A device and method for reducing support interference in wind tunnel testing

Abstract

The present application relates to the technical field of wind tunnel test, especially to a device and method for reducing support interference in wind tunnel test, which comprises a support mechanism, the support mechanism comprises a joint fixed in the wind tunnel, the joint is provided with a support rod at one end, the support rod is provided with a balance at the end away from the joint, the balance is connected with a test model, the support rod is internally provided with a blowing and sucking air device, the blowing and sucking air device comprises an air pump, the support rod side wall is provided with a sucking air port and a blowing air port, and the air pump is connected with the sucking air port and the blowing air port through pipelines respectively. The blowing and sucking air device is installed in the support mechanism, blowing and sucking air parameters are adjusted, the support mechanism windward face stagnation point, leeward low energy area and detached vortex structure are eliminated or weakened, the interference of the support mechanism flow to the test model area flow field is weakened or even eliminated, and then the support interference is reduced, the method is novel, the effect is obvious, the complex process of support interference correction is avoided, no additional negative impact is brought, and the method has strong engineering practicability.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing technology, and in particular to a device and method for reducing support interference during wind tunnel testing. Background Technology

[0002] In wind tunnel testing, support (support) mechanisms are needed to mount the test model and obtain its aerodynamic parameters. Commonly used support mechanisms include tail supports, back supports, belly supports, and tension supports. These support mechanisms inevitably interfere with the flow field around the test model, resulting in the obtained aerodynamic parameters containing interference from the support mechanisms. This interference with the experimental results is known as support interference. Therefore, it is generally necessary to reduce support interference or find methods to subtract it to correct the aerodynamic parameters.

[0003] Currently, the main methods to reduce support interference include: (1) minimizing the cross-sectional size of the support rod and the length of the support rod exposed to the airflow while meeting the requirements of strength and stiffness; (2) rationally selecting the support form and the cross-sectional shape of the support rod; (3) adopting fixed transition measures for circular cross-section support rods and adopting regular polygonal cross-section support rods; (4) improving the design of the support frame, etc. These methods can reduce support interference to a certain extent. However, in actual use, it is often necessary to select the support according to the layout of the test model. For example, tail supports can reduce support interference for slender missile bodies, and belly supports can reduce support interference for longitudinal tests of aircraft. Multiple support methods need to be changed during the test, which is a complex process and difficult to implement.

[0004] The main methods for deducting support interference are superposition and auxiliary support. This method has been widely used both domestically and internationally for many years. The premise for the superposition method is that the flow field is assumed to be ideal fluid, steady and irrotational motion, and small disturbances. In reality, many situations cannot fully meet the above assumptions. Studies suggest that if (1) the secondary disturbance is one order of magnitude smaller than the disturbance to be measured, and (2) the flow is periodic but a stable average value can be obtained, the superposition method can be used approximately. Based on the principle of the superposition method, the support interference is obtained by the mirror two-step method or the three-step method. For example, the mirror two-step method is used to measure the belly support interference using an internal strain balance. The first step involves mounting the model upright (belly down), with the belly support strut (located below the model and connected to it via an internal balance) and its mirror image strut (located above the model, not connected to it). The aerodynamic parameters F1, including the disturbances of the belly support strut and its mirror image strut, are measured. The second step involves mounting the model in reverse (belly up), with the belly support strut (located below the model and connected to it via an internal balance, similar to the mirror image strut in the first step). The aerodynamic parameters F2, including the disturbances of the mirror image strut, are measured. Subtracting F2 from the aerodynamic parameters F1 obtained in the first two steps yields the disturbance amount of the belly support strut.

[0005] As can be seen, the measurement and subtraction process for support interference is complex. Each type of support interference requires specific main supports and auxiliary mirror supports, and errors introduced during assembly and disassembly are unavoidable. Furthermore, the support interference measured above is only effective at small angles of attack or small sideslip angles. For large angles of attack or large sideslip angles, due to the complex vortex separation and interference characteristics of the model itself, the flow field does not satisfy the superposition method assumption, and the support interference obtained by the above subtraction method is severely distorted. At this time, the support interference is often on the same order of magnitude as the aerodynamic force being measured and cannot be ignored. Therefore, how to reduce support interference has become one of the difficulties in wind tunnel testing.

