Numerical simulation method of tailwater plume in deep sea mining based on ROMS model

Abstract

A numerical simulation method for deep-sea mining tailwater plume based on the ROMS model includes determining the research area, research time range, and ROMS model resolution; constructing a hydrodynamic model of the target sea area; determining the tailwater plume emission source parameters, including quantity, longitude and latitude, emission depth, emission flow, material type and its concentration; using these data, combined with hydrodynamic data, to solve the buoyancy plume model and obtain the initial conditions of the passive transport stage of the tailwater plume; using the initial conditions, constructing a tailwater plume transport model based on the hydrodynamic model, running the tailwater plume transport model and analyzing the results. The present invention provides a complete set of processes based on the ROMS model, which can achieve high-resolution and long-term simulation, and can set the deep-sea mining tailwater plume emission source at different depths. It is of great significance to understand the transport laws and mechanisms of tailwater plumes in deep-sea environments and determine the reasonable discharge depth of tailwater plumes.

Description

Technical Field

[0001] The invention relates to a deep-sea mining tail water plume numerical simulation method based on a ROMS model. The ROMS model is used to simulate the transport process of the deep-sea mining tail water plume in the ocean, and then the process of the deep-sea mining tail water plume in the environment is analyzed, belonging to the technical field of deep-sea mining. Background Art

[0002] The ocean is rich in mineral resources. In recent years, with the increasing scarcity of land resources and the increasing attention of mankind to marine resources, deep-sea mining has gradually become a hot spot for global mineral mining. In the process of deep-sea mining, the collected ore will be pre-processed on the surface operating ship, and then a large amount of mixture containing sediments, mineral debris, heavy metals and other substances will be discharged into the ocean. These mixtures are called deep-sea mining tailwater plumes (hereinafter referred to as tailwater plumes). It is generally believed that tailwater plumes will cause harm to the marine ecological environment. However, due to the limited understanding of the transport process of tailwater plumes in the ocean, it is currently difficult for people to correctly assess the harm caused by tailwater plumes to the ecological environment.

[0003] Common methods for studying the transport process of tailwater plumes include numerical simulation and field observation. The transport process of tailwater plumes in deep-sea environments is affected by multi-scale dynamic processes such as mesoscale vortices, internal waves, and ocean turbulent mixing. Accurately reflecting the evolution of tailwater plumes in deep-sea environments is a difficult problem for tailwater plumes. Field observations are usually carried out using acoustic equipment (CN118533937 A, 2024.08.23), optical equipment (CN 117740773 A, 2024.03.22), underwater robots (CN117572430 A, 2024.02.20), etc. Field observations have the advantage of obtaining real-time and accurate data. However, considering that deep-sea mining is affected by multi-scale dynamic processes in the ocean, it often has a complex three-dimensional structure and can spread over hundreds of kilometers in the ocean. Observations of such a process often require the use of multiple observation instruments and cost a lot of money. In addition, the diffusion of the tailwater plume occurs in the deep sea, so observations in the deep sea are also difficult and have high uncertainty.

[0004] Ocean numerical simulation can simulate multi-scale processes in the ocean well by discretizing the control equations that describe different processes in the ocean, and compared with observation methods, ocean numerical simulation is often less expensive. Ocean numerical simulation is an effective means to study the transport process of tailwater plumes. At present, many numerical models have been established for seabed mining vehicle plumes (Kuang Fangfang et al., 2024; Liu S,et al, 2024), but there is a lack of numerical simulation schemes for tailwater plumes. Compared with seabed mining vehicle plumes, the simulation of tailwater plumes usually needs to consider the influence of the heat transfer effect of the discharge pipe on the tailwater plume. Therefore, the model designed for the mining vehicle plume cannot be directly transferred to the simulation of the tailwater plume, and a new model must be designed for the tailwater plume.

[0005] The transport of tailwater plumes in the ocean can be divided into the discharge stage, the buoyancy-driven stage, and the passive transport stage. The first two stages belong to a small-scale fluid mechanics problem; the last stage is mainly affected by various dynamic processes such as ocean background currents and mesoscale eddies, and is a multi-scale physical oceanography problem. Accurate simulation of the first two stages usually requires the ocean model to have a higher resolution, which is usually difficult for ocean models because higher resolutions place higher demands on the amount of calculation and accuracy of the ocean model. However, to accurately simulate the passive transport stage, the discharge stage and the buoyancy-driven stage must be considered because they provide the initial conditions for the passive transport stage, which undoubtedly increases the difficulty of constructing a numerical model of the tailwater plume.

