Multi-physical process dynamic simulation method for drifting and planting of sea grass seeds

Abstract

The invention discloses a multi-physical process dynamic simulation method for drifting and planting of sea grass seeds, and belongs to the field of drifting prediction of the sea grass seeds. The method comprises the following steps: a, determining environmental suitability conditions of the sea grass seeds, and judging whether the sea grass seeds survive or not; b, establishing a sea grass seed drifting planting model; the sea grass seeds which are not planted in the sea environment are affected by ocean current and turbulent flow disturbance in the movement process, and the sea grass seeds can settle due to the properties of the sea grass seeds in the movement process; for the planted sea grass seeds, the motion state of the sea grass seeds is not influenced by the marine environment due to the fact that the sea grass seeds are fused into the substrate; and c, performing multi-physical process dynamic simulation prediction on the sea grass seeds judged to survive by adopting the established sea grass seed drifting planting model. According to the method, the dynamic simulation precision of the sea grass seeds in a natural scene can be improved by establishing the multi-element coupled sea grass seed drift planting model and fusing the sea grass seed motion characteristics, the environment survival conditions and the substrate adaptability.

Description

Technical Field

[0001] This invention relates to the field of seagrass seed drift prediction, and more specifically to a dynamic simulation method for the multi-physical process of seagrass seed drift and colonization. Background Technology

[0002] Seagrass beds, as an important component of marine ecosystems, rely heavily on seeds produced by healthy seagrass beds for natural expansion and restoration. Their drifting and colonization process directly determines the distribution boundaries, ecological connectivity, and population continuity of seagrass beds. With the increasing demands for marine ecological protection, simulation of seagrass seed drifting and colonization can serve the technical needs of seagrass bed conservation, engineering compliance, and dynamic management.

[0003] Existing research lacks simulation studies of seagrass seed drift processes, focusing mostly on investigating the life history of seagrass seeds, including stages such as seed formation, dormancy, and germination. Regarding the drift and colonization process of seeds in the marine environment, existing studies mostly focus on the influence of single hydrodynamic factors on seed drift. While this can reflect the basic drift trend of seagrass seeds, it is difficult to simulate the actual movement trajectory of seagrass seeds. Summary of the Invention

[0004] Based on the above-mentioned technical problems, this invention proposes a dynamic simulation method for the multi-physical process of seagrass seed drift and colonization.

[0005] The technical solution adopted in this invention is: A dynamic simulation method for the multi-physical process of seagrass seed drift and colonization includes the following steps: a. Determine the environmental suitability conditions for seagrass seeds and determine whether the seagrass seeds can survive; b. Establish a seagrass seed drift and colonization model; The movement of unestablished seagrass seeds in the marine environment is affected by ocean currents and turbulence, and they may also sink due to their own properties during the movement process; however, for established seagrass seeds, since they have integrated into the seabed, their movement is not affected by the marine environment. The following is a model of seagrass seed drift and colonization in a marine environment: ; in, Let x, y, z be the displacement vector of the seaweed seed, and let x, y, z be the three-dimensional coordinates of the seaweed seed. Represents the velocity vector of ocean currents. , , Let u represent the unit vectors in the positive directions of the x, y, and z axes, respectively. c v c w c These represent the magnitudes of the ocean current velocities in the x, y, and z directions, respectively. u is the turbulent diffusion velocity vector. d v d w d These represent the magnitudes of the turbulent diffusion velocity in the x, y, and z directions, respectively; w s Indicates the settling velocity of seaweed seeds; c. For the seaweed seeds that were determined to be surviving in step a, the seaweed seed drift and colonization model established in step b was used to perform dynamic simulation and prediction of multiple physical processes.

[0006] The beneficial technical effects of the present invention are as follows: (1) By considering the influence of various environmental factors such as flow field, bottom sediment, temperature, salinity and water depth, this invention establishes a dynamic tracking method to simulate the drift and settlement process of seagrass seeds, fully restores the dynamic process of the entire life cycle of seeds from drifting, settling to settlement, realizes seed drift and diffusion path tracking and settlement area assessment, and can provide guidance for seagrass bed restoration, etc.

