A method for uncertainty analysis of drag measurement of high-speed wind tunnel airfoil models

Abstract

The present invention belongs to the technical field of high-speed wind tunnel tests, and discloses a method for analyzing the uncertainty of drag measurement of a high-speed wind tunnel airfoil model. The method for analyzing the uncertainty of drag measurement of a high-speed wind tunnel airfoil model of the present invention comprises the following steps: installing an airfoil model and a wake rake; conducting a high-speed wind tunnel airfoil model drag measurement test; calculating the static pressure of the incoming flow of the high-speed wind tunnel; and calculating the uncertainty of drag measurement of the high-speed wind tunnel airfoil model. The method for analyzing the uncertainty of drag measurement of a high-speed wind tunnel airfoil model of the present invention, through rigorous theoretical derivation and high-speed wind tunnel tests, uses an uncertainty transfer method to establish a method for analyzing the uncertainty of drag measurement of a high-speed wind tunnel airfoil model, which can provide reliable uncertainty of drag measurement of an airfoil model, thereby improving the reliability of high-speed wind tunnel test results, and has engineering application value.

Description

Technical Field

[0001] The invention belongs to the technical field of high-speed wind tunnel tests, and in particular relates to a method for analyzing uncertainty in drag measurement of a high-speed wind tunnel airfoil model. Background Art

[0002] As we all know, the wing is the main component of the aircraft to generate lift, and the two-dimensional airfoil is an important part of wing forming and a basic element of wing aerodynamic shape design. The aerodynamic characteristics of the two-dimensional airfoil directly affect the aerodynamic characteristics of the wing, the aircraft's cruising speed, take-off and landing performance, stall angle of attack and speed, handling quality and even the aerodynamic efficiency of all flight stages. Therefore, the two-dimensional airfoil is also called the heart of the aircraft and plays an important role in aerodynamic theory and aircraft design.

[0003] Wing drag is an important component of the drag experienced by an aircraft during cruising. Wing drag reduction design, especially two-dimensional airfoil drag reduction design, is an important aerodynamic design method to achieve the above development goals. In order to verify the effectiveness of two-dimensional airfoil drag reduction design, it is particularly important to accurately quantify and evaluate the airfoil drag coefficient.

[0004] Before the 1970s, the precise measurement of airfoil drag coefficient mainly relied on wind tunnel tests. With the development of computer technology and computational aerodynamics, although numerical simulation methods can be used to accurately design airfoils according to target pressure distribution and accurately measure airfoil drag, it is still inseparable from the typical state verification test of airfoil drag using wind tunnel tests. According to currently available literature, the principle of the drag coefficient measurement test of low-speed wind tunnel airfoil models is simple and the method is mature. However, for high-speed wind tunnels, due to the existence of compressibility, the principle of the drag coefficient measurement test of high-speed wind tunnel airfoil models is complex, and the drag coefficient solution methods in different literatures are inconsistent, which limits the accuracy of the drag coefficient measurement of high-speed wind tunnel airfoil models. In addition, the existing methods for solving the drag coefficient of high-speed wind tunnel airfoil models have not evaluated the uncertainty of their measurement results, resulting in the inability to evaluate the reliability of high-speed wind tunnel test results, which seriously restricts the safety and economy of aircraft.

[0005] Currently, there is an urgent need to develop an uncertainty analysis method for drag measurement of high-speed wind tunnel airfoil models. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for analyzing the uncertainty of drag measurement of a high-speed wind tunnel airfoil model.

[0007] The uncertainty analysis method of the high-speed wind tunnel airfoil model drag measurement of the present invention comprises the following steps:

[0008] S10. Install the airfoil model and wake rake;

[0009] The airfoil model is connected to the rotating window mechanism and fixedly installed in the high-speed wind tunnel test section, the wake rake is fixed on the middle bracket, and the pressure measuring point on the wake rake is connected to the pressure scanning valve through a hose;

[0010] S20. Conduct drag measurement test of high-speed wind tunnel airfoil model;

[0011] Open the high-speed wind tunnel and set the incoming Mach number After the flow field stabilizes, the total pressure of the wake of the airfoil model is measured using a pressure scanning valve. 、Airfoil model wake static pressure , and simultaneously measure the total pressure in the stable section of the wind tunnel ,in, i is the total pressure measurement point number on the wake rake, N is the total number of pressure measurement points on the wake rake;

