Flow field aerodynamic characteristic wind tunnel test method for aircraft head circular seam

Abstract

The invention provides a flow field aerodynamic characteristic wind tunnel test method for an aircraft head circular seam. The method comprises the following steps: constructing an equivalent scaling test model; determining the flow field aerodynamic characteristics of the equivalent scaling test model; constructing a simplified test model; determining flow field aerodynamic characteristics of the simplified test model; and determining whether the surface pressure distribution difference of the same position in the two models is within a preset range, and under the condition that the surface pressure distribution difference is within the preset range, taking the simplified test model as a test model of an aircraft head to carry out a wind tunnel test. The equivalent scaling test model of the aircraft head is constructed, the circular nozzle is used for simplifying the circular seam, the flow field aerodynamic characteristics of the two test models are analyzed, the simplified test model with the same flow field aerodynamic characteristics as the equivalent scaling test model is used for performing the wind tunnel test, and the result is used as the wind tunnel test result of the aircraft head. And the subsequent optimization process can be realized conveniently.

Description

Technical Field

[0001] The present disclosure relates to the technical field of aircraft testing, and in particular to a wind tunnel testing method and device for a flow field aerodynamic characteristics of an aircraft head annular gap. Background Art

[0002] As a means of active flow control, the reverse jet at the head of the aircraft interacts with the incoming flow to change the flow field structure of the aircraft head, and is widely used in the design of drag reduction and heat reduction of high-speed aircraft. Domestic and foreign scholars have conducted a lot of research on the layout form and jet parameters of the reverse jet at the head of high-speed aircraft. The interaction between the reverse jet and the external flow causes significant changes in the surface and spatial flow of the aircraft head. It is necessary to accurately predict the drag reduction and heat reduction efficiency of the reverse jet. Wind tunnel tests and numerical predictions are important means to provide the above results. Wind tunnel tests are also an important way to verify the simulation accuracy of numerical methods and guide their improvement directions.

[0003] The reverse jet of the annular gap on the aircraft head is a typical reverse jet layout. The gap width is generally less than 1 mm. Under the existing wind tunnel size conditions, the annular gap size of the scaled model is too small and faces the problem of being unable to be directly processed, resulting in the inability to conduct corresponding wind tunnel tests, which affects the optimization process of the aircraft head. Summary of the invention

[0004] The purpose of the embodiments of the present disclosure is to provide a wind tunnel test method and device for the aerodynamic characteristics of the flow field of the aircraft head annular gap, so as to solve the problem that there is no wind tunnel test design method for the aerodynamic characteristics of the jet of the aircraft head annular gap in the prior art.

[0005] The embodiment of the present disclosure adopts the following technical scheme: a wind tunnel test method for flow field aerodynamic characteristics of an annular gap of an aircraft head, comprising: reducing the aircraft head according to a preset scaling ratio to form an equivalent scaled test model; determining the flow field aerodynamic characteristics of the equivalent scaled test model under wind tunnel test conditions; simplifying the annular gap in the equivalent scaled test model into N circumferentially uniformly distributed circular nozzles to form a simplified test model, where N is a positive integer; determining the flow field aerodynamic characteristics of the simplified test model under the wind tunnel test conditions; determining whether the difference in surface pressure distribution at the same position in the two models is within a preset range based on the flow field aerodynamic characteristics of the equivalent scaled test model and the flow field aerodynamic characteristics of the simplified test model, and if the surface pressure distribution difference is within the preset range, using the simplified test model as the test model of the aircraft head to carry out a wind tunnel test; if the surface pressure distribution difference is not within the preset range, adjusting the number and cross-sectional area of ​​the circular nozzles until the surface pressure distribution difference is within the preset range.

[0006] In some embodiments, it also includes: calculating the cross-sectional area of ​​the annular gap in the equivalent scaled test model so that the sum of the cross-sectional areas of all the circular nozzles is the same as the cross-sectional area of ​​the annular gap.

[0007] In some embodiments, N is an even number greater than or equal to 8.

