Device and method for reducing support disturbance variable in wind tunnel test

Abstract

The invention relates to the technical field of wind tunnel tests, in particular to a device and method for reducing support disturbance variable in a wind tunnel test. Comprising a supporting mechanism, the supporting mechanism comprises a connector fixed in a wind tunnel, a supporting rod is arranged at one end of the connector, a balance is arranged at the end, away from the connector, of the supporting rod, the balance is connected with a test model, and an air blowing and sucking device is arranged in the supporting rod and comprises an air pump; the air pump is connected with the air suction port and the air blowing port through pipelines. By installing the air blowing and sucking device in the supporting mechanism, adjusting air blowing and sucking parameters, eliminating or weakening a windward side stagnation point, a leeside low-energy area and a detached vortex structure of the supporting mechanism, and weakening or even eliminating the interference amount of streaming of the supporting mechanism on a test model area flow field, the supporting interference amount is further reduced, the method is novel, the effect is obvious, and the method is suitable for popularization and application. The complex process of supporting interference correction is avoided, additional negative effects are avoided, and the method has high engineering practicability.

Description

Technical Field

[0001] The present invention relates to the technical field of wind tunnel testing, and in particular to a device and method for reducing support interference in a wind tunnel test. Background Art

[0002] In wind tunnel tests, a support (bracket) mechanism is required to install the test model and obtain the aerodynamic parameters of the test model. Common support mechanisms include tail support, back support, abdominal support, and wire support. The support mechanism inevitably interferes with the flow field around the test model, so that the obtained aerodynamic parameters contain the interference of the support mechanism. This interference effect on the experimental results is also called bracket interference. Therefore, it is generally necessary to reduce the bracket interference or find a way to deduct the support (bracket) interference and correct the aerodynamic parameters.

[0003] At present, the main methods to reduce the amount of support interference are: (1) to minimize the cross-sectional dimensions of the struts and the length of the struts exposed to the airflow while meeting the strength and stiffness conditions; (2) to reasonably select the support form and the cross-sectional shape of the struts; (3) to adopt fixed transition measures for circular cross-sectional struts and regular polygonal cross-sectional struts; (4) to improve the design of the support frame, etc. These methods can reduce the amount of support interference to a certain extent. In actual use, it is often necessary to select supports according to the layout of the test model. For example, the use of tail supports for slender missile bodies can reduce support interference, and the use of belly supports for longitudinal tests of aircraft can reduce support interference. In the test, it is necessary to replace multiple support methods, which is a complicated process and difficult to achieve.

[0004] The main methods for deducting support interference are superposition and auxiliary support. This method has been widely used at home and abroad for many years. The premise of the superposition method is the assumption of ideal fluid, steady and irrotational motion and small disturbance. In fact, many situations cannot fully meet the above assumptions. Studies have shown that if (1) the secondary interference is one order of magnitude smaller than the interference 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 superposition, the support interference is obtained by the mirror two-step method or the three-step method. For example, the mirror two-step method of measuring the belly support interference is used with an internal strain balance. In the first step, the model is installed upright (belly downward), with a belly support rod (located below the model and connected to the model through an internal balance) and a mirror rod of the belly support rod (located above the model and not connected to the model), and the model aerodynamic parameter F1 including the interference amount of the belly support rod and the mirror rod is measured; in the second step, the model is installed inversely (belly upward), with a belly support rod (located below the model and connected to the model through an internal balance, which is similar to the mirror rod in the first step), and the model aerodynamic parameter F2 including the interference amount of the mirror rod is measured; the aerodynamic parameter F1 obtained in the above two steps minus F2 can obtain the interference amount of the belly support rod.

[0005] It can be seen that the measurement and deduction process of the support interference is complicated. Each type of support interference requires a specific main support rod and auxiliary mirror support rod, and the error introduced by disassembly and assembly is inevitable. In addition, the support interference measured above is only valid at small angles of attack or small sideslip angles. For large angles of attack or large sideslip angles, due to the complex flow 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 deduction method is seriously distorted. At this time, the support interference is often of the same order of magnitude as the aerodynamic force to be measured and cannot be ignored. Therefore, how to reduce the support interference has become one of the difficulties in wind tunnel testing.

