A wind tunnel testing method applicable to scaled-down models of large floating wind turbines

Abstract

This invention discloses a wind tunnel testing method suitable for scaled-down models of large floating wind turbines. Through a six-degree-of-freedom motion platform with a sunken mechanical mechanism and a wind tunnel bottom guide design, it maximizes the space utilization of the wind tunnel testing area while ensuring accurate simulation of the boundary layer wind field profile. By deploying multiple sensors on the scaled-down model and processing the sensor measurement data, test results such as aerodynamic loads, structural internal forces, and foundation motion attitude are obtained. Wind speed probes and particle image velocimetry are used to measure the flow field changes in the wake field during the scaled-down wind turbine model test. This invention solves the problems of inaccurate boundary layer wind field profile simulation, excessive model blockage ratio, and difficulty in accurately measuring the stress on the model structure and the foundation motion attitude in wind tunnel tests of scaled-down models of large floating wind turbines, enabling accurate measurement of aerodynamic loads, structural internal forces, foundation motion attitude, and wake field characteristics.

Description

Technical Field

[0001] This invention belongs to the field of wind power generation equipment and wind tunnel testing technology, and designs a wind tunnel testing method, particularly a wind tunnel testing method suitable for a scaled-down model of a large floating wind turbine. Background Technology

[0002] With the rapid development of the wind power industry, wind turbine design is gradually becoming larger and more complex. Design methods based on engineering experience and predictive numerical tools need to be continuously calibrated using experimental data to ensure their reliability and effectiveness. Designing accurate and reliable scaled-down model experiments has significant engineering application value.

[0003] Currently, there are some wind tunnel tests conducted on scaled-down models of large floating wind turbines both domestically and internationally. Scaled-down models of floating wind turbines, consisting of an upper scaled-down wind turbine model and a lower six-degree-of-freedom motion platform, have been widely used in related fields both at home and abroad. I. Bayati and A. Fontanella et al. from the Polytechnic University of Milan conducted a series of wind tunnel tests on scaled-down floating wind turbine models between 2019 and 2023, realizing the simulation of floating body motion under wave action and the measurement of the wind turbine's structural dynamic characteristics using a six-degree-of-freedom motion platform. However, many problems remain unresolved. Currently, all related experiments involve placing the entire model within the wind tunnel test section. This leads to the following problems: Due to the difficulty in miniaturizing the mechanical structure of the six-degree-of-freedom (6DOF) motion platform, the lower 6DOF platform occupies a significant portion of the wind tunnel test section. In the experiments of I. Bayati et al., the height of the 6DOF platform accounted for over 15% of the overall model height, resulting in the impeller size of the scaled-down wind turbine model being much smaller than the maximum usable size in the wind tunnel test section, which is detrimental to improving the accuracy of the scaled-down model test results. Furthermore, the 6DOF motion platform generates a blocking effect within the wind tunnel test section during movement, increasing the overall model's blocking ratio in the experiment. The actual operating conditions of the prototype wind turbine are boundary layer wind fields. In the model test, the 6DOF motion platform occupies part of the height, preventing the wind tunnel test from generating the boundary layer wind field from the bottom of the wind turbine model, leading to inaccurate simulation of the boundary layer wind field profile. Therefore, I. Bayati et al. had to adopt a uniform flow wind field for testing in their research, resulting in a deviation between the model test's simulation of the wind field and the prototype wind turbine's operating environment.

[0004] Current wind tunnel tests of large-scale floating wind turbine models, both domestically and internationally, employ hot-wire or differential pressure anemometers in conjunction with a moving test frame for flow field measurement. While this method can measure the three-dimensional wind speed and turbulence characteristics of the flow field, each anemometer can only measure a small area near the probe. The probe position needs to be changed during the test using the moving test frame to achieve a larger flow field measurement behind the impeller surface of the wind turbine model. This leads to the following problems: only a small number of measuring points can be measured per test; changing the probe position with the moving test frame prolongs the test time for each set of operating conditions, resulting in low measurement efficiency and high test costs; and the measurement results for each measuring point within the flow field measurement range come from different time points during the test, failing to achieve synchronous measurement, thus making it impossible to measure and analyze the instantaneous characteristics of the wake vortex structure of the wind turbine model.

