Model design method and unsteady aerodynamic modeling method for folded rudder supersonic wind tunnel test under large blocking condition

Abstract

The invention discloses a model design method and an unsteady aerodynamic modeling method under the condition of large blockage in a folded rudder supersonic wind tunnel test, and belongs to the technical field of wind tunnel test modeling. In order to improve the simulation precision of unsteady aerodynamic force of folding rudder unfolding, the method comprises the following steps: designing a folding rudder carrier model to be located in a test section rhombus area; designing a head shock wave angle of the folding rudder carrier model; and controlling the local flow field of the folded rudder carrier model to be close to the local flow field of the original folded rudder carrier model. According to the method, the model equivalent scaling design under the folding rudder supersonic wind tunnel test large-blocking condition can be realized, and an accurate test attitude conforming to a folding rudder assessment target is obtained by establishing a mathematical agent model for the folding rudder pneumatic rolling torque under the test condition; and the working rule of the folding rudder under the combination of different incidence angles and sideslip angles is summarized. The method solves the problem that whether an assessment target is reached or not is difficult to quickly determine under the test condition, which is extremely likely to cause test failure, and ensures higher calculation accuracy in the process.

Description

Technical Field

[0001] The invention belongs to the technical field of wind tunnel test modeling, and specifically relates to a model design method and an unsteady aerodynamic modeling method under large blockage conditions of a folded rudder supersonic wind tunnel test. Background Art

[0002] In order to save space, the tail rudder of the embedded missile is generally designed to be foldable, that is, a folding rudder. In order to test the ability of the folding rudder of the missile to unfold and lock smoothly when it is released, and to test the impact resistance of the rudder surface material, it is necessary to conduct a deployment test of the actual folding rudder. At present, the assessment methods are divided into two categories: flight test and ground loading test. Flight tests are expensive and risky, and should be avoided as much as possible; most ground loading tests use mass blocks or high-pressure gas to do work to simulate the aerodynamic force when the folding rudder is unfolded. It has the advantages of low cost, safety, and high timeliness, but the test accuracy is insufficient, resulting in a large redundant design of the actuator.

[0003] There are many applications of using wind tunnels to conduct dynamic deployment tests of folding rudders. The main problem is that it is difficult to measure the dynamic aerodynamic force of the folding rudder without destroying the rudder surface. The use of balance strain gauges to measure the dynamic aerodynamic force of the folding rudder has the shortcomings of poor signal measurement accuracy and the inability to complete the physical assessment due to the destruction of the rudder surface. At present, the more accurate method of obtaining the aerodynamic force of the folding rudder is to obtain the internal driving force distribution of the folding rudder actuator with high accuracy and basically unaffected by load changes. The ground no-load test is used to obtain the internal driving force distribution of the folding rudder, and then the deployment test with wind load is carried out in the wind tunnel. The folding rudder angle and angular velocity parameters obtained by high-speed photography technology in the test are used to solve the wind load distribution and work of the folding rudder. However, the equivalent scaling design of the folding rudder model and the unsteady aerodynamic modeling of the folding rudder test state using CFD methods have become an important part of the unsteady aerodynamic assessment of the folding rudder deployment. Summary of the invention

[0004] The problem to be solved by the present invention is to improve the simulation accuracy of the unsteady aerodynamic force of the folding rudder deployment, and propose a model design method and an unsteady aerodynamic modeling method under large blockage conditions of a folding rudder supersonic wind tunnel test.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A method for designing a model of a folding rudder supersonic wind tunnel test under large obstruction conditions comprises the following steps:

[0007] S1. Design the folding rudder carrier model to be in the diamond-shaped area of ​​the test section;

[0008] S2. Design the head shock wave angle of the folding rudder carrier model;

[0009] S3. The local flow field of the controlled folding rudder carrier model is close to the local flow field of the original folding rudder carrier model.

[0010] Furthermore, in step S1, the total length of the folding rudder carrier model is controlled to be smaller than the length of the diamond-shaped area of ​​the test section. The length calculation formula of the diamond-shaped area of ​​the test section is:

[0011]

[0012] Among them, L is the length of the diamond area, c is the safety factor, which is generally taken as 0.6, H is the height or width of the test section, and Ma is the Mach number.

