Bragg resonance breakwater design method and breakwater

Abstract

This invention provides a Bragg resonance breakwater design method and breakwater. The Bragg resonance breakwater design method includes acquiring wave field characteristic parameters of the target sea area and determining the target wave frequency band based on the wave field characteristic parameters; determining the target wave frequency of each resonant unit based on the target wave frequency band, and determining the geometric parameters of the resonant cavity of the resonant unit based on the target wave frequency, so that the inherent resonant frequency of the resonant cavity matches the target wave frequency; determining the reflection coefficient index to characterize the wave dissipation effect based on the target wave frequency band, and determining the arrangement parameters of each resonant unit based on the reflection coefficient index under the premise of satisfying preset constraints, wherein the arrangement parameters change stepwise along the incident wave propagation direction; and outputting the resonant cavity geometric parameters and arrangement parameters corresponding to each resonant unit to form a Bragg resonance breakwater design scheme.

Description

Technical Field

[0001] This invention relates to the field of coastal engineering and port hydraulic structures, and in particular to a design method for a Bragg resonance breakwater and a breakwater thereof. Background Technology

[0002] Breakwaters are core hydraulic structures in port and coastal engineering, primarily responsible for resisting the impact of open sea waves, maintaining the stability of harbor waters, preventing siltation, guiding water flow, and protecting natural coastlines from erosion. They provide safety for ship berthing, loading and unloading operations, and harbor facilities. With increasing demands for ecological protection and landscape harmony in marine engineering, submerged breakwater structures with their crests below the calm water surface are gaining increasing attention. Among these, the Bragg resonant breakwater utilizes the periodic interaction between waves and seabed topography to generate strong reflections. Compared to traditional solid breakwaters, it offers significant advantages such as substantial wave dissipation, no obstruction of water exchange, protection of the marine ecosystem, and no visual impact on the seascape, making it an important technical form in coastal protection engineering.

[0003] However, existing Bragg resonant breakwaters still have limitations in practical applications, mainly in their insufficient defense against low-frequency, broadband long waves under complex sea conditions. Traditional Bragg breakwaters typically employ a periodic arrangement with fixed spacing. This singular geometry means that they only generate effective resonance within a specific narrow frequency band, making it difficult to cover a wide frequency range of incident waves. This results in a sharp decrease in the reflection effect on waves deviating from the design frequency. Furthermore, existing structures often use a uniform submersion depth, which, when facing long-period, high-energy, and highly penetrating long waves, cannot provide sufficient physical obstruction in the critical areas where long waves are at play. This allows a large amount of long-wave energy to pass through the breakwater and be transmitted, causing protective failure. Summary of the Invention

[0004] This invention provides a Bragg resonance breakwater design method and breakwater, which solves the technical problem of insufficient defense capability against low-frequency, broadband long waves under complex sea conditions in the prior art.

[0005] This invention provides a Bragg resonance breakwater design method. The breakwater includes multiple resonant units arranged in an array along the direction of incident wave propagation. The method includes: acquiring wave field characteristic parameters of a target sea area and determining a target wave frequency band based on the wave field characteristic parameters; determining the target wave frequency of each resonant unit based on the target wave frequency band, and determining the geometric parameters of the resonant cavity of the resonant unit based on the target wave frequency, so that the natural resonant frequency of the resonant cavity matches the target wave frequency; determining a reflection coefficient index to characterize the wave dissipation effect based on the target wave frequency band, and determining the arrangement parameters of each resonant unit according to the reflection coefficient index under the premise of satisfying preset constraints, wherein the arrangement parameters change stepwise along the direction of incident wave propagation; and outputting the resonant cavity geometric parameters corresponding to each resonant unit and the arrangement parameters to form the design scheme of the Bragg resonance breakwater.

[0006] According to the Bragg resonance breakwater design method provided by the present invention, determining the arrangement parameters of each resonance unit based on the reflection coefficient index includes: determining the horizontal spacing between each adjacent resonance unit; and determining the submersion depth of each resonance unit.

[0007] According to the Bragg resonance breakwater design method provided by the present invention, determining the horizontal spacing between adjacent resonant units includes: determining the horizontal spacing between the first pair of adjacent resonant units located on the starting side of the incident wave propagation direction as the initial spacing; determining the spacing increment of the horizontal spacing between adjacent resonant units that increases progressively along the incident wave propagation direction; and determining the horizontal spacing between adjacent resonant units sequentially according to the arrangement order of the resonant units based on the initial spacing and the spacing increment.

[0008] According to the Bragg resonance breakwater design method provided by the present invention, determining the inundation depth of each of the resonance units includes: determining the inundation depth of the resonance unit located on the starting side of the incident wave propagation direction as the initial inundation depth; determining the amount of inundation depth change used to characterize the gradual decrease of the inundation depth along the incident wave propagation direction; and determining the inundation depth of each resonance unit in sequence according to the arrangement order of the resonance units based on the initial inundation depth and the amount of inundation depth change.

[0009] According to the Bragg resonance breakwater design method provided by the present invention, the step of determining the arrangement parameters of each resonance unit based on the reflection coefficient index includes: taking maximizing the reflection coefficient index as the objective function, iteratively solving the initial spacing, the spacing increment, the initial flooding depth, and the change in flooding depth under the preset constraints to optimize the arrangement parameters.

