An Asymmetric Calculation Method for Water and Sediment Distribution in the Cross-Section of Wandering River Channels

Abstract

This application relates to the field of water and sediment distribution calculation technology, and provides an asymmetric calculation method for water and sediment distribution in a wandering river cross section. The method includes: dividing the river cross section into two parts based on measured topographic data of the river cross section, with the centerline of the river cross section under the flat flow as the axis; obtaining water and sediment factors for the two pre-divided parts of the river cross section based on the constructed water and sediment lateral distribution model; and obtaining an asymmetric index of water and sediment distribution in the river cross section based on the water and sediment factors of the two parts of the river cross section, thereby quantitatively describing the variation law of water and sediment factors along the lateral distribution of the river cross section under finite control boundary conditions. This calculation method is not limited by regional and topographic factors and can be widely used.

Description

Technical Field

[0001] This application relates to the field of water and sediment distribution calculation technology, and in particular to an asymmetric calculation method for water and sediment distribution in the cross-section of a wandering river channel. Background Technology

[0002] In its natural state, meandering river channels exhibit complex and variable water and sediment transport conditions as well as boundary conditions. The channels are dotted with sandbars, crisscrossed by numerous distributaries, and shoals of varying sizes and shapes, with the positions of shoals and water frequently shifting. After river regulation projects are constructed, while improving and controlling the river's course, new riverbed morphologies are created. Particularly in sections where river regulation is well-developed and the riverbed is well-adjusted, the impact of the projects on the river's cross-section, the resulting changes in cross-sectional water and sediment transport, and riverbed deformation lead to a significantly different evolution of the river course compared to its natural state.

[0003] Following the extensive river regulation projects constructed in the lower reaches of the Yellow River, the distribution of various water and sediment factors across the river cross-section has been disrupted, resulting in significant changes compared to natural conditions. These changes, in turn, influence the adjustment of the river morphology. Therefore, studying the asymmetric variations in the lateral distribution of water and sediment factors across the river cross-section under finite control boundary conditions is crucial for understanding the evolution of river morphology under asymmetric conditions. Current research on how the distribution of water and sediment factors in the river cross-section changes after the construction of river regulation projects largely remains at the qualitative descriptive level.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this application is to provide an asymmetric calculation method for water and sediment distribution in the cross-section of a wandering river channel, so as to solve or alleviate the problems existing in the prior art.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] This application provides an asymmetric method for calculating water and sediment distribution in the cross-section of a wandering river channel, including:

[0008] Based on the constructed water and sediment lateral distribution model, the water and sediment factors of the two pre-divided parts of the river channel cross section are obtained; wherein, there are multiple water and sediment lateral distribution models;

[0009] Based on the water and sediment factors of the two parts of the river channel cross section, an asymmetric index of the water and sediment distribution of the river channel cross section is obtained, wherein the asymmetric index is used to characterize the asymmetric distribution characteristics of the water and sediment factors along the transverse direction of the river channel cross section.

[0010] Preferably, the water and sediment factor includes the average flow velocity of the river channel cross-section.

[0011] Correspondingly,

[0012] Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two parts of the river channel cross-section are obtained, specifically:

[0013] Based on the pre-acquired water flow data of the river cross section, and based on the constructed velocity distribution model along the lateral direction, the average velocity of the two parts of the river cross section is obtained respectively.

[0014] The lateral velocity distribution model is as follows:

[0015]

[0016]

[0017] In the formula, V represents the average flow velocity of the river channel cross section, in m / s; V i C1 represents the flow velocity at any point in the cross-section of the river channel, in m / s; C1 represents the first cross-sectional shape coefficient, obtained by mass conservation; h represents the average water depth of the cross-section of the river channel, in m; h i Q represents the water depth at any point on the cross-section of the river channel, in meters (m); Q represents the average flow rate of the cross-section of the river channel, in cubic meters per second (m³). 3 / s; a and b are the distances between the starting points of the two ends of the river channel cross section along the river width, and b > a; y is the lateral coordinate of the integral from a to b.

[0018] Preferably, the asymmetric index of water and sediment distribution in the cross-section of the wandering river channel includes a first asymmetric index, which characterizes the asymmetric distribution of the average flow velocity along the transverse direction of the river channel cross-section.

[0019] Correspondingly,

[0020] The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows:

[0021] According to the formula:

[0022]

[0023] The first asymmetric index is calculated;

[0024] In the formula, AS V V is the first asymmetric index; 大 The average flow velocity, in m / s, is the flow velocity on the side with the larger area of ​​the two pre-divided sections of the river channel cross-section; V小 The average flow velocity is the smaller of the two pre-divided sections of the river channel cross-section; the unit is m / s.

[0025] Preferably, the water and sediment factor includes the sediment content of the river channel cross-section.

[0026] Correspondingly,

[0027] Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two parts of the river channel cross-section are obtained, specifically:

[0028] Based on the pre-acquired water flow data of the river cross section, and based on the sediment concentration distribution model along the lateral direction, the sediment concentration of the two parts of the river cross section is obtained respectively.