[0013] Furthermore, in step S2, the head shape of the folding rudder carrier model is designed to be a conical rotating body or a streamlined elliptical cone to limit the oblique shock wave angle of the model head;

[0014] For a streamlined elliptical cone, the calculation process of the oblique shock wave angle and the deflection angle is as follows:

[0015] First, calculate the oblique shock wave angle, the calculation formula is:

[0016]

[0017] Among them, θ is the deflection angle, β is the oblique shock wave angle, and M1 is the wavefront Mach number. In aerodynamics, this formula can be plotted as a θ-β-M curve graph;

[0018] According to the Mach number formula of the oblique shock wave, the vertical Mach number and the Mach number behind the wave are obtained:

[0019]

[0020] Among them, M2 is the Mach number after the wave, γ is the specific heat ratio, which is 1.4 when air is the medium, and M n,2 is the vertical Mach number behind the wave, M n,1 is the vertical Mach number of the wavefront;

[0021] Then, based on the obtained θ and M2, the oblique shock wave angle β2 is obtained according to the θ-β-M curve, and the oblique shock wave angle Φ reflected from the cave wall is calculated relative to the surrounding cave walls. The calculation formula is:

[0022] Φ = β2 - θ;

[0023] Based on the total length of the folding rudder carrier model obtained in step S1 and the angle of the oblique shock wave reflected from the cave wall, the positional relationship between the reflected shock wave and the tail of the folding rudder carrier model in the flow direction is obtained.

[0024] Furthermore, in step S3, the folding rudder carrier model and the geometric model from the previous root chord length position to the tail are kept unchanged, so as to achieve that the flow field around the folding rudder carrier model is close to the local flow field of the original folding rudder carrier model.

[0025] A method for modeling unsteady aerodynamic forces of a folded rudder supersonic wind tunnel test model under large obstruction conditions is provided, which is based on the model under large obstruction conditions of a folded rudder supersonic wind tunnel test, and comprises the following steps:

[0026] Step 1. Assume that the folding rudder is a rigid body, and the translational motion equation of the object is as follows:

[0027]

[0028] in, is the resultant force vector, m is the mass of the folded rudder, is the acceleration vector;

[0029]

[0030] Wherein, x, y, z are the x-axis coordinates, y-axis coordinates, and z-axis coordinates of the mass center of the folding rudder in the inertial coordinate system, and t is the time;

[0031] Step 2. Design the vector expression of the 6-DOF rotational motion equation as follows:

[0032]

[0033] in, is the sum moment vector, is the angular acceleration vector, is the angular velocity vector, I is the moment of inertia vector; θ x ,θ y ,θ z are the angles of the object around the x, y, and z axes, respectively, and ω x =dθ x / dt,ω y =dθ y / dt,ω z =dθ z / dt;

[0034]

[0035] Among them, I xx ,I yy ,I zz are the moments of inertia of the folding rudder about the x, y, and z axes respectively;

[0036] Step 3. Based on the folding rudder being hinged on the rudder shaft, the 6-DOF motion is simplified to a rotational motion with the x-axis as the rotation axis, and the simplified rotational motion equation is:

[0037] M x =Ixx ·d 2 θ x / dt 2 or 2 θ x / dt 2 =M x / I xx ;

[0038] Based on M x The torque of gravity, aerodynamic force, mechanical friction, and actuator driving force is then calculated as follows: The calculation formula is:

[0039]

[0040] Among them, M G is the hinge moment due to gravity, M a is the hinge moment caused by aerodynamic force, M f is the hinge torque caused by mechanical friction, M e The hinge torque caused by the actuator driving force;

[0041] Then design the angular velocity of the folding rudder The equation is as follows:

[0042]

[0043] Folding rudder rotation angle θ x The equation is as follows:

[0044]

[0045] Step 4. Add and combine the hinge torque caused by the mechanical friction force of the folding rudder and the driving force of the actuator, which is collectively referred to as the internal driving torque. The value of the internal driving torque is measured by conducting a ground windless deployment test of the folding rudder in advance;

[0046] Step 5. After the internal driving torque is determined, CFD is used to simulate the deployment process under different flow conditions to obtain a variety of relationship samples between the deployment aerodynamic hinge torque and the deployment angle. Then, RBF modeling or polynomial modeling is established based on the relationship samples between the deployment aerodynamic hinge torque and the deployment angle to obtain the hinge torque aerodynamic model of the folding rudder.