[0005] Meanwhile, existing wind tunnel testing methods for scaled-down models of large floating wind turbines still suffer from the problem of inaccurate measurement of the model's dynamic response, including aerodynamic loads, structural internal forces, and foundation motion attitude. All of these issues negatively impact the accuracy of wind tunnel test results for scaled-down models of large floating wind turbines.

[0006] Based on the above background, there is an urgent need to design a wind tunnel testing method suitable for scaled-down models of large floating wind turbines. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a wind tunnel testing method suitable for scaled-down models of large floating wind turbines.

[0008] The technical solution adopted in this invention is as follows:

[0009] A wind tunnel testing method applicable to a scaled-down model of a large floating wind turbine, the scaled-down model of the large floating wind turbine comprising a six-degree-of-freedom motion platform and a scaled-down wind turbine model, comprising the following steps:

[0010] A reserved space is set below the wind tunnel test section. The main mechanical structure of the six-degree-of-freedom motion platform is sunk and arranged in the reserved space. Only the upper platform of the six-degree-of-freedom motion platform is kept in the wind tunnel test section. The bottom of the tower of the scaled-down wind turbine model is fixedly installed on the upper platform.

[0011] A guide vane of the same height as the upper platform is installed on the bottom surface of the wind tunnel test section, so that the upper surface of the guide vane is flush with the surface of the upper platform on the six-degree-of-freedom motion platform; sensors are installed on the scaled-down model of the wind turbine to acquire sensor measurement data, and the inertial force component in the load data measured by the sensors is corrected to obtain the aerodynamic load, structural internal force and basic motion attitude of the scaled-down model of the wind turbine.

[0012] Particle image velocimetry was used to measure the wind speed in the flow field. A wind speed probe was installed on a moving measurement frame to measure the wind speed in the 1D and 2D cross sections downwind of the model. The particle image velocimetry results were verified, and the wake field measurement results of the scaled-down model of the wind turbine were obtained.

[0013] Furthermore, the sunken arrangement satisfies the following constraints:

[0014] (1) The sum of the height of the scaled-down model of the wind turbine and the installation height of the platform on the six-degree-of-freedom motion platform in the wind tunnel test section is less than the maximum allowable height of the wind tunnel test section;

[0015] (2) The sum of the swept area of ​​the impeller of the scaled-down model of the wind turbine and the maximum projected area of ​​the six-degree-of-freedom motion platform in the wind tunnel test section shall not exceed 10% of the cross-sectional area of ​​the wind tunnel test section;

[0016] (3) The sum of the horizontal cross-sectional diameter of the six-degree-of-freedom motion platform at the bottom height of the wind tunnel test section and twice the maximum motion radius of the six-degree-of-freedom motion platform is less than the diameter of the reserved space;

[0017] (4) The bottom diameter of the six-degree-of-freedom motion platform is smaller than the diameter of the reserved space;

[0018] (5) The sum of the reserved space height and the installation height of the six-degree-of-freedom motion platform in the wind tunnel test section is greater than the minimum electric cylinder height of the six-degree-of-freedom platform required to meet the test motion conditions.

[0019] Furthermore, the installation of sensors on the scaled-down model of the wind turbine includes: arranging fiber optic strain sensors on the front of the blades to measure blade strain during operation; installing accelerometers on the nacelle to measure hub acceleration; installing six-component force sensors at the connection between the top of the tower and the nacelle to measure the six-component force load at the top of the tower; installing six-component force sensors at the connection between the bottom of the tower and the upper platform to measure the six-component force load at the bottom of the tower; and installing a laser interferometer on the upper platform of the six-degree-of-freedom motion platform to measure the motion displacement of the upper platform.

[0020] Furthermore, the aerodynamic load is calculated based on the measurement data of the six component forces at the top of the tower and the measurement data of the hub acceleration:

[0021] F aero =F top -M rotor a hub

[0022] Among them, F aero For the aerodynamic loads of the scaled-down model of the wind turbine, F top M represents the six-component force load at the top of the wind turbine model measured by the six-component force sensor at the top of the tower. rotor For the mass matrix of the blades and hub of the scaled-down model of the wind turbine, a hub Hub acceleration of a scaled-down model of a wind turbine, measured by an accelerometer.