[0029] The lateral distribution model of the sediment content is as follows:

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037] In the formula, S represents the sediment content of the river channel cross-section, with units of kg / m³. 3 S i The sediment content at any point on the cross-section of the river channel is expressed in kg / m³. 3 V represents the average flow velocity of the river channel cross-section, in m / s; V i The velocity at any point in the cross-section of the river channel is expressed in m / s; h represents the average water depth of the cross-section of the river channel, expressed in m. i C2 represents the water depth at any point on the cross-section of the river channel, in meters; C2 is the second cross-sectional shape coefficient, obtained by the sediment conservation solution; Q is the average flow rate of the cross-section of the river channel, in cubic meters per second. 3 / s;q i The unit width discharge at any point on the cross-section of the river channel is expressed in m³. 2 / s;ω s ω0 represents the settling velocity of sediment particles in the river channel, in m / s; ω0 represents the settling velocity of sediment particles in clear water, in m / s; d cpω represents the average suspended sediment particle size of the river channel cross section, in meters; p For a particle size of d cp The settling velocity of uniform sand in clear water is expressed in m / s; ν is the kinematic viscosity coefficient, expressed in m³ / s. 2 / s; k is the Karman constant; u * The average frictional velocity of the river channel cross section is expressed in m / s. Where J is the drop, taken as... g is the acceleration due to gravity; S v S represents the volumetric sand content. v =S / 2650;d 50 γ is the median suspended sediment particle size of the river channel cross section, in meters; s This refers to the bulk density of sediment particles in the river channel, expressed in N / m³. 3 γ is the specific gravity of water, in N / m³. 3 a and b are the distances between the starting points of the two ends of the river channel cross section along the river width, and b > a; y is the lateral coordinate of the integral from a to b.

[0038] Preferably, the asymmetric index of water and sediment distribution in the cross-section of the wandering river channel includes a second asymmetric index, which characterizes the asymmetric distribution of sediment concentration along the cross-section of the river channel.

[0039] Correspondingly,

[0040] The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows:

[0041] According to the formula:

[0042]

[0043] The second asymmetry index is calculated;

[0044] In the formula, AS s S is the second asymmetric index; 大 The sediment content of the larger area side of the two pre-divided sections of the river channel cross-section; S 小 The sediment content of the smaller side of the two pre-divided sections of the river channel cross-section.

[0045] Preferably, the water and sediment factor includes the average suspended sediment particle size of the river channel cross-section.

[0046] Correspondingly,

[0047] Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two parts of the river channel cross-section are obtained, specifically:

[0048] Based on the pre-acquired water flow data of the river channel cross section, and based on the suspended sediment composition distribution model along the lateral direction, the average suspended sediment average particle size of the two parts of the river channel cross section is obtained.

[0049] The lateral distribution model of the suspended sediment composition is as follows:

[0050]

[0051]

[0052] In the formula, d cp The average suspended sediment particle size of the river channel cross section is expressed in meters (m); d cpi The average suspended sediment particle size at any point on the river channel cross-section is expressed in meters (m); S represents the sediment content of the river channel cross-section, expressed in kg / m³. 3 S i The sediment content at any point on the cross-section of the river channel is expressed in kg / m³. 3 V represents the average flow velocity of the river channel cross-section, in m / s; V i The velocity at any point in the cross-section of the river channel is expressed in m / s; C3 is the morphology coefficient of the third cross-section, obtained by the sediment conservation solution; q i The unit width discharge at any point on the cross-section of the river channel is expressed in m³. 2 / s; Q is the average flow rate of the river cross-section, in m³ / s. 3 / s; a and b are the distances between the starting points of the cross-section of the river along the width of the river, and b > a; y is the lateral coordinate of the integral from a to b.

[0053] Preferably, the asymmetric index of water and sediment distribution in the cross-section of the wandering river channel includes a third asymmetric index, which characterizes the asymmetric distribution of the average suspended sediment particle size along the cross-section of the river channel.

[0054] Correspondingly,

[0055] The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows:

[0056] According to the formula:

[0057]

[0058] The third asymmetry index is calculated;

[0059] In the formula, AS dcp The third asymmetric index; d cp大The average suspended sediment particle size, in meters, is the larger side of the two pre-divided sections of the river channel cross-section; d cp小 The average suspended sediment particle size is the smaller side of the two pre-divided sections of the river channel cross-section, expressed in meters.

[0060] Preferably, the water and sediment factor includes the sediment-carrying capacity of the river channel cross-section.

[0061] Correspondingly,

[0062] Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two parts of the river channel cross-section are obtained, specifically:

[0063] Based on the pre-acquired water flow data of the river cross section, and based on the water flow sediment carrying capacity model along the transverse direction, the water flow sediment carrying capacity of the two parts of the river cross section is obtained respectively.

