Drainage control method and system for wind turbine pile foundation scour test based on large-scale water flume

Abstract

The present invention relates to the technical field of drainage control for wind turbine pile foundation scour tests, and discloses a drainage control method and system for wind turbine pile foundation scour tests based on a large-scale water flume. First, the target drainage rate is calculated based on the drainage similarity criterion to ensure the dynamic similarity between the model test and the prototype working condition. Secondly, a multi-stage drainage pump group is used to implement phased speed increase control, and the bed flow field distortion caused by power mutation in the traditional single pump system is avoided through progressive flow regulation, thereby 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 of drainage flow and bed morphology in real time, providing characteristic data with high temporal and spatial resolution for subsequent dynamic regulation. Finally, the drainage power is dynamically compensated based on the real-time feedback of the bed elevation data, and the velocity field adaptive adjustment mechanism is realized to effectively suppress the flow field offset error caused by sediment transport during the test.

Description

Technical Field

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

[0002] As the global energy structure transitions towards cleaner energy, offshore wind power has become an important direction for renewable energy development. The pile foundation structure supporting offshore wind turbines is exposed to a complex marine hydrodynamic environment for a long time, and its stability is directly related to the operational safety of the entire power generation system. Under the action of periodic hydrodynamic loads such as waves and tides, local scour pits are easily formed around the pile body. This phenomenon of sediment migration caused by the interaction between water flow and structure will significantly weaken the lateral bearing capacity of the pile foundation. When the scour depth exceeds the critical threshold, it may cause serious consequences such as structural resonance, fatigue damage, and even overall overturning. Therefore, simulating the evolution process of pile foundation scour through physical model experiments and in-depth research on the scour formation mechanism and development laws have important engineering value for optimizing foundation structure design and formulating effective protection measures.

[0003] Accurately replicating the hydrodynamic conditions of real-world ocean conditions in a laboratory setting is the core technology for conducting pile foundation scour simulation tests. To overcome scale effects, these tests often utilize large-scale physical models, such as large-scale flumes. These models require flume dimensions and sediment deposit areas that are dozens of times larger than those of typical small flumes, leading to long drainage times and difficulty controlling the drainage process. Furthermore, the test system must maintain a flow field that maintains dynamic similarity to the prototype, ensuring that key parameters such as the model's velocity distribution and shear stress accurately reflect the physical processes in the actual project. Precise control of the velocity field is crucial for test effectiveness. Flow velocity not only directly influences the initiation and transport of sediment on the bed but also, by altering the morphology of the vortex structure around the pile, influences the evolution of the scour pit from initial formation to dynamic equilibrium. Deviations in the velocity simulation will distort key parameters such as the scour rate and maximum scour depth, rendering the test conclusions ineffective for engineering practice.

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

[0005] In order to improve the simulation accuracy of the wind turbine pile foundation scour test, the present invention provides a drainage control method and system for the wind turbine pile foundation scour test based on a large-scale water flume. The control method includes the following steps:

[0006] Step S1, calculating a target drainage rate based on a drainage similarity criterion;

[0007] 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;

[0008] The phased increase process adopts a three-stage exponential acceleration model, and the calculation formula is:

[0009] ;

[0010] in, q(t) A function that represents 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;

[0011] Step S3: Real-time monitoring of drainage flow and bed elevation data through a sensor matrix;

[0012] Step S4: dynamically adjusting the output power of the multi-stage drainage pump group based on the bed elevation data to achieve drainage control.

[0013] Furthermore, when the following equation is satisfied, the transition start time is triggered: t 0:

[0014] ;

[0015] in, represents the bed sedimentation rate, h th Indicates the bed subsidence rate threshold.

[0016] Furthermore, sgn( t - t 0) Specifically:

[0017] when t ≤ t 0, sgn( t - t 0)=-1;

[0018] when t > t 0, sgn( t - t 0)=1.

