Tailrace pipe harmful flow structure tracing and extraction method and system based on vortex force characteristics

Abstract

The application discloses a vortex power feature-based tailrace pipe harmful flow structure tracing and extraction method and system, which comprises the following steps: constructing a multi-working-condition three-dimensional transient flow field calculation domain of a target tailrace pipe, and determining a corresponding tailrace pipe flow state data set, wherein the multi-working-condition three-dimensional transient flow field calculation domain comprises a runner outlet area and a tailrace pipe area; based on the tailrace pipe flow state data set, performing rotation and shear decomposition on a vortex field of the target tailrace pipe, extracting vortex power features, and determining a harmful flow structure of the target tailrace pipe according to the vortex power features; constructing a multi-dimensional feature set of the harmful flow structure; and judging a development stage of the harmful flow structure according to the multi-dimensional feature set. The application belongs to the field of tailrace pipe harmful flow structure identification. The application can accurately extract the harmful flow structure of the tailrace pipe.

Description

Technical Field

[0001] This invention relates to the field of identifying harmful flow structures in tailrace pipes, and particularly to a method and system for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics. Background Technology

[0002] As a key flow component in the hydraulic energy conversion process, the internal flow state of the draft tube directly affects the turbine's operating efficiency and stability. During actual operation, due to the combined effects of the rotating flow at the runner outlet, pressure gradient changes, and complex boundary conditions, harmful flow structures such as vortices, backflow, pressure pulsations, and enhanced turbulence can easily form inside the draft tube. Especially under non-rated operating conditions such as partial load and overload, these harmful flow structures can further develop and induce problems such as hydraulic vibration, decreased unit efficiency, and reduced operational stability.

[0003] Existing flow analysis methods for tailrace pipes typically rely on numerical simulations to analyze flow characteristics. However, traditional methods often focus on identifying local flow field features, making it difficult to distinguish the different effects of rotational motion and shear deformation on the formation of flow structures. They also struggle to effectively describe the dynamic evolution of harmful flow structures from initial formation to gradual diffusion and eventual instability. Therefore, accurately tracing and extracting harmful flow structures in tailrace pipes is a pressing issue that needs to be addressed. Summary of the Invention

[0004] This invention provides a method and system for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics. This solves the technical problem of accurately extracting harmful flow structures in tailrace pipes in the prior art and achieves the technical effect of accurately extracting harmful flow structures in tailrace pipes.

[0005] In a first aspect, the present invention provides a method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics, including: A multi-condition three-dimensional transient flow field computational domain for the target tailrace pipe is constructed, and the corresponding tailrace pipe flow state dataset is determined. The multi-condition three-dimensional transient flow field computational domain includes the runner outlet region and the tailrace pipe region. Based on the tailrace flow state dataset, the eddy field of the target tailrace is decomposed by rotation and shear, the eddy dynamics features are extracted, and the harmful flow structure of the target tailrace is determined based on the eddy dynamics features. Construct a multidimensional feature set of harmful flow structures; Based on the multidimensional feature set, determine the development stage of the harmful flow structure.

[0006] Furthermore, a multi-condition three-dimensional transient flow field computational domain for the target tailrace pipe is constructed, including:

[0007] in, This is a computational domain for multi-condition three-dimensional transient flow fields. For the turbine export area, The target tailrace fluid region.

[0008] Furthermore, the tailrace flow state dataset is determined, including: Constructing a multi-condition calculation model for the water turbine, including:

[0009] in, For the first Each operating condition For the first The turbine flow rate under each operating condition For the first The rotor speed under each operating condition For the first Working head under each operating condition; Transient solutions are performed for each operating condition to obtain the velocity and pressure fields of the target tailrace pipe, including:

[0010] in, For fluid density, For fluid velocity, For dynamic viscosity, Force term per unit volume, For the pressure inside the pipe, For spatial differential operators; Calculate the vorticity inside the tube ,include:

[0011] Calculate turbulent kinetic energy ,include:

[0012] in, It is the square of the velocity fluctuation components of the fluid velocity in the X, Y, and Z directions; Obtain the tailrace flow state dataset ,include:

[0013] in, For time indexing, The three-dimensional spatial coordinates of the sampling points corresponding to each flow field parameter in the target tailrace pipe flow field.

