A dynamic numerical calculation method for predicting seabed erosion and deposition and application thereof

Abstract

A kind of dynamic numerical calculation method for predicting seabed erosion and deposition, comprising: step 1, determining the dominant dynamic factor affecting seabed erosion and deposition evolution;Step 2, determining the critical incipient shear stress and critical deposition shear stress of sediment;Step 3, establishing a tidal mathematical model and / or wave mathematical model and verifying, calculating the dynamic elements of the study area, giving the flow field and / or wave field of the study area;Step 4, calculating the bed shear stress field of the study area;Step 5, comparing the critical incipient shear stress and critical deposition shear stress of sediment determined in step 2 with the bed shear stress calculated in step 4, judging the incipient, deposition status and range of bed sediment;Step 6, calculating the seabed erosion and deposition amplitude using the erosion and deposition calculation formula, and analyzing the seabed erosion and deposition trend.The present application overcomes the deficiency that the traditional seabed evolution analysis method cannot quantitatively predict the seabed erosion and deposition amplitude, and is simple and efficient compared with the sediment mathematical model for predicting seabed erosion and deposition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of water transportation technology, and relates to a dynamic numerical calculation method for predicting seabed erosion and deposition. BACKGROUND

[0002] The prediction of seabed erosion and deposition before and after the implementation of a project has been a key technical problem in seabed evolution and coastal engineering, and has been the focus of attention of port and channel engineers. Many scholars at home and abroad have carried out a large amount of research work on the prediction of seabed erosion and deposition through field observation and model research, and the main research methods can be divided into three categories: empirical judgment based on measured data, semi-empirical and semi-theoretical formula prediction, and sediment mathematical model prediction. Since the empirical judgment based on measured data has not reached the quantitative standard, the semi-empirical and semi-theoretical formula prediction method has great randomness in the parameter calibration, and the research results have certain uncertainty, and the sediment mathematical model prediction method takes a long time and has a large input, therefore, it is necessary to develop a simple and efficient seabed erosion and deposition prediction method. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the shortcomings of the previous seabed erosion and deposition prediction methods, such as being unable to quantitatively analyze, taking a long time to calculate, and having a large input, and to provide a dynamic numerical calculation method for predicting seabed erosion and deposition, which can meet the needs of seabed evolution analysis and coastal engineering research in terms of calculation efficiency and accuracy.

[0004] To solve the above technical problems, the present application adopts the following technical solutions:

[0005] A dynamic numerical calculation method for predicting seabed erosion and deposition, comprising the following steps:

[0006] Step 1: determining the dominant dynamic factors affecting seabed erosion and deposition evolution: according to the water depth conditions, hydrodynamic conditions, and sediment characteristics of the research area, the dominant dynamic factors affecting seabed erosion and deposition evolution are determined, which can generally be divided into three cases of tidal current, wave, and wave-current interaction;

[0007] Step 2: determining the critical incipient shear stress and critical deposition shear stress of the sediment through sediment hydraulic property test or literature review;

[0008] Step 3: establishing a tidal current and / or wave mathematical model according to the dominant dynamic factors determined in step 1, and verifying the model using measured data, wherein the verification result meets the requirements of Technical Specification for Simulation Test of Water Transport Engineering (JTS / T 231-2021), and then carrying out numerical simulation of hydrodynamic elements to give the flow field and / or wave field of the research area;

[0009]

[0010] Step 4: substituting the hydrodynamic results calculated in step 3 into the shear stress calculation formula to calculate the bed shear stress of the research area;​

[0011] Step 5, determine the bed surface sediment starting and deposition conditions and range by comparing the critical starting shear stress and the critical deposition shear stress determined in step 2 with the bed surface shear stress calculated in step 4; generally, when the bed surface shear stress is greater than the critical starting shear stress of the sediment, the sediment is started; when the bed surface shear stress is less than the critical deposition shear stress of the sediment, the sediment is deposited.

[0012] Step 6, calculate the sea bed scouring and silting range using the scouring and silting calculation formula to analyze the bed scouring and silting trend: according to the sea bed scouring and silting trend determined in step 5, calculate the sea bed scouring and silting, and analyze the bed scouring and silting trend.

[0013] The specific process of step 1 is: according to the water depth conditions, hydrodynamic conditions, sediment characteristics, etc. of the study area, determine the dominant dynamic factors affecting the evolution of the sea bed scouring and silting, which can be generally divided into three cases: tidal current, wave, and wave-current interaction.

