Wind power pile foundation washout test drainage control method and system based on large-scale water tank

Abstract

The invention relates to the technical field of wind power pile foundation washout test drainage control, and discloses a wind power pile foundation washout test drainage control method and system based on a large-scale water tank. Firstly, a target drainage rate is calculated based on a drainage similarity criterion, and the dynamic similarity between a model test and a prototype working condition is ensured; and secondly, staged acceleration control is implemented by adopting a multi-stage drainage pump group, bed surface flow field distortion caused by sudden power change of a traditional single-pump system is avoided through gradual flow regulation, and the natural development process of a pile periphery vortex structure is maintained. Meanwhile, an omnibearing monitoring system of the sensor matrix captures coupling change of drainage flow and bed surface form in real time, and provides characteristic data with high temporal-spatial resolution for subsequent dynamic regulation and control. And finally, dynamic compensation is performed on drainage power based on bed surface elevation data fed back in real time, a flow velocity field adaptive adjustment mechanism is realized, and a flow field offset error caused by sediment transportation in the test process is effectively inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of drainage control for wind power pile foundation scouring tests, and particularly to a drainage control method and system for wind power pile foundation scouring tests based on a large-scale flume. Background Art

[0002] With the transformation of the global energy structure towards cleaner energy, offshore wind power has become an important direction for renewable energy development. The pile foundation structure supporting offshore wind turbines is in a complex marine hydrodynamic environment for a long time, and its stability is directly related to the operation safety of the entire power generation system. Under the action of periodic hydrodynamic loads such as waves and tides, local scouring pits are likely to form around the pile body. This phenomenon of sediment transport caused by the interaction between water flow and structure will significantly weaken the lateral bearing capacity of the pile foundation. When the scouring depth exceeds the critical threshold, serious consequences such as structural resonance, fatigue damage, and even overall overturning may occur. Therefore, simulating the scouring evolution process of pile foundations through physical model tests and deeply studying the formation mechanism and development law of scouring have important engineering value for optimizing the design of foundation structures and formulating effective protection measures.

[0003] Accurately reproducing the hydrodynamic conditions of real marine conditions in the laboratory environment is the technical core of carrying out pile foundation scouring simulation tests. In order to overcome the influence of scale effects, such tests mostly use large-scale physical models, such as large-scale flumes. The flume size and sediment laying area required by large-scale physical models are dozens of times that of general small flumes, which brings problems such as long drainage time and difficult control of the drainage process. At the same time, the test system needs to construct a flow field that is dynamically similar to the prototype, so that key parameters such as the flow velocity distribution and shear stress in the model can accurately map the physical processes in actual engineering. Among them, the precise control of the flow velocity field constitutes a decisive factor for the effectiveness of the test. The flow velocity not only directly affects the initiation and transport of bed sediment, but also dominates the whole process evolution law of the scouring pit from initial formation to dynamic equilibrium by changing the morphological characteristics of the vortex structure around the pile. If there is a deviation in the flow velocity simulation, it will lead to the distortion of key parameters such as the scouring rate and the maximum scouring depth, making the test conclusions lose their guiding significance for engineering practice.

[0004] Therefore, there is an urgent need for a drainage control method and system for wind power pile foundation scouring tests based on a large-scale flume to improve the simulation accuracy of wind power pile foundation scouring tests. Summary of the Invention

[0005] In order to improve the simulation accuracy of wind power pile foundation scouring tests, the present invention provides a drainage control method and system for wind power pile foundation scouring tests based on a large-scale flume. The control method includes the following steps: Step S1, calculating the target drainage rate based on the drainage similarity criterion; Step S2, using a multi-stage drainage pump group to control the drainage process, so that the drainage rate increases from the initial value to the target drainage rate in stages; The phased increase process adopts a three-stage exponential acceleration model, and the calculation formula is: ; in, q(t) A function representing the change in drainage rate over time; q tar represents the target drainage rate, α represents the acceleration coefficient, β represents the transition section attenuation factor, t 0 indicates the start time of the transition period. t represents the cumulative time of the drainage process, sgn represents the sign function; Step S3, real-time monitoring of drainage flow and bed elevation data through a sensor matrix; Step S4: dynamically adjust the output power of the multi-stage drainage pump group based on the bed elevation data to achieve drainage control.

[0006] Furthermore, when the following formula is satisfied, the transition start time is triggered t 0: ; in, represents the bed settling rate, h th Indicates the bed subsidence rate threshold.