[0010] According to the Bragg resonance breakwater design method provided by the present invention, the geometric parameters of the resonant cavity include cavity parameters disposed inside the cavity of the resonant unit and opening parameters of the opening connecting the cavity and the external water body; determining the geometric parameters of the resonant cavity of the resonant unit according to the target wave frequency includes: determining a target value of the natural resonant frequency of the resonant cavity according to the target wave frequency corresponding to the resonant unit; determining the cavity parameters and opening parameters according to the natural resonant frequency, so that the natural resonant frequency determined by the opening parameters and the cavity parameters matches the target value.

[0011] The Bragg resonance breakwater design method provided by the present invention further includes: establishing a numerical calculation model for calculating the reflection coefficient within the target wave frequency band based on the arrangement parameters and the resonant cavity geometric parameters; calculating the value of the reflection coefficient index through the numerical calculation model, and comparing the value of the reflection coefficient index with a preset design index; if the value of the reflection coefficient index does not meet the preset design index, iteratively adjusting the arrangement parameters and / or the resonant cavity geometric parameters until the value of the reflection coefficient index meets the preset design index.

[0012] The Bragg resonance breakwater design method provided by the present invention further includes: constructing a solid model based on the arrangement parameters and the resonant cavity geometric parameters and conducting a flue test; measuring the reflection coefficient index value within the target wave frequency band in the flue test and comparing the measured value with the preset design index; and iteratively adjusting the arrangement parameters and / or the resonant cavity geometric parameters if the measured value does not meet the preset design index, until the reflection coefficient index value meets the preset design index.

[0013] According to the Bragg resonance breakwater design method provided by the present invention, the step of determining the target wave frequency of each of the resonance units based on the target wave frequency band includes: dividing the target wave frequency band into multiple sub-frequency bands; establishing a correspondence between each of the sub-frequency bands and the arrangement order of the resonance units according to the incident wave propagation direction; and determining the representative frequency of the sub-frequency band as the target wave frequency of the corresponding resonance unit based on the correspondence.

[0014] The present invention also provides a lag resonance breakwater, comprising: a plurality of resonant units arranged in an array along the propagation direction of incident waves, wherein the arrangement parameters of each resonant unit vary stepwise along the propagation direction of the incident waves; each resonant unit includes a resonant cavity, the resonant cavity including a cavity disposed inside the resonant unit and an opening connecting the cavity to the external water body; wherein the cavity parameters of the internal cavity and the opening parameters of the opening together determine the inherent resonant frequency of the resonant cavity that matches the target frequency corresponding to the resonant unit.

[0015] The Bragg resonance breakwater design method and breakwater provided by this invention, by acquiring the wave field characteristic parameters of the target sea area and determining the target wave frequency band, can determine the target wave frequency to be damped by each resonant unit according to actual needs, and thereby determine the geometric parameters of the resonant cavity to match the inherent resonant frequency of the resonant cavity with the target wave frequency, thus achieving the wave damping effect. This extends the traditional Bragg resonance breakwater's focus on a single design frequency to the target frequency band of the actual incident wave spectrum, allowing different resonant units to form targeted resonant coupling and energy dissipation for different frequency components within the target frequency band. Furthermore, a reflection coefficient index is constructed based on the target wave frequency band to characterize the wave damping effect, and under preset constraints, the arrangement parameters that vary stepwise along the incident wave propagation direction are determined according to this reflection coefficient index. This allows the spatial periodicity of the array and the resonant characteristics of the units to be coordinated and adjusted according to the frequency band requirements along the propagation direction, thereby expanding the effective reflection / dissipation working frequency band, reducing dependence on fixed-period narrowband resonance, and avoiding the sharp decline in reflection effect when deviating from a single design frequency, thus ensuring the defense capability against low-frequency, broadband long waves in complex sea conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 A schematic diagram of a Bragg resonance breakwater according to an embodiment of the present invention is shown; Figure 2 A flowchart illustrating the Bragg resonance breakwater design method according to an embodiment of the present invention is shown schematically. Figure 3 The flowchart illustrating the determination of the horizontal spacing between adjacent resonant units according to an embodiment of the present invention is shown in the schematic diagram. Figure 4This is a schematic flowchart illustrating the determination of the submersion depth of each resonant unit according to an embodiment of the present invention.

[0018] Figure label: 11 - First Resonant Unit; 12 - Second Resonance Unit; 13 - Third Resonance Unit; 14 - Fourth Resonance Unit. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] In related technologies, the array of resonant units of the Bragg resonant breakwater is designed based on a single target frequency. Such structures often employ a periodic arrangement with a fixed spacing. This single geometric structure determines that it can only generate effective resonance within a specific narrow frequency band, making it difficult to cover a wide frequency band of incident wave spectrum, resulting in a sharp decrease in the wave reflection effect deviating from the design frequency.

[0021] In view of this, the present invention provides a design method for a Bragg resonance breakwater.

[0022] Figure 1 A schematic diagram of a Bragg resonance breakwater according to an embodiment of the present invention is shown.

[0023] like Figure 1 As shown, the Bragg resonance breakwater comprises multiple resonant units arranged in an array along the propagation direction of the incident waves, with the arrangement parameters of each resonant unit varying progressively along the propagation direction of the incident waves.

[0024] Each resonant unit is constructed with a resonant cavity, which includes an internal cavity and an opening connecting the cavity to the external water body. The cavity parameters of the internal cavity and the opening parameters of the opening together determine the natural resonant frequency of the resonant cavity that matches the target frequency corresponding to the resonant unit.