[0019] 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:

[0020] ;

[0021] 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 acceleration of gravity, and q represents the graded design drainage flow of the multi-stage buffer tank system.

[0022] Furthermore, in step S4: dynamically adjusting the output power of the multi-stage drainage pump group based on the bed elevation data,

[0023] ;in, Indicates the dynamic pressure compensation amount, represents the bed shear stress Along the main flow direction x gradient, represents the bed shear stress Along the horizontal y gradient, represents the axial compensation coefficient, represents the lateral compensation coefficient, t Indicates the cumulative time of the drainage process.

[0024] Furthermore, the sensor matrix in step S3 includes: an electromagnetic flowmeter arranged in the drainage pipe; laser ranging sensors distributed in a ring around the pile; and pore water pressure sensors buried in the riprap protective layer.

[0025] On the other hand, the present invention also provides a drainage control system for a wind turbine pile foundation scour test based on a large-scale water flume, which executes any of the above-mentioned drainage control methods for a wind turbine pile foundation scour test based on a large-scale water flume, wherein the control system includes a target drainage rate determination module, a drainage rate increase determination module, and a drainage rate dynamic adjustment module;

[0026] The target drainage rate determination module is used to calculate the target drainage rate based on the drainage similarity criterion;

[0027] The drainage rate increase determination module is connected to the target drainage rate determination module and is used to control the drainage process using a multi-stage drainage pump group so that the drainage rate increases from an initial value to the target drainage rate in stages;

[0028] 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 the sensor matrix; dynamically adjust the output power of the multi-stage drainage pump group based on the bed elevation data to achieve drainage control.

[0029] The embodiments of the present invention have the following technical effects:

[0030] The present invention effectively improves the hydrodynamic simulation accuracy of wind power pile foundation scour tests by constructing a closed-loop system that combines drainage similarity criteria with dynamic feedback control. First, the target drainage rate is calculated based on the drainage similarity criteria to ensure the dynamic similarity between the model test and the prototype working conditions, so that key parameters such as the velocity field and shear stress meet the matching requirements of the geometric scale and the time scale, laying a theoretical foundation for the physical similarity of the scour process. Secondly, a multi-stage drainage pump group is used to implement phased speed increase control. Through progressive flow regulation, the bed flow field distortion caused by power mutation in the traditional single pump system is avoided, and the natural development process of the vortex structure around the pile is maintained. At the same time, the all-round monitoring system of the sensor matrix captures the coupled changes of drainage flow and bed morphology in real time, providing characteristic data with high temporal and spatial resolution for subsequent dynamic regulation. Finally, the drainage power is dynamically compensated based on the real-time feedback bed elevation data, realizing the velocity field adaptive adjustment mechanism, which effectively suppresses the flow field offset error caused by sediment transport during the test. This technical solution significantly improves the simulation fidelity of hydrodynamic conditions in scour tests through the synergistic effect of similarity theory guidance, graded flow control, real-time monitoring feedback, and dynamic compensation adjustment, so that test data such as scour rate and scour pit morphology can accurately reflect the scour laws of pile foundations in actual marine environments, providing a reliable basis for engineering protection design. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a flow chart of a drainage control method for a wind power pile foundation scour test based on a large-scale water flume provided by an embodiment of the present invention;

[0033] Figure 2 It is a structural schematic diagram of a drainage control system for a wind power pile foundation scour test based on a large-scale water flume provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0035] In order to improve the simulation accuracy of wind turbine pile foundation scour test, the present invention provides a drainage control method and system for wind turbine pile foundation scour test based on a large-scale water tank, such as Figure 1 As shown, the control method includes the following steps:

[0036] Step S1, calculating a target drainage rate based on a drainage similarity criterion;

[0037] In the wind turbine pile foundation scour model test, the accurate simulation of the hydrodynamic conditions depends on the precise control of the drainage rate. At the beginning of the test, the target drainage rate needs to be determined according to the drainage similarity criterion. This criterion establishes the dynamic similarity between the model and the prototype through the correspondence 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 velocity distribution and shear stress in the model test remain dynamically similar to the prototype working 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. The flow 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 repeated here.

