An internal embedded missile bay honeycomb configuration aerodynamic layout with improved flow field stability

Abstract

The application provides an internal embedded bomb cabin honeycomb configuration aerodynamic layout for improving flow field stability, and the internal embedded bomb cabin cross section body is a hexagonal honeycomb configuration layout, wherein the top surface of the honeycomb configuration is opened, the other five surfaces are closed wall surfaces, the top surface is parallel to the bottom surface, the included angle alpha between the bottom surface and the adjacent surface is 135 degrees, the longitudinal depth ratio beta of the honeycomb configuration is L / H=1.5, L is the maximum transverse distance of the bomb cabin cross section, and H is the maximum longitudinal height of the bomb cabin cross section. Under the condition of meeting the requirements of structural strength, sound and heat insulation, weight reduction, internal structure design of the fuselage, capacity and other constraints, the internal flow flow field stability of the internal embedded bomb cabin can be greatly improved, the flow field characteristics are improved from the physical root, the evolution of fine vortex and secondary vortex is effectively inhibited, and the process of the flow field from the steady state to the unsteady state is greatly delayed. Because the optimization design effectively inhibits the unsteady flow, especially the premature appearance of the turbulent flow, the aerodynamic efficiency of the internal flow of the bomb cabin is improved.

Description

Technical Field

[0001] This invention relates to the field of aircraft aerodynamic layout optimization design, specifically to an internally embedded bomb bay-like honeycomb aerodynamic layout that improves flow field stability. Background Technology

[0002] The internal flow driven by a cavity top cover is a classic problem in aerodynamics, and the applicant has conducted extensive research on the internal flow field. Based on previous research, we know that the internal flow driven by a square cavity top cover evolves from a steady state to an unsteady periodic flow, then to an unsteady quasi-periodic flow, and finally to turbulence, as the Reynolds number increases. This can be intuitively seen from the flow field diagram (…). Figure 1 We can see that the cavity is dominated by a large, relatively stable primary vortex. Secondary vortices appear at the bottom of the cavity and grow with increasing Reynolds number, while more and smaller secondary vortices also appear. Moffat, in his paper "Viscous and resistive eddies near a sharp corner," Journal of Fluid Mechanics, 18, 1, 1-18. (1964), conducted numerical simulations and theoretical studies on the growth and appearance of fine vortices near the corner of the cavity flow. He believed that there are infinitely many secondary vortices at the corner, which grow with increasing Reynolds number. Figure 2 ).

[0003] Moffat analyzed the causes of the Moffat effect from the perspectives of theoretical research and numerical simulation. From a mathematical point of view, we know that corner points are actually singularities, and when the corner angle is acute or right angle, the curve is not smooth and becomes discontinuous. Therefore, in physical reality, discontinuous phenomena will also appear, such as infinitely many tiny vortices at the corners.

[0004] Our research revealed that as the secondary vortices at the edges grow, they gradually compress the primary vortex while simultaneously inducing new secondary vortices and smaller, fragmented vortices. Figure 3 As the Reynolds number increases, it eventually evolves into turbulence. Figure 4 ).

[0005] Previous research revealed that for isosceles right-angle cavities and square cavities driven by a top cover, the Hopf flow bifurcation points occur around Reynolds numbers Re = 8039 and 8025, respectively. We know that the appearance of a Hopf flow bifurcation point signifies the evolution of the flow from steady to unsteady periodic flow, followed by the appearance of a Neimark-Sacker flow bifurcation point, leading to the evolution of the flow into unsteady quasi-periodic flow, and finally, turbulence.

