Method and structure for confirming two-dimensionality of airfoil test and wind tunnel sidewall interference region

Abstract

The application discloses a method and structure for confirming two-dimensionality of airfoil test and wind tunnel side wall interference area, and belongs to the technical field of airfoil test based on mechanical sensors. The method solves the problem that the traditional wind tunnel side wall interference evaluation method for airfoil test in the prior art is difficult to accurately determine the wind tunnel interference range; the method comprises the following steps: S1. A plurality of pressure measuring holes are arranged on the upper surface of an airfoil model at least two positions along the span direction from the center section of the airfoil model as a starting point, and an airfoil model upper surface pressure hole area is arranged; S2. The size of the two-dimensionality of the airfoil test and the wind tunnel side wall interference area is confirmed by analyzing the pressure distribution measurement results of the airfoil model upper surface pressure hole area and according to evaluation conditions. The application effectively improves the range accuracy of the wind tunnel side wall interference area of the airfoil test, can provide support for airfoil pressure distribution measurement, and can be applied to confirming the two-dimensionality of the airfoil test and the wind tunnel side wall interference area.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and structure for confirming the two-dimensionality of airfoil test and the interference area of wind tunnel side wall, belonging to the technical field of airfoil test based on mechanical sensor. BACKGROUND

[0002] Airfoil test is a method for measuring and obtaining the pressure distribution of the chordwise surface of an airfoil model, and then obtaining the aerodynamic characteristics of the airfoil such as lift, drag, moment, shock position and critical Mach number. Since there are many problems in directly measuring the aerodynamic force of the airfoil with a balance, the more common test method at present is to place the airfoil model horizontally in the test section supported on the two side walls of the test section, and then to obtain the aerodynamic force of the airfoil by measuring the pressure distribution of the center section of the airfoil model and by integration. The principle of airfoil test is a two-dimensional flow-based aerodynamic performance measurement test, which requires that the two-dimensionality of the model surface flow be ensured, that is, the occurrence of lateral flow of the air current on the surface of the airfoil model should be avoided, which requires that after the airfoil model is loaded, the deformation of the airfoil model should not destroy the two-dimensionality of the air current flow on the model surface. At the same time, since the airfoil model is supported on the two side walls of the test section, the presence of the test section side wall inevitably brings about the interference of the side wall, and the too large interference area of the side wall may affect the accuracy of the pressure distribution measurement of the center section of the airfoil model.

[0003] In order to ensure the rigidity of the airfoil model so that the deformation of the model after being loaded does not destroy the two-dimensionality of the air current flow on the model surface, the thickness of the airfoil needs to be increased, and accordingly the chord length of the airfoil is also increased. The increase of the chord length inevitably leads to the increase of the interference area of the wind tunnel side wall, which may affect the accuracy of the pressure distribution measurement of the center section of the airfoil model, and the increase of the thickness and chord length of the airfoil model may lead to too large blockage of the model in the wind tunnel, which further affects the accurate control and simulation of the Mach number of the incoming flow in the test section. Ensuring the good rigidity of the airfoil model and minimizing the interference area of the wind tunnel wall are always contradictory. In engineering applications, the influence of the deformation of the model after being loaded needs to be considered when designing the airfoil model. The method is to give the thickness or chord length of the airfoil according to engineering experience, then to calculate the aerodynamic force of the airfoil under the given size, to check the rigidity of the model, to obtain the deformation under the given size, and then to compare the pressure distribution of the airfoil model after deformation with the pressure distribution before deformation through CFD numerical simulation until the difference between the pressure distribution after deformation and the pressure distribution before deformation is acceptable. Generally, there may be differences between the actual situation of the wind tunnel test and the theoretical calculation, especially in transonic test, the structure of the test section of the wind tunnel is very complex, and it is very difficult to accurately analyze and evaluate the interference of the wind tunnel wall through CFD numerical simulation, and it is often difficult to evaluate the reliability of the final test results.

