Unsteady aerodynamic modeling method for compound control configuration for high angle of attack maneuvers

Abstract

The present invention proposes a method for modeling unsteady aerodynamic force of a composite control configuration for high angle of attack maneuvers. First, the composite control configuration is parameterized to determine the meaning and value range of the design parameters. Secondly, the design parameter values ​​are changed one by one within the value range, and the aerodynamic characteristics of the composite control configuration under different design parameter values ​​are calculated by the CFD method to obtain the time-averaged aerodynamic coefficient. Then, an equation considering the influence between the design parameters is constructed, and the unknown parameters in the equation are identified. Finally, based on the equation expression considering the influence between the design parameters, the physical characteristic characterization model of the final state space equation of the front elliptical wing-main wing composite control configuration is constructed. The constructed model has good aerodynamic force prediction capability and extrapolation generalization characteristics, breaking through the limitations of the applicability of existing high angle of attack aerodynamic force modeling technology to complex systems.

Description

Technical Field

[0001] The invention relates to the technical field of unsteady aerodynamic modeling, and in particular to an unsteady aerodynamic modeling method of a composite control configuration for high angle of attack maneuvers. Background Art

[0002] With the development of aviation technology, the problem of unsteady aerodynamic force at high angle of attack has gradually become the focus of attention in the field of aircraft design. Especially for the new generation of aircraft represented by high maneuverability flight performance, the excellent high-angle-of-attack over-stall flight capability is one of the key indicators to measure its comprehensive characteristics. During the high-angle-of-attack maneuvering movement of the aircraft, the aerodynamic force and motion are highly coupled, and a complex flow field will appear around it that is different from that during low-angle-of-attack and low-speed flight. During low-angle-of-attack and low-speed flight, the flow field distribution around the aircraft is stable, and the aerodynamic force has certain linear characteristics. However, during high-angle-of-attack maneuvering flight, there are a large number of flow separations and vortex breakups in the flow field, which produce strong nonlinear instantaneous aerodynamic forces and torques, directly affecting the expansion of the aircraft's flight envelope, flight performance, and survivability characteristics. Therefore, how to accurately predict the unsteady aerodynamic force at high angles of attack is of great significance to improving the flight performance of the aircraft and ensuring flight safety. When designing the aircraft, special attention should be paid to the evaluation and improvement of the unsteady aerodynamic characteristics of the aircraft during high-angle-of-attack maneuvering flight.

[0003] At present, there are three main methods for studying the aerodynamic characteristics of aircraft at high angles of attack: wind tunnel tests, numerical simulation methods, and aerodynamic modeling at high angles of attack. In general, when acquiring and analyzing unsteady aerodynamic data at high angles of attack, dynamic wind tunnel test research is time-consuming, labor-intensive, and difficult to carry out on a large scale. Computational fluid dynamics (CFD) simulation also has problems of insufficient accuracy and efficiency. Therefore, the unsteady aerodynamic modeling technology at high angles of attack has become a hot topic in the current research on aerodynamic design of advanced aircraft. Although the existing unsteady aerodynamic modeling technology can already characterize the dynamic aerodynamics at high angles of attack to a certain extent, it still needs further improvement and optimization in terms of versatility, physical meaning representation, and generalization characteristics. Under high angle flight conditions, the unsteady aerodynamic force caused by the separation flow will seriously reduce the aerodynamic performance of the aircraft at high angles of attack. It is usually necessary to use the active and passive flow control technology of adding components to the wing to improve the characteristics of the large separation flow field in order to improve the unsteady aerodynamic performance of the aircraft at high angles of attack. At this time, the wing and the flow control components together form a multi-body composite control configuration. The changes in its design parameters are highly correlated with the flow control effects under different working conditions, which in turn affect the unsteady aerodynamic changes of the entire aircraft. Therefore, it is necessary to improve the aerodynamic modeling method that regards the aircraft as a whole, and establish a set of unsteady aerodynamic modeling methods for multi-body composite control configurations.

[0004] Compared with other modeling methods, the state-space model takes the generation and breakup of vortices as the cause of aerodynamic changes, constructs vortex description variables, and brings the influence of vortices into the aerodynamic model for consideration. It has certain physical significance, and a definite aerodynamic model can be obtained through parameter identification, avoiding the artificial setting of polynomial models and the unclear physical meaning of intelligent methods such as neural networks. However, in actual calculations, traditional modeling methods generally consider the geometry, motion and aerodynamic properties of the aircraft configuration as a whole, take the macroscopic flow field mechanism as the starting point, and only consider the aerodynamic hysteresis characteristics as a factor of the angle of attack. It is difficult to make a reasonable and clear statement about the complex flow field interference between the various components of the multi-body composite control configuration and the influence of design parameters on the aerodynamic characteristics, and it is also impossible to predict the unsteady aerodynamic force after the system design parameters are changed. In addition, since there are too many unknown parameters to be identified in the original state-space equation, and the combination of design parameters of the composite control configuration is huge, if the influence relationship on the aerodynamic characteristics is directly added to the state-space model, the model solution speed and prediction accuracy will be greatly affected. Therefore, how to efficiently extract the key parameters of the compound control configuration during high angle of attack maneuvers, reasonably and accurately describe the influence of design parameters on the physical characteristics of the flow field, and then introduce them into the internal state quantities of the state-space equation is the key to realizing nonlinear aerodynamic modeling of multi-body compound control configuration at high angle of attack.

