Conveyor drag reduction method based on bimodal flow control

Abstract

The invention provides a transport plane drag reduction method based on bimodal flow control, which comprises the following steps: designing a plurality of groups of bimodal flow control structures according to parameters of a transport plane, and determining geometric characteristic parameters of each group of bimodal flow control structures, each bimodal flow control structure comprising a vortex generator and a groove; a plurality of sets of bimodal flow control structures are arranged on the equal straight section of the conveyor body of the conveyor original model, and a plurality of sets of conveyor flow control models are generated; according to the geometrical characteristic parameters of the bimodal flow control structure, the drag reduction rate of each set of transport plane flow control model is calculated, the set of transport plane flow control model with the maximum drag reduction rate serves as a final deceleration design model, and the final deceleration design model is arranged on the transport plane original model. Through the bimodal flow control structure, the wall surface friction resistance caused by a turbulent boundary layer can be effectively reduced, and a more excellent resistance reduction effect is achieved under the same flow working condition.

Description

Technical Field

[0001] The 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 are in urgent need of developing a new generation of transport aircraft that saves fuel and can reach high, subsonic or even supersonic speeds. The key factor limiting 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 about 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 the total drag is to reduce frictional drag, and most of the frictional drag on the fuselage surface is caused by the turbulent boundary layer. Therefore, without changing the aerodynamic shape of the aircraft and the frictional infiltration area, controlling the flow state in the turbulent boundary layer on the fuselage surface is most likely to bring significant drag reduction benefits, further improve the economy 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, which has a relatively limited drag reduction effect and also limits its adaptability under different working conditions. Traditional active / passive flow control methods for transport aircraft that reduce friction resistance mostly focus on controlling the small-scale flow structure in the near-wall region of the turbulent boundary layer. However, as the Reynolds number increases, the contribution of the small-scale flow structure in the turbulent boundary layer to the turbulent kinetic energy and wall friction resistance gradually decreases, and the influence of the large-scale flow structure in the turbulent boundary layer on the wall friction resistance gradually increases, and the drag reduction effect of traditional active / passive flow control methods for transport aircraft decreases accordingly. Summary of the invention

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

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

[0007] A transport aircraft drag reduction method based on dual-mode flow control, comprising:

[0008] According to the parameters of the conveyor, a plurality of groups of dual-mode flow control structures are designed, and the geometric characteristic parameters of each group of dual-mode flow control structures are determined, wherein the dual-mode flow control structures include vortex generators and grooves;

[0009] A plurality of dual-mode flow control structures are respectively set on straight sections such as the fuselage of the original model of the transport aircraft to generate a plurality 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, and the group of conveyor flow control models with the largest drag reduction rate is taken 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 such as the fuselage of the original model of the transport aircraft 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 and arranged downstream of the incoming flow, and the leading edge of the groove is close 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, drag reduction prediction methods are selected, among which drag reduction prediction methods include 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 a 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 drag of the conveyor flow control model is calculated through the conveyor flow control model.

[0023] Furthermore, the total resistance of the conveyor flow control model is obtained by calculating the geometric characteristic parameters of the conveyor original 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 taken 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 conveyor flow control model is calculated by 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 model of the transport aircraft, C D_control is the total drag of the conveyor flow control model.

[0035] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in the embodiments of this specification include at least:

[0036] The dual-mode flow control structure can effectively reduce the wall friction resistance caused by the turbulent boundary layer, achieving 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 drawings required for use in the embodiments will be briefly introduced below. 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 paying 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 is a schematic diagram of geometric characteristic parameters of a groove according to an embodiment of the present invention;

[0043] Figure 6 is a 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 being arranged on a conveyor;

[0045] Figure 8 It 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 in the embodiments of the present 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] The dual-mode flow control structure can simultaneously control both large-scale and small-scale turbulent energetic structures in the turbulent boundary layer because it couples the grooves and vortex generators together. The grooves can control the small-scale flow structure in the near-wall area and reduce the small-scale friction resistance component generated on the wall; the vortex generator can control the large-scale flow structure in the higher flow layer and reduce the large-scale friction resistance component generated on the wall. At the same time, it can also control its 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 resistance. The dual-mode flow control structure can reduce the wall friction resistance caused by the turbulent boundary layer to a greater extent, and achieve a better 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 as follows: Figure 1 As shown, the following steps are included:

[0050] Step 1: Original 3D model of the transport aircraft ( Figure 2 ) performs mesh division to generate the second mesh 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 grid distance of about 1×10 -6 m (in step 1). The original model of the transport aircraft is calculated by RANS numerical simulation 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 arrangement of the dual-mode flow control structure is that in the streamwise direction, the vortex generator is located upstream of the incoming flow, and the leading edge of the groove is adjacent to the trailing edge of the vortex generator and is located downstream of the incoming flow; in the spanwise direction, the vortex generator and the groove are arranged in parallel. The spanwise width of the dual-mode flow control structure is smaller than the straight section diameter of the original model of the transport aircraft, and the streamwise length of the dual-mode flow control structure is smaller than the straight section length of the original model of the transport aircraft.

