A method for transport aircraft drag reduction based on dual-mode flow control

Abstract

The present invention provides a method for reducing drag on a transport aircraft based on bimodal flow control, comprising: designing multiple bimodal flow control structures based on transport aircraft parameters, and determining geometric characteristic parameters of each bimodal flow control structure, wherein the bimodal flow control structures include vortex generators and grooves; respectively setting multiple bimodal flow control structures on straight sections of the fuselage of an original transport aircraft model to generate multiple transport aircraft flow control models; and calculating the drag reduction rate of each transport aircraft flow control model based on the geometric characteristic parameters of the bimodal flow control structures, selecting the transport aircraft flow control model with the highest drag reduction rate as the final deceleration design model, and setting the final deceleration design model on the original transport aircraft model. The bimodal flow control structures can effectively reduce the wall friction resistance caused by the turbulent boundary layer, achieving a superior drag reduction effect under the same flow conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft design, and in particular to a transport aircraft drag reduction method based on dual-mode flow control. Background Art

[0002] Faced with the huge consumption and limited nature of oil resources, airlines around the world urgently need to develop a new generation of transport aircraft that saves fuel and can reach high, subsonic and even supersonic speeds. The key factor restricting this plan is how to reduce the total resistance of the transport aircraft.

[0003] In the field of air transport aircraft, frictional drag is the main drag component, accounting for approximately 50% of the total drag. For transport aircraft, a large amount of frictional drag is generated by the turbulent boundary layer attached to the surface. The fundamental way to reduce total drag is to reduce frictional drag. Most of the frictional drag on the fuselage surface is caused by the turbulent boundary layer. Therefore, without changing the aircraft's aerodynamic shape and frictional infiltration area, controlling the flow state within the turbulent boundary layer on the fuselage surface is most likely to bring significant drag reduction benefits, further improve the economic efficiency of air transport aircraft, and reduce fuel consumption and carbon emissions.

[0004] Traditional active / passive flow control methods for transport aircraft often rely on a single-structure flow control mechanism, resulting in relatively limited drag reduction effects and restricting their adaptability under different operating conditions. Traditional active / passive flow control methods for transport aircraft, which aim to reduce frictional drag, primarily focus on controlling small-scale flow structures near the wall within the turbulent boundary layer. However, as the Reynolds number increases, the contribution of small-scale flow structures within the turbulent boundary layer to turbulent kinetic energy and wall frictional drag gradually decreases, while the influence of large-scale flow structures within the turbulent boundary layer on wall frictional drag gradually increases, resulting in a decrease in the drag reduction effectiveness of traditional active / passive flow control methods for transport aircraft. Summary of the Invention

[0005] In view of this, an embodiment of the present specification provides a method for reducing drag of a transport aircraft based on dual-modal flow control, so as to achieve the purpose of enhancing the drag reduction effect of the transport aircraft.

[0006] The embodiments of this specification provide the following technical solutions:

[0007] A method for reducing drag of a transport aircraft based on dual-mode flow control, comprising:

[0008] Designing multiple sets of dual-mode flow control structures according to the parameters of the conveyor, and determining the geometric characteristic parameters of each set of dual-mode flow control structures, wherein the dual-mode flow control structures include vortex generators and grooves;

[0009] Multiple sets of dual-mode flow control structures are set on straight sections of the fuselage of the original transport aircraft model to generate multiple sets of transport aircraft flow control models;

[0010] According to the geometric characteristic parameters of the dual-mode flow control structure, the drag reduction rate of each group of conveyor flow control models is calculated respectively. The group of conveyor flow control models with the largest drag reduction rate is used as the final deceleration design model, and the final deceleration design model is set on the original conveyor model.

[0011] Furthermore, the geometric characteristic parameters include the height h of the vortex generator m , the width w of the vortex generator m , the length of the vortex generator l m , the spacing of vortex generators s m、 Groove height h r , the width of the groove s r and the length of the groove l r .