[0064] The lateral distribution model of the sediment-carrying force of the water flow is as follows:

[0065]

[0066] In the formula, S * The sediment-carrying capacity of the water flow is expressed in kg / m³. 3 V represents the average flow velocity of the river channel cross section, in m / s; S v d represents the volumetric sediment content; h represents the average water depth of the river channel cross-section in meters; d represents the average water depth of the river channel cross-section in meters. 50 ω represents the median suspended sediment particle size of the river channel cross-section, in meters; s γ represents the settling velocity of sediment particles in the river channel, in m / s; k is the KAMAN constant; γ s The bulk density of sediment particles in the river channel (N / m3); γ m The specific weight of turbid water, expressed in N / m³. 3 g is the acceleration due to gravity, taken as 9.8 m / s².

[0067] Preferably, the asymmetric index of water and sediment distribution in the cross-section of the wandering river channel includes a fourth asymmetric index, which characterizes the asymmetric distribution of the sediment-carrying capacity of the water flow along the cross-section of the river channel.

[0068] Correspondingly,

[0069] The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows:

[0070] According to the formula:

[0071]

[0072] The fourth asymmetry index is calculated;

[0073] In the formula, S is the fourth asymmetric index; *大 The sediment-carrying capacity of the water flow is the larger of the two pre-divided sections of the river channel cross-section, measured in kg / m². 3 S *小 The sediment-carrying capacity of the water flow is the smaller of the two pre-divided sections of the river channel cross-section, measured in kg / m². 3 .

[0074] Preferably, the river channel cross-section is pre-divided into two parts, the pre-division specifically being:

[0075] Based on the measured topographic data of the river cross section, the river cross section is divided into two parts with the centerline of the river cross section under the flat flow as the axis.

[0076] Beneficial effects:

[0077] This application provides an asymmetric calculation method for water and sediment distribution in a wandering river cross-section. Based on measured topographic data of the river cross-section, the cross-section is divided into two parts with the centerline under flat-shoal flow as the axis. Based on a constructed lateral water and sediment distribution model, water and sediment factors for the two pre-divided parts of the cross-section are obtained. Based on these two parts, an asymmetric index of water and sediment distribution in the cross-section is derived. This quantitatively describes the variation law of water and sediment factors along the lateral distribution of a river cross-section under finite control boundary conditions. This calculation method is not limited by geographical or topographical factors and can be widely applied.

[0078] The lateral velocity distribution model provided in this application can accurately calculate the lateral velocity distribution pattern before, during, and after the flood season. The model considers a wide range of factors and is easy to apply.

[0079] The lateral sediment concentration distribution model provided in this application not only considers hydraulic factors and sediment concentration magnitude, but also introduces a suspended sediment index to reflect the coarseness of the suspended sediment composition. Based on this model, the lateral sediment concentration distribution pattern of non-floodplain floods can be calculated relatively accurately, and it can also calculate the lateral sediment concentration distribution pattern of the main channel, floodplain, and mixing zone of floodplain floods. This lateral sediment concentration distribution model is applicable to both general sediment-laden flows and high-sediment-laden flows, and the formula considers a relatively comprehensive range of factors, making it convenient to apply.

[0080] Based on the lateral distribution model of suspended sediment composition provided in this application, the average suspended sediment particle size of the river channel cross section is calculated. For different suspended sediment particle sizes and different sediment contents, the average suspended sediment particle size calculated based on the lateral distribution model of suspended sediment composition can fit well with the measured data. Compared with traditional methods, the accuracy is significantly improved.

[0081] The lateral distribution model of sediment-carrying capacity provided in this application is applicable to both general water flow and high sediment-laden water flow, and has strong universality. Attached Figure Description

[0082] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein:

[0083] Figure 1 This is a flowchart illustrating an asymmetric calculation method for water and sediment distribution in a cross-section of a wandering river channel, according to some embodiments of this application.

[0084] Figure 2 A schematic diagram verifying the measured data before, after, and during the flood season and the calculation results of the flow velocity distribution model along the lateral direction provided for some embodiments of this application;

[0085] Figure 3 A schematic diagram verifying the measured data and calculation results of the sediment concentration distribution model with low sediment concentration provided for some embodiments of this application;

[0086] Figure 4 A schematic diagram verifying the measured data of medium-level sediment concentration and the calculation results of the sediment concentration distribution model along the lateral direction provided for some embodiments of this application;

[0087] Figure 5 A schematic diagram verifying the measured data and calculation results of the sediment concentration distribution model along the lateral direction for some embodiments of this application;

[0088] Figure 6 A schematic diagram verifying the measured data and calculation results of the suspended sediment composition distribution model along the lateral direction provided for some embodiments of this application. Detailed Implementation

[0089] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present application encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0090] Figure 1 This is a flowchart illustrating an asymmetric calculation method for water and sediment distribution in a wandering river cross-section, according to some embodiments of this application; Figure 1 As shown, the asymmetric calculation method for water and sediment distribution in the cross-section of this wandering river channel includes:

[0091] Step S101: Based on the constructed water and sediment lateral distribution model, obtain the water and sediment factors of the two pre-divided parts of the river channel cross section; there are multiple water and sediment lateral distribution models.