[0023] Furthermore, the internal forces of the structure include the modified six-component load at the top of the tower, the six-component load at the bottom of the tower, and the blade axial force;

[0024] The revised calculation method for the six-component load at the top of the tower is as follows:

[0025]

[0026] in, For the corrected six-component load at the top of the tower, M RNA Mass matrix of blades, hub, and nacelle sections for a scaled-down model of a wind turbine. Mass matrix of prototype wind turbine blades, hub, and nacelle;

[0027] The revised calculation method for the six-component load at the base of the tower is as follows:

[0028]

[0029] in, For the corrected six-component load at the base of the tower, M turbine This is the total mass matrix of the scaled-down model of the wind turbine. The total mass matrix of the prototype wind turbine;

[0030] The method for calculating the blade axial force is as follows:

[0031] F N =E blade ε blade A blade

[0032] Among them, F N E represents the axial force of the blades in a scaled-down model of a wind turbine. blade ε is the elastic modulus of the blade in a scaled-down model of a wind turbine. blade For the strain of the blade in the scaled-down model of the wind turbine, A blade The cross-sectional area of ​​the blades in the scaled-down model of the wind turbine.

[0033] Furthermore, the specific steps for measuring the wind speed in the flow field using particle image velocimetry technology include:

[0034] A tracer particle delivery device was placed behind the impeller of a scaled-down wind turbine model. During the experiment, tracer particles were delivered through the device, and a laser emitter was used to illuminate an area of ​​length 2D × width 1.5D × height 1.5D behind the scaled-down wind turbine model, where D is the diameter of the impeller of the scaled-down wind turbine model. The position changes of the tracer particles in the area were continuously captured by a high-speed camera. The captured images were then subjected to high-precision cross-correlation post-processing and artificial intelligence particle image analysis to obtain the flow field wind speed components in the velocity measurement area during the experiment.

[0035] Furthermore, the specific steps for measuring wind speed using a moving measuring frame to install a wind speed probe at the downwind 1D and 2D cross sections of the model include:

[0036] An anemometer is mounted on a moving frame that can move the anemometer to a designated position on the measurement section behind the scaled-down wind turbine model. Several measuring points are arranged on two sections at distances of 1D and 2D in the wind direction under the scaled-down wind turbine model. The wind speed component of the flow field at each measuring point is measured by moving the anemometer to verify the measurement results of the particle image velocimetry technology.

[0037] Furthermore, the method for arranging the measuring points is as follows: 4 sets of measuring points are arranged with a horizontal spacing of 0.5D and 4 sets of measuring points are arranged with a vertical spacing of 0.5D, for a total of 4×4=16 measuring points arranged in each cross section for wind speed measurement.

[0038] Furthermore, the wind speed probe includes a hot-wire wind speed probe and a cobra wind speed probe.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention maximizes the space utilization of the wind tunnel testing area through a six-degree-of-freedom motion platform with a sunken mechanical mechanism and a wind tunnel bottom guide design, while ensuring accurate simulation of the boundary layer wind field profile during wind tunnel testing. By deploying six force sensors, accelerometers, laser interferometers, and fiber optic strain sensors on the scaled-down model, the measured data is processed to obtain test results such as aerodynamic loads, structural internal forces, and foundation motion attitude of the scaled-down model test. Hot-wire anemometers, cobra anemometers, moving test frames, and particle image velocimetry (PIV) are used to measure the flow field changes in the wake field during the wind turbine scaled-down model test. This method solves the problems of inaccurate boundary layer wind field profile simulation, excessive model blockage ratio, and difficulty in accurately measuring the dynamic response of the model structure, such as stress conditions and foundation motion, in wind tunnel tests of large floating wind turbine scaled-down models. It enables accurate measurement of aerodynamic loads, structural internal forces, foundation motion attitude, and wake field characteristics in wind tunnel tests of large floating wind turbine scaled-down models. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of a scaled-down model of a floating wind turbine wind tunnel test in an embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram of the installation of the device and sensor in an embodiment of the present invention.