[0025] According to an embodiment of the present invention, the opening of the resonant cavity can be provided on the top and from the side of the resonant unit to generate local oscillation resonance. This is because when the target frequency is close to the inherent resonant frequency of the resonant cavity, the resonant cavity will generate a strong response. By combining the wave-damping range generated by the local resonance of the resonant cavity with the Bragg resonance generated by each resonant unit, effective wave-damping can be achieved from a wider frequency range.

[0026] According to an embodiment of the present invention, the arrangement parameters include the horizontal spacing between adjacent resonant units and the submersion depth of each resonant unit. Specifically, the horizontal spacing between adjacent resonant units increases progressively along the direction of incident wave propagation, while the submersion depth of each resonant unit decreases progressively along the direction of incident wave propagation.

[0027] Figure 2 The flowchart illustrating the Bragg resonance breakwater design method according to an embodiment of the present invention is shown.

[0028] like Figure 2 As shown, the Bragg resonance breakwater design method includes operations S210~S240.

[0029] In operation S210, the wave field characteristic parameters of the target sea area are obtained, and the target wave frequency band is determined based on the wave field characteristic parameters.

[0030] According to embodiments of the present invention, wave field characteristic parameters may include wave spectral distribution, dominant frequency range of incident waves, extreme long-wave period, and local average water depth. Exemplarily, wave and water level data for at least one complete hydrological year can be collected using marine hydrological monitoring equipment (e.g., wave buoys or acoustic Doppler current profilers, ADCP) installed in the target sea area. Statistical analysis is performed on the collected data to determine the local average water depth h0.

[0031] According to an embodiment of the present invention, the acquired time-domain wavefront data can be converted into a frequency-domain spectrum using a Fast Fourier Transform (FFT) to obtain the wave spectral distribution. Based on the spectral peak frequencies and the energy distribution characteristics of low-frequency long waves, the dominant frequency range of incident waves requiring key defense is defined. and extreme long-wave period .

[0032] Among them, the dominant frequency range of the incident wave It is preset based on the energy accumulation distribution function of historical wave data in the target sea area. For example, the dominant frequency range of the incident wave can be set to the frequency range corresponding to the accumulation of energy reaching 5% to 95% of the total energy. The extreme long-wave period is preset based on the return period standard (such as once in 50 years). For example, the extreme long-wave period can be set to... Or higher.

[0033] According to an embodiment of the present invention, the target wave frequency band refers to the frequency range that characterizes the main energy distribution range of incident waves in the target sea area. The dominant frequency range of the incident waves can be determined as the target wave frequency band, or an area of ​​interest can be further selected within the dominant frequency range of the incident waves as the target wave frequency band.

[0034] For example, a trapezoidal breakwater can be selected as the basic configuration of the resonant unit, and the bottom width, top width, and wave-facing slope of the resonant unit can be initially set, followed by optimization and iteration through numerical simulation or experimental simulation. To ensure the stability of the breakwater structure and effective guidance of wave rise, the wave-facing slope is usually set between 1:1.5 and 1:3.

[0035] In operation S220, the target wave frequency of each resonant unit is determined based on the target wave frequency band, and the geometric parameters of the resonant cavity of the resonant unit are determined according to the target wave frequency so that the inherent resonant frequency of the resonant cavity matches the target wave frequency.

[0036] According to an embodiment of the present invention, the target wave frequency band can be divided into multiple sub-bands, and different representative frequencies of different sub-bands can be assigned to different resonant units as target wave frequencies, thereby attenuating wave energy by designing the structure and arrangement parameters of each resonant unit separately.

[0037] According to an embodiment of the present invention, the resonant cavity is a cavity structure disposed inside the resonant unit and connected to the external water body. When the frequency of the wave is approximately the same as the inherent resonant frequency of the resonant cavity, the energy of the wave can be dissipated through resonance. Generally, when waves propagate in the array and Bragg resonance occurs, waves of a specific frequency will generate a slow wave effect at a specific location, resulting in an increase in local fluid velocity and energy accumulation. At this time, the resonant cavity utilizes the strong turbulence effect at the opening and the vortex motion inside the cavity to convert the accumulated wave kinetic energy into heat energy for dissipation.

[0038] For example, the geometric parameters of the resonant cavity may include the equivalent volume of the cavity, the equivalent cavity depth, the equivalent cross-sectional dimensions, the equivalent opening area of ​​the opening, and the equivalent neck length associated with the opening.

[0039] According to an embodiment of the present invention, in order to achieve efficient action on broadband waves, the cavity resonant frequencies inside the resonant units at different positions in the array need to be designed with gradients. (The text then abruptly shifts to a different topic: setting the first...) The resonant cavities within each resonant unit satisfy the cavity frequency matching condition formula: ; In the formula: For the first The inherent resonant frequency of the velocity-sensitive energy-dissipating cavity inside each resonant unit; For the first The target wave frequency is captured by each resonant element, and the Bragg resonant cutoff frequency corresponds to the resonant element in the dual gradient array.

[0040] In operation S230, the reflection coefficient index used to characterize the wave dissipation effect is determined based on the target wave frequency band, and under the premise of meeting the preset constraints, the arrangement parameters of each resonance unit are determined according to the reflection coefficient index. The arrangement parameters change step by step along the direction of incident wave propagation.