[0006] Essentially, support disturbance is the effect of the flow around the support mechanism on the flow around the test model. However, current methods mainly focus on passive flow control, such as reducing the size of the support rods and using streamlined cross-section support rods, lacking methods to reduce support disturbance from the perspective of active flow control. Therefore, this invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a device and method for reducing support interference in wind tunnel tests. This device and method is an active measure that avoids the auxiliary support rods and complex disassembly and assembly processes required by traditional passive measures, thereby reducing secondary interference errors and disassembly and assembly errors caused by auxiliary support rods.

[0008] This invention provides a device for reducing support interference in wind tunnel testing, comprising a support mechanism, the support mechanism including a joint, a support rod at one end of the joint, a balance at the end of the support rod away from the joint, the balance being connected to a test model, an air blowing and suction device inside the support rod including an air pump, an air intake port and an air blowing port on the side wall of the support rod, and the air pump being connected to the air blowing port and the air intake port respectively through pipes.

[0009] Furthermore, the air intake is located upstream of the incoming flow, and the air outlet is located downstream of the incoming flow.

[0010] Furthermore, the number of the blowing port or the suction port can be one or more.

[0011] This invention provides a method for reducing support interference during wind tunnel testing using the aforementioned device, comprising the following steps:

[0012] S1. Determine the test model, support form, test conditions, and test model area;

[0013] S2. Based on the test conditions, measure the initial velocity field in the test model region that satisfies the flow field quality.

[0014] S3. Install the connector and the support rod, and measure the disturbance velocity field of the test model area when the connector and the support rod are present, according to the test conditions;

[0015] S4. Install the air blowing and suction device on the support rod;

[0016] S5. Adjust the blowing and suction parameters so that the velocity vector difference between the interference velocity field in the test model area and the initial velocity field obtained in step S2 at the same position when the joint and the support rod are present is less than a specific value, and determine it as the blowing and suction parameters for this test state;

[0017] S6. Install the balance on the support rod and install the test model, set the blowing and sucking parameters for this test state, and obtain the aerodynamic parameter results for reducing the amount of support interference.

[0018] Furthermore, the support form in step S1 includes one of tail support, belly support and back support, the test state includes wind speed, test angle of attack and sideslip angle, and the test model area is the spatial envelope area of ​​the test model under different test states.

[0019] Furthermore, the initial velocity field and disturbance velocity field measurement points required for the test model area in steps S2 and S3 are uniformly distributed points within the spatial envelope region, with the measurement points being densified near the support.

[0020] Furthermore, the blowing and suction parameters in step S5 include the geometric dimensions of the suction port and the blowing port, the pipe pressure, the gas flow rate, the blowing airflow angle, and the suction airflow angle.

[0021] Furthermore, the blowing and suction device uses suction upstream of the incoming flow and blowing downstream of the incoming flow. By adjusting the airflow pressure, flow rate and angle, the blowing and suction device eliminates or weakens the stagnation point on the windward side of the support mechanism, the low-energy area on the leeward side and the detached vortex structure, thereby reducing the interference of the support mechanism on the flow field of the test model area.

[0022] Furthermore, step S6 also includes obtaining the aerodynamic parameter results for reducing support interference, and adjusting them within the range of blowing and sucking parameters until the optimal aerodynamic parameter results for reducing support interference are obtained.

[0023] In summary, compared with the prior art, the present invention has the following advantages:

[0024] The technical solution provided by this invention is to set up a blowing and suction device on the support rod, adjust the blowing and suction parameters, eliminate or reduce the stagnation point on the windward side of the support mechanism, the low-energy area on the leeward side, and the detached vortex structure, thereby reducing or even eliminating the interference of the flow around the support mechanism on the flow field of the test model area, and thus reducing the amount of support interference.

[0025] The technical solution of the present invention reduces the interference of wind tunnel test support by setting a blowing and suction device on the support mechanism. It is an active measure that avoids the auxiliary support rods and complicated disassembly and assembly process required by traditional passive measures, and reduces the secondary interference error and disassembly and assembly error caused by the auxiliary support rods.