[0006] Optimizing the aerodynamic layout inside the cavity driven by the top cover to improve the flow field stability and characteristics of the internal flow field in the embedded bomb bay is a problem that needs further research. Summary of the Invention

[0007] To address the problems existing in the prior art, and under the condition of meeting many constraints, this invention proposes an aerodynamic layout of a honeycomb configuration for an embedded bomb bay that improves flow field stability. From a physical perspective, it delays the appearance of the Hopf flow bifurcation point in the flow field inside the embedded bomb bay, slows down the evolution of the flow from a steady state to an unsteady state, thereby improving the flow field stability and flow field characteristics inside the embedded bomb bay.

[0008] The technical solution of this invention is as follows:

[0009] An aerodynamic layout for an embedded bomb bay with a honeycomb-like configuration to improve flow field stability is characterized in that: the main body of the embedded bomb bay cross-section is a hexagonal honeycomb-like configuration, wherein the top surface of the honeycomb-like configuration is open, the other five surfaces are closed walls, the top surface is parallel to the bottom surface, the angle α between the bottom surface and the adjacent surface is 135 degrees, the depth ratio β of the honeycomb-like configuration is L / H = 1.5, where L is the maximum lateral distance of the bomb bay cross-section, and H is the maximum longitudinal height of the bomb bay cross-section.

[0010] When the angle α between the bottom surface and the adjacent surface varies from 90 to 180 degrees, 90 degrees corresponds to a square bomb bay, and 180 degrees corresponds to a trapezoidal bomb bay—two special cases. These two cases no longer possess the characteristics of a honeycomb structure and offer no advantages in structural strength, sound and heat insulation, or weight reduction. Furthermore, their flow field stability is not optimal. When α is 120 degrees, it represents a standard honeycomb structure, exhibiting excellent performance in structural strength, sound and heat insulation, and weight reduction. However, compared to α being 135 degrees (the geometry of this invention), its capacity is smaller, resulting in lower space utilization for the bomb bay. Moreover, α at 135 degrees demonstrates superior flow field stability. When α exceeds 135 degrees, it gradually exceeds the constraints of the fuselage's internal layout design, and the flow field stability also suffers significantly. The constraints of the fuselage's internal layout design specifically refer to the requirement that a bomb bay be placed within a given space within the fuselage's underside. Forcing its placement beyond this space will firstly affect the arrangement of other components within the fuselage and secondly, compromise the structural strength of the fuselage. Therefore, given the aerodynamic shape and internal layout of the aircraft, the bomb bay can only be arranged in a limited area, which must meet the requirements of maximum payload (bomb bay capacity) while also improving the stability of the flow field inside the bay.

[0011] In addition, the present invention also proposes an internal bomb bay, which is embedded in the fuselage and the cross-sectional shape of the bomb bay along the longitudinal direction of the aircraft is the shape corresponding to the above-mentioned aerodynamic layout.

[0012] Beneficial effects

[0013] The honeycomb-like aerodynamic layout for the embedded bomb bay proposed in this invention, while meeting constraints such as structural strength requirements, sound and heat insulation requirements, weight reduction requirements, fuselage internal structural design requirements, and capacity requirements, can significantly improve the stability of the internal flow field in the embedded bomb bay. It fundamentally improves flow field characteristics, effectively suppresses the evolution of fine vortices and secondary vortices, and significantly delays the process of the flow field evolving from a steady state to an unsteady state. Because this optimized design effectively suppresses unsteady flow, especially the premature onset of turbulence, it improves the aerodynamic efficiency of the flow within the bomb bay.

[0014] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0016] Figure 1 : Flow streamline diagrams (steady flow) driven by the top cover of triangular cavity (Re=1000) and square cavity (Re=1000);

[0017] Figure 2 Corner Moffat effect;

[0018] Figure 3 : Flow streamline diagrams (steady flow) of the internal flow driven by the top cover of the triangular cavity (Re=7500) and the square cavity (Re=8000);

[0019] Figure 4 Instantaneous streamline diagrams (turbulence) of the internal flow driven by the top cover of a triangular cavity (Re=50000) and a square cavity (Re=20000);

[0020] Figure 5 Internal bomb bay and simplified 2D diagram;

