A simulation method for internal backward multi-body separation based on delivery channel

Abstract

The present invention relates to the technical field of multi-body separation of aerospace aircraft, and discloses a simulation method for internal backward multi-body separation based on a delivery channel, including: grid generation: constructing a basic parabolic delivery channel for internal backward multi-body separation of an aircraft, constructing a parabolic delivery channel considering uncertainty based on the basic parabolic delivery channel, and generating a multi-scale gradient mixed overlapping grid; strong shear and strong time-varying flow simulation: based on the multi-scale gradient mixed overlapping grid, simulating the strong shear flow characteristics in the aircraft internal separation wake area based on an adaptive low-speed preprocessing method, and simulating the strong time-varying flow characteristics in the aircraft internal separation wake area based on a strong time-varying flow field budget method and a variable time step method. The present invention can effectively improve the prediction accuracy of the aircraft internal backward multi-body separation, and solve the problem of low numerical simulation accuracy of internal backward delivery separation.

Description

Technical Field

[0001] The invention relates to the technical field of multi-body separation of aerospace vehicles, and in particular to an internal rearward multi-body separation simulation method based on a delivery channel. Background Art

[0002] The separation of projectiles from aircraft (also known as aircraft-missile separation) is a typical unsteady multi-body separation problem. Common aircraft-missile separations are divided into external attachment separation, internal attachment separation and internal loading separation. In external attachment separation, the projectiles are attached to the wings or belly of the aircraft, and are ejected downward from the aircraft; internal loading separation refers to the projectiles being loaded in the internal bomb bay of the aircraft and dropped downward from the bomb bay; internal loading separation refers to the projectiles being loaded inside the aircraft and ejected backward from the tail of the aircraft. The carrier for internal loading separation is usually a large-capacity transport aircraft, which can carry a large number of projectiles.

[0003] Before the flight test, the safety of aircraft-missile separation is often evaluated by numerical simulation methods. Among the three aircraft-missile separation methods, external separation and internal separation are relatively common. Their characteristics are that the droplets are ejected downward and separated. The droplets can quickly get rid of the interference of the carrier aircraft and quickly enter the uniform flow area. The numerical simulation methods are also relatively mature. However, internal multi-body separation has its own characteristics. Its characteristics are: ① The droplets are ejected backward from the tail of the aircraft, the release separation time is relatively long, and the droplets are in the interference of the carrier aircraft wake for a long time; ② The separation trajectory of the droplets is similar to a parabola, which is affected by both the backward ejection speed and the gravity acceleration. The separation trajectory has typical parabolic characteristics; ③ The separation trajectory of the droplets is uncertain. Since the ejection speed of the ejection mechanism cannot guarantee that the ejection speed is constant every time, and the aircraft is also faced with multiple uncertain factors such as gusts, shaking, and unstable airflow in the actual flight process, the separation trajectory of the droplets is also uncertain. ④ The wake of the aircraft presents strong shear characteristics. In the wake shear area, the airflow velocity is low and there is a strong separation vortex. Outside the wake shear area, there is a high-speed carrier turbulence. ⑤ The wake of the aircraft is usually an unsteady airflow, and the flow field characteristics change dramatically with time. The overall performance is a strong time-varying feature. In this case, the drop is greatly disturbed by the strong time-varying wake when it is separated.

[0004] Due to the particularity of interior rearward separation, there has been a lack of good numerical simulation methods for a long time, resulting in low accuracy of numerical simulation of interior rearward separation. However, the application scenarios and demands of interior rearward separation are increasing, and it is urgent to develop a high-fidelity numerical simulation method for interior rearward separation. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a simulation method for built-in backward multi-body separation based on a delivery channel in view of the characteristics of built-in backward separation, constructs a hybrid grid considering the uncertain parabolic delivery channel, adopts low-speed preprocessing technology to improve the simulation accuracy of the strong shear region of the wake, and adopts a strong time-varying flow field budget method and a variable time step technology to improve the simulation accuracy of the backward separation of the strong time-varying flow field of the wake, which can solve the problem of low numerical simulation accuracy of built-in backward delivery separation.

