Simulation calculation method for influence of river sand mining on water flow condition of navigation channel
By constructing a two-dimensional hydrodynamic model with an unstructured grid, the problem of insufficient simulation accuracy of water flow conditions for navigation caused by river sand mining was solved, achieving efficient and accurate simulation calculations, providing scientific decision support, and ensuring navigation safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-26
Smart Images
Figure CN122287449A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of navigation flow condition monitoring technology, specifically to a simulation calculation method for the impact of river sand mining on navigation flow conditions. Background Technology
[0002] River sand and gravel resources are an important source of building materials, and river sand mining is one of the main ways to obtain these resources. However, river sand mining projects inevitably alter the original riverbed boundaries, thereby affecting the navigation conditions and even threatening navigation safety. For example, unscientific sand mining activities may cause the riverbed near the mining area to lower, leading to a drop in the water level of the upstream channel and insufficient navigation depth; it may also alter the flow pattern, forming local eddies, which adversely affect ship navigation.
[0003] Therefore, scientifically and rationally assessing the impact of sand mining projects on waterway flow conditions is of great significance for regulating sand mining activities and ensuring navigation safety. Current assessment methods suffer from problems such as insufficient simulation accuracy, large prediction deviations, and difficulty in efficiently and accurately providing technical support for scientific decision-making by waterway management departments when facing complex river boundaries and variable sand mining conditions.
[0004] Therefore, a simulation calculation method for the impact of river sand mining on navigation flow conditions is provided, which has sufficient simulation accuracy and accurate prediction results. Summary of the Invention
[0005] Therefore, in order to overcome the above-mentioned defects in the prior art, the present invention provides a simulation calculation method for the impact of river sand mining on navigation flow conditions with sufficient simulation accuracy and accurate prediction results.
[0006] This invention discloses a simulation calculation method for the impact of river sand mining on navigation flow conditions, including: S1. Data collection and preprocessing; Collect and integrate basic geographic information and hydrological data of sand mining areas to construct a digital elevation model and hydrological database covering the entire region; S2. Digital model construction and mesh generation; Based on the integrated data and Cartesian coordinate system, the sand mining area is divided using an unstructured grid to obtain the grid file of the sand mining area; S3. Construction and Parameter Setting of Two-Dimensional Hydrodynamic Model Given the initial conditions, boundary conditions, and dynamic boundary techniques of the model, a two-dimensional planar hydrodynamic model based on two-dimensional continuity equations and two-dimensional momentum equations is established through data collection and preprocessing. S4. Model Validation and Calibration The model was validated and calibrated based on existing historical measured data. S5. Operating Condition Design and Impact Prediction Analysis Based on the sand mining plan and navigation engineering design plan, the system designs two sets of working conditions before and after sand mining, and obtains the prediction results based on the simulation values of the hydrodynamic model.
[0007] In S1, the collected data includes: geographic information system data of the study area, high-precision topographic maps including riverbed topography, bank slope morphology and surrounding land topography, historical hydrological observation data including water level, flow rate, velocity and water surface line at different flow levels, geological data, and design data of sand mining and waterway engineering involved. All collected data are systematically organized, verified and converted into a unified digital format to construct digital elevation models and digital river models to meet the input requirements of two-dimensional hydrodynamic models.
[0008] In S2, based on the preprocessed data, the study area is spatially discretized using unstructured mesh technology in the Cartesian coordinate system; the digital model fully covers the main channel and major tributaries and beaches of the study river section; triangular unstructured meshes are used for regional subdivision, and key areas, including the main channel, planned sand mining areas, and bank slope transitions, are locally densified to ensure that the mesh can accurately fit the complex river boundary.
[0009] In S3, after importing the mesh file of the simulated region obtained in S2 into the two-dimensional hydrodynamic model, the multi-dimensional information of the still water state of the river channel is fused to map and obtain the initial values of each mesh of the two-dimensional hydrodynamic model. The multi-dimensional information includes at least water quality monitoring information, underwater geomorphological information, geographic information, meteorological information, and satellite remote sensing information.
