Equivalent analysis method for interference characteristics of shock wave / flexible sea surface flow field

Abstract

The invention provides an equivalent analysis method for interference characteristics of a shock wave / flexible sea surface flow field, which comprises the following steps of: based on numerical simulation, analyzing aerodynamic / flow evolution characteristics of an aircraft during high-speed flight on a near sea surface, and discussing change rules of shock wave attenuation degree and shock wave intensity; on the basis, the feasibility of carrying out numerical calculation by replacing the flexible sea surface with the rigid ground is provided; and finally, verifying the feasibility of the equivalent calculation thought of replacing the flexible sea surface with the rigid ground by comparing the space flow field structure of the aircraft, the contour lines of the rigid ground and the flexible sea surface and the aerodynamic force suffered by the aircraft. According to the method, the shock wave attenuation degree and the shock wave intensity under different flight Mach numbers are analyzed, the equivalent calculation idea of replacing the flexible deformation sea surface with the rigid ground is provided, the calculation research difficulty of solving the shock wave / flexible sea surface flow field interference characteristics can be simplified, the calculation efficiency is greatly improved, and the calculation precision is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft and relates to an equivalent analysis method for shock wave / flexible sea surface flow field interference characteristics. Background Art

[0002] When an aircraft flies near the sea surface, the flow field boundary effect caused by the sea surface cannot be ignored. Existing studies have mainly focused on the low-speed field, and found that the flow field boundary restriction will cause significant near-wall effects, resulting in changes in the flow structure between the lower surface of the aircraft and the flow field boundary, and directly affecting the aerodynamic characteristics of the aircraft. In the high-speed field, there are currently few studies and no certain understanding has been formed. However, with the continuous increase in the flight speed of aircraft, it is increasingly important to carry out research on aerodynamic characteristics under high-speed flight near the sea surface. Compared with low-speed flight, when an aircraft flies at high speed near the sea surface, there will be complex wave system structures in the spatial flow field. When the flight altitude is close to the sea surface, these wave system structures will propagate and act on the sea surface in a very short time, resulting in complex shock wave / sea surface mutual interference: on the one hand, the shock wave will cause changes in the shape of the sea surface, indirectly affecting the interference effect between the shock wave and the sea surface at the next moment; on the other hand, the shock wave will be reflected after acting on the sea surface, and the reflected shock wave may propagate to the lower surface of the aircraft again, thereby changing the surface pressure distribution and wall flow characteristics of the aircraft, seriously threatening flight safety. The above-mentioned complex shock wave / sea surface interaction brings great difficulties to the study of the aerodynamic characteristics of aircraft flying at high speed near the sea surface. Due to the characteristics of flexible deformation of the sea surface, to realize the study of shock wave / sea surface flow field interference, it is necessary to accurately characterize the sea surface deformation process, which inevitably consumes a lot of computing resources, and the complex multiphase flow characteristics of the interference area are also very likely to cause the divergence of numerical calculations.

[0003] When an aircraft flies at high speed near the sea surface, there are usually the following technical difficulties: on the one hand, water is usually regarded as an incompressible medium, while air needs to consider the drastic compression effect. To realize the flow field calculation near the interface between seawater and air, it is necessary to overcome the computational difficulties caused by the difference in compressibility of the media on both sides of the interface. If it is not handled properly, it is easy to cause non-physical solutions in numerical simulations and even cause computational divergence; on the other hand, the sea surface is flexible and will change its geometric shape, especially when the significant pressure difference before and after the shock wave acts on the sea surface, it will induce a certain degree of deformation of the sea surface. The detailed description of this deformation effect may require a large number of computational grids, which puts higher requirements on computing power. In turn, the deformed sea surface shape will also affect the interference characteristics between the shock wave and the sea surface at the next moment, further increasing the difficulty of studying the shock wave / sea surface interference mechanism. Summary of the invention

[0004] The present invention aims to solve at least one of the problems existing in the prior art.

[0005] Therefore, the present invention provides an equivalent analysis method for the shock wave / flexible sea surface flow field interference characteristics. This method mainly focuses on the above two technical difficulties. By analyzing the shock wave attenuation degree and shock wave intensity at different flight Mach numbers, it proposes an equivalent calculation idea of using a rigid ground to replace the flexible deformed sea surface, which can simplify the calculation research difficulty of solving the shock wave / flexible sea surface flow field interference characteristics, greatly improve the calculation efficiency, and ensure the calculation accuracy.