[0006] In essence, support interference is the influence of the flow around the support mechanism on the flow around the test model, but the current methods are mainly based on the passive flow control idea, such as reducing the size of the support rod, using streamlined cross-section support rods, etc., lacking a method to reduce the amount of support interference from the perspective of active flow control. Therefore, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a device and method for reducing the amount of support interference in a wind tunnel test. The device and method are active measures that avoid the auxiliary support rods and complex disassembly and assembly processes required by traditional passive measures, and reduce the secondary interference errors and disassembly and assembly errors caused by the auxiliary support rods.

[0008] The present invention provides a device for reducing the amount of support interference in a wind tunnel test, comprising a support mechanism, wherein the support mechanism comprises a joint, a support rod is provided at one end of the joint, a balance is provided at one end of the support rod away from the joint, the balance is connected to a test model, an air blowing and suction device is provided inside the support rod, the air blowing and suction device comprises an air pump, an air suction port and an air blowing port are provided on a side wall of the support rod, and the air pump is respectively connected to the air blowing port and the air suction port through pipelines.

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

[0010] Furthermore, the number of the blowing port or the inhaling port may be one or more.

[0011] The present invention provides a method for reducing the amount of support interference in a wind tunnel test by using the above device, comprising the following steps:

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

[0013] S2. According to the test state, measure the initial velocity field of the test model area that meets the flow field quality;

[0014] S3. Install the joint and the strut, and measure the interference velocity field of the test model region when the joint and the strut exist according to the test state;

[0015] S4. The blowing and suction device is installed 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 when the joint and the support rod exist and the velocity vector difference at the same position of the initial velocity field obtained in step S2 is less than a specific value, and determine it as the blowing and suction parameters of the test state;

[0017] S6. Install the balance on the support rod, install the test model, set the blowing and suction parameters of the test state, and obtain the pneumatic parameter results that reduce the support interference amount.

[0018] Furthermore, the support form in step S1 includes one of a tail support, a belly support and a 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 interference velocity field measurement points required for the test model area in step S2 and step S3 are evenly distributed points in the space envelope area, and the measurement points are encrypted at positions close to the support.

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

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

[0022] Furthermore, the step S6 also includes obtaining a pneumatic parameter result for reducing the amount of support interference, and adjusting within the blowing and suction parameter range until an optimal aerodynamic parameter result for reducing the amount of support interference is obtained.

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

[0024] The technical solution provided by the present invention is to arrange a blowing and suction device on the support rod, adjust the blowing and suction parameters, eliminate or weaken the stagnation point on the windward side of the support mechanism, the low energy area on the leeward side and the detached vortex structure, weaken or even eliminate the interference of the support mechanism flow on the flow field in the test model area, and thus reduce the support interference.

[0025] The technical solution of the present invention is a method for reducing the interference of the support amount in the wind tunnel test by arranging a blowing and suction device on the support mechanism. It is an active measure, avoiding the auxiliary support rods and complicated disassembly and assembly processes required by traditional passive measures, and reducing the secondary interference error and disassembly and assembly error caused by the auxiliary support rods.

[0026] The method for reducing the support interference amount provided by the present invention is novel, has obvious effect, avoids the complicated process of supporting interference correction, does not bring additional negative effects, and has strong engineering practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a structural schematic diagram of the support mechanism in Example 1 of the present invention;

[0029] Figure 2 This is a comparison diagram of the abdominal support interference amount when the blowing and suction device is not installed and when the blowing and suction device is installed in Example 1 of the present invention;

[0030] Figure 3 It is a structural schematic diagram of the support mechanism in Example 2 of the present invention;

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

[0032] Explanation of the reference numerals: 1-connector; 2-support rod; 3-balance; 4-test model; 5-inhalation port; 6-inhalation port; 7-pipeline; 8-air pump. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than 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.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0035] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] By analyzing the existing methods for reducing support interference and support correction methods, it is found that the existing methods for reducing support interference are passive methods, which require support design and processing according to the layout; the existing support interference correction process is complicated and is no longer applicable at large angles of attack or sideslip. Support interference is essentially the interference of the support flow exposed in the flow field on the model flow. The main idea of ​​the present invention is to reduce or eliminate its influence on the test model flow by actively controlling the support flow.