[0008] In some embodiments, the flow field aerodynamic characteristics of the equivalent scaled-down test model and the simplified test model are both determined based on numerical simulation methods.

[0009] In some embodiments, the turbulence model in the numerical simulation method adopts the SA model, and the control equation adopts the three-dimensional compressible Reynolds-averaged Navier-Stokes equation. Based on the turbulence model and boundary conditions, the control equation is discretized to obtain discrete terms and discretized control equations; the discretized control equations are solved based on the discrete terms to obtain discrete values ​​of the aerodynamic characteristics of the flow field.

[0010] In some embodiments, the discrete terms include at least: discrete convection terms, discrete viscosity terms and discrete time terms; wherein the discrete convection terms are represented by the Roe format with second-order accuracy, the discrete viscosity terms are represented by the central difference format, and the discrete time terms are represented by the LU-SGS implicit method.

[0011] In some embodiments, the centers of the N circular nozzles are located on the center line of the simplified front annular seam, and the N circular nozzles are distributed in a centrally symmetrical manner.

[0012] The embodiment of the present disclosure also provides a wind tunnel test device for the flow field aerodynamic characteristics of the annular gap of the aircraft head, including: an equivalent model construction module, used to reduce the aircraft head according to a preset scaling ratio to form an equivalent scaled test model; a first determination module, used to determine the flow field aerodynamic characteristics of the equivalent scaled test model under wind tunnel test conditions; a simplified model construction module, used to simplify the annular gap in the equivalent scaled test model into N circumferentially uniformly distributed circular nozzles to form a simplified test model, where N is a positive integer; a second determination module, used to determine the simplified model under the wind tunnel test conditions. aerodynamic characteristics of the flow field of the test model; a test model optimization module, used to determine whether the difference in surface pressure distribution at the same position in the two models is within a preset range based on the aerodynamic characteristics of the flow field of the equivalent scaled test model and the aerodynamic characteristics of the flow field of the simplified test model; when the difference in surface pressure distribution is within the preset range, using the simplified test model as the test model of the aircraft head to carry out wind tunnel testing; when the difference in surface pressure distribution is not within the preset range, adjusting the number and cross-sectional area of ​​the circular nozzles until the difference in surface pressure distribution is within the preset range.

[0013] The beneficial effects of the embodiments of the present disclosure are: constructing an equivalent scaled test model of the aircraft head, and simplifying the annular gap by using a circular nozzle, analyzing the flow field aerodynamic characteristics of the two test models, and using a simplified test model with the same flow field aerodynamic characteristics as the equivalent scaled test model to carry out wind tunnel tests, which are used as the wind tunnel test results of the aircraft head, to facilitate the subsequent optimization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0015] Figure 1 This is a flow chart of a wind tunnel test method for aerodynamic characteristics of flow field of annular gap of aircraft head in the first embodiment of the present disclosure;

[0016] Figure 2 This is a schematic diagram of an equivalent scaled-down test model in the first embodiment of the present disclosure;

[0017] Figure 3 This is a simplified schematic diagram of the test model in the first embodiment of the present disclosure;

[0018] Figure 4 It is a schematic structural diagram of a wind tunnel test of aerodynamic characteristics of flow field of annular gap of aircraft head in the second embodiment of the present disclosure. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the following will be combined with the drawings in one or more embodiments of this specification to clearly and completely describe the technical solutions in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this document.

[0020] As a means of active flow control, the reverse jet at the head of the aircraft interacts with the incoming flow to change the flow field structure of the aircraft head, and is widely used in the design of drag reduction and heat reduction of high-speed aircraft. Domestic and foreign scholars have conducted a lot of research on the layout form and jet parameters of the reverse jet at the head of high-speed aircraft. The interaction between the reverse jet and the external flow causes significant changes in the surface and spatial flow of the aircraft head. It is necessary to accurately predict the drag reduction and heat reduction efficiency of the reverse jet. Wind tunnel tests and numerical predictions are important means to provide the above results. Wind tunnel tests are also an important way to verify the simulation accuracy of numerical methods and guide their improvement directions.

