A method for evaluating corals' tolerance to island and reef hydrodynamics

Abstract

This invention relates to the technical field of coral tolerance and discloses a method for assessing the ability of corals to withstand the hydrodynamic forces of islands and reefs. The method comprises: preparing a bionic coral model based on the morphological characteristics of a target coral species; simulating different waves in a large-scale wave flume to measure wave height, flow velocity, and stress data of the bionic coral model at different locations on the reef flat; establishing a critical wave height-flow velocity-stress threshold curve for damage to the target coral species based on the wave height, flow velocity, and stress data; and assessing the tolerance of the target coral species based on this critical wave height-flow velocity-stress threshold curve. This approach can provide a research method for studying the tolerance of corals to wave-induced seawater flow in real island and reef terrain, offering a theoretical basis for coral ecological protection and a reliable technical means for the sustainable management of island and reef ecosystems.

Description

Technical Field

[0001] The present invention belongs to the technical field of coral tolerance, and in particular relates to a method for evaluating the tolerance of corals to island and reef hydrodynamics. Background Art

[0002] Coral reef ecosystems are important carriers of marine biodiversity and a key barrier to island and reef ecological protection. Currently, methods for assessing coral tolerance to hydrodynamic environments rely primarily on field observations, simplified laboratory model experiments, and numerical simulations, but these methods still have significant shortcomings in terms of technical approaches and application effectiveness.

[0003] In existing technologies, field observation methods can reflect the real environmental response by long-term monitoring of the correlation between physical damage to corals and wave parameters in natural environments. However, they are limited by the long observation period, uncontrollable environmental variables, and high data acquisition costs, making it difficult to systematically reveal the dynamic coupling mechanism between coral morphological characteristics and hydrodynamic parameters. Laboratory studies often use regular geometric bodies (such as cylinders and cubes) to simulate coral monomers and test their hydrodynamic responses in small water tanks. However, such simplified models cannot truly reproduce the complex morphology of coral branching structures and their nonlinear responses to vortexes and shear stresses, resulting in significant deviations between experimental results and actual coral damage thresholds. Numerical simulation technology can predict the flow field distribution around corals by establishing a fluid-structure interaction model, but its accuracy is highly dependent on boundary condition settings and material parameter assumptions. In particular, the mechanical properties of the porous skeleton of corals are overly simplified, making it difficult to accurately quantify the stress accumulation effect of biological materials under dynamic loads.

[0004] In addition, existing methods generally have the following technical bottlenecks: (1) There is a lack of systematic research on the coupling mechanism between coral morphological characteristics and multiple parameters of the hydrodynamic environment (wave height, flow velocity, stress), resulting in a single evaluation dimension; (2) There is no critical damage threshold curve based on biomechanical properties, which cannot provide a quantitative decision-making basis for coral ecological restoration; (3) The traditional physical model lacks geometric similarity with real corals, making it difficult to effectively extrapolate experimental data to complex island and reef terrain scenarios. These problems seriously restrict the scientific assessment of coral tolerance and make the formulation of ecological protection strategies lack accurate theoretical support.

[0005] Therefore, there is an urgent need to develop an evaluation method that integrates bionic model construction, high-precision environmental simulation and multi-parameter threshold judgment to break through the limitations of existing technologies and provide reliable technical means for the sustainable management of island reef ecosystems. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for evaluating the tolerance of corals to the hydrodynamics of islands and reefs, which can provide a research method for the tolerance of corals to the flow of seawater caused by waves under real island and reef terrain, provide a theoretical basis for coral ecological protection, and provide reliable technical means for the sustainable management of island and reef ecosystems.

[0007] The present invention provides a method for evaluating the ability of corals to tolerate hydrodynamic forces on islands and reefs, the method comprising the following steps:

[0008] S1. Prepare a bionic coral model based on the morphological characteristics of the target coral species;

[0009] S2. Use a large-scale wave flume to simulate different waves and measure wave height, flow velocity, and stress data of the bionic coral model at different locations on the reef flat;

[0010] S3. Establishing a critical wave height-flow velocity-stress threshold curve for damage to target coral species based on wave height, flow velocity, and stress data;

[0011] S4. Evaluate the tolerance of target coral species based on the critical wave height-flow velocity-stress threshold curve for damage to target coral species.