[0043] Figure 3 This invention relates to the measurement of blade normal stress under both static and dynamic conditions in this embodiment.

[0044] Figure 4This is the wind speed measurement result of the hub height at the 2D cross-section behind the impeller in this embodiment of the invention.

[0045] Figure 5 The PIV wind speed measurement results in this embodiment of the invention (the speed measurement range in the figure is 0.3D (length) × 0.3D (width) × 0.3D (height)). Detailed Implementation

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0047] A wind tunnel testing method applicable to a scaled-down model of a large floating wind turbine, the scaled-down model of the large floating wind turbine comprising a six-degree-of-freedom motion platform and a scaled-down wind turbine model, comprising the following steps:

[0048] A reserved space is set below the wind tunnel test section. The main mechanical structure of the six-degree-of-freedom motion platform is sunk and arranged in the reserved space. Only the upper platform of the six-degree-of-freedom motion platform is kept in the wind tunnel test section. The bottom of the tower of the scaled-down wind turbine model is fixedly installed on the upper platform.

[0049] A guide vane of the same height as the upper platform is installed on the bottom surface of the wind tunnel test section, so that the upper surface of the guide vane is flush with the surface of the platform on the six-degree-of-freedom motion platform; sensors are installed on the scaled-down model of the wind turbine to acquire sensor measurement data, and the inertial force component in the sensor measurement load data is corrected to obtain the aerodynamic load, structural internal force and basic motion attitude of the scaled-down model of the wind turbine.

[0050] Particle image velocimetry was used to measure the wind speed in the flow field. A wind speed probe was installed on a moving measurement frame to measure the wind speed in the 1D and 2D cross sections downwind of the model. The particle image velocimetry results were verified, and the wake field measurement results of the scaled-down model of the wind turbine were obtained.

[0051] The sunken arrangement satisfies the following constraints:

[0052] (1) The sum of the height of the scaled-down model of the wind turbine and the installation height of the platform on the six-degree-of-freedom motion platform in the wind tunnel test section is less than the maximum allowable height of the wind tunnel test section;

[0053] (2) The sum of the swept area of ​​the impeller of the scaled-down model of the wind turbine and the maximum projected area of ​​the six-degree-of-freedom motion platform in the wind tunnel test section shall not exceed 10% of the cross-sectional area of ​​the wind tunnel test section;

[0054] (3) The sum of the horizontal cross-sectional diameter of the six-degree-of-freedom motion platform at the bottom height of the wind tunnel test section and twice the maximum motion radius of the six-degree-of-freedom motion platform is less than the diameter of the reserved space;

[0055] (4) The bottom diameter of the six-degree-of-freedom motion platform is smaller than the diameter of the reserved space;

[0056] (5) The sum of the reserved space height and the installation height of the six-degree-of-freedom motion platform in the wind tunnel test section is greater than the minimum electric cylinder height of the six-degree-of-freedom platform required to meet the test motion conditions.

[0057] The installation of sensors on the scaled-down wind turbine model includes: arranging fiber optic strain sensors on the front of the blades to measure the blade strain ε during operation. blade ; Install an acceleration sensor in the engine compartment to measure wheel hub acceleration a hub A six-component force sensor is installed at the connection between the top of the tower and the nacelle to measure the six-component force load F at the top of the tower. top A six-component force sensor is installed at the connection between the bottom of the tower and the upper platform to measure the six-component force load F at the bottom of the tower. base A laser interferometer is installed on a six-degree-of-freedom motion platform to measure the displacement (basic motion) X of the platform. platform .

[0058] The aerodynamic load is calculated based on the measurement data of the six component forces at the top of the tower and the measurement data of the hub acceleration.

[0059] F aero =F top -M rotor a hub

[0060] Among them, F aero For the aerodynamic loads of the scaled-down model of the wind turbine, F top M represents the six-component force load at the top of the wind turbine model measured by the six-component force sensor at the top of the tower. rotor For the mass matrix of the blades and hub of the scaled-down model of the wind turbine, a hub Hub acceleration of a scaled-down model of a wind turbine, measured by an accelerometer.