[0012] Furthermore, multiple sets of dual-mode flow control structures are respectively set on straight sections of the fuselage of the original transport aircraft model to generate multiple sets of transport aircraft flow control models, including:

[0013] Along the flow direction of the conveyor, the vortex generator of the dual-mode flow control structure is arranged upstream of the incoming flow, and the groove of the dual-mode flow control structure is installed downstream of the incoming flow, with the leading edge of the groove adjacent to the trailing edge of the vortex generator;

[0014] The vortex generators and the grooves are arranged in parallel along the span direction of the conveyor.

[0015] Furthermore, the drag reduction rate of each group of transport aircraft flow control models is calculated separately, including:

[0016] According to the requirements of numerical simulation efficiency and accuracy, the drag reduction prediction method is selected, among which the drag reduction prediction method includes RANS modeling numerical simulation method and WMLES direct numerical simulation method;

[0017] The total drag of the transport aircraft flow control model is calculated using the drag reduction prediction method.

[0018] The total drag of the original model of the transport aircraft is calculated using the drag reduction prediction method;

[0019] The drag reduction rate of the conveyor flow control model is calculated by the total drag of the conveyor flow control model and the total drag of the original conveyor model.

[0020] Furthermore, the total drag of the transport aircraft flow control model is calculated using the drag reduction prediction method, including:

[0021] If the drag reduction prediction method is the RANS modeling numerical simulation method, the total drag of the conveyor flow control model is obtained by calculating the geometric characteristic parameters of the original conveyor model and the dual-mode flow control structure;

[0022] If the drag reduction prediction method is the WMLES direct numerical simulation method, the total resistance of the conveyor flow control model is obtained by calculating the conveyor flow control model.

[0023] Furthermore, the total resistance of the conveyor flow control model is calculated by using the geometric characteristic parameters of the original conveyor model and the dual-mode flow control structure, including:

[0024] Meshing the original model of the transport aircraft to generate first mesh data;

[0025] Define flow control files through geometric feature parameters;

[0026] Setting a first calculation parameter file, wherein the first calculation parameter file includes a Mach number / Reynolds number, a reference area / chord length, and a calculation method;

[0027] Generate drag aerodynamic data by using the RANS modeling numerical simulation method through the flow control file, the first calculation parameter file and the first grid data;

[0028] The total resistance in the drag aerodynamic data is used as the total resistance of the transport aircraft flow control model.

[0029] Furthermore, the total resistance of the conveyor flow control model is calculated by the conveyor flow control model, including:

[0030] Meshing the conveyor flow control model to generate second mesh data;

[0031] Setting a second calculation parameter file, wherein the second calculation parameter file includes free flow initial variables, calculation reference parameters, and calculation method definition;

[0032] The total resistance of the transport aircraft flow control model is calculated using the second grid data and the second calculation parameter file and the RANS modeling numerical simulation method.

[0033] Furthermore, the drag reduction rate of the conveyor flow control model is calculated based on the total drag of the conveyor flow control model and the total drag of the original conveyor model, including:

[0034] Where, ΔC D is the drag reduction rate of the transport aircraft flow control model, C D_original is the total resistance of the original transport model, C D_control is the total resistance of the conveyor flow control model.

[0035] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0036] The dual-mode flow control structure can effectively reduce the wall friction resistance caused by the turbulent boundary layer, and achieve a better drag reduction effect under the same flow conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] Figure 1 is a flow chart of a transport aircraft drag reduction method based on dual-mode flow control according to an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of an original model of a transport aircraft according to an embodiment of the present invention;

[0040] Figure 3 is a partial rear view of a dual-mode flow control structure according to an embodiment of the present invention;

[0041] Figure 4 is a partial side view of a dual-mode flow control structure according to an embodiment of the present invention;

[0042] Figure 5 Schematic diagram of geometric characteristic parameters of a groove according to an embodiment of the present invention;

[0043] Figure 6 Schematic diagram of geometric characteristic parameters of a vortex generator according to an embodiment of the present invention;

