CN-122021436-A - Abrupt slope spillway overflow surface cavitation risk assessment method and system

CN122021436ACN 122021436 ACN122021436 ACN 122021436ACN-122021436-A

Abstract

The invention provides a cavitation risk assessment method and a cavitation risk assessment system for an overflow surface of a steep slope spillway, and relates to the technical field of cavitation risk assessment of overflow surfaces; calculating Reynolds number to judge flow state and determine critical flow velocity, extracting flow line curvature and vorticity, judging flow field separation and determining risk correction coefficient, clustering initial high risk grid units by adopting a recursion traversal method, calculating the average value of the risk correction coefficient of the region, judging initial risk level by combining cavitation number and flow velocity and assigning intervals, correcting to obtain final risk level of each grid unit, and visually generating cavitation risk point location distribution map of the high risk region. The high-risk area divided by the method is clear in boundary and accurate in range, the actual distribution rule of cavitation risk on the overflow surface is truly restored, the area accumulation effect of flow field separation is integrated into a risk judgment system, and the cavitation effect of 'higher continuous area risk' is matched.

Inventors

WU JIANBING
Cai Baokun

Assignees

中国电建集团华东勘测设计研究院有限公司
浙江华东工程咨询有限公司

Dates

Publication Date: 20260512
Application Date: 20260131

Claims (9)

