A method for measuring the aerodynamic forces of zero-stiffness supports based on pulse-type wind tunnels

Abstract

This invention relates to the field of wind tunnel testing technology, and more particularly to a method for measuring aerodynamic forces under zero-stiffness support in a pulsed wind tunnel. The method includes: acquiring wind tunnel flow field parameters and model entity parameters; estimating the magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field through finite element simulation; calculating the range of attitude angle changes of the model in the wind tunnel flow field based on the magnitude of the aerodynamic forces acting on the model, the model entity parameters, and the effective action time of the wind tunnel flow field; determining whether the range of attitude angle changes of the model in the wind tunnel flow field does not exceed a preset angle change threshold, and if so, continuing; determining the combined parameters of the accelerometers embedded in the model; placing the model in the wind tunnel flow field with zero-stiffness support and acquiring the measurement results of all accelerometers within the effective action time; and calculating the actual aerodynamic forces acting on the model in the wind tunnel flow field based on the acquired measurement results of all accelerometers. This invention can improve the frequency response and data reliability of aerodynamic load measurements.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing technology, and in particular to a method for measuring aerodynamic forces of zero-stiffness support based on a pulse-type wind tunnel. Background Technology

[0002] Pulse-type wind tunnels, such as shock tunnels and expander tube wind tunnels, are important equipment for conducting ground tests of hypersonic vehicle flight environments. Aerodynamic measurement tests of hypersonic vehicles typically involve installing a vehicle model in a pulse-type wind tunnel, where a flow field that meets the simulation conditions is generated and applied to the model, thereby measuring the aerodynamic loads on the model.

[0003] For conventional models, the currently used aerodynamic measurement technology is mainly the tail-support internal balance aerodynamic measurement technology, which is a static force measurement technology in principle. Due to the limitations of its operating principle, the effective action time of a pulse wind tunnel is generally only a few hundred microseconds to tens of milliseconds. The entire process is a dynamic test process, and vibration interference is prominent. The tail-support internal balance aerodynamic measurement test device is a cantilever beam in configuration, resulting in a low frequency response and making it difficult to accurately measure aerodynamic signals over a short period of time. Summary of the Invention

[0004] The purpose of this invention is to address at least some of the above-mentioned shortcomings by providing a zero-stiffness support aerodynamic measurement method based on a pulse-type wind tunnel, so as to improve the measurement frequency response and data reliability.

[0005] To achieve the above objectives, the present invention provides a method for measuring the aerodynamic forces of a zero-stiffness support based on a pulse-type wind tunnel, comprising:

[0006] The wind tunnel flow field parameters and the model entity parameters of the model to be measured are obtained. The model is embedded with an accelerometer assembly and an offline data acquisition device. The accelerometer assembly includes multiple accelerometers, and the offline data acquisition device is connected to each of the accelerometers to collect and store the measurement results of the accelerometers.

[0007] Based on the wind tunnel flow field parameters and the model entity parameters, the magnitude of the aerodynamic force on the model in the wind tunnel flow field is estimated through finite element simulation.

[0008] Based on the estimated magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field, the model entity parameters, and the effective duration of the wind tunnel flow field, the range of attitude angle changes of the model in the wind tunnel flow field is calculated.

[0009] Determine whether the range of attitude angle change of the model in the wind tunnel flow field does not exceed the preset angle change threshold; if yes, continue.

[0010] Determine the accelerometer combination parameters embedded in the model; the accelerometer combination parameters include the final measurement parameters, installation position, measurement range and measurement accuracy of each accelerometer respectively;

[0011] The model was placed in the wind tunnel flow field with zero stiffness support, and the measurement results of all the accelerometers were obtained within the effective time.

[0012] Based on the acquired measurement results of all the accelerometers and the combined parameters of the accelerometers, the actual aerodynamic forces experienced by the model in the wind tunnel flow field are calculated.

[0013] Optionally, if the final measured parameters include one or more of axial force, normal force, lateral force, pitching moment, yaw moment, and roll moment, placing the model in the wind tunnel flow field with zero stiffness support includes:

[0014] The model is placed above the uniform flow field region of the wind tunnel in a preset posture;

[0015] The pure release allows the model to enter the uniform flow field region of the wind tunnel in the form of free fall, so that it is in the wind tunnel flow field with zero stiffness support during the effective time.

[0016] Optionally, if the final measured parameters include one or more of axial force, normal force, lateral force, pitching moment, yaw moment, and roll moment, placing the model in the wind tunnel flow field with zero stiffness support includes:

[0017] The model is placed in a uniform flow field region of the wind tunnel in a preset posture by means of suspension or lifting.

[0018] Remove the suspension or support structure, allowing the model to be placed in the wind tunnel flow field with zero stiffness support during the effective operating time.

[0019] Optionally, after determining that the attitude angle change range of the model in the wind tunnel flow field does not exceed a preset angle change threshold, and before placing the model in the wind tunnel flow field in the form of zero-stiffness support, the method further includes:

[0020] Estimate the landing area of ​​the model;

[0021] Based on the landing area of ​​the model, the installation location of the recycling device is determined, and the recycling device is installed.

[0022] Optionally, if the final measured parameters include one or more of axial force, lateral force, yaw moment, and roll moment, placing the model in the wind tunnel flow field with zero stiffness support includes:

[0023] The model is suspended by a vertical line and placed in a predetermined posture within the uniform flow field of the wind tunnel, so that the model is in the wind tunnel flow field with zero stiffness support in the axial, lateral, yaw and roll directions during the effective time.

[0024] Optionally, placing the model in a pre-defined orientation within a uniform flow field region of the wind tunnel by suspending it vertically includes:

[0025] The model is horizontally suspended using a suspension device. The suspension device includes a frame and two vertical lines. When suspending the model horizontally, the axial directions of both the frame and the model are adjusted to be horizontal. One vertical line is connected from the frame perpendicular to the axial direction of the model to the head of the model at the position with the least interference to the flow field. The other vertical line is connected from the frame perpendicular to the axial direction of the model to the tail end face of the model. The two vertical lines are parallel and spaced apart, and the upper and lower suspension points are both in the plane formed by the axis of the model and the direction of gravity.

[0026] By changing the posture of the frame, the posture of the model is adjusted to a preset posture.

[0027] Optionally, if the final measured parameters only include axial force, placing the model in the wind tunnel flow field with zero stiffness support includes:

[0028] The model is horizontally suspended using a suspension device. The suspension device includes a frame and two sets of suspension lines. Each set of suspension lines includes at least two oblique suspension lines. When suspending the model horizontally, the axial directions of both the frame and the model are adjusted to be horizontal. One set of suspension lines connects from the frame perpendicular to the axial direction of the model to the head of the model at the position with the least interference to the flow field. The other set of suspension lines connects from the frame perpendicular to the axial direction of the model to the tail end face of the model. The two sets of suspension lines are parallel and spaced apart. The two oblique suspension lines in each set are symmetrical with respect to the plane formed by the axial direction of the model and the direction of gravity. The bottom suspension points of the two oblique suspension lines are connected at the same point or the distance between the top suspension points is greater than the distance between the bottom suspension points.