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

[0007] An equivalent analysis method for the shock wave / flexible sea surface flow field interference characteristics, and the specific steps of the equivalent analysis method are as follows:

[0008] Step 1, when the aircraft flies over the sea, a shock wave is generated, and the shock wave causes the sea surface to deform. The flow field characteristics of the gas-liquid two-phase flow under the deformation of the sea surface during the high-speed sea-skimming process of the aircraft are numerically simulated.

[0009] Step 2, analyze the flow field characteristics of the gas-liquid two-phase flow obtained in Step 1 from two factors: the shock wave attenuation degree and the shock wave intensity, and determine the equivalent calculation idea of "using a rigid ground to replace the flexible sea surface" according to the analysis results.

[0010] Step 3, verify the feasibility of the equivalent calculation idea of "using a rigid ground to replace the flexible sea surface" from three aspects: the comparison of the aircraft space flow field structure, the comparison of the contour lines of the rigid ground and the flexible sea surface, and the comparison of the aerodynamic forces received by the aircraft.

[0011] Further, in Step 1, during the numerical simulation calculation process, three sample models are established. The sea surface height and sea surface wave shape of the three sample models are the same, and the flight Mach numbers of the aircraft in the three sample models are different. Let the Mach numbers of the three sample models be Ma1, Ma2, and Ma3, respectively, and Ma1 < Ma2 < Ma3; the vof multiphase flow calculation model is used to track the water-gas interface when the aircraft flies over the sea, and then the flow field characteristics of the gas-liquid two-phase flow are obtained.

[0012] Further, when using the vof multiphase flow calculation model to track the water-gas interface when the aircraft flies over the sea, the boundary conditions of the contour line need to be set according to the flow field calculation state.

[0013] The setting method is as follows: when the aircraft passes above the first wave period, the contour lines of both the rigid ground and the flexible sea surface are set as impenetrable walls; after the calculation of the first wave period is completed, the rigid ground continues to use the original boundary conditions, and the flexible sea surface changes the contour line to interior that can perform data interaction and then continues the calculation.

[0014] Furthermore, in step 2, the process of analyzing the flow field characteristics of the gas-liquid two-phase flow obtained in step 1 from the two factors of shock wave attenuation degree and shock wave intensity is as follows:

[0015] ① Shock wave attenuation degree: According to the flow field characteristics of the gas-liquid two-phase flow obtained in step 1, the greater the flight Mach number of the aircraft, the smaller the shock wave angle of the space wave system, and the longer the propagation distance of the shock wave in the air. The longer the propagation distance of the shock wave in the air, the greater the shock wave attenuation caused by the air viscosity effect. The greater the shock wave attenuation, the smaller the impact of the shock wave on the flexible sea surface, that is, the smaller the deformation of the flexible sea surface caused by the shock wave;

[0016] ② Shock wave intensity: The change of flight Mach number will lead to the change of shock wave intensity, as shown in formula (1), where P is the shock wave intensity, p 前 、p 后 are the wavefront pressure and the waveback pressure respectively; at the same flight altitude, the wavefront pressure p of the three sample models 前 are equal, the shock wave intensity P mainly depends on the back pressure p of the shock wave / sea surface interference zone 后 , the greater the post-wave pressure, the greater the shock wave intensity P, the greater the impact of the shock wave on the flexible sea surface, that is, the greater the deformation of the flexible sea surface affected by the shock wave;

[0017]

[0018] Post-wave pressure p 后 The value can be obtained by the numerical calculation results of different flight Mach numbers Ma1, Ma2, and Ma3 in step 1. By analyzing the back-wave pressure value, it is found that the back-wave pressure p of the shock wave / sea surface interference zone under different flight Mach numbers 后 The difference between them is within the preset range, which is equivalent to the back pressure p of the shock wave / sea surface interference zone at different flight Mach numbers. 后 are equal, so the flexible sea surface deformation effect caused by the shock wave intensity P can be ignored;

[0019] In summary, from the perspective of shock wave attenuation and shock wave intensity, when the flight Mach number increases, the shock wave attenuation plays a major role. The larger the flight Mach number, the greater the shock wave attenuation, and the weaker the deformation effect of the flexible sea surface caused by the shock wave. Based on this, it is only necessary to compare the space flow field structure of the aircraft under Ma1, the contours of the rigid ground and the flexible sea surface, and the aerodynamic force exerted on the aircraft to reflect the shock wave / flexible sea surface flow field interference characteristics within the range of Ma1 to Ma3. After analysis, it is found that the shock wave generated by the aircraft during sea-skimming flight under Ma1 will not have a deformation effect on the flexible sea surface. Based on this, an equivalent calculation idea of ​​using rigid ground instead of flexible sea surface is proposed.