[0010] In S3, the initial conditions are set to define the initial field of water depth and flow velocity within the computational area. Boundary conditions include the upstream inlet boundary and the downstream outlet boundary. The upstream inlet boundary is given a flow process line or water level process line as a hydraulic control condition, and the downstream outlet boundary is given a water level process line or water level-flow relationship curve as a hydraulic control condition. The land boundary adopts solid wall boundary conditions, such as free slip boundary conditions or non-slip boundary conditions. For the alternating wet and dry areas caused by changes in river water level, the dynamic boundary technology adopts the water depth judgment method, the automatic grid reconstruction method, or the submerged boundary method to ensure that the model can accurately capture the dynamic changes of the riverbank, effectively handle the inundation and receding processes of water bodies, and avoid calculation distortion. The parameters of this two-dimensional hydrodynamic model are set with reasonable roughness coefficients according to the actual situation of the river channel and are assigned values in different zones according to the riverbed type and vegetation cover of different river sections.
[0011] In S3, the governing equations of the hydrodynamic model include: Continuity equation for water flow: , Equations of water flow: , in, t For time; x , y Here, we are using a right-handed Cartesian coordinate system; d represents the still water depth; h = η + d represents the total water depth; η represents the water level; and u and v represent the components of the flow velocity in the x and y directions, respectively. C v is the Chezy coefficient, n is the Manning coefficient; t ρ is the turbulent viscosity coefficient; g is the acceleration due to gravity; the horizontal line represents the average value at depth. and The velocity at average depth is defined as: .
[0012] In S3, a numerical discretization method is used to handle complex terrain and irregular boundaries. The finite volume method based on unstructured grids is adopted. The flux calculation adopts the Roe scheme to capture shock waves and discontinuous flow fields. The time integration adopts the explicit Euler scheme. The time step is dynamically adjusted to meet the CFL stability condition, so as to improve the flexibility of calculation and adaptability to local terrain changes.
[0013] In S4, model validation was performed by selecting historical low-water and medium-water hydrological observation data of the study area. The validation metrics are: comparing the results of the model calculations, such as water surface line, average cross-sectional velocity, water level-discharge relationship at key stations, and flow split ratio, with the measured data under the current terrain conditions. Model accuracy evaluation assesses the degree of agreement between the model's calculation results and the measured data. Parameter calibration: If the model accuracy does not meet the requirements, the roughness coefficient, diffusion coefficient and other model parameters shall be reasonably adjusted and calibrated within a reasonable range until the model can accurately reflect the hydrodynamic characteristics of the study area.
[0014] In S5, the load case design involves designing two sets of calculation load cases: Working condition 1: Calculation of waterway flow under existing terrain conditions, i.e., the baseline working condition; Working Condition 2: Calculation of waterway flow under the terrain conditions after the sand mining project is implemented, i.e., prediction of the working condition; Simulation results output and analysis: Output hydrodynamic parameters at key locations in the waterway, including: Water level change ΔH = H 采砂后 -H 采砂前 ; Flow velocity change ΔV=V 采砂后 -V 采砂前 ; Change in navigation depth ΔD=D 采砂后-D 采砂前 ; Undesirable flow regimes: regions with crossflow angles greater than 5°; The change in the split ratio ΔQ%=(Q 采砂后 -Q 采砂前 ) / Q 采砂前 ×100%.
[0015] Navigation safety assessment: The impact of sand mining on navigation safety is assessed based on simulation results; if the navigation depth is reduced by more than 10% of the design value or a large area of crossflow or backflow occurs, the sand mining plan needs to be further optimized.