[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 are located downstream of the incoming flow. In the span direction, the vortex generators and the grooves are arranged in parallel without spacing, such as Figure 3 and Figure 4 .

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

[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 of height, width, length and spacing, and meet the requirements that the span width of the dual-mode flow control structure is less than 6.2m, the flow length is less than 36m, and the vortex generator structure height is less than 0.02m.

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

[0059] The boundary layer of the original model of the transport aircraft changes at a distance of 5.6 m from the nose. At a distance of 12.0 m 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 model of the transport aircraft. A total of 6 structures are installed, such as Figure 7 shown.

[0060] Step 5. Select the drag reduction prediction method according to the requirements of numerical simulation efficiency and accuracy. The prediction methods include RANS modeling numerical simulation method or WMLES direct numerical simulation method. RANS modeling numerical simulation method focuses more on numerical simulation efficiency and is suitable for engineering evaluation applications. WMLES direct numerical simulation method focuses more on numerical simulation flow field details and is more suitable for drag reduction mechanism research.

[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 calculation grid of the original model of the transport aircraft in step 1; the flow control file defined by the geometric characteristic parameters of the first group 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 The total drag C of the transport flow control model D1_control .

[0062] If the drag reduction mechanism is studied, the numerical simulation of the flow field details is more emphasized, and 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, and 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 of the remaining groups of transport aircraft flow control models. D2 , ΔC D3 ..., compared with the group of dual-mode flow control structures with higher overall drag reduction rate, the group of dual-mode flow control structures with the largest drag reduction rate is taken as the final result, that is, the best dual-mode flow control drag reduction method for transport aircraft under the current calculation conditions is obtained. D_original is the total resistance of the original model of the transport aircraft, C D_control is the total drag of the conveyor flow control model.

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

[0066] The dual-mode flow control structure can simultaneously control the large-scale and small-scale turbulent energetic structures in the turbulent boundary layer because it couples the grooves and vortex generators together. The grooves can control the small-scale flow structure in the near-wall area and reduce the small-scale friction resistance component generated on the wall; the vortex generator can control the large-scale flow structure in the higher flow layer and reduce the large-scale friction resistance component generated on the wall. At the same time, it can also control its 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 resistance. The dual-mode flow control structure can reduce the wall friction resistance caused by the turbulent boundary layer to a greater extent, and achieve a better drag reduction effect under the same flow conditions.

[0067] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of protection of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other, and with each other.

Claims

1. A method for reducing drag of a conveyor based on dual-mode flow control, characterized in that: include: According to the parameters of the conveyor, a plurality of groups of dual-mode flow control structures are designed, and geometric characteristic parameters of each group of the dual-mode flow control structures are determined, wherein the dual-mode flow control structures include vortex generators and grooves; Arranging a plurality of groups of the dual-mode flow control structures on straight sections such as the fuselage of the original model of the transport aircraft respectively to generate a plurality of groups of transport aircraft flow control models; According to the geometric characteristic parameters of the dual-mode 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 conveyor 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 model of the transport aircraft 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 dual-mode flow control structure is arranged upstream of the incoming flow, and the groove in the dual-mode flow control structure is installed downstream of the incoming flow, and the leading edge of the groove is 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 conveyor 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, including: According to the requirements of numerical simulation efficiency and accuracy, drag reduction prediction methods are selected, among which drag reduction prediction methods include RANS modeling numerical simulation method and WMLES direct numerical simulation method; The total drag of the transport aircraft flow control model is calculated using the drag reduction prediction method; The total resistance of the original model of the transport aircraft is calculated using the drag reduction prediction method; 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.

5. The method for reducing drag of a conveyor based on dual-mode flow control according to claim 4, characterized in that: The total drag of the transport aircraft flow control model is calculated using the drag reduction prediction method, including: 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 drag of the conveyor flow control model is calculated by the conveyor flow control model.

6. The method for reducing drag of a conveyor 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 means of 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 by 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 taken as the total resistance of the transport aircraft flow control model.

7. The method for reducing drag of a conveyor 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 by 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 conveyor 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 model of the transport aircraft, C D_control is the total resistance of the conveyor flow control model.

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