Wind tunnel test model construction method for waviness and order difference verification

Abstract

The invention belongs to the technical field of aircraft design, and particularly relates to a wind tunnel test model construction method for waviness and jump verification, which comprises the following steps: firstly, determining the size limit of a test model, independently designing the shape of the wind tunnel test model according to two aspects of a flat plate and a disc part, and according to the test pressure measurement requirement, determining the size limit; arranging pressure measuring points at specific positions on a flat plate and a disc profile of the designed test model, then determining a supporting mode, judging whether the whole test model meets the size limitation of the test model or not after the design is completed, and if yes, completing the design. According to the airworthiness review requirements of the aircraft RVSM, on the premise that the aircraft appearance cannot be directly tested in equal proportion, a test model is designed by combining the surface skin characteristics of the key area of the aircraft RVSM and the mounting requirements of a static pressure sensor to measure the influence of microscales such as waviness and jump on pressure; and an effective support is provided for RVSM airworthiness review verification of the reliability of the CFD method in simulation of micro-scale influences such as waviness and order difference.

Description

Technical Field

[0001] The present application belongs to the technical field of aircraft design, and in particular relates to a method for constructing a wind tunnel test model for corrugation and step difference verification. Background Art

[0002] When an aircraft operates in RVSM airspace, the error of its altitude measurement system must meet the requirements specified in Advisory Circular AC-21-13 (Aircraft Airworthiness Approval for Operation with 300 m (1000 ft) Vertical Separation Standard in RVSM Airspace). The static pressure measured by the aircraft static pressure source is related to the flight altitude. In RVSM airworthiness, a critical area is defined near the aircraft static pressure source. Factors such as skin surface corrugation and static pressure sensor installation step difference in this critical area are important sources of altitude measurement system error. In order to obtain the influence of corrugation, step difference, etc. on the aircraft static pressure measurement, the CFD method is usually used to analyze the aircraft body, and the reliability of the CFD method needs to be verified by experiment before it can be recognized by the authority.

[0003] Due to the limited size of the test wind tunnel, it is impossible to conduct a wind tunnel test on the aircraft shape at a 1:1 ratio; furthermore, the waviness and step difference are small variables. If the wind tunnel size is reduced, the characteristics of variables such as waviness and step difference cannot be reflected, and satisfactory test results cannot be obtained. Designing a wind tunnel test model and verifying it with the CFD method and wind tunnel test to obtain the error accuracy of the CFD method has become one of the methods to indirectly express airworthiness compliance.

[0004] In order to obtain the influence of tiny scales such as corrugation and step difference on pressure measurement, it is necessary to design and construct a sophisticated pressure measurement test model to ensure that the test purpose is achieved. Summary of the invention

[0005] The purpose of this application is to provide a method for constructing a wind tunnel test model for corrugation and step difference verification, so as to solve the problem that variable characteristics such as corrugation and step difference cannot be reflected in existing wind tunnel tests.

[0006] The technical solution of the present application is: a method for constructing a wind tunnel test model for corrugation and step difference verification, comprising:

[0007] Select wind tunnel equipment that meets the measurement requirements based on the test measurement accuracy requirements;

[0008] The selected wind tunnel equipment is used as the target wind tunnel, and the size limit of the test model is determined according to the size of the target wind tunnel;

[0009] According to the size limit of the test model, the shape of the wind tunnel test model is designed separately in terms of the flat plate and the disc part, and the flat plate and disc surface shapes are determined;

[0010] According to the test pressure measurement requirements, pressure measurement points are arranged at specific locations on the designed test model flat plate and disc surface to complete the preliminary design of the test model;

[0011] Obtain the installation and assembly requirements in the target wind tunnel and determine the support method of the current test model; carry out the overall structural design of the test model under the current support method. After the design is completed, determine whether the entire test model meets the test model size limit. If so, complete the design; if not, redesign until the test model size limit is met;

[0012] Determine the processing and testing requirements of the test model based on the designed test model, and obtain the structural processing design plan;

[0013] The test model is processed according to the structural processing design plan.