[0007] Furthermore, sgn( t - t 0) Specifically: when t ≤ t At 0, sgn( t - t 0)=-1; when t > t At 0, sgn( t - t 0)=1.

[0008] Furthermore, in step S2, the outlet of the multi-stage drainage pump group is connected to a multi-stage buffer tank structure, and the water level difference between adjacent buffer tanks satisfies the following relationship: ; in, represents the water level difference between adjacent buffer tanks, K represents the kinetic energy dissipation coefficient, A represents the cross-sectional area of the buffer tank, g represents the gravitational acceleration, and q represents the graded design drainage flow of the multi-stage buffer tank system.

[0009] Furthermore, in step S4: dynamically adjusting the output power of the multi-stage drainage pump group based on the bed elevation data, ; wherein, represents the dynamic pressure compensation amount, represents the bed shear stress gradient along the mainstream direction x, represents the bed shear stress gradient along the transverse direction y, represents the axial compensation coefficient, represents the transverse compensation coefficient, t represents the cumulative time of the drainage process. Further, the sensor matrix in the step S3 includes: an electromagnetic flowmeter arranged in the drainage pipe; laser ranging sensors annularly distributed along the pile circumference; pore water pressure sensors buried in the riprap protection layer.

[0010] On the other hand, the present invention also provides a drainage control system for the scour test of wind power pile foundations based on a large-scale flume, which executes the drainage control method for the scour test of wind power pile foundations based on a large-scale flume described in any one of the above. The control system includes a target drainage rate determination module, a drainage rate increase determination module, and a drainage rate dynamic adjustment module; The target drainage rate determination module is used to calculate the target drainage rate based on the drainage similarity criterion; The drainage rate increase determination module is connected to the target drainage rate determination module and is used to control the drainage process by using a multi-stage drainage pump set, so that the drainage rate increases from an initial value to the target drainage rate in stages; The drainage rate dynamic adjustment module is connected to the drainage rate increase determination module and is used to monitor the drainage flow and bed elevation data in real time through a sensor matrix; dynamically adjust the output power of the multi-stage drainage pump set based on the bed elevation data to achieve the control of drainage.

[0011] The embodiments of the present invention have the following technical effects: The present invention effectively improves the hydrodynamic simulation accuracy of the scour test for wind power pile foundations by constructing a closed-loop system that combines drainage similarity criteria and dynamic feedback control. First, based on the drainage similarity criteria, the target drainage rate is calculated to ensure the dynamic similarity between the model test and the prototype working conditions, enabling key parameters such as the flow velocity field and shear stress to meet the matching requirements of the geometric scale and time scale, laying a theoretical foundation for the physical similarity of the scour process. Second, a multi-stage drainage pump group is used to implement staged speed increase control, and the progressive flow regulation avoids the distortion of the bed surface flow field caused by sudden power changes in the traditional single-pump system, maintaining the natural development process of the vortex structure around the pile. At the same time, the all-round monitoring system of the sensor matrix captures the coupled changes in the drainage flow and the bed surface morphology in real time, providing characteristic data with high spatio-temporal resolution for subsequent dynamic regulation. Finally, based on the real-time feedback of the bed surface elevation data, dynamic compensation is performed on the drainage power, realizing an adaptive adjustment mechanism for the flow velocity field and effectively suppressing the flow field deviation error caused by sediment transport during the test. Through the synergistic effect of similarity theory guidance, hierarchical flow control, real-time monitoring feedback, and dynamic compensation adjustment, this technical solution significantly improves the simulation fidelity of the hydrodynamic conditions in the scour test, enabling test data such as the scour rate and the morphology of the scour pit to accurately reflect the pile foundation scour law in the actual marine environment, providing a reliable basis for engineering protection design. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0013] Figure 1 It is a flow chart of the drainage control method for the scour test of wind power pile foundations based on a large-scale flume provided by an embodiment of the present invention; Figure 2 It is a schematic structural diagram of the drainage control system for the scour test of wind power pile foundations based on a large-scale flume provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope protected by the present invention.