[0029] By changing the attitude of the frame, the attitude of the model is adjusted to a preset attitude, so that the model is in the wind tunnel flow field with zero stiffness support in the axial direction during the effective time.

[0030] Optionally, the model to be measured is created in the following manner:

[0031] Obtain wind tunnel flow field parameters and the geometry and dimensions of the model to be fabricated;

[0032] Based on the wind tunnel flow field parameters and the geometry and dimensions of the model, the magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field and the region where the pressure core is located are estimated through finite element simulation.

[0033] Based on the estimated magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field, as well as the preset angle change threshold and effective action time, the combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass is determined. The combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass includes multiple combinations of moment of inertia and distance from the center of pressure to the center of mass data where the attitude change does not exceed the angle change threshold within the effective action time.

[0034] Based on the combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass, the combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass is determined by the relationship between the moment of inertia and the mass. The combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass includes multiple combinations of mass, moment of inertia, and distance from the center of pressure to the center of mass data where the attitude change does not exceed the angle change threshold within the effective action time.

[0035] Using a multi-objective optimization method, within the combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass, the data values ​​of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass are selected.

[0036] Based on the estimated region of the model's center of gravity and the selected model's mass, moment of inertia, and distance from the center of gravity to the center of mass, the model's mass distribution is determined.

[0037] Based on the aforementioned geometry and dimensions, a model shell is fabricated;

[0038] Based on the determined mass distribution of the model, corresponding counterweights are set inside the manufactured model shell to obtain the model entity;

[0039] Based on the final measurement parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters, the accelerometer combination is determined. Determining the accelerometer combination includes determining the number of accelerometers, the final measurement parameters corresponding to each accelerometer, the expected installation position, the measurement range, and the measurement accuracy. The final measurement parameters include one or more of the following: axial force, normal force, lateral force, pitching moment, yaw moment, and roll moment.

[0040] Based on the determined accelerometer combination, the accelerometer combination and offline data acquisition device are embedded in the model entity to finally obtain the model for the experiment; the offline data acquisition device is connected to each of the accelerometers to collect and store the measurement results of the accelerometers.

[0041] Optionally, determining the accelerometer assembly based on the final measured parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters includes:

[0042] If the final measured parameters include pitching moment, then two identical single-axis accelerometers are set up on the front and rear sides or the top and bottom sides of the center of mass of the model. The two single-axis accelerometers set up on the front and rear sides of the center of mass measure the upward or downward acceleration, and the two single-axis accelerometers set up on the top and bottom sides of the center of mass measure the acceleration of the model along the axial direction and along the axial direction in the opposite direction, respectively.

[0043] If the final measured parameters include yaw moment, then two identical single-axis accelerometers are respectively set up on the left and right sides or front and rear sides of the center of mass of the model. The two single-axis accelerometers set up on the left and right sides of the center of mass measure the acceleration of the model along the axial direction, and the two single-axis accelerometers set up on the front and rear sides of the center of mass measure the acceleration of the model to the left or right.

[0044] If the final measured parameter includes rolling torque, then two identical single-axis accelerometers are respectively placed on the left and right sides or the top and bottom sides of the center of mass of the model. The two single-axis accelerometers placed on the left and right sides of the center of mass measure the upward or downward acceleration of the model, and the two single-axis accelerometers placed on the top and bottom sides of the center of mass measure the leftward and rightward acceleration of the model, respectively.

[0045] If the final measured parameters include axial force, then the axial acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the left and right sides or the top and bottom sides of the model's center of mass.

[0046] If the final measured parameters include the normal force, the normal acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the front and rear sides of the model's center of mass.

[0047] If the final measured parameters include lateral force, the lateral acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the upper and lower sides or the front and rear sides of the model's center of mass.

[0048] Optionally, determining the accelerometer assembly based on the final measurement parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters further includes:

[0049] Based on the final measured parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters, the expected installation positions of each accelerometer are determined.

[0050] Based on the expected installation location of each accelerometer and the estimated magnitude of the aerodynamic force on the model in the wind tunnel flow field, the numerical range of the measurement results of each accelerometer is determined respectively.

[0051] Based on the numerical range of the accelerometer measurement results, determine the accelerometer's measurement range and accuracy.

[0052] The above-mentioned technical solution of the present invention has the following advantages: The present invention provides a zero-stiffness support aerodynamic force measurement method based on pulse-type wind tunnel. For a model that will not undergo significant attitude changes in the wind tunnel flow field within the effective time and thus cause changes in aerodynamic load, it is placed in the wind tunnel flow field in the form of zero-stiffness support. The accelerometer combination set inside the model and the offline data acquisition device are used to measure and record the data, and then the actual aerodynamic force on the model in the wind tunnel flow field is calculated. The present invention can effectively improve the frequency response of aerodynamic force measurement in wind tunnel tests, from about 20Hz in the tail support internal balance aerodynamic force measurement technology to more than 1000Hz. At the same time, the measurement device used in the present invention has a more compact structure and higher stiffness, which can reduce the interference of difficult-to-handle low-frequency interference on the model aerodynamic force measurement signal, improve the data reliability, and thus more accurately measure the instantaneous aerodynamic force signal on the order of milliseconds. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the steps of a zero-stiffness support aerodynamic measurement method based on a pulse-type wind tunnel in an embodiment of the present invention;

[0054] Figure 2 This is a schematic diagram of a zero-stiffness support state in an embodiment of the present invention;

[0055] Figure 3 This is a schematic diagram showing the positional relationship and sensitivity direction of each accelerometer relative to the center of mass of the model in an accelerometer assembly according to an embodiment of the present invention;

[0056] Figure 4 This is a schematic diagram illustrating the principle of using two accelerometers to calculate linear and rotational acceleration.