[0005] As a new type of active flow control method, the front elliptical wing-main wing composite control configuration forms a composite control configuration by adding a segmented small vibrating elliptical wing to the leading edge of the main wing to achieve the effect of improving aerodynamic performance. In the normal mode, the elliptical wing is also a lift component, which does not reduce the lift-drag performance of the overall configuration. During the high angle of attack maneuver, the front elliptical wing vibrates as needed to form high-energy flow, suppressing the separation of the vortex system of the main wing, thereby improving the transient aerodynamic characteristics of the entire system. Compared with the conventional active flow control method, the front elliptical wing-main wing system relies on the vibration of the small front elliptical wing to form a flow field interference effect with the main wing to achieve the purpose of improving the stall characteristics of the main wing. This configuration is a typical composite flow control configuration, and the realization of its flow field control requires the support of more complete flow field perception, modeling and control strategies. On the one hand, it is necessary to obtain the current flow field information in real time to set the input conditions for the movement of the front elliptical wing. On the other hand, it is necessary to integrate the complete aerodynamic model to determine the aerodynamic benefits brought by the movement in real time, and feedback to the control link for adjustment to achieve the best high angle of attack unsteady flow control effect. Therefore, characterizing and modeling the nonlinear flow field mechanism at large angles of attack for the front elliptical wing-main wing composite control configuration can provide technical support for the efficient unsteady aerodynamic design and performance evaluation of advanced aircraft.

[0006] If various flow control methods are to be applied to the actual application of flow field regulation in unsteady maneuvers at large angles of attack, it is necessary to clarify the aerodynamic response characteristics caused by changes in component parameters in the motion environment. This highly real-time process cannot be achieved through numerical simulation. Therefore, it is necessary to establish a complex system unsteady aerodynamic model at large angles of attack coupled with an active flow control configuration.

[0007] The commonly used high-angle-of-attack unsteady aerodynamic modeling methods now include conventional differential equations, integral equations modeling, and intelligent algorithm modeling. With the continuous improvement of the complexity of the flow field, especially the complex system coupled with active flow control technology, the disturbance parameters of the nonlinear flow field have increased dramatically. The aerodynamic modeling of high-angle-of-attack maneuvers based on intelligent algorithms has received more extensive attention, and a variety of aerodynamic models based on neural networks have been developed. However, despite the rapid development of aerodynamic modeling in recent years, there are still key technical difficulties that have not been resolved, mainly in the following aspects: First, the accuracy and efficiency of modeling. The traditional model is limited by its own model structure, and the prediction accuracy of aerodynamics needs to be further improved. In addition, the traditional unsteady aerodynamic model has many unknown parameters, and the parameter identification method has the disadvantage of low efficiency; second, the physical meaning of the model is expressed. The physical meaning of traditional models is relatively clear, but the expression of parameters in the models is not complete. Modern intelligent models are "black box" models, and the representation ability of the physical mechanism of the flow field is very weak, making it difficult to understand the physical mechanism. In addition, the modeling objects of both are for a single overall configuration, and the interference effect of multi-body components is not considered. The third is generalization ability. The generalization ability is mainly reflected in the model's ability to predict the aerodynamic results of unknown states. At present, both traditional and modern intelligent models have the defect of insufficient generalization ability, especially the extrapolation prediction ability, which still has great room for improvement. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention proposes a method for unsteady aerodynamic modeling of a compound control configuration for high-angle-of-attack maneuvers, which has good aerodynamic prediction capability and extrapolation generalization characteristics, breaks through the limitations of the existing high-angle-of-attack aerodynamic modeling technology in terms of applicability to complex systems, and describes the aerodynamic characteristics of the compound control configuration while taking into account both physical significance and practical value of flow field control. At the same time, it also provides a new idea for the study of the unsteady flow field dynamics mechanism and comprehensive flow field regulation of the compound flow control configuration.

[0009] The technical solution of the present invention is:

[0010] The method for modeling unsteady aerodynamic force of a composite control configuration for high angle of attack maneuvers comprises the following steps:

[0011] Step 1: Perform parameterized design on the front elliptical wing-main wing composite control configuration, determine the meaning and value range of the design parameters, and perform dimensionless processing on all design parameters; the design parameters include the angle of attack of the front elliptical wing , the horizontal distance from the center of the front elliptical wing to the leading edge of the main wing and vertical distance ;

[0012] Step 2: Use the control variable method to change the design parameter values ​​one by one within the value range, and calculate the aerodynamic characteristics of the front elliptical wing-main wing composite control configuration under different design parameter values ​​through numerical simulation methods to obtain the time-averaged aerodynamic force coefficient and aerodynamic moment coefficient of the front elliptical wing-main wing composite control configuration under different design parameter values. ,in is the time-averaged lift coefficient, is the time-averaged resistance coefficient, is the time-averaged pitching moment coefficient;

[0013] Step 3: Construct a set of equations describing the effect of a single design parameter on the time-averaged aerodynamic force of the front elliptical wing-main wing composite control configuration:

[0014]

[0015] in, is a natural constant, and To correct The value range of and the parameters for determining the peak position, To control the function The peak height parameter, and To correct The value range and parameters for determining the peak position, To control the function The peak height parameter, is a sine function The middle value of is a sine function The amplitude of is a sine function The initial phase of

[0016] Step 4: Based on the equations constructed in step 3, construct equations that consider the influence between design parameters:

[0017]

[0018] in All are unknown parameters to be identified;

[0019] Step 5: Within the range of design parameter values, select the design parameter combination through the orthogonal experimental design method and establish an orthogonal table;