[0038] 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;

[0039] For example, a multi-stage drainage pump group is composed of several centrifugal pumps of different powers connected in parallel, and the pumps are coordinated by a frequency converter. In the initial drainage stage, a low-power pump group is used to maintain the basic flow rate. As the test progresses, the medium and high-power pump groups are activated in stages to gradually increase the drainage rate to the target value. The phased speed increase strategy can avoid the sudden change in flow caused by the full-load start-up of a single pump, and prevent the stability of the flow field in the test section from being destroyed by the drainage shock. During the switching process of the pump groups, there are overlapping working intervals between adjacent pump groups, and a smooth transition is achieved by flow superposition. The multi-stage pump group configuration not only improves the flow regulation resolution, but also enhances the redundancy of the system to cope with unexpected working conditions.

[0040] In some implementations, the phased increase process adopts a three-stage exponential acceleration model, and the calculation formula is:

[0041] ;

[0042] in, q(t) A function that represents the change in drainage rate over time; q tar represents the target drainage rate, α represents the acceleration coefficient, the value of which is related to the mechanical inertia of the pump unit and the water resistance characteristics of the pipeline. The optimal parameters need to be obtained through no-load test calibration; β represents the transition section attenuation factor. t0 represents the starting time of the transition period, which corresponds to the critical state when the sediment on the bed changes from static to starting. At this time, the flow field structure changes significantly, and the shear stress balance needs to be maintained by flow adjustment. t represents the cumulative time of the drainage process, and sgn represents the sign function.

[0043] Among them, the function of drainage rate changing with time is q(t) Indicates the actual drainage flow at time t (unit: m³ / s). This function is used to dynamically control the drainage rate to balance the need for rapid drainage and bed stability. t 0 is dynamically triggered by the bed surface sedimentation rate threshold, forming a closed-loop feedback control. The multi-stage buffer tank structure (ΔH calculation formula) is used in the absorption formula The kinetic energy fluctuations generated by the term.

[0044] The phased adjustment of the drainage rate utilizes a three-stage exponential acceleration model, which divides the drainage process into an initial acceleration phase, a transition adjustment phase, and a target stabilization phase. During the initial acceleration phase (t ≤ t0), the drainage rate gradually increases from the initial value, but the rate of increase is suppressed. The flow field must be established slowly during the initial stages of the test to prevent the shear stress from exceeding the critical threshold for sediment initiation, which could lead to premature scouring and deformation of the bed surface. During this period, the sediment is stationary or moving only slightly, so a low flow rate is required to maintain the initial bed surface configuration. During the transition adjustment phase (t > t0), localized scouring has already occurred on the bed surface, and the drainage rate must be increased to simulate the flow field intensity of the prototype. During the target stabilization phase, the drainage rate reaches the target value and enters a stable state, simulating the stable hydrodynamic conditions of the prototype. This allows the scour pit morphology to naturally develop to an equilibrium state, thus obtaining reliable test data. During the initial acceleration phase, it is necessary to avoid sudden increases in shear stress that could damage the bed surface; during the transition adjustment phase, the sediment transport energy level must be dynamically matched; and during the target stabilization phase, the flow field must be maintained similarly. Pump power is adjusted according to the different phases to achieve drainage rate control.

[0045] In the initial growth phase, through the exponential function Dominant, used to describe the gradual acceleration characteristics of the initial stage, through the natural attenuation characteristics of the exponential function to achieve a smooth increase in flow, so that the drainage rate increases smoothly and avoids sudden changes in flow. t - t 0)=-1, the square root term is a negative value, which suppresses the rapid increase in drainage and protects the stability of the bed surface.