[0092] In some optional embodiments, in step S101, the pre-division of the river cross-section into two parts specifically involves: based on the measured topographic data of the river cross-section, using the centerline of the river cross-section under the flat-shoal flow as the axis, dividing the river cross-section into two parts. Understandably, here, asymmetry refers to dividing the river cross-section into left and right sides, i.e., into two parts, using the centerline of the river cross-section under the flat-shoal flow as the axis. The asymmetry is quantitatively described by taking the square root of the ratio of the areas of the physical quantities (water and sediment factors) on both sides. In the calculation, the index of the side with the larger area after division is used as the numerator, and the index of the side with the smaller area is used as the denominator.

[0093] In some alternative embodiments, the water and sediment factors include the average flow velocity of the river channel cross section. Correspondingly, based on the constructed water and sediment lateral distribution model, the water and sediment factors of the two parts of the river channel cross section are obtained. Specifically, based on the pre-acquired water flow data of the river channel cross section, the average flow velocity of the two parts of the river channel cross section is obtained respectively based on the constructed flow velocity lateral distribution model.

[0094] The flow velocity distribution model along the lateral direction is as follows:

[0095]

[0096]

[0097] In the formula, V represents the average flow velocity of the river channel cross section, with units of m / s; V iThe velocity at any point in the river cross-section is expressed in m / s; C1 represents the shape coefficient of the first cross-section, obtained by mass conservation; h represents the average water depth of the river cross-section, in meters. i Q represents the water depth at any point on the river cross-section, in meters (m); Q represents the average flow rate of the river cross-section, in cubic meters per second (m³). 3 / s; a and b are the distances between the starting points of the cross-section of the river along the width of the river, and b > a; y is the lateral coordinate of the integral from a to b.

[0098] In some optional embodiments, the water and sediment factors include the sediment concentration of a river channel cross-section. Correspondingly, based on the constructed water and sediment lateral distribution model, the water and sediment factors for two parts of the river channel cross-section are obtained. Specifically, based on the pre-acquired flow data of the river channel cross-section, the sediment concentration of the two parts of the river channel cross-section is obtained respectively, according to the sediment concentration lateral distribution model. The sediment concentration lateral distribution model is as follows:

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106] In the formula, S represents the sediment content of the river channel cross section, with units of kg / m³. 3 S i The sediment content at any point on the cross-section of the river channel, expressed in kg / m³. 3 V represents the average flow velocity across the river channel cross-section, measured in m / s; V i The velocity at any point in the river cross-section is expressed in m / s; h represents the average water depth of the river cross-section, expressed in m. i C1 represents the water depth at any point on the river channel cross-section, in meters (m); C2 is the second cross-sectional shape coefficient, obtained from the sediment conservation solution; Q is the average discharge of the river channel cross-section, in cubic meters per second (m³ / s); q i The unit width discharge at any point on the cross-section of the river channel, in meters. 2 / s;ω s ω0 represents the settling velocity of sediment particles in the river channel, in m / s; ω0 represents the settling velocity of sediment particles in clear water, in m / s; d cp ω represents the average suspended sediment particle size of the river channel cross section, in meters;p For a particle size of d cp The settling velocity of uniform sand in clear water is expressed in m / s; ν is the kinematic viscosity coefficient, expressed in m³ / s. 2 / s; k is the Karman constant; u * The average frictional velocity across the river channel cross-section is expressed in m / s. Where J is the drop, taken as... g is the acceleration due to gravity; S v S represents the volumetric sand content. v =S / 2650;d 50 γ is the median suspended sediment diameter of the river channel cross section, in meters; s This refers to the bulk density of sediment particles in the river channel, expressed in N / m³. 3 γ is the specific gravity of water, in N / m³. 3 a and b are the distances between the starting points of the cross-section of the river along the width of the river, and b > a; y is the lateral coordinate of the integral from a to b.

[0107] Analysis of extensive measured data revealed significant differences in sediment transport capacity along the river width (lateral direction) of meandering channels. This resulted in marked variations in sediment concentration distribution along the river width during sediment transport. The lateral distribution pattern of sediment concentration is not only related to hydraulic factors and sediment concentration magnitude but also closely correlated with suspended sediment composition: the finer the suspended sediment composition, the more uniform the lateral sediment concentration distribution. In this embodiment, in addition to incorporating sediment concentration from the river cross-section, a suspension index was introduced to reflect the fineness of the suspended sediment composition. Based on this, the aforementioned lateral sediment concentration distribution model was constructed.

[0108] In some alternative embodiments, the water and sediment factors include the average suspended sediment particle size of the river channel cross section. Correspondingly, based on the constructed water and sediment lateral distribution model, the water and sediment factors of the two parts of the river channel cross section are obtained. Specifically, based on the pre-acquired water flow data of the river channel cross section, the average suspended sediment particle size of the two parts of the river channel cross section is obtained based on the suspended sediment composition lateral distribution model.