[0061] The internal forces of the structure include the modified six-component load at the top of the tower, the six-component load at the bottom of the tower, and the blade axial force;

[0062] The revised calculation method for the six-component load at the top of the tower is as follows:

[0063]

[0064] in, For the corrected six-component load at the top of the tower, M RNA Mass matrix of blades, hub, and nacelle sections for a scaled-down model of a wind turbine. Mass matrix of prototype wind turbine blades, hub, and nacelle;

[0065] The revised calculation method for the six-component load at the base of the tower is as follows:

[0066]

[0067] in, For the corrected six-component load at the base of the tower, M turbine This is the total mass matrix of the scaled-down model of the wind turbine. The total mass matrix of the prototype wind turbine;

[0068] The method for calculating the blade axial force is as follows:

[0069] F N =E blade ε blade A blade

[0070] Among them, F N E represents the axial force of the blades in a scaled-down model of a wind turbine. blade For the elastic modulus of the blade in the scaled-down model of the wind turbine, A blade The cross-sectional area of ​​the blades in the scaled-down model of the wind turbine.

[0071] The method of measuring wind speed in a flow field using particle image velocimetry includes the following specific steps:

[0072] A tracer particle delivery device was placed behind the impeller of a scaled-down wind turbine model. During the experiment, tracer particles were delivered through the device, and a laser emitter was used to illuminate an area of ​​length 2D × width 1.5D × height 1.5D behind the scaled-down wind turbine model, where D is the diameter of the impeller of the scaled-down wind turbine model. The position changes of the tracer particles in the area were continuously captured by a high-speed camera. The captured images were then subjected to high-precision cross-correlation post-processing and artificial intelligence particle image analysis to obtain the flow field wind speed components in the velocity measurement area during the experiment.

[0073] The specific steps for measuring wind speed using a moving frame to install a wind speed probe in the downwind 1D and 2D sections of the model include:

[0074] The hot-wire anemometer and the cobra anemometer are mounted on a moving frame, which can move the anemometer to a designated position on the measurement section behind the scaled-down wind turbine model. On two sections at distances of 1D and 2D in the wind direction under the scaled-down wind turbine model, four sets of measuring points are arranged at a horizontal spacing of 0.5D and four sets of measuring points are arranged at a vertical spacing of 0.5D, for a total of 4×4=16 measuring points on each section for wind speed measurement. The wind speed component of the flow field at each measuring point is measured by moving the anemometer to verify the measurement results of the particle image velocimetry technology.

[0075] Example

[0076] like Figure 1 As shown, in a specific embodiment of the present invention, the scaled-down model of the floating wind turbine wind tunnel test consists of a six-degree-of-freedom motion platform driven by six sets of electric cylinders and a scaled-down model of the wind turbine including blades, hub, nacelle, tower and sensors.

[0077] like Figure 2The diagram shown is a schematic of the equipment and sensor installation for a wind tunnel testing method applicable to a scaled-down model of a large floating wind turbine according to the present invention.

[0078] Regarding the installation of the test model, the bottom surface of the wind tunnel test section was modified. Utilizing the reserved space below the test section, a six-degree-of-freedom motion platform mechanical mechanism was arranged in a sunken configuration. The main mechanical structure of the six-degree-of-freedom motion platform was placed below the wind duct. Only the upper platform and the wind turbine model for fixing the wind turbine model were retained within the wind tunnel test section to meet the requirements for blockage ratio and structural dimensions. The model dimensions, wind tunnel dimensions, and installation location should meet the following conditions:

[0079] 1) The total height of the model shall not exceed the wind tunnel size limit.

[0080] h turbine +h up <H

[0081] Among them, h turbine h represents the total height of the scaled-down model of the wind turbine. up H represents the height of the six-degree-of-freedom motion platform within the wind tunnel test section, where H is the maximum allowable test height within the wind tunnel test section.

[0082] 2) The model blocking ratio does not exceed the limit.

[0083]

[0084] Where A turbine A represents the swept area of ​​the impeller in a scaled-down model of a wind turbine. up A0 represents the maximum projected area of ​​the six-degree-of-freedom motion platform within the wind tunnel test section under all motion postures, and A0 represents the cross-sectional area of ​​the wind tunnel test section.

[0085] 3) The size of the six-degree-of-freedom platform shall not exceed the size limit of the reserved space below the wind tunnel test section.