[0014] Furthermore, based on the tailrace flow state dataset, the vorticity field of the target tailrace is subjected to rotational and shear decomposition to extract vortex dynamic features, including: vorticity Perform rotational and shear decomposition, including:

[0015] in, vorticity, For rotational vorticity, Shear vorticity; Calculate the turbulent kinetic energy generation term ,include:

[0016] in, For turbulent dynamic viscosity, For strain rate tensor intensity.

[0017] Furthermore, the harmful flow structure of the target tailrace pipe is determined based on the aforementioned vortex dynamic characteristics, including: Will , as well as Normalization was performed, and an vortex dynamic contribution index was constructed. ,include:

[0018] in, , as well as All are preset weights. This represents the normalized rotational vorticity. This represents the normalized shear vorticity. This is the normalized turbulent kinetic energy generation term; Based on the vortex power contribution index, the evolution process of harmful flow structures spreading from the runner outlet region to the target tailrace pipe is tracked to determine the initial formation region and development path of the harmful flow structures.

[0019] Furthermore, a multidimensional feature set of harmful flow structures is constructed, including: The Q criterion is used to identify vortex regions, which are typical manifestations of harmful flow structures, including:

[0020] in, Indicators for identifying vortex regions. For rotation tensor intensity, For strain rate tensor intensity;

[0021] in, For circulation, For the closed integral path around the vortex region, For fluid velocity, The length of the infinitesimal element of the integration path;

[0022] in, The frequency domain characteristics of the pressure signal This is a pressure pulsation signal. The imaginary unit, For time indexing, For frequency variables;

[0023] Constructing a multidimensional feature set of harmful flow structures ,in, Contribution index to vortex dynamics The change in turbulent kinetic energy. This represents the change in pressure pulsation. The oscillation frequency of the vortex region.

[0024] Furthermore, based on the multidimensional feature set, the development stage of the harmful flow structure is determined, including: Normalize each feature in the multidimensional feature set and determine the comprehensive feature change rate, including:

[0025] in, The rate of change of the comprehensive characteristics of the harmful flow structure. It is a normalized set of multidimensional features; The development stage of harmful flow structures is determined based on the rate of change of comprehensive characteristics.

[0026] Furthermore, based on the comprehensive characteristic change rate, the development stage of the harmful flow structure is determined, including: when When the change threshold is greater in the turbine outlet region, the harmful flow structure is in its initial stage. when When the change threshold is greater than the target tailrace pipe's diffusion section continues to expand, and the eddy current contribution index, turbulent kinetic energy change, and pressure pulsation change all increase simultaneously, the harmful flow structure is in the development stage. when The rate of change is greater than the rate of change threshold, and the rate of change of pressure pulsation is greater than the pressure rate of change threshold, indicating that the harmful flow structure is in an unstable stage.

[0027] Secondly, this invention provides a system for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics, including: The model building module is used to construct a multi-condition three-dimensional transient flow field calculation domain for the target tailrace pipe and determine the corresponding tailrace pipe flow state dataset. The multi-condition three-dimensional transient flow field calculation domain includes the runner outlet region and the tailrace pipe region. The flow structure extraction module is used to perform rotational and shear decomposition on the eddy field of the target tailwater pipe based on the tailwater pipe flow state dataset, extract eddy dynamic features, and determine the harmful flow structure of the target tailwater pipe based on the eddy dynamic features. A multidimensional feature module is used to construct a multidimensional feature set for harmful flow structures. The stage judgment module is used to determine the development stage of harmful flow structures based on a multi-dimensional feature set.

[0028] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention constructs a multi-condition three-dimensional transient flow field computational domain to achieve a comprehensive description of the flow evolution process of the tailrace pipe under different operating conditions. Based on the vorticity field in the flow field data, it performs rotational and shear decomposition to decouple the rotational motion, shear deformation, and energy dissipation processes that are difficult to distinguish in traditional vortex identification methods. This allows for the extraction of vortex dynamic characteristics that can reflect the formation mechanism of harmful flow, thereby improving the accuracy of harmful flow structure identification.

[0029] Based on this, by constructing a multi-dimensional feature set that integrates vortex dynamic contribution index, vortex characteristics, circulation, oscillation frequency, turbulent kinetic energy change, and pressure pulsation change, a comprehensive characterization of harmful flow structures from multiple dimensions of dynamic characteristics, spatial characteristics, energy characteristics, and unsteady characteristics is achieved.