[0047] Beneficial effects of the present invention:

[0048] The model design method for a folding rudder under large obstruction conditions in a supersonic wind tunnel test described in the present invention is designed to address the technical challenges posed to high-speed wind tunnel test technology during the development of embedded weapons. It is necessary to successfully implement the folding rudder test on schedule, reduce the expected test costs, and compress the test cycle. This method can achieve equivalent scaling design of the model under large obstruction conditions in a supersonic wind tunnel test of a folding rudder. By establishing a mathematical proxy model for the aerodynamic rolling moment of the folding rudder under test conditions, an accurate test posture that meets the folding rudder assessment target is obtained, and the working law of the folding rudder under different combinations of angles of attack and sideslip angles is summarized. Overall, this method saves project funds and ensures the successful implementation of the project.

[0049] The model design method for a folding rudder supersonic wind tunnel test under large blockage conditions described in the present invention designs a good folding rudder shape without shock wave interference under supersonic and large blockage conditions, accurately calculates the aerodynamic rolling moment of its deployment process under the test state, and then establishes a reasonable mathematical proxy model. It can effectively solve the model design problem when there is no CFD means, solve the problem that it is difficult to quickly determine whether the assessment target is achieved under test conditions, and it is very likely to cause the test failure. In this process, a high calculation accuracy is guaranteed, and the difference between the proxy model and the final test result is guaranteed to be within 10%. This method is a pilot verification method that has been tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the typical folding rudder distribution and carrier described in the present invention;

[0051] Figure 2 It is the design of the folding rudder aerodynamic assessment process and the link diagram of the invention in the red frame;

[0052] Figure 3 It is a schematic diagram of the model scaling design described in the present invention;

[0053] Figure 4 is a schematic diagram of the unfolding of the folding rudder described in the present invention;

[0054] Figure 5 It is a schematic diagram of the aerodynamic rolling moment of the RBF fitting single folding rudder deployment process described in the present invention;

[0055] Figure 6 It is a schematic diagram of the change of aerodynamic rolling moment with the deployment angle and angular velocity during the folding rudder deployment process according to the RBF modeling fitting described in the present invention;

[0056] Figure 7 It is a schematic diagram of the polynomial modeling and fitting of the aerodynamic rolling moment during the folding rudder deployment process as a function of the deployment angle, angle of attack, and sideslip angle described in the present invention;

[0057] Figure 8is a comparison diagram of the aerodynamic rolling moment distribution estimated by the aerodynamic model described in the present invention and the test results;

[0058] Fig. 9 is a graph showing the change in the angle of attack of the aerodynamic rolling moment hindering the work done as estimated by the aerodynamic model described in the present invention;

[0059] Fig.10 It is a diagram showing the change in angle of attack of the aerodynamic rolling moment promoting work predicted by the aerodynamic model described in the present invention. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0061] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0062] In order to further understand the content, features and effects of the present invention, the following specific implementation methods are given as examples, and the attached Figure 1 -Attached Fig.10 The detailed instructions are as follows:

[0063] Embodiment 1:

[0064] A method for designing a model of a folding rudder supersonic wind tunnel test under large obstruction conditions comprises the following steps:

[0065] S1. Design the folding rudder carrier model to be in the diamond-shaped area of ​​the test section;

[0066] Furthermore, in step S1, the total length of the folding rudder carrier model is controlled to be smaller than the length of the diamond-shaped area of ​​the test section. The length calculation formula of the diamond-shaped area of ​​the test section is:

[0067]

[0068] Where L is the length of the diamond area, c is the safety factor, which is generally taken as 0.6, H is the height or width of the test section, and Ma is the Mach number;

[0069] Furthermore, when the wind tunnel is 1.6 meters and the wind tunnel width is 1.5 meters, 1.5 meters is taken to estimate the model length. If the Mach number is 1.5, the calculated L is approximately 1.006 meters.

