Mixed laminar flow control vertical fin optimization design method integrating multiple working conditions and multiple constraints

Abstract

The invention provides a mixed laminar flow control vertical fin optimization design method integrating multiple working conditions and multiple constraints, and the method comprises the following steps: setting an optimization target and constraint conditions according to multiple actual working conditions of a vertical fin, and building a vertical fin optimization mathematical model; constructing a design variable; the design variables comprise vertical fin geometric parameter design variables and vertical fin suction coefficient design variables; based on the vertical fin reference configuration, determining an optimization design space of each design variable; and carrying out optimization design. The method has good multi-working-condition and multi-constraint processing capacity, balance of frictional resistance and differential pressure resistance can be comprehensively considered in optimization design, meanwhile, it is guaranteed that the stall characteristic of the vertical fin is not deteriorated in the take-off and landing stage, the airfoil laminar flow range is not suddenly changed in the small sideslip state, various complex engineering constraints can be considered, and the method is suitable for large-scale popularization and application. Therefore, the drag reduction effect of the mixed laminar flow control vertical fin is effectively improved, and the design result better meets the actual engineering requirement.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft optimization design, and particularly relates to an optimization design method for a vertical tail with hybrid laminar flow control considering multiple working conditions and multiple constraints. Background Art

[0002] The frictional drag of a high-subsonic civil aircraft accounts for about 55% of the total aircraft drag. At the same Reynolds number, the frictional drag of a laminar boundary layer is much smaller than that of a turbulent boundary layer. Therefore, laminar design of the vertical tail component of an aircraft can effectively reduce the frictional drag of the aircraft, thereby achieving the purpose of improving the flight efficiency of the aircraft. At present, the technical means to achieve laminar flow on the vertical tail component of an aircraft mainly include: Natural Laminar Flow (NLF), Laminar Flow Control (LFC), and Hybrid Laminar Flow Control (HLFC). Among these technical means, the hybrid laminar flow control technology can form a large-scale laminar flow on the vertical tail surface at a relatively low energy consumption cost and obtain a significant drag reduction effect.

[0003] The hybrid laminar flow control technology suppresses the growth of CF waves by sucking air at the leading edge, and designs a reasonable favorable pressure gradient downstream to suppress TS waves, so as to maintain a large-scale laminar flow at a large leading edge sweep angle and obtain a significant drag reduction effect. Among them, CF wave is an inviscid instability wave generated by the inflection point of the velocity profile in the boundary layer. It is excited in the favorable pressure region and suppressed in the adverse pressure region; TS wave is a viscous instability wave, which is suppressed in the favorable pressure region and excited in the adverse pressure region. For the vertical tail of a high-subsonic civil aircraft, such as the vertical tail of an A320 aircraft, due to the large sweep angle, natural laminar design cannot well suppress the crossflow instability caused by the sweep; the laminar flow control technology with large-scale air suction has high energy consumption of the air suction system and large structural weight; hybrid laminar flow control can obtain a significant drag reduction effect with less energy consumption and will not cause an obvious increase in structural weight, so it has been widely studied and applied.

[0004] In the aviation field, there are few studies on the optimization design method for a vertical tail with hybrid laminar flow control. Although a small number of publicly disclosed optimization design technologies for a vertical tail with hybrid laminar flow control can reduce the air suction energy consumption and improve the drag reduction effect, they do not specifically consider the multi-working condition characteristics of the vertical tail in actual engineering problems. For example, the low-speed stall characteristics of the vertical tail and the drag reduction effect under the sideslip state are not considered in the design process, resulting in the deterioration of the performance of the designed vertical tail during takeoff and landing and under small sideslip conditions. Therefore, it is difficult to obtain a design result that is practical in engineering. Summary of the Invention

[0005] In view of the deficiencies existing in the prior art, the present invention provides an optimized design method for a vertical tail with hybrid laminar flow control that integrates multiple working conditions and multiple constraints, which can effectively solve the above problems.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides an optimized design method for a vertical tail with hybrid laminar flow control that integrates multiple working conditions and multiple constraints, including the following steps:

[0008] Step S1, select the baseline configuration of the vertical tail; set the optimization objectives and constraint conditions according to multiple actual working conditions of the vertical tail, and establish an optimization mathematical model for the vertical tail;

[0009] Step S2, construct design variables; the design variables include design variables of the geometric parameters of the vertical tail and design variables of the suction coefficient of the vertical tail; based on the baseline configuration of the vertical tail, determine the optimization design space of each design variable;