[0015] To improve the simulation accuracy of the scour test for wind power pile foundations, the present invention provides a drainage control method and system for the scour test of wind power pile foundations based on a large-scale flume, as Figure 1 shown. The control method includes the following steps: Step S1: Calculate the target drainage rate based on the drainage similarity criterion; In the scour model test of wind power pile foundations, the accurate simulation of hydrodynamic conditions depends on the precise control of the drainage rate. At the initial stage of the test, the target drainage rate needs to be determined according to the drainage similarity criterion, which establishes the dynamic similarity between the model and the prototype through the corresponding relationship between the geometric scale and the time scale. The drainage similarity criterion comprehensively considers dimensionless parameters such as the Froude number and the Reynolds number to ensure that key parameters such as the flow velocity distribution and shear stress in the model test are dynamically similar to the prototype conditions. The calculation of the target drainage rate needs to be based on the geometric dimensions of the test water area, the sediment particle size distribution characteristics, and the design parameters of the prototype project, and a flow rate reference value that conforms to the similarity law is obtained through proportional conversion. The specific calculation method is not limited in this application and will not be elaborated here.

[0016] Step S2: Use a multi-stage drainage pump group to control the drainage process, so that the drainage rate increases from the initial value to the target drainage rate in stages; Exemplarily, the multi-stage drainage pump group is composed of several centrifugal pumps with different powers connected in parallel, and the pumps cooperate with each other through a frequency conversion controller. In the initial drainage stage, a low-power pump group is used to maintain the basic flow rate, and medium- and high-power pump groups are activated in stages as the test progresses to gradually increase the drainage rate to the target value. The staged acceleration strategy can avoid the sudden change in flow rate caused by the full-load start of a single pump and prevent the destruction of the flow field stability in the test section due to drainage impact. During the pump group switching process, there is an overlapping working interval between adjacent pump groups, and a smooth transition is achieved through the flow rate superposition method. The multi-stage pump group configuration not only improves the flow rate adjustment resolution but also enhances the redundancy ability of the system to cope with sudden working conditions.

[0017] In some embodiments, the process of increasing in stages adopts a three-stage exponential acceleration model, and the calculation formula is: ; where q(t) represents the function of the drainage rate changing with time; q tar represents the target drainage rate, α represents the acceleration coefficient, and its value is related to the mechanical inertia of the pump group and the water resistance characteristics of the pipeline, and the optimal parameters need to be obtained through no-load tests; β represents the attenuation factor of the transition section, t 0 represents the starting time of the transition section, corresponding to the critical state where the sediment on the bed surface changes from static to starting. At this time, the flow field structure changes significantly, and the shear stress balance needs to be maintained through flow rate adjustment; t represents the cumulative time of the drainage process, and sgn represents the sign function.

[0018] Among them, the function of the drainage rate varying with time q(t) represents the actual drainage flow rate at time t (unit: m³ / s). The drainage rate is dynamically regulated through this function to balance the rapid drainage demand and the bed surface stability. The starting time of the transition section t 0 is dynamically triggered by the threshold of the bed surface settlement rate, forming a closed-loop feedback control. The multi-stage buffer pool structure (ΔH calculation formula) is used to absorb the kinetic energy fluctuations generated by the terms in the formula in the formula

[0019] The stage adjustment of the drainage rate adopts a three-stage exponential acceleration model. This model divides the drainage process into an initial acceleration stage, a transition adjustment stage, and a target stable stage. In the initial acceleration stage (t ≤ t0), the drainage rate gradually increases from the initial value in this stage, but the acceleration is inhibited: in the initial stage of the experiment, the flow field needs to be slowly established to prevent the water flow shear stress from instantly exceeding the critical value of sediment incipient motion, resulting in premature scouring and deformation of the bed surface. At this time, the sediment is in a static or weakly moving state, and a low flow velocity is required to maintain the initial shape of the bed surface. In the transition adjustment stage (t > t0), local scouring has occurred on the bed surface, and the drainage rate needs to be increased to simulate the flow field intensity of the prototype working condition. In the target stable stage, the drainage rate reaches the target value and enters a stable state, simulating the stable hydrodynamic conditions in the prototype, allowing the shape of the scouring pit to naturally develop to an equilibrium state to obtain reliable test data. In the initial acceleration stage, it is necessary to avoid a sudden increase in shear stress from damaging the bed surface; in the transition adjustment stage, it is necessary to dynamically match the sediment transport energy level; in the target stable stage, it is necessary to maintain the similarity of the flow field. According to the different stages, the pump group power is adjusted to achieve the control of the drainage rate

[0020] In the initial acceleration stage, through the exponential function term dominates and is used to describe the progressive acceleration characteristics in the initial stage. The smooth rise of the flow rate is achieved through the natural decay characteristics of the exponential function, enabling the drainage rate to rise smoothly and avoiding sudden changes in the flow rate. The sign function sgn( t - t 0) = -1, and the square root term is negative, suppressing the too-fast increase in drainage speed and protecting the stability of the bed surface