[0086]

[0087] Where D up D is the horizontal cross-sectional diameter of the six-degree-of-freedom motion platform at the bottom height of the wind tunnel test section. motion D represents the maximum radius of motion for a six-degree-of-freedom motion platform across all motion postures. low D0 is the diameter of the bottom of the six-degree-of-freedom motion platform, and D0 is the diameter of the reserved space for mounting the six-degree-of-freedom motion platform.

[0088] 4) The reserved space height should meet the size restrictions of the electric cylinder of the six-degree-of-freedom motion platform.

[0089] h0+h up h actuator

[0090] Where h0 is the height of the reserved space below the wind tunnel test section, h actuator The minimum electric cylinder height for a six-degree-of-freedom motion platform required to meet the experimental motion conditions.

[0091] 5) Install at a height of h on the bottom surface of the wind tunnel test section. up The guide vanes were added to raise the bottom of the wind tunnel, ensuring that the bottom surface of the wind tunnel test section was at the same height as the platform surface of the six-degree-of-freedom motion platform during the test.

[0092] In this embodiment, the impeller diameter of the scaled-down model of the large floating wind turbine wind tunnel test, designed with a six-degree-of-freedom motion platform sinking according to the above steps, is 2.12m. In contrast, the largest impeller diameter of a wind turbine model designed using traditional methods, which place the entire model structure within the wind tunnel test section, is 1.58m. This invention effectively increases the space utilization of the wind tunnel test section and improves the scaled-down model size. Simultaneously, the bottom surface of the wind tunnel test section is at the same height as the platform surface on the six-degree-of-freedom motion platform, ensuring that the initial height of the wind field in the test boundary layer is the same as the actual working environment of the prototype wind turbine, effectively simulating the wind field of the prototype wind turbine's working environment.

[0093] Fiber optic strain sensors were placed on the front of the blades of a scaled-down wind turbine model to measure the blade strain ε during model operation. blade An acceleration sensor was installed in the model's cabin to measure the acceleration 'a' of the model's wheel hubs. hub Six-component force sensors were installed at the connection points between the top of the model tower and the nacelle, and at the connection points between the bottom of the tower and the six-degree-of-freedom motion platform, to measure the six-component force load F at the top and bottom of the tower, respectively. top F base A laser interferometric rangefinder is installed on top of a six-degree-of-freedom motion platform to measure the platform's displacement (basic motion) X. platform .

[0094] Froude similarity is not typically used for scaled-down models of large floating wind turbines in wind tunnel tests. This is because the mechanical structures of the wind turbine model, such as the motor, often cannot be arbitrarily reduced in scale. Therefore, it is necessary to correct the inertial force components in the measurement results to obtain the correct internal structural forces, aerodynamic loads, and structural interface loads.

[0095] The aerodynamic load calculation method for the scaled-down model of the wind turbine is as follows:

[0096] F aero =F top -M rotor a hub

[0097] Where F aero For the aerodynamic loads of the scaled-down model of the wind turbine, M rotor This is the mass matrix of the blades and hub of a scaled-down model of a wind turbine.

[0098] The expression for the six-component force load at the top of the wind turbine in the scaled-down model is as follows:

[0099]

[0100] in For the six-component force load at the top of the tower of the corrected scaled-down wind turbine model, M RNA Mass matrix of blades, hub, and nacelle sections for a scaled-down model of a wind turbine. The mass matrix of the prototype wind turbine blades, hub, and nacelle.

[0101] The corrected six-component load at the base of the tower can be expressed as:

[0102]

[0103] in For the six-component force load at the base of the tower in the corrected scaled-down model of the wind turbine, M turbine This is the total mass matrix of the scaled-down model of the wind turbine. The total mass matrix of the prototype wind turbine.

[0104] The method for calculating the blade axial force in a scaled-down model of a wind turbine is as follows:

[0105] F N =E blade ε blade A blade

[0106] Where F N E represents the axial force of the model blade. blade Let A be the elastic modulus of the model blade. blade This represents the cross-sectional area of ​​the blade. For example... Figure 3 It measures the normal stress of the blade under both static and dynamic conditions.