[0037] The present invention provides a device for reducing the amount of support interference in a wind tunnel test, such as Figure 1 or Figure 3 As shown, the supporting mechanism includes a joint 1 fixed in the wind tunnel, one end of the joint 1 is fixedly connected to a support rod 2, and a balance 3 is provided at the end of the support rod 2 away from the joint 1, and the balance 3 is connected to the support rod 2 through a conical surface matching oblique splitting tension, and the balance 3 is connected to the test model 4, and the test model 4 is connected to the balance 3 through a conical surface matching end surface thread connection; a blowing and suction device is provided inside the support rod 2. The connection between the joint 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 the present invention are all conventional technical means in the field.

[0038] A cavity is provided inside the support rod 2, and one end of the cavity away from the joint 1 is connected to the outside world, so as to facilitate placing the blowing and suction device into the cavity. The blowing and suction device includes an air pump 8. An air suction port 5 and an air blowing port 6 connected to the cavity are provided on the side wall of the support rod 2. The air pump 8 is connected to the air suction port 5 and the air blowing port 6 respectively through a pipe 7. The air suction port 5 is located upstream of the incoming flow, and the air blowing port 6 is located downstream of the incoming flow. The number of the air suction port 5 and the air blowing port 6 can be one or more, and the geometric dimensions of the air suction port 5 and the air blowing port 6 can be set according to the experimental requirements. The air pump 8 can be fixed in the cavity by conventional means such as threaded connection and clamping, and the mouth of the pipe 7 can be fixed to the air suction port 5 and the air blowing port 6 by conventional means such as clamping and bonding.

[0039] The method of using the above device to reduce the amount of support interference in a wind tunnel test is as follows:

[0040] S1. Determine the support form, test state and test model area according to the test model layout;

[0041] S2. Conduct flow field measurement tests in the test model area according to the test status to obtain an initial velocity field in the test model area that meets the flow field quality requirements;

[0042] S3. Install the joint 1 and the support rod 2, and carry out the flow field measurement test of the test model area according to the test state to obtain the interference velocity field of the test model area when the joint 1 and the support rod 2 exist;

[0043] S4. Install a blowing and suction device on the 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 region when the joint 1 and the support rod 2 obtained in step S3 exist and the velocity vector difference at the same position of the initial velocity field obtained in step S2 is less than a specific value, and determine it as the blowing and suction parameters of the test state;

[0045] S6. Install the balance 3 on the support rod 2, and install the test model 4, set the blowing and suction parameters of the test state, and obtain the pneumatic parameter results that reduce the support interference amount.

[0046] Wherein: in step S1, the support forms include tail support, belly support and back support, the test conditions 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 conditions.

[0047] In step S2 and step S3, the initial velocity field and interference velocity field measurement points required for the test model area are evenly distributed points in the spatial envelope area, and the measurement points are encrypted at positions close to the support.

[0048] In step S4, the blowing and suction device includes an air pump 8, an air inlet 5, an air blowing port 6 and a pipeline 7, and the blowing and suction parameters include the geometric dimensions of the blowing and suction ports, pipeline pressure, flow rate, and blowing and suction airflow angle; the blowing and suction device adopts the method of suction in the upstream of the incoming flow and blowing in the downstream; the airflow angles of the air inlet 5 and the air blowing port 6 can be adjusted by adjusting the installation position of the pipeline; 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 by adjusting the airflow pressure, flow rate and angle (by installing conventional throttle valves, pressure regulating valves, flow meters and other components), thereby reducing the interference of the support mechanism on the flow field in the test model area. The blowing port 6 or the air inlet 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 supporting mechanism used in this embodiment is as follows Figure 1 The figure shows an abdominal support mechanism. The method of using the abdominal support mechanism to reduce the support interference in the wind tunnel test is as follows:

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

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

[0053] S3. Install the joint 1 and the support rod 2, and carry out the flow field measurement test of the test model area at the test wind speed of 80m / s and the test angle of attack of 30° to obtain the interference velocity field of the test model area F1 when the joint 1 and the support rod 2 exist;

[0054] S4. Install a blowing and suction device on the 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 region F1 and the initial velocity field obtained in step S2 at the same position when the joint 1 and the support rod 2 obtained in step S3 exist is less than 5%, and determine the blowing and suction parameters of the test state;

[0056] S6. Install the balance 3 and the test model 4 on the support rod 2, set the blowing and suction parameters of the test state, obtain the pneumatic parameter results for reducing the support interference amount, and adjust within the blowing and suction parameter range until the optimal pneumatic parameter results for reducing the support interference amount are obtained.

