A system and method for measuring frictional drag of a flat plate model in a low speed wind tunnel

Abstract

A kind of regulating system and method for measuring frictional resistance of flat plate model in low-speed wind tunnel, the regulating system includes flat plate model, pressure regulating plate, static pressure measuring hole, adapter, pressure measuring tube and pressure sensor;Pressure regulating plate is rotatably connected at the end of flat plate model by adapter;Several static pressure measuring holes are distributed in line with equal intervals on flat plate model along the direction of incoming flow;Pressure sensor is connected with static pressure measuring hole by pressure measuring tube.The present application realizes accurate adjustment of static pressure on the surface of flat plate model by setting deflectable pressure regulating plate;Realizes accurate measurement of static pressure on the surface of flat plate model by setting static pressure measuring holes in line along the direction of incoming flow;Through the combination of pressure regulating and static pressure measurement, the rapid and accurate adjustment of zero pressure gradient state on the surface of flat plate model is realized, the influence of angle of attack change on the measurement accuracy of frictional resistance is effectively eliminated, the measurement accuracy of frictional resistance is significantly improved, without complex flow field measuring equipment throughout, with the remarkable characteristics of low cost, simple operation and easy engineering.

Description

Technical Field

[0001] This invention belongs to the field of wind tunnel testing technology, and in particular relates to an adjustment system and method for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel. Background Technology

[0002] In low-speed wind tunnel tests, accurately measuring the frictional drag of a flat plate model is one of the fundamental problems in aerodynamics research. To obtain an accurate measurement of the frictional drag, the flat plate model and the incoming flow must be perfectly parallel. However, in engineering practice, poor observability due to air transparency makes achieving perfect parallelism between the incoming flow and the flat plate model difficult.

[0003] Furthermore, since the wind tunnel flow field cannot completely avoid zero angle of attack error and plate model installation error, the plate model often cannot guarantee a strict zero angle of attack state in actual wind tunnel tests.

[0004] In conventional wind tunnel tests, minute deviations in angle of attack may not significantly affect the overall measurement results. However, for measuring the frictional resistance of a flat plate model, even in the most precise wind tunnels currently available, the angle of attack deviation |Δ α It can only meet the requirement of ≤0.1°, which will still have a significant impact on the measurement accuracy of the frictional resistance of the plate model. This is because a small change in the angle of attack will cause an asymmetric change in the surface pressure distribution of the plate model, thereby introducing a non-negligible pressure resistance component, causing the measured "total resistance" to deviate from the true "frictional resistance". Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an adjustment system and method for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel. By setting an adjustable pressure regulating plate at the end of the flat plate model, precise adjustment of the static pressure on the model surface is achieved. By setting a row of static pressure measuring holes along the flow direction on the flat plate model, precise measurement of the static pressure on the model surface is achieved. Through the combination of pressure regulation and static pressure measurement, rapid and precise adjustment of the zero pressure gradient state on the flat plate model surface is achieved, effectively eliminating the influence of angle of attack changes on the accuracy of frictional resistance measurement, significantly improving the accuracy of frictional resistance measurement. The entire process requires no complex flow field measurement equipment and has significant advantages such as low cost, ease of operation, and ease of engineering application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel, comprising a flat plate model, a pressure regulating plate, a static pressure measuring hole, an adapter frame, a pressure measuring tube, and a pressure sensor; the adapter frame is fixedly connected to the end of the flat plate model; one end of the pressure regulating plate is hinged to the adapter frame, and the other end of the pressure regulating plate is a free end; the static pressure measuring hole is arranged on the flat plate model; one end of the pressure measuring tube is connected to the static pressure measuring hole, and the pressure sensor is connected to the other end of the pressure measuring tube.

[0007] The number of static pressure measuring holes is several and not less than five. The several static pressure measuring holes are distributed in a straight line with equal spacing along the incoming flow direction. Each static pressure measuring hole is independently connected to a pressure measuring tube and a pressure sensor.

[0008] The width of the pressure regulating plate is equal to that of the flat plate model, and the length of the pressure regulating plate is 100mm to 300mm.