[0046] Transition adjustment section, the trigger condition is the bed surface settlement rate , indicating that the sediment enters the active transport stage. The symbol function switches to sgn( t - t 0)=1, the square root term turns positive, and the drainage rate accelerates to the target value. The growth rate is slowing down but continuing to improve, matching the energy level requirements of 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 over time. This nonlinear growth rate characteristic results in: a slowdown in the later flow velocity growth rate and a gentle transition in the shear stress. The sediment in the transition adjustment section is mainly saltation, and the gentle growth rate of the square root function makes the sediment transport rate controllable and maintains the critical conditions: the sediment transport rate is related to the high power of the flow velocity, and the slow growth rate can avoid the sudden change in bed morphology caused by the exponential growth of the sediment transport rate; it also keeps the bed shear stress close to the critical value for sediment initiation, ensuring both the continuity of sediment transport and the prevention of excessive scouring. Therefore, the square root function controls the nonlinear growth of the drainage rate, reduces the rate of change of the later flow velocity, optimizes the distribution of water flow energy, thereby suppressing the risk of secondary scouring caused by inertia effects and ensuring the natural development of the scouring process.

[0047] In the target stable phase, the exponential function term approaches 1. The growth rate of the item has slowed down, and the system has maintained a constant flow rate through dynamic compensation.

[0048] The introduction of the sign function sgn automatically reverses the flow rate trend before and after the transition period. Before the transition period begins, the sign function is negative, and the square root term exerts a suppressive effect, preventing initial flow rate overshoot. Once the test duration exceeds the transition period, the sign function becomes positive, and the square root term begins to exert a reinforcing effect, rapidly driving the drainage rate toward the target value. This bidirectional regulation mechanism ensures a continuous first-order derivative of the flow curve at critical turning points, preventing damage to the test equipment from mechanical shock.

[0049] In some embodiments, sgn( t - t 0) Specifically:

[0050] when t ≤ t 0, sgn( t - t 0)=-1, which is a negative value, indicating that the sudden change of drainage rate is suppressed, the shear force of water flow is reduced, and the critical starting conditions of sediment particles are avoided from being broken; the rapid increase of drainage rate is suppressed, and the shear stress of bed surface is prevented from exceeding the limit due to sudden change of water flow in the initial stage, thus protecting the stability of bed surface. At this time, the drainage rate is mainly determined by the first item. Dominant, showing the characteristic of the index approaching the target value.

[0051] when t > t 0, sgn( t - t 0)=1, a positive value, indicates that the drainage process of the transition section is accelerated to ensure that the target drainage rate is reached quickly q tar , meeting the test efficiency requirements; bidirectional dynamic adjustment of drainage rate is achieved through sign inversion.

[0052] The introduction of a sign function automatically reverses the flow rate trend before and after the transition. Before the transition start time, the sign function is negative, and the square root term exerts a suppressive effect, preventing initial flow overshoot. Once the test duration exceeds the transition start time, the sign function becomes positive, and the square root term begins to exert a reinforcing effect, rapidly pushing the drainage rate toward the target value. This bidirectional regulation mechanism ensures a continuous first-order derivative of the flow curve at critical turning points, preventing damage to the test equipment from mechanical shock.

[0053] Therefore, in the drainage control of wind turbine pile foundation scour test, the design of the sgn function achieves the following key goals:

[0054] (1) Prevent bed surface from collapsing

[0055] pass t The sign reversal at time 0 accurately controls the growth slope of the drainage rate.

[0056] Initial stage ( t ≤ t 0) to reduce the shear force of the water flow and avoid breaking the critical starting conditions of the sediment particles.

[0057] (2) Optimizing energy dissipation

[0058] Square root term The introduction of the flow rate change rate , effectively attenuating the inertial energy of water flow and reducing the risk of secondary scour (such as collapse of the edge of the scour pit).

[0059] (3) Experimental repeatability

[0060] The drainage stage is clearly divided by the sgn function to ensure strict consistency of the time-rate curves of different test batches and improve data comparability.