[0107] A tracer particle delivery device was placed behind the impeller of a scaled-down wind turbine model. During the test, tracer particles were released, and a laser emitter illuminated a 2D (length) × 1.5D (width) × 1.5D (height) area behind the model. A high-speed camera continuously captured the positional changes of the tracer particles in this area. The captured images underwent high-precision cross-correlation post-processing and artificial intelligence particle image analysis to obtain the wind speed components of the flow field within the measurement area during the experiment. A hot-wire anemometer and a cobra anemometer were mounted on a moving frame, which could move the anemometer to any position within the 2D (length) × 1.5D (width) × 1.5D (height) area (D is the diameter of the impeller) behind the model. At two cross-sections 1D and 2D away from the wind turbine in the downwind direction of the scaled-down model, four sets of measuring points were arranged at a horizontal spacing of 0.5D and four sets of measuring points at a vertical spacing of 0.5D, for a total of 4 × 4 = 16 measuring points per cross-section for wind speed measurement. Hot-wire anemometers and cobra anemometers were used to measure the wind speed components of the flow field at each measuring point to verify the PIV measurement results.

[0108] Figure 4 The result is the wind speed measurement at the hub height of the 2D cross-section behind the impeller. Figure 5 The results show the PIV wind speed measurement (the measurement range in the figure is 0.3D (length) × 0.3D (width) × 0.3D (height)). The measurement results demonstrate that, compared to the multi-point measurement method using an anemometer and moving measuring frame used in previous similar domestic and international experiments, the PIV measurement method used in this invention can achieve efficient and synchronous measurement of the flow field behind the impeller of the wind turbine model, effectively capturing the instantaneous turbulent characteristics of the wind turbine model's wake field during the experiment.

[0109] Of course, the above are just specific application examples of the present invention. The present invention has other implementation methods. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A wind tunnel testing method applicable to a scaled-down model of a large floating wind turbine, wherein the scaled-down model of the large floating wind turbine includes a six-degree-of-freedom motion platform and a scaled-down model of the wind turbine, characterized in that, Includes the following steps: A reserved space is set below the wind tunnel test section. The main mechanical structure of the six-degree-of-freedom motion platform is sunk and arranged in the reserved space. Only the upper platform of the six-degree-of-freedom motion platform is kept in the wind tunnel test section. The bottom of the tower of the scaled-down wind turbine model is fixedly installed on the upper platform. A guide vane of the same height as the upper platform is installed on the bottom surface of the wind tunnel test section, so that the upper surface of the guide vane is flush with the surface of the platform on the six-degree-of-freedom motion platform; sensors are installed on the scaled-down model of the wind turbine to acquire sensor measurement data, and the inertial force component in the load data measured by the sensors is corrected to obtain the aerodynamic load, structural internal force and basic motion attitude of the scaled-down model of the wind turbine. Particle image velocimetry was used to measure the wind speed in the flow field. A wind speed probe was installed on a moving measurement frame to measure the wind speed in the 1D and 2D sections downwind of the model. The particle image velocimetry results were verified, and the wake field measurement results of the scaled-down wind turbine model were obtained, where D is the impeller diameter of the scaled-down wind turbine model. The aerodynamic load is calculated based on the measurement data of the six component forces at the top of the tower and the measurement data of the hub acceleration. ， in, The aerodynamic loads for a scaled-down model of a wind turbine. The six-component force load at the top of the wind turbine is measured by a six-component force sensor on a scaled-down model of the wind turbine. The mass matrix of the blades and hub of the scaled-down model of the wind turbine. Hub acceleration of a scaled-down model of a wind turbine, measured by an accelerometer. The internal forces of the structure include the modified six-component load at the top of the tower, the six-component load at the bottom of the tower, and the blade axial force; The revised calculation method for the six-component load at the top of the tower is as follows: ， in, The corrected six-component load at the top of the tower. Mass matrix of blades, hub, and nacelle sections for a scaled-down model of a wind turbine. Mass matrix of prototype wind turbine blades, hub, and nacelle; The revised calculation method for the six-component load at the base of the tower is as follows: ， in, The corrected six-component load at the base of the tower. The six-component force load at the bottom of the tower is measured by a six-component force sensor. This is the total mass matrix of the scaled-down model of the wind turbine. The total mass matrix of the prototype wind turbine; The method for calculating the blade axial force is as follows: ， in, The axial force of the blades in the scaled-down model of the wind turbine. The elastic modulus of the blade in the scaled-down model of the wind turbine. Strain of the blade in a scaled-down model of a wind turbine. The cross-sectional area of ​​the blades in the scaled-down model of the wind turbine.