[0020] Step 6: Use numerical simulation method to calculate the aerodynamic characteristics of the front elliptical wing-main wing composite control configuration under different design parameter combinations in the orthogonal table, and obtain the aerodynamic force coefficient and aerodynamic moment coefficient under different design parameter combinations in the orthogonal table. According to the obtained aerodynamic force coefficient and aerodynamic moment coefficient, identify the unknown parameters in the equation established in step 4, and obtain Expression of

[0021] Step 7: Based on the result from step 6 The final state space equation physical characteristic characterization model of the front elliptical wing-main wing composite control configuration is constructed as follows:

[0022]

[0023] in is the internal state quantity, representing the distance from the flow separation point on the main wing upper surface to the leading edge of the main wing, for The dimensionless representation of ; is the main wing angle of attack, for The first-order rate of change of for The dimensionless form of All are time constants; is the slope factor, is the angle of attack corresponding to the separation point reaching the midpoint of the chord line of the main wing airfoil under steady state; is a constant, the partial derivative Both The unknown parameters obtained through model identification are ; The input variables of the state space equation physical property characterization model are And design parameters , the output is the aerodynamic force coefficient and aerodynamic moment coefficient .

[0024] Furthermore, in step 1, the angle of attack of the front elliptical wing The value range is , the corresponding dimensionless parameter is , is the average angle of attack of the pitch oscillation of the compound control configuration; the horizontal distance from the center of the front elliptical wing to the leading edge of the main wing The value range is , the corresponding dimensionless parameter is , The chord length of the main wing airfoil; the vertical distance from the center of the front elliptical wing to the leading edge of the main wing The value range is , the corresponding dimensionless parameter is .

[0025] Furthermore, during the pitching motion of the front elliptical wing-main wing composite control configuration, the main wing performs reciprocating pitching motion around the moment center, and the front elliptical wing is relatively stationary.

[0026] Furthermore, the equation established in step 4 is given by It consists of four parts, including The formula together constitutes a three-dimensional surface with multiple peaks in the local area. By associating elliptic equations and polynomials, Formula in will Added on an associated basis impact.

[0027] Furthermore, the equation established in step 4 can be realized when When the value of exceeds the design space, the The impact of change.

[0028] Furthermore, in step 7, the partial derivative Expressed as a quadratic polynomial:

[0029]

[0030] In the formula, are constants, ;and can be identified through model identification.

[0031] Furthermore, in step 7, The dimensionless form of , represents the characteristic time of the flow, is the free flow speed.

[0032] Furthermore, in step 7, the time constant It reflects the formation process of unsteady equilibrium separation flow. It reflects the separation hysteresis characteristics of flow.

[0033] The key technical points of the present invention are:

[0034] 1. The method of constructing equations between the design parameters of the composite control configuration and the aerodynamic coefficients is to first establish a set of equations for the influence of a single design parameter on the aerodynamic force, and then use mathematical forms to reasonably link them into one equation.

[0035] 2. The orthogonal experimental design method is used to reduce the amount of numerical simulation calculations, and the constructed design parameter equations are first identified and then added to the internal state quantities. The advantage of step-by-step identification is that the state space model of the composite control configuration does not add unknown parameters compared to the original model, which can reduce the difficulty of parameter identification and improve prediction accuracy.

[0036] 3. Through comparative analysis of the hysteresis loop of the aerodynamic coefficients of the composite control configuration and the original airfoil, the physical quantity in the original state-space model that has the greatest impact on the aerodynamic force after the design parameters are changed is identified, and then the position and form of adding the established composite control configuration design parameter equation to the internal state quantity of the original state-space model is determined.

[0037] Beneficial Effects

[0038] The present invention targets the complex flow field characteristics of the new flow control technology represented by the front elliptical wing-main wing composite control configuration, incorporates the nonlinear flow field physical characterization method, explores the influence of various interference parameters, controls the increase in the number of unknown parameters to reduce the difficulty of parameter identification, and comprehensively considers the model prediction accuracy and generalization ability to construct an efficient, practical and interpretable large-angle-of-attack unsteady aerodynamic model with physical significance, which provides a new way for the dynamic aerodynamic evaluation of composite flow control systems, and at the same time provides a theoretical basis and technical support for the large-angle-of-attack unsteady aerodynamic design, flight dynamics analysis and control strategy research of advanced aircraft.

[0039] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0041] Figure 1 :Flow control mechanism of front elliptical wing-main wing composite control configuration;

[0042] In the figure: 1. Main wing; 2. Front elliptical wing; 3. Moment center; 4. Separation zone; 5. Elliptical wing tail vortex; 6. Slot accelerated airflow;

[0043] Figure 2 : Schematic diagram of the front elliptical wing-main wing composite control configuration scheme; in the figure, the main wing performs reciprocating pitching motion around the moment center, and the front elliptical wing is relatively stationary;

[0044] Figure 3 : Schematic diagram of position parameters of front elliptical wing-main wing composite control configuration;

[0045] In the figure, is the main wing angle of attack; is the angle of attack of the front elliptical wing;

[0046] Figure 4 : Schematic diagram of the front elliptical wing-main wing composite control configuration and design space;

[0047] In the figure, 7, the design space; It is the horizontal distance from the center of the front elliptical wing to the leading edge of the main wing; It is the vertical distance from the center of the front elliptical wing to the leading edge of the main wing;