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

[0007] A simulation method for internal backward multi-body separation based on a delivery channel, comprising:

[0008] Grid generation: construct a basic parabolic delivery channel for rearward multi-body separation inside the aircraft, construct a parabolic delivery channel considering uncertainty based on the basic parabolic delivery channel, and generate multi-scale gradient mixed overlapping grids;

[0009] Strong shear and strong time-varying flow simulation: According to the multi-scale gradient mixed overlapping grid, the strong shear flow characteristics in the separation wake area inside the aircraft are simulated based on the adaptive low-speed preprocessing method, and the strong time-varying flow characteristics in the separation wake area inside the aircraft are simulated based on the strong time-varying flow field budget method and the variable time step method; the strong shear flow characteristics include flow characteristics with shear characteristics higher than a first threshold, and the strong time-varying flow characteristics include flow characteristics with flow field characteristics changing with time higher than a second threshold.

[0010] Furthermore, the construction of a basic parabolic delivery channel for rearward multi-body separation inside an aircraft includes: constructing a basic parabolic delivery channel for rearward multi-body separation inside an aircraft based on the axial, lateral and longitudinal initial separation positions of the delivery objects, based on the rearward ejection speed, the parabolic formula and the lateral envelope.

[0011] Furthermore, a parabolic delivery channel taking uncertainty into consideration is constructed based on the basic parabolic delivery channel, including: amplifying the uncertainty multiples on the basis of the basic parabolic delivery channel according to the uncertainty of axial, lateral and longitudinal separation conditions and the uncertainty of aerodynamic conditions, so as to obtain the parabolic delivery channel taking uncertainty into consideration.

[0012] Furthermore, based on the strong time-varying flow field budget method, the strong time-varying flow characteristics in the aircraft internal separation wake area are simulated, including: pre-calculating the number of unsteady physical time steps before the internal separation movement of the dropped object to obtain a regularly oscillating strong time-varying wake field.

[0013] Furthermore, based on the variable time step method, the strongly time-varying flow characteristics in the aircraft's internal separation wake area are simulated, including: when performing the aircraft's strong time-varying flow field budget, a time step smaller than a preset value is used to obtain the strongly time-varying flow field; after the launch object begins the internal separation movement, a time step larger than the preset value is used to obtain the launch separation characteristics of the launch object.

[0014] Furthermore, the construction of a basic parabolic delivery channel for rearward multi-body separation inside an aircraft includes:

[0015] Based on the minimum backward ejection velocity V of the projectile min , Maximum ejection speed V max , gravitational acceleration g and separation time t, calculate the minimum parabolic curve trajectory S min (x min , z min ) and the maximum parabola trajectory S max (x max , z max ), where x min =V min t, z min =0.5gt 2 ;x max =V max t, z max =0.5gt 2 ;

[0016] According to the minimum initial separation position envelope y of the dropped object on the side of the aircraft min and the maximum initial separation position envelope y max , the lateral interval of the basic parabolic release channel is defined as [y min ,y max ];

[0017] The minimum parabola trajectory S min The starting point is set as the initial separation position that is closest to the aircraft in the axial direction and the lowest in the longitudinal direction, and the maximum parabolic trajectory S max The starting point is set as the initial separation position which is axially farthest from the aircraft and longitudinally most upward;

[0018] The minimum parabola trajectory S min and the maximum parabolic curve trajectory S max The plane of the composition is stretched laterally to y min With y max The formed spatial envelope area serves as the basic parabolic delivery channel.

[0019] Furthermore, constructing a parabolic delivery channel taking uncertainty into consideration according to the basic parabolic delivery channel includes:

[0020] The uncertainty U of the backward ejection velocity of the projectile is evaluated by using error analysis method and prior knowledge. v , angle of attack uncertainty U a , Sideslip angle uncertainty U b , aerodynamic influence deviation U f and the gust uncertainty U t ;

[0021] The envelope range of the basic parabolic delivery channel is amplified by uncertainty to obtain a parabolic delivery channel taking uncertainty into consideration. The amplification factors in each direction include:

[0022] Axial magnification: (1+U v )×(1+U f )×(1+U t );

[0023] Vertical magnification: (1+U a )×(1+U f )×(1+U t );

[0024] Lateral magnification: (1+U b )×(1+U f )×(1+U t ).

