A method and system for predicting the stable morphology of sand-mud mixed shallow sea negative topography

Abstract

The present invention discloses a method and system for predicting the stable morphology of sand-mud mixed shallow-water negative topography. The method comprises: constructing a continuity equation for the evolution of the topography; calculating the total sediment transport rate for each tidal cycle based on the sediment characteristics of the sand-mud percentage, and calculating the change in bed elevation according to the continuity equation for the evolution of the topography; obtaining the spatial variation of the total sediment transport rate for each tidal cycle; if the spatial variation is greater than a set value, updating the data to calculate a new spatial variation of the total sediment transport rate until it is less than or equal to the set value, at which point the calculation is stopped; combining the bed elevation to characterize the topography, assess the geomorphic stability of the negative topography, and predict the erosion or siltation trend of the negative topography. Simplifying the shallow-water negative topography into a one-dimensional form overcomes the computational crash caused by the cumulative error of traditional discrete methods, shortening the calculation time and ensuring the stability of the results of the landform evolution calculation.

Description

Technical Field

[0001] The present invention relates to an analytical model of a stable landform, and in particular to an analytical model method of a stable landform of a sand-mud mixed shallow sea negative terrain. Background Art

[0002] In estuarine coastal and offshore environments, because protrusions such as islands and headlands alter local tidal characteristics to a certain extent, negative landforms such as scour troughs, tidal gullies, and distributary channels often develop. Their main axes align with the direction of the local reciprocating tides, and the water depth is several meters or even tens of meters greater than that of the surrounding waters. The length, width, and depth of negative landforms can vary by several orders of magnitude in different regional environments. Due to their greater depths, they often serve as natural harbor and waterway resources. The stable geomorphic form they can achieve under the influence of tidal forces is a key parameter that must be considered in the planning and design of projects such as cross-sea bridge construction and submarine pipeline laying. Therefore, predicting the stable geomorphic form that can be achieved under local tidal dynamics and sediment conditions is of great practical significance.

[0003] Although recent progress has been made in numerical simulations of shallow-water geomorphic dynamics, these models require complex boundary conditions and input parameters, typically in two-dimensional or three-dimensional form. Simulating and predicting long-term geomorphic evolution often requires extremely long computational times. Accumulated errors can lead to unstable results and even system crashes over extended periods. Sediments in estuarine, coastal, and offshore environments are often composed of a mixture of sand and mud, and negative topography composed entirely of sand or mud is rare. The percentages of sandy and muddy sediment components vary from region to region, and the transport patterns and corresponding calculation methods for these sediments differ significantly. Consequently, a specialized research method for predicting the stable morphology of shallow-water negative topography characterized by mixed sand and mud sediments is currently lacking. Summary of the Invention

[0004] In order to predict the dynamic landform of sand-mud mixed shallow sea negative topography, the present application provides a method for predicting the stable morphology of sand-mud mixed shallow sea negative topography.

[0005] A method for predicting the stable form of sand-mud mixed shallow sea negative topography, comprising the following steps:

[0006] Based on the topographic data of the sand-mud mixed shallow sea negative topography waters, a coordinate system is established and a continuity equation for landform evolution is constructed;

[0007] The transport rate of sandy sediments is calculated based on the relative density of sediment and water, the median particle size of sediment, and the characteristic values of flow velocity at high and low tides.

[0008] Calculating the scouring flux of the muddy sediment based on the scouring coefficient, the sedimentation shear stress of the sediment, and the shear stress of the water flow; calculating the settling flux of the muddy sediment based on the sediment settling velocity, the sand content of the water body, the sedimentation or starting critical shear stress of the sediment, and the shear stress of the water flow; and calculating the transport rate of the muddy sediment based on the scouring flux and the sedimentation flux of the sediment;

[0009] In each tidal cycle, a total sediment transport rate is calculated based on the percentage of sand and mud components, the transport rate of the sandy sediments, and the transport rate of the muddy sediments, and a bed elevation is calculated based on a geomorphic evolution continuity equation and the total sediment transport rate.