[0048] Figure 5 : Time-averaged lift coefficient The impact of

[0049] Figure 6 : Time-averaged drag coefficient The impact of

[0050] Figure 7 : Time-averaged pitch moment coefficient The impact of

[0051] Figure 8 : Time-averaged lift coefficient The impact of

[0052] Fig. 9 : Time-averaged drag coefficient The impact of

[0053] Fig.10 : Time-averaged pitch moment coefficient The impact of

[0054] Fig.11 : Time-averaged lift coefficient The impact of

[0055] Fig.12 : Time-averaged drag coefficient The impact of

[0056] Fig.13 : Time-averaged pitch moment coefficient The impact of

[0057] Fig.14 : Comparison of unsteady lift coefficients between the composite control configuration and the original airfoil;

[0058] Fig.15: Comparison of unsteady drag coefficient between the composite control configuration and the original airfoil;

[0059] Fig.16 : Comparison of unsteady pitching moment coefficients between the composite control configuration and the original airfoil;

[0060] Fig.17 :Comparison between the calculated and predicted values ​​of lift coefficient in Example 1;

[0061] Fig.18 :Comparison between the calculated and predicted values ​​of the drag coefficient in Example 1;

[0062] Fig.19 :Comparison between the calculated and predicted values ​​of the pitching moment coefficient in Example 1;

[0063] Fig. 20 :Comparison between the calculated and predicted values ​​of lift coefficient in Example 2;

[0064] Fig.21 :Comparison between the calculated and predicted values ​​of the drag coefficient in Example 2;

[0065] Fig. 22 :Comparison between the calculated and predicted values ​​of the pitching moment coefficient in Example 2;

[0066] Fig.23 :Comparison between the calculated and predicted values ​​of lift coefficient in Example 3;

[0067] Fig.24 : Comparison between the calculated and predicted values ​​of the drag coefficient in Example 3;

[0068] Fig.25 :Comparison between the calculated and predicted values ​​of the pitching moment coefficient in Example 3;

[0069] Fig.26 :Comparison between the calculated and predicted values ​​of lift coefficient in Example 4;

[0070] Fig. 27 : Comparison between the calculated and predicted values ​​of the drag coefficient in Example 4;

[0071] Fig.28 :Comparison between the calculated and predicted values ​​of the pitching moment coefficient in Example 4;

[0072] Fig.29 :Comparison between the calculated and predicted values ​​of lift coefficient in Example 5;

[0073] Fig.30 : Comparison between the calculated and predicted values ​​of the drag coefficient in Example 5;

[0074] Fig.31 :Comparison between the calculated and predicted values ​​of the pitching moment coefficient in Example 5;

[0075] Fig.32 :Comparison between the calculated and predicted values ​​of lift coefficient in Example 6;

[0076] Fig.33 : Comparison between the calculated and predicted values ​​of the drag coefficient in Example 6;

[0077] Fig.34 :Comparison between the calculated and predicted values ​​of the pitching moment coefficient in Example 6;

[0078] Fig.35 :Comparison between the calculated and predicted values ​​of lift coefficient in Example 7;

[0079] Fig.36 : Comparison between the calculated and predicted values ​​of the drag coefficient in Example 7;

[0080] Fig.37 : Comparison between the calculated and predicted values ​​of the pitching moment coefficient in Example 7. DETAILED DESCRIPTION

[0081] Embodiments of the present invention are described in detail below. The embodiments are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0082] The front elliptical wing-main wing composite control configuration consists of two parts: the main wing and the elliptical wing set in front of its leading edge point. Figure 1 As shown in the figure, the flow control effect is mainly based on the gap formed between the two and the dynamic wake generated by the front elliptical wing. The main influencing parameters are reflected in the relative geometric parameters, position parameters, motion parameters, etc. of the front elliptical wing and the main wing. When the front elliptical wing-main wing composite control configuration performs large angle of attack maneuvers, the flow field will show obvious "time and space" interference phenomenon, and the change of its design parameters will also cause different interferences to the unsteady aerodynamic force of the composite control configuration. For the front elliptical wing, the subsonic airflow disturbance generated by its downstream main wing will propagate upstream and affect the lift and drag characteristics of the front elliptical wing itself, and the gap between the front elliptical wing and the main wing will also change the flow of its rear wing section. The flow field of the main wing is greatly affected by the disturbance of the front elliptical wing. On the one hand, the gap formed between the two changes the quality of the incoming flow at the leading edge of the main wing. On the other hand, the unsteady wake of the front elliptical wing will also affect the flow on the upper wing surface of the main wing in real time. The overall aerodynamic characteristics of this composite control configuration are closely related to the mutual interference between components, and the aerodynamics and motion are highly coupled. It should be noted that in the field of fluid mechanics and aircraft design, the concept of high angle of attack is a concept that is clear to those skilled in the art. It is generally believed that when the angle of attack reaches The above is a high angle of attack. When the aircraft enters a high angle of attack state, the airflow on the upper surface of the wing will separate and produce a separation vortex.

[0083] Although the changes in the flow field characteristics of the composite control configuration under different parameter combinations can be obtained through numerical simulation analysis, it is difficult to intuitively express the relationship between each parameter and the aerodynamic force and flow field characteristics. Therefore, it is necessary to introduce the state space equation theory based on the study of the flow field mechanism, based on the basic state space equation principle, consider the individual and correlation effects between the front elliptical wing and the main wing, add the physical quantities of the design parameters of the front elliptical wing-main wing composite control configuration to the internal state quantities that characterize the aerodynamic separation characteristics of the high angle of attack maneuvering motion, use differential equations to describe the development and change process of unsteady flow field separation, and establish an unsteady flow field physical characterization method suitable for the composite control configuration.