[0057] In the diagram: 1: Wind tunnel nozzle; 2: Delivery device; 3: Wind tunnel test chamber; 4: Recovery device; 5: Model. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] As mentioned earlier, the currently used aerodynamic measurement technology mainly employs the tail-support internal balance aerodynamic measurement technology. During measurement, a strain balance is built into the model, and the tail of the model is supported in the wind tunnel. The aerodynamic forces applied to the model are measured by the strain balance. In principle, the tail-support internal balance aerodynamic measurement technology is a static force measurement technique. Due to limitations in its operating principle, the effective operating time (or effective test time) of a pulse-type wind tunnel is generally only a few hundred microseconds to tens of milliseconds. The entire process is a dynamic testing process, where vibration interference is significant. Because the tail-support internal balance aerodynamic measurement experimental device is a cantilever beam in configuration, its axial force has a high natural vibration frequency, resulting in a high frequency response, reaching up to 1kHz or more. This allows it to accurately reproduce aerodynamic signals with a duration of less than 1ms. However, due to the influence of the model's mass and the length-to-diameter ratio of the support rods, the natural frequencies of the model's normal force and pitching moment are difficult to exceed 100Hz, resulting in a frequency response often only in the tens of hertz. This limits its ability to reproduce aerodynamic signals with a duration of more than 100ms, and for shorter aerodynamic signals, strong vibration interference occurs. Therefore, this invention provides a zero-stiffness support aerodynamic measurement method suitable for pulse-type wind tunnels to reduce the impact of vibration interference on the model's aerodynamic measurement results.

[0060] The specific implementation of the above concept is described below.

[0061] like Figure 1 As shown, an embodiment of the present invention provides a method for measuring the aerodynamic forces of a zero-stiffness support based on a pulse-type wind tunnel (hereinafter referred to as the method of the present invention), comprising:

[0062] Step 100: Obtain the wind tunnel flow field parameters and the model entity parameters of the model to be measured;

[0063] The model to be measured is embedded with an accelerometer assembly and an offline data acquisition device. The accelerometer assembly includes multiple accelerometers, and the offline data acquisition device is connected to each of the accelerometers to collect and store the measurement results of the accelerometers.

[0064] The model entity parameters include the model's geometry, dimensions, mass, center of mass position, and moment of inertia; under zero stiffness support, the model rotates under aerodynamic forces, with a moment of inertia J = mr. 2 m represents the mass of the model, and r represents the distance from the center of pressure to the center of mass of the model; in addition, the stiffness of the model should also be large to ensure that the rigid body effect is greater than the flexible body effect in the flow field.

[0065] Step 102: Based on the wind tunnel flow field parameters and the model entity parameters, estimate the magnitude of the aerodynamic force on the model in the wind tunnel flow field through finite element simulation;

[0066] This step 102 only requires estimation and does not require precise solution, which can save time and reduce the amount of calculation.

[0067] Step 104: Based on the estimated magnitude of the aerodynamic force on the model in the wind tunnel flow field, the model entity parameters, and the effective action time of the wind tunnel flow field, calculate the range of attitude angle changes of the model in the wind tunnel flow field within the effective action time.

[0068] This step 104 does not actually require an exact solution; it is sufficient to estimate the possible range of changes in the model.

[0069] Step 106: Determine whether the range of attitude angle change of the model in the wind tunnel flow field does not exceed the preset angle change threshold; if yes, continue.

[0070] To achieve accurate measurement, the preset angle change threshold is preferably no more than 3′ for pitch, yaw, and roll.

[0071] In step 106, if the range of attitude angle changes of the model in the wind tunnel flow field exceeds the preset angle change threshold, that is, the possible change in any angle of pitch, yaw or roll exceeds the preset angle change threshold, it indicates that the model is not applicable to the method of the present invention. In order to make the model applicable to the method of the present invention, the model to be measured can be adjusted, such as increasing the mass and / or moment of inertia of the model, so as to reduce the attitude changes that the model may undergo in the wind tunnel flow field.

[0072] Step 108: Determine the combined parameters of the accelerometers embedded in the model;

[0073] The accelerometer combination parameters include the final measurement parameters, installation position, measurement range, and measurement accuracy corresponding to each accelerometer; the final measurement parameters may be one or more.

[0074] Step 110: Place the model in the wind tunnel flow field with zero stiffness support, and obtain the measurement results of all the accelerometers within the effective time.

[0075] Step 112: Based on the measurement results of all the accelerometers and the combined parameters of the accelerometers, calculate the actual aerodynamic force on the model in the wind tunnel flow field, that is, calculate the measured signal and obtain the final measurement parameters to be determined.

[0076] To address the vibration interference caused by the tail support structure, a free-flight force measurement technique suitable for lightweight models is available. This technique involves launching the model into the flow field in a certain attitude, allowing it to fly freely, and simultaneously using a high-speed camera to record the model's motion history. Based on the images captured by the camera, the model's motion characteristic parameters are obtained, and then the aerodynamic characteristics of the model are inverted. This technique is generally used in applications such as interstage separation trajectory prediction and dynamic derivative measurement. When this free-flight force measurement technique is applied to conventional aerodynamic measurements of models, the following problems arise: 1. Relying on image-based measurements, it is limited by the spatiotemporal measurement accuracy of high-speed cameras. Lightweight models are required to increase displacement and obtain sufficiently accurate model acceleration information, placing high demands on both the model and the high-speed camera. 2. To ensure controllable attitude changes during model motion, the model's center of mass and center of pressure must coincide. However, the center of pressure is actually the object to be measured, making this condition difficult to achieve and unsuitable for non-standard models with separated centers of mass and pressure. 3. The requirement for lightweight models often contradicts the requirement for similar inertia of separated components, limiting the method. 4. The requirement for lightweight models often restricts model size; smaller models result in poorer detail simulation, contradicting the requirement for models to accurately reproduce the shape of a real aircraft. Therefore, it is impossible to achieve a high degree of model detail simulation, and only simple shape tests can be conducted; 5. The model's aerodynamic forces and attitude are closely related. As a lightweight model, its attitude is easily affected by disturbances, resulting in low robustness and difficulty in achieving steady aerodynamic force measurements. Furthermore, the lightweight nature of the model necessitates its deployment into the flow field at a predetermined attitude, making it highly susceptible to disturbances during the flow field establishment process; 6. Lightweight models often have large accelerations and displacements, making recovery difficult. Generally, models are considered disposable consumables, leading to high testing costs; In addition, the model's displacement in the flow field is related to the duration and magnitude of the applied force, and it typically does not move at a constant speed. Under these circumstances, determining the model's motion characteristics based on displacement is often inaccurate and subjective, often introducing the influence of human judgment. Thus, existing free-flight force measurement technology not only has high requirements for the supporting measurement equipment and models, but is also unsuitable for large, heavy, or non-standard models, severely limiting its practical application in aircraft ground testing.