2. The wind tunnel testing method for a scaled-down model of a large floating wind turbine according to claim 1, characterized in that, The sunken arrangement satisfies the following constraints: (1) The sum of the height of the scaled-down model of the wind turbine and the installation height of the platform on the six-degree-of-freedom motion platform in the wind tunnel test section is less than the maximum allowable height of the wind tunnel test section; (2) The sum of the swept area of ​​the impeller of the scaled-down wind turbine model and the maximum projected area of ​​the six-degree-of-freedom motion platform in the wind tunnel test section shall not exceed 10% of the cross-sectional area of ​​the wind tunnel test section; (3) The sum of the horizontal cross-sectional diameter of the six-degree-of-freedom motion platform at the bottom height of the wind tunnel test section and twice the maximum motion radius of the six-degree-of-freedom motion platform is less than the diameter of the reserved space; (4) The bottom diameter of the six-degree-of-freedom motion platform is smaller than the diameter of the reserved space; (5) The sum of the reserved space height and the installation height of the six-degree-of-freedom motion platform in the wind tunnel test section is greater than the minimum electric cylinder height of the six-degree-of-freedom platform required to meet the test motion conditions.

3. The wind tunnel testing method for a scaled-down model of a large floating wind turbine according to claim 1, characterized in that, The installation of sensors on the scaled-down model of the wind turbine includes: arranging fiber optic strain sensors on the front of the blades to measure blade strain during operation; installing accelerometers on the nacelle to measure hub acceleration; installing six-component force sensors at the connection between the top of the tower and the nacelle to measure the six-component force load at the top of the tower; installing six-component force sensors at the connection between the bottom of the tower and the upper platform to measure the six-component force load at the bottom of the tower; and installing a laser interferometer on the upper platform of the six-degree-of-freedom motion platform to measure the displacement of the upper platform.

4. The wind tunnel testing method for a scaled-down model of a large floating wind turbine according to claim 1, characterized in that, The method of measuring wind speed in a flow field using particle image velocimetry includes the following specific steps: A tracer particle delivery device was placed behind the impeller of a scaled-down wind turbine model. During the experiment, tracer particles were delivered through the device, and a laser emitter was used to illuminate an area of ​​length 2D × width 1.5D × height 1.5D behind the scaled-down wind turbine model, where D is the diameter of the impeller of the scaled-down wind turbine model. The position changes of the tracer particles in the area were continuously captured by a high-speed camera. The captured images were then subjected to high-precision cross-correlation post-processing and artificial intelligence particle image analysis to obtain the flow field wind speed components in the velocity measurement area during the experiment.

5. The wind tunnel testing method for a scaled-down model of a large floating wind turbine according to claim 1, characterized in that, The specific steps for measuring wind speed using a moving frame to install a wind speed probe in the downwind 1D and 2D sections of the model include: An anemometer is mounted on a moving frame that can move the anemometer to a designated position on the measurement section behind the scaled-down wind turbine model. Several measuring points are arranged on two sections at distances of 1D and 2D in the wind direction under the scaled-down wind turbine model. The wind speed component of the flow field at each measuring point is measured by moving the anemometer to verify the measurement results of the particle image velocimetry technology.

6. The wind tunnel testing method for a scaled-down model of a large floating wind turbine according to claim 5, characterized in that, The method for arranging the measuring points is as follows: 4 sets of measuring points are arranged with a horizontal spacing of 0.5D and 4 sets of measuring points are arranged with a vertical spacing of 0.5D, for a total of 4×4=16 measuring points arranged in each cross section for wind speed measurement.

7. The wind tunnel testing method for a scaled-down model of a large floating wind turbine according to claim 6, characterized in that, The wind speed probes include hot-wire wind speed probes and cobra wind speed probes.

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