[0010] Step S3, use the baseline configuration of the vertical tail as the initial baseline configuration for the optimization design, sample in the optimization design space of the design variables of the geometric parameters of the vertical tail and the optimization design space of the design variables of the suction coefficient of the vertical tail to obtain a set of sample points;

[0011] Step S4, generate an optimized configuration of the vertical tail based on the set of sample points;

[0012] Step S5, evaluate the aerodynamic performance of the optimized configuration of the vertical tail obtained in Step S4 through computational fluid dynamics numerical simulation methods;

[0013] Step S6, determine whether the aerodynamic performance of the optimized configuration of the vertical tail evaluated in Step S5 meets the optimization mathematical model of the vertical tail in Step S1. If it meets, the iteration terminates and Step S8 is executed; if it does not meet, Step S7 is executed;

[0014] Step S7, determine new added sample points in the optimization design space of the design variables of the geometric parameters of the vertical tail and the optimization design space of the design variables of the suction coefficient of the vertical tail through the point addition criterion algorithm, and integrate the new added sample points and the original set of sample points into a new set of sample points; update the set of sample points in Step S4 and return to Step S4;

[0015] Step S8, output the finally generated optimized configuration of the vertical tail, which is the finally optimized configuration of the vertical tail.

[0016] Preferably, the objective function and constraint conditions of the optimization mathematical model of the vertical tail are as follows:

[0017] min.β 1 ×Q V / Q V0 +β 2×C D / C D0 +β 3 ×(S 0 / S Laminar )

[0018] s.t.

[0019] S Z / B＝0.25_0 ≤0.6

[0020] S Z / B＝0.50_0 ≤0.6

[0021] S Laminar_2_U ≥0.45

[0022] S Laminar_2_L ≥0.45

[0023] Le i ≥Le i0

[0024] Te i ≥Te i0

[0025] Thk i ≥Thk i0

[0026] where: β 1 、β 2 and β 3 are the first coefficient, the second coefficient, and the third coefficient respectively; β 1 +β 2 +β 3 = 1;

[0027] Q V represents the suction gas volume flow rate of the optimized vertical tail; C D represents the drag coefficient of the optimized vertical tail at a 0° sideslip angle; Q V0 represents the suction gas volume flow rate of the baseline configuration of the vertical tail; C D0 represents the drag coefficient of the baseline configuration of the vertical tail at a 0° sideslip angle; S Laminar represents the laminar flow range of the optimized vertical tail at a 0° sideslip angle; S 0 represents the laminar flow range of the baseline configuration of the vertical tail at a 0° sideslip angle;

[0028] S Z / B＝0.25_0 ,S Z / B＝0.50_0 represent the transition positions of the optimized vertical tail at the 25% and 50% spanwise positions at a 0° sideslip angle respectively;

[0029] S Laminar_2_U ,S Laminar_2_Lrespectively represent the laminar flow ranges on the leeward side and the windward side of the optimized vertical tail at a 2° sideslip angle;

[0030] i = 1, 2, 3, respectively represent the spanwise stations of 25%, 50% and 75% of the vertical tail; Le i represents the thickness at the 25%c position of the optimized vertical tail at the i-th spanwise station; Te i represents the thickness at the 75%c position of the optimized vertical tail at the i-th spanwise station; Thk i represents the maximum thickness of the optimized vertical tail;

[0031] Le i0 represents the thickness at the 25%c position of the baseline configuration of the vertical tail at the i-th spanwise station; Te i0 represents the thickness at the 75%c position of the baseline configuration of the vertical tail at the i-th spanwise station; Thk i0 represents the maximum thickness of the baseline configuration of the vertical tail.

[0032] Preferably, β 1 、β 2 and β 3 are 0.2, 0.4 and 0.4 respectively.

[0033] Preferably, the vertical tail suction coefficient is defined as C q = -(ρ S V S ) / (ρ ∞ V ∞ ), where ρ s 、V s respectively represent the air flow density at the wall surface and the suction velocity perpendicular to the wall surface; ρ ∞ 、V ∞ respectively represent the air flow density in the far field and the free stream velocity;

[0034] The suction volume flow rate is S Suction ×ρ S ×V S ; where S Suction represents the area of the suction region.