[0077] This invention addresses the problems in measuring the aerodynamic forces of lightweight free-flight models and proposes a better solution. The zero-stiffness-supported aerodynamic force measurement method provided by this invention can be applied to models with large mass and large inertia. These models exhibit small displacement and acceleration within a millisecond-level effective timeframe, making them easy to recover. The attitude changes of large-inertia models during testing are negligible, facilitating accurate measurement of aerodynamic forces at specific attitudes. Furthermore, large-inertia models support large-scale model testing, allowing for more realistic simulation of model details. In wind tunnel flow fields, the magnitude of aerodynamic forces on the model changes with attitude. This invention aims to measure aerodynamic forces using zero-stiffness support. Considering the higher degrees of freedom without support structures, significant attitude changes within the effective timeframe could lead to distorted measurement results. Therefore, this invention acquires wind tunnel flow field parameters and the model entity parameters of the model under test, estimates potential attitude angle changes during wind tunnel testing, and compares these estimates with a preset angle change threshold. This determines whether the current model is suitable for aerodynamic force measurement using the zero-stiffness-supported method provided by this invention, resulting in more accurate and reliable measurement results. This invention employs an accelerometer assembly embedded within the model under test and an offline data acquisition device. The actual values ​​of the final measured parameters are calculated from the measurement results of the accelerometer assembly, obtaining the corresponding measurement results without requiring significant model displacement. This invention overcomes the frequency response limitations of cantilever beam configurations, effectively improving the measurement frequency response. Compared to the existing tail-support internal balance aerodynamic measurement technology with a frequency response of around 20Hz, the frequency response of this invention can be improved to over 1000Hz. Simultaneously, the measurement device (or system) has a more compact structure and higher rigidity, reducing interference from difficult-to-handle low-frequency interference on the model's aerodynamic measurement signals, improving data reliability, and thus more accurately measuring instantaneous aerodynamic signals on the millisecond scale.

[0078] Let the mass of the model be m, and let the direction of the model's axis from beginning to end be the positive x-axis (i.e., the axial direction). Establish a right-handed Cartesian coordinate system. In this case, the normal force is the force along the y-axis, and the lateral force is the force along the z-axis. The three-dimensional moments of inertia of the model are expressed as I. x I y I z The three-dimensional motion accelerations of the rigid body in the model are expressed as a. x a y a z The angular accelerations of the three-dimensional motion are expressed as α. x α y α z The measurement principle of the method of the present invention is as follows:

[0079] F x =a x m

[0080] Fy =a y m

[0081] F z =a z m

[0082] M x =I x α x

[0083] M y =I y α y

[0084] M z =I z α z

[0085] Among them, F x F y F z M represents axial force, normal force, and lateral force, respectively. x M y M z These represent the rolling moment, yaw moment, and pitch moment, respectively. By measuring and calculating the corresponding acceleration or angular acceleration, the final measurement parameters can be determined.

[0086] Unlike existing free-flight force measurement techniques, this invention is applicable to heavy models with large inertia. The greater the model's moment of inertia and mass, the stronger its attitude interference resistance. Since the model's center of rotation is the center of mass in its free state, the output sensitivity of the torque component can be controlled by adjusting the distance between the center of pressure and the center of mass.

[0087] Meanwhile, due to the model's large mass, its three-dimensional displacement within the effective time of the wind tunnel flow field can be expressed as:

[0088] s x =a x t 2 / 2

[0089]

[0090] s z =a z t 2 / 2

[0091] Because the effective operating time of a pulsed wind tunnel is very short, the actual displacement of the model within the wind tunnel flow field is very small, and can be approximated as the model's spatial displacement remaining constant within the wind tunnel test chamber. Preferably, the model mass used in the method of this invention can be determined based on the magnitude of the aerodynamic load, and the model displacement is limited to the millimeter level within the effective operating time.

[0092] The method of this invention replaces the cantilever beam configuration commonly used in tail-support internal balance aerodynamic measurement with a zero-stiffness support, making the entire force measurement system more compact and stiffer, thereby significantly increasing the natural vibration frequency and the upper limit of the frequency response. Verification has shown that the method of this invention can raise the upper limit of the frequency response of the force measurement system to over 1 kHz.

[0093] Optionally, if the final measured parameters include one or more of axial force, normal force, lateral force, pitching moment, yaw moment, and rolling moment, step 110, "placing the model in the wind tunnel flow field with zero stiffness support," may further include:

[0094] The model is placed above the uniform flow field region of the wind tunnel in a preset posture;

[0095] The model is released cleanly, allowing it to enter the uniform flow field region of the wind tunnel in a free-fall manner, thus remaining in the wind tunnel flow field with zero stiffness support for the effective time.

[0096] The above embodiments employ a pure release method, allowing the model to exist within the uniform flow field region of the wind tunnel with zero stiffness support during the effective duration. Pure release means release without initial velocity or acceleration. Since this invention is suitable for heavy models with large moments of inertia, the model falls freely through the wind tunnel, resulting in minimal changes in model attitude, low velocity, and small axial displacement. Compared to the wind tunnel flow field's speed of several kilometers per second, it can be considered equivalent to a stationary state, and the aerodynamic loads experienced within the uniform flow field region can be considered constant. The advantage of pure release is fewer interference factors with the flow field, but it places high demands on release control and the timing of coordination with the wind tunnel flow field.

[0097] In other embodiments, if the final measured parameters include one or more of axial force, normal force, lateral force, pitching moment, yaw moment, and rolling moment, step 110, "placing the model in the wind tunnel flow field with zero stiffness support," may include:

[0098] The model is placed in a uniform flow field region of the wind tunnel in a preset posture by means of suspension or lifting.

[0099] Remove the suspension or support structure, allowing the model to be placed in the wind tunnel flow field with zero stiffness support during the effective operating time.

[0100] The above embodiments employ a suspension release or lifting removal method, allowing the model, pre-placed within the wind tunnel test chamber, to achieve zero-stiffness support. For example, suspension release can be achieved by cutting the suspension wire or disconnecting it using methods such as electrical fuses or electrical release wires. After suspension release or lifting removal, the model falls freely within the wind tunnel at a predetermined attitude. Since the model's displacement along the direction of gravity and axial direction is very small in the initial stage of descent, it can be approximately achieved that the model is suspended in the flow field. The aerodynamic load on the model in the uniform flow field region of the wind tunnel can be considered constant. The advantage of releasing the suspension or lifting is that it is easier to position the model in the ideal position within the uniform flow field region of the wind tunnel within the effective action time window, but the control requirements for suspension release or lifting removal are relatively high.

[0101] Furthermore, if it is determined that the model is placed in the wind tunnel flow field with zero stiffness support in step 110 using the above-mentioned pure release, suspension release, or lifting removal method, in order to improve model utilization and test safety, it is preferable to set up a recovery device below the wind tunnel flow field to recover the model. In some embodiments, after determining in step 106 that the attitude angle change range of the model in the wind tunnel flow field does not exceed a preset angle change threshold, and before placing the model in the wind tunnel flow field with zero stiffness support in step 110, the method of the present invention further includes:

[0102] Estimate the landing area of ​​the model;

[0103] Based on the landing area of ​​the model, the installation location of the recycling device is determined, and the recycling device is installed.