[0084] In this embodiment, the unsteady aerodynamic modeling for the front elliptical wing-main wing composite control configuration mainly includes the following steps:

[0085] Step 1: Perform parameterized design on the front elliptical wing-main wing composite control configuration, clarify the meaning and value range of each design parameter, and make all design parameters dimensionless.

[0086] The present invention uses the relative position parameters of the front elliptical wing-main wing composite control configuration as the design parameters for research. The main wing airfoil uses a typical NACA0012 airfoil with a chord length of , the average angle of attack of pitch oscillation is , the amplitude is , the dimensionless angular velocity is , angle of attack The law of movement is The major axis length of the front elliptical wing is 0.02 , the minor axis length is 0.01 During the pitching motion of the compound control configuration, the main wing performs reciprocating pitching motion around the moment center, while the front elliptical wing is relatively stationary. Figure 2 The relative position parameters include the angle of attack of the front elliptical wing , the horizontal distance from the center of the front elliptical wing to the leading edge of the main wing and vertical distance ,like Figure 3 and Figure 4 shown.

[0087] Table 1 gives the relative position parameters of the front elliptical wing-main wing composite control configuration as design parameters and their respective value ranges. In order to deeply explore the influence of the correlation between the front elliptical wing and the main wing, study its objective laws, and improve the efficiency of analysis and modeling, the design parameters are dimensionless.

[0088] Table 1 Design parameters of the front elliptical wing-main wing composite control configuration

[0089]

[0090] Step 2: Using the control variable method, change the design parameter values ​​one by one within the value range, and use a high-precision numerical simulation method to calculate the aerodynamic characteristics of the composite control configuration under different design parameter values, and obtain the time-averaged aerodynamic force coefficient and aerodynamic moment coefficient of the composite control configuration under different design parameter values.

[0091] The numerical simulation analysis of the front elliptical wing-main wing composite control configuration is carried out, and the calculation conditions are as follows: , , , , , the initial dimensionless design parameter is , and The control variable method is used to change the design parameter values ​​in sequence to obtain the unsteady aerodynamic force coefficients and moment coefficients of the composite control configuration with different design parameter combinations under large angle of attack pitch oscillation. And the time-averaged aerodynamic force coefficient and moment coefficient in a motion cycle ,in is the unsteady lift coefficient, is the unsteady resistance coefficient, is the unsteady pitching moment coefficient, is the time-averaged lift coefficient, is the time-averaged resistance coefficient, is the time-averaged pitch moment coefficient. In order to explore the influence of a single design parameter on the aerodynamic performance of the compound control configuration, the time-averaged aerodynamic force coefficient and aerodynamic moment coefficient of the compound control configuration are compared with those of the single main wing. Figure 5-Figure 13 shown.

[0092] Step 3: Based on the numerical simulation results and referring to the Gaussian mixture model, a set of equations containing unknown parameters is constructed, where the independent variables of the equations are the design parameters, and the dependent variables are the aerodynamic coefficients and aerodynamic moment coefficients of the composite control configuration. The number of equations is the same as the number of design parameters. This set of equations is used to describe the influence of a single design parameter on the time-averaged aerodynamic force of the composite control configuration.

[0093] According to the time-averaged aerodynamic variation trend of the composite control configuration under different design parameter values ​​obtained in step 2, it can be seen that and There is a certain effective range of values. Within this range, the time-averaged aerodynamic force of the composite control configuration will have one or more peaks as the single design parameter increases. and When the value of exceeds its effective range, the time-averaged aerodynamic force of the composite control configuration begins to infinitely approach a constant close to the time-averaged aerodynamic force of the single main wing. It can be considered that the mutual interference between the front elliptical wing and the main wing is small enough to be ignored. This mathematical characteristic can be described by the Gaussian Mixed Model (GMM) obtained by superimposing multiple Gaussian distributions. and , It is a minor factor affecting the aerodynamic performance of the composite control configuration. , Under the value of The value of fluctuates up and down, and this mathematical characteristic can be approximated by the sine function. Based on the above analysis, a set of unknown parameters is initially constructed. The equation to describe the effect of a single design parameter on the time-averaged aerodynamic force of the composite control configuration is:

[0094]

[0095] in, is a natural constant, and To correct The value range and parameters for determining the peak position, To control the function The peak height parameter uses a polynomial to change the peak shape to adapt to different aerodynamic changes. and To correct The value range and parameters for determining the peak position, To control the function Parameter for peak height. is a sine function The middle value of is a sine function The amplitude of is a sine function The initial phase.

[0096] Step 4: Use mathematical forms such as polynomials and elliptical distribution to relate the design parameters to each other. Based on the equations built in step 3, construct an equation that takes into account the complex influences between the design parameters. The independent variables of this equation are all the design parameters, and the dependent variable is the aerodynamic force of the composite control configuration.

[0097] In fact, since the aerodynamic characteristics of the composite control configuration will be affected by the values ​​of the three design parameters at the same time, and there is complex mutual interference between these parameter combinations rather than simple linear superposition, it is necessary to further rewrite the equations established in step 3. Construct equations as independent variables that are correlated with each other:

[0098]

[0099] The equation is based on Gaussian distribution, polynomial and elliptical shapes and consists of four parts, taking into account the design parameters The correlation between the composite control configuration and the main wing airfoil separation can characterize the overall flow control effect of the composite control configuration under different design parameter combinations and the macroscopic influence on the aerodynamic coefficient of the system. The physical meaning is the same as step 3, the unknown parameter and Similarly, it is used to control the peak height, while the polynomial part causes the shape of the peak or trough to change. The formula together constitutes a three-dimensional surface with multiple peaks in the local area. By associating elliptic equations and polynomials, On this basis, the formula adds The impact of ,Right now When the value of exceeds the design space, The impact of the changes will be greatly reduced.