[0021] Figure 6 : Triangular and square cavity geometry; U, U lid The driving speed of the bomb bay top cover; P1, P2, and P3 are the flow field information acquisition points; x c The location of the center of the computational domain;

[0022] Figure 7 : Unoptimized square bomb bay; L is the characteristic length of the closed end of the square bomb bay;

[0023] Figure 8 : Honeycomb-like geometric shape;

[0024] In the diagram, α represents 135 degrees. To maintain a constant cargo capacity relative to a square bomb bay, the aspect ratio β is a fixed value of 1.5, as indicated in the diagram. This aspect ratio parameter varies with α, and the mathematical relationship between them is as follows: As can be seen, when α changes from 90 degrees to 135 degrees, the depth ratio changes from 1 to 1.5. As α continues to increase, the depth ratio will further increase and exceed the constraints of the internal structural layout design of the fuselage in this application. When the depth ratio β varies between 1 and 1.5, the larger the better, because in this case, a large depth ratio corresponds to a large bomb bay capacity, which can maximize space utilization and payload.

[0025] Figure 9 : Calculation results of cellular-like structure (Re = 13000, steady-state results); (a) streamline diagram, (b) convergence curve of the velocity components at the center point over time; u x Let u be the velocity component in the x-direction of the center point. y The velocity component in the y-direction of the center point;

[0026] Figure 10 Calculation results for cellular-like structures (Re = 14000, non-steady periodic results);

[0027] Figure 11 The critical Reynolds number at which Hopf flow bifurcation occurs for different α values. Detailed Implementation

[0028] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] Internal bomb bays, such as Figure 5 As shown, the flow field stability of the internal flow field is an important factor affecting the performance of the new generation of fighter jets. This embodiment starts from the numerical simulation and theoretical analysis of flow field stability analysis and aerodynamic layout design. Under the condition of meeting the corresponding constraints, it proposes a local optimization design idea for the honeycomb structure of the bomb bay. From the perspective of physical characteristics, it delays the appearance of the Hopf flow bifurcation point in the internal flow field of the embedded bomb bay, slows down the evolution of the flow from a steady state to an unsteady state, thereby improving the flow field stability and improving the flow field characteristics of the internal flow of the embedded bomb bay.

[0030] Based on long-term research on flow field stability optimization and aerodynamic layout optimization design, the applicant has developed a complete research system combining numerical simulation, theoretical analysis, and shape optimization design. This system includes high-efficiency and high-precision numerical simulation algorithms, robust complex shape mesh refinement methods (tree mesh), high-precision complex curve surface boundary processing formats, a comprehensive flow field stability analysis theoretical system (spectral analysis methods, trajectory tracking methods, disturbance attenuation coefficient analysis methods, Poincaré mapping theory, velocity phase diagram analysis methods, flow field topology analysis methods, etc.), and reliable flow field visualization processing techniques and analysis methods. Building upon this research system, the applicant has conducted extensive analysis and research on internal flow fields, such as... Figure 6 The diagram shows the top cover driving the internal flow of an isosceles right-angled cavity and a square cavity.

[0031] Analysis shows that the aerodynamic layout design research of the bomb bay can be completely equivalent to the study of the internal flow driven by the top cover of the cavity, such as... Figure 7 As shown. After extensive research, the applicant discovered two main factors affecting the stability of the internal flow field: the depth ratio λ = L / H and the overall geometry of the cavity. The cavity base angle θ and the overall cavity shape are directly related and change with variations in the cavity geometry. Considering the structural strength requirements, sound and heat insulation requirements, weight reduction requirements, internal fuselage layout design requirements (a larger depth ratio within the range of 1 ≤ λ ≤ 1.5 is better), and capacity requirements of practical applications, this embodiment proposes an optimized aerodynamic layout design scheme for the bomb bay that can improve flow field stability under these constraints. Furthermore, compared to a square bomb bay, it can further improve the structural strength, sound and heat insulation performance, and reduce weight to a certain extent.