[0041] According to an embodiment of the present invention, the reflection coefficient index can be a comprehensive index of the reflection coefficients of multiple single-frequency waves within the target wave frequency band, such as a comprehensive evaluation quantity formed by averaging, weighted averaging, or taking the maximum / minimum value of the reflection coefficients at each frequency point; wherein, the weighting method can be determined according to the wave spectrum distribution of the target sea area so that the reflection coefficient index can reflect the wave dissipation requirements of the main energy components within the target wave frequency band.

[0042] According to embodiments of the present invention, the preset constraints may include at least one of engineering feasibility constraints and functional constraints, such as spatial range constraints, geometric constraints to prevent structural interference between adjacent resonant units, submersion state constraints of resonant units, material and construction capability constraints, and safety and stability constraints.

[0043] According to an embodiment of the present invention, the arrangement parameters include at least the horizontal spacing between each adjacent resonant unit and the submersion depth of each resonant unit; the arrangement parameters may also further include the number of resonant units, the array length, and the arrangement of the resonant units in the lateral direction, etc.

[0044] In one embodiment, when the arrangement parameters include the horizontal spacing between adjacent resonant units, the gradual change of the arrangement parameters along the direction of incident wave propagation can be characterized by a sequence of horizontal spacings composed of the horizontal spacings between adjacent resonant units. Optionally, the sequence of horizontal spacings can be determined by an initial spacing and the amount of spacing change. For example, the center spacing between the first pair of adjacent resonant units located on the starting side of the direction of incident wave propagation can be determined as the initial spacing, and the center spacing of subsequent adjacent resonant units can be determined sequentially according to a preset change rule.

[0045] In another embodiment, when the arrangement parameters include a submersion depth sequence composed of the submersion depths of each resonant unit, the submersion depth sequence can be determined by the initial submersion depth and the amount of change in submersion depth. For example, the submersion depth of the resonant unit located at the starting side of the incident wave propagation direction is determined as the initial submersion depth, and the submersion depth of the subsequent resonant units is determined sequentially according to a preset change rule.

[0046] The gradual change pattern can be arithmetic progression, piecewise variation, nonlinear variation, or other variation methods that satisfy the characteristics of gradual change, in order to adapt to different target wave frequency bands or different engineering constraints.

[0047] During operation S240, the geometric parameters and arrangement parameters of the resonant cavities corresponding to each resonant unit are output to form the design scheme of the Bragg resonant breakwater.

[0048] By employing the aforementioned configuration, target wave frequencies are assigned to multiple resonant units, and matching resonant cavity geometric parameters are determined. This ensures that the inherent resonant frequencies of different resonant units can cover the target wave frequency band. Based on the reflection coefficient index, arrangement parameters that gradually change along the incident wave propagation direction are determined under preset constraints, allowing the spatial arrangement of the array to match the waves at each target frequency. This reduces the narrow-band dependence on single-period geometry, expands the effective reflection and dissipation operating frequency band, and mitigates the problem of declining wave-damping performance when deviating from the design frequency. Consequently, it enhances the applicability and stability of the breakwater's wave-damping effect under broadband incident wave spectrum conditions.

[0049] In one illustrative embodiment, the arrangement parameters of each resonant unit are determined based on the reflection coefficient index, including: determining the horizontal spacing between each adjacent resonant unit; and determining the submersion depth of each resonant unit.

[0050] Figure 3 The flowchart illustrating the determination of the horizontal spacing between adjacent resonant units according to an embodiment of the present invention is shown.

[0051] like Figure 3 As shown, the process for determining the horizontal spacing between adjacent resonant units includes operations S310 to S330.

[0052] In operation S310, the horizontal spacing between the first pair of adjacent resonant units located on the starting side of the incident wave propagation direction is determined as the initial spacing.

[0053] According to an embodiment of the present invention, the starting side of the incident wave propagation direction refers to the upstream side or the wave-facing side along the incident wave propagation direction.

[0054] According to embodiments of the present invention, the initial spacing can be determined by considering factors such as the available space for engineering layout, construction feasibility, and the wavelength scale corresponding to the target wave frequency band. The initial spacing primarily determines the starting point of the array's response to high-frequency shortwave.

[0055] In operation S320, the spacing increment between adjacent resonant units is determined as the horizontal spacing increases progressively along the direction of incident wave propagation.

[0056] In operation S330, based on the initial spacing and spacing increment, the horizontal spacing between each adjacent resonant unit is determined sequentially according to the arrangement order of the resonant units.

[0057] According to an embodiment of the present invention, the spacing increment refers to the change in the horizontal spacing between adjacent resonant units in the array arrangement direction, which is used to make the adjacent spacing change step by step along the direction of incident wave propagation.

[0058] For example, the horizontal spacing is marked as And satisfy The increasing relationship. To achieve spatial sorting of different frequency components in the incident wave spectrum (i.e., rainbow capture mechanism), multiple resonant units are arranged with non-equidistant spacing along the wave propagation direction. The spacing between adjacent resonant units is not a fixed value, but increases in an arithmetic sequence. The resonant unit and the first The positional relationship between the resonant elements is defined by the following formula for calculating the horizontal spacing: ; In the formula: For the first The resonant unit and the first The horizontal spacing between each resonant unit; The initial spacing is the horizontal spacing between the first and second resonant units at the beginning of the array. This parameter mainly determines the starting point of the array's response to high-frequency shortwave. As the spacing increment, this parameter controls the rate of change of the horizontal spacing, which in turn determines the width of the array's capture bandwidth and frequency resolution.