[0021] In the transition adjustment stage, the triggering condition is the bed surface settlement rate , indicating that the sediment enters the active transport stage. The sign function switches to sgn( t - t 0) = 1, and the square root term becomes positive, and the drainage rate accelerates towards the target value. In the formula, the square root function term dominates, the acceleration slows down but continues to increase, matching the energy level requirements of the scouring development The reciprocal of is 0.5▏t - t0▏ -0.5, indicating that the rate of change of the drainage rate dq / dt decays with time. This non-linear growth characteristic results in: a slower increase in the flow velocity in the later stage and a smooth transition of the shear stress. The sediment in the transition adjustment section mainly moves in saltation. The smooth growth of the square root function enables the control of the sediment transport rate and the maintenance of critical conditions: the sediment transport rate is related to a high power of the flow velocity, and the slower growth can avoid sudden changes in the bed surface morphology caused by exponential growth of the sediment transport rate; it keeps the bed surface shear stress always close to the critical value for sediment incipient motion, ensuring both the continuity of sediment transport and preventing excessive scouring. Therefore, the square root function controls the non-linear growth of the drainage rate, reduces the rate of change of the flow velocity in the later stage, optimizes the distribution of water flow energy, thereby suppressing the risk of secondary scouring caused by inertial effects and ensuring the natural development of the scouring process.

[0022] In the target stable section, the exponential function term approaches 1, the growth rate of the term slows down, and the system has maintained a constant flow rate through dynamic compensation.

[0023] The introduction of the sign function sgn realizes the automatic reversal of the flow rate change trend before and after the transition section. Before the starting time of the transition section, the sign function is negative, and the square root term has an inhibitory effect, preventing overshoot of the flow rate in the initial stage. When the test time exceeds the starting time of the transition section, the sign function turns positive, and the square root term starts to play an enhancing role, driving the drainage rate to quickly approach the target value. This two-way adjustment mechanism makes the flow rate curve have a continuous first derivative at the key turning point, avoiding damage to the test equipment caused by mechanical shock.

[0024] In some embodiments, sgn( t - t 0) specifically is: When t ≤ t 0, sgn( t - t 0) = -1, which is negative, indicating suppressing sudden changes in the drainage rate, reducing the water flow shear force, and avoiding breakthrough of the critical incipient motion conditions of sediment particles; suppressing the rapid increase of the drainage rate, preventing the bed surface shear stress from exceeding the limit due to sudden changes in water flow in the initial stage, and protecting the bed surface stability. At this time, the drainage rate is mainly dominated by the first term and shows the characteristic of exponentially approaching the target value.

[0025] When t > t 0, sgn( t - t 0) = 1, which is positive, indicating accelerating the drainage process in the transition section to ensure quickly reaching the target drainage rate q tar , meeting the test efficiency requirements; realizing two-way dynamic adjustment of the drainage rate through sign reversal.

[0026] The introduction of the sign function realizes the automatic reversal of the flow rate change trend before and after the transition section. Before the start time of the transition section, the sign function is negative, and the square root term produces an inhibitory effect to prevent the flow rate overshoot in the initial stage. When the test time exceeds the start time of the transition section, the sign function turns positive, and the square root term begins to play an enhancing role, driving the drainage rate to quickly approach the target value. This two-way adjustment mechanism enables the flow rate curve to have a continuous first derivative at the key turning points, avoiding damage to the test equipment caused by mechanical shocks.

[0027] Therefore, in the drainage control of the wind power pile foundation scour test, the design of the sgn function achieves the following key objectives: (1) Prevent the bed surface from collapsing By t reversing the sign at time 0, precisely controlling the growth slope of the drainage rate.

[0028] In the initial stage ( t ≤ t 0), the negative regulation reduces the water flow shear stress and avoids breaking through the critical starting condition of sediment particles.

[0029] (2) Optimize energy dissipation The introduction of the square root term makes the flow velocity change rate , effectively attenuating the inertial energy of the water flow and reducing the risk of secondary scour (such as the collapse of the edge of the scour pit).

[0030] (3) Test repeatability By clearly dividing the drainage stage through the sgn function, ensuring that the time-rate curves of different test batches are strictly consistent, and improving the comparability of data.

[0031] In some embodiments, when the following formula is satisfied, the start time of the transition section is triggered t 0: ; Where represents the bed surface settlement rate, h th represents the bed surface settlement rate threshold.