[0057] Meanwhile, a comparative experiment is set up, in which a conventional abdominal support mechanism is used, that is, the support rod 2 is a solid structure, and no blowing and suction device is set up, and the abdominal support interference amount is obtained by a traditional two-step method.

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

[0059] Example 2

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

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

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

[0063] S3. Install the joint 1 and the support rod 2, and carry out the flow field measurement test of the test model area F2 at the test wind speed of 35m / s and the test angle of attack of 50° to obtain the interference velocity field of the test model area when the joint 1 and the support rod 2 exist;

[0064] S4. Install a blowing and suction device on the support rod 2;

[0065] S5. Adjust the blowing and suction parameters so that the velocity vector difference between the interference velocity field of the test model region when the joint 1 and the support rod 2 obtained in step S3 exist and the velocity vector difference at the same position of the initial velocity field obtained in step S2 is less than 5%, and determine the blowing and suction parameters of the test state;

[0066] S6. Install the balance 3 and the test model 4 on the support rod 2, set the blowing and suction parameters of the test state, obtain the pneumatic parameter results for reducing the support interference amount, and adjust within the blowing and suction parameter range until the optimal pneumatic parameter results for reducing the support interference amount are obtained.

[0067] At the same time, a comparative experiment is set up. The comparative experiment adopts a conventional tail support mechanism, that is, the support rod 2 is a solid structure, and no blowing and suction device is set. The traditional two-step method is used to obtain the tail support interference amount.

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

[0069] The support mechanism with the blowing and suction device provided by the present invention can adapt to test models with different aerodynamic layouts, especially for situations where the support interference is relatively large at large angles of attack or large sideslip angles, does not bring 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 device for reducing the amount of support interference in a wind tunnel test, comprising a support mechanism, the support mechanism comprising a joint (1), one end of the joint (1) being provided with a support rod (2), the end of the support rod (2) away from the joint (1) being provided with a balance (3), the balance (3) being connected to a test model, characterized in that: An air blowing and suction device is provided inside the support rod (2), and the air blowing and suction device comprises an air pump (8). An air suction port (5) and an air blowing port (6) are provided on the side wall of the support rod (2), and the air pump (8) is connected to the air suction port (5) and the air blowing port (6) respectively through a pipeline (7).

2. The device for reducing the amount of support interference in a wind tunnel test 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 device for reducing the amount of support interference in a wind tunnel test according to claim 1, characterized in that: The number of the air intake port (5) or the air blowing port (6) may be one or more.

4. A method for reducing the amount of support interference in a wind tunnel test using the device described in any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Determine the test model, support form, test state and test model area; S2. According to the test state, measure the initial velocity field of the test model area that meets the flow field quality; S3. Install the joint (1) and the support rod (2), and measure the interference velocity field of the test model region when the joint (1) and the support rod (2) exist according to the test state; S4. Installing 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 in 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) exist 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), and install the test model, set the blowing and suction parameters of the test state, and obtain the pneumatic parameter results that reduce the support interference amount.

5. The method according to claim 4, characterized in that The support form in step S1 includes one of a tail support, a belly support and a 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.

6. The method according to claim 4, characterized in that The initial velocity field and interference velocity field measurement points required for the test model area in step S2 and step S3 are evenly distributed points in the space envelope area, and the measurement points are encrypted at positions close to the support.

7. The method according to claim 4, characterized in that The blowing and inhaling parameters in step S5 include the geometric dimensions of the inhalation port (5) and the blowing port (6), the pipeline pressure, the gas flow rate, the blowing air flow angle and the inhalation air flow angle.

8. The method according to claim 4, characterized in that The air blowing and suction device adopts the method of suction at the upstream of the incoming flow and blowing at the downstream of the incoming flow. The air blowing and suction device eliminates or weakens the stagnation point on the windward side, the low energy area on the leeward side and the detached vortex structure of the support mechanism by adjusting the airflow pressure, flow rate and angle, thereby reducing the interference of the support mechanism on the flow field in the test model area.

9. The method according to claim 4, characterized in that The step S6 also includes obtaining a pneumatic parameter result for reducing the amount of support interference, and adjusting within the blowing and suction parameter range until an optimal aerodynamic parameter result for reducing the amount of support interference is obtained.

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