1. A method for evaluating cavitation risk of overflow surface of steep slope spillway is characterized by comprising the following specific steps: s1, constructing a three-dimensional finite element model from a spillway weir crest to the tail end of an overflow surface, dividing grid units, inputting acquired spillway body type parameters, local hydrologic pressure parameters and least adverse working condition parameters, setting boundary conditions to perform flow field numerical simulation so as to obtain flow velocity and water pressure of each grid unit, and calculating cavitation numbers; S2, obtaining flow velocity, hydraulic radius and local hydrologic pressure parameters of each grid unit, calculating the Reynolds number of each grid unit at the current moment, judging the flow state type of each grid unit, and determining the critical flow velocity according to the flow state type-critical flow velocity matching rule; s3, extracting the streamline curvature and vorticity of each grid unit, judging whether flow field separation occurs, calculating the flow field separation strength, determining the risk correction coefficient, acquiring the streamline track of the main flow of the overflow surface of the spillway, and defining the grid unit passed by the streamline track as a grid unit in the main flow direction; S4, marking the grid cells in the main flow direction with flow field separation as initial high-risk grid cells, clustering the initial high-risk grid cells by adopting a recursion traversal method to obtain a plurality of independent high-risk areas, calculating the average value of risk correction coefficients of all grid cells in each independent high-risk area, and taking the average value as the risk correction coefficient of the corresponding high-risk area; S5, aiming at each grid cell, comparing the cavitation number with the primary cavitation number, the flow rate and the critical flow rate to obtain initial risk levels and assigning intervals, correcting the initial risk levels by combining the risk correction coefficients of each high-risk area to obtain final risk levels of each grid cell, mapping the visual identification of the final risk levels to a three-dimensional model, generating cavitation risk point location distribution diagrams marked with the high-risk areas, and completing evaluation.
2. The method for evaluating cavitation risk of a steep slope spillway overflow surface according to claim 1, wherein the spillway body type parameters comprise the number of spillway openings, the horizontal width of each opening and the inclination angle of a steep slope section of the spillway, the local hydrologic pressure parameters comprise the local water density, the vaporization pressure, the atmospheric pressure and the water kinematic viscosity, and the worst working condition parameters comprise the highest running water level and the maximum leakage flow.
3. The method for evaluating cavitation risk of a steep slope spillway overflow surface according to claim 2, wherein the three-dimensional finite element model is divided into grid cells, and the specific logic is as follows: The front edge of the spillway weir crest is taken as a starting boundary, the tail end outlet of the spillway surface is taken as a stopping boundary, and an integral three-dimensional area ranging from the spillway weir crest to the tail end of the spillway surface is defined; Combining the number of spillway holes and the horizontal width of each hole, taking the left side wall and the right side wall of each hole as dividing lines, dividing the whole three-dimensional area into a plurality of independent flow passage areas based on the vertical center line of each hole, wherein each independent flow passage area corresponds to the overflow range of 1 hole; Calculating the flow velocity and the Reynolds number of the water flow in each independent flow channel area by combining the highest running water level and the maximum drainage flow; The method comprises the steps that an independent flow channel area meeting the condition that the flow speed exceeds a flow speed threshold value and the Reynolds number exceeds a first Reynolds number threshold value is defined as a leakage core area, and other independent flow channel areas are defined as leakage non-core areas; and carrying out grid cell division on the drainage core area and the drainage non-core area, wherein the grid cell size of the drainage core area is smaller than that of the drainage non-core area.
4. The method for evaluating cavitation risk of a spillway overflow surface of a steep slope according to claim 3, wherein the method comprises determining a flow pattern type of each grid unit, and determining a critical flow rate according to a flow pattern type-critical flow rate matching rule, wherein the specific logic is as follows: If the Reynolds number of a grid unit is smaller than the low Reynolds number threshold, determining that the flow state type is laminar, and matching the corresponding critical flow velocity is ; If the Reynolds number of a grid unit is greater than or equal to the low Reynolds number threshold and less than or equal to the high Reynolds number threshold, determining that the flow state type is a transition flow, and matching the corresponding critical flow velocity is ; If the Reynolds number of a grid unit is larger than the high Reynolds number threshold, determining that the flow state type is turbulent, and matching the corresponding critical flow velocity is ; Calculating the Reynolds number of each grid unit at the current moment based on the flow velocity, the water depth and the kinematic viscosity of water of each grid unit obtained by finite element simulation; judging the flow state type according to the Reynolds number of each grid unit at the current moment and matching to obtain the corresponding critical flow rate; Wherein the low Reynolds number threshold is less than the high Reynolds number threshold, 。
5. The method for evaluating cavitation risk of a spillway overflow surface of a steep slope according to claim 1, wherein the specific logic of extracting the streamline curvature and vorticity of each grid unit and judging whether flow field separation occurs, calculating the flow field separation strength and determining the risk correction coefficient thereof is as follows: extracting streamline curvature and vorticity corresponding to each grid unit from a flow field numerical simulation result; If the streamline curvature of a grid unit is larger than or equal to the streamline curvature threshold value and the vorticity is larger than or equal to the vorticity threshold value, judging that the flow field separation occurs in the area where the grid unit is positioned; For grid cells where flow field separation does not occur, the flow field separation strength is set to 0; For the grid unit judged to be subjected to flow field separation, respectively carrying out weighted calculation on the curvature and the vorticity of the streamline and the weight coefficient of the grid unit to obtain a weighted value of the curvature and a weighted value of the vorticity of the streamline, and adding the 2 weighted values to obtain flow field separation strength; the mapping relation between the flow field separation strength and the risk correction coefficient is constructed as follows: If the flow field separation strength of a grid cell is less than the low separation strength threshold, the matching risk correction coefficient is ; If the flow field separation strength of a grid unit is greater than or equal to the low separation strength threshold and less than or equal to the high separation strength threshold, the matching risk correction coefficient is ; If the flow field separation strength of a grid unit is greater than the high separation strength threshold, the matching risk correction coefficient is ; Wherein the low separation strength threshold is less than the high separation strength threshold, 。