[0032] The triggering mechanism of the transition section start time is based on the real-time monitoring results of the bed surface settlement rate. The bed surface settlement rate is calculated from the time series data of the laser rangefinder, and the sliding window difference method is used to eliminate the measurement noise. When the settlement rate exceeds the preset threshold, it indicates that the sediment on the bed surface enters the active transport state. At this time, the interaction between the flow field and the bed surface enters the nonlinear stage, and the transition section acceleration mode needs to be started to match the energy level requirements. The setting of the threshold needs to refer to the critical starting shear stress of the sediment, and the response characteristics of different particle size groups are determined through the flume calibration test.

[0033] The physical meaning of the threshold of the bed surface settlement rate lies in identifying the critical point of the transition of the sediment transport state. When the settlement rate is lower than the threshold, the sediment movement is mainly the rolling and sliding of individual particles. At this time, maintaining a low drainage rate can avoid excessive disturbance. After exceeding the threshold, group particle jumping movement and even suspension movement occur on the bed surface, and the energy demand of the flow field increases significantly. The system switches to the acceleration mode in the transition section, timely increases the power of the drainage pump group, and ensures that the shear stress and the sediment transport intensity maintain a dynamic balance.

[0034] The realization of the triggering mechanism depends on the collaborative work of the high-speed data acquisition system and the real-time control algorithm. The laser ranging data is transmitted to the processor at a fixed sampling frequency, and the instantaneous settlement rate is obtained through digital filtering and real-time differential calculation. When the settlement rates of multiple consecutive sampling points exceed the threshold, the system determines that the triggering condition is established and immediately starts the control logic in the transition section. This dual verification mechanism can effectively avoid false triggering caused by accidental interference and improve the reliability of state switching.

[0035] In some embodiments, in step S2, the outlet of the multi-stage drainage pump group is connected to a multi-stage buffer pool structure, and the water level difference between adjacent buffer pools satisfies the following relational expression: ; where represents the water level difference between adjacent buffer pools, K represents the kinetic energy dissipation coefficient, A represents the cross-sectional area of the buffer pool, g represents the acceleration due to gravity, and q represents the graded design drainage flow rate of the multi-stage buffer pool system.

[0036] The multi-stage buffer pool structure is composed of cylindrical pools arranged in series, and adjacent buffer pools are connected by overflow weirs. The water level difference calculation formula reflects the balance relationship between kinetic energy dissipation and potential energy conversion, where the kinetic energy dissipation coefficient characterizes the energy loss characteristics of the water flow passing through the buffer pool. The design of the cross-sectional area of the buffer pool needs to meet the requirements of water flow diffusion to ensure that the water flow entering the next-stage buffer pool has a uniform velocity distribution. The graded design drainage flow rate corresponds to the rated operating point of each pump group, and by matching the pump group characteristic curve and the hydraulic parameters of the buffer pool, the system efficiency is optimized.

[0037] The dynamic water level difference between the buffer pools forms a natural head adjustment mechanism. When the flow rate of the upstream pump group increases instantaneously, the water level difference increases accordingly, and the flow rate fluctuation is buffered through potential energy accumulation. On the contrary, when the flow rate decreases, the water level difference decreases, and the stored potential energy is gradually released to maintain the stability of the downstream flow rate. This self-adaptive adjustment mechanism based on Bernoulli's principle effectively suppresses the pressure pulsation caused by the start and stop of the pump group and provides stable water flow conditions for the test section.

[0038] The value of the kinetic energy dissipation coefficient is closely related to the internal diversion structure of the buffer pool. Energy dissipation grids are arranged in a staggered pattern inside the pool to promote energy dissipation by increasing the turbulence intensity of the water flow. The angle design of the flow deflector causes the water flow to rotate, enhancing the mixing effect while extending the water flow path. These structural measures enable the buffer pool not only to have a flow stabilization function but also to effectively eliminate large-scale vortices in the water flow, improving the quality of the flow field in the test section.

[0039] Step S3: Real-time monitor the drainage flow rate and the bed elevation data through the sensor matrix; In some embodiments, the sensor matrix in step S3 includes: an electromagnetic flowmeter arranged in the drainage pipeline, installed at the confluence of each drainage branch pipe to monitor the change in the total drainage flow rate in real time. Laser ranging sensors distributed annularly along the pile circumference, equally spaced circumferentially along the pile foundation model, measure the bed elevation at different azimuth angles around the pile by emitting laser beams. Pore water pressure sensors buried in the riprap protection layer, with the pore water pressure sensors buried at different depths inside the riprap protection layer to capture the change in the pore water pressure gradient during the seepage process. The data of each sensor is transmitted to the central controller through an industrial bus to form a multi-dimensional monitoring network, providing real-time data support for dynamic regulation.