[0021] The reverse jet of the annular gap on the aircraft head is a typical reverse jet layout. The gap width is generally less than 1 mm. Under the existing wind tunnel size conditions, the annular gap size of the scaled model is too small and faces the problem of being unable to be directly processed, resulting in the inability to conduct corresponding wind tunnel tests, which affects the optimization process of the aircraft head.

[0022] In order to solve the above problems, the first embodiment of the present disclosure provides a wind tunnel test method for aerodynamic characteristics of flow field of annular gap of aircraft head, and the flow chart thereof is as follows: Figure 1 As shown, it mainly includes steps S10 to S50:

[0023] S10, reducing the head of the aircraft according to a preset scaling ratio to form an equivalent scaled test model;

[0024] S20, under wind tunnel test conditions, determine the flow field aerodynamic characteristics of the equivalent scaled test model;

[0025] S30, simplifying the annular gap in the equivalent scaled test model into N circular nozzles uniformly distributed in the circumferential direction to form a simplified test model, where N is a positive integer;

[0026] S40, determine the aerodynamic characteristics of the flow field of the simplified test model under wind tunnel test conditions;

[0027] S50, based on the flow field aerodynamic characteristics of the equivalent scaled test model and the flow field aerodynamic characteristics of the simplified test model, determine whether the difference in surface pressure distribution at the same position in the two models is within a preset range; when the surface pressure distribution difference is within the preset range, use the simplified test model as the test model of the aircraft head to carry out a wind tunnel test; when the surface pressure distribution difference is not within the preset range, adjust the number and / or cross-sectional area of ​​the circular nozzles until the surface pressure distribution difference is within the preset range.

[0028] In this embodiment, the preset scaling ratio can be set according to the actual size of the aircraft head and the size of the wind tunnel, and this embodiment does not limit the size of the specific scaling value. Figure 2As shown, after the aircraft head is scaled, the annular gap size in the equivalent scaled test model is usually less than 1 mm, and the actual preparation process cannot meet the preparation requirements of annular gaps of corresponding sizes. Therefore, by simplifying the equivalent scaled test model, a simplified test model that is easy to process and has the same flow field aerodynamic characteristics as the equivalent scaled test model is obtained as the test subject of the aircraft head wind tunnel test.

[0029] After the equivalent scaled test model is determined, the flow aerodynamic characteristics of the model are determined under wind tunnel test conditions to serve as the basis for selecting a simplified test model. Subsequently, the annular seam in the equivalent scaled test model is simplified to N circumferentially evenly distributed circular nozzles, and the simplified test model is constructed by taking advantage of the convenient processing characteristics of the circular nozzles. Figure 3 As shown, the value of N is a positive integer, and a specific number of circular nozzles are designed to make it have the same flow field aerodynamic characteristics as the equivalent scaled test model.

[0030] Specifically, when simplifying the equivalent scaled test model, the cross-sectional area S of the annular gap in the equivalent scaled test model can be determined first, and then the value of N can be determined based on the cross-sectional area of ​​the circular nozzles that can be achieved by the current process, so that the sum of the cross-sectional areas of all circular nozzles is the same as the cross-sectional area S of the annular gap in the equivalent scaled test model. It should be noted that the value of N is preferably set to an even number greater than or equal to 8, so as to achieve uniform distribution of multiple circular nozzles in the circumferential direction of the model head and restore better aircraft characteristics.

[0031] In addition, considering the difficulty of preparation, this embodiment uses a circular nozzle to equal the annular seam, and the centers of the N circular nozzles arranged on the model are located on the center line of the annular seam before simplification, and all the circular nozzles are centrally symmetrically distributed to restore the aerodynamic characteristics of the flow field of the aircraft head with annular seams. In some embodiments, the simplified nozzle can also be implemented by an elliptical nozzle, but it cannot be implemented by a polygonal nozzle. The angle between adjacent straight edges will cause the aerodynamic characteristics of the position to change, and it is impossible to completely restore the aerodynamic characteristics of the flow field of the equivalent scaled test model. At the same time, it is impossible to perfectly restore specific angles when preparing a physical model.