[0035] The hybrid laminar flow control vertical tail optimization design method provided by the present invention that comprehensively considers multiple working conditions and multiple constraints has the following advantages:

[0036] In view of the multi - operating - condition characteristics faced by the vertical tail in actual engineering problems, based on the design concept of simultaneously considering the suction parameters and aerodynamic shape, the present invention comprehensively considers the balance between frictional drag and pressure drag in the optimization design, ensuring that the stall characteristics of the vertical tail do not deteriorate during take - off and landing, and the laminar - flow range on the vertical - tail surface does not change suddenly in the small - sideslip state. At the same time, various complex engineering constraints can be considered, such as no reduction in the vertical - tail thickness, no decrease in the low - speed lift - curve slope and stall angle of attack, etc., thereby further improving the drag - reduction effect of the hybrid laminar - flow - controlled vertical tail. Finally, a hybrid laminar - flow - controlled vertical tail that better meets the actual engineering requirements is obtained. Brief Description of the Drawings

[0037] Figure 1 is a flowchart of an optimization design method for a hybrid laminar - flow - controlled vertical tail that comprehensively considers multiple operating conditions and multiple constraints provided by the present invention;

[0038] Figure 2 is a schematic diagram of the planar geometry, airfoil configuration, and suction region of the baseline configuration of an embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of the optimization design space of the vertical - tail root airfoil of an embodiment of the present invention;

[0040] Figure 4 is a schematic diagram of the optimization design space of the vertical - tail airfoil at the Z / B = 50% spanwise station of an embodiment of the present invention;

[0041] Figure 5 is a schematic diagram of the optimization design space of the vertical - tail tip airfoil of an embodiment of the present invention;

[0042] Figure 6 is a schematic diagram of the optimization design space of the suction coefficient of different suction regions of the vertical tail of an embodiment of the present invention;

[0043] Figure 7 is a convergence - history diagram of the optimization design of the hybrid laminar - flow - controlled vertical tail of an embodiment of the present invention;

[0044] Figure 8 is a comparison diagram of the root airfoils of the BASE configuration and the OPT configuration of an embodiment of the present invention;

[0045] Figure 9 is a comparison diagram of the airfoils at the Z / B = 50% spanwise station of the BASE configuration and the OPT configuration of an embodiment of the present invention;

[0046] Figure 10 is a comparison diagram of the tip airfoils of the BASE configuration and the OPT configuration of an embodiment of the present invention;

[0047] Figure 11 is a comparison diagram of the suction - coefficient distributions of different suction regions of the BASE configuration and the OPT configuration of an embodiment of the present invention;

[0048] Figure 12 It is the pressure distribution diagram of the BASE configuration of the embodiment of the present invention with Z / B = 25% at a sideslip angle of 0° to 2°;

[0049] Figure 13 It is the pressure distribution diagram of the BASE configuration of the embodiment of the present invention with Z / B = 50% at a sideslip angle of 0° to 2°;

[0050] Figure 14 It is the pressure distribution diagram of the BASE configuration of the embodiment of the present invention with Z / B = 75% at a sideslip angle of 0° to 2°;

[0051] Figure 15 It is the pressure distribution diagram of the OPT configuration of the embodiment of the present invention with Z / B = 25% at a sideslip angle of 0° to 2°;

[0052] Figure 16 It is the pressure distribution diagram of the OPT configuration of the embodiment of the present invention with Z / B = 50% at a sideslip angle of 0° to 2°;

[0053] Figure 17 It is the pressure distribution diagram of the OPT configuration of the embodiment of the present invention with Z / B = 75% at a sideslip angle of 0° to 2°;

[0054] Figure 18 It is the comparison diagram of the lift lines of the BASE and OPT configurations of the embodiment of the present invention.

[0055] Wherein:

[0056] 1 represents the wing root airfoil of the BASE configuration;

[0057] 2 represents the lower bound of the optimization design space of the vertical tail wing root airfoil;

[0058] 3 represents the upper bound of the optimization design space of the vertical tail wing root airfoil;

[0059] 4 represents the airfoil of the BASE configuration at the Z / B = 50% spanwise station;

[0060] 5 represents the lower bound of the optimization design space of the vertical tail airfoil at the Z / B = 50% spanwise station;

[0061] 6 represents the upper bound of the optimization design space of the vertical tail airfoil at the Z / B = 50% spanwise station;

[0062] 7 represents the wing tip airfoil of the BASE configuration;

[0063] 8 represents the lower bound of the optimization design space of the vertical tail wing tip airfoil;

[0064] 9 represents the upper bound of the optimization design space of the vertical tail wing tip airfoil;

[0065] 10 represents the suction coefficient distribution of different suction regions in the BASE configuration;

[0066] 11 represents the lower bound of the optimization design space of the suction coefficient for different suction regions;