[0025] Furthermore, the generating of multi-scale gradient mixed overlapping grids includes:

[0026] Generate surface meshes of the aircraft and the dropped objects, wherein the surface meshes adopt quadrilateral structure meshes;

[0027] The space grid of the aircraft adopts a spherical far field. If the scale of the aircraft is L f , then the diameter of the far field boundary must exceed 20L f ;

[0028] The spatial grid of the projectile adopts the cylindrical far field. If the length of the projectile is L t , the radial maximum radius envelope is R t , then the length of the far-field boundary should be 1.2L t ~1.5L t , the radial radius should be 2R t ~4R t ; Grid size D at the far field boundary of the projectile t No more than 3 times the surface grid size;

[0029] When the space grid of the aircraft is generated, the space grid scale inside the parabola delivery channel is gradually changed. The gradual change rules include: the grid scale of the initial delivery area is the same as the far field scale of the delivery object. As the parabola distance increases, the grid scale gradually changes to 1.2D.t ~1.5D t ; The grid scale of the grid space outside the parabola delivery channel gradually changes to its far-field grid scale.

[0030] Furthermore, the adaptive low-speed preprocessing method is used to simulate the flow characteristics of strong shear in the separated wake area inside the aircraft, including: changing the time derivative term of the Navier-Stokes equation during the simulation calculation so that the characteristic velocity of the equation remains at the same order of magnitude in the low-speed area of ​​strong shear and the high-speed area.

[0031] Furthermore, based on the strongly time-varying flow field estimation method, the strongly time-varying flow characteristics in the separation wake area inside the aircraft are simulated, including: using fluid solving software and unsteady methods to carry out internal backward multi-body separation simulation, placing the dropped object at the initial separation position, keeping the relative position of the dropped object and the aircraft fixed at the initial stage of calculation, pre-calculating a preset unsteady number of steps, monitoring the pressure and velocity distribution of the aircraft wake field until a stable oscillation period of the monitoring point is obtained; after obtaining a stable oscillating flow field, removing the restrictions on the separation position and posture of the dropped object, and continuing to calculate the separation trajectory of the dropped object.

[0032] The beneficial effects of the present invention are:

[0033] 1. Since the objects are ejected backwards from the tail of the aircraft during internal separation, the separation time is relatively long, and the objects are in the interference of the carrier aircraft wake for a long time, which places high requirements on the quality of the grid. In view of the fact that the trajectory of the objects released during internal separation is similar to a parabola, the present invention proposes the concept of "aircraft parabolic delivery channel", and uses high-quality multi-scale gradient space grids inside the parabolic channel to improve the simulation accuracy of the separation trajectory of the objects inside the entire parabolic channel. At the same time, during the actual flight process in the sky, the separation trajectory of the objects released is also uncertain due to uncertain factors such as gusts, aircraft jitters, and unstable airflow. The present invention proposes a method for constructing an aircraft parabolic delivery channel that takes uncertainty into account, and fully considers the uncertainty of separation when generating the grid, further ensuring the simulation accuracy of the numerical simulation.

[0034] 2. Since the wake of the aircraft presents strong shear characteristics, the airflow velocity in the wake shear area is low and there is a strong separation vortex. Outside the wake shear area, there is a high-speed carrier turbulence. In addition, the wake of the aircraft is usually an unsteady airflow, and the flow field characteristics change violently over time. The overall performance is a strong time-varying feature. Conventional numerical simulation methods are difficult to meet the high-precision simulation requirements. The present invention adopts adaptive low-speed preprocessing technology to improve the simulation accuracy of the strong shear wake in view of the strong shear and strong time-varying flow characteristics in the built-in separation wake area. At the same time, a certain number of unsteady steps is pre-calculated before the movement of the drop, and a strong time-varying wake field with regular oscillation is pre-established, so that the drop begins to separate in a high-fidelity flow field. At the same time, due to the high frequency of aircraft wake oscillation, the high-fidelity wake field budget requires a smaller time step, while the delivery separation requires a larger time step. Therefore, the present invention adopts a variable time step technology to improve the accuracy and robustness of the numerical simulation. The present invention can effectively improve the prediction accuracy of the rearward multi-body separation of the aircraft, and solve the problem of low accuracy of the numerical simulation of the rearward delivery separation of the built-in. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of an internal backward multi-body separation simulation method based on a delivery channel of the present invention.