[0016] The technical solution of this invention has the following advantages: In this invention, the simulation calculation method forms a complete and reliable technical process, from data integration, model construction and verification to setting comparative working conditions for quantitative prediction. It can systematically, efficiently and accurately simulate and predict the multidimensional impact of river sand mining projects on navigation flow conditions. This simulation calculation method can provide scientific decision-making basis for water transport management departments to approve sand mining projects and ensure navigation safety in waterways, and has great practical value and technical advantages in engineering practice. Attached Figure Description
[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is a flowchart illustrating the simulation calculation method for the impact of river sand mining on navigation flow conditions as described in this invention. Figure 2 This is a schematic diagram of the grid of the river section studied in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the calculation range of the two-dimensional hydrodynamic model in Embodiment 2 of the present invention; Figure 4 The results are numerical simulations of the flow velocity at the dry section in Embodiment 2 of the present invention. Figure 5 This is a waterway water level verification diagram from Embodiment 2 of the present invention; Figure 6 This is a flow field diagram showing the design flow rate and reclaimed water flow rate at the sand mining channel in Embodiment 2 of the present invention. Detailed Implementation
[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0021] Example 1: As Figure 1 As shown in the figure, this embodiment provides a simulation calculation method for the impact of river sand mining on navigation flow conditions, including: S1. Data collection and preprocessing (i.e., data preparation stage); Collect and integrate basic geographic information and hydrological data of sand mining areas to construct a digital elevation model and hydrological database covering the entire region; Specifically, in S1, the collected data includes: geographic information system data of the study area, high-precision topographic maps including riverbed topography, bank slope morphology and surrounding land topography, historical hydrological observation data including water level, flow rate, flow velocity and water surface line at different flow levels, geological data, and design data of sand mining and waterway engineering involved; all collected data are systematically organized, verified and converted into a unified digital format to construct digital elevation models and digital river models to meet the input requirements of two-dimensional hydrodynamic models.
[0022] S2. Digital model construction and mesh generation (i.e., model mesh construction). Based on the integrated data and Cartesian coordinate system, the sand mining area is divided using an unstructured grid to obtain the grid file of the sand mining area; In S2, based on the preprocessed data, the study area is spatially discretized using unstructured mesh technology in the Cartesian coordinate system; the digital model fully covers the main channel and major tributaries and beaches of the study river section; triangular unstructured meshes are used for regional subdivision, and key areas, including the main channel, planned sand mining areas, and bank slope transitions, are locally densified to ensure that the mesh can accurately fit the complex river boundary.
[0023] S3. Construction and parameter setting of the two-dimensional hydrodynamic model (i.e., hydrodynamic model establishment) Given the initial conditions, boundary conditions, and dynamic boundary techniques of the model, a two-dimensional planar hydrodynamic model based on two-dimensional continuity equations and two-dimensional momentum equations is established through data collection and preprocessing. Specifically, in S3, after importing the mesh file of the simulated region obtained in S2 into the two-dimensional hydrodynamic model, the multi-dimensional information of the still water state of the river channel is fused to map and obtain the initial values of each mesh of the two-dimensional hydrodynamic model. The multi-dimensional information includes at least water quality monitoring information, underwater geomorphological information, geographic information, meteorological information, and satellite remote sensing information.
[0024] Furthermore, in S3, the initial conditions are set to define the initial field of water depth and flow velocity within the computational region; the boundary conditions include the upstream inlet boundary and the downstream outlet boundary. The upstream inlet boundary is given a flow rate process line or a water level process line as a hydraulic control condition, and the downstream outlet boundary is given a water level process line or a water level-flow rate relationship curve as a hydraulic control condition; the land boundary adopts solid wall boundary conditions, such as free slip boundary conditions or no slip boundary conditions. , Where H is the total water depth; u is the flow velocity in the x direction; and v is the flow velocity in the y direction; To calculate the x-coordinate of the grid; The calculation uses the y-coordinate of the grid; t is time; H0 is the initial total water depth; u0 is the initial x-direction velocity; and v0 is the y-direction velocity.
[0025] For areas of alternating wet and dry conditions caused by changes in river water levels, the dynamic boundary technique employs a water depth determination method, an automatic grid reconstruction method, or an immersion boundary method to ensure that the model can accurately capture the dynamic changes of the riverbank, effectively handle the inundation and receding processes of water bodies, and avoid calculation distortion. H=H(t) Q=Q(t) Where H is the boundary water depth; t is time; Q is the boundary flow rate; H(t) is the water level process; and Q(t) is the flow rate process curve.
[0026] The parameters of this two-dimensional hydrodynamic model are set with reasonable roughness coefficients (such as Manning coefficients) based on the actual conditions of the river channel, and are assigned values in different zones according to the riverbed type and vegetation cover of different river sections.
[0027] Furthermore, in S3, the governing equations of the hydrodynamic model include: Continuity equation for water flow: , Equations of water flow: , Where t is time; x and y are in a right-handed Cartesian coordinate system; d is the still water depth; h = η + d is the total water depth; η is the water level; u and v are the components of the flow velocity in the x and y directions, respectively; C is the Chezy coefficient; n is the Manning coefficient; v tρ is the turbulent viscosity coefficient; g is the acceleration due to gravity; the horizontal line represents the average value at depth. and The velocity at average depth is defined as: .