[0007] (2) By establishing a multi-element coupled seagrass seed drift and settlement model, this invention integrates the seagrass seed movement characteristics, environmental survival conditions and substrate adaptability, which can improve the dynamic simulation accuracy of seagrass seeds in natural scenarios. Attached Figure Description

[0008] Figure 1 This is a flowchart illustrating the dynamic simulation method for the multi-physical process of seagrass seed drift and colonization according to the present invention. Figure 2 This is a specific application example of the invention, showing the distribution of seagrass bed cover observed in a bay. Figure 3 This is a specific application example of the drifting and colonization of seagrass seeds in a bay. Detailed Implementation

[0009] Existing studies often analyze the impact of single hydrodynamic factors (such as tidal currents or ocean currents) on seed transport in isolation, failing to integrate the synergistic effects of disturbance on seed resuspension and sediment influence. Secondly, the dynamic interaction between seed biological characteristics and hydrodynamic parameters has not been effectively modeled, particularly lacking quantitative characterization of key parameters such as seed buoyancy changes and sediment anchoring efficiency. These deficiencies lead to significant discrepancies between existing simulation results and actual conditions. Furthermore, current technologies cannot accurately identify the core seed-producing areas of seagrass, making it impossible to establish protective measures for these areas. For example, in coastal engineering environmental impact assessments, the lack of simulation of the impact of engineering projects on natural seed diffusion corridors can easily lead to engineering projects blocking seed flow, ultimately resulting in seagrass bed fragmentation and shrinkage. Therefore, establishing simulation methods adapted to seagrass seed characteristics and integrating multiple physical processes can better serve the ecological restoration and protection of seagrass beds.

[0010] Based on this, this invention proposes a dynamic simulation method for the multi-physical processes of seagrass seed drift and colonization. This method considers the comprehensive influence of multiple physical processes, including flow field, the physical characteristics of seagrass seeds themselves, and substrate type. It refines key parameters such as seed buoyancy, settling velocity, and seed resuspension conditions, filling the current research gap in multi-factor coupled simulation and precise consideration of key parameters. This provides guidance for the natural restoration, ecological protection, and resource management of seagrass beds.

[0011] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0012] like Figure 1 As shown, a dynamic simulation method for the multi-physical process of seagrass seed drift and colonization includes the following steps: a. Determine the environmental suitability conditions for seagrass seeds and determine whether the seagrass seeds can survive.

[0013] The seagrass seed drift and colonization model first determines environmental suitability. Suitable seeds move under the influence of ocean currents and random disturbances. During the movement, the model determines whether the seeds will colonize or continue to move based on the conditions of settling or resuspension, and finally outputs the result of colonization or death.

[0014] The environmental suitability conditions for seagrass seeds are set as follows: ; Among them, f s T is a logical judgment function. w Let I be the water temperature, I be the light intensity, and h be the water depth.

[0015] Set environmental conditions when 10℃ ≤ T w ≤ 25℃, and the average water temperature over 3 days is ≤ 25℃; I ≥ 0.36I surface Seeds survive when h < 5 m, i.e., f s = 1, otherwise f s = 0, where I surface The intensity of sunlight on the sea surface.

[0016] b. Establish a seagrass seed drift and colonization model.

[0017] The movement of unestablished seagrass seeds in the marine environment is affected by ocean currents and turbulence, and they may also settle due to their own properties during movement. For established seagrass seeds, because they have integrated into the seabed, their movement is not affected by the marine environment. In summary, the movement speed of seagrass seeds in the marine environment can be expressed as: ; The above formula is the seagrass seed drift and settlement model. After calculating the drift position, the seed position is used to determine whether to settle or continue drifting.

[0018] in, Let x, y, z be the displacement vector of the seaweed seed, and let x, y, z be the three-dimensional coordinates of the seaweed seed. Represents the velocity vector of ocean currents. , , Let u represent the unit vectors in the positive directions of the x, y, and z axes, respectively. c v c w c These represent the magnitudes of the ocean current velocities in the x, y, and z directions, respectively. u is the turbulent diffusion velocity vector. d v d w d These represent the magnitudes of the turbulent diffusion velocity in the x, y, and z directions, respectively; w s This indicates the settling velocity of seagrass seeds, that is, the settling velocity caused by the inherent properties of seagrass seeds.

[0019] Turbulent diffusion velocity vector It is a random variable, and its components are calculated using the random walk method: ; Where R is a random number uniformly distributed in the interval [-1, 1]; Δt is the time step; K h K is the horizontal diffusion coefficient. z is the vertical diffusion coefficient.