[0036] Figure 2 This is a schematic diagram of the rearward separation inside the simplified C17 aircraft.

[0037] Figure 3 It is a plane diagram of a basic parabolic channel.

[0038] Figure 4 It is a schematic diagram of the spatial structure of a basic parabolic channel.

[0039] Figure 5 This is a schematic diagram of the aircraft parabolic release channel taking uncertainty into account.

[0040] Figure 6 It is a schematic diagram of the hybrid grid on the aircraft surface.

[0041] Figure 7 This is a schematic diagram of the grid structure of the delivery object.

[0042] Figure 8 It is a schematic diagram of the parabolic channel grid of the aircraft space.

[0043] Fig. 9 It is a comparison and verification diagram of the numerical simulation results of the present invention and the experimental results. DETAILED DESCRIPTION

[0044] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. 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, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides a simulation method for internal rearward multi-body separation based on a delivery channel, comprising:

[0047] Mesh generation: Construct a basic parabolic delivery channel for rearward multi-body separation inside the aircraft, construct a parabolic delivery channel considering uncertainty based on the basic parabolic delivery channel, and generate multi-scale gradient mixed overlapping grids;

[0048] Strong shear and strong time-varying flow simulation: According to the multi-scale gradient mixed overlapping grid, the strong shear flow characteristics in the separation wake area of ​​the aircraft are simulated based on the adaptive low-speed preprocessing method, and the strong time-varying flow characteristics in the separation wake area of ​​the aircraft are simulated based on the strong time-varying flow field budget method and the variable time step method; the strong shear flow characteristics include the flow characteristics with shear characteristics higher than the first threshold, and the strong time-varying flow characteristics include the flow characteristics with flow field characteristics changing with time higher than the second threshold.

[0049] Specifically, the internal rearward multi-body separation simulation method of this embodiment can be implemented based on the following contents.

[0050] 1. Mesh Generation

[0051] (1) Constructing a basic parabolic delivery channel for rearward multi-body separation inside an aircraft. Preferably, according to the initial separation positions of the delivery objects in the axial, lateral and longitudinal directions, the basic parabolic delivery channel for rearward multi-body separation inside an aircraft is constructed based on the rearward ejection velocity, the parabolic formula and the lateral envelope.

[0052] More preferably, the following steps can be used to implement the method:

[0053] ① Based on the minimum backward ejection velocity V of the projectile min , Maximum ejection speed V max , gravitational acceleration g and separation time t, calculate the minimum parabolic curve trajectory S min (x min , z min ) and the maximum parabola trajectory S max (x max , zmax ), where x min =V min t, z min =0.5gt 2 ;x max =V max t, z max =0.5gt 2 ;

[0054] ②According to the minimum initial separation position envelope y of the dropped object on the side of the aircraft min and the maximum initial separation position envelope y max , the lateral interval of the basic parabolic release channel is defined as [y min ,y max ];

[0055] ③The minimum parabola trajectory S min The starting point is set as the initial separation position that is closest to the aircraft in the axial direction and the lowest in the longitudinal direction, and the maximum parabolic trajectory S max The starting point is set as the initial separation position which is axially farthest from the aircraft and longitudinally most upward;

[0056] ④ The minimum parabola trajectory S min and the maximum parabolic curve trajectory S max The plane of the composition is stretched laterally to y min With y max The formed spatial envelope area serves as the basic parabolic delivery channel.