[0109] The lateral distribution model of suspended sediment composition is as follows:

[0110]

[0111]

[0112] In the formula, d cp The average suspended sediment particle size of the river channel cross section, in meters; d cpi The average suspended sediment particle size at any point on the river channel cross-section is expressed in meters (m); S represents the sediment content of the river channel cross-section, expressed in kg / m³. 3 S i The sediment content at any point on the cross-section of the river channel, expressed in kg / m³.3 V represents the average flow velocity across the river channel cross-section, measured in m / s; V i The velocity at any point in the river channel cross-section is expressed in m / s; C3 is the third cross-sectional shape coefficient, obtained from the sediment conservation solution; q i Let be the unit width flow rate at any point on the river cross-section, in m² / s; Q be the average flow rate of the river cross-section, in m³ / s; a and b be the distance between the starting points of the river cross-section along the width direction, where b > a; y be the lateral coordinate of the integral from a to b.

[0113] In some optional embodiments, the water and sediment factors include the sediment-carrying capacity of the river channel cross section. Correspondingly, based on the constructed water and sediment lateral distribution model, the water and sediment factors of the two parts of the river channel cross section are obtained. Specifically, based on the pre-acquired water flow data of the river channel cross section, the sediment-carrying capacity of the two parts of the river channel cross section is obtained respectively based on the sediment-carrying capacity model along the lateral direction.

[0114] The lateral distribution model of sediment-carrying capacity of water flow is as follows:

[0115]

[0116] In the formula, S * The sediment-carrying capacity of water flow, measured in kg / m³ 3 V represents the average flow velocity across the river cross-section, in m / s; S v d represents the volumetric sediment content; h represents the average water depth of the river channel cross section, in meters; d represents the volumetric sediment content. 50 ω represents the median suspended sediment particle size of the river channel cross section, in meters; s γ represents the settling velocity of sediment particles in the river channel, in m / s; k is the KAMAN constant; γ s The bulk density of sediment particles in the river channel (N / m³) 3 );γ m The specific weight of turbid water, expressed in N / m³. 3 g is the acceleration due to gravity, taken as 9.8 m / s².

[0117] Step S102: Based on the water and sediment factors of the two parts of the river channel cross section, obtain the asymmetric index of water and sediment distribution in the river channel cross section. The asymmetric index is used to characterize the asymmetric distribution characteristics of water and sediment factors along the transverse direction of the river channel cross section.

[0118] In some optional embodiments, the asymmetric index of water and sediment distribution in a wandering channel cross-section includes a first asymmetric index, which characterizes the asymmetric distribution of average flow velocity along the transverse direction of the channel cross-section. Correspondingly, based on the water and sediment factors of the two parts of the channel cross-section, the asymmetric index of water and sediment distribution in the channel cross-section is obtained, specifically as follows:

[0119] According to the formula:

[0120]

[0121] The first asymmetric index was calculated;

[0122] In the formula, ASV The first asymmetric index; V 大 The average flow velocity, expressed in m / s, is the flow velocity on the larger side of a pre-divided cross-section of a river channel; V 小 The average flow velocity on the smaller side of a pre-divided cross-section of a river channel; the unit is m / s.

[0123] In some alternative embodiments, the asymmetric index of water and sediment distribution in the cross-section of a wandering river channel includes a second asymmetric index, which characterizes the lateral asymmetric distribution of sediment concentration along the river channel cross-section; correspondingly,

[0124] Based on the water and sediment factors of the two parts of the river channel cross-section, the asymmetric index of water and sediment distribution in the river channel cross-section is obtained, specifically:

[0125] According to the formula:

[0126]

[0127] The second asymmetric index was calculated;

[0128] In the formula, AS s The second asymmetric index; S 大 The sediment content of the larger area side of the two pre-divided sections of the river channel cross-section; S 小 The sediment content of the smaller side of the two pre-divided sections of a river channel cross-section.

[0129] In some optional embodiments, the asymmetric index of water and sediment distribution in a wandering channel cross-section includes a third asymmetric index, which characterizes the lateral asymmetric distribution of the average suspended sediment size along the channel cross-section. Correspondingly, based on the water and sediment factors of the two parts of the channel cross-section, the asymmetric index of water and sediment distribution in the channel cross-section is obtained, specifically as follows:

[0130] According to the formula:

[0131]

[0132] The third asymmetric index was calculated;

[0133] In the formula, AS dcp The third asymmetric index; d cp大The average suspended sediment particle size, in meters, is the larger of the two pre-divided sections of a river channel cross-section. cp小 The average suspended sediment particle size, in meters, is the smaller side of the two pre-divided sections of a river channel cross-section.