[0006] The ROMS (Regional Ocean Modeling System) model has the characteristics of open source model, diverse modules, high accuracy, and easy to use. It is currently widely used in hydrodynamics, sediment transport simulation, and marine ecosystem simulation in estuaries and offshore areas. These characteristics of the ROMS model, especially the good support of the ROMS model for marine ecosystem simulation, make the ROMS model a potential effective means of simulating tailwater plumes. However, there is currently no research on using the ROMS model to simulate tailwater plumes, so it is imperative to build a numerical model based on the ROMS model to simulate and analyze tailwater plumes.

[0007] Liu S, Yang J, Lyu H, et al. A numerical investigation of the effects of deep-sea mining vehicles on the evolution of sediment plumes based on the combination of near- and far-field models[J]. Applied Ocean Research, 2024,149: 104048;

[0008] Kuang, F.F., Zhang, J.P., Jing, C.S., et al. Numerical simulation of deep-sea mining plume diffusion in CC area[J]. Chinese Journal of Applied Oceanography, 2024, 43(3): 462–472. Summary of the invention

[0009] In view of the existing deficiencies, the present invention gives full play to the advantages of the ROMS model in the field of ocean numerical simulation and establishes a numerical simulation method for tailwater plumes of deep-sea mining based on the ROMS model to study the transport process and dynamic mechanism of tailwater plumes in the deep sea, providing a reference for environmental impact assessment of deep-sea mining.

[0010] To achieve the above technical objectives, the present invention provides a method for simulating deep-sea mining tailwater plume based on the ROMS model, comprising the following steps:

[0011] Step 1. Determine the study area, study time range, and ROMS model resolution;

[0012] Step 2. Collect topographic data, atmospheric data, and ocean hydrodynamic data for the study area and study period; the influence of tides on deep-sea processes is limited, so tidal data may not be collected;

[0013] Step 3. Generate a grid file using the acquired terrain data;

[0014] Step 4. Interpolate the obtained atmospheric data and ocean hydrodynamic data to the corresponding grid nodes to create atmospheric forcing files, initial field files, and boundary field files;

[0015] Step 5. Construct the hydrodynamic model of the target sea area based on the prepared grid file, atmospheric forcing file, initial field file, and boundary field file;

[0016] Step 6. Determine the tailwater plume emission source parameters, including quantity, longitude and latitude, discharge depth, discharge flow, substance type and its concentration;

[0017] Its characteristics include:

[0018] Step 7. Using the data from step 6 and combined with the hydrodynamic data, solve the buoyancy plume model to obtain the initial conditions of the passive transport stage of the tailwater plume;

[0019] Step 8. Using the results of step 7, build a tailwater plume transport model based on the hydrodynamic model of step 5, run the tailwater plume transport model and analyze the results.

[0020] Furthermore, in step 1, the model resolution includes horizontal resolution and vertical resolution. The ROMS model uses a staggered C grid horizontally and a terrain-following sigma coordinate vertically. The sigma coordinate is calculated by a vertical transformation equation and a vertical stretching function based on water depth, number of vertical layers, surface and bottom densification coefficients.

[0021] Furthermore, the atmospheric data in step 2 include 10m wind speed u component, 10m wind speed v component, 2m temperature, relative humidity, sea surface atmospheric pressure, rainfall, net longwave radiation flux, and net shortwave radiation flux; the ocean hydrodynamic data in step 2 include seawater flow velocity u component, seawater flow velocity v component, seawater temperature, seawater salinity, and sea surface height.

[0022] Furthermore, in step 3, if the terrain in the study area changes dramatically, the terrain in the grid file needs to be smoothed.

[0023] Furthermore, the steps for constructing the hydrodynamic model in step 5 are:

[0024] (1) Configure the environment required to run the ROMS model;

[0025] (2) Set the options used in the hydrodynamic model in the h file;

[0026] (3) In the roms.in file, set the number of horizontal grid nodes, number of vertical layers, number of computational nodes, horizontal and vertical difference formats, boundary conditions, computational time step, total computational step, vertical transformation equation, vertical stretching function, surface and bottom encryption coefficients, and input and output file locations.

[0027] Furthermore, the hydrodynamic data in step 7 may be provided by step 2 or by the hydrodynamic model established in step 5.