[0070] S2. Design the head shock wave angle of the folding rudder carrier model;

[0071] Furthermore, in step S2, the head shape of the folding rudder carrier model is designed to be a conical rotating body or a streamlined elliptical cone to limit the oblique shock wave angle of the model head;

[0072] For a streamlined elliptical cone, the calculation process of the oblique shock wave angle and the deflection angle is as follows:

[0073] First, calculate the oblique shock wave angle, the calculation formula is:

[0074]

[0075] Among them, θ is the deflection angle, β is the oblique shock wave angle, and M1 is the wavefront Mach number. In aerodynamics, this formula can be plotted as a θ-β-M curve graph;

[0076] According to the Mach number formula of the oblique shock wave, the vertical Mach number and the Mach number behind the wave are obtained:

[0077]

[0078] Among them, M2 is the Mach number after the wave, γ is the specific heat ratio, which is 1.4 when air is the medium, and M n,2 is the vertical Mach number behind the wave, M n,1 is the vertical Mach number of the wavefront;

[0079] Then, based on the obtained θ and M2, the oblique shock wave angle β2 is obtained according to the θ-β-M curve, and the oblique shock wave angle Φ reflected from the cave wall is calculated relative to the surrounding cave walls. The calculation formula is:

[0080] Φ=β2-θ

[0081] Based on the total length of the folding rudder carrier model obtained in step S1 and the angle of the oblique shock wave reflected from the cave wall, the position relationship between the reflected shock wave and the tail of the folding rudder carrier model in the flow direction is obtained;

[0082] Furthermore, when the model is a two-dimensional wedge-shaped body, θ is the half angle of the wedge-shaped body, that is, half of the full angle of the wedge-shaped body, and the angle of the head oblique shock wave generated is limited to within about 45° as much as possible to reduce the influence of the head oblique shock wave and its reflected shock wave.

[0083] For wedge-shaped bodies;

[0084] The above method is to solve the shape of the reflected shock wave of the wedge-shaped body in the wind tunnel. However, in the three-dimensional test, the shape of the model after streamlined design is close to a cone or an elliptical cone. The farther away from the model surface, the smaller the shock wave angle. Therefore, its shock wave angle is smaller than the shock wave angle of the wedge-shaped body, and the uniform flow field area in the shock wave is longer, and the possibility of interference with the tail of the model is weaker. In order to avoid shock wave interference as much as possible in the design, theoretical calculations should be performed first based on the shape of the wedge-shaped body, and then the calculated wedge-shaped body half angle should be used as the cone angle of the model head.

[0085] When establishing the geometric shape of the model head, it is necessary to establish a series of smooth bridging curves from the model head tip to the model tail. The curve form is NURBS curve (non-uniform rational B-spline curve). NURBS curves ensure smooth transitions between the bridging curve and other curves to meet the requirements for curve smoothness and continuity in the design. If the model head is designed as a rotational body, only one NURBS curve needs to be established. If it is an elliptical cone, the model head half mold can be designed first. The establishment of the half mold part requires selecting at least 4 points on the edge of the half mold on the bottom surface of the elliptical cone, and establishing smooth bridging curves with these points with the model head tip as the starting point, and then establishing a smooth surface in the form of a filled form or a multi-section surface.

[0086] S3. The local flow field of the controlled folding rudder carrier model is close to the local flow field of the original folding rudder carrier model.

[0087] Furthermore, in step S3, the folding rudder carrier model and the geometric model from the previous root chord length position to the tail are kept unchanged, so as to achieve that the flow field around the folding rudder carrier model is close to the local flow field of the original folding rudder carrier model.

[0088] Furthermore, a preliminary model is designed based on the implementation of the above three design requirements. The flow field near the folding rudder of the original shape and the test model is compared through CFD calculation. When the maximum difference in the surface pressure coefficient distribution of the rudder surface is within 10%, the model design is considered qualified. If the difference is greater than 10%, the model length is further reduced and the head cone angle is adjusted to obtain a shape that meets the surface pressure error requirements. However, it should also be avoided to reduce the model length excessively, which will cause the head shock wave to directly scan the folding rudder surface. The most obvious feature of the above method is to control the total length of the model, the head shaping, and retain the shape of the carrier around the folding rudder to ensure the similarity of the flow field around the folding rudder before and after the model scaling design.