[0026] The method for reducing support interference provided by this invention is novel and effective. It avoids the complex process of support interference correction, does not bring additional negative effects, and has strong engineering applicability. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the support mechanism in Embodiment 1 of the present invention;

[0029] Figure 2 This is a comparison diagram of abdominal support interference between the present invention embodiment 1 and the embodiment with the inhalation and exhalation device installed;

[0030] Figure 3 This is a schematic diagram of the support mechanism in Embodiment 2 of the present invention;

[0031] Figure 4 This is a comparison diagram of the amount of tail support interference in Embodiment 2 of the present invention with and without the blowing and suction device.

[0032] Explanation of reference numerals in the attached drawings: 1-Connector; 2-Support rod; 3-Balance; 4-Test model; 5-Inlet; 6-Outlet; 7-Pipeline; 8-Air pump. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] Analysis of existing methods for reducing support interference and for correcting support interference reveals that existing methods are passive, requiring support design and fabrication based on the layout; existing methods for correcting support interference are complex and no longer applicable at high angles of attack or sideslip angles. Support interference essentially refers to the interference of the exposed support flow around the model. The main idea of ​​this invention is to reduce or eliminate the influence of the support on the flow around the test model through active flow control.

[0037] This invention provides a device for reducing support interference during wind tunnel testing, such as... Figure 1 or Figure 3 As shown, the system includes a support mechanism, comprising a connector 1 fixed in the wind tunnel. One end of the connector 1 is fixedly connected to a support rod 2. A balance 3 is located at the end of the support rod 2 away from the connector 1. The balance 3 is connected to the support rod 2 via a conical surface mating with a wedge, and is connected to a test model 4. The test model 4 and the balance 3 are connected via a threaded connection on the conical surface mating end face. A blowing and suction device is located inside the support rod 2. The connections between the connector 1 and the wind tunnel and the support rod 2, the connection between the support rod 2 and the balance 3, and the connection between the balance 3 and the test model 4 in this invention are all conventional techniques in the field.

[0038] The support rod 2 has an internal cavity, with the end of the cavity furthest from the connector 1 connected to the outside, facilitating the placement of the air blowing / suction device inside. The air blowing / suction device includes an air pump 8. The side wall of the support rod 2 has an air intake 5 and an air blowing port 6 communicating with the cavity. The air pump 8 is connected to the air intake 5 and air blowing port 6 via pipes 7. The air intake 5 is located upstream of the incoming flow, and the air blowing port 6 is located downstream. There can be one or more air intake ports 5 and air blowing ports 6, and their geometric dimensions can be set according to experimental requirements. The air pump 8 can be fixed in the cavity using conventional methods such as threaded connections or snap-fit ​​connections. The opening of the pipe 7 can be fixed to the air intake 5 and air blowing port 6 using conventional methods such as snap-fit ​​connections or adhesive connections.

[0039] The method for reducing support interference using the aforementioned device in wind tunnel testing follows these steps:

[0040] S1. Determine the support structure, test conditions, and test model area based on the layout of the test model;

[0041] S2. Based on the test conditions, conduct flow field measurement tests in the test model area to obtain the initial velocity field in the test model area that meets the flow field quality requirements;

[0042] S3. Install joint 1 and support rod 2, and conduct flow field measurement tests in the test model area according to the test conditions to obtain the disturbance velocity field in the test model area when joint 1 and support rod 2 are present;

[0043] S4. Install a blower / suction device on support rod 2;

[0044] S5. Adjust the blowing and suction parameters so that the velocity vector difference between the interference velocity field of the test model area obtained in step S3 and the initial velocity field obtained in step S2 at the same position is less than a specific value, and determine it as the blowing and suction parameters for this test state.

[0045] S6. Install the balance 3 on the support rod 2 and install the test model 4. Set the blowing and sucking parameters for this test state and obtain the aerodynamic parameter results for reducing the amount of support interference.

[0046] In step S1, the support forms include tail support, belly support and back support, the test states include wind speed, test angle of attack and sideslip angle, and the test model area is the spatial envelope area of ​​the test model under different test states.

[0047] In steps S2 and S3, the initial velocity field and disturbance velocity field measurement points required for the test model area are uniformly distributed points in the spatial envelope area, and the measurement points are densified near the support.