[0030] Meanwhile, based on the temporal variation pattern of the multidimensional feature set, the evolutionary stages of the harmful flow structure from its initial stage to its development and instability can be further determined, thus realizing a dynamic analysis of the formation process and development trend of the harmful flow structure.

[0031] This invention uses the vortex power contribution index to perform spatiotemporal correlation analysis on high contribution areas, tracks the evolution path of harmful flow structures from the runner outlet area to the interior of the tailrace pipe, and determines their initial formation area, thus tracing the source of harmful flow structures. Based on a defined structural region, this invention utilizes the Q criterion, circulation, frequency domain features, and energy change features to construct a multi-dimensional feature set, thereby enabling the feature extraction of harmful flow structures. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart illustrating the method for tracing and extracting harmful flow structures in tailrace pipes based on vortex dynamics characteristics provided by the present invention. Detailed Implementation

[0034] This invention provides a method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics, which solves the technical problem of accurately extracting harmful flow structures in tailrace pipes in the prior art.

[0035] The technical solution of this invention is to solve the above-mentioned technical problems, and the overall idea is as follows: A method for tracing and extracting harmful flow structures in a tailrace pipe based on eddy dynamics features includes: constructing a multi-condition three-dimensional transient flow field computational domain for the target tailrace pipe and determining the corresponding tailrace pipe flow state dataset, wherein the multi-condition three-dimensional transient flow field computational domain includes the runner outlet region and the tailrace pipe region; based on the tailrace pipe flow state dataset, performing rotational and shear decomposition on the eddy field of the target tailrace pipe to extract eddy dynamics features, and determining the harmful flow structures of the target tailrace pipe based on the eddy dynamics features; constructing a multi-dimensional feature set of the harmful flow structures; and determining the development stage of the harmful flow structures based on the multi-dimensional feature set.

[0036] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0037] First, it should be clarified that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0038] This invention provides, for example Figure 1 The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics, as shown, includes steps S11-S14: Step S11: Construct a multi-condition three-dimensional transient flow field calculation domain for the target tailrace pipe and determine the corresponding tailrace pipe flow state dataset. The multi-condition three-dimensional transient flow field calculation domain includes the runner outlet region and the tailrace pipe region.

[0039] Constructing a multi-condition three-dimensional transient flow field computational domain for the target tailrace pipe, including:

[0040] in, This is a computational domain for multi-condition three-dimensional transient flow fields. For the turbine export area, The target tailrace fluid region.

[0041] Determine the tailrace flow state dataset, including: Constructing a multi-condition calculation model for the water turbine, including:

[0042] in, For the first Each operating condition For the first The turbine flow rate under each operating condition For the first The rotor speed under each operating condition For the first Working head under each operating condition; Transient solutions are performed for each operating condition to obtain the velocity and pressure fields of the target tailrace pipe, including:

[0043] in, For fluid density, For fluid velocity, For dynamic viscosity, Force term per unit volume, For the pressure inside the pipe, For spatial differential operators; Calculate the vorticity inside the tube ,include:

[0044] Calculate turbulent kinetic energy ,include:

[0045] in, It is the square of the velocity fluctuation components of the fluid velocity in the X, Y, and Z directions; Obtain the tailrace flow state dataset ,include:

[0046] in, For time indexing. The three-dimensional spatial coordinates of the sampling points corresponding to each flow field parameter in the target tailrace pipe flow field.

[0047] Specifically, a three-dimensional transient flow field computational domain is first established for the target tailrace pipe under different operating conditions. The operating conditions can include rated conditions, partial load conditions, and overload conditions, and their specific values ​​can be defined according to the actual situation, without limitation here.

[0048] The computational domain includes the impeller outlet region and the tailrace fluid region. The impeller outlet region is used to accurately describe the impeller outlet rotational wake and the transfer of rotational momentum into the tailrace. The tailrace region is used to simulate the development process of the fluid in the diffuser section, bend section and outlet section. Together, the two parts form a complete multi-condition three-dimensional transient flow field computational domain.

[0049] For different operating conditions, corresponding calculation models are constructed. Each operating condition is determined by the flow rate, the rotor speed, and the working head, thus forming a set of multiple typical operating conditions. Each operating condition corresponds to an independent transient numerical simulation process.

[0050] Subsequently, the Navier-Stokes governing equations for incompressible fluids are solved for the three-dimensional transient flow field computational domain corresponding to each operating condition, and the velocity and pressure fields of the fluid in the entire computational domain are calculated hour by hour within a set time step.