[0032] Considering the classic honeycomb configuration, we know that this structure has high structural strength, is lightweight, and is also beneficial for sound and heat insulation. Therefore, the honeycomb configuration for embedded bomb bays is our first choice. However, considering the constant volume constraint, the processing precision requirements for the components are very high. Furthermore, previous extensive research has shown that when α = 135°, the flow within the bomb bay exhibits optimal stability, such as... Figure 11 As shown. In the classic honeycomb structure, α = 120° does not achieve the optimal effect on improving flow field stability, and the depth ratio is only about 1.155, indicating the possibility and demand for further increases.

[0033] from Figure 11 It can be seen that when α equals 135 degrees, the flow inside the bomb bay has optimal stability. When α increases further, the stability of the flow field will gradually decrease, and it cannot meet the requirements of the internal layout design of the fuselage under the same capacity.

[0034] Therefore, considering all the above constraints, we propose a design approach based on a honeycomb-like structure (such as...). Figure 8As shown, this design inherits the typical excellent characteristics of honeycomb structures while maximizing flow field stability. Furthermore, its simple configuration facilitates component processing and manufacturing. Numerical simulation verification and comparative analysis, by observing the delay of the Hopf flow bifurcation point and the suppression of the evolution of secondary vortices and fine vortices within the flow field, confirm that this optimized aerodynamic layout design can significantly improve the flow field stability within the bomb bay.

[0035] Overall, the numerical simulation results show that the aerodynamic layout optimization design research for the stability of the internal flow field of the embedded bomb bay has achieved ideal results, which can greatly improve the flow field stability of the embedded bomb bay.

[0036] Based on previous research and the conclusions of other scholars, we know that for a square internal bomb bay, the Hopf flow bifurcation point occurs between Re = (8000, 8050). This indicates that when the Reynolds number is between Re = (8000, 8050), the flow evolves from a steady state to a non-steady periodic state, then to a non-steady quasi-periodic flow, and finally to turbulence. The conclusion of this embodiment shows that for the honeycomb-like structure optimization scheme, when the Reynolds number is 13000, the flow is steady, as shown below. Figure 9 The figure shows the flow field topology at this Reynolds number and the velocity variation curves from the data acquisition point over time. Figure 10 The calculation results for a Reynolds number of 14000 under the same optimization scheme are given, combined with Figure 10 From the velocity-time curve, velocity spectrum, and velocity phase diagram, it is clear that the flow has now become unsteady periodic. This indicates that the Hopf flow bifurcation point has been effectively delayed, and the unoptimized (square bomb bay) Re... H =8025±25 was postponed to the optimized (cellular-like structure) Re H =13500±500. Compared to the standard square embedded bomb bay, the honeycomb structure has extremely strong flow field stability, which can provide a very stable internal flow field for the bomb bay.

[0037] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An internal embedded missile bay honeycomb configuration aerodynamic layout for improving the stability of the flow field, characterized in that: The inner-embedded missile cabin section body is a hexagonal honeycomb configuration layout, wherein the top surface is open, the other five surfaces are closed wall surfaces, the top surface is parallel to the bottom surface, the angle α between the bottom surface and the adjacent surface is 135 degrees, the longitudinal depth ratio β of the honeycomb configuration is L / H=1.5, L is the maximum transverse distance of the missile cabin section, and H is the maximum longitudinal height of the missile cabin section.

2. The internal embedded missile bay honeycomb configuration aerodynamic layout according to claim 1, wherein: The flow field in the missile cabin cavity is still in a steady state when the Reynolds number is 13000.

3. An internalized pod, characterized by: The missile cabin is embedded in the belly of the aircraft, and the cross-sectional shape of the missile cabin perpendicular to the longitudinal direction of the aircraft is the shape of the aerodynamic layout in claim 1.

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