[0012] Furthermore, in S1, preparing a bionic coral model based on the morphological characteristics of the target coral species includes:

[0013] S11. determining an overall shape index and a branching shape index of the target coral species based on the morphological characteristics of the target coral species;

[0014] S12. Establish a generalized model based on the overall shape index, branching shape index, and target modeling height of the target coral species;

[0015] S13. Determine the preparation materials based on the generalized model, and prepare the bionic coral model to be tested by 3D printing;

[0016] S14, performing a mechanical property test on the bionic coral model to be tested to obtain a mechanical property test result;

[0017] S15. comparing the mechanical property test results with the actual values ​​of the mechanical properties of the target coral species;

[0018] If the error between the mechanical property test result and the true value of the mechanical property is within the preset error range, the bionic coral model to be tested is used as the final bionic coral model; otherwise, the preparation material is adjusted and S13-S15 are executed again.

[0019] Furthermore, in S11, the overall shape index is the ratio of the projection height to the projection width, and the branch shape index is the ratio of the branch length to the branch diameter.

[0020] Furthermore, in S14, a mechanical property test is performed on the bionic coral model to be tested, and the obtained mechanical property test results include:

[0021] The bone strength of the bionic coral model to be tested was measured to obtain the elastic modulus, compressive strength and critical stress intensity factor;

[0022] The matrix strength of the bionic coral model to be tested was measured to obtain the matrix bonding strength.

[0023] Furthermore, in S2, different waves were simulated in a large-scale wave tank to measure the wave height, flow velocity, and stress data of the bionic coral model at different locations on the reef flat, including:

[0024] S21. Place the bionic coral model at different locations on the reef flat in a large-scale wave tank to simulate different wave conditions for testing.

[0025] S22. During the test, the flow velocity distribution, wave surface elevation, and stress time history curve of the bionic coral model at different locations on the reef flat are recorded in real time. The test ends when the bionic coral model is damaged.

[0026] Among them, the damage to the bionic coral model included matrix removal and branch breakage.

[0027] Furthermore, in S22, when the base shear stress of the bionic coral model is greater than or equal to the matrix bonding strength, it is determined that the matrix is ​​removed;

[0028] When the stress intensity factor of the bionic coral model is greater than or equal to the critical stress intensity factor, it is determined to be a branch fracture.

[0029] Furthermore, in S3, the critical wave height-flow velocity-stress threshold curve for damage to the target coral species is established based on wave height, flow velocity, and stress data, including:

[0030] S31. Determine the morphological parameter function through multiple regression and establish the wave height-current velocity threshold equation for the destruction of target coral species;

[0031] The equation expression is as follows:

[0032] H0=f(U0,a,b,c);

[0033] Where H0 represents the critical wave height, U0 represents the critical flow velocity, and a, b, and c represent the morphological parameter functions;

[0034] S32. Draw the tolerance envelope of the target coral species based on the wave height-current threshold equation;

[0035] S33, performing low-pass filtering on the stress time history curve to obtain the maximum principal stress;

[0036] S34. Calculate the stress coefficient based on the maximum principal stress;

[0037] S35. Establish a correlation equation between the stress coefficient, wave height, and flow velocity, and obtain a critical wave height-flow velocity-stress threshold curve for damage to the target coral species.

[0038] Furthermore, in S34, the stress coefficient is calculated based on the maximum principal stress, and the calculation formula is as follows:

[0039] ;

[0040] Among them, C σ represents the stress coefficient, σ max represents the maximum principal stress, ρ w represents water density and U represents flow velocity.

[0041] The embodiments of the present invention have the following technical effects:

[0042] This scheme prepares a bionic coral model by defining the overall shape index and the branch shape index, and ensures that the mechanical response of the model is consistent with that of real corals through iterative optimization of mechanical properties; simulates the real reef flat topography in a large-scale wave tank, and simultaneously collects wave height, flow velocity, and stress time-history curves. Through low-pass filtering and defining dimensionless stress coefficients, a three-dimensional correlation equation of wave height-flow velocity-stress is established. By quantifying the dynamic coupling relationship between the combined action of waves and flows and the internal stress response of corals, the coral tolerance mechanism of wave-induced flows under real topography is revealed. It can provide a research method for the tolerance of corals to wave-induced seawater flow under real island and reef topography, provide a theoretical basis for coral ecological protection, and provide reliable technical means for the sustainable management of island and reef ecosystems. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 This is a flow chart of a method for evaluating the ability of corals to tolerate hydrodynamic forces on islands and reefs, provided by an embodiment of the present invention;

[0045] Figure 2 This is a generalized schematic diagram of a Staghorn coral provided by an embodiment of the present invention; Figure 2 (a) is a schematic diagram of the prototype coral of Acropora, Figure 2 (b) is a generalized coral diagram of Acropora;

[0046] Figure 3 This is a schematic diagram of the layout of a coral wave and current tolerance test model provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0048] The embodiment of the present invention provides a method for evaluating the ability of corals to withstand the hydrodynamic forces of islands and reefs. Figure 1 This is a flow chart of a method for evaluating the ability of corals to withstand hydrodynamic forces on islands and reefs, provided by an embodiment of the present invention. Figure 1 , the method comprises the following steps:

[0049] S1. Prepare a bionic coral model based on the morphological characteristics of the target coral species.