[0004] In summary, when carrying out airfoil wind tunnel test, a method and structure for confirming the two-dimensionality of airfoil test and the interference area of wind tunnel side wall are needed. SUMMARY

[0005] The following presents a simplified summary of the application in order to provide a basic understanding of some aspects of the application. This summary is not an extensive overview of the application. It is not intended to identify key or critical elements of the application or to delineate the scope of the application. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

[0006] In view of this, in order to solve the problem that the conventional wind tunnel sidewall interference evaluation method for airfoil test in the prior art is difficult to accurately determine the wind tunnel interference range, the application provides a method and structure for confirming two-dimensionality of airfoil test and wind tunnel sidewall interference area.

[0007] Technical solution one is as follows: a method for confirming two-dimensionality of airfoil test and wind tunnel sidewall interference area, comprising the following steps:

[0008] S1. At least two positions on the upper surface of the airfoil model, a plurality of pressure measuring holes are arranged along the span from the center section of the airfoil model, and an airfoil model upper surface pressure measuring hole area is arranged.

[0009] S2. By analyzing the pressure distribution measurement results of the airfoil model upper surface pressure measuring hole area, according to the evaluation condition, the two-dimensionality of the airfoil test and the wind tunnel sidewall interference area range are confirmed.

[0010] Further, in S2, the evaluation condition is as follows: within a certain range close to the center section of the airfoil model in the span, the size of the spanwise pressure distribution on the upper surface of the airfoil model does not change, indicating that no spanwise flow occurs, confirming that the airfoil test has two-dimensionality, and the larger the region where the spanwise pressure distribution of the airfoil model does not change, the larger the two-dimensional region of the airfoil test; the range close to the wind tunnel sidewall and the airfoil model spanwise pressure distribution changes sharply, which is the wind tunnel sidewall interference area.

[0011] Technical solution two is as follows: a structure for confirming two-dimensionality of airfoil test and wind tunnel sidewall interference area, used to implement the method for confirming two-dimensionality of airfoil test and wind tunnel sidewall interference area according to technical solution one, comprising an airfoil model center section pressure measuring point area and an airfoil model upper surface pressure measuring hole area.

[0012] The pressure measuring points of the airfoil model center section pressure measuring point area are arranged along the center section of the airfoil model, the airfoil model upper surface is provided with at least two airfoil model upper surface pressure measuring hole areas, and the pressure measuring holes of the airfoil model upper surface pressure measuring hole area are arranged along the span of the airfoil model upper surface.

[0013] The beneficial effects of the present application are as follows: in the wing profile test in the wind tunnel, the present application sets several pressure measuring holes at least two positions on the upper surface of the wing profile model along the span to measure the spanwise pressure distribution on the upper surface of the model, the upper surface pressure distribution is sensitive to the change of the attitude of the wing profile model, the spanwise pressure measuring holes selected on the upper surface of the model can meet the evaluation requirement of the spanwise pressure distribution of the model under large load at large angle of attack; selecting at least two positions can ensure the reliability of the evaluation of the spanwise pressure distribution of the wing profile model; in the wing profile test in the wind tunnel, the present application quickly confirms the two-dimensionality of the wing profile test by evaluating the pressure distribution along the span set at least two positions on the upper surface of the wing profile model, and then accurately evaluates the reliability of the wind tunnel test result; the present application gives a method for quickly confirming the size of the wind tunnel side wall interference area of the wing profile test in the wind tunnel by evaluating the pressure distribution along the span set at least two positions on the upper surface of the wing profile model, and then accurately evaluating the reliability of the wind tunnel test result; in a certain range close to the wind tunnel side wall, the spanwise pressure distribution of the wing profile model will change sharply, and the change range is the wind tunnel side wall interference area, since the pressure measuring holes for wing profile pressure distribution measurement should be located in the two-dimensional area as far away from the wind tunnel side wall interference area as possible, the present application can also provide support for wing profile pressure distribution measurement. BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and serve to explain the principles of the application. In the drawings:

[0015] Fig. 1 It is a flow chart of a method for confirming the two-dimensionality of the wing profile test and the wind tunnel side wall interference area;

[0016] Fig. 2 It is a structural schematic diagram of a method for confirming the two-dimensionality of the wing profile test and the wind tunnel side wall interference area;

[0017] Fig. 3 It is a schematic diagram of the pressure distribution along the span of the wing profile model.