[0010] The spatial variation of the total sediment transport rate in each tidal cycle is obtained based on the total sediment transport rate along the course. If the spatial variation of the total sediment transport rate is greater than a set value, it indicates that the landform has not reached a stable state, and the data is updated. Specifically, the spatial variation of the total sediment transport rate is calculated based on the characteristic values of the flow velocity at high and low tides. The calculation of the total sediment transport rate and bed elevation is stopped until the spatial variation of the total sediment transport rate is less than or equal to the set value.

[0011] Combined with the bed elevation, the landform of the sand-mud mixed shallow sea negative topography in a stable form is depicted, the trend of negative topography erosion or siltation is predicted, and the landform stability of the sand-mud mixed shallow sea negative topography is evaluated.

[0012] Furthermore, the transport rate of sandy sediments is calculated, including:

[0013]

[0014] Among them, C z is the Xie Cai coefficient, △ is the relative density of sediment and water, α is the correction coefficient, D 50 is the median particle size of the sediment, U is the characteristic value of the flow velocity at high tide or low tide, q s is the transport rate of sandy sediments.

[0015] Furthermore, the transport rate of muddy sediments is calculated, including:

[0016] q m =ED

[0017] Among them, q m is the transport rate of muddy sediments, E and D are the scouring amount and sedimentation flux of muddy sediments, respectively.

[0018] When τ>τ c hour,

[0019] When τ<τ c hour,

[0020] Where M is the scour coefficient, τ c is the sedimentation or starting critical shear stress of sediment, c is the sediment content of water, w s is the sediment settling velocity; τ is the water shear stress.

[0021] Furthermore, the water shear stress is calculated as follows:

[0022]

[0023] Among them, ρ w is the density of water, and g is the acceleration due to gravity.

[0024] The transport patterns of sandy sediments are significantly different from those of muddy sediments. When calculating the transport rate, the influence of different sediment component types must be taken into account. This scheme calculates the transport rates of sandy and muddy sediments respectively, and then calculates the total sediment transport rate in the negative terrain based on their respective proportions.

[0025] Furthermore, calculating the bed elevation also includes: discretizing the landform evolution continuity equation using a Lax explicit format.

[0026] Furthermore, establishing the coordinate system specifically includes: taking the low point of the sand-mud mixed shallow sea negative terrain as the coordinate origin, and taking the water flow direction of the negative terrain as the horizontal coordinate.

[0027] The present application also discloses a system for predicting the stable morphology of sand-mud mixed shallow sea negative topography, comprising:

[0028] The model coordinate unit is used to establish a coordinate system and construct a continuity equation for landform evolution based on the topographic data of the sand-mud mixed shallow sea negative topography water area;

[0029] a data storage unit for calculating the transport rate of sandy sediments based on the relative density of sediments and water, the median particle size of sediments, and the characteristic value of the flow velocity of the rising and falling tides;

[0030] a calculation unit for calculating the scour flux of the muddy sediment based on the scour coefficient, the sedimentation shear stress of the sediment, and the shear stress of the water flow; calculating the sedimentation flux of the muddy sediment based on the sediment settling velocity, the sand content of the water body, the sedimentation shear stress of the sediment, and the shear stress of the water flow; and calculating the transport rate of the muddy sediment based on the scour flux and the sedimentation flux of the sediment; calculating the total sediment transport rate for each tidal cycle based on the content of sand and mud components, the transport rate of the sandy sediment, and the transport rate of the muddy sediment; and calculating the bed elevation based on the total sediment transport rate according to the continuity equation of landform evolution and the total sediment transport rate;

[0031] a comparison unit, for comparing the spatial variation of the total sediment transport rate with a set value, and stopping the calculation when the spatial variation of the total sediment transport rate is less than or equal to the set value;

[0032] The landform characterization and prediction unit is used to characterize the landform under the stable form of the sand-mud mixed shallow sea negative topography landform in combination with the bed elevation and the total sediment transport rate, and to predict the trend of negative topography erosion or siltation, and to evaluate the landform stability of the sand-mud mixed shallow sea negative topography.