[0050] In some embodiments, S1 specifically includes the following sub-steps:

[0051] S11. Determine an overall shape index and a branching shape index of the target coral species based on the morphological characteristics of the target coral species.

[0052] S12. Establish a generalized model based on the overall shape index, branching shape index, and target modeling height of the target coral species.

[0053] In this example, Acropora was used as the target coral species, and the morphological data of Acropora was analyzed. The precise morphological data of the coral was obtained using 3D scanning technology, and the overall shape index I was selected. g (Projection height H c With projection width W c The ratio of ) is 1:3, 1:1 and 3:1, and the branch shape index I b (Branch length L c and branch diameter D c The study was conducted on Acropora with a ratio of 8:1, 5:1, 3:1 and 1:1. The coral model was generalized to a height of 20 cm. Figure 2 This is a schematic diagram of a generalized staghorn coral provided by an embodiment of the present invention. The generalized morphology of staghorn coral is as follows Figure 2 As shown, Figure 2 (a) is a schematic diagram of the prototype coral of Acropora, Figure 2 (b) is a schematic diagram of the generalized coral of Acropora, Figure 2The overall morphological index of the generalized Acropora in (b) is 1:1, and the branching indices are 8:1, 5:1, 3:1, and 1:1.

[0054] S13. Determine the preparation materials based on the generalized model, and prepare the bionic coral model to be tested by 3D printing.

[0055] In some embodiments, the prepared material can use a light-curable resin to simulate the coral skeleton, and a coral sand-epoxy resin composite material to simulate the coral matrix.

[0056] S14. Perform a mechanical property test on the bionic coral model to be tested to obtain a mechanical property test result.

[0057] In some embodiments, the bone strength of the bionic coral model to be tested is measured, and the bone strength measurement includes:

[0058] Uniaxial compression test: The loading rate of the testing machine indenter is 0.5 mm / min, the stress-strain curve is recorded, and the elastic modulus E and compressive strength σ are calculated. bc .

[0059] Fracture toughness test: Use three-point bending method to calculate the critical stress intensity factor K IC .

[0060] The substrate strength of the bionic coral model to be tested is tested. The substrate strength test includes:

[0061] Simulate the intertidal environment (temperature 25-30°C, salinity 30-35‰, pH 7.8-8.2), set up a dry-wet cycle (immersion / exposure every 6 hours), and perform a shear test after 28 days to measure the substrate bond strength τ max =F / A, where F is the applied shear force and A is the projected area of ​​the matrix.

[0062] S15. Compare the mechanical property test results with the actual values ​​of the mechanical properties of the target coral species.

[0063] In some embodiments, the true values ​​of the coral elastic modulus, compressive strength, and matrix bonding strength are calculated through data research combined with previous field test data and determined through ultimate destructive testing. If the error between the mechanical property test results and the true values ​​of the mechanical properties is within a preset error range, the tested bionic coral model is used as the final bionic coral model; otherwise, the prepared materials are adjusted and steps S13-S15 are repeated; the preset error range may be 5%.

[0064] S2. Use a large-scale wave tank to simulate different waves and measure the wave height, flow velocity, and stress data of the bionic coral model at different locations on the reef flat.

[0065] S21. The bionic coral model was placed at different locations on the reef flat in a large-scale wave tank to simulate different wave conditions for testing.

[0066] Figure 3 This is a schematic diagram of the layout of a coral wave and current tolerance test model provided by an embodiment of the present invention, see Figure 3 First, the island and reef terrain is generalized using a 1:8 model scale. The model and instrument layout are as follows: Figure 3 The model is 5m wide and 40m long. The foreslope slope is designed as a 1:1 composite slope. The distance between the toe of the steep reef slope and the wave generator is 330m. Regular waves are used for wave simulation. Wave parameters are designed based on extreme waves with different return periods. Wave heights range from 4m to 12m, and periods range from 8 to 14s. The reef flat water depth is 0-3m, and the distance between corals and the reef edge ranges from 0 to 300m. The main experimental parameters are shown in Table 1.