[0028] In S3, numerical discretization techniques are used to handle complex terrain and irregular boundaries. The finite volume method based on unstructured grids is adopted. The flux calculation uses the Roe scheme to capture shock waves and discontinuous flow fields. The time integration adopts the explicit Euler scheme. The time step is dynamically adjusted to meet the CFL stability condition, so as to improve the flexibility of calculation and adaptability to local terrain changes.
[0029] S4. Model Validation and Calibration (i.e., Model Validation and Approval) The model was validated and calibrated based on existing historical measured data. Specifically, in S4, model validation was performed by selecting historical low-water and medium-water hydrological observation data of the study area. The validation metrics are: comparing the results of the model calculations, such as water surface line, average cross-sectional velocity, water level-discharge relationship at key stations, and flow split ratio, with the measured data under the current terrain conditions. Model accuracy evaluation assesses the degree of agreement between the model's calculation results and the measured data. Parameter calibration: If the model accuracy does not meet the requirements, the roughness coefficient, diffusion coefficient and other model parameters shall be reasonably adjusted and calibrated within a reasonable range until the model can accurately reflect the hydrodynamic characteristics of the study area.
[0030] S5. Operating Condition Design and Impact Prediction Analysis (i.e., Operating Condition Design and Prediction) Based on the sand mining plan and navigation engineering design plan, the system designs two sets of working conditions before and after sand mining, and obtains the prediction results based on the simulation values of the hydrodynamic model.
[0031] In S5, the load case design involves designing two sets of calculation load cases: Working condition 1: Calculation of waterway flow under existing terrain conditions, i.e., the baseline working condition; Working Condition 2: Calculation of waterway flow under the terrain conditions after the sand mining project is implemented, i.e., prediction of the working condition; Simulation results output and analysis: Output hydrodynamic parameters at key locations in the waterway, including: Water level change ΔH = H 采砂后 -H 采砂前 ; Flow velocity change ΔV=V 采砂后 -V 采砂前 ; Change in navigation depth ΔD=D 采砂后-D 采砂前 ; Undesirable flow regimes: regions with crossflow angles greater than 5°; The change in the split ratio ΔQ%=(Q 采砂后 -Q 采砂前 ) / Q 采砂前 ×100%.
[0032] Navigation safety assessment: The impact of sand mining on navigation safety is assessed based on the simulation results. If the navigation depth decreases by more than 10% of the design value or harmful flow patterns such as large-area crossflows or backflow areas appear, the navigation safety conditions are not met, and the sand mining plan needs further optimization. If the navigation depth decreases by less than 10% of the design value and no harmful flow patterns appear, the navigation safety conditions are met, and the sand mining plan is feasible. After determining the judgment result, the simulation calculation is terminated and an assessment report is output.
[0033] The simulation calculation method provided in this embodiment forms a complete and reliable technical process, from data integration, model construction and verification to setting comparative working conditions for quantitative prediction. It can systematically, efficiently and accurately simulate and predict the multidimensional impact of river sand mining projects on navigation flow conditions. This simulation calculation method can provide scientific decision-making basis for water transport management departments to approve sand mining projects and ensure navigation safety in waterways, and has great practical value and technical advantages in engineering practice.
[0034] Example 2: Based on the above examples, a specific case study is given using the impact assessment of sand mining in an inland waterway as an example.
[0035] The specific evaluation process is as follows: Step 1: Data Collection and Preprocessing Collect and integrate basic geographic information and hydrological data for the study area. Specifically, this includes: Topographic data: Obtain a high-precision 1:2000 scale river topographic map of the recently measured river section; Hydrological verification data: Collect multiple sets of synchronously measured water level, flow rate and cross-sectional velocity data of the river section during the dry and medium water periods. Engineering data, including the scope of the planned sand mining area, mining elevation, and waterway engineering design data; Finally, all data were standardized in format, corrected in coordinates, and subjected to quality control to construct a digital elevation model and hydrological database covering the entire study area.
[0036] Step 2: Digital Model Construction and Mesh Generation Based on the preprocessed data, the study area was spatially discretized using unstructured mesh technology in a Cartesian coordinate system. The digital model fully covers the main channel, major tributaries, and beaches of the study river section. For mesh partitioning, triangular unstructured meshes were used for regional partitioning, with local densification in key areas such as the main channel, planned sand mining areas, and bank slope transitions to ensure that the mesh can accurately fit the complex river boundary.