[0014] The specific process of step 2 is: according to the test results or literature sorting of the hydrodynamic characteristics of the sediment in the study area, determine the critical starting shear stress and the critical deposition shear stress of the sediment in the study area.

[0015] The specific process of step 3 is: according to the dominant dynamic factors affecting the evolution of the sea bed scouring and silting determined in step 1, respectively establish the mathematical model of tidal current and / or wave, and after the calibration and verification, carry out the simulation calculation of the aforementioned hydrodynamic factors.

[0016] (1) For the area dominated by tidal current, establish a mathematical model of water flow;

[0017] (2) For the area dominated by wave, establish a mathematical model of wave;

[0018] (3) For the area dominated by wave-current interaction, a mathematical model of water flow and a mathematical model of wave need to be established respectively.

[0019] The control equations and solution methods of the mathematical model and the mathematical model of wave can be selected from the equations and solution methods recommended in the current relevant specifications (Technical Specifications for Simulation Test of Water Transport Engineering (JTS / T 231-2021)).

[0020] The specific process of step 4 is: substitute the hydrodynamic results calculated in step 3 into the shear stress calculation formula to calculate the bed surface shear stress of the study area. The bed surface shear stress τ b The empirical formula in the textbook of hydraulics or published literature can be used for calculation, or the following calculation formula can be selected according to the dominant dynamic factors of the study area.

[0021] 1) Only tidal current, the bed surface shear stress τ b The following formula can be used for calculation:

[0022] τ b = τ c = ρu *c (1)

[0023] where: τ c is the bed shear stress under the action of water flow, ρ is the density of water, u *c is the bed friction velocity under the action of water flow, h is the water depth, Δ is the bed roughness height, when the median grain size D 50 of the bed sediment is ≤0.5mm, Δ = 1mm, when D 50 >0.5mm, Δ = 2D 50 , is the vertical average velocity, calculated by the hydrodynamic mathematical model described in step 3.

[0024] 2) only wave action, the bed shear stress τ b can be calculated by the following formula:

[0025]

[0026] where: τ wm is the bed shear stress under the action of wave, f w is the wave friction coefficient, generally in the range of 0.005-0.02, for silt sea bed, generally take 0.01, u wm is the velocity amplitude of water particles at the bottom under the action of wave, where H is the wave height, T is the wave period, k is the wave number, k = 2π / L, L is the wave length; H, T and L are calculated by the wave mathematical model in step 3.

[0027] 3) wave flow interaction, the bed shear stress τ b can be calculated by the following formula:

[0028]

[0029] where: is the average value of the bed shear stress in a wave period under the action of wave flow.

[0030] The specific process of the step 5 is: comparing the critical incipient shear stress τ e of the sediment, the critical deposition shear stress τ d determined in step 2 and the bed shear stress τ b calculated in step 4, to determine the incipient and deposition conditions and range of the bed sediment. Generally: when the bed shear stress is greater than the critical incipient shear stress of the sediment, the sediment is incipient; when the bed shear stress is less than the critical deposition shear stress of the sediment, the sediment is deposited.

[0031] (1) if τb >τ e , the bed sediment starts to enter the water body;

[0032] (2) If τ b <τ d , the bed sediment falls and deposits in the water body;

[0033] (3) If τ d <τ b <τ c , no exchange of sediment between the bed and the water body occurs.

[0034] Taking τ or τ as the criterion for the occurrence of obvious incipient motion or deposition of seabed sediment, the thickness of seabed scouring or deposition is calculated, if τ and τ , it is determined that the seabed erosion and deposition in the study area are relatively balanced.

[0035] The specific process of step 6 is: the seabed scouring and deposition amplitude is calculated using the scouring and deposition calculation formula, and the seabed scouring and deposition trend is analyzed.