[0033] Furthermore, the calculation unit includes a sandy sediment transport rate calculation unit, and the specific calculation method is:

[0034]

[0035] Among them, C z is the Xie Cai coefficient, △ is the relative density of sediment and water, α is the correction coefficient, D 50 is the median particle size of sediment, U is the characteristic value of the flow velocity of the rising and falling tides, q s is the transport rate of sandy sediments.

[0036] Furthermore, the calculation unit includes a muddy sediment transport rate calculation unit, and the specific calculation method is:

[0037] q m =ED

[0038] Among them, q m is the transport rate of muddy sediments, E and D are the scouring amount and sedimentation flux of muddy sediments, respectively.

[0039] When τ>τ c hour,

[0040] When τ<τ c hour,

[0041] Where M is the scour coefficient, τ c is the sedimentation or starting critical shear stress of sediment, c is the sediment content of water, w s is the sediment settling velocity; τ is the water shear stress.

[0042] The beneficial effects of the present invention are:

[0043] (1) Innovation. This proposal proposes for the first time a prediction method for the stable morphology of one-dimensional sand-mud mixed shallow-sea negative topography. By calculating the total sediment transport rate, the discrete solution of the geomorphological evolution continuity equation is obtained, and the threshold value of the spatial variation of the sediment transport rate is determined to reach the stable morphology of the geomorphology. This overcomes the disadvantage that the traditional method is difficult to calculate the stable morphology of the geomorphology under complex terrain conditions. The percentage of sand and mud components in the sand-mud mixed sediment is considered in the sediment transport rate calculation equation, which ensures the accuracy of the model calculation results under different sediment characteristics.

[0044] (2) Versatility. This scheme not only considers both sandy and muddy sediment components, but also considers the spatial variation of their percentages and median sediment particle size with depth below the seabed. It adapts to the topography and dynamic characteristics of shallow sea negative terrain and is generally applicable to various estuaries, bays, and offshore environments.

[0045] (3) Simplicity. In view of the fact that shallow sea negative terrain is generally parallel to the tidal direction and its length is much greater than its width, the negative terrain is simplified into a one-dimensional form and solved using a one-dimensional analytical model. This eliminates the need to consider calculation areas unrelated to the negative terrain, greatly shortening the calculation time.

[0046] (4) Stability. Compared with the traditional upwind format or time-forward difference spatial center difference discretization format, the Lax explicit format is used to discretize the landform evolution continuity equation. This effectively overcomes the traditional method's tendency to cause cumulative errors and lead to calculation crashes, ensuring the stability of the long-term dynamic landform evolution calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0048] Figure 1 is a flow chart of the present method;

[0049] Figure 2 It is a schematic diagram of the change in the percentage of mud-sand components;

[0050] Figure 3 It is a schematic diagram of the change of the average median particle size of mud and sand;

[0051] Figure 4 This is a comparison chart between the simulated calculated value of the landform stability and the actual situation;

[0052] Figure 5 This is a schematic diagram of the system. DETAILED DESCRIPTION

[0053] In order to make the purpose, features, and advantages of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0054] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0055] Example 1

[0056] This embodiment takes the A deep trough on the north shore of the H City Bay as an example to disclose a method for predicting the stable form of sand-mud mixed shallow sea negative topography.