[0032] In the actual design process, a set of circular nozzle cross-sectional area and number N can be preferentially selected to determine the flow field aerodynamic characteristics of the simplified test model under the same wind tunnel test conditions. It should be understood that both the flow field aerodynamic characteristics of the equivalent scaled test model and the flow field aerodynamic characteristics of the simplified test model can be determined by numerical simulation, and in order to eliminate the influence of other variables on the analysis results, the simulation process of the numerical simulation method used for the flow field aerodynamic characteristics of the two should be completely consistent.

[0033] In some embodiments, the turbulence model in the numerical simulation method can use the SA model, and the control equation uses the three-dimensional compressible Reynolds-averaged Navier-Stokes equation. Based on the turbulence model and boundary conditions, the control equation is discretized to obtain discrete terms and the discretized control equation; the discretized control equation is solved based on the discrete terms to obtain the discrete values ​​of the aerodynamic characteristics of the flow field; finally, the aerodynamic characteristics of the flow field of the corresponding model can be determined through numerical analysis, feature extraction and other operations. Among them, the discrete terms at least include: convective term discretization, viscous term discretization and time term discretization; among them, the convective term discretization is expressed in the second-order accuracy Roe format, the viscous term discretization is expressed in the central difference format, and the time term discretization uses the LU-SGS implicit method.

[0034] Generally, the aerodynamic characteristics of the flow field include, but are not limited to, force and moment, surface pressure distribution, flow structure, turbulence characteristics, heat transfer characteristics, etc. The aerodynamic characteristics of the flow field concerned in this embodiment are mainly surface pressure distribution. In this embodiment, according to the aerodynamic characteristics of the flow field of the equivalent scaled test model and the aerodynamic characteristics of the flow field of the simplified test model, it can be determined whether the difference in surface pressure distribution at the same position in the two models is within a preset range, and the above preset range can be limited to ±1%; when the difference in surface pressure distribution is within the preset range, the simplified test model can be directly used as the test model of the aircraft head to carry out wind tunnel tests; when the difference in surface pressure distribution is not within the preset range, the number and cross-sectional area of ​​the circular nozzles are adjusted until the difference in surface pressure distribution is within the preset range, and the simplified test model that finally meets the conditions is used as the test model of the aircraft head to carry out wind tunnel tests.

[0035] It should be noted that when adjusting the number and cross-sectional area of ​​the circular nozzles, it should be ensured that the size of the circular nozzles meets the limitations of the preparation process during preparation and meets the value limit of N. In addition, if there are multiple sets of simplified test models corresponding to the cross-sectional area and N value, and the difference in surface pressure distribution at the same position of the equivalent scaled test model is within the preset range, the simplified test model corresponding to the set of data with the largest N value and the smallest circular nozzle cross-sectional area is selected to make the design of the circular nozzle as close as possible to the design of the annular gap, so as to obtain more accurate aerodynamic characteristics of the flow field.

[0036] In this embodiment, an equivalent scaled-down test model of the aircraft head is constructed, and the annular gap is simplified by using a circular nozzle. By analyzing the flow field aerodynamic characteristics of the two test models, a simplified test model with the same flow field aerodynamic characteristics as the equivalent scaled-down test model is used to carry out wind tunnel tests, which are used as the wind tunnel test results of the aircraft head to facilitate the subsequent optimization process of the aircraft head.