[0018] BRIEF DESCRIPTION OF DRAWINGS: 1. Wing profile model center section pressure measuring point area; 2. Wing profile model upper surface pressure measuring hole area; 3. Flow direction; 4. Wind tunnel side wall. DETAILED DESCRIPTION

[0019] In order to make the technical solutions and advantages in the embodiments of the present application clearer, the exemplary embodiments of the present application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0020] Embodiment 1: Reference Figs. 1-3 To explain this embodiment in detail, the method for confirming the two-dimensionality of airfoil test and the wind tunnel sidewall interference region specifically comprises the following steps:

[0021] S1. A plurality of pressure holes are arranged on the upper surface of the airfoil model at at least two positions along the span direction from the center section of the airfoil model, and the upper surface pressure hole region of the airfoil model is arranged.

[0022] S2. The two-dimensionality of the airfoil test and the range of the wind tunnel sidewall interference region are confirmed by analyzing the pressure distribution measurement results of the upper surface pressure hole region of the airfoil model and according to the evaluation condition.

[0023] Further, in S2, the evaluation condition is specifically as follows: within a certain range close to the center section of the airfoil model along the span direction, if the spanwise pressure distribution on the upper surface of the airfoil model does not change, it means that no spanwise flow occurs, and it is confirmed that the airfoil test has two-dimensionality. The larger the region where the spanwise pressure distribution of the airfoil model does not change is, the larger the two-dimensional region of the airfoil test is. The range close to the sidewall of the wind tunnel where the spanwise pressure distribution of the airfoil model changes sharply is the wind tunnel sidewall interference region.

[0024] Specifically, the deformation amount of the airfoil model along the span direction is different, and the pressure value changes. The airfoil model bears a larger load at a larger test angle of attack, and the deformation of the model is larger. Under the condition of larger deformation, the spanwise pressure distribution of the airfoil model still has a larger two-dimensional region, and the test result is more reliable. The pressure measurement points of the airfoil pressure distribution measurement should be located in the two-dimensional region as far away from the wind tunnel sidewall interference region as possible.

[0025] Embodiment 2: Reference Figs. 2-3 To explain this embodiment in detail, the structure for confirming the two-dimensionality of airfoil test and the wind tunnel sidewall interference region is used to realize the method for confirming the two-dimensionality of airfoil test and the wind tunnel sidewall interference region in Embodiment 1, and comprises an airfoil model center section pressure point region 1 and an airfoil model upper surface pressure hole region 2.

[0026] The pressure points of the airfoil model center section pressure point region 1 are arranged along the center section of the airfoil model. The airfoil model upper surface is provided with at least two airfoil model upper surface pressure hole regions 2, and the pressure holes of the airfoil model upper surface pressure hole region 2 are arranged along the span direction of the airfoil model upper surface.

[0027] Specifically, the airfoil model center section pressure point region 1 is the pressure point that should be arranged in the airfoil test, and the airfoil model upper surface pressure hole region 2 is arranged on one side of the airfoil model center section pressure point region 1 to quickly and accurately judge the two-dimensionality and the sidewall interference region.