[0040] Exemplarily, the electromagnetic flowmeter is installed in the vertical pipe section between the pump group outlet and the buffer pool, and the instantaneous flow rate is measured using the Faraday electromagnetic induction principle. The measuring probe adopts a full-bore structure to avoid flow field disturbance, and the lining material is selected as polyurethane rubber to enhance wear resistance. The signal converter is built-in with a temperature compensation module to eliminate the measurement deviation caused by the change in the water body conductivity. Multiple flowmeters adopt a master-slave synchronous acquisition mode to ensure the timing consistency of the flow data of each branch.

[0041] The laser ranging sensor group is arranged circumferentially along the pile foundation model, and the installation bracket has a three-dimensional fine-tuning function to achieve accurate focusing. The sensor emits laser beams in an inclined incident manner, and calculates the change in the bed elevation by receiving the position offset of the reflected light spot. The system uses wavelength diversity technology to eliminate the reflection interference on the water surface, and the adaptive filtering algorithm effectively suppresses the measurement noise caused by bubbles and suspended solids. The circumferential measurement data is reconstructed into the three-dimensional shape of the bed through polar coordinate transformation, and the time series analysis reveals the expansion mode of the scouring pit.

[0042] The pore water pressure sensors are embedded at different depths in the riprap layer, and the probe-type structure design ensures close contact with the surrounding medium. The sensor adopts a double diaphragm structure to isolate mechanical stress interference, and the capillary passage balances the hydrostatic pressure. The measurement data reflects the dynamic changes in the seepage field inside the protection layer, and the evolution law of the permeability coefficient is inverted through Darcy's law. The fusion processing of multi-physical field data establishes a correlation model between the pore water pressure gradient and the surface shear stress, providing a criterion for judging the critical state of the protection layer failure.

[0043] Step S4: Dynamically adjust the output power of the multi-stage drainage pump set based on the bed elevation data to achieve drainage control.

[0044] During the dynamic adjustment process, a feedback relationship between the scour depth and the drainage rate is established based on the bed elevation data. When the scour rate in a local area is monitored to be abnormal, the system automatically adjusts the output power of the drainage pump set in the corresponding area, and balances the flow field around the pile through flow redistribution. The power adjustment algorithm comprehensively considers the influence of the shear stress gradient on sediment incipience, and adopts a combination of axial and lateral compensation to correct the drainage pressure. This closed-loop control system can effectively suppress the flow field distortion caused by uneven sediment transport and maintain the stability of the flow pattern structure during the test.

[0045] In some embodiments, in step S4: Dynamically adjust the output power of the multi-stage drainage pump set based on the bed elevation data, ; where represents the dynamic pressure compensation amount, represents the bed shear stress gradient along the mainstream direction x, represents the bed shear stress gradient along the transverse direction y, represents the axial compensation coefficient, represents the transverse compensation coefficient, t represents the cumulative time of the drainage process. A power adjustment mechanism is established by quantifying the non-uniformity of the spatial distribution of the bed shear stress. In the formula, the square operation of the axial gradient term highlights the sensitive area of the stress change in the mainstream direction. When a significant pressure difference is formed between the upstream and downstream surfaces of the pile, the square operation amplifies the regulation demand in this area. The transverse gradient integral term focuses on the circumferential stress difference generated by the flow around the pile, and the integral operation accumulated over time reflects the continuous effect of lateral scour. The physical meaning of each compensation coefficient is to balance the energy distribution relationship between the dominant longitudinal scour and the lateral diffusion effect, and its numerical characteristics are determined by the energy dissipation characteristics at different stages of scour development.

[0046] Exemplarily, a sensor array arranged along the axis of the pile monitors the longitudinal pressure change, and the gradient of the bed shear stress along the mainstream direction x is calculated in combination with the boundary layer velocity profile. The sensor group arranged circumferentially captures the pressure fluctuations generated by the flow around the pile, and the gradient of the bed shear stress along the transverse direction y is calculated through discretization processing. The data processing algorithm uses spatial interpolation technology to fill the measurement gaps and calculates the gradient components in each direction by the finite difference method. This gradient analysis method can accurately identify the shear stress mutation area at the edge of the scour pit and provide spatial characteristic information for dynamic compensation.