[0051] During the solution process, a velocity-pressure coupled algorithm is used to iteratively update the flow field parameters at each time step, so that the velocity field, pressure field and continuity equation simultaneously satisfy the convergence condition.

[0052] After the calculation is completed, the transient velocity field and pressure field corresponding to the tailrace region are extracted from the entire computational domain as the basic data for subsequent flow characteristic analysis.

[0053] After obtaining the transient velocity field, the vorticity at each sampling point is calculated based on the velocity field. The vorticity is calculated from the curl of the velocity field and is used to describe the local fluid rotation intensity and vortex distribution.

[0054] Meanwhile, the turbulent kinetic energy of the corresponding sampling point is calculated based on the velocity fluctuations in each direction. The velocity fluctuations are obtained by the difference between the instantaneous velocity and the corresponding time-averaged velocity. The turbulent kinetic energy is used to reflect the local turbulence intensity and energy dissipation level.

[0055] The three-dimensional spatial coordinates, velocity field, pressure field, vorticity, turbulent kinetic energy, time index, and corresponding operating conditions of each sampling point within the target tailrace pipe area are uniformly organized to form a tailrace pipe flow state dataset D.

[0056] Among them, three-dimensional spatial coordinates are used to identify the location of each flow field parameter, time index is used to describe the transient evolution process of the flow field, and operating conditions are used to identify the flow field state under different boundary conditions.

[0057] Step S12: Based on the tailrace flow state dataset, the eddy field of the target tailrace is decomposed by rotation and shearing to extract eddy dynamic features, and the harmful flow structure of the target tailrace is determined according to the eddy dynamic features.

[0058] Based on the aforementioned tailrace flow state dataset, the vorticity field of the target tailrace is subjected to rotational and shear decomposition to extract vortex dynamic features, including: vorticity Perform rotational and shear decomposition, including:

[0059] in, vorticity, For rotational vorticity, Shear vorticity; Calculate the turbulent kinetic energy generation term ,include:

[0060] in, For turbulent dynamic viscosity, For strain rate tensor intensity.

[0061] The harmful flow structure of the target tailrace pipe is determined based on the eddy dynamic characteristics, including: Will , as well as Normalization was performed, and an vortex dynamic contribution index was constructed. ,include:

[0062] in, , as well as All are preset weights. This represents the normalized rotational vorticity. This represents the normalized shear vorticity. This is the normalized turbulent kinetic energy generation term. , as well as The values ​​can be 0.3, 0.3, and 0.4 respectively. The preset weights can be set according to the actual situation, and there are no restrictions here. Based on the vortex power contribution index, the evolution process of harmful flow structures spreading from the runner outlet region to the target tailrace pipe is tracked to determine the initial formation region and development path of the harmful flow structures.

[0063] Specifically, based on the tailrace flow state dataset constructed in step S11, the vorticity in the flow field of the target tailrace at each moment is decomposed by rotation and shear to distinguish between stable vortex structures dominated by rotational motion and shear flow structures generated by velocity gradients. The vorticity can be decomposed based on the rotational and shear components of the velocity gradient tensor.

[0064] The total vorticity is decomposed into rotating vorticity and shear vorticity. Rotating vorticity is used to characterize the intensity of the local rotational motion of the fluid, while shear vorticity is used to characterize the intensity of shear deformation caused by the fluid velocity gradient.

[0065] The turbulent kinetic energy generation term is calculated for each sampling point based on the transient flow field parameters obtained in step S11. The turbulent kinetic energy generation term describes the ability of the local average flow to transfer energy to turbulent fluctuations; a larger value indicates stronger energy exchange and a stronger turbulent development trend in the fluid region. Since rotating vorticity, shear vorticity, and the turbulent kinetic energy generation term reflect different forms of dynamic characteristics in the flow field, they collectively constitute the vortex dynamic characteristics of the tailrace flow state.

[0066] To eliminate the influence of different physical quantities on their dimensions and numerical ranges, the rotational vorticity, shear vorticity, and turbulent kinetic energy generation terms were normalized, and vortex power contribution indices were constructed according to preset weights.

[0067] Among them, rotational vorticity mainly reflects the rotational intensity of the vortex structure, shear vorticity mainly reflects the degree of fluid shear deformation, and turbulent kinetic energy generation reflects local energy dissipation and turbulence development capability.