[0028] Furthermore, the steps for obtaining the initial conditions of the passive transport stage of the tailwater plume in step 7 are:

[0029] (1) Solve the temperature of the outlet under the effect of heat conduction:

[0030] ,

[0031] In the above formula, is the ambient water temperature, is the temperature in the drain pipe, depth.

[0032] (2) Calculate the tailwater density at the discharge port:

[0033] ,

[0034] In the above formula, is the density of the plume at the discharge outlet, and are the densities of sediment and water at the outlet, respectively, and are the volume flow rates of sediment and water at the outlet, respectively, The temperature and salinity at the outlet are calculated using the seawater state equation based on the salinity and (1).

[0035] The salinity may be provided in step 6, or the salinity of the sea surface may be used.

[0036] (3) Solve the discharge phase equation as the initial condition for the buoyancy driven phase:

[0037] First calculate the effective starting position of the plume :

[0038] ,

[0039] in, is the depth at the discharge port, is the length of the flow establishment zone, calculated by the following formula:

[0040] ,

[0041] In the above formula, is the radius at the discharge port, is the initial Froude number, where is the initial velocity at the discharge port, is the initial buoyancy at the discharge port, where is the acceleration due to gravity, is the density of the plume at the discharge outlet, is the background seawater density;

[0042] Then, calculate the effective radius, velocity, and buoyancy of the plume:

[0043] ,

[0044] ,

[0045] ,

[0046] In the above formula, is the effective radius of the plume, is the effective velocity of the plume, is the effective buoyancy of the plume, is the velocity and density distribution ratio, Calculated by the following formula:

[0047] .

[0048] (4) Calculate the buoyancy drive phase equation:

[0049] ,

[0050] ,

[0051] ,

[0052] ,

[0053] ,

[0054] in, is the volume flux of the plume, is the distance of the plume along the central axis, is the radius of the plume, is the vertical velocity at the plume midline, is the velocity at the plume centerline, is the corrected entrainment coefficient, and are the horizontal entrainment coefficient and the vertical entrainment coefficient, is the background velocity, , , satisfy , is the momentum flux of the plume, is the velocity and density distribution ratio, is the buoyancy flux of the plume, N is the buoyancy frequency, is the difference between the plume density and the background environment density, is the background seawater density, is the depth at the plume midline, is the horizontal distance from the plume centerline to the discharge point.

[0055] (5) Solve the initial conditions of the passive transport stage:

[0056] Typically, the plume is neutrally buoyant ( ) is transported outward from the neutral buoyancy point. In order to provide initial conditions for the passive transport stage of the ROMS model, it is necessary to solve the equation in (4) for the depth of the neutral buoyancy point of the plume: , and volume flux , and then calculate the concentration of the substance in the plume at the neutral buoyancy depth and plume flow :

[0057] ,

[0058] ,

[0059] In the above formula, Initial volume flux in the buoyancy-driven phase, is the initial concentration in the buoyancy-driven phase.

[0060] In addition, the temperature and salinity of the plume at the neutral buoyancy depth are required. Given that the plume is fully mixed with the background environment at the neutral buoyancy depth, it is reasonable to assume that the temperature and salinity of the plume are consistent with the surrounding environment.

[0061] Furthermore, the steps for constructing the tailwater plume model in step 8 are:

[0062] (1) Use the neutral buoyancy depth obtained in step 7 , plume flow , temperature, salinity and substance concentration , generate emission source files, where the substances in the emission sources include: viscous sediments and non-viscous sediments of various particle sizes and settling velocities, and various dissolved substances;

[0063] (2) Set the river_Vshape variable in the emission source file, setting the depth corresponding to the emission source to 1 and the other depths to 0, so that the emission source is located at the specified depth;

[0064] (3) Set LwSrc to T in the roms.in file and assign a value of 2 to the river_direction variable in the emission source file to make the flow direction of the emission source vertical;

[0065] (4) Add a sediment transport model or a dissolved matter transport model based on whether the matter in the tailwater plume is sediment or dissolved matter;

[0066] (5) If the substances in the tailwater plume are soluble substances, it is necessary to set the number of types of soluble substances in the roms.in file and set LtracerSrc to T to activate the transport of soluble substances in the emission source; if the substances in the tailwater plume are sedimentary substances, it is necessary to set the number of types of sedimentary substances in the roms.in file and write a sediment.in file to specify the particle size and sedimentation velocity of the sediment, and set SAND_Ltsrc / MUD_Ltsrc to T according to the type of sediment to activate the sediment transport in the emission source.