[0067] 12 represents the upper bound of the optimization design space of the suction coefficient for different suction regions;

[0068] 13 represents the airfoil at the wing root in the OPT configuration;

[0069] 14 represents the airfoil at the spanwise station of Z / B = 50% in the OPT configuration;

[0070] 15 represents the airfoil at the wing tip in the OPT configuration;

[0071] 16 represents the suction coefficient distribution of different suction regions in the OPT configuration;

[0072] 17 represents the pressure distribution at the Z / B = 25% station of the BASE configuration under a sideslip angle of 0°;

[0073] 18 represents the pressure distribution at the Z / B = 25% station of the BASE configuration under a sideslip angle of 1°;

[0074] 19 represents the pressure distribution at the Z / B = 25% station of the BASE configuration under a sideslip angle of 2°;

[0075] 20 represents the pressure distribution at the Z / B = 50% station of the BASE configuration under a sideslip angle of 0°;

[0076] 21 represents the pressure distribution at the Z / B = 50% station of the BASE configuration under a sideslip angle of 1°;

[0077] 22 represents the pressure distribution at the Z / B = 50% station of the BASE configuration under a sideslip angle of 2°;

[0078] 23 represents the pressure distribution at the Z / B = 75% station of the BASE configuration under a sideslip angle of 0°;

[0079] 24 represents the pressure distribution at the Z / B = 75% station of the BASE configuration under a sideslip angle of 1°;

[0080] 25 represents the pressure distribution at the Z / B = 75% station of the BASE configuration under a sideslip angle of 2°;

[0081] 26 represents the pressure distribution at the Z / B = 25% station of the OPT configuration under a sideslip angle of 0°;

[0082] 27 represents the pressure distribution at the Z / B = 25% station of the OPT configuration under a sideslip angle of 1°;

[0083] 28 represents the pressure distribution at the Z / B = 25% station of the OPT configuration under a sideslip angle of 2°;

[0084] 29 represents the pressure distribution of the OPT configuration with Z / B = 50% at a sideslip angle of 0°;

[0085] 30 represents the pressure distribution of the OPT configuration with Z / B = 50% at a sideslip angle of 1°;

[0086] 31 represents the pressure distribution of the OPT configuration with Z / B = 50% at a sideslip angle of 2°;

[0087] 32 represents the pressure distribution of the OPT configuration with Z / B = 75% at a sideslip angle of 0°;

[0088] 33 represents the pressure distribution of the OPT configuration with Z / B = 75% at a sideslip angle of 1°;

[0089] 34 represents the pressure distribution of the OPT configuration with Z / B = 75% at a sideslip angle of 2°;

[0090] 35 represents the lift curve of the BASE configuration;

[0091] 36 represents the lift curve of the OPT configuration. Detailed implementation mode

[0092] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the following further details the present invention in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0093] The present invention mainly focuses on the optimized design of the vertical tail components of civil aircraft applying the hybrid laminar flow control technology. On the basis of considering the design concept of suction parameters and aerodynamic shape, a more suitable optimized design method for the hybrid laminar flow control vertical tail of civil aircraft actual engineering needs is developed. This method is based on an efficient global surrogate optimization algorithm and has good multi-condition and multi-constraint processing capabilities. The prominent feature of the present invention is that it can comprehensively consider the balance between frictional drag and pressure drag in the optimized design, while ensuring that the stall characteristics of the vertical tail do not deteriorate during the takeoff and landing stages, the laminar flow range on the vertical tail surface does not change suddenly in the small sideslip state, and can consider various complex engineering constraints, thereby effectively improving the drag reduction effect of the hybrid laminar flow control vertical tail and making the design results more in line with the actual engineering needs.

[0094] Compared with the existing hybrid laminar flow control optimized design methods, the optimized design method of the present invention comprehensively considers various actual conditions of civil aircraft vertical tails under complex engineering constraints, such as the balance between frictional drag and pressure drag, the stall characteristics of the vertical tail during the takeoff and landing stages, and the laminar flow range on the vertical tail surface in the small sideslip state, can effectively improve the drag reduction effect of the hybrid laminar flow control vertical tail, and at the same time ensure that the design results are more in line with the actual engineering needs.