[0044] Figure 7 is a schematic diagram of a dual-mode flow control structure according to an embodiment of the present invention disposed on a conveyor;

[0045] Figure 8 This is a schematic diagram of the drag reduction rate changing with the angle of attack. DETAILED DESCRIPTION

[0046] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0047] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0048] Because the dual-mode flow control structure couples grooves and vortex generators, it can simultaneously control both large-scale and small-scale turbulent energetic structures within the turbulent boundary layer. The grooves can control the small-scale flow structure near the wall, reducing the small-scale friction drag component it generates on the wall. The vortex generators can control the large-scale flow structure in the higher flow layer, reducing the large-scale friction drag component it generates on the wall. They can also control their modulation effect on the small-scale flow structure near the wall, further reducing the contribution of the small-scale flow structure to the wall friction drag. The dual-mode flow control structure can significantly reduce the wall friction drag caused by the turbulent boundary layer, achieving a superior drag reduction effect under the same flow conditions.

[0049] In one embodiment, a transport aircraft drag reduction design method based on dual-mode flow control is described. Figure 1 As shown, the following steps are included:

[0050] Step 1: Original 3D model of transport aircraft ( Figure 2 ) performs grid division to generate the second grid data, and RANS numerical simulation is performed to generate the aerodynamic data of the resistance.

[0051] like Figure 2 As shown, the original model of the transport aircraft (reference Figure 2 ) for grid division. All computational domains are divided into structured grids with about 17.96 million grid points, 37 grid points in the boundary layer, and a first-layer grid distance of about 1×10 -6 m (in step 1). The original model of the transport aircraft is numerically simulated by RANS to obtain the total drag coefficient C D_original .

[0052] Step 2: Establish a dual-mode flow control structure.

[0053] The dual-mode flow control structure includes at least one vortex generator ( Figure 3 and Figure 4 The large triangle on the Figure 3 The bimodal flow control structure is arranged such that the vortex generators are upstream of the incoming flow in the streamwise direction, and the leading edges of the grooves are adjacent to the trailing edges of the vortex generators, downstream of the incoming flow. In the spanwise direction, the vortex generators and grooves are arranged in parallel. The spanwise width of the bimodal flow control structure is less than the diameter of the original transport aircraft fuselage in a straight section, and the bimodal flow control structure's length in the streamwise direction is less than the length of the original transport aircraft fuselage in a straight section.

[0054] In one embodiment, 74 wedge-shaped vortex generators and 49,000 V-shaped symmetrical grooves form a dual-mode flow control structure. In the flow direction, the vortex generators are located upstream of the incoming flow, and the leading edge of the grooves is adjacent to the trailing edge of the vortex generators, which is located downstream of the incoming flow. In the span direction, the vortex generators and grooves are arranged in parallel without spacing, such as Figure 3 and Figure 4 .

[0055] Step three: establishing several sets of dual-mode flow control structures according to the geometric characteristic parameters, and installing the dual-mode flow control structures on the straight sections of the transport aircraft's fuselage.

[0056] The geometric characteristic parameters include the height h of the vortex generator m , the width w of the vortex generator m , the length of the vortex generator l m , the spacing of vortex generators s m、 Groove height h r , the width of the groove s r and the length of the groove l r Among them, the height of the vortex generator h m Less than 0.5 times the thickness of the turbulent boundary layer.

[0057] The geometric characteristic parameters of the first group of dual-mode flow control structures are as follows: Figure 5 and Figure 6 , h m =0.01m, w m =0.02m,l m =0.04m,s m =0m,h r =3×10 -5 m,s r =3×10 -5 m, l r =6m. Several other groups of dual-mode flow control structures are established by maintaining the principle of single-factor variation in height, width, length, and spacing, and satisfying the requirements that the spanwise width of the dual-mode flow control structure is less than 6.2m, the flowwise length is less than 36m, and the vortex generator structure height is less than 0.02m.

[0058] Step 4: Establish any one of the circulating conveyor flow control models (3d) among the conveyor flow control models.