[0067] Table 1 Test parameters

[0068]

[0069] The bionic coral models are arranged at locations such as the reef edge, reef crown, outer reef flat and inner reef flat.

[0070] S22. During the test, the flow velocity distribution, wave surface elevation, and stress time history curve of the bionic coral model under the action of waves and currents at different locations on the reef flat are recorded in real time. The test ends when the bionic coral model is destroyed.

[0071] In some embodiments, an ADV current meter (accuracy ±1%) and a wave height meter are used to obtain the current velocity distribution (U(z)) and wave surface elevation (η(t)) at different locations on the reef flat.

[0072] Micro dynamic strain gauges (sampling frequency f=1000Hz) were embedded in the branches and roots of the bionic coral model to synchronously record the stress time history curve (σ(t)) under the action of waves and currents, and a high-definition camera system was used to observe the changes in coral morphology in real time.

[0073] Among them, the damage to the bionic coral model includes substrate removal and branch breakage:

[0074] When the base shear stress of the bionic coral model is greater than or equal to the matrix bonding strength (τ ≥ τ max ), it was determined to be matrix removal;

[0075] When the stress intensity factor of the bionic coral model is greater than or equal to the critical stress intensity factor (K I ≥K IC ), it is judged as a branch break.

[0076] S3. Establish a critical wave height-flow velocity-stress threshold curve for damage to the target coral species based on wave height, flow velocity, and stress data.

[0077] In some embodiments, S3 includes the following sub-steps:

[0078] S31. Determine the morphological parameter function through multivariate regression and establish the wave height-velocity threshold equation for damage to the target coral species.

[0079] In some embodiments, the equation is expressed as follows:

[0080] H0=f(U0,a,b,c);

[0081] In some embodiments, f(U0,a,b,c)=a×U0 b +c;

[0082] Among them, H0 represents the critical wave height (i.e., the wave height corresponding to the damage of the target coral species), U0 represents the critical flow velocity (i.e., the water velocity corresponding to the damage of the target coral species), a, b, and c represent morphological parameter functions, which are related to the geometric characteristics of the target coral species and reflect the differences in the damage resistance of different coral structures. Experimental data can be substituted into the equation, and the specific expressions of a, b, and c can be fitted through statistical methods (such as the least squares method).

[0083] S32. Draw the tolerance envelope of the target coral species based on the wave height-current threshold equation.

[0084] In some embodiments, the fitted equation is visualized in the HU coordinate system to form a dividing line, where the area below the envelope is a safe zone (corals are not damaged) and the area above the envelope is a dangerous zone (corals may be damaged).

[0085] S33. Perform low-pass filtering on the stress time history curve to obtain the maximum principal stress.

[0086] In some embodiments, the stress time history curve σ(t) is low-pass filtered (cut-off frequency fc = 50 Hz) to extract the maximum principal stress σ max .

[0087] S34. Calculate the stress coefficient based on the maximum principal stress.

[0088] In some embodiments, the stress coefficient is calculated as follows:

[0089] ;

[0090] Among them, C σ represents the stress coefficient, σ max represents the maximum principal stress, ρ w represents water density and U represents flow velocity.

[0091] S35. Establish a correlation equation between the stress coefficient, wave height, and flow velocity, and obtain a critical wave height-flow velocity-stress threshold curve for damage to the target coral species.

[0092] Since the stress on corals is caused by the combined action of waves and currents, its physical nature can be decomposed into:

[0093] Wave force contribution: Wave height H is transmitted to the coral structure through inertial force and drag force. The inertial force is positively correlated with wave height H.

[0094] Contribution of water flow force: The drag force generated by the flow velocity U is proportional to the square of the flow velocity;

[0095] Therefore, the internal stress of coral can be regarded as the relationship between H and U 2 The joint function, H / U 2 It comprehensively reflects the wave height (H) and flow velocity (U 2 ) is closer to the actual stress mechanism of corals, so the stress coefficient and H / U 2 The correlation equation of wave height, velocity and stress threshold curve for the destruction of target coral species was obtained.

[0096] S4. Evaluate the tolerance of target coral species based on the critical wave height-flow velocity-stress threshold curve for damage to target coral species.