[0059] Specifically, according to the Bragg resonance principle, the first Each resonant unit primarily targets wavelengths of... The waves produce strong reflections. Due to the wavelength... With frequency Negative correlation (i.e.) ), with horizontal spacing As the numbers increase in an arithmetic progression, the resonant wavelength of the array increases progressively, while the resonant frequency decreases progressively. Therefore, this formula establishes the array front end ( Smaller Smaller) mainly captures high-frequency shortwave, array back end ( Larger The larger one mainly captures the physical correspondence of low-frequency long waves, thereby achieving rainbow capture of broadband waves through the design of geometric gradient.

[0060] Horizontal gradient (i.e., horizontal spacing) The Bragg resonance bandgap, arranged in an arithmetic progression, gradually varies along the direction of incident wave propagation. High-frequency, short-wavelength components in the incident spectrum satisfy the Bragg resonance condition (i.e., the local lattice constant matches the half-wavelength) at the smaller spacing at the front of the array, causing the group velocity to decrease and approach zero, resulting in a slow-wave effect and localizing energy at the front. Meanwhile, the highly transmissive low-frequency, long-wavelength components continue to propagate until they reach the larger spacing at the rear of the array, where the resonance condition is satisfied and energy accumulates. This mechanism achieves spatial sorting of wave frequencies (i.e., the rainbow effect).

[0061] In some embodiments, the spacing increment can be set to a constant, so that the array spacing increases gradually in an arithmetic progression; in other embodiments, the spacing increment can also be set to a function related to the resonant unit number, so that the spacing increases piecewise in an arithmetic progression or nonlinearly, to adapt to the frequency distribution of different target wave frequency bands.

[0062] Figure 4 This is a schematic flowchart illustrating the determination of the submersion depth of each resonant unit according to an embodiment of the present invention.

[0063] like Figure 4 As shown, the process for determining the flooding depth of each resonant unit includes operations S410~S430.

[0064] In operation S410, the submersion depth of the resonant unit located on the starting side of the incident wave propagation direction is determined as the initial submersion depth.

[0065] In operation S420, the amount of change in inundation depth is determined to characterize the gradual decrease in inundation depth along the direction of incident wave propagation.

[0066] In operation S430, based on the initial flooding depth and the change in flooding depth, the flooding depth of each resonant unit is determined sequentially according to the arrangement order of the resonant units.

[0067] According to an embodiment of the present invention, in order to solve the problem of traditional Bragg breakwaters failing to defend against low-frequency long waves due to significant transmission effects, this embodiment adopts a reverse height gradient design. That is, according to the sequence number... As the wavelength increases (corresponding to a longer capture wavelength), the submersion depth of the submerged dike gradually decreases, and the dike body gradually increases in height.

[0068] The submersion depth of each resonant element is defined by the following formula: ; In the formula: For the first The submersion depth of each resonant unit is the vertical distance from the top surface of the resonant unit to the still water surface. This is the initial flooding depth, i.e., the flooding depth of the first resonant unit in the array; The submergence depth reduction coefficient determines the slope of the array height gradient and is used to determine the progressively decreasing submergence depth. It is crucial to ensure that the calculated submergence depth of the final resonant unit meets the minimum water depth requirements for navigation and construction.

[0069] Based on the above-mentioned inundation depth and combined with the local average water depth, the physical height of the resonant element is calculated: ; In the formula: For the first The actual physical height of each resonant unit, i.e., the vertical distance from the bottom of the seabed to the top of the submerged breakwater; This represents the local average water depth.

[0070] Vertical gradient (i.e., physical height) (Increasing in reverse order) and coupled with the aforementioned horizontal spatial sorting mechanism. Given that the wave energy of low-frequency long waves decays slowly with water depth and is prone to transmission, by reducing the submersion depth and increasing the physical height at the rear end of the array (i.e., the long-wave capture area), the hydrodynamic characteristics of long waves can be effectively matched. Sufficient physical impedance is provided at the energy accumulation point to suppress transmission, causing the accumulated energy to be reflected or dissipated into the energy dissipation cavity, thereby ensuring efficient defense across the entire broadband range.

[0071] Through the above steps, a horizontal spacing in space is constructed. Gradually increase, vertical height The progressively increasing dual-gradient structure ensures that long waves are captured at the rear of the array while being subjected to stronger physical obstruction.

[0072] In one illustrative embodiment, the arrangement parameters of each resonant unit are determined based on the reflection coefficient index, including: taking the maximization of the reflection coefficient index as the objective function, iteratively solving the initial spacing, spacing increment, initial flooding depth, and flooding depth change under preset constraints to optimize the arrangement parameters.

[0073] For example, the algorithm is optimized. The initial spacing is... Increasing Spacing Tolerance Initial flood depth and the inundation depth reduction factor These variables are set as the variables to be optimized. An optimization algorithm (such as a genetic algorithm, particle swarm optimization, or simulated annealing) is used to iteratively solve for these variables under preset constraints.

[0074] According to an embodiment of the present invention, the constraints include: Geometric constraints: ensure that adjacent submerged breakwater resonant elements do not physically overlap; Water depth constraints: ensuring the submersion depth at any location Greater than the minimum navigable depth or ecological depth; Quantity constraint: Total number of resonant units Within the limits of economic cost.

