Sediment deposition evaluation method based on water-sediment two-phase flow model

Abstract

The invention relates to the field of model computational hydraulics, in particular to a sediment deposition evaluation method based on a water-sediment two-phase flow model. The difficulty degree of sediment deposition can be indicated through the size of the efficiency coefficient; and comparing and evaluating the sediment deposition levels of the same project under different working conditions or the same working condition under different project reconstruction scheme conditions. According to the evaluation method, the sediment deposition levels of various hydraulic engineering under different working conditions and reconstruction scheme conditions can be compared, so that comprehensive evaluation is carried out, and the sediment deposition levels of various hydraulic engineering under different working conditions and reconstruction scheme conditions can be objectively, accurately and comprehensively reflected and compared.

Description

Technical Field

[0001] This invention relates to the field of model-based computational hydraulics, specifically to a method for evaluating sediment deposition based on a two-phase flow model of water and sediment. Background Technology

[0002] Sedimentation is a common natural phenomenon in rivers, lakes, reservoirs, and pumping station forebays, significantly impacting the safe operation of water conservancy projects, the rational utilization of water resources, ecological environment protection, and socio-economic development. With increasing human activity and the effects of climate change, sedimentation problems are becoming increasingly severe. Therefore, researching and developing effective sedimentation assessment methods is of great significance for solving this problem.

[0003] The main methods for studying sediment deposition include field observation, model experiments, and numerical simulation. While field observation can provide a direct view of sedimentation, its limitations in manpower, resources, and funding make large-scale, long-term continuous monitoring difficult. Model experiments can simulate actual conditions to some extent, but their scale and cost restrict their application. Numerical simulation, due to its efficiency, economy, and strong repeatability, has been widely used in sediment deposition research. Among these methods, the water-sediment two-phase flow model can realistically describe the interaction between the two phases, including the carrying effect of water flow on sediment, the collision between sediment particles, and the interaction between sediment and the riverbed.

[0004] In sediment deposition evaluation methods, the main evaluation indicators include sediment deposition volume, sedimentation rate, volume fraction, and sediment deposition thickness. While these indicators provide effective quantitative means for analyzing sediment deposition, they fail to combine factors such as water flow velocity and sediment concentration to compare and evaluate sediment deposition levels under different working conditions of the same project or under different engineering modification schemes for the same working condition. Therefore, it is necessary to propose a sediment deposition evaluation method based on a two-phase flow model. Summary of the Invention

[0005] In view of the above situation, the purpose of this invention is to provide a sediment deposition evaluation method based on a two-phase flow model of water and sediment. This method can compare and evaluate the sediment deposition level under different working conditions of the same project or under different engineering modification schemes for the same working condition by combining factors such as water flow velocity and sediment content, thus providing a scientific basis for the design, operation and management of water conservancy projects.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: to provide a method for evaluating sediment deposition based on a two-phase flow model of water and sediment, comprising the following steps: (1) Obtain relevant parameters of the model, including: inlet sediment concentration Entry traffic Volume of the research object Sediment particle density water density ; (2) Based on the volume fraction of sediment The volume of the research object in the model It is divided into two parts, one part being the volume fraction of sediment. This volume is the sediment deposit, denoted as [missing information]. The volume fraction of sediment in the other part of the volume. This portion of the volume is the non-silt deposit part, denoted as... ; (3) Based on the research object in the model, determine its sediment deposition portion. The volume of sediment in and water volume To calculate the siltation portion quality ; (4) According to the formula Calculate the efficiency coefficient By calculating the efficiency coefficients under different working conditions of the same project or different project modification schemes under the same working conditions. Based on this indicator, a comparison of siltation is made, and then an evaluation is conducted.

[0007] The efficiency coefficient Defined as siltation efficiency and water exchange efficiency The ratio, i.e. Among them, siltation efficiency Water exchange efficiency Therefore, the efficiency coefficient is :

[0008] in: The part is the silt deposit. quality The sand content at the inlet. To study the volume of the object, The part is the silt deposit. medium sediment particle density, The part is the silt deposit. Density of medium water The part is the silt deposit. The volume of sediment, The part is the silt deposit. The volume of water.