[0068] Finally, based on the eddy current contribution index of spatial distribution at each time step, the regions that meet the preset contribution threshold within each time step of the target tailrace pipe are extracted, and the contribution regions that meet the spatial connectivity relationship between adjacent sampling points are divided into the same flow structure, that is, the regions that are greater than the preset contribution threshold are regarded as high contribution regions.

[0069] The preset contribution threshold can be set according to the actual situation; there are no restrictions here.

[0070] Subsequently, the location coordinates, spatial overlap rate, and centroid migration direction of high-contribution regions within adjacent time steps are matched in order of time index. When the spatial overlap rate of two high-contribution regions within adjacent time steps is greater than a preset threshold and the centroid migration direction is consistent with the mainstream flow direction, it is determined that the two belong to the continuous evolution state of the same harmful flow structure at different times, and the corresponding spatiotemporal correlation is established.

[0071] Based on the spatiotemporal correlation established at each time step, the high contribution regions corresponding to the same harmful flow structure at consecutive moments are connected in chronological order to form the spatiotemporal evolution trajectory of the harmful flow structure.

[0072] When the evolution trajectory first appears in the runner outlet region, this location is determined as the initial formation region of the harmful flow structure. Based on the migration paths of high-contribution regions in the evolution trajectory at subsequent time steps, the development path of the harmful flow structure diffusing from the runner outlet to the target tailrace pipe is obtained.

[0073] Step S13: Construct a multidimensional feature set of harmful flow structures.

[0074] Construct a multidimensional feature set of harmful flow structures, including: The Q criterion is used to identify vortex regions, which are typical manifestations of harmful flow structures, including:

[0075] in, Indicators for identifying vortex regions. For rotation tensor intensity, For strain rate tensor intensity;

[0076] in, For circulation, For the closed integral path around the vortex region, For fluid velocity, The length of the infinitesimal element of the integration path;

[0077] in, The frequency domain characteristics of the pressure signal This is a pressure pulsation signal. The imaginary unit, For time indexing, For frequency variables;

[0078] Constructing a multidimensional feature set of harmful flow structures ,in, Contribution index to vortex dynamics The change in turbulent kinetic energy. This represents the change in pressure pulsation. The oscillation frequency of the vortex region.

[0079] Specifically, based on the harmful flow structure determined in step S12, multidimensional flow characteristics are further extracted from the flow field parameters in the corresponding region.

[0080] First, the Q criterion is used to identify vortex regions within the harmful flow structure region. Specifically, the rotation tensor intensity R and strain rate tensor intensity S are calculated based on the velocity gradient tensor, and the vortex region identification index Q corresponding to each sampling point is calculated.

[0081] When Q is greater than the preset Q threshold, rotational motion is determined to be dominant in the corresponding region. This region serves as a typical vortex region of harmful flow structures, used to characterize the spatial distribution range and rotational intensity of the vortex structure. The preset Q threshold can be set according to actual conditions and is not limited here.

[0082] Subsequently, within the identified vortex region, the circulation Γ of the corresponding region is calculated using the closed integral path around the vortex core as the integration path, which is used to characterize the overall rotational intensity of the vortex.

[0083] Meanwhile, pressure pulsation signals corresponding to each pressure monitoring point within the vortex region are extracted, and the frequency domain characteristics of the pressure signals are calculated using Fourier transform. The frequency with the largest spectral amplitude is selected as the vortex oscillation frequency to reflect the dominant oscillation characteristics of the harmful flow structure.

[0084] In addition, the changes in turbulent kinetic energy and pressure pulsation signals within a continuous time step are calculated to characterize the energy changes and pressure fluctuations of the harmful flow structure during its evolution.

[0085] The vortex dynamic contribution index obtained in step S12, along with the vortex region identification index, circulation, vortex oscillation frequency, turbulent kinetic energy change, and pressure pulsation change extracted in this step, are used to construct a multidimensional feature set of harmful flow structures.

[0086] Step S14: Determine the development stage of the harmful flow structure based on the multidimensional feature set.

[0087] Normalize each feature in the multidimensional feature set and determine the comprehensive feature change rate, including:

[0088] in, The rate of change of the comprehensive characteristics of the harmful flow structure. For a normalized set of multidimensional features, the norm can be the Euclidean norm; The development stage of harmful flow structures is determined based on the rate of change of comprehensive characteristics.