[0037] The entire digital model in this embodiment is divided into 963,828 grids, totaling 490,638 nodes. Figure 2 and 3 As shown; the grid accuracy is 10m, with local densification of the study area to an accuracy of 2.0m. The topographic map is a measured topographic map, the elevation system uses the 1985 National Elevation Datum, and the plane coordinate system uses the Geodetic 2000 coordinate system.
[0038] Step 3: Establishment and Parameter Setting of Two-Dimensional Hydrodynamic Model A two-dimensional planar hydrodynamic model based on two-dimensional shallow water equations is established.
[0039] The governing equations of the two-dimensional hydrodynamic model are as follows: Continuity equation for water flow: , Equations of water flow: , , Numerical discretization was performed using the finite volume method based on unstructured grids to discretize the governing equations; flux calculations were performed using the Roe scheme, and time integration was performed using the explicit Euler scheme, with the time step dynamically adjusted to satisfy the CFL stability condition.
[0040] The initial conditions are provided by steady flow calculations, which provide a stable flow field as the initial values.
[0041] In the boundary conditions, the upstream inlet boundary is given by the flow process according to the calculation conditions, the downstream outlet boundary is given by the water level process, and the land boundary adopts the slip boundary condition.
[0042] In this embodiment, the dynamic boundary processing adopts the "dry and wet grid" discrimination method to handle the flooding and exposure process of the beach, and sets reasonable dry and wet water depth thresholds; among the key parameters, the Manning roughness coefficient n of the riverbed is calibrated and assigned according to the riverbed composition zoning.
[0043] Step 4: Model Validation and Calibration The constructed two-dimensional hydrodynamic model was validated using collected hydrological data from the dry and moderate water periods. Validation included verification of the water surface line, cross-sectional velocity distribution, and flow split ratio.
[0044] Water level verification involves selecting water level observation points along the research river section and comparing the water level values calculated by the model under the current topographic conditions with the measured water level data from the same period point by point.
[0045] Cross-sectional velocity verification: By comparing the lateral distribution of the vertical average velocity at multiple characteristic cross-sections, it was determined that the simulated velocity was basically consistent with the measured value in terms of magnitude and lateral variation trend.
[0046] The diversion ratio verification was conducted by calculating the flow rates of each tributary at key nodes of the channel, obtaining the simulated diversion ratio, and then comparing and analyzing it with measured synchronous hydrological data.
[0047] Conclusion: After calibration, the water surface line, cross-sectional velocity distribution and key node split ratio calculated by the model are in good agreement with the measured data, meeting the technical requirements of the "Technical Specification for Simulation Test of Water Transport Engineering" (JTS / T231-2021). The applicability and accuracy of the model in the study area are determined, thus proving that the method can be used for actual sand mining impact prediction analysis.
[0048] Step 5: Operating Condition Design and Impact Prediction Analysis Based on the validated two-dimensional hydrodynamic model, the system design simulates and predicts comparative operating conditions before and after sand mining. Three typical flow conditions—design navigable flow, reclaimed water flow, and flood flow—are selected for simulation.
[0049] Terrain conditions (for each flow level) are simplified into two core comparison conditions: Case 1 (before sand mining): The existing river topography is used as the benchmark for impact assessment; Scenario 2 (Post-Sand Mining): Based on the existing topography, the topography of the sand mining area is modified according to the planned mining scope and elevation to simulate the topographic conditions after the sand mining project is implemented.
[0050] Simulation Calculation and Results Output: By running the model, the flow field under two operating conditions is calculated, and the following key indicators are output and analyzed: 1. Impact of waterway water level: By plotting and comparing the water surface lines along key sections of the waterway before and after sand mining, the quantitative changes in water level after sand mining relative to before sand mining are given. For example... Figure 5 As shown, the simulation results indicate that after taking standardized backfilling measures, the sand mining project has a negligible impact on the water level along the waterway. Under the three flow levels of design flow, medium water flow, and two-year flood flow, the water level change near the mining area in the basin does not exceed 0.01m.