[0020] Furthermore, in step three, the process of verification from the comparison of the space flow field structure of the aircraft is as follows:

[0021] When the water-air interface line is horizontal, numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface are carried out. The flight Mach number and flight altitude of the rigid ground and the flexible sea surface are the same. According to the calculation results, the water structure below the horizontal line of the flexible sea surface has no effect on the space flow field of the aircraft.

[0022] When the water-air interface line is a wave line, numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface are carried out. The flight Mach number and flight altitude of the rigid ground and the flexible sea surface are the same. According to the calculation results, the water structure below the wave line of the flexible sea surface has no effect on the space flow field of the aircraft.

[0023] In summary, under the horizontal profile and the wave profile, the water structure below the flexible sea surface profile has no direct impact on the spatial flow field of the aircraft. Therefore, the rigid ground can be used instead of the flexible sea surface.

[0024] Furthermore, in step three, the verification process is performed by comparing the contours of the rigid ground and the flexible sea surface:

[0025] Numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface were carried out. The flight Mach numbers and flight altitudes of the rigid ground and the flexible sea surface are the same. According to the calculation results, the shock wave has no impact on the contours of the rigid ground and the flexible sea surface. Therefore, the rigid ground can be used instead of the flexible sea surface.

[0026] Furthermore, in step 3, the process of verifying the aerodynamic force on the aircraft is as follows:

[0027] Numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface were carried out. The flight Mach numbers and flight altitudes of the rigid ground and the flexible sea surface are the same. According to the calculation results, the rigid ground and the flexible sea surface have no effect on the aerodynamic force of the aircraft. Therefore, the rigid ground can be used instead of the flexible sea surface.

[0028] By applying the above technical solution, the present invention has the following beneficial effects:

[0029] (1) The present invention closely focuses on the ability requirements of an aircraft flying at high speed near the sea surface. Based on numerical simulation methods, studies on the interference effects of spatial wave systems with rigid ground / flexible sea surface at different flight Mach numbers have been carried out. By analyzing the shock wave attenuation degree and shock wave intensity, starting from the calculation results, the equivalent calculation idea of "replacing the flexible with the rigid", that is, using a rigid ground to replace the flexible deformed sea surface, is proposed. By comparing the spatial flow field structure of the aircraft, the contour line changes of the rigid ground and the flexible sea surface, and the changes in the aerodynamic data received by the aircraft, the influence law of different flight Mach numbers on the shock wave / sea surface interference characteristics under the same flight altitude and sea wave level is analyzed, and the feasibility of using a rigid ground to replace the flexible sea surface for numerical calculation is obtained. Based on the equivalent calculation idea of using a rigid ground to replace the flexible deformed sea surface proposed by the present invention, the calculation efficiency can be greatly improved, the calculation accuracy can be guaranteed, and key technical support can be provided for the technical research on the aircraft flying at high speed near the sea surface.

[0030] (2) In the equivalent calculation idea of "replacing the flexible with the rigid", that is, using a rigid ground to replace the flexible deformed sea surface, of the present invention, on the one hand, by using a rigid grid, there is no grid deformation and reconstruction process, which will greatly compress the grid processing time and improve the calculation efficiency; on the other hand, the rigid grid can effectively guarantee the calculation accuracy and is not easily prone to calculation divergence. Brief Description of the Drawings

[0031] The accompanying drawings included are used to provide a further understanding of the embodiments of the present invention. They form a part of the description and are used to illustrate the embodiments of the present invention and, together with the written description, to explain the principles of the present invention. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0032] Figure 1 A research idea diagram of an equivalent analysis method for the interference characteristics of a shock wave / flexible sea surface flow field is given;

[0033] Figure 2 A schematic diagram of the interaction between a shock wave and the sea surface when an aircraft flies near the sea surface is given. In the figure, A and C represent the interference areas between the shock wave and the sea surface, B represents the interaction area between the shock wave reflected by the sea surface and the lower surface of the aircraft, and Ma represents the incoming flow Mach number;

[0034] Figure 3 A schematic diagram of the interaction between the spatial wave system of an aircraft and the sea surface at different flight Mach numbers is given.