[0036] The seabed scouring and deposition thickness can be calculated using the empirical formula in the textbook of seabed evolution or published literature, or the following calculation formula can be selected according to the form of sediment movement:

[0037] 1) In the area where the sediment mainly moves in the form of suspended load

[0038] (1) When the bed surface deposits, the deposition thickness is calculated according to the following formula:

[0039]

[0040] In the formula: η d is the deposition thickness, Δt d is the deposition time, k is the sediment deposition probability, C b is the bottom sediment concentration, ω is the sediment settling velocity, τ b is the bed shear stress, τ d is the critical deposition shear stress of sediment. The sediment deposition probability k in formula (4) can be calculated using the following formula:

[0041]

[0042] is the probability integral function, which can be obtained from Table 2; ω is the sediment settling velocity, σ is the root mean square of the fluctuating flow velocity, v is the average flow velocity of the section, g is the acceleration of gravity, and C is the Chezy coefficient of the study sea area.

[0043] Table 2 Probability integral function Value table

[0044]

[0045] (2) When the bed surface is scoured, the scouring thickness is calculated according to the bed surface properties by the following formula:

[0046] ① If the bulk density is vertically uniformly distributed on the bed surface,

[0047] ② If the bulk density is gradually increased from top to bottom on the naturally compacted bed surface,

[0048] In the formula: η e is the scouring thickness, Δt d is the scouring time, M is the bed surface sediment scouring coefficient, which is related to the properties of the sediment, and α and β are parameters that vary with the structure and density of the deposited sediment, and τ e is the critical incipient shear stress of the sediment.

[0049] (3) When τ d < τ b < τ c , the bed surface does not deposit or scour, i.e., Δη d = Δη e = 0.

[0050] (4) The bed surface deposition and scouring change Δη b = Δη d + Δη e .

[0051] 2) The region where the sediment mainly moves in the form of wash load

[0052] (1) When the bed surface is deposited, the deposition thickness is calculated according to the following formula:

[0053] Δη d = Δt d · ωC b (8)

[0054] (2) When the bed surface is scoured, the scouring thickness is calculated according to the following formula:

[0055]

[0056] In the formula: s is the specific gravity of the sediment, g is the acceleration of gravity, D 50 is the median particle size of the sediment, ψ and ψ c are the Hillz number under the action of water power and the critical incipient Hillz number of the sediment, respectively, ν is the viscosity coefficient of the water body.

[0057] If the bed surface deposition thickness Δη d≤0.2m or the thickness of the deposition Δη e ≤0.2m, it is judged that the seabed of the study area is relatively stable, and vice versa if Δη d >0.2m or Δη e >0.2m, it is judged that the seabed of the study area is relatively stable, and vice versa if Δη

[0058] Thus, the whole process of the dynamic numerical calculation for predicting the seabed erosion and deposition is completed.

[0059] Compared with the prior art, the present application has the following advantages:

[0060] The present application discloses a dynamic numerical calculation method for predicting the seabed erosion and deposition, which compares and analyzes the measured critical incipient shear stress, the critical deposition shear stress and the bed shear stress calculated by a mathematical model, predicts the seabed erosion and deposition, and overcomes the defects of the previous seabed evolution prediction, such as the inability to quantitatively analyze, the long time-consuming and limited precision of the sand mathematical model prediction of the beach erosion and deposition, and enriches the research method of the seabed evolution. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 is a flow chart of the dynamic numerical calculation method for predicting the seabed erosion and deposition according to the present application.

[0062] Figure 2 is an embodiment (Lianyungang and its adjacent sea area) of the present application.

[0063] Figure 3 is a two-dimensional tidal current mathematical model and wave mathematical model calculation range and grid division diagram of the present application.

[0064] Figure 4 is a tidal current mathematical model calculation result diagram of the present application.

[0065] Figure 5 is a wave mathematical model calculation result diagram of the present application.

[0066] Figure 6 is a bed shear stress calculation result diagram of the present application at a typical time during a strong wind.

[0067] Figure 7 is a seabed erosion and deposition prediction result diagram of the present application after the action of a strong wind. DETAILED DESCRIPTION

[0068] The present application will be described in detail below in combination with an example of Lianyungang and its adjacent sea area.

[0069] Lianyungang is located in the southwest of the Huanghai Gulf. Its north and east directions are open sea areas. Lianyungang Port Area, Xuwei Port Area and 300,000-ton channel are built in the sea area. The channel plane is arranged in a "person" shape. The tidal movement of Lianyungang and the nearby sea area is controlled by the standing wave system of the South Yellow Sea. In the outer sea, it is a rotating flow, and in the nearshore area, it is a reciprocating flow, and the flow direction is basically consistent with the shore line direction. There is no large runoff into the sea area, and the flow velocity is generally small. The wave influence is significant, and the common and strong wave directions are both NE.