[0061] In some implementations, the transition start time is triggered when the following equation is satisfied: t 0:

[0062] ;

[0063] in, represents the bed sedimentation rate, h th Indicates the bed subsidence rate threshold.

[0064] The triggering mechanism for the start of the transition phase is based on real-time monitoring of the bed sedimentation rate. This rate is calculated using time-series data from a laser ranging sensor, using a sliding window difference method to eliminate measurement noise. When the sedimentation rate exceeds a preset threshold, it indicates that the bed sediment is actively transporting. At this point, the interaction between the flow field and the bed enters a nonlinear phase, necessitating the activation of the transition phase acceleration mode to match the energy level requirements. The threshold is set with reference to the critical starting shear stress of the sediment, and the response characteristics of different particle size groups are determined through flume calibration tests.

[0065] The physical significance of the bed sedimentation rate threshold lies in identifying the critical point at which sediment transport states transition. When the sedimentation rate falls below the threshold, sediment movement is primarily the rolling and sliding of individual particles. Maintaining a low drainage rate at this point prevents excessive disturbance. Above the threshold, the bed surface experiences jumping and even suspended motion of groups of particles, significantly increasing flow field energy demand. The system switches to transition acceleration mode, promptly increasing the power of the drainage pumps to ensure a dynamic balance between shear stress and sediment transport intensity.

[0066] The trigger mechanism relies on the collaborative work of a high-speed data acquisition system and a real-time control algorithm. Laser ranging data is transmitted to the processor at a fixed sampling frequency, where instantaneous sedimentation rates are calculated through digital filtering and real-time differentiation. When the sedimentation rates at multiple consecutive sampling points exceed a threshold, the system determines that the trigger condition has been met and immediately initiates the transition control logic. This dual verification mechanism effectively prevents false triggering caused by occasional interference and improves the reliability of state switching.

[0067] In some embodiments, 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:

[0068] ;

[0069] 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 acceleration of gravity, and q represents the graded design drainage flow of the multi-stage buffer tank system.

[0070] The multi-stage buffer tank structure consists of cylindrical tanks arranged in series, with adjacent buffer tanks connected by overflow weirs. The water level difference calculation formula reflects the balance between kinetic energy dissipation and potential energy conversion, where the kinetic energy dissipation coefficient characterizes the energy loss characteristics of water flowing through the buffer tank. The buffer tank cross-sectional area must be designed to meet water flow diffusion requirements to ensure a uniform velocity distribution of water entering the next buffer tank. The graded discharge flow rate is designed to correspond to the rated operating point of each pump unit. By matching the pump unit characteristic curve with the buffer tank hydraulic parameters, the system efficiency is optimized.

[0071] The dynamic water level difference between the buffer tanks creates a natural head regulation mechanism. When the flow rate of the upstream pump group increases instantaneously, the water level difference increases accordingly, buffering flow fluctuations through accumulated potential energy. Conversely, when the flow rate decreases, the water level difference decreases, and the stored potential energy is gradually released to maintain stable downstream flow. This adaptive regulation mechanism, based on the Bernoulli principle, effectively suppresses pressure pulsations caused by the start and stop of the pump group, ensuring stable water flow conditions in the test section.

[0072] The value of the kinetic energy dissipation coefficient is closely related to the internal flow diversion structure of the buffer tank. Staggered energy dissipation grids are installed within the tank to increase the turbulence intensity of the water flow and promote energy dissipation. The angled design of the deflectors creates a rotational motion in the water flow, extending the flow path and enhancing mixing. These structural measures not only ensure flow stabilization in the buffer tank, but also effectively eliminate large-scale vortices in the water flow, improving the flow field quality of the test section.