[0067] The beneficial effects of the present invention are as follows: based on the ROMS model, the present invention provides a complete set of processes from data download, model construction, and data analysis, which can achieve high-resolution and long-term simulation, and can set the deep-sea mining tail water plume emission source at different depths, and support the addition of a variety of sediments and soluble substances in the emission source. In view of the current limited research on deep-sea mining tail water plumes and the lack of a reasonable discharge depth, the present invention is of great significance for understanding the transport laws and mechanisms of tail water plumes in deep-sea environments and determining the reasonable discharge depth of tail water plumes. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 Flowchart of an embodiment of the present application.

[0069] Figure 2 Example study area and water depth.

[0070] Figure 3 Schematic diagram of the buoyancy plume model.

[0071] Figure 4 Comparison of model results with WOA 2023 annual average sea surface temperature and salinity.

[0072] Figure 5 Comparison of model results with WOA2023 annual average temperature and salinity changes with depth within 0-500m at the 10°N section.

[0073] Figure 6 Comparison of model results with the climatological mean HYCOM annual average sea surface flow field. DETAILED DESCRIPTION

[0074] The present invention provides a method for numerically simulating deep-sea mining tailwater plumes based on the ROMS model, which is specifically described below in conjunction with the accompanying drawings. The embodiment described below is carried out under the average forcing of the climatic state from 2006 to 2015 and only one type of sediment is simulated in the tailwater. Obviously, the described embodiment is only an example of the present invention, and the present invention can also be carried out in other ways.

[0075] As attached Figure 1 The embodiment shown includes the following steps:

[0076] S1: The study area of ​​this embodiment is 5°N~15°N, 160°W~150°W, which can cover the deep-sea mining contracted mining area of ​​China Minmetals Corporation in the eastern Pacific. In order to reflect the more general situation in this area, this example will run for one year under the climatological forcing. The horizontal resolution of the model is 1 / 20° (about 5km), and there are 50 Sigma layers in the vertical direction. In this example, the combination of Vtransform=2 and Vstretching=4 is selected to realize the calculation of Sigma coordinates. This combination can achieve refinement on the surface and bottom, and is independent of or weakly dependent on the terrain in the deep sea area. This combination has now become the default option of the ROMS model. We also highly recommend this solution for deep-sea mining. The vertical transformation equation corresponding to Vtransfrom=2 is:

[0077] ,

[0078] ,

[0079] ,

[0080] In the above formula, is a nonlinear transformation function defined by equation (2); is a free surface that changes with time; is the actual water depth; is the critical depth during vertical stretching. ; The vertical stretching coordinate is defined by equation (3), where N is the number of vertical layers, and in this example, N=50; is the vertical stretching function. The stretching function corresponding to Vstretching=4 is defined as a continuous stretching function:

[0081] ,

[0082] ,

[0083] In the above formula, and They are the surface density coefficient and the bottom density coefficient, and their valid value ranges are , , formula (5) is the result of the stretching transformation of formula (4) The secondary stretching is , .

[0084] S2: Download ETOPO2022 data to obtain the topographic data of the study area; download ERA5 data for the study area from 2006 to 2015, and calculate the climate state average to provide atmospheric data for the model; download HYCOM data for the study area from 2006 to 2015, and calculate the climate state average to provide ocean hydrodynamic data for the initial field and boundary field of the model.

[0085] In this embodiment, it is necessary to download the 10m wind speed, 2m temperature, 2m dew point temperature, sea surface pressure, total precipitation, net atmospheric longwave and shortwave radiation fluxes in the sea surface atmosphere from the ERA5 dataset; it is necessary to download the seawater flow velocity, seawater salinity, seawater temperature, and sea surface height from the HYCOM dataset.

[0086] S3: The CROCO_TOOLS toolkit in MATLAB was used to create a grid file. The water depth in the grid file was interpolated from the ETOPO2022 data to the ROMS grid nodes. The water depth in the study area of ​​this example changes dramatically. In order to ensure the stable operation of the model, terrain smoothing is required. The water depth after terrain smoothing in this example is shown in the attached figure. Figure 2 As shown. The smoothness of the terrain needs to be referenced and :

[0087] ,

[0088] ,

[0089] In the above formula It's only about the terrain. In addition to depending on the terrain, it is also related to the vertical coordinate transformation. Although some models can run on large and However, in general, the water depth in the grid file needs to meet , In this embodiment, terrain smoothing is achieved by using the matlab package LP_Bathymetry. The LP_Bathymetry package uses a linear programming method to perform terrain smoothing. It has excellent performance when performing terrain smoothing, and the terrain is smoothed to a preset and superior.