[0057] Deep Trough A is located in the front waters of Zhapu Town on the north shore of H City Bay. The water depth of H City Bay is generally around 10m. Deep Trough A is close to the north shore of H City Bay, running in a northeast-southwest direction, about 30km long, connected to Dushan Shoal in the west, and connected to Deep Trough B at the tailgate on the east side. The water depth can reach over 25m, making it a unique port and waterway resource, providing H City with a natural port access channel. H City Bay is a strong tidal estuary bay, and Deep Trough A has an average tidal range of 4.66m over many years. The tidal currents in this area are irregular semi-diurnal tidal currents, and the movement form is basically reciprocating flow. The flow direction is consistent with the channel direction, with high tide flowing to the west and low tide flowing to the east. The tidal current is dominated by high tide, and the measured average flow velocities of the maximum high tide and low tide can reach 2.0m / s and 1.6m / s respectively. Within 20 meters below the seabed in the deep trough, muddy sediments dominate, with a mud content ranging from 62% to 94% and a median particle size between 0.009mm and 0.048mm. Within 20-30 meters below the seabed, sandy sediments dominate, with a sand content ranging from 50% to 64% and a median particle size between 0.08mm and 0.1mm. It should be emphasized that the "median particle size" mentioned below refers to the median particle size of the mud-sand mixture, which ranges from 0.009mm to 0.1mm.

[0058] Through the analysis of the hydrological and topographic data and dynamic geomorphological characteristics of this area, in view of the characteristics of this area that is dominated by tidal action, with strong tidal power, tidal currents mainly in reciprocating flow, and the bottom sediments are sand-mud mixed type sediments, an analytical model of the A deep trough on the north bank of H City Bay was established, with a length of 50km, an initial water depth of 10m, and 600 nodes arranged, with a spacing of 10 to 50m between each node. The sediment transport rates mentioned below are all node sediment transport rates. Each node will have a different sediment transport rate due to different water depths and flow rates. The characteristic values of rising and falling tide velocities are 2.0m / s and 1.6m / s respectively. The characteristic values of rising tide duration and falling tide duration are assumed to be 5.5h and 7h. The characteristic value of flow velocity refers to the maximum flow velocity. The percentage content and median particle size of the sand and mud components of the sediments are determined by measured data. The specific values vary with the depth below the bed surface, such as Figure 2 and Figure 3 shown.

[0059] Based on the measured topographic data, the topographic data include the length of the negative topographic area, initial water depth, sea level elevation, tidal velocity, characteristic sand content, median sediment particle size, scour coefficient, sedimentation or starting critical shear stress, sedimentation velocity, etc.

[0060] like Figure 1 As shown, the calculation process of this method is as follows:

[0061] With the low point as the coordinate origin and the water flow direction as the horizontal coordinate, a coordinate system is established to construct the landform evolution continuity equation based on the calculation of the total sediment transport rate, as follows:

[0062]

[0063] Among them, z represents the seabed elevation, q sm represents the total sediment transport rate of sand-mud mixture during the tidal cycle, x is the horizontal axis value, and t is time. Equation (1) is discretized using the Lax explicit format to solve the bed elevation value:

[0064]

[0065] Among them, △t is the time step, △x is the spatial step of the horizontal axis, i and j are the i-th spatial step and j-th time step respectively, c b is a constant coefficient, which is set to 0.005. After obtaining the total sediment transport rate of the sand-mud mixture, the bed elevation is calculated according to equation (2). If the spatial variation of the total sediment transport rate does not reach the set value, the calculation of the total sediment transport rate and bed elevation for the next tidal cycle is continued.

[0066] The total sediment transport rate is calculated based on the percentage of sand-mud components, sediment settling or critical starting shear stress, water flow shear stress, and high tide and low tide velocities. The spatial variation of the total sediment transport rate is obtained based on the total sediment transport rate along the process. If the spatial variation of the total sediment transport rate is greater than the set value, the data is updated and the above steps are repeated to obtain the spatial variation of the total sediment transport rate for the next tidal cycle until the spatial variation of the total sediment transport rate is less than or equal to the set value.

[0067] First, the transport rate of sandy sediments is calculated based on the median sediment particle size, the relative density of sediment and water, and the characteristic value of the flow velocity of the rising and falling tides:

[0068]

[0069] Among them, C z is the Xie Cai coefficient, △ is the relative density of sediment and water, α is the correction coefficient, D 50 is the median particle size of sediment, C z ,△,α,D 50 are all constants and can be obtained by consulting data or sampling measurements. U is the characteristic value of the flow velocity at high tide or low tide, and q s is the transport rate of sandy sediments.