6. The method for evaluating cavitation risk of a steep slope spillway overflow surface according to claim 5, wherein the initial high risk grid cells are clustered by a recursive traversal method, and the specific logic is as follows: Marking all initial high-risk grid cells as non-accessed states, arbitrarily selecting one non-accessed initial high-risk grid cell as a recursion starting point, and constructing a cluster containing the recursion starting point; Judging whether a common side exists between the recursion starting point and each initial high-risk grid cell which is not accessed, updating the initial high-risk grid cell which has the common side into an accessed state, classifying the accessed state into a cluster, taking the initial high-risk grid cell classified into the cluster as a new starting point, and then incorporating a new initial high-risk grid cell into the cluster again until the new initial high-risk grid cell cannot be incorporated, and summarizing all the initial high-risk grid cells in the final cluster to form a high-risk area; And randomly selecting an unaccessed initial high-risk grid unit again to serve as a new recursion starting point, and repeating the steps to form a new high-risk area until all initial high-risk grid units are updated to be in an accessed state.
7. The method for evaluating cavitation risk of a spillway overflow surface of a steep slope according to claim 6, wherein for each grid unit, comparing the cavitation number with the primary cavitation number, and comparing the flow rate with the critical flow rate to obtain an initial risk level and assigning a section, wherein the method comprises the following specific logic: If the cavitation number of a grid unit is greater than or equal to the primary cavitation number and the flow rate is less than or equal to the critical flow rate, determining that the initial risk level is a low risk level, and calibrating the assignment interval of the low risk level as ; If the cavitation number of a grid unit is greater than or equal to the primary cavitation number and the flow rate is greater than the critical flow rate, or the cavitation number is less than the primary cavitation number and the flow rate is less than or equal to the critical flow rate, determining that the initial risk level is a risk level, and calibrating the assignment interval of the risk level as ; If the cavitation number of a grid unit is smaller than the primary cavitation number and the flow rate is larger than the critical flow rate, determining that the initial risk level is a high risk level, and calibrating an assignment interval of the high risk level as 。
8. The method for evaluating cavitation risk of a spillway overflow surface of a steep slope according to claim 7, wherein the final risk level of each grid unit is obtained by correcting the risk correction coefficient of each high risk area by combining the risk correction coefficient with the risk correction coefficient of each high risk area, and the specific logic is as follows: Aiming at grid cells positioned in a high risk area, correcting the initial risk level by using a risk correction coefficient mean value of the high risk area; For each grid unit in the high risk area, extracting the lower limit value and the upper limit value of the assignment interval corresponding to the initial risk level, multiplying the lower limit value and the upper limit value with the risk correction coefficient mean value of the high risk area respectively to obtain the final risk interval range of the grid unit, and judging the final risk level according to the final risk interval range of each grid unit, wherein the method specifically comprises the following steps: If the final risk interval range falls into If the risk level is within the preset threshold, judging that the final risk level is a low risk level; If the final risk interval range falls into In or with If the intersection exists and the lower limit of the assigned interval of the high risk level is not covered, judging that the final risk level is the middle risk level; If the final risk interval range falls into In or with If the intersection exists, or the upper limit value of the final risk interval exceeds 3.6, judging that the final risk level is a high risk level; for grid cells outside the high risk area, the initial risk level is directly used as the final risk level, and no correction is made; integrating the correction results of the class 2 grid cells to obtain the final risk level of all the grid cells; the corresponding mark colors are matched according to the final risk level, wherein the high risk level is matched with the red mark, the medium risk level is matched with the yellow mark, and the low risk level is matched with the green mark; Based on a space coordinate system of the three-dimensional finite element model, mapping the final risk level and the corresponding identifier of each grid unit to the corresponding space position of the model one by one, and finally generating a cavitation risk point position distribution map of the spillway overflow surface.
9. A steep slope spillway overflow surface cavitation risk assessment system for performing a steep slope spillway overflow surface cavitation risk assessment method according to any of claims 1-8, comprising: The grid dividing module is used for constructing a three-dimensional finite element model from the spillway weir crest to the tail end of the overflow surface, dividing grid units, inputting acquired spillway body type parameters, local hydrologic pressure parameters and least favorable working condition parameters, setting boundary conditions to perform flow field numerical simulation so as to obtain the flow velocity and water pressure of each grid unit and calculating cavitation numbers; The flow rate matching module is used for acquiring the flow rate, the water depth and the kinematic viscosity of water of each grid unit, calculating the Reynolds number of each grid unit at the current moment, judging the flow state type of each grid unit and determining the critical flow rate according to the flow state type-critical flow rate matching rule; The main flow determining module is used for extracting the streamline curvature and the vorticity of each grid unit, judging whether flow field separation occurs, calculating the flow field separation strength, determining the risk correction coefficient, acquiring the streamline track of the main flow of the overflow surface of the spillway, and defining the grid unit through which the streamline track passes as a grid unit in the main flow direction; The clustering module is used for marking the grid cells in the main flow direction with flow field separation as initial high-risk grid cells, clustering the initial high-risk grid cells by adopting a recursion traversal method to obtain a plurality of independent high-risk areas, calculating the average value of risk correction coefficients of all grid cells in each independent high-risk area, and taking the average value as the risk correction coefficient of the corresponding high-risk area; the risk assessment module is used for obtaining initial risk levels and assigned intervals by comparing the cavitation number with the primary cavitation number, the flow rate and the critical flow rate for each grid unit, correcting the initial risk levels by combining the risk correction coefficients of each high-risk area, obtaining final risk levels of each grid unit, mapping the visual identification of the final risk levels to the three-dimensional model, generating cavitation risk point location distribution diagrams marked with the high-risk areas, and completing assessment.