[0009] A hinge shaft is provided at the hinge point between the pressure regulating plate and the adapter frame. The hinge shaft is located in the plane of the flat plate model, and the central axis of the hinge shaft is perpendicular to the line connecting the static pressure measuring holes.

[0010] A protractor is installed between the adapter frame and the pressure regulating plate, and the protractor and the adapter frame are an integral structure.

[0011] The protractor is provided with an arc guide groove, the center of which coincides with the axis of the hinge shaft.

[0012] The angle scale of the protractor is distributed along the arc guide groove, and the measuring range of the angle scale of the protractor is ±45°.

[0013] A guide pin is inserted into the arc guide groove and is fixedly connected to the pressure regulating plate. A positioning lock nut is threaded onto the guide pin on the outside of the arc guide groove.

[0014] A method for adjusting the frictional resistance of a flat plate model in a low-speed wind tunnel, employing the aforementioned adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel, includes the following steps: Step 1: Install the flat plate model inside the wind tunnel test section and complete the connection of the pressure measuring tube and pressure sensor; Step 2: Adjust the deflection angle of the pressure regulating plate to the initial set value, and then tighten the positioning lock nut to complete the fixing of the pressure regulating plate; Step 3: Start the wind tunnel and adjust the wind speed to the initial set value; Step 4: After the wind field in the wind tunnel stabilizes, collect the static pressure of all static pressure measurement holes through pressure sensors. Take the first static pressure measurement hole at the foremost edge of the flat plate model as the benchmark measurement point and the remaining static pressure measurement holes as reference comparison points. Step 5: Calculate the difference between the static pressure at all reference comparison points and the static pressure at the benchmark measurement point, and obtain a set of static pressure difference data; Step Six: Change the deflection angle of the pressure regulating plate and repeat steps three to five to obtain multiple sets of static pressure difference data; Step 7: Change the wind speed inside the wind tunnel and repeat steps 4 to 6 to obtain multiple sets of static pressure difference data; Step 8: Select the absolute static pressure difference from multiple sets of static pressure difference data | △ P The smallest set of static pressure difference data is used as the basis for measuring the frictional resistance of the flat plate model, and the corresponding deflection angle of the pressure regulating plate and the wind tunnel wind speed are used as the basis for measuring the frictional resistance of the flat plate model.

[0015] When selecting absolute static pressure difference | △ P When using the smallest set of static pressure difference data, it is required that all data be referenced to the absolute static pressure difference between the comparison point and the benchmark measurement point.|△ P The pressure gradient must be ≤0.3Pa for the plate model to be considered to be in a state of zero pressure gradient on the surface.

[0016] The beneficial effects of this invention are: The present invention relates to an adjustment system and method for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel. This system achieves precise adjustment of the static pressure on the flat plate model surface by setting an adjustable pressure regulating plate at the end of the model; it also achieves precise measurement of the static pressure on the model surface by setting a row of static pressure measuring holes along the flow direction on the model; and by combining pressure regulation and static pressure measurement, it achieves rapid and precise adjustment of the zero pressure gradient state on the flat plate model surface, effectively eliminating the influence of angle of attack changes on the accuracy of frictional resistance measurement, significantly improving the accuracy of frictional resistance measurement, and requiring no complex flow field measurement equipment throughout the process. This system is characterized by low cost, ease of operation, and ease of engineering application. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of an adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to the present invention. In the figure, 1—flat plate model, 2—pressure regulating plate, 3—static pressure measuring hole, 4—adapter frame, 5—pressure measuring tube, 6—pressure sensor, 7—hinged shaft, 8—protractor, 9—circular arc guide groove, 10—guide pin. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0019] like Figure 1As shown, an adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel includes a flat plate model 1, a pressure regulating plate 2, a static pressure measuring hole 3, an adapter frame 4, a pressure measuring tube 5, and a pressure sensor 6. The adapter frame 4 is fixedly connected to the end of the flat plate model 1. One end of the pressure regulating plate 2 is hinged to the adapter frame 4, and the other end of the pressure regulating plate 2 is a free end. The static pressure measuring hole 3 is arranged on the flat plate model 1. One end of the pressure measuring tube 5 is connected to the static pressure measuring hole 3, and the pressure sensor 6 is connected to the other end of the pressure measuring tube 5.

