beach evolution trend prediction method which is more accurate and efficient so as to solve the problem that the effect of an offshore large floating structure project on waves cannot be considered in an existing beach evolution prediction model. According to the method, on the basis of a dynamic spectrum balance equation, waves in different wave directions after the offshore large floating structure engineering is implemented are obtained through simulation by arranging a plurality of sections of closed transmission dikes, so that the wave boundary conditions of a beach evolution model are determined; the method comprises the following steps: taking wave elements in spatial continuous distribution as open boundaries of a beach evolution model, and quantitatively calculating the action time of each stage of wave in an annual scale and the coastal sediment transport according to wave grading and direction statistical data, so as to predict the influence trend of an offshore large floating structure project in the annual scale on beach evolution.

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 influence of a large offshore floating structure on beach evolution. Background Art

[0002] Sandy beaches undertake important ecological service functions such as purifying water quality, buffering land and ocean, and regulating climate, and play an irreplaceable role in maintaining global ecological balance. Currently, the construction of large offshore floating structure projects around sandy coastlines 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, since large offshore floating structures occupy a large area, they affect the diffraction and transmission propagation of most incoming waves, thereby changing the nearshore wave energy distribution, affecting the coastal sand transport process in the engineering sea area, and having a certain impact on the beach evolution trend in the engineering sea area. The existing beach evolution prediction model cannot take into account the site selection of large offshore projects and the impact of structural wave breaking, thereby reducing the realism of the prediction model. Summary of the invention

[0004] The present invention provides a quantitative method for predicting the influence of large offshore floating structures on beach evolution, so as to solve the problem that the beach evolution prediction model in the prior art cannot consider the site selection of large offshore projects and the influence of structural wave dissipation.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: A quantitative method for predicting the impact of large offshore floating structures on beach evolution includes the following steps: S1, determining wave boundary conditions; S2, generalizing important wave condition parameters; S3, determining model open boundaries; S4, determining simulation time; S5, simulating prediction results.

[0006] Preferably, S1 specifically includes: using the dynamic spectrum balance equation in combination with wind field data to derive a large-scale wave field in the past 10 years, simulating waves of different wave directions after the implementation of the offshore large-scale floating structure project by setting up multiple sections of closed transmission dikes, and obtaining graded and directional wave data of deep water in the engineering sea area in the past 10 years by statistically analyzing the wave results, and thereby determining the wave boundary conditions of the shore evolution model.

[0007] Preferably, the engineering sea area includes the area outside the wave-breaking zone and within the offshore engineering area.

[0008] Preferably, the transmission coefficient of the transmission dam is related to the geometric shape of the large floating structure and can be determined by water tank physical test or numerical test calculation.

[0009] Preferably, S2 specifically includes: selecting the root mean square value of each level of wave height as the representative wave height, and the calculation formula is H1 / 10 = m, where X and Y represent the minimum and maximum wave heights of waves of this level respectively.

[0010] Preferably, the S2 specifically includes: calculating the effective wave height and action time, wherein the effective wave height is taken as H according to the "Hydrological Specifications for Ports and Waterways" s =H 1 / 10 / 1.27; Action time (h) = frequency × 365 × 24h / day.

[0011] Preferably, the wave direction refers to the angle between the main direction of wave travel and the earth's due north direction. The frequency of wave action in each direction is obtained from the wave data measured throughout the year in the study area, indicating the number of days in a year when waves of this level act.

[0012] Preferably, S3 specifically includes: assuming that waves and wave-induced 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 a one-line model, and the spatially continuously distributed wave elements are used as the open boundaries of the model.

[0013] Preferably, in the beach evolution model, the spatially continuously distributed 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 effective wave height, average period, and wave direction angle.

[0014] Preferably, specific wave condition parameter values ​​along the open boundary can be obtained by calculating wind surge waves based on dynamic spectrum balance equation simulation.

[0015] Preferably, the S4 specifically includes: the simulation time is converted according to the frequency of waves of each level, indicating the number of days in a year when waves of this level act.