[0070] The transport rate of muddy sediments is calculated as follows:

[0071] q m =ED (4)

[0072] Among them, q m is the transport rate of muddy sediments, E and D are the scouring amount and sedimentation flux of sediments, respectively.

[0073] When τ>τ c hour,

[0074] When τ<τ c hour,

[0075] Where M is the scour coefficient, τ c is the sediment shear stress of the sediment, c is the sand content of the water body, w s is the sediment settling velocity of mud, M, τ c ,c,w s are all constants, which can be found by consulting the data; τ is the shear stress of the water flow, which is calculated as follows:

[0076]

[0077] where ρ w is the density of water, and g is the acceleration due to gravity.

[0078] The sandy sediment transport rate q calculated according to equations (3) and (4) is s and muddy sediment transport rate q m Calculate the total sediment transport rate:

[0079] q s m=φ s q s +φ m q m (8)

[0080] Among them, φ s 、φ m are the percentages of sandy and muddy sediments in sand-mud mixed sediments, respectively.

[0081] The transport patterns of sandy sediments are significantly different from those of muddy sediments. Considering the influence of different sediment components when calculating transport rates can make the results more accurate.

[0082] Based on the total sediment transport rate along the route, the spatial variation of the total sediment transport rate is calculated:

[0083] Δq sm =q sm，i -q sm，i+1 (9)

[0084] The subscript i is the node label.

[0085] When the spatial variation of the total sediment transport rate between two adjacent nodes △q sm When the spatial variation of the total sediment transport rate is less than or equal to the set value δ, the landform evolution reaches a stable state. If the spatial variation of the total sediment transport rate is greater than the set value, the calculation continues for the next tidal cycle. If the spatial variation of the total sediment transport rate is less than or equal to the set value, the surface landform evolution reaches a stable state and the calculation stops.

[0086] When the landform evolution reaches a stable state, the total sediment transport rate q sm Substitute into equations (1) and (2) to solve the bed elevation and characterize the landform.

[0087] The evolution of shallow-water negative topography is related to factors such as mountain spurs and islands, which change the local flow characteristics and thus affect sediment transport. Field observations show that the flow velocity is generally strongest between the mountain spurs and islands, and decreases with distance. The high tide and low tide velocities U are obtained from the measured data. f and ebb current velocity U e The distribution along the way. According to the situation of high tide or low tide, U f and U e Substitute U into equations (3) and (7) to calculate q smand τ. As the calculation time increases, the seabed elevation z of the negative terrain will gradually change, and accordingly, the tidal velocity will also change. The following formula is used to calculate the change in tidal velocity with seabed elevation:

[0088] High tide stage:

[0089] Low tide stage:

[0090] in, is the sea level elevation, is the water depth at the i-th node, △t is the time step, and the subscripts t and t+△t represent the time at time t and the next time step with an increased time step.

[0091] When the landform is not stable, the flow velocity is calculated using equation (10) or (11), and the transport rate is recalculated by updating U in equations (3) and (7).

[0092] When the landform is stable, GIS tools are used to describe the landform under the stable landform of shallow sea negative topography in combination with the bed elevation. The simulated stable landform is compared with the measured landform characteristics. The comparison between the calculated results and the measured data of the Zhapu deep trough on the north coast of H City Bay is shown in the figure. Figure 4 As shown, calculating only muddy or only sandy sediments is inaccurate. The calculated bed elevation at the deepest point is -25.2m, while the measured value is -24.9m. The model-predicted shoal and trough distribution is consistent with the actual situation, with a shallow shoal forming at Trough A and the deepest point of the trough at the front of Spur A. Considering the percentage of sand and mud components is closer to reality than calculating only sandy or muddy sediments. Based on these calculation results, combined with data such as bed elevation, average flow velocity, and water depth, the geomorphic stability of negative terrain can be assessed and the tendency of negative terrain erosion or siltation can be predicted.