[0089] Embodiment 2:

[0090] A method for modeling unsteady aerodynamic force of a folded rudder supersonic wind tunnel test model under large obstruction conditions is implemented based on the model under large obstruction conditions of a folded rudder supersonic wind tunnel test described in Example 1, and includes the following steps:

[0091] Step 1. Assume that the folding rudder is a rigid body, and the translational motion equation of the object is as follows:

[0092]

[0093] in, is the resultant force vector, m is the mass of the folded rudder, is the acceleration vector;

[0094]

[0095] Wherein, x, y, z are the x-axis coordinates, y-axis coordinates, and z-axis coordinates of the mass center of the folding rudder in the inertial coordinate system, and t is the time;

[0096] Step 2. Design the vector expression of the 6-DOF rotational motion equation as follows:

[0097]

[0098] in, is the sum moment vector, is the angular acceleration vector, is the angular velocity vector, I is ***; θ x ,θ y ,θ z are the angles of the object around the x, y, and z axes, respectively, and ω x =dθ x / dt,ω y =dθ y / dt,ω z =dθ z / dt;

[0099]

[0100] Among them, I xx ,I yy ,I zz are the moments of inertia of the folding rudder about the x, y, and z axes respectively;

[0101] Step 3. Based on the folding rudder being hinged on the rudder shaft, the 6-DOF motion is simplified to a rotational motion with the x-axis as the rotation axis, and the simplified rotational motion equation is:

[0102] M x =I xx ·d 2 θ x / dt 2 or 2 θ x / dt 2 =M x / Ixx ;

[0103] Based on M x The torque of gravity, aerodynamic force, mechanical friction, and actuator driving force is then calculated as follows: The calculation formula is:

[0104]

[0105] Among them, M G is the hinge moment due to gravity, M a is the hinge moment caused by aerodynamic force, M f is the hinge torque caused by mechanical friction, M e The hinge torque caused by the actuator driving force;

[0106] Then design the angular velocity of the folding rudder The equation is as follows:

[0107]

[0108] Folding rudder rotation angle θ x The equation is as follows:

[0109]

[0110] Furthermore, the hinge torque caused by the mechanical friction of the folding rudder and the driving force of the actuator can be numerically added and combined, collectively referred to as the internal driving torque. The determination of its value requires the ground windless deployment test of the folding rudder to be measured in advance. The ground windless deployment test is a test method that uses gas as a power source to establish a set of load application mechanisms on the folding rudder surface that unfolds with the rudder surface to obtain the internal driving torque law of the folding rudder mechanism. In the ground test of the folding rudder actuator, when the actuator is driven by a torsion spring, its internal driving torque is easier to determine. When the actuator is driven by a fire control product, its internal driving torque is more difficult to determine and is affected by the movement speed. It is necessary to obtain several samples after multiple tests and then obtain it through mathematical modeling.

[0111] Step 4. Add and combine the hinge torque caused by the mechanical friction force of the folding rudder and the driving force of the actuator, which is collectively referred to as the internal driving torque. The value of the internal driving torque is measured by conducting a ground windless deployment test of the folding rudder in advance;

[0112] Step 5. After the internal driving torque is determined, CFD is used to simulate the deployment process under different flow conditions to obtain a variety of relationship samples between the deployment aerodynamic hinge torque and the deployment angle. Then, RBF modeling or polynomial modeling is established based on the relationship samples between the deployment aerodynamic hinge torque and the deployment angle to obtain the hinge torque aerodynamic model of the folding rudder.

[0113] The specific implementation process of this embodiment is as follows:

[0114] (1) Confirm the input conditions:

[0115] Before establishing the model scaling design and unsteady aerodynamic modeling work under large blockage conditions for folded rudder supersonic wind tunnel tests, the following inputs are required:

[0116] 1. Assessment target: After obtaining clear assessment targets for the folding rudder, the assessment targets are divided into two categories: the hindering end and the promoting end. The initial torque and total work energy of the assessment targets are the key quantities.