[0047] Exemplarily, the implementation of the dynamic pressure compensation amount can be achieved by adjusting the pump set speed through a frequency converter. When the axial gradient increases significantly, the system preferentially increases the output power of the pump set in the corresponding area to enhance the water flow energy in the mainstream direction to balance the stress distribution. The continuous accumulation of the transverse gradient triggers the coordinated regulation of the circumferential pump set, and the flow rate redistribution is achieved by adjusting the valve opening of the annular pipeline. The superimposed effect of the dynamic pressure compensation amount enables the pump set power output to always maintain a dynamic match with the bed surface stress state, effectively suppressing the imbalance of the flow field energy level caused by the development of scouring.

[0048] It can be understood that step S2 (multi-stage pump group staged control), step S3 (sensor monitoring), and step S4 (dynamic adjustment) of the present application together constitute a closed-loop feedback control system: (1) The triggering of stage switching depends on real-time monitoring data In step S2, "increasing the drainage rate in stages" is not preset based on a fixed time, but is dynamically triggered by the sensor data in step S3.

[0049] Initial acceleration stage to transition adjustment stage: When the sensor detects that the bed surface settlement rate exceeds the threshold (i.e., satisfying in step S3), the system automatically triggers the start time of the transition stage t 0, and the sign function sgn in the three-segment exponential acceleration model used for "increasing the drainage rate in stages" in step S2 becomes 1.

[0050] Transition adjustment stage to target stable stage: When the change in the bed surface elevation tends to be stable (the in the S3 data drops below the bed surface settlement rate threshold), the pump set enters the steady-state control mode.

[0051] Through stage division, it responds to the change in the bed surface scouring state, and the scouring state is real-time feedback through sensor data (step S3). This data-driven stage switching ensures the precise matching of the drainage rate adjustment and the sediment transport dynamics.

[0052] (2) Dynamic power compensation is based on real-time data feedback Direct regulation of the bed surface elevation data: The input parameters and in the dynamic adjustment formula in step S4 need to be calculated through the sensor data in step S3: The laser rangefinder sensor provides the spatial distribution of the bed surface elevation, and in combination with the flow velocity field model, and are inverted; The data of the spatial pore water pressure sensor is used to assist in correcting the influence of the bed surface permeability on the shear stress.

[0053] (3) The multi-stage drainage pump set provides a physical execution basis for dynamic control Redundancy and flexibility of the staged pump group. The design of the multi-stage drainage pump group in step S2 (such as multiple variable-frequency pumps in parallel) provides hardware support for the dynamic adjustment in step S4: Power fine-tuning: By adjusting the speed of a single pump (instead of starting and stopping), continuous and smooth control of the drainage rate is achieved. Regional control: If the sensor matrix detects scouring differences in different directions of the pile foundation (obtained from the monitoring data in step S3), the power of the corresponding pump group can be independently adjusted (performing the actions in step S4) to achieve local correction of the flow field.

[0054] Synergistic effect of the buffer pool. The multi-stage buffer pool structure cooperates with the pump group to absorb the flow rate fluctuations during the dynamic adjustment. For example: When the power of a certain pump group suddenly increases, the buffer pool dissipates kinetic energy through the water level difference ΔH formula to avoid flow field distortion in the test section.

[0055] Exemplarily, through the sensor matrix in step S3, the flow field-bed surface coupling state (such as flow rate, elevation, pore water pressure) is captured in real time. When a sudden drop in the bed surface elevation is monitored, the dynamic pressure compensation amount is calculated according to step S4, and the pump group power adjustment strategy is determined, and the bed shear stress Gradient along the mainstream direction x increases, and the power of the corresponding pump group needs to be increased; in step S2, the multi-stage drainage pump group responds to the instruction and executes the calculation formula of the three-stage exponential acceleration model. Through the hierarchical control mechanism of the multi-stage pump group (such as stage switching, power distribution), the adjustment is carried out, activating the standby pump or increasing the speed of the existing pump, and at the same time, the buffer pool suppresses the flow impact. After the adjustment, the elevation of the backflow surface monitored in step S3 tends to be stable, and the system enters the steady-state control.

[0056] Through the synergistic effect of similarity theory guidance, hierarchical flow control, real-time monitoring feedback and dynamic compensation adjustment, the present application significantly improves the simulation fidelity of hydrodynamic conditions in the scouring test, enabling test data such as scouring rate and scouring pit morphology to accurately reflect the pile foundation scouring law in the actual marine environment, providing a reliable basis for engineering protection design.