[0104] The above embodiments enable the model to be recovered after measurement, allowing for model reuse, saving experimental costs, and protecting the wind tunnel system by preventing damage to the inner wall of the wind tunnel test chamber from the heavy model falling. The recovery device can be a recovery net, a recovery unit, etc.

[0105] like Figure 2 As shown, in a specific embodiment, to implement the method of the present invention, the force measurement system may include a wind tunnel nozzle 1, a release device 2, a wind tunnel test chamber 3, a recovery device 4, and a model 5. The release device 2, located at the top of the wind tunnel test chamber 3, is used to release the model 5 in a preset posture. The model 5 falls freely while being acted upon by the wind tunnel flow field. The accelerometer embedded in the model 5 measures the data. After the measurement is completed, the model 5 leaves the wind tunnel flow field area and falls into the recovery device 4 located at the bottom of the wind tunnel test chamber 3. The recovery device 4 can protect the model 5 and the data collected and stored inside it, so as to calculate the actual aerodynamic force on the model in the wind tunnel flow field based on the measurement results of all the accelerometers and the combined parameters of the accelerometers.

[0106] In other embodiments, if the final measured parameters include one or more of axial force, lateral force, yaw moment, and roll moment, step 110, "placing the model in the wind tunnel flow field with zero stiffness support," may include:

[0107] The model is suspended by a vertical line and placed in a predetermined posture within the uniform flow field of the wind tunnel, so that the model is in the wind tunnel flow field with zero stiffness support in the axial, lateral, yaw and roll directions during the effective time.

[0108] The above embodiment suspends the model in the wind tunnel flow field using a vertical suspension method, eliminating the need for release and simplifying the implementation. Referring to pendulum motion, due to the model's large inertia, its displacement is only on the order of millimeters within the effective timeframe of milliseconds. This displacement is negligible compared to the meter-scale suspension, and the influence of the suspension tension on the model's drag can be ignored. In other words, within the effective timeframe, the model can be approximated as being in free motion in the drag direction. For ultra-heavy and ultra-large models like engine models, which exhibit scale effects and require 1:1 simulation testing, free fall is less safe. Suspension is a more ideal zero-stiffness support method for conducting thrust characteristic tests on ultra-heavy and ultra-large models in wind tunnels. It also breaks the cantilever beam configuration, thereby significantly increasing the upper limit of the test system's frequency response.

[0109] Preferably, placing the model in a predetermined posture within a uniform flow field region of the wind tunnel by suspending it vertically further includes:

[0110] The model is horizontally suspended using a suspension device. The suspension device includes a frame and two vertical lines. When suspending the model horizontally, the axial directions of both the frame and the model are adjusted to be horizontal. The model can be fixed using a temporary support structure. One vertical line is connected from the frame perpendicularly to the axial direction of the model to the head of the model at the position with the least interference to the flow field, generally the front of the straight section of the model or the front end of the conical surface, avoiding positions with drastic changes in cross-sectional area as much as possible. The other vertical line is connected from the frame perpendicularly to the axial direction of the model to the tail end face of the model. The two vertical lines are parallel and spaced apart, and the upper and lower suspension points are both in the plane formed by the axis of the model and the direction of gravity.

[0111] By changing the posture of the frame, the posture of the model is adjusted to a preset posture.

[0112] The above embodiment uses a frame and vertical lines to suspend the model. When viewed from the side, the line connecting the top suspension points of the two vertical lines (i.e., the position where it connects to the frame at the top), the bottom suspension point (i.e., the position where it connects to the model at the bottom), and the two vertical lines approximately form a rectangle. The lengths of the two vertical lines are approximately equal. When moving along the axis, the rectangle becomes a parallelogram, and the model approximates a simple pendulum motion with almost no change in posture. This reduces the impact of suspension on the force on the model and ensures that the force on the model remains basically unchanged within the effective time.

[0113] Optionally, for vertical suspension, if it is also necessary to measure the normal force or pitching moment, then step 110, "placing the model in the wind tunnel flow field with zero stiffness support," may include:

[0114] The model is placed in a uniform wind tunnel flow field region by suspending it vertically in a preset posture, so that the model is in the wind tunnel flow field with zero stiffness support during the effective time.

[0115] The model was removed after the wind tunnel flow field was shut down.

[0116] After the model is rolled 90° relative to its original posture (i.e., rotated 90° around its own axis), it is then placed in the uniform flow field of the wind tunnel by means of suspension, so that the model is in the wind tunnel flow field in the form of zero stiffness support during the new round of effective action time.

[0117] The above embodiment rotates the model by 90°, converting the original normal force and pitching moment into lateral force and yaw moment, achieving a zero-stiffness support state for the original normal force and pitching moment. Then, a wind tunnel test is repeated to obtain measurement results within a new effective operating time. Corresponding calculations are then performed to determine the original normal force and pitching moment. Clearly, for the rotated model, its normal force and pitching moment (i.e., the original lateral force and yaw moment before rotation) are no longer in a zero-stiffness support state and cannot be directly calculated using accelerometer measurements. In other words, by suspending the model in a predetermined attitude within a uniform wind tunnel flow field, the measurement data within the same effective operating time can only calculate a maximum of four degrees of freedom of aerodynamic loads.

[0118] Optionally, if the final measured parameters only include axial force, placing the model in the wind tunnel flow field with zero stiffness support includes:

[0119] The model is horizontally suspended using a suspension device. The suspension device includes a frame and two sets of suspension lines. Each set of suspension lines includes at least two oblique suspension lines. When suspending the model horizontally, the axial directions of both the frame and the model are adjusted to be horizontal. One set of suspension lines connects from the frame perpendicular to the axial direction of the model to the head of the model at the position with the least interference to the flow field. The other set of suspension lines connects from the frame perpendicular to the axial direction of the model to the tail end face of the model. The two sets of suspension lines are parallel and spaced apart. The two oblique suspension lines in each set are symmetrical with respect to the plane formed by the axial direction of the model and the direction of gravity. The bottom suspension points of the two oblique suspension lines are connected at the same point, or the distance between the top suspension points of the two oblique suspension lines is greater than the distance between the bottom suspension points.

[0120] By changing the attitude of the frame, the attitude of the model is adjusted to a preset attitude, so that the model is in the wind tunnel flow field with zero stiffness support in the axial direction during the effective time.