[0020] The number of static pressure measuring holes 3 is several and not less than 5. The several static pressure measuring holes 3 are distributed in a straight line at equal intervals along the incoming flow direction. Each static pressure measuring hole 3 is independently connected to a pressure measuring tube 5 and a pressure sensor 6.

[0021] The width of the pressure regulating plate 2 is equal to that of the flat plate model 1, and the length of the pressure regulating plate 2 is 100mm to 300mm.

[0022] A hinge shaft 7 is provided at the hinge point between the pressure regulating plate 2 and the adapter frame 4. The hinge shaft 7 is located in the plane of the flat plate model 1, and the central axis of the hinge shaft 7 is perpendicular to the line connecting the static pressure measuring holes 3.

[0023] A protractor 8 is provided between the adapter frame 4 and the pressure regulating plate 2. The protractor 8 and the adapter frame 4 are an integral structure.

[0024] An arc guide groove 9 is provided on the protractor 8, and the center of the arc guide groove 9 coincides with the axis of the hinge shaft 7.

[0025] The angle scale of the protractor 8 is distributed along the arc guide groove 9, and the angle scale of the protractor 8 has a measurement range of ±45°.

[0026] A guide pin 10 is inserted into the arc guide groove 9. The guide pin 10 is fixedly connected to the pressure regulating plate 2. A positioning lock nut is threaded onto the guide pin 10 on the outside of the arc guide groove 9.

[0027] A method for adjusting the frictional resistance of a flat plate model in a low-speed wind tunnel, employing the aforementioned adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel, includes the following steps: Step 1: Install the flat plate model 1 in the wind tunnel test section and complete the connection between the pressure measuring tube 5 and the pressure sensor 6; in this embodiment, the number of static pressure measuring holes 3 is 16; Step 2: Adjust the deflection angle of the pressure regulating plate 2 to the initial set value, and then tighten the positioning lock nut to complete the fixing of the pressure regulating plate 2; in this embodiment, the initial set value of the deflection angle of the pressure regulating plate 2 is 5°; Step 3: Start the wind tunnel and adjust the wind speed to the initial set value; Step 4: After the wind field in the wind tunnel stabilizes, the static pressure of all static pressure measuring holes 3 is collected by the pressure sensor 6. The first static pressure measuring hole 3 at the foremost edge of the flat plate model 1 is used as the reference measuring point, and the remaining static pressure measuring holes 3 are used as reference comparison points. In this embodiment, the number of reference comparison points is 15. Step 5: Calculate the difference between the static pressure at all reference comparison points and the static pressure at the benchmark measurement point, and obtain a set of static pressure difference data; Step Six: Change the deflection angle of the pressure regulating plate 2, repeat steps three to five, and obtain multiple sets of static pressure difference data; in this embodiment, the deflection angle of the pressure regulating plate 2 changes by 0.1° each time, and the adjustment is performed 10 times, obtaining a total of 10 sets of data; Step 7: Change the wind speed inside the wind tunnel and repeat steps 4 to 6 to obtain multiple sets of static pressure difference data; in this embodiment, the wind speed change value is 0.2 m / s each time, the adjustment is performed 10 times, and a total of 10 sets of data are obtained. Step 8: Select the absolute static pressure difference from multiple sets of static pressure difference data | △ P The smallest set of static pressure difference data is used as the basis for measuring the frictional resistance of the flat plate model 1, and the deflection angle of the pressure regulating plate 2 and the wind tunnel wind speed corresponding to this set of static pressure difference data are used.

[0028] When selecting absolute static pressure difference | △ P When using the smallest set of static pressure difference data, it is required that all data be referenced to the absolute static pressure difference between the comparison point and the benchmark measurement point.|△ P | The pressure must be ≤0.3Pa for the plate model 1 to be considered to be in a state of zero pressure gradient on the surface.