[0117] 2. Test conditions: Based on the flight altitude and speed of the carrier aircraft when the folding rudder is detached from the carrier aircraft, the dynamic pressure and Mach number of the carrier aircraft are calculated. This dynamic pressure and Mach number are the dynamic pressure and Mach number of the test, which also determine the wind tunnel test conditions.

[0118] 3. Folding rudder mechanism: The distribution of the driving torque provided by the overall folding rudder with the deployment angle. Rudder surface structure mass parameters, including the mass of the folding rudder and the moment of inertia about the axis of rotation.

[0119] 4. Folding rudder deployment time: After the assessment target and folding rudder mechanism information in the above input are determined, the deployment time magnitude of the folding rudder under different assessment targets should also be basically clarified. Generally, the folding rudder deployment time is about 20ms to 200ms. It can be considered that 20ms is a faster deployment, while 200ms is a slower deployment. The different deployment time has a significant impact on the strength of the dynamic aerodynamic force increment of the folding rudder. Based on this, the approximate range of the angle of attack and sideslip angle combination can be determined in the calculation.

[0120] (2) Model scaling design:

[0121] When the input conditions are confirmed, the model is scaled down according to the input conditions. The scaled down is carried out according to three principles: ensure that the model is in the diamond area of ​​the test section, streamline the head of the model to reasonably control the head shock wave, and keep the shape near the folded rudder unchanged so that the local flow field is close to the original shape. The model scaling design results are shown in the attached figure. Figure 3 shown.

[0122] (3) Unsteady aerodynamic modeling of folding rudder:

[0123] During the unsteady deployment of the folding rudder, the main concern is the aerodynamic rolling moment of the rudder surface. Therefore, it is necessary to first establish a complete simulation method for simulating the dynamic deployment of the folding rudder in a supersonic wind tunnel, which requires the accuracy of the real response to the deployment process of the rudder surface and the unsteady aerodynamic force. The single-degree-of-freedom aerodynamic motion equation of the rudder surface deployment is established to simulate the motion process. The motion equation includes gravity, aerodynamic force, mechanical friction force, and actuator drive force during the deployment of the folding rudder, including the mass of the folding rudder and the moment of inertia about the rotating shaft. Among them, the mechanical friction force of the folding rudder and the actuator drive force can be combined and collectively referred to as the internal driving force. The determination of its value needs to refer to the design indicators of the folding rudder actuator and the results of the windless deployment test. When the actuator is driven by a torsion spring, its driving torque is easier to determine using a ground windless test. When the actuator is driven by a fire control product, its driving torque is more difficult to determine and has a more obvious interaction with the deployment speed, and it needs to be obtained after multiple ground load tests. At this time, the distribution results of driving torque with different loads are obtained. For different assessment targets, the driving torque results should be clarified. For example, the driving torque of the folding rudder during obstruction should be different from the driving torque during promotion.

[0124] CFD is used to calculate the unsteady motion process of the single degree of freedom of the folding rudder. The CFD simulation process is set up as follows:

[0125] The URANS or DES method is used, and the fluid medium is a compressible ideal gas. The spatial discretization uses the finite volume method based on the grid center format, and the time advancement uses the multi-level Runge-Kutta explicit time advancement. The results of each physical time step are obtained by double time advancement. Multiple grids and dynamic CFL number adjustment are used to accelerate the calculation convergence. The folded rudder rotates relative to the carrier, and the area near the rudder surface is nested in the carrier background domain as a subdomain. The computational grid uses a three-dimensional prism layer and a tetrahedral hybrid unstructured grid, which is divided into two parts: the carrier background domain and the folded rudder subdomain. The nested boundary interpolation accuracy is 2nd order. The subdomain and background domain grids need to be verified by grid independence to ensure reasonable density and distribution, especially in the space where the head shock wave and the reflected shock wave are located, and a dense grid should be maintained. The grid near the folded rudder surface should be denser. There is a certain gap between the dynamic rudder surface and the static rudder surface due to the nesting. This gap generally does not exceed 5mm. At present, in most cases, the gap between the static rudder and the dynamic rudder is kept at 2mm. After the folded rudder is displaced to a new position in each physical time step, it is re-nested to obtain the solution grid, and the time step convergence analysis is performed at 1 / 10 to 1 / 200 of the dimensionless unsteady physical time step. At the same time, the angle swept by the tip of the rudder surface in each physical time step should be considered, and this angle should be kept within 1° as much as possible, or even increased to within 0.5°.