[0070] The method comprises the following steps:

[0071] Step 1, determining the dominant dynamic factor affecting the evolution of the seabed erosion: according to the water depth conditions, hydrodynamic conditions, sediment characteristics and the like of the research area, the dominant dynamic factor affecting the evolution of the seabed erosion is determined, which can be generally divided into tidal current, wave and wave-current combined action.

[0072] The seabed evolution of Lianyungang and the nearby sea area is affected by the combined action of waves and tides, so it is necessary to calculate the bed scour caused by the combined action of the two.

[0073] Step 2, determining the critical incipient shear stress and critical deposition shear stress of the sediment through the sediment hydraulic property test or literature review.

[0074] According to the hydraulic property test results of the Tianjin Waterway Engineering Science Institute of the Ministry of Transport, the critical incipient shear stress of the Lianyungang channel sediment under the combined action of waves and tides is between 0.44 and 0.48 N / m 2 , and the average value in this example is 0.46 N / m 2 . According to the relevant results of Huang Jianwei's "Research and Application of Coastal and Estuary Cohesive Sediment Movement Rules", when the initial sediment concentration of Lianyungang silt is 0.4-1.7 kg / m 3 , the corresponding critical deposition shear stress is 0.044-0.065 N / m 2 . Considering that the sediment concentration is higher in the gale days of Lianyungang sea area (about 2.0 kg / m 3 of the maximum vertical average sediment concentration observed by the seat frame in the 3m and 5m water depth of Xuwei sea area during the "Vipa" typhoon in September 2007), the critical deposition shear stress is 0.07 N / m 2 in this example.

[0075] Step 3. According to the dominant dynamic factors determined in Step 1, establish a tidal mathematical model and / or a wave mathematical model, and use the measured data to verify the model. After the verification results meet the requirements of the Technical Specification for Simulation Test of Water Transport Engineering (JTS / T 231-2021), carry out numerical simulation of the hydrodynamic factors, and give the flow field and / or wave field of the study area.

[0076] In this example, a two-dimensional tidal flow mathematical model and a wave mathematical model for the Lianyungang and adjacent sea area are established. The calculation domain is divided into grids using unstructured grids, and the calculation domain and grid division are shown in Figure 3 . The tidal mathematical model is verified using hydrological test data in September 2023. After the verification results of the tidal level, flow velocity, and flow direction at the measurement points meet the accuracy requirements specified in the Technical Specification for Simulation Test of Water Transport Engineering (JTS / T 231-2021), the flow field during the spring tide period in this sea area is simulated. The flow field and flow velocity distribution at the time of rising tide are shown in Figure 4 . The wave mathematical model is verified using the bottom-mounted wave observation data during the influence of Typhoon Wipha on the Lianyungang sea area in September 2007. After the verification results of wave height, wave period, and wave direction at the measurement points meet the accuracy requirements specified in the Technical Specification for Simulation Test of Water Transport Engineering (JTS / T 231-2021), the wave field simulation under the action of 10-level NE wind in this sea area is carried out. The effective wave height distribution at high water level is shown in Figure 5 .

[0077] Step 4. Substitute the hydrodynamic results calculated in Step 3 into the shear stress calculation formula to calculate the bed shear stress field in the study area: Substitute the hydrodynamic factors calculated in Step 3 into the corresponding bed shear stress calculation formulas (1) to (3) to calculate the bed shear stress field in the study area. The wave friction coefficient f w According to the bottom material of the Lianyungang sea area, which is a silt sea bed, and combined with the analysis of wave characteristics, the wave friction coefficient f w is taken as 0.01;

[0078] Substitute the tidal flow velocity and water depth calculated by the tidal flow model in Step 3, and the wave height, wave period, wave length, and water depth calculated by the wave model into formulas (1) and (2) respectively to calculate the bed shear stress under the action of tidal flow and wave. Then use formula (3) to calculate the bed shear stress under the combined action of wave and tidal flow. During the action of strong wind, the bed shear stress distribution under the combined action of wave and tidal flow at the typical time (high water level) is shown in Figure 6 .

[0079] Step 5. Compare the bed shear stress calculated in Step 4 with the critical incipient shear stress and critical deposition shear stress determined in Step 2 to determine.