[0134] In some alternative embodiments, the asymmetric index of water and sediment distribution in the cross-section of a wandering river channel includes a fourth asymmetric index, which characterizes the lateral asymmetric distribution of sediment-carrying capacity along the river channel cross-section; correspondingly,

[0135] Based on the water and sediment factors of the two parts of the river channel cross-section, the asymmetric index of water and sediment distribution in the river channel cross-section is obtained, specifically:

[0136] According to the formula:

[0137]

[0138] The fourth asymmetric index was calculated;

[0139] In the formula, The fourth asymmetric index; S *大 The sediment-carrying capacity of the water flow on the side with the larger area in the two pre-divided sections of the river channel cross-section is expressed in kg / m². 3 S *小 The sediment-carrying capacity of the water flow on the smaller side of the two pre-divided sections of the river channel cross-section, measured in kg / m². 3 .

[0140] In some optional embodiments, after calculating the asymmetric index of water and sediment distribution in the river cross section, the method further includes: based on the lateral distribution model of water flow carrying capacity, and according to the asymmetric index of water and sediment distribution in the river cross section, verifying the calculation results of the lateral distribution model of flow velocity, the lateral distribution model of sediment concentration, and the lateral distribution model of suspended sediment composition.

[0141] In this embodiment of the application, the calculation results of the flow velocity distribution model, sediment concentration distribution model, and suspended sediment composition distribution model are verified based on the measured data of a certain river channel.

[0142] In a specific example, the calculation results of the velocity distribution model along the transverse direction were verified. The average velocity range of the river cross section in the measured data was 0.10–3.56 m / s, and the measured data range covered the pre-flood, post-flood, and flood season periods. The measured data were compared with the calculation results of the velocity distribution model along the transverse direction. Figure 2 As shown, by Figure 2 It can be seen that, based on the lateral velocity distribution model, the average lateral velocity distribution pattern of the river cross section before, during, and after the flood season can be accurately calculated. This model considers a wide range of factors and is easy to apply.

[0143] In another specific example, the calculation results of the sediment concentration distribution model along the lateral direction were verified. The average sediment concentration of the river cross section in the measured data ranged from 3 to 480 kg / m³. 3 This includes measured data from floodplain floods and non-floodplain floods. The average sediment load of the river channel cross-section in the measured data is compared with the calculation results from the sediment load distribution model along the lateral direction. Figure 3 , Figure 4 , Figure 5 As shown, from Figure 3 , Figure 4 , Figure 5 It can be seen that the lateral distribution model of sediment concentration can accurately calculate the lateral distribution of sediment concentration in non-floodplain floods, as well as the lateral distribution of sediment concentration in the main channel, floodplain, and mixing zone of floodplain floods. This lateral distribution model of sediment concentration is applicable to both general sediment-laden flows and high-sediment-laden flows, and it considers a wide range of factors, making it convenient to use.

[0144] In another specific example, measured suspended sediment gradation data were used. After correction using the suspended sediment gradation correction method, the average suspended sediment particle size corresponding to the measured data was calculated. Based on this, the suspended sediment evaluation particle size calculated by the suspended sediment composition lateral distribution model was verified. The average suspended sediment particle size range of the river channel cross-section was 0.01–0.06 mm. The average suspended sediment particle size calculated from the measured data was compared with the calculation results of the suspended sediment composition lateral distribution model. Figure 6 As shown, from Figure 6 It can be seen that, for different suspended sand particle sizes and different sand contents, the average suspended sand particle size calculated based on the suspended sand composition distribution model along the lateral direction can be well matched with the measured data, and the accuracy is significantly improved compared with the traditional method.

[0145] In a specific scenario, taking five typical cross-sections of a section of a wandering river as a research example, the asymmetric index of water and sediment distribution in the river cross-section is calculated according to the asymmetric calculation method for water and sediment distribution in wandering river cross-sections provided in this application. Specifically, the five typical cross-sections are sections A, B, C, D, and E. Based on bend apex and transition points, the five typical cross-sections are divided into two categories: sections A and B are at bend apex, where engineering works are relatively close to the flow; sections C, D, and E are in the transition section between two bend apexes. According to the asymmetric calculation method for water and sediment distribution in wandering river cross-sections, the asymmetric index of water and sediment distribution in the river cross-section under scour-deposition balance, scour, and deposition states is calculated, as shown in Tables 1, 2, and 3. Tables 1, 2, and 3 are as follows:

[0146] Table 1. Asymmetric indices at bends and transition sections of meandering river channels (scour and deposition equilibrium state, S = 32 kg / m³) 3 )

[0147]

[0148] Table 2. Asymmetric indices at bends and transition sections of meandering river channels (cross-sectional scour, S = 5 kg / m) 3 )

[0149]

[0150]

[0151] Table 3. Asymmetric indices at bends and transition sections of meandering river channels (section sedimentation, S = 90 kg / m³) 3 )

[0152]

[0153] Based on the asymmetric index of water and sediment distribution in the cross-section of the river channel under the conditions of scour-deposition equilibrium, scouring, and sedimentation, the sediment-carrying capacity of the water flow under these conditions is calculated, as shown in Table 4. Table 4 is as follows:

[0154] Table 4 Verification of scour and siltation status at each cross-section (flow rate 5000 m³ / h) 3 / s)

[0155]

[0156] As can be seen from Table 4, the sediment concentration set for the river cross-section under the conditions of scour-deposition balance, scouring, and sedimentation has a small error compared with the sediment-carrying capacity of the water flow calculated by the asymmetric calculation method based on the water and sediment distribution of the wandering river cross-section. This indicates that the results calculated by this method can reflect the water and sediment factor distribution status of each cross-section.