[0028] Because the pressure distribution on the upper surface of the airfoil model is sensitive to the change of the airfoil model posture, the pressure holes arranged along the span are arranged on the upper surface of the airfoil model, and the pressure distribution along the span obtained is more illustrative. The upper surface of the airfoil model is provided with at least two positions to ensure the accuracy of the evaluation of the spanwise pressure distribution of the airfoil model. Referring to Fig. 2 In this example, the airfoil model is left-right symmetrical, and one side is arranged. Two positions of X / C=0.2 and X / C=0.4 are selected. The reason is that the thickness is relatively large, the pressure hole is easy to arrange, and the pressure distribution of the airfoil near the position is sensitive to various factors. The measurement result of the spanwise pressure distribution is more valuable. Wherein, X is the distance between the selected position and the leading edge of the airfoil, and C is the chord length of the airfoil. The direction 3 of the flow is towards the center section pressure point area 1 of the airfoil model.

[0029] Referring to Fig. 3 Cp is the pressure coefficient, and the horizontal coordinate 0 is the center section of the airfoil model. The spanwise pressure distribution results of the two positions of X / C=0.2 and X / C=0.4 show that within the range of 250mm from the center section of the airfoil model, the spanwise pressure distribution on the upper surface of the airfoil model does not change, that is, the range of 500mm from the center section of the airfoil model on the left and right is a two-dimensional area, Fig. 3 only one half of the two-dimensional area is shown; in the range close to the side wall 4 of the wind tunnel, the spanwise pressure distribution of the airfoil model changes sharply outside the range of 250mm from the center section of the airfoil model, that is, the wind tunnel side wall interference area, M is the Mach number, and a is the attack angle.

[0030] The present application accurately obtains the two-dimensional area and the wind tunnel side wall interference area of the airfoil test. The pressure distribution measurement of the airfoil is arranged in the two-dimensional area, so that the test result is more reliable.

[0031] Although the present application is described according to a limited number of embodiments, those skilled in the art, with the benefit of the above description, will appreciate that other embodiments can be conceived within the scope of the application described herein. In addition, it should be noted that the language used in the specification is mainly selected for readability and teaching purposes, rather than for interpretation or limitation of the subject matter of the application. Therefore, many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present application is illustrative rather than limiting, and the scope of the present application is defined by the appended claims.

Claims

1. A method for confirming the two-dimensionality of airfoil testing and the interference zone of wind tunnel sidewalls, characterized in that, Includes the following steps: S1. At least two locations on the upper surface of the airfoil model, several pressure measuring holes are set along the spanwise direction, starting from the center section of the airfoil model, to form a pressure measuring hole area on the upper surface of the airfoil model; S2. By analyzing the pressure distribution measurement results in the pressure measurement hole area on the upper surface of the airfoil model, and based on the evaluation conditions, the two-dimensionality of the airfoil test and the range of the wind tunnel sidewall interference zone are confirmed; In S2, the evaluation conditions are as follows: within a certain range of the airfoil model's central section in the spanwise direction, if the spanwise pressure distribution on the upper surface of the airfoil model remains unchanged, it indicates that no spanwise flow occurs, confirming that the airfoil test has a two-dimensional nature. The larger the area where the spanwise pressure distribution of the airfoil model remains unchanged, the larger the two-dimensional region of the airfoil test is. The range near the wind tunnel sidewall where the spanwise pressure distribution of the airfoil model changes drastically is the wind tunnel sidewall interference zone.

2. A structure for confirming the two-dimensionality of airfoil testing and the interference zone of the wind tunnel sidewall, characterized in that, The method for confirming the two-dimensionality of an airfoil test and the interference zone of the wind tunnel sidewall as described in claim 1 includes a pressure measurement point area (1) on the center section of the airfoil model and a pressure measurement hole area (2) on the upper surface of the airfoil model. The pressure measurement points of the pressure measurement point area (1) of the airfoil model center section are set along the airfoil model center section, and at least two airfoil model upper surface pressure measurement hole areas (2) are set on the airfoil model upper surface, and the pressure measurement holes of the airfoil model upper surface pressure measurement hole areas (2) are set along the span of the airfoil model upper surface.

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