[0093] Example 2

[0094] This embodiment provides a system for predicting the stable form of sand-mud mixed shallow sea negative topography, which is used to implement the method described in Example 1, such as Figure 5 Shown, including:

[0095] The model coordinate unit is used to establish a coordinate system and construct a continuity equation for landform evolution based on the topographic data of the sand-mud mixed shallow sea negative topography water area.

[0096] The data storage unit is used to calculate the transport rate of sandy sediments based on the median particle size of the sediments, the relative density of the sediments and water, and the characteristic values of the flow velocity of the rising and falling tides.

[0097] A calculation unit calculates the transport rate of muddy sediments based on the scouring flux and sedimentation flux of the sediments, calculates the scouring flux of the sediments based on the scouring coefficient, the sedimentation shear stress of the sediments, and the shear stress of the water flow, and calculates the sedimentation flux based on the sediment settling velocity, the sand content of the water body, the sedimentation shear stress of the sediments, and the shear stress of the water flow; calculates the total sediment transport rate based on the content of sand and mud components, the transport rate of the sandy sediments, and the transport rate of the muddy sediments in each tidal cycle, and calculates the bed elevation based on the total sediment transport rate according to the continuity equation of the landform evolution and the total sediment transport rate.

[0098] The comparison unit compares the spatial variation of the total sediment transport rate with a set value, and stops the calculation when the spatial variation of the total sediment transport rate is less than or equal to the set value.

[0099] The landform characterization and prediction unit is used to combine the bed elevation and the total sediment transport rate to characterize the landform under the stable form of negative landform, evaluate the landform stability of the sand-mud mixed shallow sea negative landform, and predict the trend of negative landform erosion or siltation.

[0100] The calculation unit includes a sandy sediment transport rate calculation unit, and the specific calculation method is as follows:

[0101]

[0102] Among them, C z is the Xie Cai coefficient, △ is the relative density of sediment and water, α is the correction coefficient, D 50 is the median particle size of sediment, C z ,△,α,D 50 are all constants and can be obtained by consulting data or sampling measurements. U is the characteristic value of the flow velocity at high tide or low tide, and q s is the transport rate of sandy sediments.

[0103] The calculation unit includes the mud sediment transport rate calculation unit, and the specific calculation method is as follows:

[0104] q m =ED

[0105] Among them, q m is the transport rate of muddy sediments, E and D are the scouring amount and sedimentation flux of sediments, respectively.

[0106] When τ>τ c hour,

[0107] When τ<τ c hour,

[0108] Where M is the scour coefficient, τ cis the sedimentation or starting critical shear stress of sediment, c is the sediment content of water, w s is the sediment settling velocity, M, τ c ,c,w s are all constants, which can be found by consulting the data; τ is the shear stress of the water flow, which is calculated as follows:

[0109]

[0110] where ρ w is the density of water, and g is the acceleration due to gravity.

[0111] The calculation unit includes the total sediment transport rate calculation unit, and the specific calculation method is:

[0112] q sm =φ s q s +φ m q m

[0113] Among them, φ s 、φ m are the percentages of sandy and muddy sediments in sand-mud mixed sediments, respectively.

[0114] The calculation unit also calculates the spatial variation of the total sediment transport rate. The specific calculation method is:

[0115] Δq sm =q sm，i -q sm，i+1

[0116] The subscript i is the node label.

[0117] The calculation unit also includes a bed elevation calculation unit, which uses the continuous equation of landform evolution

[0118] and its discrete

[0119]

[0120] Among them, z represents the seabed elevation, q sm represents the total sediment transport rate of sand-mud mixture within the tidal cycle, x is the horizontal axis value, t is the time; △t is the time step, △x is the spatial step of the horizontal axis, i and j are the i-th spatial step and the j-th time step respectively, c b is a constant coefficient, which is set to 0.005. The bed elevation is calculated using the calculated total sediment transport rate.