[0126] By applying the CFD method several times to simulate the deployment process of the folding rudder in the wind tunnel, the aerodynamic samples of the folding rudder under test conditions are obtained. Check whether the aerodynamic rolling moment distribution and energy in the sample cover the assessment target, and whether its distribution trend is close to the rolling moment distribution of the assessment target. If it deviates from the assessment target distribution, the angle of attack and sideslip angle of the model should be modified, so that the sample results finally cover the assessment target and the distribution trend is close. After the calculation of multiple groups of angle of attack and sideslip angle samples, the aerodynamic rolling moment proxy model is established using RBF function or fourth-order polynomial. The independent variables of the model are the deployment angle of the folding rudder, the deployment angular velocity, the carrier angle of attack, and the carrier sideslip angle, and the dependent variable is the aerodynamic rolling moment of the folding rudder dynamic control surface. The aerodynamic rolling moment distribution of single deployment and multiple deployment processes established by RBF correspondence is shown in the attached figure. Figure 6 , Attachment Figure 7 The mathematical proxy model established by polynomial modeling and the aerodynamic rolling moment distribution calculated by CFD are shown in the attached figure. Figure 8 As shown, it can be seen that both have good fitting characteristics.

[0127] (4) Agent model assessment

[0128] The present invention selects RBF function (RBF function formula is basically known, and the Gaussian function form thereof is used here) or 4th order polynomial to establish aerodynamic rolling moment proxy model according to different situations. When the value of the internal driving torque at each deployment angle does not change with the change of the external aerodynamic force, the 4th order polynomial is selected to establish the aerodynamic rolling moment proxy model, and vice versa, the RBF function is used. The independent variables of the 4th order polynomial are the angle of attack, the sideslip angle, the deployment angle, and the deployment angular velocity, and the dependent variable is the aerodynamic hinge torque.

[0129] Set the aerodynamic work as the assessment target, calculate the root mean square deviation of the aerodynamic hinge torque of the "assessment target-aerodynamic model" at the same deployment angle, use the genetic algorithm for optimization iteration, and select the state corresponding to the minimum deviation, that is, to obtain the optimal angle of attack and sideslip angle combination. Figure 2 After the wind tunnel test was carried out according to the process shown in the figure, the comparison results between the test and the aerodynamic model were obtained, as shown in the attached figure. Figure 8 As shown, the aerodynamic proxy model accurately predicts the model aerodynamic force distribution and the final total energy during the test. The optimal total energy error is less than 4%, and in general it can be within 10%, showing the high accuracy of the aerodynamic proxy model.

[0130] (5) Distribution of work energy

[0131] In recent years, statistics on the calculation and test results of different folding rudders have shown that the total energy of the aerodynamic rolling torque during the deployment of the folding rudder changes with the angle of attack or sideslip angle in a nearly linear relationship, and its slope is related to parameters such as the rudder surface area, the incoming flow Mach number, and the dynamic pressure. A typical example is shown in the attached figure. Fig. 9 , Attachment Fig.10 As shown, the aerodynamic rolling moment of the folding rudder during the deployment process both hinders the work and promotes the work and presents an approximately linear inertia with the angle of attack.

[0132] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0133] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for designing a model under large obstruction conditions for a folding rudder supersonic wind tunnel test, characterized in that: The steps include: S1. Design the folding rudder carrier model to be in the diamond-shaped area of ​​the test section; S2. Design the head shock wave angle of the folding rudder carrier model; S3. The local flow field of the controlled folding rudder carrier model is close to the local flow field of the original folding rudder carrier model.

2. The method for designing a model under large obstruction conditions for a folded rudder supersonic wind tunnel test according to claim 1, characterized in that: Step S1 controls the total length of the folding rudder carrier model to be less than the length of the diamond-shaped area of ​​the test section. The length calculation formula of the diamond-shaped area of ​​the test section is: Among them, L is the length of the diamond area, c is the safety factor, which is generally taken as 0.6, H is the height or width of the test section, and Ma is the Mach number.