[0051] 2. Impact of Diversion Ratio: Statistical analysis was conducted on the changes in diversion ratio at key nodes in the river's bifurcation. The analysis showed that, under the design flow conditions, sand mining had virtually no impact on navigation.
[0052] 3. The influence of water flow conditions near the sand mining area: By extracting the velocity distribution of characteristic cross-sections of the upstream and downstream navigation channels of the sand mining area, the focus is on the lateral velocity. Specifically, under the design navigation flow and medium-water flow conditions, the velocity vector distribution of the sand mining channel and surrounding waters remains generally straight. For example... Figure 6 As shown in the simulation results, due to the thorough consideration of backfilling measures in the sand mining scheme, the topography of the sand mining area did not significantly obstruct or guide the mainstream flow. The flow field distribution was smooth, and no eddies, backflows, or sudden turbulence phenomena restricted by navigation regulations occurred. By comparing the velocity distribution before and after sand mining, it was found that in terms of velocity magnitude, due to the control of sand mining depth and subsequent backfilling, the velocity variation in the sand mining channel area was extremely small, and the local velocity increment under medium water flow was basically maintained within 0.02 m / s. In terms of flow direction change, since the angle between the water flow direction and the channel direction (crossflow) remained basically unchanged, it ensured that ships could maintain good maneuverability when passing through this section of the river.
[0053] As can be seen from the above specific implementation process, the method provided by this invention can systematically, efficiently, and accurately simulate and predict the multidimensional impact of river sand mining projects on navigation flow conditions. The final evaluation conclusion of this embodiment clearly shows that the simulation calculation method for the impact of river sand mining on navigation flow conditions provided by this application, from data integration, model construction and verification to setting comparative working conditions for quantitative prediction, forms a complete and reliable technical evaluation and verification process; this provides a scientific decision-making basis for water transport management departments to approve sand mining projects and ensure navigation safety; thus, the method provided by this invention has practical value and technical advantages in engineering practice.
[0054] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A simulation calculation method for the influence of river sand mining on the water flow conditions of a navigation channel, characterized in that, include: S1. Data collection and preprocessing; Collect and integrate basic geographic information and hydrological data of sand mining areas to construct a digital elevation model and hydrological database covering the entire region; S2. Digital model construction and mesh generation; Based on the integrated data and Cartesian coordinate system, the sand mining area is divided using an unstructured grid to obtain the grid file of the sand mining area; S3. Construction and Parameter Setting of Two-Dimensional Hydrodynamic Model Given the initial conditions, boundary conditions, and dynamic boundary techniques of the model, a two-dimensional planar hydrodynamic model based on two-dimensional continuity equations and two-dimensional momentum equations is established through data collection and preprocessing. S4. Model Validation and Calibration The model was validated and calibrated based on existing historical measured data. S5. Operating Condition Design and Impact Prediction Analysis Based on the sand mining plan and navigation engineering design plan, the system designs two sets of working conditions before and after sand mining, and obtains the prediction results based on the simulation values of the hydrodynamic model.
2. The simulation calculation method for the influence of river sand mining on the navigation flow condition of a channel according to claim 1, characterized in that, In S1, the collected data includes: geographic information system data of the study area, high-precision topographic maps including riverbed topography, bank slope morphology and surrounding land topography, historical hydrological observation data including water level, flow rate, velocity and water surface line at different flow levels, geological data, and design data of sand mining and waterway engineering involved. All collected data are systematically organized, verified and converted into a unified digital format to construct digital elevation models and digital river models to meet the input requirements of two-dimensional hydrodynamic models.
3. The simulation calculation method of the influence of river sand excavation on navigation flow conditions of a channel according to claim 2, characterized in that, In S2, based on the preprocessed data, the study area is spatially discretized using unstructured mesh technology in the Cartesian coordinate system; the digital model fully covers the main channel and major tributaries and beaches of the study river section; triangular unstructured meshes are used for regional subdivision, and key areas, including the main channel, planned sand mining areas, and bank slope transitions, are locally densified to ensure that the mesh can accurately fit the complex river boundary.
4. The simulation calculation method of the influence of river sand mining on navigation flow conditions according to claim 1, characterized in that, In S3, after importing the mesh file of the simulated region obtained in S2 into the two-dimensional hydrodynamic model, the multi-dimensional information of the still water state of the river channel is fused to map and obtain the initial values of each mesh of the two-dimensional hydrodynamic model. The multi-dimensional information includes at least water quality monitoring information, underwater geomorphological information, geographic information, meteorological information, and satellite remote sensing information.