[0035] In the figure, Ma1, Ma2, and Ma3 represent three different flight Mach numbers, with the magnitudes in sequence: Ma1 < Ma2 < Ma3. The blue dotted lines in the interference area represent the deformed sea surface, and the black solid lines represent the sea surface before deformation;

[0036] Figure 4 The comparison of space pressure cloud diagrams under different flight Mach numbers is given;

[0037] Figure 5 The comparison of the pressure behind the wave at the profile under different flight Mach numbers is given;

[0038] Figure 6 The pressure cloud diagram comparison between the rigid ground and the flexible sea surface under the horizontal / wavy line is given, (a) is the horizontal line, (b) is the wavy line;

[0039] Figure 7 The comparison diagram of the calculation results of the rigid ground and the flexible sea surface under the wave line is given, (a) is the comparison of the contour lines, and (b) is the comparison of the aerodynamic forces acting on the aircraft. DETAILED DESCRIPTION

[0040] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0042] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0043] This embodiment provides an equivalent analysis method for the interference characteristics of shock waves / flexible sea surface flow fields. When an aircraft flies at high speed near the sea surface, the shape of the sea surface will fluctuate to a certain extent, and the degree of fluctuation will be affected by different factors such as sea breeze and ocean currents. To achieve safe flight, there must be a minimum safe flight distance between the aircraft and the sea surface, that is, the minimum safe flight altitude. If the altitude from the sea is less than the minimum safe flight altitude, seawater or waves may directly act on the surface of the aircraft during flight, seriously changing the surface pressure distribution of the aircraft and causing it to fall into the sea; therefore, in this embodiment, the altitude of the aircraft from the sea is greater than the minimum safe flight altitude, and there is no direct interaction between seawater and the surface of the aircraft. The focus is on the interaction between the aircraft space wave system (i.e., shock waves) and the sea surface.

[0044] In addition, see Appendix Figure 2 When the aircraft is flying at high speed near the sea surface, the shock wave generated by it will act on area A of the sea surface, and may propagate to area B of the lower surface of the aircraft after reflection from the sea surface, and may propagate to area C of the sea surface again after reflection again; therefore, areas A and C of the sea surface are the interaction areas of shock wave / flexible sea surface. Compared with area A, when the shock wave propagates to area C, which is farther away, the energy of the shock wave in area C has been greatly attenuated. Therefore, the shock wave / flexible sea surface interference effect in area A is stronger than that in area C. This embodiment mainly performs an equivalent analysis on the shock wave / flexible sea surface interference effect in area A.

[0045] The equivalent analysis method of this embodiment is: based on numerical simulation, the aerodynamic / flow evolution characteristics of the aircraft when flying at high speed near the sea surface are analyzed, and the change law of shock wave attenuation and shock wave intensity is discussed; on this basis, the feasibility of using rigid ground instead of flexible sea surface for numerical calculation is proposed; finally, by comparing the spatial flow field structure of the aircraft, the contour lines of the rigid ground and flexible sea surface, and the aerodynamic force on the aircraft, the feasibility of the equivalent calculation idea of ​​"using rigid ground instead of flexible sea surface" is verified. See Appendix Figure 1, the specific steps of the equivalent analysis method are as follows:

[0046] Step 1: Conduct numerical calculations on the flow field characteristics of the gas-liquid two-phase flow during the sea-skimming flight of the aircraft. When the aircraft conducts sea-skimming flight, shock waves are generated, and the shock waves cause deformation of the sea surface. Through numerical simulation, the flow field characteristics of the gas-liquid two-phase flow under the deformation of the sea surface during the high-speed sea-skimming process of the aircraft are obtained.

[0047] During the numerical simulation calculation process, three sample models are established. The sea surface height and sea surface wave shape of the three sample models are the same, and the flight Mach numbers of the aircraft in the three sample models are different. Let the Mach numbers of the three sample models be Ma1, Ma2, and Ma3, respectively, and Ma1 < Ma2 < Ma3; see the appendix Figure 3 , the vof multiphase flow calculation model is used to track the water-gas interface during the sea-skimming flight of the aircraft, and then the flow field characteristics of the gas-liquid two-phase flow are obtained. The vof multiphase flow calculation model is a relatively mature free surface capture method at present, which will not be elaborated here;

[0048] When using the vof multiphase flow calculation model to track the water-gas interface during the sea-skimming flight of the aircraft, the boundary conditions of the contour line need to be set according to the flow field calculation state. The setting method is as follows: When the aircraft passes above the first wave period, the contour lines of the rigid ground and the flexible sea surface are both set as impenetrable walls to avoid the mixing of the gas phase and the liquid phase in the unstable flow field, resulting in calculation divergence. After the calculation of the first wave period is completed, the rigid ground still continues to use the original boundary conditions, and the flexible sea surface changes the contour line to interior that can perform data interaction and then continues the calculation.