[0090] S4: Calculate the climatological average of ERA5 and HYCOM data from 2006 to 2015, and interpolate the climatological average ERA5 and HYCOM data to the ROMS grid nodes to create the atmospheric forcing file, initial field file, and boundary field file. The creation of each file needs to be combined with the hydrodynamic model configuration information. The creation methods of each file in this example are as follows:

[0091] In this example, the block formula is used to parameterize the interaction between the ocean and the atmosphere. The block formula needs to provide 10m wind speed, relative humidity, 2m temperature, sea surface atmospheric pressure, sea surface net shortwave radiation, sea surface net longwave radiation, and precipitation. Since the ERA5 dataset does not provide relative humidity, the relative humidity in this example is calculated from the 2m temperature and 2m dew point temperature:

[0092] ,

[0093] In the above formula, is the relative humidity, is the dew point temperature at 2m ( ) The actual water vapor pressure corresponding to is calculated as: , is the saturated water vapor pressure corresponding to the 2m temperature (T), and the calculation formula is: 。

[0094] The ROMS model in this example uses a cold start method, that is, the sea surface height, flow velocity, and sediment concentration in the initial field file are all set to 0, and the temperature and salinity are provided by linear interpolation of the HYCOM data averaged from 2006 to 2015. In the vertical direction, the valid data provided in the original data set of HYCOM is only up to 5000m, while the maximum water depth of the study area is close to 6000m. For this part of the data not provided by HYCOM, the nearest neighbor interpolation is used. The four boundaries of the model are all open boundaries. In this example, the temperature, salinity, and flow velocity use the clamped boundary conditions, and the sea surface height uses the Chapman boundary conditions. The boundary field file needs to provide the temperature, salinity, flow velocity, and sea surface height at the boundary, which are all provided by linear interpolation of the HYCOM data averaged by the climate state. For the data not provided by HYCOM in the vertical direction, the nearest neighbor interpolation is used.

[0095] S5: Construct a hydrodynamic model for the study area. The ROMS model version used in this example is 4.1, the Fortran compiler used is ifort, the parallel computing library is intelmpi, and the NETCDF library is NETCDF4 compiled by the interl compiler; the hydrodynamic model uses secondary bottom friction to calculate the bottom boundary layer, uses block formulas to parameterize the air-sea interaction, uses the KPP scheme to close the vertical turbulent mixing, and uses nonlinear state equations to calculate the thermodynamic properties of seawater; in the roms.in file, the number of horizontal grids of the hydrodynamic model is 199*203, the number of vertical Sigma layers is 50, the horizontal difference format of temperature and salinity is U3, the vertical difference format is C4, the time step dt is 60s, the running time is 1 year, the model instantaneous hydrodynamic variables are output every 1 hour, the average value of the hydrodynamic variables is calculated and output every 1 day, the vertical coordinate transformation combination is Vtransform = 2, Vstretching = 4, and the vertical surface encryption coefficient is , vertical bottom density coefficient , the critical depth of vertical densification TCLINE=350m.

[0096] S6: Determine the tailwater plume emission source information and solve Figure 3 In this example, the latitude and longitude of the tailwater discharge source are 10°N, 155°W. In order to explore the diffusion law and mechanism of the tailwater plume at different depths, the discharge source is placed at the surface, 1000m, 2000m, and 3000m, respectively. The initial radius of the discharge pipe is 0.25m, and the flow rate of the discharge source is 0.56 m 3 s -1 Only one type of sediment was considered among the emission sources, with a concentration of 8.3 kg m -3 , median particle size is 10 μm, sedimentation velocity is 0.1 mm s -1 , sediment density is 2680 kg m -3 The initial temperature and salinity of tailwater discharge are replaced by the sea surface temperature and salinity in HYCOM. , , , background flow rate u a is the flow velocity in the HYCOM data. The background density and background buoyancy frequency are calculated using the Gibbs-SeaWater toolkit from the temperature and salinity in the HYCOM data set. Under the above emission source conditions, the fourth-order Runge-Kutta method is used to numerically solve the buoyancy plume model, and the depth, flow rate, temperature, salinity and material concentration of the plume at neutral buoyancy are obtained as the initial conditions of the tailwater plume transport model.