5. The simulation calculation method of the influence of river sand mining on the water flow conditions of the navigation channel according to claim 4, characterized in that, In S3, the initial conditions are set to define the initial field of water depth and flow velocity within the computational area. Boundary conditions include the upstream inlet boundary and the downstream outlet boundary. The upstream inlet boundary is given a flow process line or water level process line as a hydraulic control condition, and the downstream outlet boundary is given a water level process line or water level-flow relationship curve as a hydraulic control condition. The land boundary adopts solid wall boundary conditions, such as free slip boundary conditions or non-slip boundary conditions. For the alternating wet and dry areas caused by changes in river water level, the dynamic boundary technology adopts the water depth judgment method, the automatic grid reconstruction method, or the submerged boundary method to ensure that the model can accurately capture the dynamic changes of the riverbank, effectively handle the inundation and receding processes of water bodies, and avoid calculation distortion. The parameters of this two-dimensional hydrodynamic model are set with reasonable roughness coefficients according to the actual situation of the river channel and are assigned values in different zones according to the riverbed type and vegetation cover of different river sections.
6. The simulation calculation method for the impact of river sand mining on navigation flow conditions according to claim 5, characterized in that, In S3, the governing equations of the hydrodynamic model include: Continuity equation for water flow: ， Equations of water flow: ， in, t For time; x , y Here, we are using a right-handed Cartesian coordinate system; d represents the still water depth; h = η + d represents the total water depth; η represents the water level; and u and v represent the components of the flow velocity in the x and y directions, respectively. C v is the Chezy coefficient, n is the Manning coefficient; t ρ is the turbulent viscosity coefficient; g is the acceleration due to gravity; the horizontal line represents the average value at depth. and The velocity at average depth is defined as: 。 7. The simulation calculation method for the impact of river sand mining on navigation flow conditions according to claim 5, characterized in that, In S3, a numerical discretization method is used to handle complex terrain and irregular boundaries. The finite volume method based on unstructured grids is adopted. The flux calculation adopts the Roe scheme to capture shock waves and discontinuous flow fields. The time integration adopts the explicit Euler scheme. The time step is dynamically adjusted to meet the CFL stability condition, so as to improve the flexibility of calculation and adaptability to local terrain changes.
8. The simulation calculation method for the impact of river sand mining on navigation flow conditions according to claim 1, characterized in that, In S4, model validation was performed by selecting historical low-water and medium-water hydrological observation data of the study area. The validation metrics are: comparing the results of the model calculations, such as water surface line, average cross-sectional velocity, water level-discharge relationship at key stations, and flow split ratio, with the measured data under the current terrain conditions. Model accuracy evaluation assesses the degree of agreement between the model's calculation results and the measured data. Parameter calibration: If the model accuracy does not meet the requirements, the roughness coefficient, diffusion coefficient and other model parameters shall be reasonably adjusted and calibrated within a reasonable range until the model can accurately reflect the hydrodynamic characteristics of the study area.
9. The simulation calculation method for the impact of river sand mining on navigation flow conditions according to claim 1, characterized in that, In S5, the load case design involves designing two sets of calculation load cases: Working condition 1: Calculation of waterway flow under existing terrain conditions, i.e., the baseline working condition; Working Condition 2: Calculation of waterway flow under the terrain conditions after the sand mining project is implemented, i.e., prediction of the working condition; Simulation results output and analysis: Output hydrodynamic parameters at key locations in the waterway, including: Water level change amount AH = H 采砂后 - H 采砂前 ; Flow rate change amount AV = V 采砂后 -V 采砂前 ; Depth variation ΔD = D 采砂后 - D 采砂前 ; Undesirable flow regimes: regions with crossflow angles greater than 5°; Split ratio change AQ% = (Q 采砂后 - Q 采砂前 ) / Q 采砂前 x 100%; Navigation safety assessment: The impact of sand mining on navigation safety is assessed based on simulation results; if the navigation depth is reduced by more than 10% of the design value or harmful flow patterns such as large-area crossflow or backflow areas appear, the sand mining plan needs to be further optimized.