[0057] On the other hand, the present invention also provides a drainage control system for the wind power pile foundation scouring test based on a large-scale flume, which executes the drainage control method for the wind power pile foundation scouring test based on a large-scale flume described in any one of the above, such as Figure 2 shown, the control system includes a target drainage rate determination module, a drainage rate increase determination module, and a drainage rate dynamic adjustment module; The target drainage rate determination module is used to calculate the target drainage rate based on the drainage similarity criterion; The drainage rate increase determination module is connected to the target drainage rate determination module and is used to control the drainage process by using a multi-stage drainage pump group to increase the drainage rate from the initial value to the target drainage rate in stages; The drainage rate dynamic adjustment module, which is connected to the drainage rate increase determination module, is used to monitor the drainage flow rate and the bed surface elevation data in real time through a sensor matrix; and dynamically adjust the output power of the multi-stage drainage pump group based on the bed surface elevation data to achieve the control of drainage.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A drainage control method for the scour test of wind power pile foundations based on a large-scale flume, characterized in that, The control method includes the following steps: Step S1: Calculate the target drainage rate based on the drainage similarity criterion; Step S2: Use a multi-stage drainage pump set to control the drainage process, so that the drainage rate increases from the initial value to the target drainage rate in stages; In the process of increasing in stages, a three-stage exponential acceleration model is adopted, and the calculation formula is: ； Among them, q(t) represents a function of the drainage rate varying with time; q tar represents the target drainage rate, α represents the acceleration coefficient, β represents the attenuation factor of the transition section, t 0 represents the starting time of the transition section, t represents the cumulative time of the drainage process, and sgn represents the sign function; Step S3: Real-time monitor the drainage flow rate and the elevation data of the bed surface through a sensor matrix; Step S4: Dynamically adjust the output power of the multi-stage drainage pump set based on the elevation data of the bed surface to achieve the control of drainage.

2. The drainage control method for the wind power pile foundation scour test based on a large-scale flume according to claim 1, wherein When the following formula is satisfied, the start time of the transition section is triggered t 0: ； Among them, represents the bed surface settlement rate, h th represents the threshold value of the bed surface settlement rate.

3. The drainage control method for the scour test of wind power pile foundation based on a large-scale flume according to claim 2, wherein, sgn( t - t 0) specifically as follows: When t ≤ t 0, sgn( t - t 0) = -1; When t > t 0, sgn( t - t 0) = 1.

4. The drainage control method for the scour test of wind power pile foundations based on a large-scale flume according to claim 1, wherein In step S2, the outlet of the multi-stage drainage pump set is connected to a multi-stage buffer pool structure, and the water level difference between adjacent buffer pools satisfies the following relational expression: ； in, represents the water level difference between adjacent buffer tanks, K represents the kinetic energy dissipation coefficient, A represents the cross-sectional area of the buffer tank, g represents the gravitational acceleration, and q represents the graded design drainage flow of the multi-stage buffer tank system.

5. The drainage control method for the scour test of wind power pile foundations based on a large-scale flume according to claim 1, wherein, In step S4: Dynamically adjust the output power of the multi-stage drainage pump set based on the elevation data of the bed surface, ; wherein, represents the dynamic pressure compensation amount, represents the bed shear stress gradient along the mainstream direction x, represents the bed shear stress gradient along the transverse direction y, represents the axial compensation coefficient, represents the transverse compensation coefficient, t represents the cumulative time of the drainage process.

6. The drainage control method for the scour test of wind power pile foundation based on a large-scale flume according to claim 1, wherein In step S3, the sensor matrix includes: an electromagnetic flowmeter arranged in the drainage pipeline; laser ranging sensors distributed annularly along the pile circumference; pore water pressure sensors buried in the riprap protection layer.

7. Drainage control system for scour test of wind power pile foundation based on large-scale flume, characterized in that Implement the drainage control method for the scour test of the wind power pile foundation based on a large-scale flume according to any one of claims 1-6. The control system includes a target drainage rate determination module, a drainage rate increase determination module, and a drainage rate dynamic adjustment module; The target drainage rate determination module is used to calculate the target drainage rate based on the drainage similarity criterion; The drainage rate increase determination module is connected to the target drainage rate determination module and is used to control the drainage process by using a multi-stage drainage pump set, so that the drainage rate increases from the initial value to the target drainage rate in stages; The drainage rate dynamic adjustment module is connected to the drainage rate increase determination module and is used to real-time monitor the drainage flow rate and the elevation data of the bed surface through a sensor matrix; dynamically adjust the output power of the multi-stage drainage pump set based on the elevation data of the bed surface to achieve the control of drainage.

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