[0121] After calculating the spatial variation of total sediment transport rate and bed elevation, the calculation results are input into the comparison unit. When the spatial variation of total sediment transport rate △q between two adjacent nodes issm When the spatial variation of the total sediment transport rate is less than or equal to the set value δ, the landform evolution reaches a stable state. If the spatial variation of the total sediment transport rate is greater than the set value, the flow velocity data is updated, and the calculation process returns to the calculation unit to continue the cycle calculation for the next tidal cycle. If the spatial variation of the total sediment transport rate is less than or equal to the set value, the landform evolution reaches a stable state and the calculation stops.

[0122] After stopping the operation, the landform characterization and prediction unit combines the bed elevation and the total sediment transport rate to characterize the landform under the stable form of the sand-mud mixed shallow sea negative landform, evaluate the landform stability of the negative landform, and predict the trend of negative landform erosion or siltation.

[0123] In the several embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative. For example, the division of the units described is merely a logical functional division. In actual implementation, other division methods may be used, such as combining or integrating multiple units or components into another device, or ignoring or not implementing certain features.

[0124] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0125] In particular, according to the embodiments disclosed in the present invention, the process described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments of the present disclosure include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network through the communication part, and / or installed from a removable medium. When the computer program is executed by the central processing unit (CPU), the above-mentioned functions defined in the method of the present application are executed. It should be noted that the computer-readable medium mentioned above in the present application can be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium can be, for example, but not limited to, a system, device or device of an electrical, magnetic, optical, electromagnetic, infrared segment, or semiconductor, or any combination of the above.

[0126] The flow charts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the system, method and computer program product according to various embodiments of the present invention. In this regard, each box in the flow chart or block diagram can represent a module, program segment, or a part of code, and the module, program segment, or a part of code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order than that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart, can be implemented with a dedicated hardware-based system that performs the specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

Claims

1. A method for predicting the stable morphology of sand-mud mixed shallow sea negative topography, characterized in that: The following steps are involved: Based on the topographic data along the shallow sea negative terrain, a continuity equation for landform evolution based on the calculation of the transport rate of sand-mud mixed sediments was constructed; The transport rate of sandy sediments is calculated based on the median sediment particle size, the relative density of sediment to water, and the tidal current velocity; Calculating the scouring flux of the sediment based on the scouring coefficient, sediment settling or starting critical shear stress, and water flow shear stress; calculating the settling flux based on the sediment settling velocity, water body sand content, sediment settling or starting critical shear stress, and water flow shear stress; and calculating the transport rate of muddy sediment based on the scouring flux and settling flux of the sediment; For each tidal cycle, a total sediment transport rate is calculated based on the percentage of sand-mud components, the transport rate of the sandy sediments, and the transport rate of the muddy sediments, and a bed elevation change is calculated based on a geomorphic evolution continuity equation and the total sediment transport rate. The spatial variation of the total sediment transport rate in each tidal cycle is obtained based on the total sediment transport rate along the course. If the spatial variation of the total sediment transport rate is greater than a set value, the data is updated and a new spatial variation of the total sediment transport rate is calculated. The calculation of the total sediment transport rate and bed elevation is stopped until the spatial variation of the total sediment transport rate is less than or equal to the set value. Combined with the bed elevation, the landform under the stable form of shallow sea negative topography is depicted, the landform stability of the negative topography is evaluated, and the erosion or siltation trend of the negative topography is predicted.

2. The method for predicting the stable morphology of sand-mud mixed shallow sea negative topography according to claim 1, characterized in that: Calculate the transport rate of sandy sediments, including: Among them, C z is the Xie Cai coefficient, △ is the relative density of sediment and water, α is the correction coefficient, D 50 is the median particle size of sediment, U is the characteristic value of the flow velocity of the rising and falling tides, q s is the transport rate of sandy sediments.

3. The method for predicting the stable morphology of sand-mud mixed shallow sea negative topography according to claim 1, characterized in that: Calculate the transport rate of muddy sediments, including: q m =E-D Among them, q m is the transport rate of muddy sediments, E and D are the scouring amount and sedimentation flux of sediments, respectively. When τ>T e hour, When τ<τ c hour, Where M is the scour coefficient, τ c is the sedimentation or starting critical shear stress of sediment, c is the sediment content of water, w s is the sediment settling velocity, and τ is the shear stress of the water flow.