[0075] After the optimization calculation is completed, a set of optimal parameter combinations is output. Based on this, a detailed array layout coordinate sequence and height sequence are generated, which serve as the direct basis for subsequent numerical simulation and engineering construction.

[0076] In one illustrative embodiment, the geometric parameters of the resonant cavity include cavity parameters disposed within the cavity of the resonant unit and opening parameters of the opening connecting the cavity to the external water body.

[0077] Determining the geometric parameters of the resonant cavity of the resonant unit based on the target wave frequency includes: determining the target value of the natural resonant frequency of the resonant cavity based on the target wave frequency corresponding to the resonant unit; and determining the cavity parameters and opening parameters based on the natural resonant frequency to match the natural resonant frequency determined by the opening parameters and cavity parameters with the target value.

[0078] According to an embodiment of the present invention, the cavity parameters include the depth or volume of the cavity, and the opening parameters include the equivalent area of ​​the opening.

[0079] According to embodiments of the present invention, the specific geometric dimensions of the cavity can be determined based on the principles of the Helmholtz resonator or tube resonance. By continuously adjusting the cavity parameters and opening parameters, the natural frequency of the resonant cavity can be made to continuously approach the target frequency corresponding to the resonant unit.

[0080] According to embodiments of the present invention, for resonant units located at the front (corresponding to high-frequency waves), a smaller opening area or a shallower cavity depth is designed; for resonant units located at the rear (corresponding to low-frequency long waves), a larger cavity depth is designed or the porosity of the opening is adjusted to match the lower resonant frequency. This structural design ensures that when long waves are guided deep into the array, they are not only physically blocked but also efficiently absorbed by the cavity coupled to their frequency.

[0081] In one illustrative embodiment, the Bragg resonance breakwater design method further includes: establishing a numerical calculation model for calculating the reflection coefficient within the target wave frequency band based on the arrangement parameters and the geometric parameters of the resonant cavity.

[0082] The reflection coefficient index is calculated using a numerical calculation model, and the value of the reflection coefficient index is compared with the preset design index.

[0083] If the value of the reflection coefficient does not meet the preset design specifications, the arrangement parameters and / or resonant cavity geometric parameters are iteratively adjusted until the value of the reflection coefficient meets the preset design specifications.

[0084] According to embodiments of the present invention, a numerical calculation model is first established based on the arrangement parameters and the geometric parameters of the resonant cavity. In some embodiments, the numerical calculation model may adopt a potential flow model or a boundary element model under linear wave theory, or a computational fluid dynamics model based on grid discretization; the numerical calculation model may also be a numerical wave flume model. The boundary conditions of the model may include at least one of wave incident boundary, wave-dissipating boundary, and solid wall boundary. The wave incident condition may be set as a single-frequency wave, a regular wave, or an irregular wave according to the target wave frequency band, and the water depth conditions corresponding to the target sea area may be set.

[0085] In some embodiments, adjusting the layout parameters and resonant cavity assembly parameters may include increasing, decreasing, or reassigning parameters such as horizontal spacing and submersion depth in the layout parameters, and correcting parameters such as the equivalent cavity volume, cavity depth, and equivalent opening area in the resonant cavity geometry parameters. This adjustment needs to be performed under preset constraints to ensure that the adjusted design remains feasible. In further embodiments, iterative adjustments may be implemented using search algorithms or optimization algorithms, such as gradient-based methods, heuristic search methods, or multi-objective optimization methods, to improve the efficiency of achieving preset design targets.

[0086] For example, a linear frequency domain potential flow calculation and analysis model can be built and run for rapid screening. The optimized arrangement parameters described above are then imported into the potential flow theory calculation software.

[0087] In the frequency domain, assuming the fluid is inviscid and the flow is irrotational, the wave scattering characteristics of the resonant unit array in the target wave frequency band are calculated to quickly verify the effectiveness of Bragg resonance and rainbow capture mechanism under potential flow theory, that is, to confirm whether the wave is reflected or slowed down at the expected spatial location, and to exclude those design schemes that cannot meet the reflectivity requirements in theory.

[0088] Construct a refined computational fluid dynamics (CFD) numerical model. For the selected preferred schemes, establish a two-dimensional or three-dimensional numerical wave tank that includes the overall layout of the resonant units and the fine features of the resonant cavities. The simulation area needs to cover the complete wave propagation path from the head to the tail of the array in order to fully capture the wave interference and resonance phenomena between multiple units.

[0089] The Navier-Stokes equations are discretized and solved using the finite volume method (FVM) to simulate the nonlinear motion of fluids. The fluid volume function method (VOF) is employed to capture the large deformation motion of the free surface, and a turbulence model (e.g., Model or A model was used to accurately calculate turbulent dissipation inside the cavity caused by fluid shearing and vortex shedding. Wave generator boundary conditions were set at the inlet boundary of the numerical flume to generate the target wave, and a wave-damping zone was set at the outlet boundary to eliminate the effects of secondary reflections.

[0090] The length of the wave-damping zone at the exit boundary is preset based on the maximum wavelength. For example, the length of the wave-damping zone can be set as follows: The wavelength corresponding to the extreme long-wave period of times.

[0091] Furthermore, the protective performance of the resonant unit array is quantitatively calculated based on the following formula for calculating the reflection coefficient: First, for discrete analog frequency points, calculate the single-frequency wave reflection coefficient: ; In the formula: For a specific frequency The reflection coefficient below; The amplitude of the separated reflected wave; The amplitude of the incident wave is given.