[0121] In the above embodiment, when suspending the model, viewed from the side, the two diagonal suspension lines are indistinguishable from a vertical line. The line connecting the top suspension points, the bottom suspension points, and the two sets of suspension lines approximately form a rectangle. Viewed from the front, the two diagonal suspension lines form a V-shape, exhibiting good stability in the thrust direction. The bottom suspension points of the two diagonal suspension lines in one set (i.e., the positions connected to the model) can be at the same location or relatively separated, but the distance should not be too large. If the bottom suspension points of the two diagonal suspension lines are at the same location, the model can be considered to be in a state of zero stiffness support in the roll direction in the wind tunnel. Using diagonal suspension lines for suspension makes the model less prone to deflection in the wind tunnel, but the final measurement parameters are more limited.

[0122] Furthermore, if it is determined that the model is placed in the wind tunnel flow field with zero stiffness support in step 110 using any of the above suspension methods, considering that the model will not spontaneously leave the wind tunnel flow field, in order to improve the safety of the test, it is preferable to set a stop device behind (or downstream) the model in the wind tunnel flow field to avoid the subsequent airflow continuing to act on the model after the measurement is completed, causing the model to fly around randomly in the wind tunnel test chamber.

[0123] Optionally, in step 110, the model is placed in the wind tunnel flow field with zero stiffness support, which can also be achieved by magnetic levitation.

[0124] Optionally, to ensure that the model does not rotate significantly within the effective operating time and that the aerodynamic load remains essentially unchanged, the model to be measured in this invention can be fabricated in the following manner:

[0125] Obtain wind tunnel flow field parameters and the geometry and dimensions of the model to be fabricated;

[0126] Based on the wind tunnel flow field parameters and the geometry and dimensions of the model, the magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field and the region where the pressure core is located are estimated through finite element simulation.

[0127] Based on the estimated magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field, as well as the preset angle change threshold and effective action time, the combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass is determined. The combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass includes multiple combinations of moment of inertia and distance from the center of pressure to the center of mass data where the attitude change does not exceed the angle change threshold within the effective action time.

[0128] Based on the combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass, the combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass is determined by the relationship between the moment of inertia and the mass. The combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass includes multiple combinations of mass, moment of inertia, and distance from the center of pressure to the center of mass data where the attitude change does not exceed the angle change threshold within the effective action time.

[0129] Using a multi-objective optimization method, within the combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass, the data values ​​of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass are selected.

[0130] Based on the estimated region of the model's center of gravity and the selected model's mass, moment of inertia, and distance from the center of gravity to the center of mass, the model's mass distribution is determined.

[0131] Based on the aforementioned geometry and dimensions, a model shell is fabricated;

[0132] Based on the determined mass distribution of the model, corresponding counterweights are set inside the manufactured model shell to obtain the model entity;

[0133] Based on the final measurement parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters, the accelerometer combination is determined. Determining the accelerometer combination includes determining the number of accelerometers, the final measurement parameters corresponding to each accelerometer, the expected installation position, the measurement range, and the measurement accuracy. The final measurement parameters include one or more of the following: axial force, normal force, lateral force, pitching moment, yaw moment, and roll moment.

[0134] Based on the determined accelerometer combination, the accelerometer combination and offline data acquisition device are embedded in the model entity to finally obtain the model for the experiment; the offline data acquisition device is connected to each of the accelerometers to collect and store the measurement results of the accelerometers.

[0135] Optionally, such as Figure 3 and Figure 4As shown, determining the accelerometer assembly based on the final measurement parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters includes:

[0136] If the final measured parameter includes pitch moment, then two identical single-axis accelerometers are installed on either the front or rear sides, or the top or bottom sides, of the model's center of mass. Both single-axis accelerometers on either the front or rear sides of the model's center of mass measure either upward or downward acceleration (i.e., both single-axis accelerometers on either the front or rear sides of the center of mass measure either the upward acceleration or the downward acceleration of the model). Figure 3 The accelerometers s1 and s2 shown in the figure are for ease of display. Figure 3 The volume of the accelerometer is not shown; only the arrow indicates the measurement direction of the accelerometer, and the position of the arrow shows the relative position of the accelerometer to the center of mass O. Two single-axis accelerometers are placed on the upper and lower sides of the model's center of mass to measure the acceleration of the model along the axial direction and in the opposite direction of the axial direction, respectively (i.e., one single-axis accelerometer on the upper and lower sides of the center of mass measures the acceleration of the model along the axial direction, and the other measures the acceleration of the model in the opposite direction of the axial direction). Figure 3 Accelerometers s10 and s11 are shown in the figure;

[0137] If the final measured parameter includes yaw moment, then two identical single-axis accelerometers should be installed on either the left or right sides or the front and rear sides of the model's center of mass. Both single-axis accelerometers installed on the left and right sides of the model's center of mass should measure the model's acceleration along the axial direction. Figure 3 The accelerometers s3 and s4 shown are two single-axis accelerometers positioned on either side of the model's center of mass, measuring the model's acceleration to the left or right. Figure 3 Accelerometers s8 and s9 are shown in the image.

[0138] If the final measured parameter includes rolling torque, then two identical single-axis accelerometers should be installed on either the left or right, or top or bottom, sides of the model's center of mass. Both single-axis accelerometers on the left and right sides of the model's center of mass should measure the model's upward or downward acceleration. Figure 3 The accelerometers s5 and s6 shown are two single-axis accelerometers positioned above and below the model's center of mass to measure the model's acceleration to the left and right, respectively. Figure 3 The accelerometers s12 and s13 are shown in the image.

[0139] It should be noted that the directional terms such as "up", "down", "left", "right", "front", and "back" in the above embodiments are all relative to the center of mass. The upper side is the side that is relatively far away from the ground, and the front side is the side that is relatively close to the incoming flow field.

[0140] The above embodiments, by setting accelerometers at corresponding locations, calculate the corresponding angular acceleration based on the linear acceleration measured by the accelerometers, and then solve for the torque. Compared with measuring displacement, measuring acceleration better reflects the aerodynamic load characteristics over a short period of time, and is also less expensive, with advantages such as objective and simple data processing and more reliable experimental data.

[0141] Furthermore, if the final measured parameters include axial force, the axial acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the left and right sides or the top and bottom sides of the model's center of mass.

[0142] If the final measured parameters include the normal force, the normal acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the front and rear sides of the model's center of mass.

[0143] If the final measured parameters include lateral force, the lateral acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the upper and lower sides or the front and rear sides of the model's center of mass.