[0037] Based on the same inventive concept, the second embodiment of the present disclosure provides a wind tunnel test device for the flow field aerodynamic characteristics of the aircraft head annular gap, and its structural schematic diagram is shown as follows: Figure 4 As shown, it mainly includes: an equivalent model construction module 10 is used to reduce the head of the aircraft according to a preset scaling ratio to form an equivalent scaled test model; a first determination module 20 is used to determine the flow field aerodynamic characteristics of the equivalent scaled test model under wind tunnel test conditions; a simplified model construction module 30 is used to simplify the annular gap in the equivalent scaled test model into N circumferentially uniformly distributed circular nozzles to form a simplified test model, where N is a positive integer; a second determination module 40 is used to determine the flow field aerodynamic characteristics of the simplified test model under wind tunnel test conditions; and a test model optimization module 50 is used to determine whether the difference in surface pressure distribution at the same position in the two models is within a preset range based on the flow field aerodynamic characteristics of the equivalent scaled test model and the flow field aerodynamic characteristics of the simplified test model. If the surface pressure distribution difference is within the preset range, the simplified test model is used as the test model of the aircraft head to carry out wind tunnel tests; if the surface pressure distribution difference is not within the preset range, the number and cross-sectional area of ​​the circular nozzles are adjusted until the surface pressure distribution difference is within the preset range.

[0038] In some embodiments, the first determination module 20 is further used to calculate the cross-sectional area of ​​the annular gap in the equivalent scaled test model so that the sum of the cross-sectional areas of all the circular nozzles is the same as the cross-sectional area of ​​the annular gap.

[0039] In some embodiments, N is an even number greater than or equal to 8.

[0040] In some embodiments, the first determination module 20 and the second determination module 40 both determine the flow field aerodynamic characteristics of the equivalent scaled test model and the simplified test model based on the numerical simulation method. Specifically, the turbulence model in the numerical simulation method uses the SA model, and the control equation uses the three-dimensional compressible Reynolds-averaged Navier-Stokes equation. Based on the turbulence model and boundary conditions, the control equation is discretized to obtain discrete terms and the discretized control equation; the discretized control equation is solved based on the discrete terms to obtain the discrete values ​​of the flow field aerodynamic characteristics. The discrete terms include at least: convective term discretization, viscous term discretization and time term discretization; wherein, the convective term discretization is represented by the second-order precision Roe format, the viscous term discretization is represented by the central difference format, and the time term discretization uses the LU-SGS implicit method.

[0041] In some embodiments, the simplified model building module 30 places the centers of the N circular nozzles on the center line of the simplified front annular seam, and the N circular nozzles are distributed in a centrally symmetrical manner.

[0042] In this embodiment, the test model optimization module 50 can determine whether the difference in surface pressure distribution at the same position in the two models is within a preset range based on the flow field aerodynamic characteristics of the equivalent scaled test model and the flow field aerodynamic characteristics of the simplified test model. The above preset range can be limited to ±1%; when the surface pressure distribution difference is within the preset range, the simplified test model can be directly used as the test model of the aircraft head to carry out wind tunnel tests; when the surface pressure distribution difference is not within the preset range, the test model optimization module 50 instructs the simplified model construction module 30 to adjust the number and cross-sectional area of ​​the circular nozzles, and re-determines the flow field aerodynamic characteristics of the adjusted simplified model through the second determination module 40 until the surface pressure distribution difference is within the preset range, and the simplified test model that finally meets the conditions is used as the test model of the aircraft head to carry out wind tunnel tests.

[0043] It should be noted that when the simplified model building module 30 adjusts the number and cross-sectional area of ​​the circular nozzles, it should ensure that the size of the circular nozzles meets the limitations of the manufacturing process during preparation and meets the value limit of N. In addition, if there are multiple sets of simplified test models corresponding to the cross-sectional area and N value, and the difference in surface pressure distribution at the same position of the equivalent scaled test model is within the preset range, the test model optimization module 50 selects the simplified test model corresponding to a set of data with the largest N value and the smallest cross-sectional area of ​​the circular nozzle, so as to make the design of the circular nozzle as close to the design of the annular gap as possible, and obtain more accurate aerodynamic characteristics of the flow field.

[0044] In this embodiment, an equivalent scaled-down test model of the aircraft head is constructed, and the annular gap is simplified by using a circular nozzle. By analyzing the flow field aerodynamic characteristics of the two test models, a simplified test model with the same flow field aerodynamic characteristics as the equivalent scaled-down test model is used to carry out wind tunnel tests, which are used as the wind tunnel test results of the aircraft head to facilitate the subsequent optimization process of the aircraft head.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure 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 by 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 disclosure.