[0014] Preferably, the measurement accuracy requirement uses a CFD method to evaluate the difference in effect of a small change in the target variable on pressure, and the measurement accuracy requirement for the wind tunnel test is determined based on the difference in effect on pressure.

[0015] Preferably, the test model adopts a flat plate and a circular disk, and the design of the corrugation and step difference characteristics is constructed on the circular disk.

[0016] Preferably, the wind tunnel equipment is a continuous wind tunnel, and its pressure measurement accuracy and repeatability reach ±0.0015.

[0017] Preferably, the ratio of the maximum cross-sectional area of ​​the designed test model to the cross-sectional area of ​​the target wind tunnel test section is 1%.

[0018] Preferably, the flat plate profile is designed as follows: using a CFD method to simulate the flat plate shape, finding a relatively uniform area of ​​pressure distribution, and determining the position as the selected position of the disk.

[0019] Preferably, the disc profile is designed as follows: using CFD method to simulate the shape of the flat plate, according to the pressure distribution law under different shapes of the leading edge and trailing edge of the flat plate, the shape with the smallest influence on the pressure at the selected position of the disc is selected as the leading edge and trailing edge shape of the flat plate.

[0020] Preferably, the front edge of the flat plate adopts a semi-elliptical shape, and the pressure coefficient Cp in the plane where the disk is located has a variation range of less than 0.0015.

[0021] Preferably, the disc is divided into two parts, an inner circle and an outer circle, the inner and outer circles are processed integrally, the outer circle is connected to the flat plate, and the corrugation and step difference profile are constructed on the inner circle.

[0022] Preferably, the pressure measuring points are arranged at specific positions as follows: two rows of pressure measuring points are arranged on the flat plate, and the pressure measuring points on the disc are distributed in a "M" shape.

[0023] Preferably, the supporting method is specifically designed as follows: in combination with the opening conditions of the wind tunnel floor, 6 pillars are used for support, the pillar profile adopts a thin plane plus an elliptical modification of the front and rear edges, and grooves are provided inside the pillars. The pressure measuring pipelines of the disc and the plate are led out of the wind tunnel floor to the pressure measuring instrument or the pressure scanning valve through the grooves in the pillars.

[0024] Preferably, the processing and testing requirements of the test model are as follows: the pressure measuring hole opening diameter Φ=0.3mm, the corrugation profile tolerance is ±0.05mm, the step difference plane tolerance is ±0.03mm, and the outer circle gap tolerance between the disk and the plate is ±0.20mm; the upper surface roughness of the disk and the plate Ra≤0.4μm, and the surface roughness of the mating surfaces of each component Ra≤1.6μm; there is no reverse step difference in the assembly of parts, and the forward step difference does not exceed 0.05mm.

[0025] The wind tunnel test model construction method for corrugation and step difference verification in this application starts from the aircraft RVSM airworthiness review requirements. Under the premise that it is impossible to directly conduct tests on the aircraft shape in proportion, combined with the surface skin characteristics of the aircraft RVSM key area and the static pressure sensor installation requirements, the test model is designed to measure the influence of micro-scales such as corrugation and step difference on pressure, which provides effective support for the RVSM airworthiness review to verify the reliability of the CFD method in simulating micro-scale influences such as corrugation and step difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0027] Figure 1 This is a schematic diagram of the overall process of this application. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] A method for constructing a wind tunnel test model for corrugation and step difference verification, such as Figure 1 As shown, the following steps are included:

[0030] Step 1: Plan the initial test plan and clarify the test measurement accuracy requirements.

[0031] The initial test plan included the design of the test model. In order to meet the airworthiness review requirements, the test model used a flat plate plus a disc, and the corrugation and step difference characteristics were designed on the disc.

[0032] The measurement accuracy requirement is preferably determined by using the CFD method to evaluate the impact of small changes in target variables such as waviness and step difference on pressure, and the measurement accuracy requirement for the wind tunnel test is determined based on the impact of pressure.

[0033] For example: The pressure values ​​of different corrugations and waveforms evaluated by the CFD method are shown in the following table. The measurement accuracy of the wind tunnel test should be able to capture the differences in the impact of different variables.