[0157] This application presents an asymmetric calculation method for water and sediment distribution in wandering river cross-sections. Based on measured topographic data of the river cross-section, the cross-section is divided into two parts using the centerline under flat-shoal flow as the axis. A constructed lateral water and sediment distribution model is used to obtain the water and sediment factors for the two pre-divided parts of the cross-section. Based on these two parts, an asymmetric index of water and sediment distribution in the cross-section is derived. This quantitatively describes the variation law of water and sediment factors along the lateral distribution of the river cross-section under finite control boundary conditions. This calculation method is not limited by geographical or topographical factors and can be widely applied.

[0158] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An asymmetric calculation method for water and sediment distribution in a cross-section of a wandering river channel, characterized in that, include: Based on the constructed water and sediment lateral distribution model, the water and sediment factors of the two pre-divided parts of the river channel cross section are obtained; wherein, there are multiple water and sediment lateral distribution models; Based on the water and sediment factors of the two parts of the river channel cross section, an asymmetric index of water and sediment distribution in the river channel cross section is obtained, wherein the asymmetric index is used to characterize the asymmetric distribution characteristics of the water and sediment factors along the transverse direction of the river channel cross section. The pre-division specifically involves dividing the river channel cross-section into two parts based on the measured topographic data of the river channel cross-section and taking the centerline of the river channel cross-section under the flat flow as the axis. The asymmetric index of water and sediment distribution in the river cross section includes a first asymmetric index, which characterizes the asymmetric distribution of average flow velocity along the transverse direction of the river cross section. Correspondingly, The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows: According to the formula: ； The first asymmetric index is calculated; In the formula, This is the first asymmetric index; The average flow velocity on the side with the larger area of ​​the two pre-divided sections of the river channel cross-section, in m / s; The average flow velocity on the smaller side of the two pre-divided sections of the river channel cross-section; the unit is m / s. The asymmetric index of water and sediment distribution in the river cross section includes a second asymmetric index, which characterizes the asymmetric distribution of sediment concentration along the river cross section. Correspondingly, The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows: According to the formula: ； The second asymmetry index is calculated; In the formula, AS s This is the second asymmetric index; The sediment content of the side with the larger area in the two pre-divided sections of the river channel cross-section; The sediment content of the smaller side of the two pre-divided sections of the river channel cross-section; The asymmetric index of water and sediment distribution in the river channel cross section includes a third asymmetric index, which characterizes the asymmetric distribution of the average suspended sediment particle size along the transverse direction of the river channel cross section. Correspondingly, The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows: According to the formula: ； The third asymmetry index is calculated; In the formula, AS dcp This refers to the third asymmetric index; d cp大 The average suspended sediment particle size, in meters, is the larger side of the two pre-divided sections of the river channel cross-section. d cp小 The average suspended sediment particle size, in meters, is the smaller side of the two pre-divided sections of the river channel cross-section. The asymmetric index of water and sediment distribution in the river channel cross section includes a fourth asymmetric index, which characterizes the asymmetric distribution of sediment-carrying capacity along the transverse direction of the river channel cross section. Correspondingly, The asymmetric index of water and sediment distribution in the river channel cross-section is obtained based on the water and sediment factors of the two parts of the cross-section, specifically as follows: According to the formula: ； The fourth asymmetry index is calculated; In the formula, This refers to the fourth asymmetry index; The sediment-carrying capacity of the water flow on the side with the larger area of ​​the two pre-divided sections of the river channel cross-section, in units of kg / m³; The sediment-carrying capacity of the water flow is the smaller of the two pre-divided sections of the river channel cross-section, measured in kg / m³.

2. The method for calculating the asymmetric distribution of water and sediment in the cross-section of a wandering river channel according to claim 1, characterized in that, The water and sediment factors include the average flow velocity of the river channel cross-section. Correspondingly, Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two pre-divided parts of the river channel cross-section are obtained, specifically: Based on the pre-acquired water flow data of the river cross section, and based on the constructed velocity distribution model along the lateral direction, the average velocity of the two parts of the river cross section is obtained respectively. The lateral velocity distribution model is as follows: ； ； In the formula, V The average flow velocity of the river channel cross section is expressed in m / s. V i The velocity at any point in the cross-section of the river channel is expressed in m / s. C 1 This represents the first cross-sectional shape coefficient, obtained by solving for mass conservation. h This represents the average water depth of the river channel cross-section, in meters (m). h i This represents the water depth at any point on the cross-section of the river channel, in meters. Q The average flow rate of the river cross section is expressed in m³ / s; a and b are the distances between the starting points of the two ends of the river cross section along the river width, and b > a. y Let be the horizontal coordinate of the integral from a to b.