[0092] Furthermore, in order to evaluate the overall defensive effectiveness of the breakwater under actual sea conditions, the wave spectrum determined in Operation S210 was used as a reference. (Right now (frequency domain representation), calculate the energy-weighted average reflectance coefficient: ; In the formula: The energy-weighted average reflectance coefficient; The wave spectrum energy density function for the target sea area; These are the lower and upper limits of the dominant frequency range of the incident wave defined in step S1.

[0093] The energy-weighted average reflectance coefficient calculated above This is the final reflection coefficient index used to evaluate the overall protective performance of the breakwater array and determine whether it meets the design expectations.

[0094] In numerical simulation, stability refers to the state where the wave propagates to the exit boundary and the waveform repeats periodically. The determination time is preset based on the wave propagation speed. For example, the determination time can be set to the time required for the wave to propagate from the wave-generating boundary to the wave-dissipating boundary. times.

[0095] The local flow field mechanism was analyzed. In CFD post-processing, velocity vector maps and pressure contour maps at different times were extracted. Two key physical phenomena were verified: first, the slow-wave effect, i.e., observing whether wave energy is located at the resonant unit position corresponding to its frequency (based on spacing). The first phenomenon is the decrease in group velocity and the local amplification of wave height; the second is turbulent dissipation, that is, observing whether high-intensity turbulent vortices are generated inside the velocity-sensitive energy dissipation cavity at the energy accumulation point.

[0096] If the simulation results show an increase in turbulent kinetic energy (TKE) within the cavity, it proves that the local energy dissipation mechanism has been effectively activated. If the reflection coefficient... If the design specifications are met within a wide frequency band, the design scheme is deemed to have passed numerical verification.

[0097] In one illustrative embodiment, the Bragg resonant breakwater design method further includes: constructing a physical model based on the layout parameters and resonant cavity geometric parameters, and conducting a flue test. During the flue test, the reflection coefficient value within the target wave frequency band is measured, and the measured value is compared with a preset design parameter. If the measured value does not meet the preset design parameter, the layout parameters and / or resonant cavity geometric parameters are iteratively adjusted until the reflection coefficient value meets the preset design parameter.

[0098] For example, based on numerical simulation verification, the design parameters are further verified through physical model experiments to correct deviations caused by numerical model simplification (such as turbulence model assumptions), and finally the precise parameters required for engineering implementation are determined.

[0099] Using a laboratory wave tank environment, the designed breakwater array was physically reproduced and its hydrodynamic performance was tested. The specific steps included: Construct a physical model of the entity. Determine the geometric scale of the model based on the gravitational similarity criterion (i.e., the principle of equal Froude numbers). Based on the parameter combinations output from the numerical simulation above, multiple resonance unit models of different sizes were fabricated.

[0100] The model is made of concrete, plexiglass, or high-density wood to ensure that the surface roughness of the model is similar to that of the prototype or meets the requirements for hydraulic smoothness.

[0101] The horizontal spacing is determined strictly according to the formula for calculating the horizontal spacing of the resonant units. The submersion depth of the resonant unit determines the physical height of the resonant unit. The resonant unit model was then fixed to the bottom plate of the water tank.

[0102] Meanwhile, a resonant cavity is precisely machined inside each resonant unit model to ensure that the cavity parameters and opening parameters of the resonant cavity meet the geometric similarity ratio.

[0103] Set up the testing instruments and perform wave loading. Construct a Bragg breakwater in the effective testing area of ​​the wave-generating flume. Place wave height meter arrays (e.g., capacitive or resistive wave height meters) on the wave-facing and wave-repellent sides of each resonant unit in the model to synchronously acquire wave surface wave data.

[0104] The wave generator was started to produce regular wave sequences and irregular wave spectra based on the acquired wave field characteristic parameters. The test conditions covered different water level conditions (corresponding to tidal changes) and different wave height conditions to comprehensively examine the array's response stability under complex sea conditions.

[0105] Wavefront time history curves at each measuring point were recorded using a data acquisition system. Wavefront data on the wave-facing side were processed using reflected wave separation methods (e.g., two-point or multi-point methods) to separate the incident wave amplitude. and reflected wave amplitude The measured reflection coefficient is then calculated again using the formula for calculating the reflection coefficient. .

[0106] Meanwhile, the flow field structure near the resonant cavity was observed using particle image velocimetry (PIV) or dye tracer methods to confirm whether there was obvious dye diffusion or vortex shedding at the resonant frequency point, in order to verify the actual effectiveness of the local energy dissipation mechanism.

[0107] Compare the reflection coefficient curves obtained from physical experiments with the numerical simulation results. If the experimental results show that the reflectivity in the low-frequency band is lower than the design expectation (e.g., excessive long-wave transmission), then increase the immersion depth reduction factor. This involves raising the height of the resonant units at the rear of the array in the physical model to enhance physical blocking; if experimental results show insufficient effective defense bandwidth or the presence of reflectivity troughs (transmission windows) within the bandwidth, then the spacing increment is adjusted. This involves changing the spacing of the models in the water tank to optimize the spatial resolution of rainbow capture.

[0108] Adjustments were made iteratively until the measured broadband defense performance met the engineering design requirements.