[0089] Based on the comprehensive characteristic change rate, the development stages of harmful flow structures are determined, including: when When the change threshold is greater in the turbine outlet region, the harmful flow structure is in its initial stage. when When the change threshold is greater than the target tailrace pipe's diffusion section continues to expand, and the eddy current contribution index, turbulent kinetic energy change, and pressure pulsation change all increase simultaneously, the harmful flow structure is in the development stage. when The rate of change is greater than the rate of change threshold, and the rate of change of pressure pulsation is greater than the pressure rate of change threshold, indicating that the harmful flow structure is in an unstable stage.

[0090] It should be noted that the (preset) change threshold, (preset) change rate threshold, and (preset) pressure change rate threshold can be set according to the actual situation, and there are no restrictions here.

[0091] Specifically, based on the multidimensional feature set of harmful flow structure constructed in step S13, each feature is normalized, and the changes of each feature within consecutive time steps are calculated according to the time index.

[0092] Subsequently, the normalized multidimensional feature set is represented as a time-series feature vector, and the Euclidean norm of its time derivative is calculated to obtain the comprehensive characteristic change rate of the harmful flow structure. The comprehensive characteristic change rate is used to comprehensively reflect the overall degree of change of multiple features such as eddy power contribution, vortex structure, circulation, oscillation frequency, turbulent kinetic energy, and pressure fluctuation per unit time. The larger the value, the faster the evolution of the harmful flow structure and the more drastic the change in the flow field state.

[0093] The development stage of harmful flow structures is determined based on the rate of change of comprehensive characteristics and the spatial distribution characteristics of harmful flow structures.

[0094] When the rate of change of the comprehensive characteristic exceeds the (preset) change threshold for the first time in the runner outlet area, and / or the high vortex power contribution area (i.e. the area greater than the preset vortex power contribution index) only appears locally near the runner outlet and has not yet significantly expanded to the target tailrace diffusion section, the harmful flow structure is judged to be in the initial stage.

[0095] This stage indicates that the vortex structure has just begun to form, and local flow energy has begun to accumulate, but the scope of influence is small, and a stable and developing harmful flow structure has not yet been formed.

[0096] When the rate of change of the comprehensive characteristics continues to exceed the (preset) change threshold, and the harmful flow structure continues to expand from the turbine outlet to the target tailrace diffusion section, the spatial range of the high vortex power contribution area continues to increase, and at the same time the vortex power contribution index, the change in turbulent kinetic energy and the change in pressure pulsation increase synchronously, it is determined that the harmful flow structure has entered the development stage.

[0097] This stage indicates that the vortex structure is continuously strengthening, energy is continuously transferred into the tailrace pipe, the unsteady characteristics of the flow field are gradually increasing, the harmful flow structure has formed a stable development trend, and continues to affect the flow state inside the tailrace pipe.

[0098] When the rate of change of the comprehensive characteristic exceeds the (preset) rate of change threshold, it indicates that the evolution speed of the harmful flow structure is rapidly increasing. At the same time, when the rate of change of the pressure pulsation exceeds the preset pressure change rate threshold, it indicates that the pressure fluctuation inside the tailrace pipe is significantly enhanced. Furthermore, when the vortex oscillation frequency and turbulent kinetic energy change simultaneously fluctuate violently, it is determined that the harmful flow structure has entered the instability stage.

[0099] This stage indicates that the harmful flow structure has become significantly unstable, with rapid changes in its spatial morphology, significantly enhanced pressure pulsation and energy exchange, which can easily induce adverse phenomena such as tailrace pipe vibration, low-frequency pressure pulsation and hydraulic instability. Therefore, it is identified as the final unstable stage of the evolution of the harmful flow structure.

[0100] In summary, this invention constructs a multi-condition three-dimensional transient flow field computational domain to achieve a comprehensive description of the flow evolution process of the tailrace pipe under different operating conditions. Based on the vorticity field in the flow field data, it performs rotational and shear decomposition, decoupling the rotational motion, shear deformation, and energy dissipation processes that are difficult to distinguish in traditional vortex identification methods. This allows for the extraction of vortex dynamic characteristics that can reflect the formation mechanism of harmful flow, thereby improving the accuracy of harmful flow structure identification.