3. The method for calculating the asymmetric distribution of water and sediment in the cross-section of a wandering river channel according to claim 1, characterized in that, The water and sediment factors include the sediment content of the river channel cross-section. Correspondingly, Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two pre-divided parts of the river channel cross-section are obtained, specifically: Based on the pre-acquired water flow data of the river cross section, and based on the sediment concentration distribution model along the lateral direction, the sediment concentration of the two parts of the river cross section is obtained respectively. The lateral distribution model of the sediment content is as follows: ； ； ； ； ； ； ； In the formula, S The sediment content of the cross-section of the river channel is expressed in kg / m³. S i The sediment content at any point on the cross-section of the river channel is expressed in kg / m³. V The average flow velocity of the river channel cross section is expressed in m / s. V i The velocity at any point in the cross-section of the river channel is expressed in m / s. h This represents the average water depth of the river channel cross-section, in meters (m). h i This represents the water depth at any point on the cross-section of the river channel, in meters. C 2 The second cross-sectional shape coefficient is obtained by solving the sand conservation problem. Q The average flow rate of the river cross section is expressed in m³ / s. q i The unit width flow rate at any point on the cross-section of the river channel is expressed in m² / s. ω s Settling velocity of sediment particles in the river channel, in m / s; Settling velocity of sediment particles in clear water, in m / s; d cp The average suspended sediment particle size of the river channel cross section is expressed in meters. For particle size d cp The settling velocity of uniform sand in clear water, expressed in m / s; The coefficient of kinematic viscosity, in meters. 2 / s; k Kármán's constant; u * The average frictional velocity of the river channel cross section is expressed in m / s. ,in, J To reduce the ratio, take J =2‱, g It is the acceleration due to gravity; S v This refers to the volumetric sand content. S v = S / 2650; The median suspended sediment particle size of the cross-section of the river channel is expressed in meters. The bulk density of sediment particles in the river channel, expressed in N / m³. This is the specific weight of water, expressed in N / m³. a , b The distance between the starting points at both ends of the river channel cross-section along the river width is given by the given point. b > a ; y Let be the horizontal coordinate of the integral from a to b.

4. The method for calculating the asymmetric distribution of water and sediment in the cross-section of a wandering river channel according to claim 1, characterized in that, The water and sediment factors include the average suspended sediment particle size of the river channel cross section. Correspondingly, Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two pre-divided parts of the river channel cross-section are obtained, specifically: Based on the pre-acquired water flow data of the river channel cross section, and based on the suspended sediment composition distribution model along the lateral direction, the average suspended sediment average particle size of the two parts of the river channel cross section is obtained. The lateral distribution model of the suspended sediment composition is as follows: ； ； In the formula, d cp The average suspended sediment particle size of the river channel cross section is expressed in meters. d cpi The average suspended sediment particle size at any point on the cross-section of the river channel is expressed in meters. S The sediment content of the cross-section of the river channel is expressed in kg / m³. S i The sediment content at any point on the cross-section of the river channel is expressed in kg / m³. V The average flow velocity of the river channel cross section is expressed in m / s. V i The velocity at any point in the cross-section of the river channel is expressed in m / s. C 3 The third cross-sectional shape coefficient is obtained by solving the sand conservation problem. q i The unit width flow rate at any point on the cross-section of the river channel is expressed in m² / s. Q The average flow rate of the river cross section is expressed in m³ / s; a and b are the distances between the starting points of the river cross section along the width of the river, and b > a. y Let be the horizontal coordinate of the integral from a to b.

5. The method for calculating the asymmetric distribution of water and sediment in the cross-section of a wandering river channel according to claim 1, characterized in that, The water and sediment factors include the sediment-carrying capacity of the water flow at the cross-section of the river channel. Correspondingly, Based on the constructed lateral distribution model of water and sediment, the water and sediment factors of the two pre-divided parts of the river channel cross-section are obtained, specifically: Based on the pre-acquired water flow data of the river channel cross section, and based on the lateral distribution model of the water flow sediment carrying capacity, the water flow sediment carrying capacity of the two parts of the river channel cross section is obtained respectively. The lateral distribution model of the sediment-carrying force of the water flow is as follows: ； In the formula, The sediment-carrying capacity of the water flow is expressed in kg / m³. V The average flow velocity of the river channel cross section is expressed in m / s. S v This refers to the volumetric sand content; h This represents the average water depth of the river channel cross-section, in meters (m). The median suspended sediment particle size of the cross-section of the river channel is expressed in meters. ω s Settling velocity of sediment particles in the river channel, in m / s; k Kármán's constant; The bulk density of sediment particles in the river channel (N / m³); The specific weight of turbid water is expressed in N / m³. g The acceleration due to gravity is taken as 9.8 m / s².

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