[0009] According to its formula, the efficiency coefficient and , , , The relevant factor is a dimensionless number. Ideally, if no sediment deposition occurs in the flow field, the sediment deposition portion... If the value is 0, then the siltation portion quality =0, The value is 0. Therefore, A smaller efficiency coefficient indicates less sediment deposition and a lower level of sediment deposition. For the same project, must, and The magnitude of the ratio can reflect the level of sediment deposition under different working conditions; for the same working condition, must, and The ratio can also reflect the level of siltation under different engineering modification schemes.

[0010] In addition, due to siltation in some areas It consists of two parts: sediment and water. The sediment deposition part With a constant volume, the volume of sediment and water volume The relative size of the two factors affects the efficiency coefficient. The size of the efficiency coefficient; therefore, the efficiency coefficient It can not only effectively reflect the level of siltation under different working conditions of the same project or different engineering modification schemes under the same working conditions, but also reflect the siltation part The specific gravity of the sediment and water in the middle.

[0011] According to the "Design Code for Dredging and Reclamation Engineering," the silt in the aforementioned research subjects is defined as follows: bottom sediment is divided into floating mud, flowing mud, and silt. The natural water content of the silt... Converted to sediment volume fraction: (The density of the silt particles is taken as 2650 kg / m³) 3 Therefore, the volume of the sediment deposition portion is the volume fraction of sediment in the research object. The sum of the volumes of the grid cells.

[0012] The beneficial effects of this invention are: through the evaluation method of this invention, the level of siltation of various water conservancy projects under different working conditions and renovation schemes can be compared, thereby making a comprehensive evaluation, so as to objectively, accurately and comprehensively reflect and compare the level of siltation of various water conservancy projects under different working conditions and renovation schemes. Attached Figure Description

[0013] Figure 1 This is the water-sediment two-phase flow model of Example 1; Figure 2 This is the water-sediment two-phase flow model of Example 2; Figure 3 This is the water-sediment two-phase flow model of Example 3; Figure 4 This is the water-sediment two-phase flow model of Example 4; Figure 5 This is the water-sediment two-phase flow model of Example 5. Detailed Implementation

[0014] The technical solution of the present invention will be described in detail below, but the scope of protection of the present invention includes, but is not limited to, the embodiments described. Example 1

[0015] A sediment deposition evaluation method based on a two-phase flow model of water and sediment, selecting research objects such as... Figure 1 The figure shows a two-phase flow model of water and sediment without a bottom sill. The relevant model parameters are shown in Table 1. The relevant model parameters include: inlet sediment concentration. Entry traffic Volume of the research object Sediment particle density water density . Example 2

[0016] Selected research subjects, such as Figure 2 The figure shows a two-phase flow model of water and sediment with a bottom sill. The bottom sill is 2m away from the sidewall and 0.3m thick. The relevant model parameters are shown in Table 1. The relevant model parameters include: inlet sediment concentration. Entry traffic Volume of the research object Sediment particle density water density . Example 3

[0017] Selected research subjects, such as Figure 3 The figure shows a two-phase flow model of water and sediment with a bottom sill. The bottom sill is 2.5m away from the sidewall and 0.3m thick. The relevant model parameters are shown in Table 1. The relevant model parameters include: inlet sediment concentration. Entry traffic Volume of the research object Sediment particle density water density . Example 4

[0018] Selected research subjects, such as Figure 4 The figure shows a two-phase flow model of water and sediment with a bottom sill. The bottom sill is 3m away from the sidewall and has a thickness of 0.3m. The relevant model parameters are shown in Table 1. The relevant model parameters include: inlet sediment concentration. Entry traffic Volume of the research object Sediment particle density water density . Example 5

[0019] Selected research subjects, such as Figure 5 The figure shows a two-phase flow model of water and sediment with a bottom sill. The bottom sill is 3m away from the sidewall and 2m thick. The relevant parameters of the model are obtained, as shown in Table 1. The relevant parameters of the model include: inlet sediment concentration. Entry traffic Volume of the research object Sediment particle density water density .

[0020] Table 1. Model-related parameters of the embodiment.

[0021] Then, the volume of the research object in the model. Divided into silt deposits Non-silt deposits Siltation Sediment volume fraction Afterwards, the siltation area was determined. The volume of sediment in and water volume As shown in Table 2.