[0073] Step S3: Real-time monitoring of drainage flow and bed elevation data through a sensor matrix;

[0074] In some embodiments, the sensor matrix in step S3 includes: electromagnetic flowmeters arranged in drainage pipes, installed at the confluence of each drainage branch pipe, to monitor changes in total drainage flow in real time. Laser ranging sensors distributed in a circular pattern around the pile, arranged equidistantly along the circumference of the pile foundation model, and measuring the bed elevation at different azimuths around the pile by emitting laser beams. Pore water pressure sensors embedded in the riprap protective layer, at different depths within the riprap protective layer, capture changes in pore water pressure gradients during seepage. Data from each sensor is transmitted to a central controller via an industrial bus, forming a multi-dimensional monitoring network that provides real-time data support for dynamic regulation.

[0075] For example, an electromagnetic flowmeter is installed in the vertical pipe section between the pump outlet and the buffer tank, measuring instantaneous flow rate using the Faraday principle of electromagnetic induction. The measuring probe uses a full-bore structure to avoid flow field disturbances, and the lining material is polyurethane rubber for enhanced wear resistance. The signal converter has a built-in temperature compensation module to eliminate measurement errors caused by changes in water conductivity. Multiple flowmeters use a master-slave synchronization acquisition mode to ensure the temporal consistency of flow data across each branch.

[0076] Laser ranging sensors are arranged along the circumference of the pile foundation model, with mounting brackets featuring three-dimensional fine-tuning for precise focus. The sensors emit laser beams at an oblique incidence and calculate bed elevation changes by detecting the positional offset of the reflected light spot. The system uses wavelength diversity technology to eliminate interference from water surface reflections, and an adaptive filtering algorithm effectively suppresses measurement noise caused by bubbles and suspended matter. Circumferential measurement data is transformed into polar coordinates to reconstruct the three-dimensional bed surface, and time series analysis reveals the expansion pattern of the scour pit.

[0077] Pore-water pressure sensors are embedded at varying depths within the riprap layer. Their probe-type design ensures close contact with the surrounding medium. The sensors utilize a dual-diaphragm structure to isolate mechanical stress interference, while capillary channels balance hydrostatic pressure. The measured data reflects the dynamics of the seepage field within the protective layer, and Darcy's law is used to invert the evolution of the permeability coefficient. Multi-physics data fusion is used to establish a correlation model between pore-water pressure gradients and surface shear stress, providing a criterion for determining critical failure states of the protective layer.

[0078] Step S4: dynamically adjusting the output power of the multi-stage drainage pump group based on the bed elevation data to achieve drainage control.

[0079] During the dynamic adjustment process, a feedback relationship between scour depth and drainage rate is established based on bed elevation data. When abnormal scour rates are detected in a local area, the system automatically adjusts the output power of the drainage pumps in that area, balancing the flow field around the piles through flow redistribution. The power adjustment algorithm comprehensively considers the impact of shear stress gradients on sediment mobilization and uses a combination of axial and lateral compensation to correct drainage pressure. This closed-loop control system effectively suppresses flow field distortion caused by uneven sediment transport and maintains the stability of the flow structure during the test.

[0080] In some embodiments, in step S4: dynamically adjusting the output power of the multi-stage drainage pump group based on the bed elevation data,

[0081] ;in, Indicates the dynamic pressure compensation amount, represents the bed shear stress Along the main flow direction x gradient, represents the bed shear stress Along the horizontal y gradient, represents the axial compensation coefficient, represents the lateral compensation coefficient, t Indicates the cumulative time of the drainage process.

[0082] The power regulation mechanism is established by quantifying the spatial heterogeneity of the shear stress distribution on the bed surface. The square operation highlights the sensitive area of ​​stress change in the mainstream direction. When a significant pressure difference is formed between the upstream and downstream sides of the pile, the square operation amplifies the control demand in this area. The focus is on the circumferential stress differences generated by the flow around the pile. The time-accumulated integral reflects the ongoing effects of lateral scour. The physical significance of each compensation coefficient lies in balancing the energy distribution relationship between the dominant longitudinal scour and the lateral diffusion effect. Its numerical characteristics are determined by the energy dissipation characteristics at different stages of scour development.