Claims

1. A wind tunnel test method for aerodynamic characteristics of flow field of annular gap of aircraft head, characterized in that: include: According to the preset scaling ratio, the aircraft head is reduced to form an equivalent scaled test model; Under wind tunnel test conditions, determining the flow field aerodynamic characteristics of the equivalent scaled test model; The annular gap in the equivalent scaled test model is simplified into N circular nozzles uniformly distributed in the circumferential direction to form a simplified test model, where N is a positive integer; Under the wind tunnel test conditions, determining the aerodynamic characteristics of the flow field of the simplified test model; Determine whether the difference in surface pressure distribution at the same position in the two models is within a preset range according to the flow field aerodynamic characteristics of the equivalent scaled test model and the flow field aerodynamic characteristics of the simplified test model, and if the difference in surface pressure distribution is within the preset range, use the simplified test model as the test model of the aircraft head to carry out a wind tunnel test; When the surface pressure distribution difference is not within the preset range, the number and cross-sectional area of ​​the circular nozzles are adjusted until the surface pressure distribution difference is within the preset range.

2. The flow field aerodynamic characteristics wind tunnel test method according to claim 1, characterized in that: Also includes: The cross-sectional area of ​​the annular gap in the equivalent scaled test model is calculated so that the sum of the cross-sectional areas of all the circular nozzles is the same as the cross-sectional area of ​​the annular gap.

3. The flow field aerodynamic characteristics wind tunnel test method according to claim 1, characterized in that: N is an even number greater than or equal to 8.

4. The flow field aerodynamic characteristics wind tunnel test method according to claim 1, characterized in that: The flow field aerodynamic characteristics of the equivalent scaled-down test model and the simplified test model are both determined based on a numerical simulation method.

5. The flow field aerodynamic characteristics wind tunnel test method according to claim 4, characterized in that: In the numerical simulation method, the SA model is selected as the turbulence model, and the three-dimensional compressible Reynolds-averaged Navier-Stokes equation is used as the control equation. Based on the turbulence model and boundary conditions, the control equation is discretized to obtain discrete terms and the discretized control equation; the discretized control equation is solved based on the discrete terms to obtain the discrete values ​​of the aerodynamic characteristics of the flow field.

6. The flow field aerodynamic characteristics wind tunnel test method according to claim 5, characterized in that: The discrete items include at least: discrete convection items, discrete viscosity items and discrete time items; wherein the discrete convection items are represented by the second-order accurate Roe format, the discrete viscosity items are represented by the central difference format, and the discrete time items are represented by the LU-SGS implicit method.

7. The wind tunnel test method for flow field aerodynamic characteristics according to any one of claims 1 to 6, characterized in that: The centers of the N circular nozzles are located on the center line of the simplified front annular seam, and the N circular nozzles are distributed in a centrally symmetrical manner.

8. A wind tunnel test device for the flow field aerodynamic characteristics of the aircraft head annular gap, characterized in that: include: An equivalent model building module is used to reduce the aircraft head according to a preset scaling ratio to form an equivalent scaled test model; A first determination module is used to determine the aerodynamic characteristics of the flow field of the equivalent scaled test model under wind tunnel test conditions; A simplified model building module, used for simplifying the annular gap in the equivalent scaled test model into N circular nozzles uniformly distributed in the circumferential direction to form a simplified test model, where N is a positive integer; A second determination module is used to determine the aerodynamic characteristics of the flow field of the simplified test model under the wind tunnel test conditions; A test model optimization module, for determining whether the difference in surface pressure distribution at the same position in the two models is within a preset range according to the flow field aerodynamic characteristics of the equivalent scaled test model and the flow field aerodynamic characteristics of the simplified test model, and using the simplified test model as the test model of the aircraft head to carry out a wind tunnel test when the difference in surface pressure distribution is within the preset range; When the surface pressure distribution difference is not within the preset range, the number and cross-sectional area of ​​the circular nozzles are adjusted until the surface pressure distribution difference is within the preset range.

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