[0095] Refer to Figure 1 , the present invention provides a hybrid laminar flow control vertical tail optimization design method integrating multiple working conditions and multiple constraints, including the following steps:

[0096] Step S1, select the vertical tail reference configuration; set the optimization objectives and constraint conditions according to multiple actual working conditions of the vertical tail, and establish a vertical tail optimization mathematical model;

[0097] As a specific form, the objective function and constraint conditions of the vertical tail optimization mathematical model are as follows:

[0098] min.β 1 ×Q V / Q V0 +β 2 ×C D / C D0 +β 3 ×(S 0 / S Laminar )

[0099] s.t.

[0100] S Z / B＝0.25_0 ≤0.6

[0101] S Z / B＝0.50_0 ≤0.6

[0102] S Laminar_2_U ≥0.45

[0103] S Laminar_2_L ≥0.45

[0104] Le i ≥Le i0

[0105] Te i ≥Te i0

[0106] Thk i ≥Thk i0

[0107] Where: β 1 , β 2 and β 3 are the first coefficient, the second coefficient and the third coefficient respectively; β 1 +β 2 +β 3 =1; The preferred method is: β 1 , β 2 and β 3 are 0.2, 0.4 and 0.4 respectively.

[0108] Q Vrepresents the suction gas volume flow rate of the optimized vertical tail; C D represents the drag coefficient of the optimized vertical tail at a sideslip angle of 0°; Q V0 represents the suction gas volume flow rate of the baseline configuration of the vertical tail; C D0 represents the drag coefficient of the baseline configuration of the vertical tail at a sideslip angle of 0°; S Laminar represents the laminar range of the optimized vertical tail at a sideslip angle of 0°; S 0 represents the laminar range of the baseline configuration of the vertical tail at a sideslip angle of 0°;

[0109] S Z / B＝0.25_0 ,S Z / B＝0.50_0 respectively represent the transition positions of the optimized vertical tail at 25% and 50% spanwise positions at a sideslip angle of 0°;

[0110] S Laminar_2_U ,S Laminar_2_L respectively represent the laminar ranges of the leeward side and the windward side of the optimized vertical tail at a sideslip angle of 2°;

[0111] i = 1, 2, 3, respectively represent the vertical tail at 25%, 50% and 75% spanwise positions; Le i represents the thickness of the optimized vertical tail at the 25%c position of the i-th spanwise position; Te i represents the thickness of the optimized vertical tail at the 75%c position of the i-th spanwise position; Thk i represents the maximum thickness of the optimized vertical tail;

[0112] Le i0 represents the thickness of the baseline configuration of the vertical tail at the 25%c position of the i-th spanwise position; Te i0 represents the thickness of the baseline configuration of the vertical tail at the 75%c position of the i-th spanwise position; Thk i0 represents the maximum thickness of the baseline configuration of the vertical tail.

[0113] Step S2, construct design variables; the design variables include vertical tail geometric parameter design variables and vertical tail suction coefficient design variables; based on the baseline configuration of the vertical tail, determine the optimization design space of each design variable;

[0114] Step S3, use the baseline configuration of the vertical tail as the initial baseline configuration for optimization design, sample in the optimization design space of the vertical tail geometric parameter design variables and the optimization design space of the vertical tail suction coefficient design variables to obtain a set of sample points;

[0115] Step S4, generate an optimized configuration of the vertical tail based on the set of sample points;

[0116] Step S5: Evaluate the aerodynamic performance of the optimized vertical tail configuration obtained in step S4 through computational fluid dynamics numerical simulation method;

[0117] Step S6: Determine whether the aerodynamic performance of the optimized vertical tail configuration evaluated in step S5 meets the vertical tail optimization mathematical model in step S1. If it meets, terminate the iteration and execute step S8; if it does not meet, execute step S7;

[0118] Step S7: Determine new sample points in the optimization design space of the vertical tail geometric parameter design variables and the optimization design space of the vertical tail suction coefficient design variables through the point addition criterion algorithm, and integrate the new sample points and the original sample point set into a new sample point set; update the sample point set in step S4 and return to step S4;

[0119] Step S8: Output the finally generated optimized vertical tail configuration, which is the finally optimized vertical tail configuration.

[0120] The hybrid laminar flow control vertical tail optimization design method of the present invention adopts an efficient global surrogate optimization algorithm, which can consider the multi-condition and multi-constraint characteristics of civil aircraft vertical tail design. During the optimization design process, it can comprehensively consider the balance between frictional drag and pressure drag, and at the same time ensure that the stall characteristics of the vertical tail during the takeoff and landing stages of civil aircraft do not deteriorate, and the laminar flow range on the vertical tail surface does not change suddenly under small sideslip conditions. And it can consider various complex engineering constraints. Thereby improving the drag reduction effect and engineering practicability of the hybrid laminar flow control vertical tail.