[0020] Horizontal diffusion coefficient K h The calculation formula is as follows: ; Vertical diffusion coefficient K z The calculation formula is as follows: ; Where H is the significant wave height, e is the natural constant, k is the wave number, T is the wave period, and z is the vertical coordinate value (z = 0 at sea surface, z = h at seabed).

[0021] The settling velocity of seaweed seeds w s The calculation balances the resistance and buoyancy acting on the seed, and the formula is as follows: ; In the formula, Re p = μ w d / ρ w It is the Reynolds number of the seed, μ w = 10 −3 Pa·s is the dynamic viscosity of seawater, ρ w ρ is the density of seawater.s d represents the seed density, and d represents the seed diameter.

[0022] The seed resuspension condition is set such that the shear stress in the seed settling region is greater than or equal to 0.2 N / m. The shear stress can be expressed as: ; Among them, C f = 24 / Re p The drag coefficient, This indicates the magnitude of the ocean current velocity. If the seed meets the resuspension condition, the drift position prediction will be further performed by combining the seagrass seed velocity model in the marine environment from step b.

[0023] The planting time for seagrass seeds is related to the organic matter content (Lol) of the substrate, and the shear stress in the seagrass seed settling area must be less than 0.2 N / m. The formula for calculating the planting time of seagrass seeds is as follows: ; Among them, t s For the planting time of seagrass seeds; k s It is a constant related to the characteristics of seagrass seeds themselves, and is taken as 3.5 based on the results of field investigation experiments; L o This represents the percentage of organic matter contained in the substrate.

[0024] c. For the seaweed seeds that were determined to be surviving in step a, the seaweed seed drift and colonization model established in step b was used to perform dynamic simulation and prediction of multiple physical processes.

[0025] The invention will be further explained below with reference to specific application examples.

[0026] A field survey of seagrass beds was conducted in a bay. Shipborne radar was used to scan the seagrass beds within the bay, obtaining the seagrass bed cover distribution as shown below. Figure 2 As shown.

[0027] Environmental information of the study area was collected. The model input data used was the flow field data near the simulation area provided by the FVCOM model operated by the North China Sea Forecasting and Disaster Reduction Center of the Ministry of Natural Resources. The method of this invention was used for dynamic simulation.

[0028] By simulating the seagrass seeds in this bay, their drift and colonization can be obtained, such as... Figure 3 As shown in the simulation results, during high tide, seagrass seeds diffuse from the bay mouth into the bay with the northward current; during low tide, the seeds flow back towards the bay mouth with the southward current. However, due to the influence of local circulation and water depth within the bay, a temporary retention area forms in the central part of the bay. This drifting pattern corresponds to the distribution characteristics of the bay seagrass bed survey, where the seagrass cover is highest at the bay crest, followed by the central part, and lowest at the bay mouth. Figure 3As shown, the results are largely consistent, proving the rationality of the simulation method of this invention in predicting seed drift paths.

[0029] In summary, this invention, by integrating multiple factors such as flow field, seed characteristics, substrate properties, and environmental factors, reconstructs the dynamic process of the entire life cycle of seeds from drifting and settling to establishment / death, providing practical guidance for predicting changes in seagrass bed distribution areas, formulating seagrass bed protection strategies, and restoring seagrass beds. Specifically, this is reflected in the following aspects: (1) Natural seagrass bed protection plan: guide the delineation of core seed source areas, diffusion corridor protection zones, and potential planting reserve areas in protected areas, and prohibit destructive human activities; (2) Environmental impact assessment of coastal projects: quantify the blocking impact of the project on the diffusion corridor, optimize the project plan (such as adjusting the route of the waterway) or design ecological compensation measures; (3) Dynamic management of the protected area: annually simulate the natural seed drift and planting boundary, dynamically adjust the protected area, and avoid insufficient or excessive protection; (4) Passive restoration of damaged seagrass beds: assess the natural seed arrival rate and planting success rate in the damaged area to guide mild intervention measures (such as improving the organic matter content of the bottom substrate) and accelerate natural recovery; (5) Maintenance of cross-regional ecological connectivity: Identify cross-regional diffusion corridors of seagrass beds in different sea areas, formulate unified protection standards, and maintain population genetic diversity.