[0144] The above embodiment uses two accelerometers to form a combination to measure and calculate motion acceleration. The force measurement can continue to use the accelerometers used for torque measurement. In other words, force and torque can be calculated simultaneously using two single-axis accelerometers. For example, two single-axis accelerometers positioned on either side of the center of mass measure upward acceleration. If the two accelerometers are symmetrical with respect to the center of mass, adding their measurements yields twice the normal linear acceleration, and subtracting them yields twice the pitch-rotational acceleration. Combining this with the accelerometer positions, the angular acceleration in the pitch direction can be determined. If the two accelerometers are not symmetrical with respect to the center of mass, the calculation can still be performed using the center of mass position and accelerometer placement. By using appropriate accelerometer combinations, combined with accelerometer placement and center of mass positions, the corresponding linear or rotational acceleration can be calculated, and thus the corresponding force or torque can be determined. Figure 4 As shown, assume two single-axis accelerometers are installed at points A and B on a certain axis, respectively. The measurement direction (i.e., the sensitive direction) is perpendicular to line segment AB. Point C is the center of mass, and point D is the center of pressure. The accelerometer at point A measures an acceleration a. A =a F +a mA The accelerometer at point B measures an acceleration a. B =a F +a mB a F Let a be the linear acceleration perpendicular to line segment AB. mA Let a be the linear acceleration (i.e., rotational acceleration) at point A caused by rotation. mBLet the linear acceleration at point B due to rotation be l1, the distance between AC and BC be l2, and the distance between DC be L. The aerodynamic force F acts on the center of pressure, rotating around the center of mass, producing an angular acceleration α. mA =αl1,a mB =-αl2, therefore a A -a B =a mA -a mB , (a A -a B ) / (l1+l2)=α=M / J, where M represents torque and J represents moment of inertia, thus M=(a A -a B )J / (l1+l2); Similarly, l1a mB / (l1+l2)+l2a mA / (l1+l2)=l1(-αl2) / (l1+l2)+l2(αl1) / (l1+l2)=0, then l1a A / (l1+l2)+l2a B / (l1+l2)=a F =F / m, where m represents mass, and F = [l1a] can be calculated. A / (l1+l2)+l2a B / (l1+l2)]m.

[0145] Preferably, the accelerometers are arranged at the vibration node or at a position symmetrical to the vibration node to reduce the interference of vibration on the measurement. Each accelerometer is preferably set on a coordinate axis with the center of mass as the origin O. If it is not on the coordinate axis, it needs to be projected onto the corresponding coordinate axis for calculation.

[0146] Furthermore, a triaxial accelerometer can be placed at the model's center of mass, such as... Figure 3 Accelerometer s7, located at the center of mass O, is used to measure the three-dimensional linear acceleration along the X, Y, and Z axes, thereby verifying and correcting the results calculated by the single-axis accelerometer. In the free state, the center of rotation of the model system is the center of mass, and there is no linear acceleration caused by rotation at accelerometer s7. Decoupling is not required, and the measured result is the translational acceleration of the model.

[0147] Optionally, determining the accelerometer assembly based on the final measurement parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters further includes:

[0148] Based on the final measured parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters, the expected installation positions of each accelerometer are determined.

[0149] Based on the expected installation location of each accelerometer and the estimated magnitude of the aerodynamic force on the model in the wind tunnel flow field, the numerical range of the measurement results of each accelerometer is determined respectively.

[0150] Based on the numerical range of the accelerometer measurement results, determine the accelerometer's measurement range and accuracy.

[0151] Using the above embodiments, it is possible to obtain a model with small attitude changes during the aerodynamic test with zero stiffness support and accurate measurement of aerodynamic signals.

[0152] In summary, this invention provides a method for measuring zero-stiffness supported aerodynamic forces based on a pulse-type wind tunnel, which has at least the following advantages:

[0153] Without the interference of struts or support devices, the flow field structure of the model is consistent with the actual object, making the simulation more realistic.

[0154] The frequency response has been improved from below 20Hz to above 1000Hz, making it more suitable for dynamic testing applications in shock tunnels;

[0155] It can realize aerodynamic tests on large-scale, large-mass models;

[0156] When the model has a large inertia (mass, rotational inertia), the disadvantage of a short effective shock tunnel interaction time becomes an advantage in terms of model attitude control. Assume the effective aerodynamic force F of the model is 200 N, the model mass m is 20 kg, and the model rotational inertia J is 0.2 kgm. 2 The torque M relative to the center of mass is 10 Nm, the effective action time t is 5 ms, the model's initial state is zero, and the displacement of the model during the effective action time is... The model's velocity is at = 0.05 m / s, and the model's attitude changes. Simply put, the model's displacement and attitude changes require time to accumulate. Within a very short effective time, the model's position and attitude remain almost unchanged under the influence of aerodynamic forces. Since the model's velocity is much smaller than the flow field velocity (3000 m / s), it can be approximated as the model being stationary in a certain attitude within the effective time. This is approximately equivalent to using the tail support rod to support the model in a certain attitude within the effective flow field.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the aerodynamic forces of a zero-stiffness support based on a pulse-type wind tunnel, characterized in that, include: The wind tunnel flow field parameters and the model entity parameters of the model to be measured are obtained. The model is embedded with an accelerometer assembly and an offline data acquisition device. The accelerometer assembly includes multiple accelerometers, and the offline data acquisition device is connected to each of the accelerometers to collect and store the measurement results of the accelerometers. Based on the wind tunnel flow field parameters and the model entity parameters, the magnitude of the aerodynamic force on the model in the wind tunnel flow field is estimated through finite element simulation. Based on the estimated magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field, the model entity parameters, and the effective duration of the wind tunnel flow field, the range of attitude angle changes of the model in the wind tunnel flow field is calculated. Determine whether the range of attitude angle change of the model in the wind tunnel flow field does not exceed the preset angle change threshold; if yes, continue. Determine the accelerometer combination parameters embedded in the model; the accelerometer combination parameters include the final measurement parameters, installation position, measurement range and measurement accuracy of each accelerometer respectively; The model was placed in the wind tunnel flow field with zero stiffness support, and the measurement results of all the accelerometers were obtained within the effective time. Based on the measurement results of all the accelerometers and the combined parameters of the accelerometers, the actual aerodynamic forces experienced by the model in the wind tunnel flow field are calculated. The model to be measured was created in the following manner: Obtain wind tunnel flow field parameters and the geometry and dimensions of the model to be fabricated; Based on the wind tunnel flow field parameters and the geometry and dimensions of the model, the magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field and the region where the pressure core is located are estimated through finite element simulation. Based on the estimated magnitude of the aerodynamic forces acting on the model in the wind tunnel flow field, as well as the preset angle change threshold and effective action time, the combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass is determined. The combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass includes multiple combinations of moment of inertia and distance from the center of pressure to the center of mass data where the attitude change does not exceed the angle change threshold within the effective action time. Based on the combined design range of the model's moment of inertia and the distance from the center of pressure to the center of mass, the combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass is determined by the relationship between the moment of inertia and the mass. The combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass includes multiple combinations of mass, moment of inertia, and distance from the center of pressure to the center of mass data where the attitude change does not exceed the angle change threshold within the effective action time. Using a multi-objective optimization method, within the combined design range of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass, the data values ​​of the model's mass, moment of inertia, and distance from the center of pressure to the center of mass are selected. Based on the estimated region of the model's center of gravity and the selected model's mass, moment of inertia, and distance from the center of gravity to the center of mass, the model's mass distribution is determined. Based on the aforementioned geometry and dimensions, a model shell is fabricated; Based on the determined mass distribution of the model, corresponding counterweights are set inside the manufactured model shell to obtain the model entity; Based on the final measurement parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters, the accelerometer combination is determined. Determining the accelerometer combination includes determining the number of accelerometers, the final measurement parameters corresponding to each accelerometer, the expected installation position, the measurement range, and the measurement accuracy. The final measurement parameters include one or more of the following: axial force, normal force, lateral force, pitching moment, yaw moment, and roll moment. Based on the determined accelerometer combination, the accelerometer combination and offline data acquisition device are embedded in the model entity to finally obtain the model for the experiment; the offline data acquisition device is connected to each of the accelerometers to collect and store the measurement results of the accelerometers.