[0101] Based on this, by constructing a multi-dimensional feature set that integrates vortex dynamic contribution index, vortex characteristics, circulation, oscillation frequency, turbulent kinetic energy change, and pressure pulsation change, a comprehensive characterization of harmful flow structures from multiple dimensions of dynamic characteristics, spatial characteristics, energy characteristics, and unsteady characteristics is achieved.

[0102] Meanwhile, based on the temporal variation pattern of the multidimensional feature set, the evolutionary stages of the harmful flow structure from its initial stage to its development and instability can be further determined, thus realizing a dynamic analysis of the formation process and development trend of the harmful flow structure.

[0103] This invention uses the vortex power contribution index to perform spatiotemporal correlation analysis on high contribution areas, tracks the evolution path of harmful flow structures from the runner outlet area to the interior of the tailrace pipe, and determines their initial formation area, thus tracing the source of harmful flow structures. Based on a defined structural region, this invention utilizes the Q criterion, circulation, frequency domain features, and energy change features to construct a multi-dimensional feature set, thereby enabling the feature extraction of harmful flow structures.

[0104] Based on the same inventive concept, this invention also provides a system for tracing and extracting harmful flow structures in tailrace pipes based on vortex dynamics characteristics, including: The model building module is used to construct a multi-condition three-dimensional transient flow field calculation domain for the target tailrace pipe and determine the corresponding tailrace pipe flow state dataset. The multi-condition three-dimensional transient flow field calculation domain includes the runner outlet region and the tailrace pipe region. The flow structure extraction module is used to perform rotational and shear decomposition on the eddy field of the target tailwater pipe based on the tailwater pipe flow state dataset, extract eddy dynamic features, and determine the harmful flow structure of the target tailwater pipe based on the eddy dynamic features. A multidimensional feature module is used to construct a multidimensional feature set for harmful flow structures. The stage judgment module is used to determine the development stage of harmful flow structures based on a multi-dimensional feature set.

[0105] Furthermore, the stage judgment module also includes: The initial stage judgment submodule is used when... When the change threshold is greater in the turbine outlet region, the harmful flow structure is in its initial stage. The development stage determination submodule is used when... When the change threshold is greater than the target tailrace pipe's diffusion section continues to expand, and the eddy current contribution index, turbulent kinetic energy change, and pressure pulsation change all increase simultaneously, the harmful flow structure is in the development stage. The instability phase judgment submodule is used when... The rate of change is greater than the rate of change threshold, and the rate of change of pressure pulsation is greater than the pressure rate of change threshold, indicating that the harmful flow structure is in an unstable stage.

[0106] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0107] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics, characterized in that, include: A multi-condition three-dimensional transient flow field computational domain for the target tailrace pipe is constructed, and the corresponding tailrace pipe flow state dataset is determined. The multi-condition three-dimensional transient flow field computational domain includes the runner outlet region and the tailrace pipe region. Based on the tailrace flow state dataset, the eddy field of the target tailrace is decomposed by rotation and shear, the eddy dynamics features are extracted, and the harmful flow structure of the target tailrace is determined based on the eddy dynamics features. Construct a multidimensional feature set of harmful flow structures; Based on the multidimensional feature set, determine the development stage of the harmful flow structure.

2. The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics as described in claim 1, characterized in that, Constructing a multi-condition three-dimensional transient flow field computational domain for the target tailrace pipe, including: in, This is a computational domain for multi-condition three-dimensional transient flow fields. For the turbine export area, The target tailrace fluid region.

3. The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics as described in claim 2, characterized in that, Determine the tailrace flow state dataset, including: Constructing a multi-condition calculation model for the water turbine, including: in, For the first Each operating condition For the first The turbine flow rate under each operating condition For the first The rotor speed under each operating condition For the first Working head under each operating condition; Transient solutions are performed for each operating condition to obtain the velocity and pressure fields of the target tailrace pipe, including: in, For fluid density, For fluid velocity, For dynamic viscosity, Force term per unit volume, For the pressure inside the pipe, For spatial differential operators; Calculate the vorticity inside the tube ,include: Calculate turbulent kinetic energy ,include: in, It is the square of the velocity fluctuation components of the fluid velocity in the X, Y, and Z directions; Obtain the tailrace flow state dataset ,include: in, For time indexing, The three-dimensional spatial coordinates of the sampling points corresponding to each flow field parameter in the target tailrace pipe flow field.