[0029] The solutions in the embodiments are not intended to limit the scope of protection of the present invention. All equivalent implementations or modifications that do not depart from the present invention are included in the scope of protection of the present invention.

Claims

1. An adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel, characterized in that: The device includes a flat plate model, a pressure regulating plate, a static pressure measuring hole, an adapter frame, a pressure measuring tube, and a pressure sensor. The adapter frame is fixedly connected to the end of the flat plate model. One end of the pressure regulating plate is hinged to the adapter frame, and the other end of the pressure regulating plate is a free end. The static pressure measuring hole is arranged on the flat plate model. One end of the pressure measuring tube is connected to the static pressure measuring hole, and the pressure sensor is connected to the other end of the pressure measuring tube.

2. The adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 1, characterized in that: The number of static pressure measuring holes is several and not less than five. The several static pressure measuring holes are distributed in a straight line with equal spacing along the incoming flow direction. Each static pressure measuring hole is independently connected to a pressure measuring tube and a pressure sensor.

3. The adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 1, characterized in that: The width of the pressure regulating plate is equal to that of the flat plate model, and the length of the pressure regulating plate is 100mm to 300mm.

4. The adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 1, characterized in that: A hinge shaft is provided at the hinge point between the pressure regulating plate and the adapter frame. The hinge shaft is located in the plane of the flat plate model, and the central axis of the hinge shaft is perpendicular to the line connecting the static pressure measuring holes.

5. The adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 1, characterized in that: A protractor is installed between the adapter frame and the pressure regulating plate, and the protractor and the adapter frame are an integral structure.

6. The adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 5, characterized in that: The protractor is provided with an arc guide groove, the center of which coincides with the axis of the hinge shaft.

7. The adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 6, characterized in that: The angle scale of the protractor is distributed along the arc guide groove, and the measuring range of the angle scale of the protractor is ±45°.

8. The adjustment system for measuring the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 6, characterized in that: A guide pin is inserted into the arc guide groove and is fixedly connected to the pressure regulating plate. A positioning lock nut is threaded onto the guide pin on the outside of the arc guide groove.

9. A method for adjusting the frictional resistance of a flat plate model in a low-speed wind tunnel, comprising the adjustment system for adjusting the frictional resistance of a flat plate model in a low-speed wind tunnel as described in claim 1, characterized in that, Includes the following steps: Step 1: Install the flat plate model inside the wind tunnel test section and complete the connection of the pressure measuring tube and pressure sensor; Step 2: Adjust the deflection angle of the pressure regulating plate to the initial set value, and then tighten the positioning lock nut to complete the fixing of the pressure regulating plate; Step 3: Start the wind tunnel and adjust the wind speed to the initial set value; Step 4: After the wind field in the wind tunnel stabilizes, collect the static pressure of all static pressure measurement holes through pressure sensors. Take the first static pressure measurement hole at the foremost edge of the flat plate model as the benchmark measurement point and the remaining static pressure measurement holes as reference comparison points. Step 5: Calculate the difference between the static pressure at all reference comparison points and the static pressure at the benchmark measurement point, and obtain a set of static pressure difference data; Step Six: Change the deflection angle of the pressure regulating plate and repeat steps three to five to obtain multiple sets of static pressure difference data; Step 7: Change the wind speed inside the wind tunnel and repeat steps 4 to 6 to obtain multiple sets of static pressure difference data; Step 8: Select the absolute static pressure difference from multiple sets of static pressure difference data | △ P The smallest set of static pressure difference data is used as the basis for measuring the frictional resistance of the flat plate model, and the corresponding deflection angle of the pressure regulating plate and the wind tunnel wind speed are used as the basis for measuring the frictional resistance of the flat plate model.

10. The method for adjusting the frictional resistance of a flat plate model in a low-speed wind tunnel according to claim 9, characterized in that: When selecting absolute static pressure difference | △ P When using the smallest set of static pressure difference data, it is required that all data be referenced to the absolute static pressure difference between the comparison point and the benchmark measurement point.|△ P The pressure gradient must be ≤0.3Pa for the plate model to be considered to be in a state of zero pressure gradient on the surface.

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