Description

Abrupt slope spillway overflow surface cavitation risk assessment method and system Technical Field The invention relates to the technical field of cavitation risk assessment of overflow surfaces, in particular to a cavitation risk assessment method and a cavitation risk assessment system for overflow surfaces of steep slope spillways. Background The steep slope spillway is used as a core structure for releasing flood, and the overflow surface of the steep slope spillway is subjected to scouring and erosion of high-speed water flow for a long time, so cavitation erosion is a key hidden danger threatening the structural safety and the operation stability of the steep slope spillway. Cavitation is generated because the local pressure of water flow is reduced below the vaporization pressure, cavitation bubbles are formed, and when the bubbles move to a high-pressure area along with the water flow to collapse, huge energy is released, and the bubbles repeatedly impact the wall surface of the overflow surface, so that structural damages such as concrete peeling and exposed reinforcing steel bars are finally caused, the service life of the spillway is greatly shortened, and serious engineering accidents such as overtopping and dam break can be possibly caused. In order to solve the above problems, a great deal of technical research has been conducted in the related art, and various cavitation risk assessment methods have been formed. According to the cavitation risk assessment method for the overflow surface of the steep slope spillway, which is provided by the publication No. CN118194421A, the cavitation risk is assessed by determining hydrologic pressure parameters, spillway body types and working condition parameters, calculating the average flow velocity and cavitation number of the water surface line and the section by adopting a segmentation test algorithm, and finally taking the critical flow velocity and the primary cavitation number as comprehensive discrimination criteria. On the basis, the flow field simulation evaluation technology based on the three-dimensional finite element grid is developed gradually, the calculation of risk parameters such as flow speed, water pressure and the like at the grid unit level can be realized, the limitation of traditional macroscopic evaluation can be broken through theoretically, and the refined risk analysis of the whole overflow surface area can be realized. The existing cavitation risk assessment technology still has obvious short plates, wherein the sectional trial algorithm method belongs to section level macroscopic assessment, only can judge the along-path section risk, cannot capture the global local risk difference of an overflow surface, is not matched with the natural continuous spatial characteristics of a high-risk area based on the three-dimensional finite element grid flow field simulation assessment technology, adopts indiscriminate single parameter judgment on a risk grid unit, is easy to fracture a connected high-risk area into a plurality of independent areas due to local parameter fluctuation and calculation errors on one hand, cannot accurately restore the actual distribution rule of risks, and lacks quantitative indexes for representing the overall risk level of the area and an area risk-unit risk correlation correction mechanism on the other hand, only depends on cavitation number and flow velocity judgment risk level, and ignores the accumulated effect of a fluid severe area. The above information disclosed in the background section is only for enhancement of understanding of the background of the disclosure and therefore it may include information that does not form the prior art that is already known to a person of ordinary skill in the art. Disclosure of Invention The invention aims to provide a cavitation risk assessment method and a cavitation risk assessment system for a steep slope spillway overflow surface, so as to solve the problems in the background art. In order to achieve the above purpose, the present invention provides the following technical solutions: a method for evaluating cavitation erosion risk of overflow surface of steep slope spillway specifically comprises the following steps: s1, constructing a three-dimensional finite element model from a spillway weir crest to the tail end of an overflow surface, dividing grid units, inputting acquired spillway body type parameters, local hydrologic pressure parameters and least adverse working condition parameters, setting boundary conditions to perform flow field numerical simulation so as to obtain flow velocity and water pressure of each grid unit, and calculating cavitation numbers; S2, obtaining flow velocity, hydraulic radius and local hydrologic pressure parameters of each grid unit, calculating the Reynolds number of each grid unit at the current moment, judging the flow state type of each grid unit, and determining the critical flow velocity according to the flow state typ