[0049] Step 2: Analyze the flow field characteristics of the gas-liquid two-phase flow obtained in Step 1:

[0050] Analyze from two factors: the shock wave attenuation degree and the shock wave intensity:

[0051] ① Shock wave attenuation degree: See the appendix Figure 4 , according to the flow field characteristics of the gas-liquid two-phase flow obtained in Step 1, when the aircraft flies at high speed near the sea surface, the greater the flight Mach number, the smaller the shock wave angle of the spatial wave system, and the longer the propagation distance of the shock wave in the air. Since Ma1 < Ma2 < Ma3, the propagation distances of the shock waves corresponding to Ma1, Ma2, and Ma3 in the air increase in turn. Considering the viscous effect of the air, the longer the propagation distance of the shock wave in the air, the greater the shock wave attenuation caused by the viscous effect, and the greater the shock wave attenuation, the smaller the impact of the shock wave on the flexible sea surface, that is, the smaller the deformation of the flexible sea surface caused by the shock wave (that is, the smaller the deformation of the water-gas interface);

[0052] ② Shock wave intensity: The change of the flight Mach number will cause the change of the shock wave intensity, as shown in formula (1). Where P is the shock wave intensity, p前 、p 后 are the wavefront pressure and waveback pressure, respectively. At the same flight altitude, the wavefront pressure p of the three sample models 前 The shock wave intensity P mainly depends on the back pressure p of the shock wave / sea surface interference zone. 后 , the greater the post-wave pressure, the greater the shock wave intensity P, the greater the impact of the shock wave on the flexible sea surface, that is, the greater the deformation of the flexible sea surface affected by the shock wave (that is, the greater the deformation of the water-air interface);

[0053]

[0054] Post-wave pressure p 后 The value can be obtained through the numerical calculation results of different flight Mach numbers (Ma1, Ma2, Ma3) in step 1, such as Figure 5 By analyzing the post-wave pressure value, it is found that the post-wave pressure p in the shock wave / sea surface interference zone at different flight Mach numbers 后 They are basically equal, so the flexible sea surface deformation effect caused by the shock wave intensity P is very weak.

[0055] In summary, from the perspective of the two factors of shock wave attenuation and shock wave intensity, when the flight Mach number increases, the main factor is the shock wave attenuation. The larger the flight Mach number, the greater the shock wave attenuation, and the weaker the deformation effect of the flexible sea surface caused by the shock wave. Based on this, it is only necessary to compare the spatial flow field structure of the aircraft under Ma1, the contours of the rigid ground and the flexible sea surface, and the aerodynamic force exerted on the aircraft to reflect the shock wave / flexible sea surface flow field interference characteristics within the range of Ma1 to Ma3. After analysis, it was found that the shock waves generated by the aircraft during sea skimming flight under Ma1 will not have a deformation effect on the flexible sea surface; based on this, this embodiment proposes an equivalent calculation idea of ​​replacing the flexible sea surface with a rigid ground;

[0056] Step 3: Verify the feasibility of the equivalent calculation idea of ​​using rigid ground instead of flexible sea surface:

[0057] The feasibility is verified from three aspects: the comparison of the space flow field structure of the aircraft, the comparison of the contour lines of the rigid ground and the flexible sea surface, and the comparison of the aerodynamic forces acting on the aircraft:

[0058] ① Comparison of space flow field structures of aircraft:

[0059] Under the horizontal profile of the air-water interface, numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface are carried out. The flight Mach number and flight altitude of the rigid ground and the flexible sea surface are the same. The calculation results are shown in the attached Figure 6 (a) According to the calculation results, the flow field structures of the rigid ground and the flexible sea surface are basically the same, and the water structure below the horizontal line of the flexible sea surface has no direct impact on the space flow field of the aircraft;

[0060] Under the wave-shaped line of the water-air interface, numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface are carried out. The flight Mach number and flight altitude of the rigid ground and the flexible sea surface are the same. The calculation results are shown in the attached Figure 6 (b) According to the calculation results, the flow field structures of the rigid ground and the flexible sea surface are basically the same, and the water structure below the wave line of the flexible sea surface has no direct impact on the space flow field of the aircraft;

[0061] Among them, the deformed contour of the flexible sea surface can be obtained by the Vof multiphase flow calculation model.