[0100] Step 5: Since the number of combinations of design parameters is huge, in order to reduce the calculation cost, the orthogonal experimental design method is used to select appropriate parameter combinations within the value range and establish an orthogonal table.

[0101] In the process of modeling the unsteady aerodynamic force of the composite control configuration, it is first necessary to identify the unknown parameters in the equation based on the numerical simulation results. In order to reduce the amount of calculation, save calculation time, and efficiently extract the influence of different design parameter combinations on the flow field characteristics of the composite control configuration during the high angle of attack maneuver, based on the existing calculation results, within the range of design parameter values, the design parameter combination is selected through the orthogonal experimental design method, and a three-factor six-level orthogonal table is constructed. , as shown in Table 2.

[0102] Table 2 Factors and levels of orthogonal experiment

[0103]

[0104] Step 6: Use numerical simulation method to calculate the aerodynamic characteristics of the front elliptical wing-main wing composite control configuration under different design parameter combinations in the orthogonal table, obtain the aerodynamic data under different design parameter combinations in the orthogonal table, and use these data to identify the unknown parameters in the equations constructed above, and obtain expression.

[0105] The composite control configurations of 36 groups of different parameter combinations selected by orthogonal test method were calculated and their corresponding , and use these data to identify the parameters in the equation, and the results are shown in Table 3. The relative error of The error is slightly larger, but still within the acceptable range. The following parameter values ​​are used to model the unsteady aerodynamic force of the composite control configuration to reduce the difficulty of identification caused by the increase of unknown parameters in the state space equation.

[0106] Table 3 Parameter identification results

[0107]

[0108] Step 7: Based on the numerical simulation results, the hysteresis loop of the aerodynamic coefficient of the composite control configuration with different design parameters as the angle of attack changes is compared with the hysteresis loop of the aerodynamic coefficient of a single main wing as the angle of attack changes, and the maximum relevant influence of the design parameter change on the aerodynamic coefficient is explored, providing a reference and basis for adding the design parameters to the position of the original state space model.

[0109] The unsteady aerodynamic force of the compound control configuration during pitching motion is closely related to the instantaneous angle of attack. The design parameter combination has different effects on the aerodynamic changes of the compound control configuration at different angles of attack. Figure 14-16 The changes of aerodynamic force of the compound control configuration and a single main wing with angle of attack were compared under the initial design parameter values. Since the front elliptical wing has a certain control effect on the flow separation on the main wing surface, the shape of the hysteresis loop of the compound control configuration changes significantly compared with the single main wing under large angle of attack. In the case of small angle of attack, the flow on the main wing surface is an attached flow, and the unsteady aerodynamic force of the compound control configuration is close to that of the single main wing. In summary, when establishing the state space model of the compound control configuration, in order to accurately describe the flow control effect of the compound control configuration on the main wing during the change of angle of attack, it is necessary to focus on the change of the flow separation point position caused by the change of design parameters.

[0110] Therefore, based on the basic principle of state-space equations, the physical quantities of the design parameters of the front elliptical wing-main wing composite control configuration are added to the internal state quantities that characterize the aerodynamic separation characteristics of high angle of attack maneuvers to complete the unsteady aerodynamic modeling of the composite control configuration.

[0111] Based on the basic state space equation principle, the aerodynamic separation characteristics of the compound control configuration under high angle of attack maneuver are expressed as internal state quantities. Indicates. Among them, represents the distance from the flow separation point on the main wing upper surface to the leading edge of the main wing. The dimensionless expression of the internal state quantity is x ¯ = x / c ∈ [ 0 , 1 ] , its physical meaning is the relative position of the flow separation point on the main wing surface. When , this corresponds to the attachment flow under a small angle of attack. When , this corresponds to the complete separation flow at the leading edge of the flow separation point. In the basic state space equation, Goman et al., after analyzing a large amount of experimental data, used a differential equation to describe the separation characteristics of the flow:

[0112]

[0113] in, are all time constants, It reflects the formation process of unsteady equilibrium separation flow. It reflects the separation hysteresis characteristics of flow. Angle of attack The first-order rate of change of . Function The relationship between the flow separation point position and the angle of attack under steady flow conditions is approximately expressed by a natural function, and the relationship is:

[0114]

[0115] in, is the slope factor, It corresponds to the angle of attack when the separation point reaches the midpoint of the main wing airfoil chord under steady state.

[0116] The constructed equation Add function , introduce the influence of various design parameter combinations on the aerodynamic force and flow field characteristics of the composite control configuration, and use differential equations to describe the development and change process of unsteady flow field separation. In particular, it is considered that right The influence of is a quadratic relationship to highlight the influence of design parameters on the separation point location:

[0117]

[0118] Combined with the modeling principle of the state space model, the unsteady aerodynamic force and moment at large angle of attack can be written as dimensionless internal state quantities: and multi-order quantities of angle of attack Function:

[0119]

[0120] In actual work, except for a few cases with high-frequency vibration, the second-order rate of change of the angle of attack The higher-order terms have little effect on the aerodynamic force and moment, so the formula is simplified to:

[0121]

[0122] Taylor expand the formula, write it in the form of a polynomial, and get the second-order term:

[0123]

[0124] Non-dimensionalizing the simplified expression yields:

[0125]

[0126] in, is the dimensionless form of the first-order rate of change of the angle of attack, represents the characteristic time of the flow, is the velocity of the free stream. The partial derivatives in each term are dimensionless internal state quantities The specific form of the function is approximated by a quadratic polynomial:

[0127]

[0128] In the formula, are all constants.