[0016] Preferably, S5 specifically includes: when the simulation time is 1 year, based on the wave rose diagram measured annually, waves of normal wave direction and strong wave direction of the engineering sea area act on the model boundary in sequence; when the simulation time is greater than one year, the wave conditions of the first year are repeated every year starting from the second year.

[0017] Preferably, S5 specifically includes: using a shore evolution model to perform long-term simulation calculations of large-scale floating structures, quantitatively calculating the wave action time and coastal sediment transport at each level on an annual scale based on wave classification and direction statistics, and obtaining prediction results of the large-scale floating structure on the shore evolution trend.

[0018] The principle and beneficial effects of this technical solution: (1) The calculation method in the present invention can be based on the dynamic spectrum balance equation. By setting up multiple closed transmission dikes to simulate the waves of different wave directions after the implementation of the offshore large-scale floating structure project, the wave boundary conditions of the beach evolution model can be determined, and the regional division of waves of different wave directions can be realized. At the same time, the boundary conditions of waves of different levels are defined.

[0019] (2) The present invention uses spatially continuously distributed wave elements as the open boundary of the beach evolution model. Based on the statistical data of wave classification and direction, the wave action time and the amount of sediment transported along the coast at each level on an annual scale are quantitatively calculated, thereby predicting the impact trend of large offshore floating structure projects on beach evolution on an annual scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of the steps of the present invention; Figure 2 is the representative wave height of each level of waves in the numerical simulation and its corresponding simulation time; DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments: Example:

[0022] like Figure 2 As shown, taking Hongtang Bay in Sanya City, Hainan Province as an example: ESE acts on point A11 with a wave height of 1.5m for 445 hours; ESE acts on point A11 with a wave height of 2.1m for 397 hours; SW acts on point A11 with a wave height of 3m for 28.5 hours; ESE acts on point A11 with a wave height of 4m for 5.18 hours; WSW acts on point A11 with a wave height of 3m for 8.6 hours; WSW acts on point A11 with a wave height of 4m for 2.6 hours.

[0023] like Figure 1 As shown, the present invention provides a quantitative method for predicting the impact of large offshore floating structures on beach evolution, including the following steps: S1, determining wave boundary conditions; S2, generalizing important wave condition parameters; S3, determining model open boundaries; S4, determining simulation time; S5, simulating prediction results.

[0024] like Figure 1 As shown in FIG, S1 specifically includes: using the dynamic spectrum balance equation and combining it with the wind field data to obtain the large-scale wave field in the past 10 years, simulating the waves of different wave directions after the implementation of the offshore large-scale floating structure project by setting up multiple sections of closed transmission dikes, and obtaining the graded and directional wave data of the deep water of the project sea area in the past 10 years by statistical wave results, and thereby determining the wave boundary conditions of the shore evolution model.

[0025] like Figure 1 As shown, the engineering sea area includes the area outside the wave-breaking zone and within the offshore engineering area.

[0026] like Figure 1 As shown, the transmission coefficient of the transmissive dike is related to the geometric shape of the large floating structure and can be determined by water tank physical tests or numerical test calculations.

[0027] like Figure 1 As shown, S2 specifically includes: selecting the root mean square value of each level of wave height as the representative wave height, and the calculation formula is H 1 / 10 = m, where X and Y represent the minimum and maximum wave heights of waves of this level respectively.

[0028] like Figure 1 As shown, S2 specifically includes: calculating the effective wave height and action time, where the effective wave height is taken as H according to the "Hydrological Specifications for Ports and Waterways". s =H 1 / 10 / 1.27; Action time (h) = frequency × 365 × 24h / day.

[0029] like Figure 1 As shown, wave direction refers to the angle between the main direction of wave travel and the earth's true north direction. The frequency of wave action in each direction is obtained from the wave data measured throughout the year in the study area, indicating the number of days in a year when waves of this level act.

[0030] like Figure 1 As shown, S3 specifically includes: assuming that waves and wave-induced 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 continuously distributed wave elements are used as the open boundaries of the model.