[0062] In summary, we can see that under the horizontal profile and the wave profile, the flow field structures of the rigid ground and the flexible sea surface are basically the same. The water structure below the flexible sea surface profile has no direct impact on the spatial flow field of the aircraft. Therefore, the rigid ground can be used instead of the flexible sea surface.

[0063] ②Contour comparison between rigid ground and flexible sea surface:

[0064] Numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface were carried out. The flight Mach number and the flight altitude of the rigid ground and the flexible sea surface were the same. The calculation results are shown in the attached Figure 7 (a) According to the calculation results, the contours of the rigid ground and the flexible sea surface are basically the same, and the sea surface deformation effect caused by the shock wave is weak. Therefore, the shock wave has no direct impact on the contours of the rigid ground and the flexible sea surface. Therefore, the rigid ground can be used instead of the flexible sea surface.

[0065] ③ Comparison of aerodynamic forces on aircraft:

[0066] Numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface were carried out. The flight Mach number and the flight altitude of the rigid ground and the flexible sea surface were the same. The calculation results are shown in the attached Figure 7 (b) According to the calculation results, the rigid ground and the flexible sea surface have no direct impact on the aerodynamic force of the aircraft. Therefore, the rigid ground can be used instead of the flexible sea surface.

[0067] Through the above comparison, the effectiveness of the equivalent calculation idea of ​​"replacing flexibility with rigidity" is verified, which provides effective support for the efficient and high-precision numerical simulation of subsequent aircraft under near-sea flight conditions.

[0068] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0069] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An equivalent analysis method for shock wave / flexible sea surface flow field interference characteristics, characterized in that: The specific steps of the equivalent analysis method are as follows: Step 1: When the aircraft flies over the sea surface, a shock wave is generated, which causes the sea surface to deform. The flow field characteristics of the gas-liquid two-phase flow under the sea surface deformation during the high-speed sea-skimming process of the aircraft are numerically simulated; Step 2: Analyze the flow field characteristics of the gas-liquid two-phase flow obtained in Step 1 from two factors: the shock wave attenuation degree and the shock wave intensity. Determine the equivalent calculation idea of "replacing the flexible sea surface with a rigid ground" according to the analysis results; Step 3: Verify the feasibility of the equivalent calculation idea of "replacing the flexible sea surface with a rigid ground" from three aspects: the comparison of the aircraft spatial flow field structure, the comparison of the contour lines of the rigid ground and the flexible sea surface, and the comparison of the aerodynamic forces acting on the aircraft.

2. The equivalent analysis method of shock wave / flexible sea surface flow field interference characteristics according to claim 1, characterized in that: In Step 1, during the numerical simulation calculation process, three sample models are established. The sea surface height and sea surface wave shape of the three sample models are the same, and the flight Mach numbers of the aircraft in the three sample models are different. Let the Mach numbers of the three sample models be Ma1, Ma2, and Ma3, respectively, and Ma1 < Ma2 < Ma3; The vof multiphase flow calculation model is used to track the water-air interface during the sea-skimming flight of the aircraft, and then the flow field characteristics of the gas-liquid two-phase flow are obtained.

3. The equivalent analysis method of shock wave / flexible sea surface flow field interference characteristics as claimed in claim 2, characterized in that: When using the vof multiphase flow calculation model to track the water-air interface during the sea-skimming flight of the aircraft, the boundary conditions of the contour line need to be set according to the flow field calculation state; The setting method is as follows: When the aircraft passes above the first wave cycle, the contour lines of both the rigid ground and the flexible sea surface are set as impenetrable walls; After the calculation of the first wave cycle is completed, the rigid ground continues to use the original boundary conditions, while the flexible sea surface changes the contour line to an interior that can perform data interaction and then continues the calculation.