[0022] The embodiment addresses the siltation portion Non-silt deposits silt deposits The volume of sediment in and water volume The determination of this value can be obtained through model data processing; it is generated by model calculations and is a direct application of existing model data processing methods. This involves screening the sediment volume fraction in the research object. The volume of the grid cells is calculated by summing them using the model, thus yielding the sediment deposition portion. After obtaining the silt deposits Then, the silt deposits can be obtained. The volume of sediment in and water volume ; Screening the grid cell volume of sediment volume fraction in the research object The sum of these values ​​is calculated using the model, thus yielding the non-siltation portion. .

[0023] Table 2 shows the siltation portion of the embodiments. The volume of sediment in and water volume .

[0024] Finally, based on the efficiency coefficient Formula, defining the efficiency coefficient For siltation efficiency and water exchange efficiency The ratio, i.e. Among them, siltation efficiency Water exchange efficiency Therefore, the efficiency coefficient is for:

[0025] The efficiency coefficient is calculated using the formula above, as shown in Table 3.

[0026] Table 3 shows the efficiency coefficients of the models given in Examples 1-5. .

[0027] Table 3 shows the impact of the presence or absence of a bottom sill on siltation by comparing Example 1 and Example 2. The efficiency coefficient of Example 1 (without a bottom sill) is... Maximum, the efficiency coefficient of Example 2 (with a chin) The decrease compared to Example 1 indicates that the siltation level in Example 2 is lower, demonstrating that setting up a sill can effectively reduce siltation. Comparing Examples 2, 3, and 4 reveals the influence of the relative position of the sill within the study object (the distance between the sill and the sidewall of the study object) on siltation. The efficiency coefficients of Examples 2, 3, and 4 are also discussed. The gradual decrease indicates that the farther the bottom sill is from the side wall of the research object, the lower the efficiency coefficient. The smaller the diameter, the less sediment deposition occurs. The relative position of the sill within the study area has a significant impact on reducing sediment deposition. Among these, the scheme presented in Example 4 resulted in the least sediment deposition. Comparing Examples 4 and 5 reveals the influence of sill thickness on sediment deposition. The efficiency coefficient of Example 4... Efficiency coefficient compared to Example 5 The smaller value indicates that the solution given in Example 4 is less prone to siltation, and the solution given in Example 4 is superior to the solution given in Example 5. Furthermore, the efficiency coefficient can be observed from these two examples. Advantages of the evaluation method. Compared to Example 4, the siltation portion of Example 5... The volume of sediment in and water volume Smaller, but with a higher efficiency coefficient Larger. If the silt volume evaluation method is used, the solution given in Example 5 would be considered superior. However, due to the difference in the shape of the bottom sill, the volume of the research object... The efficiency coefficient of sedimentation will decrease accordingly. For evaluation, the volume of the research object can be considered. The impact of the changes leads to a more reasonable and comprehensive conclusion.

[0028] In summary, referring to the sediment deposition evaluation process based on the water-sediment two-phase flow model given in Examples 1-5, it can be seen that by using the efficiency coefficient as an index, the sediment deposition level of various water conservancy projects under different working conditions and modification schemes can be compared and comprehensively evaluated. This method has universal applicability.

Claims

1. A method for evaluating sediment deposition based on a water-sediment two-phase flow model, characterized in that: comprising the steps of: (1) Obtain model related parameters, including: inlet sediment concentration , inlet flow , study object volume , sediment particle density , water density ; (2) Based on the volume fraction of sediment The volume of the research object in the model It is divided into two parts, one part being the volume fraction of sediment. This volume is the sediment deposit, denoted as... The volume fraction of sediment in the other part of the volume. This portion of the volume is the non-silt deposit part, denoted as... ; (3) According to the research object in the model, determine the sediment volume and water volume in the sediment deposition part to calculate the mass of the sediment deposition part ;​​​​ (4) Define the efficiency coefficient : In the formula: The sand content at the inlet. To study the volume of the object, The part is the silt deposit. medium sediment particle density, The part is the silt deposit. Density of medium water The part is the silt deposit. The volume of sediment, The part is the silt deposit. The volume of water. 2.The sediment deposition evaluation method based on the water-sand two-phase flow model according to claim 1, characterized in that, The efficiency coefficient There is no fixed evaluation standard for sediment deposition, and the efficiency coefficient It is not applicable to the evaluation of sediment deposition for a single working condition or a certain single scheme Efficiency coefficient The size of the efficiency coefficient can indicate the degree of difficulty of sediment deposition. 3.The method of claim 2, wherein, The higher the efficiency coefficient Smaller values ​​indicate less sediment deposition and a lower level of sediment deposition.

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