[0012] S30. Calculation of static pressure of high-speed wind tunnel inflow ;

[0013] According to the incoming flow Mach number and total pressure in the stable section of the wind tunnel , calculate the static pressure of the incoming flow :

[0014] ,

[0015] In the formula, is the specific heat ratio of gases;

[0016] S40. Calculation of the uncertainty of drag measurement for high-speed wind tunnel airfoil models ;

[0017] According to the drag coefficient of the high-speed wind tunnel airfoil model Numerical integration equation for :

[0018] ,

[0019] In the formula, c is the chord length of the airfoil model, is the vertical length corresponding to the total pressure measurement point of the airfoil model wake, and the uncertainty of the drag measurement of the high-speed wind tunnel airfoil model is calculated. for:

[0020] ,

[0021] In the formula, for The uncertainty of for The uncertainty of for The uncertainty of for uncertainty.

[0022] Furthermore, the calculation uncertainty of the high-speed wind tunnel airfoil model drag measurement in step S40 is The calculation method of each individual uncertainty in is as follows:

[0023] S41. Calculation method of

[0024] Wake static pressure of airfoil model Uncertainty By measurement The pressure scanning valve is given by The calculation method is as follows:

[0025] ;

[0026] S42. Calculation method of

[0027] According to the static pressure of the incoming flow in step S30 The calculation method of Given by:

[0028] ,

[0029] Among them, the total pressure in the stable section of the wind tunnel is Uncertainty By measurement The pressure sensor gives the Mach number of the flow Uncertainty Given by the Mach number control accuracy of the high-speed wind tunnel, the corresponding coefficient The calculation methods are as follows:

[0030] ,

[0031] so, The calculation method is as follows:

[0032] ,

[0033] The corresponding coefficient The calculation method is as follows:

[0034] ;

[0035] S43. Calculation method of

[0036] Wake total pressure of airfoil model Uncertainty By measurement The pressure scanning valve is given by The calculation method is as follows:

[0037] ;

[0038] S44. Calculation method of

[0039] Total pressure in the wind tunnel steady section Uncertainty By measurement The pressure sensor gives the corresponding coefficient The calculation method is as follows:

[0040] .

[0041] The uncertainty analysis method for measuring the drag of a high-speed wind tunnel airfoil model of the present invention is established by rigorous theoretical derivation and high-speed wind tunnel tests, using the uncertainty transfer method. The method can provide reliable uncertainty in measuring the drag of a high-speed wind tunnel airfoil model, thereby improving the reliability of high-speed wind tunnel test results and having engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The present invention is a flow chart of the uncertainty analysis method for measuring drag of a high-speed wind tunnel airfoil model. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0044] Example: Figure 1 As shown, the high-speed wind tunnel airfoil model drag measurement uncertainty analysis method of this embodiment includes the following steps:

[0045] S10. Install the airfoil model and wake rake;

[0046] The airfoil model is connected to the rotating window mechanism and fixedly installed in the high-speed wind tunnel test section, the wake rake is fixed on the middle bracket, and the pressure measuring point on the wake rake is connected to the pressure scanning valve through a hose;

[0047] S20. Conduct drag measurement test of high-speed wind tunnel airfoil model;

[0048] Open the high-speed wind tunnel and set the incoming Mach number After the flow field stabilizes, the total pressure of the wake of the airfoil model is measured using a pressure scanning valve. 、Airfoil model wake static pressure , and simultaneously measure the total pressure in the stable section of the wind tunnel ,in, iis the total pressure measurement point number on the wake rake, N is the total number of pressure measurement points on the wake rake;

[0049] S30. Calculation of static pressure of high-speed wind tunnel inflow ;

[0050] According to the incoming flow Mach number and total pressure in the stable section of the wind tunnel , calculate the static pressure of the incoming flow :

[0051] ,

[0052] In the formula, is the specific heat ratio of gases;

[0053] S40. Calculation of the uncertainty of drag measurement for high-speed wind tunnel airfoil models ;

[0054] According to the drag coefficient of the high-speed wind tunnel airfoil model Numerical integration equation for :

[0055] ,

[0056] In the formula, c is the chord length of the airfoil model, is the vertical length corresponding to the total pressure measurement point of the airfoil model wake, and the uncertainty of the drag measurement of the high-speed wind tunnel airfoil model is calculated. for:

[0057] ,

[0058] In the formula, for The uncertainty of for The uncertainty of for The uncertainty of for uncertainty.