3. The method for designing a model under large obstruction conditions for a folded rudder supersonic wind tunnel test according to claim 2, characterized in that: Step S2: the head shape of the folding rudder carrier model is designed to be a conical rotating body or a streamlined elliptical cone to limit the oblique shock wave angle of the model head; For a streamlined elliptical cone, the calculation process of the oblique shock wave angle and the deflection angle is as follows: First, calculate the oblique shock wave angle, the calculation formula is: Among them, θ is the deflection angle, β is the oblique shock wave angle, and M1 is the wavefront Mach number. In aerodynamics, this formula can be plotted as a θ-β-M curve graph; According to the Mach number formula of the oblique shock wave, the vertical Mach number and the Mach number behind the wave are obtained: Among them, M2 is the Mach number after the wave, γ is the specific heat ratio, which is 1.4 when air is the medium, and M n,2 is the vertical Mach number behind the wave, M n,1 is the vertical Mach number of the wavefront; Then, based on the obtained θ and M2, the oblique shock wave angle β2 is obtained according to the θ-β-M curve, and the oblique shock wave angle Φ reflected from the cave wall is calculated relative to the surrounding cave walls. The calculation formula is: Φ=β2-θ Based on the total length of the folding rudder carrier model obtained in step S1 and the angle of the oblique shock wave reflected from the cave wall, the positional relationship between the reflected shock wave and the tail of the folding rudder carrier model in the flow direction is obtained.

4. The method for designing a model of a folded rudder under large obstruction conditions for supersonic wind tunnel testing according to claim 3, characterized in that: In step S3, the folding rudder carrier model and the geometric model from the previous root chord length position to the tail are kept unchanged, so as to achieve that the flow field around the folding rudder carrier model is close to the local flow field of the original folding rudder carrier model.

5. A method for modeling unsteady aerodynamic forces of a folded rudder supersonic wind tunnel test model under large blockage conditions, based on the model of a folded rudder supersonic wind tunnel test model under large blockage conditions as claimed in any one of claims 1 to 4, characterized in that: The steps include: Step 1. Assume that the folding rudder is a rigid body, and the translational motion equation of the object is as follows: in, is the resultant force vector, m is the mass of the folded rudder, is the acceleration vector; Wherein, x, y, z are the x-axis coordinates, y-axis coordinates, and z-axis coordinates of the mass center of the folding rudder in the inertial coordinate system, and t is the time; Step 2. Design the vector expression of the 6-DOF rotational motion equation as follows: in, is the sum moment vector, is the angular acceleration vector, is the angular velocity vector, I is ***; θ x ,θ y ,θ z are the angles of the object around the x, y, and z axes, respectively, and ω x =dθ x / dt,ω y =dθ y / dt,ω z =dθ z / dt; Among them, I xx ,I yy ,I zz are the moments of inertia of the folding rudder about the x, y, and z axes respectively; Step 3. Based on the folding rudder being hinged on the rudder shaft, the 6-DOF motion is simplified to a rotational motion with the x-axis as the rotation axis, and the simplified rotational motion equation is: M x = I xx · d 2 θ x / dt 2 or d 2 θ x / dt 2 = M x / I xx ; Based on M x The torque of gravity, aerodynamic force, mechanical friction, and actuator driving force is then calculated as follows: The calculation formula is: Among them, M G is the hinge moment due to gravity, M a is the hinge moment caused by aerodynamic force, M f is the hinge torque caused by mechanical friction, M e The hinge torque caused by the actuator driving force; Then design the angular velocity of the folding rudder The equation is as follows: Folding rudder rotation angle θ x The equation is as follows: Step 4. Add and combine the hinge torque caused by the mechanical friction force of the folding rudder and the driving force of the actuator, which is collectively referred to as the internal driving torque. The value of the internal driving torque is measured by conducting a ground windless deployment test of the folding rudder in advance; Step 5. After the internal driving torque is determined, CFD is used to simulate the deployment process under different flow conditions to obtain a variety of relationship samples between the deployment aerodynamic hinge torque and the deployment angle. Then, RBF modeling or polynomial modeling is established based on the relationship samples between the deployment aerodynamic hinge torque and the deployment angle to obtain the hinge torque aerodynamic model of the folding rudder.

Images