[0034] Table of the influence of different corrugations and different waveform pressures

[0035] Waviness Arc Spline Difference 0.0015 -0.0071 -0.0097 0.0026 0.0025 -0.0119 -0.0163 0.0044 0.005 -0.0239 -0.0328 0.0089

[0036] Step 2: Select wind tunnel equipment that meets the measurement requirements based on the test measurement accuracy requirements;

[0037] As a specific implementation method, the wind tunnel equipment finally selected is a continuous wind tunnel, and its pressure measurement accuracy (Cp) and repeatability during the same period reach ±0.0015.

[0038] Step 3: Take the selected wind tunnel equipment as the target wind tunnel and determine the size limit of the test model according to the target wind tunnel size;

[0039] As a specific implementation, the ratio (blockage degree) of the maximum cross-sectional area of ​​the designed test model (including support) to the cross-sectional area of ​​the target wind tunnel test section is about 1%.

[0040] Step 4: Design the flat plate and disc surface shapes of the test model according to the size limit of the test model. Specifically, design the shape of the wind tunnel test model separately according to the flat plate and disc parts, and determine the flat plate and disc surface shapes.

[0041] As a specific implementation method, the flat plate surface is designed as follows: the CFD method is used to simulate the shape of the flat plate, and the area where the pressure distribution changes relatively evenly is found, and the position is determined as the selected position of the disc; the disc surface is designed as follows: the CFD method is used to simulate the shape of the flat plate, and according to the pressure distribution law under different shapes of the leading edge and trailing edge of the flat plate, the shape with the least influence on the pressure at the selected position of the disc is selected as the shape of the leading edge and trailing edge of the flat plate.

[0042] The leading edge of the flat plate can be in the shape of a symmetrical airfoil, a semi-ellipse, etc., and can be tangent to the equal-valued section of the flat plate. Preferably, the leading edge of the flat plate is in the shape of a semi-ellipse, and the pressure coefficient Cp in the plane where the disk is located varies within 0.0015.

[0043] Preferably, the disc is divided into two parts, an inner circle and an outer circle, the inner and outer circles are processed as one, the outer circle is connected to the flat plate, and the corrugation and step difference profile are constructed on the inner circle.

[0044] Step 5: According to the test pressure measurement requirements, arrange pressure measurement points at specific locations on the designed test model flat plate and disc surface to complete the preliminary design of the test model;

[0045] As a specific implementation method, during the test, the flat plate is fixed and only the state of the disc is changed. Two rows of pressure measuring points are arranged on the flat plate to monitor repeatability. The pressure measuring points on the disc are distributed in a "M" shape to measure the pressure at different characteristic positions and monitor symmetry at the same time.

[0046] Step 6: Obtain the installation and assembly requirements in the target wind tunnel and determine the support method for the current test model.

[0047] As a specific implementation method, the support method is combined with the opening conditions of the wind tunnel floor and adopts 6 pillars for support. The pillar profile adopts a thin plane plus an elliptical modification of the front and rear edges. A groove is provided inside the pillar. The pressure measuring pipelines of the disc and the plate are led out of the wind tunnel floor to the pressure measuring instrument or pressure scanning valve through the grooves in the pillar.

[0048] Step 7: Under the current support mode, carry out the overall structural design of the test model. After the design is completed, determine whether the entire test model meets the test model size limit. If so, complete the design; if not, redesign until the test model size limit is met.

[0049] Step 8: Determine the processing and testing requirements of the test model based on the designed test model, and obtain the structural processing design plan;

[0050] As a specific implementation method, the processing and testing requirements of the test model are as follows: the diameter of the pressure measuring hole is Φ = 0.3mm, the corrugation profile tolerance is ±0.05mm, the step difference plane tolerance is ±0.03mm, and the outer circle gap tolerance between the disc and the plate is ±0.20mm. The upper surface roughness of the disc and the plate is Ra≤0.4μm, and the surface roughness of the mating surface of each component is Ra≤1.6μm. There is no reverse step difference in the assembly of parts, and the forward step difference does not exceed 0.05mm; each test piece needs to be marked.

[0051] Step 9: Process the test model according to the structural processing design plan.