[0097] This scheme prepares a bionic coral model by defining the overall shape index and the branch shape index, and ensures that the mechanical response of the model is consistent with that of real corals through iterative optimization of mechanical properties; simulates the real reef flat topography in a large-scale wave tank, and simultaneously collects wave height, flow velocity, and stress time-history curves. Through low-pass filtering and defining dimensionless stress coefficients, a three-dimensional correlation equation of wave height-flow velocity-stress is established. By quantifying the dynamic coupling relationship between the combined action of waves and flows and the internal stress response of corals, the coral tolerance mechanism of wave-induced flows under real topography is revealed. It can provide a research method for the tolerance of corals to wave-induced seawater flow under real island and reef topography, provide a theoretical basis for coral ecological protection, and provide reliable technical means for the sustainable management of island and reef ecosystems.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the ability of corals to withstand the hydrodynamic forces of islands and reefs, characterized in that: The method comprises the following steps: S1. Prepare a bionic coral model based on the morphological characteristics of the target coral species; Specifically include: S11. determining an overall shape index and a branching shape index of the target coral species based on morphological characteristics of the target coral species; The overall shape index is the ratio of the projected height to the projected width, and the branch shape index is the ratio of the branch length to the branch diameter; S12, establishing a generalized model according to the overall shape index, branching shape index, and target modeling height of the target coral species; S13. Determine the preparation material based on the generalized model, and prepare the bionic coral model to be tested by 3D printing; S14, performing a mechanical property test on the bionic coral model to be tested to obtain a mechanical property test result; S15. Comparing the mechanical property test result with the actual value of the mechanical property of the target coral species; If the error between the mechanical property test result and the true value of the mechanical property is within a preset error range, the bionic coral model to be tested is used as the final bionic coral model; otherwise, the preparation material is adjusted and S13-S15 are executed again; S2. Simulating different waves in a large-scale wave tank to measure wave height, flow velocity, and stress data of the bionic coral model at different locations on the reef flat; Specifically include: S21, placing the bionic coral model at different locations on the reef flat in a large-scale wave tank to simulate different wave conditions for testing; S22. During the test, the flow velocity distribution, wave surface elevation, and stress time history curve of the bionic coral model under the action of waves and currents at different locations on the reef flat are recorded in real time. The test ends when the bionic coral model is damaged. Wherein, the destruction of the bionic coral model includes matrix removal and branch breakage; When the base shear stress of the bionic coral model is greater than or equal to the matrix bonding strength, it is determined that the matrix is ​​removed; When the stress intensity factor of the bionic coral model is greater than or equal to the critical stress intensity factor, it is determined that the branch is broken; S3. establishing a critical wave height-flow velocity-stress threshold curve for damage to the target coral species based on the wave height, flow velocity, and stress data; S4. Evaluate the tolerance of the target coral species based on a critical wave height-flow velocity-stress threshold curve for damage to the target coral species.

2. The method for evaluating the hydrodynamic tolerance of corals to islands and reefs according to claim 1, wherein: In S14, a mechanical property test is performed on the bionic coral model to be tested, and the mechanical property test results obtained include: Performing bone strength measurement on the bionic coral model to be tested to obtain elastic modulus, compressive strength, and critical stress intensity factor; The matrix strength of the bionic coral model to be tested is measured to obtain the matrix bonding strength.

3. The method for evaluating the hydrodynamic tolerance of corals to islands and reefs according to claim 1, wherein: In S3, establishing a critical wave height-flow velocity-stress threshold curve for damage to the target coral species based on the wave height, flow velocity, and stress data includes: S31. Determine the morphological parameter function through multiple regression to establish a wave height-flow velocity threshold equation for damage to the target coral species; The equation expression is as follows: H0=f(U0,a,b,c); Where H0 represents the critical wave height, U0 represents the critical flow velocity, and a, b, and c represent the morphological parameter functions; S32. Draw a tolerance envelope of the target coral species according to a wave height-current velocity threshold equation; S33, performing low-pass filtering on the stress time history curve to obtain the maximum principal stress; S34, calculating a stress coefficient according to the maximum principal stress; S35. Establishing a correlation equation between the stress coefficient, wave height, and flow velocity to obtain a critical wave height-flow velocity-stress threshold curve for damage to the target coral species.

4. The method for evaluating the hydrodynamic tolerance of corals to islands and reefs according to claim 3, wherein: In S34, the stress coefficient is calculated according to the maximum principal stress, and the calculation formula is as follows: ； Among them, C σ represents the stress coefficient, σ max represents the maximum principal stress, ρ w represents water density and U represents flow velocity.

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