[0121] The following introduces an embodiment:

[0122] The inventor used the developed optimization design method to carry out multiple rounds of optimization design on a vertical tail baseline configuration (BASE) and obtained an optimized configuration OPT. The planar geometry and suction area configuration of the vertical tail baseline configuration are as Figure 2 shown, in which three-stage suction is adopted. The area from the leading edge of the vertical tail to 20% chord length is divided into three sections, namely 0% - 6%, 6% - 12%, and 12% - 20%. In Figure 2 C1, C2, and C3 are used, representing the first, second, and third suction areas respectively; different suction coefficient designs are used. The suction coefficient is defined as C q = -(ρ S V S ) / (ρ ∞ V ∞ ), where ρ s , V s represent the air flow density at the wall surface and the suction velocity perpendicular to the wall surface respectively, and ρ ∞ , V ∞They represent the air flow density and the free stream velocity at the far field respectively. To more intuitively reflect the difference in the air intake, the air intake is defined as: Q = S Suction × ρ S × V S , where S Suction represents the area of the air intake region. The main design conditions and constraints considered in the design process include the cruise state at 0° and 2° sideslip angles, the vertical tail thickness, the low-speed stall characteristics, and the drag reduction effect, etc. Specifically:

[0123] The mathematical model of the optimization problem is specifically:

[0124] min. 0.2 × Q V / Q V0 + 0.4 × C D / C D0 + 0.4 × (S 0 / S Laminar )

[0125] s.t.

[0126] S Z / B＝0.25_0 ≤ 0.6

[0127] S Z / B＝0.50_0 ≤ 0.6

[0128] S Laminar_2_U ≥ 0.45

[0129] S Laminar_2_L ≥ 0.45

[0130] Le i ≥ Le i0

[0131] Te i ≥ Te i0

[0132] Thk i ≥ Thk i0

[0133] In the formula:

[0134] Q V represents the air intake volume flow rate of the optimized vertical tail; C D represents the drag coefficient of the optimized vertical tail at 0° sideslip angle; Q V0 represents the air intake volume flow rate of the baseline configuration of the vertical tail; C D0 represents the drag coefficient of the baseline configuration of the vertical tail at 0° sideslip angle; S Laminar represents the laminar flow range of the optimized vertical tail at 0° sideslip angle; S 0 represents the laminar flow range of the baseline configuration of the vertical tail at 0° sideslip angle;

[0135] S Z / B＝0.25_0 and S Z / B＝0.50_0 respectively represent the transition positions of the optimized vertical tail at the 25% and 50% spanwise stations at a 0° sideslip angle; this constraint condition constrains the transition position, which is an innovative constraint condition of the present invention. Specifically, the inventor has found through research that by constraining the transition position to prevent it from being too far back, not only can the pressure drag and friction drag be balanced, but also the position of the maximum thickness is indirectly constrained from being too far back, ensuring the stall characteristics of the vertical tail in the low-speed state and realizing that the stall characteristics of the vertical tail do not deteriorate during the takeoff and landing phases;

[0136] S Laminar_2_U and S Laminar_2_L respectively represent the laminar flow ranges on the leeward side and windward side of the optimized vertical tail at a 2° sideslip angle;

[0137] i = 1, 2, 3, respectively representing the vertical tail at the 25%, 50%, and 75% spanwise stations; Le i represents the thickness of the optimized vertical tail at the 25% c position at the i-th spanwise station; Te i represents the thickness of the optimized vertical tail at the 75% c position at the i-th spanwise station; Thk i represents the maximum thickness of the optimized vertical tail;

[0138] Le i0 represents the thickness of the vertical tail reference configuration at the 25% c position at the i-th spanwise station; Te i0 represents the thickness of the vertical tail reference configuration at the 75% c position at the i-th spanwise station; Thk i0 represents the maximum thickness of the vertical tail reference configuration.

[0139] Therefore, the mathematical model of the optimization problem provided by the present invention has the following characteristics:

[0140] (1) The maximum thickness, the thickness at the 25% c position, and the thickness at the 75% c position of the airfoil of each section of the vertical tail along the spanwise direction are not less than those of the reference configuration, and the planform shape of the vertical tail does not change compared with the reference configuration; where c represents the chord length;

[0141] (2) Considering the transition position and laminar flow range at 0° and 2° sideslip angles under the sideslip state comprehensively to ensure the aerodynamic characteristics under each sideslip state and the robustness of the scheme;

[0142] Specifically, by restricting the constraint of the transition position at a 0° sideslip angle, the lateral aerodynamic performance of the vertical tail in the low-speed state is ensured, and the stall angle of attack and lift curve slope are basically not reduced compared with the reference configuration;

[0143] By constraining the laminar flow range on the leeward side and the laminar flow range on the windward side at a 2° sideslip angle, the laminar flow range is made more than 45%, minimizing the component drag to the greatest extent.