[0080] Compare the Lianyungang sediment critical incipient shear stress τ e, critical deposition shear stress τ d and the bed shear stress τ b calculated in step 4, the bed shear stress τ or , the bed sediment in this area is in a state of obvious incipient motion or deposition, and the thickness of the seabed scouring or deposition is calculated in step 6; if and , the bed sediment in this area will not change significantly, and the seabed is stable.

[0081] Step 6, the seabed scouring or deposition amplitude is calculated using the scouring and deposition calculation formula, and the seabed scouring or deposition trend is analyzed.

[0082] (1) If the sediment in a certain area is obviously deposited, the deposition thickness is calculated using formula (4), wherein the sediment deposition probability k is calculated according to formula (5), and is taken as 0.7 (the sediment deposition probability k is calculated by the calculation formula).

[0083] (2) If the sediment in a certain area is obviously started, the scouring thickness is calculated using formula (6) or formula (7), wherein the scouring coefficient M of the bed sediment is taken as 0.36×10 -4 kg / m 2 ·s, which is referred to in Yu Zhiying, et al. “Water dynamic characteristics of Lianyungang muddy coast and beach evolution under the condition of artificial blowing mud”.

[0084] The seabed scouring or deposition amplitude prediction results of Lianyungang and its adjacent sea area after a 10-level NE wind are shown in Figure 7 , and the calculation results of step 6 are reviewed according to the seabed scouring or deposition trend determined in step 5, and the scouring or deposition calculation amplitude is basically consistent with the scouring or deposition trend.

[0085] The above description of the embodiments is for the convenience of those skilled in the art to understand and use the present application. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A dynamic numerical calculation method for predicting seabed erosion and deposition, comprising the following steps: Step 1: determining the dominant dynamic factors affecting seabed erosion and deposition evolution: determining the dominant dynamic factors affecting seabed erosion and deposition evolution according to the water depth conditions, hydrodynamic conditions and sediment characteristics of the study area; Step 2, determine the critical incipient shear stress τ e , of the sediment by sediment hydraulic characteristics test or literature review d ; Step 3: establishing a mathematical model of tidal current and / or wave according to the dominant dynamic factors determined in Step 1, verifying the model with measured data, and carrying out numerical simulation of hydrodynamic force after the verification result meets the requirements of Technical Code for Simulation Test of Waterway Engineering (JTS / T 231-2021) to give the flow field and / or wave field of the study area; Step 4, the hydrodynamic results calculated in Step 3 are substituted into the shear stress calculation formula to calculate the bed shear stress τ of the study area b ; Step 5: comparing the critical incipient shear stress and critical deposition shear stress determined in Step 2 with the bed shear stress calculated in Step 4 to determine the incipient, deposition and erosion conditions and range of the bed sediment; Step 6: calculating the seabed erosion and deposition amplitude by using the erosion and deposition calculation formula and analyzing the bed erosion and deposition trend. In step 5, the bed shear stress τ b determined in step 2 e , the critical deposition shear stress τ d ; (1) If τ b > τ e , the bed sediment starts to enter the water body; (2) If τ b < τ d , the sediment falls to the bed in the water body; (3) If τ d < τ b < τ c , the bed surface and the water body do not exchange sediment; In step 6, according to the analysis results of step 5, the sea bed scouring or deposition thickness is calculated with or as the judgment standard of the obvious starting or deposition of sea bed sediment, if and the sea bed scouring and deposition of the study area is judged to be relatively balanced.

2. A method of predicting seabed erosion and deposition by dynamic numerical calculation according to claim 1, characterized in that: The dominant dynamic factors in Step 1 include tidal current, wave and wave-current interaction.

3. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 1, characterized in that: In Step 3, the mathematical models of tidal current and / or wave are established according to the dominant dynamic factors determined in Step 1, and the simulation calculation of the aforementioned hydrodynamic factors is carried out after the calibration and verification. (1) In the region mainly affected by tidal current, a mathematical model of tidal current is established; (2) In the region mainly affected by wave, a mathematical model of wave is established; (3) In the region mainly affected by wave-current interaction, a mathematical model of tidal current and a mathematical model of wave are established respectively.

4. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 1, characterized in that: In step 4, the bed shear stress τ b Calculated using empirical formula.

5. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 1, characterized in that: In step 4, only the tidal current acts, the bed shear stress τ b The following formula was used for the calculation: τ b = τ c = ρu *c (1) where τ is the bed shear stress, ρ is the water density, u is the water velocity, and h is the water depth. c *c is the bed friction velocity, calculated from the water dynamic model described in Step 3. h is the water depth, and Δ is the bed roughness height. When the median grain size of the bed sediment D 50 ≤ 0.5 mm, Δ = 1 mm. When D 50 > 0.5 mm, Δ = 2D 50 , is the average vertical flow velocity, calculated from the water dynamic model described in Step 3.​ 6. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 5, characterized in that: In step 4, only wave action, bed shear stress τ b The following formula was used for the calculation: where τ wm is the bed shear stress under wave action, f w is the wave friction coefficient, u wm is the velocity amplitude of water particles at the bottom under wave action, where H is the wave height, T is the wave period, k is the wave number, k = 2π / L, L is the wave length; H, T and L are calculated by the wave mathematical model in step 3.

7. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 6, characterized in that: In step 4, the wave-current interaction, the bed shear stress τ b The following formula was used to calculate: In the formula: is the average value of the bed shear stress in a wave period under the combined action of waves and currents.

8. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 6, characterized in that: f w The value range of f is 0.005-0.02; for the silt sea bed, f w The value of f is 0.

01.

9. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 1, characterized in that: The bed erosion and deposition thickness is calculated by using an empirical formula.

10. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 1, characterized in that: For the region mainly affected by suspended load movement, the bed erosion and deposition thickness is calculated by using the following formula: (1) When the bed is deposited, the deposition thickness is calculated according to the following formula: where: η d is the thickness of the deposit, Δt d is the time of deposition, k is the probability of sediment deposition, C b is the sediment concentration at the bottom, ω is the settling velocity of the sediment, τ b is the bed shear stress, τ d is the critical shear stress for sediment deposition; (2) When the bed is eroded, the erosion thickness is calculated according to the following formula: ① If the weight density is vertically uniformly distributed on the bottom, (ii) if the bulk density is a natural compacted bed which is gradually increasing from top to bottom, where: η e is the scour depth, Δt d is the scour time, M is the bed sediment scour coefficient, which is related to the properties of the sediment, and α and β are parameters that vary with the structure and density of the deposited sediment, τ e is the critical incipient shear stress of the sediment; (3) when τ d < τ b < τ c , the bed surface does not undergo deposition or erosion, i.e. Δη d = Δη e = 0; (4) bed surface erosion and deposition change Δη b = Δη d + Δη e .

11. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 1, characterized in that: For the region mainly affected by bed load movement, the bed erosion and deposition thickness is calculated by using the following formula: (1) When the bed is deposited, the deposition thickness is calculated according to the following formula: Δη d = Δt d • ωC b (8) (2) When the bed is eroded, the erosion thickness is calculated according to the following formula: where s is the sediment specific weight, g is the gravitational acceleration, D 50 is the median grain size of the sediment, ψ, ψ c are the Hill number under the hydrodynamic action and the critical incipient Hill number of the sediment, respectively, ν is the water body viscosity coefficient; and ρ is the water density. If the thickness of the bed surface sedimentation Δη d ≤ 0.2 m or the thickness of the sedimentation Δη e ≤ 0.2 m, it is determined that the seabed of the study area is relatively stable, otherwise, if Δη d > 0.2 m or the thickness of the sedimentation Δη e > 0.2 m, it is determined that the seabed activity of the study area is strong.

12. The dynamic numerical calculation method for predicting seabed erosion and deposition according to claim 10, characterized in that: The sediment deposition probability k in formula (4) is calculated by the following formula: For the probability integral function, the values can be found in Table 1; ω is the settling velocity of the sediment, σ is the root mean square of the fluctuating flow velocity, v is the average flow velocity over the cross section, g is the acceleration due to gravity, and C is the Chezy coefficient for the study area.

13. The method of claim 12, wherein the method is used for predicting seabed erosion and deposition under the action of tidal current, wave or wave and current, and under the action of suspended load or non-cohesive load. The following table was obtained; Probability integral function Value table 14. Use of the method of dynamic numerical calculation of the prediction of the seabed scouring and silting according to claim 1, characterized in that:

13. The method of claim 12, wherein the method is used for predicting seabed erosion and deposition under the action of tidal current, wave or wave and current, and under the action of suspended load or non-cohesive load.

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