[0031] like Figure 1 As shown, in the beach evolution model, the spatially continuously distributed 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 the effective wave height, average period, and wave direction angle.

[0032] like Figure 1 As shown in Figure 2, the specific wave condition parameter values ​​along the open boundary can be obtained by calculating the wind surge wave based on the dynamic spectrum balance equation simulation.

[0033] like Figure 1 As shown, S4 specifically includes: the simulation time is converted according to the frequency of waves of each level, indicating the number of days in a year when waves of this level act.

[0034] like Figure 1 As shown, S5 specifically includes: when the simulation time is 1 year, waves in the ESE-W direction act on the model boundary in sequence; when the simulation time is greater than one year, the wave conditions of the first year are repeated every year starting from the second year.

[0035] like Figure 1 As shown, S5 specifically includes: using the shore evolution model to perform long-term simulation calculations of large-scale floating structures, quantitatively calculating the wave action time and coastal sediment transport at each level on an annual scale based on wave classification and direction statistics, and obtaining the prediction results of the large-scale floating structure on the shore evolution trend.

[0036] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification 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 beach evolution, characterized in that: The following steps are involved: S1. Determine the wave boundary conditions; S2. Generalize the important wave parameters; S3. Determine the model opening boundary; S4. Determine the simulation time; S5. Simulate the prediction results.

2. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 1, characterized in that: The S1 specifically includes: using the dynamic spectrum balance equation in combination with wind field data to derive a large-scale wave field in the past 10 years, simulating waves of different wave directions after the implementation of the offshore large-scale floating structure project by setting up multiple sections of closed transmission dikes, and obtaining the graded and directional wave data of the deep water of the project sea area in the past 10 years through statistical wave results, and thereby determining the wave boundary conditions of the shore evolution model.

3. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 2, characterized in that: The engineering sea area includes the area outside the wave-breaking zone and within the offshore engineering area.

4. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 2, characterized in that: The transmission coefficient of the transmission dam is related to the geometric shape of the large floating structure and can be determined by water tank physical test or numerical test calculation.

5. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 1, characterized in that: S2 specifically includes: selecting the root mean square value of each level of wave height as the representative wave height, the representative wave height H 1 / 10 The calculation formula is H 1 / 10 = m, where X and Y represent the minimum and maximum wave heights of waves of this level respectively.

6. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 1, characterized in that: The S2 specifically includes: calculating the effective wave height and action time, wherein the effective wave height H s =H 1 / 10 / 1.27; Action time (h) = frequency × 365 × 24h / day.

7. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 1, characterized in that: The wave direction refers to the angle between the main direction of wave travel and the earth's true north direction. The frequency of wave action in each direction is obtained from the wave data measured throughout the year in the study area, indicating the number of days in a year when waves of this level act.

8. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 1, characterized in that: The S3 specifically includes: assuming that waves and wave-induced 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 continuously distributed wave elements are used as the open boundaries of the model.

9. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 8, characterized in that: In the shore evolution model, the spatially continuously distributed 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 shore evolution model, including effective wave height, average period, and wave direction angle.

10. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 8, characterized in that: The specific wave condition parameter values ​​along the open boundary can be obtained by calculating the wind surge waves based on the dynamic spectrum balance equation simulation.

11. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 1, characterized in that: The S4 specifically includes: the simulation time is converted according to the frequency of waves of each level, indicating the number of days in a year when waves of this level act.

12. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 11, characterized in that: The S5 specifically includes: when the simulation time is 1 year, waves in the ENE-S direction act on the model boundary in sequence; when the simulation time is greater than one year, the wave conditions of the first year are repeated every year starting from the second year.

13. A quantitative method for predicting the impact of large offshore floating structures on beach evolution according to claim 1, characterized in that: The S5 specifically includes: using the shore evolution model to perform long-term large-scale floating structure simulation calculations, quantitatively calculating the wave action time and coastal sediment transport at each level on an annual scale based on wave classification and direction statistics, and obtaining the prediction results of the large-scale floating structure on the shore evolution trend.

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