[0059] Furthermore, the calculation uncertainty of the high-speed wind tunnel airfoil model drag measurement in step S40 is The calculation method of each individual uncertainty in is as follows:

[0060] S41. Calculation method of

[0061] Wake static pressure of airfoil model Uncertainty By measurement The pressure scanning valve is given by The calculation method is as follows:

[0062] ;

[0063] S42. Calculation method of

[0064] According to the static pressure of the incoming flow in step S30 The calculation method of Given by:

[0065] ,

[0066] Among them, the total pressure in the stable section of the wind tunnel is Uncertainty By measurement The pressure sensor gives the Mach number of the flow Uncertainty Given by the Mach number control accuracy of the high-speed wind tunnel, the corresponding coefficient The calculation methods are as follows:

[0067] ,

[0068] so, The calculation method is as follows:

[0069] ,

[0070] The corresponding coefficient The calculation method is as follows:

[0071] ;

[0072] S43. Calculation method of

[0073] Wake total pressure of airfoil model Uncertainty By measurement The pressure scanning valve is given by The calculation method is as follows:

[0074] ;

[0075] S44. Calculation method of

[0076] Total pressure in the wind tunnel steady section Uncertainty By measurement The pressure sensor gives the corresponding coefficient The calculation method is as follows:

[0077] .

[0078] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and implementation modes. For those familiar with the art, all features disclosed in the present invention, or steps in all methods or processes disclosed, except for mutually exclusive features and / or steps, can be combined in any way without departing from the principles of the present invention. The present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for uncertainty analysis of drag measurement of a high-speed wind tunnel airfoil model, characterized in that: The following steps are involved: S10. Install the airfoil model and wake rake; The airfoil model is connected to the rotating window mechanism and fixedly installed in the high-speed wind tunnel test section, the wake rake is fixed on the middle bracket, and the pressure measuring point on the wake rake is connected to the pressure scanning valve through a hose; S20. Conduct high-speed wind tunnel airfoil model drag measurement test; Open the high-speed wind tunnel and set the incoming Mach number After the flow field stabilizes, the total pressure of the wake of the airfoil model is measured using a pressure scanning valve. 、Airfoil model wake static pressure , and simultaneously measure the total pressure in the stable section of the wind tunnel ,in, i is the total pressure measurement point number on the wake rake, N is the total number of pressure measurement points on the wake rake; S30. Calculation of static pressure of high-speed wind tunnel inflow ; According to the incoming flow Mach number and total pressure in the stable section of the wind tunnel , calculate the static pressure of the incoming flow : ， In the formula, is the specific heat ratio of gases; S40. Calculation of the uncertainty of drag measurement for high-speed wind tunnel airfoil models ; According to the drag coefficient of the high-speed wind tunnel airfoil model Numerical integration equation for : ， In the formula, c is the chord length of the airfoil model, is the vertical length corresponding to the total pressure measurement point of the airfoil model wake, and the uncertainty of the drag measurement of the high-speed wind tunnel airfoil model is calculated. for: ， In the formula, for The uncertainty of for The uncertainty of for The uncertainty of for uncertainty.

2. The high-speed wind tunnel airfoil model drag measurement uncertainty analysis method according to claim 1, characterized in that: The uncertainty of measuring the drag of the high-speed wind tunnel airfoil model in step S40 is calculated. The calculation method of each individual uncertainty in is as follows: S41. Calculation method of Wake static pressure of airfoil model Uncertainty By measurement The pressure scanning valve is given by The calculation method is as follows: ； S42. Calculation method of According to the static pressure of the incoming flow in step S30 The calculation method of Given by: ， Among them, the total pressure in the stable section of the wind tunnel is Uncertainty By measurement The pressure sensor gives the Mach number of the flow Uncertainty Given by the Mach number control accuracy of the high-speed wind tunnel, the corresponding coefficient The calculation methods are as follows: ， so, The calculation method is as follows: ， The corresponding coefficient The calculation method is as follows: ； S43. Calculation method of Wake total pressure of airfoil model Uncertainty By measurement The pressure scanning valve is given by The calculation method is as follows: ； S44. Calculation method of Total pressure in the wind tunnel steady section Uncertainty By measurement The pressure sensor gives the corresponding coefficient The calculation method is as follows: 。

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