[0059] The boundary layer of the original transport aircraft model fuselage transitions at a distance of 5.6m from the nose. At a distance of 12.0m from the nose, the first set of dual-mode flow control structures are installed in series along the flow direction on the straight section of the original transport aircraft model fuselage. A total of 6 structures are installed, such as Figure 7 shown.

[0060] Step 5: Select a drag reduction prediction method based on the required numerical simulation efficiency and accuracy. These methods include RANS modeling or WMLES direct numerical simulation. RANS modeling prioritizes numerical simulation efficiency and is suitable for engineering assessment applications. WMLES direct numerical simulation prioritizes flow field details and is more suitable for studying drag reduction mechanisms.

[0061] If the application is for engineering evaluation, the efficiency of numerical simulation is more important, so the RANS modeling numerical simulation method is selected. Prepare the input files: the original model calculation grid of the transport aircraft in step 1; the flow control file defining the geometric characteristic parameters of the first set of dual-mode flow control structure; Mach number 0.85, Reynolds number 5×10 6 , angle of attack 0°~5° and turbulence model k-ωSST and other main parameters. Output the first group of drag aerodynamic data: total drag C of transport flow control model D1_control .

[0062] If the drag reduction mechanism research focuses on the details of the flow field, the WMLES direct numerical simulation method is selected. Prepare the input file: mesh the flow control model of the first group of transport aircraft, and use structured grids for all calculation domains; Mach number 0.85, Reynolds number 5×10 6 , angle of attack 0°~5° and turbulence model k-ωSST and other main parameters. Output the total resistance C of the first group of transport aircraft flow control model D1_control .

[0063] Step 6: Repeat steps 4 and 5 to calculate the drag reduction rates of several groups of conveyor flow control models to obtain a better conveyor drag reduction method with a dual-mode flow control structure.

[0064] Calculate the drag reduction rate ΔC for the first group of transport aircraft flow control models D1 (like Figure 8 shown): Repeat steps 4 to 5 to calculate the drag reduction rate ΔC for the remaining groups of transport aircraft flow control models. D2 , ΔC D3 ..., comparing the set of dual-mode flow control structures with the higher overall drag reduction rate, and taking the set of dual-mode flow control structures with the largest drag reduction rate as the final result, the optimal dual-mode flow control drag reduction method for transport aircraft under the current calculation conditions was obtained. D_original is the total resistance of the original transport model, C D_control is the total resistance of the conveyor flow control model.

[0065] Beneficial effects of the embodiments of the present invention:

[0066] The dual-mode flow control structure, by coupling grooves and vortex generators, can simultaneously control both large-scale and small-scale turbulent energetic structures within the turbulent boundary layer. The grooves control the small-scale flow structure near the wall, reducing the small-scale friction drag component it generates on the wall. The vortex generators control the large-scale flow structure in the higher flow layer, reducing the large-scale friction drag component it generates on the wall. They also control their modulation of the small-scale flow structure near the wall, further reducing the contribution of the small-scale flow structure to wall friction drag. The dual-mode flow control structure can significantly reduce the wall friction drag caused by the turbulent boundary layer, achieving superior drag reduction under the same flow conditions.

[0067] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of patent protection, should still fall within the scope of this patent. Furthermore, the technical features of the present invention may be freely combined with one another, with other technical solutions, and with other technical solutions.

Claims

1. A method for reducing drag of a transport aircraft based on dual-mode flow control, characterized in that: include: Designing multiple sets of dual-mode flow control structures according to the parameters of the conveyor, and determining geometric characteristic parameters of each set of the dual-mode flow control structures, wherein the dual-mode flow control structures include vortex generators and grooves; arranging a plurality of sets of the dual-mode flow control structures on straight sections of the fuselage of the original transport aircraft model to generate a plurality of sets of transport aircraft flow control models; According to the geometric characteristic parameters of the dual-modal flow control structure, the drag reduction rate of each group of the conveyor flow control models is calculated respectively, and the group of conveyor flow control models with the largest drag reduction rate is used as the final deceleration design model, and the final deceleration design model is set on the original conveyor model.