[0030] For any parts not mentioned above, existing technologies can be adopted or referenced.

[0031] Of course, the above description is only a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. It should be noted that any equivalent substitutions or obvious modifications made by those skilled in the art under the guidance of this specification fall within the scope of this specification and should be protected by the present invention.

Claims

1. A multi-physics dynamic simulation method for eelgrass seed dispersal colonization, characterized in that Comprising the following steps: a. Determine the environmental suitability conditions of seagrass seeds, and determine whether the seagrass seeds are alive; b. Establish a model of seagrass seed drift and colonization; For seagrass seeds that have not yet colonized, their movement in the marine environment is affected by ocean currents and turbulent disturbances, and they will also settle due to their own properties during the movement process; For colonized seagrass seeds, because they have integrated into the substrate, their movement state is not affected by the marine environment; The model of seagrass seed drift and colonization in the marine environment is as follows: ； wherein, is the displacement vector of the seagrass seed, x, y, z are the three-dimensional coordinates of the seagrass seed; represents the velocity vector of the sea current, , , respectively represent the unit vectors of the positive direction of the x, y, z axes, u c , v c , w c are the sea current velocity magnitudes in the x, y, z directions, respectively; is the turbulent diffusion velocity vector, u d , v d , w d are the turbulent diffusion velocity magnitudes in the x, y, z directions, respectively; w s represents the settling velocity of the seagrass seed; c. For the alive seagrass seeds determined in step a, use the model of seagrass seed drift and colonization established in step b to perform dynamic simulation and prediction of multiple physical processes.

2. The multi-physics dynamic simulation method of eelgrass seed drift colonization according to claim 1, wherein, In step a: The environmental suitability conditions of seagrass seeds are set as: ； where f s is a logical decision function, T w is water temperature, I is light intensity, and h is water depth. Set environmental conditions when 10°C ≤ T w ≤ 25°C, and 3-day average water temperature ≤ 25°C; I ≥ 0.36I surface , and h < 5 m, the seed survives, i.e. f s = 1, otherwise f s = 0, where I surface is the sea surface light intensity.

3. The multi-physics dynamic simulation method of eelgrass seed drift colonization according to claim 2, wherein, In step b: turbulent diffusion velocity vector is a random variable whose magnitude in the x, y, z directions is calculated using the random walk method: ； where R is a random number uniformly distributed in the interval [-1, 1]; At is the time step; K h is the horizontal diffusion coefficient; K z is the vertical diffusion coefficient.

4. The multi-physics dynamic simulation method of eel grass seed drift planting according to claim 3, wherein, Horizontal diffusion coefficient K h The formula for calculating K is as follows: ； Vertical diffusion coefficient K z The formula for calculating Kz is as follows: ； Where H is the significant wave height, e is the natural constant, k is the wave number, T is the wave period, and z is the vertical coordinate value.

5. The multi-physics dynamic simulation method of eel grass seed drift planting according to claim 4, wherein, In step b: The settling velocity w of the seed of the sea grass s The balance between the resistance and the buoyancy acting on the seed is calculated, and the calculation formula is as follows: ； where Re p = μ w d / ρ w is the Reynolds number of the seed, μ w = 10 −3 Pa·s is the dynamic viscosity of seawater, ρ w is the density of seawater, ρ s is the density of the seed, and d is the diameter of the seed.

6. The multi-physics dynamic simulation method of eel grass seed drift planting according to claim 5, wherein, In step b: The seed resuspension condition is set as the shear stress of the seed settling area being greater than or equal to a set threshold, and the shear stress is represented as: ； where C f = 24 / Re p is the drag coefficient, represents the current velocity magnitude; if the seed meets the resuspension condition, the seed will continue to drift location prediction with the drift and colonization model of the seagrass seed in step b.

7. The multi-physics dynamic simulation method of eel grass seed drift planting according to claim 6, wherein, In step b: The seagrass seed colonization time is related to the organic matter content of the substrate, and it also needs to satisfy the condition that the shear stress of the seagrass seed settling area is less than a set threshold, and the calculation formula of the seagrass seed colonization time is as follows: ； wherein t s is the planting time of the seagrass seeds; k s is a constant related to the properties of the seagrass seeds themselves; L o is the percentage of organic matter contained in the substrate.

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