2. The method according to claim 1, characterized in that, If the final measured parameters include one or more of axial force, normal force, lateral force, pitching moment, yaw moment, and roll moment, placing the model in the wind tunnel flow field with zero stiffness support includes: The model is placed above the uniform flow field region of the wind tunnel in a preset posture; The pure release allows the model to enter the uniform flow field region of the wind tunnel in the form of free fall, so that it is in the wind tunnel flow field with zero stiffness support during the effective time.

3. The method according to claim 1, characterized in that, If the final measured parameters include one or more of axial force, normal force, lateral force, pitching moment, yaw moment, and roll moment, placing the model in the wind tunnel flow field with zero stiffness support includes: The model is placed in a uniform flow field region of the wind tunnel in a preset posture by means of suspension or lifting. Remove the suspension or support structure, allowing the model to be placed in the wind tunnel flow field with zero stiffness support during the effective operating time.

4. The method according to claim 2 or 3, characterized in that, After determining that the attitude angle change range of the model in the wind tunnel flow field does not exceed a preset angle change threshold, and before placing the model in the wind tunnel flow field in the form of zero-stiffness support, the method further includes: Estimate the landing area of ​​the model; Based on the landing area of ​​the model, the installation location of the recycling device is determined, and the recycling device is installed.

5. The method according to claim 1, characterized in that, If the final measured parameters include one or more of axial force, lateral force, yaw moment, and roll moment, placing the model in the wind tunnel flow field with zero stiffness support includes: The model is suspended by a vertical line and placed in a predetermined posture within the uniform flow field of the wind tunnel, so that the model is in the wind tunnel flow field with zero stiffness support in the axial, lateral, yaw and roll directions during the effective time.

6. The method according to claim 5, characterized in that, The step of placing the model in a pre-set orientation within a uniform flow field region of the wind tunnel by suspending it vertically includes: The model is horizontally suspended using a suspension device. The suspension device includes a frame and two vertical lines. When suspending the model horizontally, the axial directions of both the frame and the model are adjusted to be horizontal. One vertical line is connected from the frame perpendicular to the axial direction of the model to the head of the model at the position with the least interference to the flow field. The other vertical line is connected from the frame perpendicular to the axial direction of the model to the tail end face of the model. The two vertical lines are parallel and spaced apart, and the upper and lower suspension points are both in the plane formed by the axis of the model and the direction of gravity. By changing the posture of the frame, the posture of the model is adjusted to a preset posture.

7. The method according to claim 1, characterized in that, If the final measured parameters only include axial force, placing the model in the wind tunnel flow field with zero stiffness support includes: The model is horizontally suspended using a suspension device. The suspension device includes a frame and two sets of suspension lines. Each set of suspension lines includes at least two oblique suspension lines. When suspending the model horizontally, the axial directions of both the frame and the model are adjusted to be horizontal. One set of suspension lines connects from the frame perpendicular to the axial direction of the model to the head of the model at the position with the least interference to the flow field. The other set of suspension lines connects from the frame perpendicular to the axial direction of the model to the tail end face of the model. The two sets of suspension lines are parallel and spaced apart. The two oblique suspension lines in each set are symmetrical with respect to the plane formed by the axial direction of the model and the direction of gravity. The bottom suspension points of the two oblique suspension lines are connected at the same point or the distance between the top suspension points is greater than the distance between the bottom suspension points. By changing the attitude of the frame, the attitude of the model is adjusted to a preset attitude, so that the model is in the wind tunnel flow field with zero stiffness support in the axial direction during the effective time.

8. The method according to claim 1, characterized in that, The determination of the accelerometer assembly based on the final measured parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters includes: If the final measured parameters include pitching moment, then two identical single-axis accelerometers are set up on the front and rear sides or the top and bottom sides of the center of mass of the model. The two single-axis accelerometers set up on the front and rear sides of the center of mass measure the upward or downward acceleration, and the two single-axis accelerometers set up on the top and bottom sides of the center of mass measure the acceleration of the model along the axial direction and along the axial direction in the opposite direction, respectively. If the final measured parameters include yaw moment, then two identical single-axis accelerometers are respectively set up on the left and right sides or front and rear sides of the center of mass of the model. The two single-axis accelerometers set up on the left and right sides of the center of mass measure the acceleration of the model along the axial direction, and the two single-axis accelerometers set up on the front and rear sides of the center of mass measure the acceleration of the model to the left or right. If the final measured parameter includes rolling torque, then two identical single-axis accelerometers are respectively placed on the left and right sides or the top and bottom sides of the center of mass of the model. The two single-axis accelerometers placed on the left and right sides of the center of mass measure the upward or downward acceleration of the model, and the two single-axis accelerometers placed on the top and bottom sides of the center of mass measure the leftward and rightward acceleration of the model, respectively. If the final measured parameters include axial force, then the axial acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the left and right sides or the top and bottom sides of the model's center of mass. If the final measured parameters include the normal force, the normal acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the front and rear sides of the model's center of mass. If the final measured parameters include lateral force, the lateral acceleration of the model is measured and calculated by placing two identical single-axis accelerometers on the upper and lower sides or the front and rear sides of the model's center of mass.

9. The method according to claim 8, characterized in that, The determination of the accelerometer assembly based on the final measured parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters also includes: Based on the final measured parameters, the actual parameters of the model entity, and the wind tunnel flow field parameters, the expected installation positions of each accelerometer are determined. Based on the expected installation location of each accelerometer and the estimated magnitude of the aerodynamic force on the model in the wind tunnel flow field, the numerical range of the measurement results of each accelerometer is determined respectively. Based on the numerical range of the accelerometer measurement results, determine the accelerometer's measurement range and accuracy.

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