[0048] In step S4, the air blowing and suction device includes an air pump 8, an air intake 5, an air blowing port 6, and a pipe 7. The air blowing and suction parameters include the geometric dimensions of the air blowing and suction ports, pipe pressure, flow rate, and airflow angle. The air blowing and suction device uses suction upstream and blowing downstream. The airflow angle of the air intake 5 and air blowing port 6 can be adjusted by adjusting the installation position of the pipe. The air blowing and suction device eliminates or weakens the stagnation point on the windward side of the support structure, the low-energy area on the leeward side, and the detached vortex structure by adjusting the airflow pressure, flow rate, and angle (achieved by installing conventional throttle valves, pressure regulating valves, flow meters, etc.), thereby reducing the interference of the support structure on the flow field of the test model area. The air blowing port 6 or the air intake port 5 can be a single opening or multiple openings, and the opening parameters include the opening shape, position, and geometric dimensions.

[0049] Example 1

[0050] The support mechanism used in this embodiment is as follows: Figure 1 The diagram shows the abdominal support mechanism. In wind tunnel testing, the abdominal support mechanism is used to reduce support interference. The specific process is as follows:

[0051] S1. The test model is determined to be an aircraft layout model with belly support, a test wind speed of 80 m / s, a test angle of attack of 30°, and a test model area F1 (a cuboid area with a length of 1000 mm, a width of 1000 mm, and a height of 1000 mm that is symmetrical about the center of the test section).

[0052] S2. Conduct a velocity field measurement test of the test model region F1 in step S1 at an angle of attack of 30° to obtain the initial velocity field of the test model region F1 that satisfies the flow field quality.

[0053] S3. Install joint 1 and support rod 2, and conduct flow field measurement test in the test model area at a test wind speed of 80m / s and a test angle of attack of 30° to obtain the disturbance velocity field of the test model area F1 when joint 1 and support rod 2 are present;

[0054] S4. Install a blower / suction device on support rod 2;

[0055] S5. Adjust the blowing and suction parameters so that the velocity vector difference between the interference velocity field of the test model area F1 when joint 1 and support rod 2 are present, obtained in step S3, and the initial velocity field at the same position is less than 5%, and determine the blowing and suction parameters for this test state.

[0056] S6. Install the balance 3 on the support rod 2 and the test model 4. Set the blowing and suction parameters for this test state to obtain the aerodynamic parameter results for reducing the support interference. Adjust the blowing and suction parameters within the range until the optimal aerodynamic parameter results for reducing the support interference are obtained.

[0057] A comparative experiment was also set up, which used a conventional abdominal support mechanism, i.e., the support rod 2 was a solid structure, without a blowing and inhaling device, and the amount of abdominal support interference was obtained by the traditional two-step method.

[0058] Experimental results are as follows Figure 2 As shown, from Figure 2 It can be clearly seen that in the high angle of attack region (20°-50°), the amount of support interference obtained by the abdominal support mechanism with the blowing and suction device provided in this embodiment is significantly less than the amount of support interference obtained by the abdominal support mechanism without the blowing and suction device.

[0059] Example 2

[0060] The support mechanism used in this embodiment is as follows: Figure 3 The image shows the tail support mechanism. The method of using a tail support mechanism to reduce support interference in wind tunnel testing is as follows:

[0061] S1. The test model is determined to be a slender body model with tail support, the test wind speed is 35m / s, the test angle of attack is 50°, and the test model area is F2 (a cuboid area with a length of 1000mm, a width of 1000mm, and a height of 1000mm that is symmetrical about the center of the test section).

[0062] S2. Conduct a velocity field measurement test on the test model region F2 in step S1 at an angle of attack of 50° to obtain the initial velocity field of the test model region F2 that satisfies the flow field quality.

[0063] S3. Install joint 1 and support rod 2, and conduct flow field measurement test of F2 in the test model area at a test wind speed of 35m / s and a test angle of attack of 50° to obtain the disturbance velocity field of the test model area when joint 1 and support rod 2 are present.

[0064] S4. Install a blower / suction device on support rod 2;

[0065] S5. Adjust the blowing and suction parameters so that the velocity vector difference between the interference velocity field in the test model area obtained in step S3 and the initial velocity field obtained in step S2 at the same position is less than 5%, and determine it as the blowing and suction parameters for this test state.