[0097] S7: Add tailwater plume emission source to the regional hydrodynamic model constructed in S5, build and run the tailwater plume transport model. Use the depth, flow, temperature, salinity and material concentration of the plume at neutral buoyancy obtained by S6 to create an emission source file. In this example, the depth of the plume at neutral buoyancy obtained by S6 may be different from the vertical depth of the hydrodynamic model. We select the value closest to the neutral buoyancy depth of the plume in the vertical depth of the hydrodynamic model as the depth of the emission source; activate the sediment transport model in the h file, set the sediment type NNS to 1 in the roms.in file, and set LwSrc to T to activate vertical momentum transport. Write the sediment.in file to set the sediment level and difference format to HISMT, the boundary condition to the gradient boundary condition, the median particle size of the sediment to 10μm, and the sedimentation velocity to 0.1 mm s -1 , set SAND_Ltsrc to T so that there is sediment in the emission source.

[0098] S8. Result analysis. Due to the lack of measured data on tailwater plumes, this example mainly verifies the hydrodynamic results to reflect the accuracy of the model simulation of the present invention. The comparison results of the hydrodynamic model and the multi-year average sea surface temperature and salinity of WOA2023 are shown in the figure. Figure 4 As shown, the hydrodynamic model is consistent with the 10-year average of WOA2023. ° The comparison results of temperature and salinity changes with depth within 0-500m at the N section are as follows: Figure 5 The results of comparing the hydrodynamic model with the climatologically averaged HYCOM annual mean sea surface velocity are shown in Figure 6 As shown, the results show that the model simulates the hydrodynamic environment of the study area well.

Claims

1. A numerical simulation method for deep-sea mining tailwater plume based on the ROMS model includes the following steps: Step 1. Determine the study area, study time range, and ROMS model resolution; Step 2. Collect topographic data, atmospheric data, and ocean hydrodynamic data for the study area and study period; Step 3. Generate a grid file using the acquired terrain data; Step 4. Interpolate the obtained atmospheric data and ocean hydrodynamic data to the corresponding grid nodes to create atmospheric forcing files, initial field files, and boundary field files; Step 5. Construct the hydrodynamic model of the target sea area based on the prepared grid file, atmospheric forcing file, initial field file, and boundary field file; Step 6. Determine the tailwater plume emission source parameters, including quantity, longitude and latitude, discharge depth, discharge flow, substance type and its concentration; Its characteristics include: Step 7. Using the data from step 6 and combined with the hydrodynamic data, solve the buoyancy plume model to obtain the initial conditions of the passive transport stage of the tailwater plume; Step 8. Using the results of step 7, build a tailwater plume transport model based on the hydrodynamic model of step 5, run the tailwater plume transport model and analyze the results.

2. The method for numerical simulation of deep-sea mining tailwater plume based on the ROMS model as claimed in claim 1, characterized in that in step 1, the model resolution includes horizontal resolution and vertical resolution, the ROMS model uses a staggered C grid horizontally and a terrain-following sigma coordinate vertically, and the sigma coordinate is calculated by a vertical transformation equation and a vertical stretching function based on water depth, vertical layer number, surface and bottom encryption coefficients.

3. The method for numerical simulation of tailwater plume in deep sea mining based on ROMS model as claimed in claim 1, characterized in that The atmospheric data in step 2 include 10m wind speed u component, 10m wind speed v component, 2m temperature, relative humidity, sea surface atmospheric pressure, rainfall, net longwave radiation flux, and net shortwave radiation flux; the ocean hydrodynamic data in step 2 include seawater flow velocity u component, seawater flow velocity v component, seawater temperature, seawater salinity, and sea surface height.

4. The method for numerical simulation of deep-sea mining tailwater plume based on the ROMS model as claimed in claim 1, characterized in that if the terrain changes drastically in the study area in step 3, it is necessary to smooth the terrain in the grid file.

5. The method for numerical simulation of tailwater plume in deep sea mining based on ROMS model as claimed in claim 1, characterized in that The steps for constructing the hydrodynamic model in step 5 are: (1) Configure the environment required to run the ROMS model; (2) Set the options used in the hydrodynamic model in the h file; (3) In the roms.in file, set the number of horizontal grid nodes, number of vertical layers, number of computational nodes, horizontal and vertical difference formats, boundary conditions, computational time step, total computational step, vertical transformation equation, vertical stretching function, surface and bottom encryption coefficients, and input and output file locations.