4. The method for predicting the stable morphology of sand-mud mixed shallow sea negative topography according to claim 3, characterized in that: The calculation method of the water flow shear stress is: Among them, ρ w is the water density, g is the acceleration due to gravity, U is the flow velocity at high tide or low tide, C z It is Xie Cai coefficient.

5. The method for predicting the stable form of sand-mud mixed shallow sea negative topography according to claim 4, characterized in that: Calculate the total sediment transport rate as: what sm =φ s what s +φ m what m Among them, φ s 、φ m are the percentages of sandy and muddy sediments in sand-mud mixed sediments, respectively, and q s ,q m are the transport rates of sandy sediments and muddy sediments, respectively.

6. The method for predicting the stable morphology of sand-mud mixed shallow sea negative topography according to claim 1, characterized in that: Calculating the bed elevation also includes: discretizing the landform evolution continuity equation using the Lax explicit format.

7. The method for predicting the stable form of sand-mud mixed shallow sea negative topography according to claim 1, characterized in that: Establishing the coordinate system specifically includes: taking the low point of the negative terrain as the coordinate origin, and taking the water flow direction of the negative terrain as the horizontal coordinate.

8. A system for predicting the stable morphology of sand-mud mixed shallow sea negative topography, characterized by: include: Model coordinate unit, used to establish a coordinate system and construct the continuity equation of landform evolution based on the topographic data of negative topographic water areas; a data storage unit for storing negative topographic data, wherein the negative topographic data includes sediment median particle size, relative density of sediment to water, characteristic values of flow velocity at high and low tides, scour coefficient, sediment settling or starting critical shear stress, water flow shear stress, sediment settling velocity, and water body sand content; a calculation unit for calculating the transport rate of sandy sediments based on the median particle size of the sediments, the relative density of the sediments and water, and the characteristic value of the flow velocity of the rising and falling tides; calculating the transport rate of muddy sediments based on the scouring flux and the settling flux of the sediments, calculating the scouring flux of the sediments based on the scouring coefficient, the settling or starting critical shear stress of the sediments, and the shear stress of the water flow, and calculating the settling flux based on the sediment settling velocity, the sand content of the water body, the settling or starting critical shear stress of the sediments, and the shear stress of the water flow; calculating the total sediment transport rate for each tidal cycle based on the content of sand and mud components, the transport rate of the sandy sediments, and the transport rate of the muddy sediments, and calculating the bed elevation based on the total sediment transport rate according to the continuity equation of the landform evolution; a comparison unit, for comparing the spatial variation of the total sediment transport rate with a set value, and stopping the calculation when the spatial variation of the total sediment transport rate is less than or equal to the set value; The landform characterization and prediction unit is used to characterize the landform under the stable form of shallow sea negative landform by combining the bed elevation and the total sediment transport rate, evaluate the landform stability of the negative landform, and predict the trend of negative landform erosion or siltation.

9. The system for predicting the stable form of sand-mud mixed shallow sea negative topography according to claim 8, characterized in that: The calculation unit includes a sandy sediment transport rate calculation unit, and the specific calculation method is: Among them, C z is the Xie Cai coefficient, △ is the relative density of sediment and water, α is the correction coefficient, D 50 is the median particle size of sediment, U is the characteristic value of the flow velocity of the rising and falling tides, q s is the transport rate of sandy sediments.

10. The system for predicting the stable form of sand-mud mixed shallow sea negative topography according to claim 8, characterized in that: The calculation unit includes a mud sediment transport rate calculation unit, and the specific calculation method is: q m =E-D Among them, q m is the transport rate of muddy sediments, E and D are the scouring amount and sedimentation flux of sediments, respectively; When τ>τ c hour, When τ<τ c hour, Where M is the scour coefficient, τ c is the sedimentation or starting critical shear stress of sediment, c is the sediment content of water, w s is the sediment settling velocity, and τ is the shear stress of the water flow.

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