[0066] S6. Install the balance 3 on the support rod 2 and the test model 4. Set the blowing and suction parameters for this test state to obtain the aerodynamic parameter results for reducing the support interference. Adjust the blowing and suction parameters within the range until the optimal aerodynamic parameter results for reducing the support interference are obtained.

[0067] Meanwhile, a comparative experiment was set up. The comparative experiment used a conventional tail support mechanism, that is, the support rod 2 is a solid structure, without a blowing or sucking device, and the traditional two-step method was used to obtain the tail support interference.

[0068] Experimental results are as follows Figure 4 As shown, from Figure 4 It can be clearly seen that in the high angle of attack region (40°-80°), the amount of support interference obtained by the tail support mechanism with the air blowing and suction device provided in this embodiment is significantly less than the amount of support interference obtained by the tail support mechanism without the air blowing and suction device.

[0069] The support mechanism with blowing and sucking device provided by the present invention can adapt to test models with different aerodynamic layouts. In particular, it can handle situations where there is a lot of support interference at large angles of attack or large sideslip angles without causing additional negative effects, and has strong engineering practicality.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reducing support interference during wind tunnel testing, characterized in that, The wind tunnel test is conducted using a device to reduce the amount of support interference. The device includes a support mechanism, which includes a connector (1). One end of the connector (1) is provided with a support rod (2). The end of the support rod (2) away from the connector (1) is provided with a balance (3). The balance (3) is connected to the test model. The support rod (2) is provided with a blowing and suction device inside. The blowing and suction device includes an air pump (8). The side wall of the support rod (2) is provided with an air inlet (5) and an air outlet (6). The air pump (8) is connected to the air inlet (5) and the air outlet (6) respectively through a pipe (7). Includes the following steps: S1. Determine the test model, support form, test conditions, and test model area; S2. Based on the test conditions, measure the initial velocity field in the test model region that satisfies the flow field quality. S3. Install the joint (1) and the support rod (2), and measure the disturbance velocity field of the test model area when the joint (1) and the support rod (2) are present, according to the test conditions; S4. Install the blowing and suction device on the support rod (2); S5. Adjust the blowing and suction parameters so that the velocity vector difference between the interference velocity field of the test model area and the initial velocity field obtained in step S2 at the same position when the joint (1) and the support rod (2) are present is less than a specific value, and determine it as the blowing and suction parameters of the test state; S6. Install the balance (3) on the support rod (2), install the test model, set the blowing and sucking parameters of the test state, and obtain the aerodynamic parameter results for reducing the amount of support interference; The blowing and suction device uses suction upstream of the incoming flow and blowing downstream of the incoming flow. By adjusting the air pressure, flow rate and angle, the blowing and suction device eliminates or weakens the stagnation point on the windward side of the support mechanism, the low-energy area on the leeward side and the detached vortex structure, thereby reducing the interference of the support mechanism on the flow field of the test model area.

2. The method according to claim 1, characterized in that, The air inlet (5) is located upstream of the incoming flow, and the air outlet (6) is located downstream of the incoming flow.

3. The method according to claim 1, characterized in that, The number of the air inlet (5) or the air outlet (6) is one or more.

4. The method according to claim 1, characterized in that, The support form in step S1 includes one of tail support, belly support and back support. The test state includes wind speed, test angle of attack and sideslip angle. The test model area is the spatial envelope area of ​​the test model under different test states.

5. The method according to claim 1, characterized in that, The initial velocity field and disturbance velocity field measurement points required for the test model area in steps S2 and S3 are uniformly distributed points in the spatial envelope area, with the measurement points being densified near the support.

6. The method according to claim 1, characterized in that, The blowing and suction parameters in step S5 include the geometric dimensions of the suction port (5) and the blowing port (6), the pipe pressure, the gas flow rate, the blowing airflow angle, and the suction airflow angle.

7. The method according to claim 1, characterized in that, Step S6 further includes obtaining the aerodynamic parameter results for reducing support interference, and adjusting them within the range of blowing and sucking parameters until the optimal aerodynamic parameter results for reducing support interference are obtained.

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