2. The method for reducing drag of a transport aircraft based on dual-mode flow control according to claim 1, characterized in that: The geometric characteristic parameters include the height h of the vortex generator m , the width w of the vortex generator m , the length l of the vortex generator m , the spacing s of the vortex generators m、 The height h of the groove r , the width of the groove s r and the length l of the groove r .

3. The method for reducing drag of a transport aircraft based on dual-mode flow control according to claim 1, characterized in that: A plurality of sets of the dual-mode flow control structures are respectively arranged on straight sections such as the fuselage of the original transport aircraft model to generate a plurality of sets of transport aircraft flow control models, including: Along the flow direction of the conveyor, the vortex generator in the bimodal flow control structure is arranged upstream of the incoming flow, and the groove in the bimodal flow control structure is installed downstream of the incoming flow, with the leading edge of the groove adjacent to the trailing edge of the vortex generator; The vortex generators and the grooves are arranged in parallel along the span direction of the conveyor.

4. The method for reducing drag of a transport aircraft based on dual-mode flow control according to claim 1, characterized in that: Calculating the drag reduction rate of each group of the transport aircraft flow control model separately includes: According to the requirements of numerical simulation efficiency and accuracy, a drag reduction prediction method is selected, among which the drag reduction prediction methods include RANS modeling numerical simulation method and WMLES direct numerical simulation method; Calculating the total resistance of the transport aircraft flow control model using the drag reduction prediction method; Calculating the total resistance of the original model of the transport aircraft using the drag reduction prediction method; The drag reduction rate of the conveyor flow control model is obtained by calculating the total resistance of the conveyor flow control model and the total resistance of the conveyor original model.

5. The method for reducing drag of a transport aircraft based on dual-mode flow control according to claim 4, characterized in that: Calculating the total resistance of the transport aircraft flow control model using the drag reduction prediction method includes: If the drag reduction prediction method is a RANS modeling numerical simulation method, the total drag of the conveyor flow control model is calculated by using the geometric characteristic parameters of the original conveyor model and the dual-mode flow control structure; If the drag reduction prediction method is the WMLES direct numerical simulation method, the total resistance of the conveyor flow control model is obtained by calculating the conveyor flow control model.

6. The method for reducing drag of a transport aircraft based on dual-mode flow control according to claim 5, characterized in that: The total resistance of the conveyor flow control model is calculated by using the geometric characteristic parameters of the conveyor original model and the dual-mode flow control structure, including: Meshing the original model of the transport aircraft to generate first mesh data; defining a flow control file by using the geometric characteristic parameters; Setting a first calculation parameter file, wherein the first calculation parameter file includes a Mach number / Reynolds number, a reference area / chord length, and a calculation method; Generate drag aerodynamic data using the RANS modeling numerical simulation method through the flow control file, the first calculation parameter file and the first grid data; The total resistance in the drag aerodynamic data is used as the total resistance of the transport aircraft flow control model.

7. The method for reducing drag of a transport aircraft based on dual-mode flow control according to claim 5, characterized in that: The total resistance of the conveyor flow control model is calculated by the conveyor flow control model, including: Meshing the conveyor flow control model to generate second mesh data; Setting a second calculation parameter file, wherein the second calculation parameter file includes free flow initial variables, calculation reference parameters, and calculation method definition; The total resistance of the conveyor flow control model is calculated using the second grid data and the second calculation parameter file and the RANS modeling numerical simulation method.

8. The method for reducing drag of a transport aircraft based on dual-mode flow control according to claim 4, characterized in that: The drag reduction rate of the conveyor flow control model is calculated by using the total drag of the conveyor flow control model and the total drag of the conveyor original model, including: Where, ΔC D is the drag reduction rate of the transport aircraft flow control model, C D_original is the total resistance of the original transport model, C D_control is the total resistance of the conveyor flow control model.

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