6. The method for numerical simulation of tailwater plume in deep sea mining based on ROMS model as claimed in claim 1, characterized in that The hydrodynamic data in step 7 may be provided by step 2 or by the hydrodynamic model established in step 5.

7. The method for numerical simulation of tailwater plume in deep sea mining based on ROMS model as claimed in claim 1, characterized in that The steps to obtain the initial conditions of the passive transport phase of the tailwater plume in step 7 are: (1) Solve the temperature of the outlet under the effect of heat conduction: ， In the above formula, is the ambient water temperature, is the temperature in the drain pipe, depth; (2) Calculate the tailwater density at the discharge port: ， In the above formula, is the density of the plume at the discharge outlet, and are the densities of sediment and water at the outlet, respectively, and are the volume flow rates of sediment and water at the outlet, respectively, Calculate the temperature and salinity of the outlet using the seawater state equation based on the salinity and (1); (3) Solve the discharge phase equation as the initial condition for the buoyancy driven phase: First calculate the effective starting position of the plume : ， in, is the depth at the discharge port, is the length of the flow establishment zone, calculated by the following formula: ， In the above formula, is the radius at the discharge port, is the initial Froude number, where is the initial velocity at the discharge port, is the initial buoyancy at the discharge port, where is the acceleration due to gravity, is the density of the plume at the discharge outlet, is the background seawater density; Then, calculate the effective radius, velocity, and buoyancy of the plume: ， ， ， In the above formula, is the effective radius of the plume, is the effective velocity of the plume, is the effective buoyancy of the plume, is the velocity and density distribution ratio, Calculated by the following formula: ， (4) Calculate the buoyancy drive phase equation: ， ， ， ， ， in, is the volume flux of the plume, is the distance of the plume along the central axis, is the radius of the plume, is the vertical velocity at the plume midline, is the velocity at the plume centerline, is the corrected entrainment coefficient, and are the horizontal entrainment coefficient and the vertical entrainment coefficient, is the background velocity, , , satisfy , is the mass flux of the plume, is the velocity and density distribution ratio, is the buoyancy flux of the plume, N is the buoyancy frequency, is the difference between the plume density and the background environment density, is the background seawater density, is the depth at the plume midline, is the horizontal distance between the plume centerline and the discharge point; (5) Solve the initial conditions of the passive transport stage: Usually the plume is neutrally buoyant. In order to provide initial conditions for the passive transport stage of the ROMS model, it is necessary to solve the equation in (4) for the depth of the neutral buoyancy point of the plume: , and volume flux , and then calculate the concentration of the substance in the plume at the neutral buoyancy depth and plume flow : ， ， In the above formula, Initial volume flux in the buoyancy-driven phase, is the initial concentration in the buoyancy-driven phase.

8. The method for numerical simulation of tailwater plume in deep sea mining based on ROMS model as claimed in claim 7, characterized in that In step (2), the salinity may be provided in step 6, or the salinity of the sea surface may be used.

9. The method for numerical simulation of deep-sea mining tailwater plume based on ROMS model as claimed in claim 1, characterized in that the tailwater plume model construction step in step 8 is: (1) Use the neutral buoyancy depth obtained in step 7 , plume flow , temperature, salinity and substance concentration , generate emission source files, where the substances in the emission sources include: Cohesive and non-cohesive sediments of various particle sizes and settling velocities, various dissolved substances; (2) Set the river_Vshape variable in the emission source file, setting the depth corresponding to the emission source to 1 and the other depths to 0, so that the emission source is located at the specified depth; (3) Set LwSrc to T in the roms.in file and assign a value of 2 to the river_direction variable in the emission source file to make the flow direction of the emission source vertical; (4) Add a sediment transport model or a dissolved matter transport model based on whether the matter in the tailwater plume is sediment or dissolved matter; (5) If the substances in the tailwater plume are soluble substances, it is necessary to set the number of types of soluble substances in the roms.in file and set LtracerSrc to T to activate the transport of soluble substances in the emission source; if the substances in the tailwater plume are sedimentary substances, it is necessary to set the number of types of sedimentary substances in the roms.in file and write a sediment.in file to specify the particle size and sedimentation velocity of the sediment, and set SAND_Ltsrc / MUD_Ltsrc to T according to the type of sediment to activate the sediment transport in the emission source.

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