4. The equivalent analysis method of shock wave / flexible sea surface flow field interference characteristics according to claim 1, characterized in that: In Step 2, the process of analyzing the flow field characteristics of the gas-liquid two-phase flow obtained in Step 1 from two factors: the shock wave attenuation degree and the shock wave intensity is as follows: ① Shock wave attenuation degree: According to the flow field characteristics of the gas-liquid two-phase flow obtained in Step 1, the greater the flight Mach number of the aircraft, the smaller the shock wave angle of the spatial wave system, the longer the propagation distance of the shock wave in the air, and the greater the shock wave attenuation caused by the air viscosity effect. The greater the shock wave attenuation, the smaller the impact of the shock wave on the flexible sea surface, that is, the smaller the deformation of the flexible sea surface caused by the shock wave; ② Shock wave intensity: The change of flight Mach number will lead to the change of shock wave intensity, as shown in formula (1), where P is the shock wave intensity, p 前 、p 后 are the wavefront pressure and the waveback pressure respectively; at the same flight altitude, the wavefront pressure p of the three sample models 前 are equal, the shock wave intensity P mainly depends on the back pressure p of the shock wave / sea surface interference zone 后 , the greater the post-wave pressure, the greater the shock wave intensity P, the greater the impact of the shock wave on the flexible sea surface, that is, the greater the deformation of the flexible sea surface affected by the shock wave; Post-wave pressure p 后 The value can be obtained by the numerical calculation results of different flight Mach numbers Ma1, Ma2, and Ma3 in step 1. By analyzing the back-wave pressure value, it is found that the back-wave pressure p of the shock wave / sea surface interference zone under different flight Mach numbers 后 The difference between them is within the preset range, which is equivalent to the back pressure p of the shock wave / sea surface interference zone at different flight Mach numbers. 后 are equal, so the flexible sea surface deformation effect caused by the shock wave intensity P can be ignored; In summary, from the two factors of shock wave attenuation degree and shock wave intensity, when the flight Mach number increases, the main factor is the shock wave attenuation degree. The greater the flight Mach number, the greater the shock wave attenuation, and the weaker the deformation effect of the shock wave on the flexible sea surface; Based on this, only by comparing the aircraft spatial flow field structure, the contour lines of the rigid ground and the flexible sea surface, and the aerodynamic forces acting on the aircraft under Ma1, the shock wave / flexible sea surface flow field interference characteristics in the range from Ma1 to Ma3 can be reflected; After analysis, it is found that the shock wave generated during the sea-skimming flight of the aircraft under Ma1 will not cause deformation of the flexible sea surface; Based on this, the equivalent calculation idea of replacing the flexible sea surface with a rigid ground is proposed.

5. The equivalent analysis method of shock wave / flexible sea surface flow field interference characteristics as claimed in claim 1, characterized in that: In Step 3, the process of verifying from the comparison of the aircraft spatial flow field structure is as follows: When the water-air interface line is horizontal, numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface are carried out. The flight Mach number and flight altitude of the rigid ground and the flexible sea surface are the same. According to the calculation results, the water structure below the horizontal line of the flexible sea surface has no effect on the space flow field of the aircraft. When the water-air interface line is a wave line, numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface are carried out. The flight Mach number and flight altitude of the rigid ground and the flexible sea surface are the same. According to the calculation results, the water structure below the wave line of the flexible sea surface has no effect on the space flow field of the aircraft. In summary, under the horizontal profile and the wave profile, the water structure below the flexible sea surface profile has no direct impact on the spatial flow field of the aircraft. Therefore, the rigid ground can be used instead of the flexible sea surface.

6. The equivalent analysis method of shock wave / flexible sea surface flow field interference characteristics according to claim 1, characterized in that: In step 3, the verification process from the comparison of the contours of the rigid ground and the flexible sea surface is as follows: Numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface were carried out. The flight Mach numbers and flight altitudes of the rigid ground and the flexible sea surface are the same. According to the calculation results, the shock wave has no impact on the contours of the rigid ground and the flexible sea surface. Therefore, the rigid ground can be used instead of the flexible sea surface.

7. The equivalent analysis method of shock wave / flexible sea surface flow field interference characteristics as claimed in claim 1, characterized in that: In step 3, the process of verification based on the aerodynamic force applied to the aircraft is as follows: Numerical calculations of the flow field characteristics of the rigid ground and the flexible sea surface were carried out. The flight Mach numbers and flight altitudes of the rigid ground and the flexible sea surface are the same. According to the calculation results, the rigid ground and the flexible sea surface have no effect on the aerodynamic force of the aircraft. Therefore, the rigid ground can be used instead of the flexible sea surface.

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