[0109] In one illustrative embodiment, determining the target wave frequency of each resonant unit based on the target wave frequency band includes: dividing the target wave frequency band into multiple sub-bands; establishing a correspondence between each sub-band and the arrangement order of the resonant units according to the incident wave propagation direction; and determining the representative frequency of each sub-band as the target wave frequency of its corresponding resonant unit based on the correspondence.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing a Bragg resonance breakwater, the breakwater comprising multiple resonant units arranged in an array along the direction of incident wave propagation, characterized in that, include: Obtain the wave field characteristic parameters of the target sea area, and determine the target wave frequency band based on the wave field characteristic parameters; The target wave frequency of each of the resonant units is determined based on the target wave frequency band, and the geometric parameters of the resonant cavity of the resonant unit are determined according to the target wave frequency so that the inherent resonant frequency of the resonant cavity matches the target wave frequency. Based on the target wave frequency band, a reflection coefficient index is determined to characterize the wave dissipation effect. Under the premise of satisfying the preset constraints, the arrangement parameters of each of the resonant units are determined according to the reflection coefficient index. The arrangement parameters change step by step along the propagation direction of the incident wave. Output the resonant cavity geometric parameters and the arrangement parameters corresponding to each resonant unit to form the design scheme of the Bragg resonant breakwater.

2. The Bragg resonance breakwater design method according to claim 1, characterized in that, The determination of the arrangement parameters of each resonant unit based on the reflection coefficient index includes: Determine the horizontal spacing between adjacent resonant units; and Determine the submersion depth of each of the resonant units.

3. The Bragg resonance breakwater design method according to claim 2, characterized in that, Determining the horizontal spacing between adjacent resonant units includes: The initial spacing is determined by defining the horizontal distance between the first pair of adjacent resonant units located on the starting side of the incident wave propagation direction as the initial spacing. Determine the spacing increment that gradually increases the horizontal spacing between adjacent resonant units along the direction of the incident wave propagation; Based on the initial spacing and the spacing increment, the horizontal spacing between adjacent resonant units is determined sequentially according to the arrangement order of the resonant units.

4. The Bragg resonance breakwater design method according to claim 3, characterized in that, Determining the flooding depth of each of the resonant units includes: The initial flooding depth is determined by defining the flooding depth of the resonant element located on the starting side of the incident wave propagation direction. Determine the amount of inundation depth variation used to characterize the gradual decrease in inundation depth along the propagation direction of the incident wave; Based on the initial flooding depth and the change in flooding depth, the flooding depth of each resonant unit is determined sequentially according to the arrangement order of the resonant units.

5. The Bragg resonance breakwater design method according to claim 4, characterized in that, The determination of the arrangement parameters of each resonant unit based on the reflection coefficient index includes: Using the maximization of the reflection coefficient as the objective function, the initial spacing, the spacing increment, the initial flooding depth, and the change in flooding depth are iteratively solved under the preset constraints to optimize the layout parameters.

6. The Bragg resonance breakwater design method according to claim 1, characterized in that, The geometric parameters of the resonant cavity include the cavity parameters of the cavity disposed inside the resonant unit and the opening parameters of the opening connecting the cavity to the external water body. Determining the geometric parameters of the resonant cavity of the resonant unit based on the target wave frequency includes: The target value of the inherent resonant frequency of the resonant cavity is determined based on the target wave frequency corresponding to the resonant unit. The cavity parameters and opening parameters are determined based on the inherent resonant frequency, so that the inherent resonant frequency determined by the opening parameters and the cavity parameters matches the target value.

7. The Bragg resonance breakwater design method according to claim 1, characterized in that, Also includes: Based on the arrangement parameters and the resonant cavity geometric parameters, a numerical calculation model is established for calculating the reflection coefficient within the target wave frequency band; The value of the reflection coefficient index is calculated using the numerical calculation model, and the value of the reflection coefficient index is compared with the preset design index. If the value of the reflection coefficient index does not meet the preset design index, the arrangement parameters and / or the resonant cavity geometric parameters are iteratively adjusted until the value of the reflection coefficient index meets the preset design index.

8. The Bragg resonance breakwater design method according to claim 1 or 7, characterized in that, Also includes: A solid model was constructed based on the arrangement parameters and the resonant cavity geometric parameters, and a water tank test was conducted. In the water tank test, the reflection coefficient index value within the target wave frequency band is measured, and the measured value is compared with the preset design index. If the measured values ​​do not meet the preset design specifications, the arrangement parameters and / or the resonant cavity geometric parameters are iteratively adjusted until the value of the reflection coefficient meets the preset design specifications.

9. The Bragg resonance breakwater design method according to claim 1, characterized in that, The step of determining the target wave frequency of each of the resonant units based on the target wave frequency band includes: The target wave frequency band is divided into multiple sub-frequency bands; Establish a correspondence between each of the sub-frequency bands and the arrangement order of the resonant units according to the direction of incident wave propagation; and Based on the aforementioned correspondence, the representative frequency of the sub-band is determined as the target wave frequency of the corresponding resonant unit.

10. A Bragg resonance breakwater, characterized in that it comprises: Multiple resonant units are arranged in an array along the propagation direction of the incident wave, and the arrangement parameters of each resonant unit change step by step along the propagation direction of the incident wave. The resonant unit includes a resonant cavity, which includes an internal cavity and an opening connecting the cavity to external water. The cavity parameters and the opening parameters together determine the inherent resonant frequency of the resonant cavity that matches the target frequency corresponding to the resonant unit.

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