4. The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics as described in claim 1, characterized in that, Based on the aforementioned tailrace flow state dataset, the vorticity field of the target tailrace is subjected to rotational and shear decomposition to extract vortex dynamic features, including: vorticity Perform rotational and shear decomposition, including: in, vorticity, For rotational vorticity, Shear vorticity; Calculate the turbulent kinetic energy generation term ,include: in, For turbulent dynamic viscosity, For strain rate tensor intensity.

5. The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics as described in claim 4, characterized in that, The harmful flow structure of the target tailrace pipe is determined based on the eddy dynamic characteristics, including: Will , as well as Normalization was performed, and an vortex dynamic contribution index was constructed. ,include: in, , as well as All are preset weights. This represents the normalized rotational vorticity. This represents the normalized shear vorticity. This is the normalized turbulent kinetic energy generation term; Based on the vortex power contribution index, the evolution process of harmful flow structures spreading from the runner outlet region to the target tailrace pipe is tracked to determine the initial formation region and development path of the harmful flow structures.

6. The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics as described in claim 1, characterized in that, Construct a multidimensional feature set of harmful flow structures, including: The Q criterion is used to identify vortex regions, which are typical manifestations of harmful flow structures, including: in, Indicators for identifying vortex regions. For rotation tensor intensity, For strain rate tensor intensity; in, For circulation, For the closed integral path around the vortex region, For fluid velocity, The length of the infinitesimal element of the integration path; in, The frequency domain characteristics of the pressure signal This is a pressure pulsation signal. The imaginary unit, For time indexing, For frequency variables; Constructing a multidimensional feature set of harmful flow structures ,in, Contribution index to vortex dynamics The change in turbulent kinetic energy. This represents the change in pressure pulsation. The oscillation frequency of the vortex region.

7. The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics as described in claim 6, characterized in that, Based on the multidimensional feature set, the development stage of harmful flow structures is determined, including: Normalize each feature in the multidimensional feature set and determine the comprehensive feature change rate, including: in, The rate of change of the comprehensive characteristics of the harmful flow structure. It is a normalized set of multidimensional features; The development stage of harmful flow structures is determined based on the rate of change of comprehensive characteristics.

8. The method for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics as described in claim 7, characterized in that, Based on the comprehensive characteristic change rate, the development stages of harmful flow structures are determined, including: when When the change threshold is greater in the turbine outlet region, the harmful flow structure is in its initial stage. when When the change threshold is greater than the target tailrace pipe's diffusion section continues to expand, and the eddy current contribution index, turbulent kinetic energy change, and pressure pulsation change all increase simultaneously, the harmful flow structure is in the development stage. when The rate of change is greater than the rate of change threshold, and the rate of change of pressure pulsation is greater than the pressure rate of change threshold, indicating that the harmful flow structure is in an unstable stage.

9. A system for tracing and extracting harmful flow structures in tailrace pipes based on eddy dynamics characteristics, characterized in that, include: The model building module is used to construct a multi-condition three-dimensional transient flow field calculation domain for the target tailrace pipe and determine the corresponding tailrace pipe flow state dataset. The multi-condition three-dimensional transient flow field calculation domain includes the runner outlet region and the tailrace pipe region. The flow structure extraction module is used to perform rotational and shear decomposition on the eddy field of the target tailwater pipe based on the tailwater pipe flow state dataset, extract eddy dynamic features, and determine the harmful flow structure of the target tailwater pipe based on the eddy dynamic features. A multidimensional feature module is used to construct a multidimensional feature set for harmful flow structures. The stage judgment module is used to determine the development stage of harmful flow structures based on a multi-dimensional feature set.

10. The tailrace pipe harmful flow structure tracing and extraction system based on eddy dynamics characteristics as described in claim 9, characterized in that, The stage determination module also includes: The initial stage judgment submodule is used when... When the change threshold is greater in the turbine outlet region, the harmful flow structure is in its initial stage. The development stage determination submodule is used when... When the change threshold is greater than the target tailrace pipe's diffusion section continues to expand, and the eddy current contribution index, turbulent kinetic energy change, and pressure pulsation change all increase simultaneously, the harmful flow structure is in the development stage. The instability phase judgment submodule is used when... The rate of change is greater than the rate of change threshold, and the rate of change of pressure pulsation is greater than the pressure rate of change threshold, indicating that the harmful flow structure is in an unstable stage.

Images