[0083] For example, a sensor array arranged along the pile axis monitors the longitudinal pressure change, and the bed shear stress is calculated by combining the boundary layer velocity profile. The x gradient along the mainstream direction. The circumferentially arranged sensor group captures the pressure fluctuations generated by the flow and calculates the bed shear stress through discretization processing. Along the lateral y gradient. The data processing algorithm uses spatial interpolation to fill measurement gaps and the finite difference method to calculate the gradient components in all directions. This gradient analysis method can accurately identify areas of sudden shear stress changes at the edges of scour pits, providing spatial characteristic information for dynamic compensation.

[0084] For example, dynamic pressure compensation can be implemented by adjusting the pump speed via a frequency converter. When the axial gradient increases significantly, the system prioritizes increasing the output power of the pumps in the corresponding area, enhancing the energy of the mainstream water flow to balance the stress distribution. The continued accumulation of lateral gradients triggers the coordinated regulation of the circumferential pumps, achieving flow redistribution by adjusting the valve opening of the annular pipeline. The superposition of dynamic pressure compensation ensures that the pump power output is always dynamically matched to the bed stress state, effectively suppressing the imbalance of flow field energy levels caused by the development of scour.

[0085] It can be understood that step S2 (multi-stage pump group stage control), step S3 (sensor monitoring) and step S4 (dynamic adjustment) of the present application together constitute a closed-loop feedback control system:

[0086] (1) The triggering of phase switching depends on real-time monitoring data

[0087] The “increase of drainage rate in stages” in step S2 is not based on a fixed time preset, but is dynamically triggered by the sensor data in step S3.

[0088] Initial acceleration stage to transition adjustment stage: When the sensor detects that the bed surface settlement rate exceeds the threshold (i.e., the ), the system automatically triggers the transition start time t 0, the sign function sgn in the three-stage exponential acceleration model used in the “increase the drainage rate in stages” in step S2 becomes 1.

[0089] Transition adjustment stage to target stable stage: When the bed elevation changes tend to be stable (S3 data When the bed surface subsidence rate drops below the bed surface subsidence rate threshold), the pump group enters the steady-state control mode.

[0090] By dividing the drainage system into stages, the system responds to changes in the bed scour state, which is fed back in real time via sensor data (step S3). This data-driven stage switching ensures that drainage rate adjustments are precisely matched to sediment transport dynamics.

[0091] (2) Dynamic power compensation based on real-time data feedback

[0092] Direct control of bed elevation data: dynamic adjustment of input parameters in the formula in step S4 and , which needs to be calculated through the sensor data of step S3: the laser ranging sensor provides the spatial distribution of bed elevation, combined with the velocity field model inversion and ; Spatial pore water pressure sensor data assists in correcting the effect of bed permeability on shear stress.

[0093] (3) Multi-stage drainage pump group provides physical execution basis for dynamic control

[0094] The redundancy and flexibility of the tiered pump groups. The design of the multi-stage drainage pump group in step S2 (e.g., multiple variable-frequency pumps in parallel) provides hardware support for the dynamic adjustments in step S4: Power fine-tuning: By adjusting the speed of individual pumps (rather than starting and stopping them), continuous and smooth control of the drainage rate is achieved. Regionalized control: If the sensor matrix detects scour differences in different directions of the pile foundation (obtained from the monitoring data in step S3), the power of the pump group in the corresponding direction can be independently adjusted (execution of the action in step S4), achieving local correction of the flow field.

[0095] The multi-stage buffer tank structure works in conjunction with the pump unit to absorb flow fluctuations during dynamic adjustment. For example, when a pump unit experiences a sudden power surge, the buffer tank dissipates kinetic energy using the water level difference ΔH formula, avoiding flow field distortion in the test section.