[0052] In summary, this application starts from the needs of aircraft RVSM airworthiness review. Under the premise that it is impossible to directly conduct tests on the aircraft shape in proportion, combined with the surface skin characteristics of the aircraft RVSM key areas and the installation requirements of static pressure sensors, a test model is designed to measure the influence of micro-scales such as corrugation and step difference on pressure, which provides effective support for RVSM airworthiness review to verify the reliability of CFD methods in simulating micro-scale influences such as corrugation and step difference.

[0053] Finally, it should be noted that: the drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0054] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing a wind tunnel test model for corrugation and step difference verification, characterized in that: include: Select wind tunnel equipment that meets the measurement requirements based on the test measurement accuracy requirements; The selected wind tunnel equipment is used as the target wind tunnel, and the size limit of the test model is determined according to the target wind tunnel size; According to the size limit of the test model, the shape of the wind tunnel test model is designed separately in terms of the flat plate and the disc part, and the flat plate and disc surface shapes are determined; According to the test pressure measurement requirements, pressure measurement points are arranged at specific locations on the designed test model flat plate and disc surface to complete the preliminary design of the test model; Obtain the installation and assembly requirements in the target wind tunnel and determine the support method for the current test model; Under the current support mode, the overall structural design of the test model is carried out. After the design is completed, it is determined whether the entire test model meets the size limit of the test model. If so, the design is completed. If not, the design is re-performed until the size limit of the test model is met. Determine the processing and testing requirements of the test model based on the designed test model, and obtain the structural processing design plan; The test model is processed according to the structural processing design plan.

2. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The measurement accuracy requirement adopts the CFD method to evaluate the impact difference of a small change of the target variable on the pressure, and the wind tunnel test measurement accuracy requirement is determined according to the impact difference of the pressure.

3. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The test model adopts a flat plate and a circular disk, and the design of the corrugation and step difference characteristics is constructed on the circular disk.

4. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The wind tunnel equipment is a continuous wind tunnel, and its pressure measurement accuracy and repeatability reach ±0.0015.

5. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The ratio of the maximum cross-sectional area of ​​the designed test model to the cross-sectional area of ​​the target wind tunnel test section is 1%.

6. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The flat plate profile is designed as follows: the CFD method is used to simulate the flat plate shape, to find a relatively uniform pressure distribution area, and to determine the position as the selected position of the disk.

7. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The disc profile is designed as follows: a CFD method is used to simulate the shape of a flat plate, and according to the pressure distribution law under different shapes of the leading edge and trailing edge of the flat plate, a shape with a small influence on the pressure at the selected position of the disc is selected as the shape of the leading edge and trailing edge of the flat plate.

8. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The front edge of the flat plate adopts a semi-elliptical shape, and the variation range of the pressure coefficient Cp within the plane range where the disk is located is within 0.0015.

9. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The disc is divided into two parts, an inner circle and an outer circle. The inner and outer circles are processed in one piece. The outer circle is connected to the flat plate, and the corrugation and step difference profile are constructed on the inner circle.

10. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The specific arrangement of the pressure measuring points at the specific positions is as follows: two rows of pressure measuring points are arranged on the flat plate, and the pressure measuring points on the disc are distributed in a "M" shape.

11. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The support method is specifically designed as follows: in combination with the opening conditions of the wind tunnel floor, 6 pillars are used for support, the pillar profile adopts a thin plane plus an elliptical modification of the front and rear edges, and grooves are provided inside the pillars. The pressure measuring pipelines of the disc and the plate are led out of the wind tunnel floor to the pressure measuring instrument or the pressure scanning valve through the grooves in the pillars.

12. The method for constructing a wind tunnel test model for corrugation and step difference verification according to claim 1, characterized in that: The processing and testing requirements of the test model are as follows: the pressure measuring hole opening diameter Φ=0.3mm, the corrugation profile tolerance is ±0.05mm, the step difference plane tolerance is ±0.03mm, and the outer circle gap tolerance between the disk and the plate is ±0.20mm; the upper surface roughness of the disk and the plate Ra≤0.4μm, and the surface roughness of the mating surfaces of each component Ra≤1.6μm; there is no reverse step difference in the assembly of parts, and the forward step difference does not exceed 0.05mm.

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