[0129] By establishing the state space equation of the aerodynamic force of the front elliptical wing-main wing composite control configuration and then combining it with the output equation, the physical characteristic characterization model of the final state space equation of the composite control configuration can be obtained. The expression is as follows:

[0130]

[0131] In the high-angle-of-attack unsteady aerodynamic state-space model of the front elliptical wing-main wing composite control configuration, the unknown parameters obtained through model identification include , which is consistent with the original state space model. The input variables of the model are And three design parameters of the composite control configuration The model output is the aerodynamic coefficient and aerodynamic moment coefficient .

[0132] Simulation verification:

[0133] Based on the unsteady aerodynamic modeling method of the above-mentioned composite control configuration, the following aerodynamic example of the pitch motion of the front elliptical wing-main wing composite control configuration calculated by the CFD method verifies the rationality of the state space model structure for the multi-body composite control configuration proposed in the present invention as well as the accuracy and applicability of the model. The basic prediction ability of the model is tested by three groups of examples with different design parameter values, and the generalization ability of the model is tested by three groups of examples with changing single parameter values ​​and one group of examples with random values. The calculation conditions are: , , , , .

[0134] (1) Verification of model basic prediction ability

[0135] For the front elliptical wing-main wing composite control configuration, three groups of simple harmonic motion examples with different design parameter combinations were selected to verify the basic prediction ability and prediction accuracy of the established model.

[0136] Calculation example 1: , ,

[0137] Calculation example 2: , ,

[0138] Calculation example 3: , ,

[0139] Figure 17-Figure 25 A comparison between the calculated and predicted values ​​of the aerodynamic coefficients of the compound control configurations in Examples 1, 2, and 3 is given. It can be seen that the state-space model fits the overall trend of the hysteresis loop of the unsteady aerodynamic coefficients of the compound control configurations well, and the predicted values ​​are almost consistent with the calculated values, indicating that the model established by the present invention can complete the prediction of unsteady aerodynamic forces for compound control configurations with different parameters with high accuracy.

[0140] The root mean square error and relative error of the compound control configuration state space model for the prediction results of the aerodynamic coefficients are shown in Table 4. For the lift coefficient and drag coefficient of the compound control configuration under different parameter combinations, the relative errors between the predicted value and the calculated value are basically less than 1.5%, while the error of the pitch moment coefficient is slightly larger. Due to the limited accuracy of the parameter identification method, the absolute value of the pitch moment coefficient is small in magnitude, which makes it impossible to obtain a completely accurate pitch moment coefficient model. The original Goman state space model also has the same problem when predicting aerodynamic coefficients. In general, the compound control configuration state space model has basic prediction capabilities, and the modeling results are relatively ideal.

[0141] Table 4 Comparison of aerodynamic coefficient prediction errors

[0142]

[0143] (2) Verification of model generalization ability

[0144] After determining the prediction accuracy of the model, the generalization ability of the model was verified using four sets of examples, each of which contained two sets of training data and one set of test data.

[0145] Calculation example 4:

[0146] The design parameter values ​​of the training data are:

[0147] , ,

[0148] , ,

[0149] The design parameter values ​​of the test data are:

[0150] , ,

[0151] Calculation example 5:

[0152] The design parameter values ​​of the training data are:

[0153] , ,

[0154] , ,

[0155] The design parameter values ​​of the test data are:

[0156] , ,

[0157] Calculation example 6:

[0158] The design parameter values ​​of the training data are:

[0159] , ,

[0160] , ,

[0161] The design parameter values ​​of the test data are:

[0162] , ,

[0163] Calculation example 7:

[0164] The design parameter values ​​of the training data are:

[0165] , ,

[0166] , ,

[0167] The design parameter values ​​of the test data are:

[0168] , ,

[0169] The comparison between the predicted results and the calculated values ​​of the above examples is shown in Figure 26-Figure 37 As shown, examples 4 and 5 are interpolation predictions, and examples 6 and 7 are extrapolation predictions. It can be seen that the aerodynamic coefficients output by the state-space model of the compound control configuration are relatively close to the calculated values, and the rising or falling trend of the hysteresis loop is accurately predicted, indicating that the physical significance of the improved state-space model is further enhanced and the improvement method is reasonable.

[0170] The root mean square error and relative error of the aerodynamic coefficient prediction results of the composite control configuration state space model in the four groups of examples are shown in Table 5. Compared with the original Goman state space model, the improved state space model proposed in the present invention additionally includes the design parameters of the composite control configuration, which can predict the unsteady aerodynamic force of the composite control configuration with different parameter values. Although the error of the model extrapolation prediction is larger than that of the interpolation prediction, the error mainly comes from the prediction of the aerodynamic coefficient at a large angle of attack, when the flow field state on the airfoil surface is complex, the hysteresis effect is enhanced, and the nonlinearity of the aerodynamic force is more prominent; but compared with the original Goman state space model and other methods in this field, the accuracy of the model extrapolation prediction results meets the requirements of engineering applications. On the whole, the composite control configuration state space model has generalization ability, and the prediction error is within an acceptable range.