[0144] Take the airfoil of the three sections at the wing root, the 50% spanwise station of Z / B, and the wing tip of the vertical tail and the suction coefficients of different suction regions as design variables. Keep the taper ratio, aspect ratio, leading edge sweep angle, and wing area of the vertical tail unchanged. Take the BASE configuration as the initial reference configuration for the optimization design. Figures 3 to 6 The optimized design space (the variation range of design variables) is shown. Figure 7 The convergence history of the optimized design is given. Figures 8 to 11 The airfoil and suction coefficient distributions at typical stations of the BASE configuration and the OPT configuration are shown.

[0145] Using the computational fluid dynamics (CFD) numerical simulation method, the aerodynamic performance of the vertical tail reference configuration (BASE) and the OPT configuration (the vertical tail configuration optimized by the present invention) designed by the method of the present invention is evaluated and compared. The evaluation calculation conditions are: (1) Mach number is 0.78, Reynolds number is 2.5×10 7 , sideslip angle is 0° to 2°; (2) Mach number is 0.3, Reynolds number is 2.0×10 7 , sideslip angle is 0° to 19°. The S-A model is used for turbulence simulation, and the e N method is used for transition prediction. The two critical disturbance amplification factors [N tr_TS , N tr_CF for transition prediction are taken as [6.5, 7.5] respectively. The comparison results are as Figures 12 to 17 shown. As Figures 12 to 17 can be seen, the OPT configuration of the vertical tail enhances the favorable pressure gradient and its range on the vertical tail surface in the cruise state, weakens the adverse pressure gradient near the leading edge of the vertical tail in the sideslip state, and shortens the length of the leading edge acceleration region, successfully suppressing the growth of the CF / TS waves on the windward side / leeward side of the vertical tail in the sideslip state, significantly increasing the laminar flow range of the vertical tail in the cruise and sideslip states, and thus reducing the skin friction drag of the vertical tail.

[0146] In the cruise and sideslip states, the laminar flow range and drag coefficient on the upper and lower surfaces of the vertical tail are shown in Table 1 as follows:

[0147] Table 1 Comparison of Aerodynamic Characteristics of BASE Configuration and OPT Configuration at Design Point (Ma = 0.78, Re = 2.5×10 7 , β = 0° to 2°)

[0148]

[0149] As can be seen from Table 1, compared with the non-suction BASE configuration, the laminar flow range of the vertical tail OPT configuration reaches 57.70% in the cruise state. The total drag coefficient decreases from 50.15 cts to 31.74 cts, and the drag reduction of the vertical tail component is 36.71%. Moreover, near the design state at a sideslip angle of 0° to 2°, the laminar flow ranges on both the windward and leeward sides of the vertical tail OPT configuration are maintained above 45%, and the thickness and maximum thickness at the 25% c and 75% c positions of the OPT configuration do not decrease.

[0150] Finally, the side force coefficients of the vertical tail BASE and OPT configurations at different sideslip angles in the low-speed state are evaluated, and the results are as Figure 18 shown: The slope of the linear segment of the side force coefficient of the vertical tail BASE in the low-speed state is dC N_BASE / dβ = 0.05565 / deg; the slope of the linear segment of the side force coefficient of the OPT configuration in the low-speed state is dC N_OPT / dβ = 0.05505 / deg; the stall angle β Stall_BASE of the vertical tail BASE in the low-speed state is 14°; the stall angle β Stall_OPT of the OPT configuration in the low-speed state is 15°.

[0151] It can be seen that the lift line slope of the OPT configuration is basically the same as that of the reference configuration, and the stall angle is not lower than that of the reference configuration. While achieving the drag reduction design goal, other aerodynamic performances of the vertical tail are not reduced.

[0152] The comprehensive design and calculation results show that: the hybrid laminar flow control vertical tail optimization design method of the present invention can comprehensively consider various actual working conditions and various engineering constraints, and can design a design scheme with good drag reduction effect and more in line with engineering needs.