[0096] For example, the sensor matrix in step S3 captures the flow field-bed coupling state (such as flow, elevation, pore water pressure) in real time, monitors the sudden drop in bed elevation, calculates the dynamic pressure compensation amount according to step S4, determines the pump group power adjustment strategy, and the bed shear stress x gradient along the main flow direction If the flow rate increases, the corresponding pump group power needs to be increased. In step S2, the multi-stage drainage pump group responds to the command and executes the calculation formula of the three-stage exponential acceleration model. Adjustments are made through the multi-stage pump group's hierarchical control mechanisms (such as stage switching and power allocation), activating backup pumps or increasing the speed of existing pumps. Meanwhile, the buffer pool smooths out flow shocks. After the adjustments, step S3 monitors that the backflow surface elevation has stabilized, and the system enters steady-state control.

[0097] This application significantly improves the simulation fidelity of hydrodynamic conditions in scour tests through the synergistic effect of similarity theory guidance, graded flow control, real-time monitoring feedback, and dynamic compensation adjustment, so that test data such as scour rate and scour pit morphology can accurately reflect the scour laws of pile foundations in actual marine environments, providing a reliable basis for engineering protection design.

[0098] On the other hand, the present invention also provides a wind turbine pile foundation scour test drainage control system based on a large-scale water tank, which executes any of the above-mentioned wind turbine pile foundation scour test drainage control methods based on a large-scale water tank, such as Figure 2 As shown, the control system includes a target drainage rate determination module, a drainage rate increase determination module, and a drainage rate dynamic adjustment module;

[0099] The target drainage rate determination module is used to calculate the target drainage rate based on the drainage similarity criterion;

[0100] The drainage rate increase determination module is connected to the target drainage rate determination module and is used to control the drainage process using a multi-stage drainage pump group so that the drainage rate increases from an initial value to the target drainage rate in stages;

[0101] 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 the sensor matrix; dynamically adjust the output power of the multi-stage drainage pump group based on the bed elevation data to achieve drainage control.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A drainage control method for wind turbine pile foundation scour test based on a large-scale water flume, characterized in that: The control method comprises the following steps: Step S1, calculating a target drainage rate based on a 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 that represents 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 adjusting the output power of the multi-stage drainage pump group based on the bed elevation data to achieve drainage control.

2. The drainage control method for wind power pile foundation scour test based on a large-scale water tank according to claim 1 is characterized in that: When the following formula is satisfied, the transition start time is triggered t 0: ； in, represents the bed sedimentation rate, h th Indicates the bed subsidence rate threshold.

3. The drainage control method for wind power pile foundation scour test based on a large-scale water tank according to claim 2 is characterized in that: sgn( tt 0) Specifically: when t ≤ t 0, sgn( tt 0)=-1; when t > t 0, sgn( tt 0)=1.

4. The drainage control method for wind power pile foundation scour test based on a large-scale water tank according to claim 1 is characterized in that: 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 acceleration of gravity, and q represents the graded design drainage flow of the multi-stage buffer tank system.

5. The drainage control method for wind power pile foundation scour test based on a large-scale water tank according to claim 1 is characterized in that: In the step S4: dynamically adjusting the output power of the multi-stage drainage pump group based on the bed elevation data, ;in, Indicates the dynamic pressure compensation amount, represents the bed shear stress Along the main flow direction x gradient, represents the bed shear stress Along the horizontal y gradient, represents the axial compensation coefficient, represents the lateral compensation coefficient, t Indicates the cumulative time of the drainage process.

6. The drainage control method for wind power pile foundation scour test based on a large-scale water tank according to claim 1 is characterized in that: The sensor matrix in step S3 includes: an electromagnetic flowmeter arranged in the drainage pipe; laser ranging sensors distributed in a ring around the pile; and pore water pressure sensors buried in the riprap protective layer.

7. A drainage control system for wind power pile foundation scour test based on a large-scale water tank, characterized by: The drainage control method for a wind power pile foundation scour test based on a large-scale water flume according to any one of claims 1 to 6 is implemented, wherein 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 using a multi-stage drainage pump group 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 the sensor matrix; dynamically adjust the output power of the multi-stage drainage pump group based on the bed elevation data to achieve drainage control.

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