[0171] Table 5 Comparison of aerodynamic coefficient prediction errors

[0172]

[0173] The present invention constructs a high-angle-of-attack unsteady aerodynamic state-space model of a front elliptical wing-main wing composite control configuration based on the physical mechanism of the interference of the two-wing flow field. By analyzing the correlation between the disturbance parameters of the front elliptical wing and the main wing, the separation point equation of the state-space equation is redefined. The model, based on the physical mechanism, has good aerodynamic prediction ability and certain extrapolation generalization characteristics for the composite control configuration. The method is verified based on the CFD simulation results. The results show that the maximum root mean square error of the retrospective prediction of the lift, drag and moment coefficients of the original sample data does not exceed 0.01, and the maximum root mean square error of the generalized prediction of other composite control configurations after parameter change does not exceed 0.1. It can be seen that the modeling method breaks through the limitations of the applicability of the existing high-angle-of-attack aerodynamic modeling technology to complex systems, and the aerodynamic characteristics of the composite control configuration are expressed in terms of both physical significance and practical value of flow field control. At the same time, it also provides a new idea for the study of the unsteady flow field dynamics mechanism and comprehensive flow field regulation of the composite control configuration.

[0174] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers, characterized in that: The following steps are involved: Step 1: Perform parameterized design on the front elliptical wing-main wing composite control configuration, determine the meaning and value range of the design parameters, and perform dimensionless processing on all design parameters; the design parameters include the angle of attack of the front elliptical wing , the horizontal distance from the center of the front elliptical wing to the leading edge of the main wing and vertical distance ; Step 2: Use the control variable method to change the design parameter values ​​one by one within the value range, and calculate the aerodynamic characteristics of the front elliptical wing-main wing composite control configuration under different design parameter values ​​through numerical simulation methods to obtain the time-averaged aerodynamic force coefficient and aerodynamic moment coefficient of the front elliptical wing-main wing composite control configuration under different design parameter values. ,in is the time-averaged lift coefficient, is the time-averaged resistance coefficient, is the time-averaged pitching moment coefficient; Step 3: Construct a set of equations describing the effect of a single design parameter on the time-averaged aerodynamic force of the front elliptical wing-main wing composite control configuration: in, is a natural constant, and To correct The value range of and the parameters for determining the peak position, To control the function The peak height parameter, and To correct The value range of and the parameters for determining the peak position, To control the function The peak height parameter, is a sine function The middle value of is a sine function The amplitude of is a sine function The initial phase of Step 4: Based on the equations constructed in step 3, construct equations that consider the influence between design parameters: in are all unknown parameters to be identified; Step 5: Within the range of design parameter values, select the design parameter combination through the orthogonal experimental design method and establish an orthogonal table; Step 6: Use numerical simulation method to calculate the aerodynamic characteristics of the front elliptical wing-main wing composite control configuration under different design parameter combinations in the orthogonal table, and obtain the aerodynamic force coefficient and aerodynamic moment coefficient under different design parameter combinations in the orthogonal table. According to the obtained aerodynamic force coefficient and aerodynamic moment coefficient, identify the unknown parameters in the equation established in step 4, and obtain Expression of Step 7: Based on the result from step 6 The final state space equation physical characteristic characterization model of the front elliptical wing-main wing composite control configuration is constructed as follows: in is the internal state quantity, representing the distance from the flow separation point on the main wing upper surface to the leading edge of the main wing, for The dimensionless representation of ; is the main wing angle of attack, for The first-order rate of change of for The dimensionless form of All are time constants; is the slope factor, is the angle of attack corresponding to the separation point reaching the midpoint of the chord line of the main wing airfoil under steady state; is a constant, the partial derivative Both The unknown parameters obtained through model identification are ; The input variables of the state space equation physical property characterization model are And design parameters , the output is the aerodynamic force coefficient and aerodynamic moment coefficient .

2. The method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers according to claim 1, characterized in that: In step 1, the angle of attack of the front elliptical wing The value range is , the corresponding dimensionless parameter is , is the average angle of attack of the pitch oscillation of the composite control configuration; the horizontal distance from the center of the front elliptical wing to the leading edge of the main wing The value range is , the corresponding dimensionless parameter is , is the chord length of the main wing airfoil; The vertical distance from the center of the front elliptical wing to the leading edge of the main wing The value range is , the corresponding dimensionless parameter is .

3. The method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers according to claim 2, characterized in that: During the pitching motion of the front elliptical wing-main wing composite control configuration, the main wing performs reciprocating pitching motion around the moment center, and the front elliptical wing is relatively stationary.

4. The method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers according to claim 1, characterized in that: The equation established in step 4 is given by It consists of four parts, including The formula together constitutes a three-dimensional surface with multiple peaks in the local area. By associating elliptic equations and polynomials, Formula in will Added on an associated basis impact.

5. The method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers according to claim 4, characterized in that: The equation established in step 4 can achieve When the value of exceeds the design space, the The impact of change.

6. The method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers according to claim 1, characterized in that: In step 7, the partial derivative Expressed as a quadratic polynomial: In the formula, are constants, ;and can be identified through model identification.

7. The method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers according to claim 6, characterized in that: In step 7, The dimensionless form of , represents the characteristic time of the flow, is the free flow speed.

8. The method for modeling unsteady aerodynamic forces of a composite control configuration for high angle of attack maneuvers according to claim 6, characterized in that: In step 7, the time constant It reflects the formation process of unsteady equilibrium separation flow. It reflects the separation hysteresis characteristics of flow.

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