[0153] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A hybrid laminar flow control vertical tail optimization design method with comprehensive multi-condition and multi-constraints, characterized in that: The following steps are involved: Step S1, selecting a vertical tail reference configuration; According to the actual working conditions of the vertical tail, the optimization objectives and constraints are set, and the vertical tail optimization mathematical model is established; Step S2, constructing design variables; The design variables include vertical tail geometric parameter design variables and vertical tail suction coefficient design variables; Based on the vertical tail reference configuration, determining an optimal design space for each of the design variables; Step S3, taking the vertical tail reference configuration as the initial reference configuration for optimization design, sampling in the optimization design space of the vertical tail geometric parameter design variables and the optimization design space of the vertical tail suction coefficient design variables to obtain a sample point set; Step S4, generating an optimized configuration of the vertical tail based on the sample point set; Step S5, evaluating the aerodynamic performance of the vertical tail optimized configuration obtained in step S4 by using a computational fluid dynamics numerical simulation method; Step S6, determining whether the aerodynamic performance of the vertical tail optimized configuration evaluated in step S5 satisfies the vertical tail optimization mathematical model in step S1, if so, the iteration is terminated and step S8 is executed; If not satisfied, execute step S7; Step S7, determining new sample points in the optimization design space of the vertical tail geometric parameter design variables and the optimization design space of the vertical tail suction coefficient design variables by using a point adding criterion algorithm, and integrating the new sample points and the original sample point set into a new sample point set; Update the sample point set of step S4, and return to step S4; Step S8, outputting the finally generated vertical tail optimized configuration, which is the vertical tail optimized configuration finally obtained by optimization.

2. The method for optimizing the design of a hybrid laminar flow control vertical tail with comprehensive multi-condition and multi-constraints according to claim 1 is characterized in that: The objective function and constraints of the vertical tail optimization mathematical model are as follows: min.β1×Q V / Q V0 +β2×C D / C D0 +β3×(S0 / S Laminar ) st S Z / B＝0.25_0 ≤0.6 S Z / B＝0.50_0 ≤0.6 S Laminar_2_U ≥0.45 S Laminar_2_L ≥0.45 The i ≥The i0 The i ≥The i0 Thk i ≥Thk i0 Among them: β1, β2 and β3 are the first coefficient, the second coefficient and the third coefficient respectively; β1+β2+β3=1; Q V represents the optimized vertical tail suction volume flow rate; C D represents the drag coefficient of the optimized vertical tail at a sideslip angle of 0°; Q V0 represents the intake volume flow rate of the vertical tail reference configuration; C D0 represents the drag coefficient of the vertical tail reference configuration at a sideslip angle of 0°; S Laminar represents the laminar flow range of the optimized vertical tail at a sideslip angle of 0°; S0 represents the laminar flow range of the vertical tail reference configuration at a sideslip angle of 0°; S Z / B＝0.25_0 , S Z / B =0.50_0 respectively represent the transition positions of the optimized vertical tail at 25% and 50% positions in the span direction at a sideslip angle of 0°; S Laminar_2_U , S Laminar_2_L They represent the laminar flow range of the leeward side and the laminar flow range of the windward side of the optimized vertical tail at a sideslip angle of 2° respectively; i=1, 2, 3, respectively, represents the vertical tail at 25%, 50% and 75% spanwise positions; Lei represents the optimized thickness of the vertical tail at the 25%c position of the i-th spanwise position; Tei represents the optimized thickness of the vertical tail at the 75%c position of the i-th spanwise position; Thki represents the maximum thickness of the optimized vertical tail; Le i0 Te represents the thickness of the vertical tail reference configuration at the 25% c position of the i-th spanwise position; i0 Thk represents the thickness of the vertical tail reference configuration at the 75% c position of the i-th spanwise position; i0 Indicates the maximum thickness of the vertical tail reference configuration.

3. The method for optimizing the design of a hybrid laminar flow control vertical tail with comprehensive multi-condition and multi-constraints according to claim 2 is characterized in that: β1, β2 and β3 are 0.2, 0.4 and 0.4 respectively.

4. The method for optimizing the design of a hybrid laminar flow control vertical tail with comprehensive multi-condition and multi-constraints according to claim 2 is characterized in that: The vertical tail suction coefficient is defined as C q =-(ρ S V S ) / (ρ ∞ V ∞ ), where ρ s 、V s Respectively represent the air flow density at the wall and the suction speed vertical to the wall; ρ ∞ 、V ∞ Represent the airflow density and free stream velocity in the far field respectively; The suction volume flow is S Suction ×ρ S ×V S ; Among them, S Suction Represents the area of ​​the suction region.

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