[0057] (2) Constructing a parabolic delivery channel taking into account uncertainty based on the basic parabolic delivery channel. Preferably, based on the uncertainty of the axial, lateral and longitudinal separation conditions and the uncertainty of the aerodynamic conditions, the uncertainty multiple is amplified on the basis of the basic parabolic delivery channel to obtain a parabolic delivery channel taking into account uncertainty.

[0058] More preferably, the following steps can be used to implement the method:

[0059] ①Use error analysis method and prior knowledge to evaluate the uncertainty U of the backward ejection velocity of the projectile v , angle of attack uncertainty U a , Sideslip angle uncertainty U b , aerodynamic influence deviation U f , gust uncertainty U t ;

[0060] ② The uncertainty of the envelope range of the basic parabolic delivery channel is amplified to obtain the parabolic delivery channel considering uncertainty. The amplification factor in each direction is:

[0061] Axial magnification: (1+U v)×(1+U f )×(1+U t );

[0062] Vertical magnification: (1+U a )×(1+U f )×(1+U t );

[0063] Lateral magnification: (1+U b )×(1+U f )×(1+U t ).

[0064] (3) Generate multi-scale gradient mixed overlapping grids. Preferably, for the parabola delivery channel, the grid distribution is gradient-varied with the parabola distance in the channel, and the multi-scale gradient grid distribution is adopted in the whole flow field to generate the built-in backward separation mixed overlapping grid.

[0065] More preferably, the following method can be used to achieve this:

[0066] ① Generate the surface mesh of the aircraft and the dropped objects, and use as many quadrilateral structure meshes as possible;

[0067] ② The space grid of the aircraft adopts a spherical far field. If the scale of the aircraft is L f , then the diameter of the far field boundary must exceed 20L f ;

[0068] ③ The spatial grid of the object is a cylindrical far field. If the length of the object is L t , the radial maximum radius envelope is R t , then the length of the far-field boundary should be 1.2L t ~1.5L t , the radial radius should be 2R t ~4R t ; Grid size D at the far field boundary of the projectile t No more than 3 times the surface grid size;

[0069] ④ When the space grid of the aircraft is generated, the space grid scale inside the parabola delivery channel is gradual. The gradual change rules include: the grid scale of the initial delivery area is the same as the far field scale of the delivery object. As the parabola distance increases, the grid scale gradually changes to 1.2D. t ~1.5D t ; The grid scale of the grid space outside the parabola delivery channel gradually changes to its far-field grid scale.

[0070] 2. Strong shear and strong time-varying flow simulation

[0071] (1) Based on the adaptive low-speed preprocessing method, the strong shear flow characteristics in the separation wake region of the aircraft are simulated to improve the simulation accuracy of the strong shear wake, where the strong shear flow characteristics include flow characteristics with shear characteristics higher than a first threshold.

[0072] Preferably, the time derivative of the Navier-Stokes equation is changed during the simulation calculation so that the characteristic velocity of the equation remains at the same order of magnitude in the low-speed region and the high-speed region of strong shear, so as to eliminate the problem of numerical simulation rigidity and improve the simulation accuracy and robustness of the strong shear wake.

[0073] (2) Based on the strong time-varying flow field budget method and the variable time step method, the strong time-varying flow characteristics in the separation wake region inside the aircraft are simulated, where the strong time-varying flow characteristics include flow characteristics whose flow field characteristics vary with time and are higher than a second threshold.

[0074] Preferably, the strongly time-varying flow characteristics in the aircraft's internal separation wake region are simulated based on a strongly time-varying flow field budget method, including: precalculating the number of unsteady physical time steps before the internal separation movement of the dropped object to obtain a regularly oscillating strongly time-varying wake field.

[0075] More preferably, the strong time-varying flow field estimation method can be implemented by the following steps: using fluid solving software and unsteady methods to carry out internal backward multi-body separation simulation, placing the object at the initial separation position, keeping the relative position of the object and the aircraft fixed at the initial stage of calculation, pre-calculating a certain number of unsteady steps, monitoring the pressure and velocity distribution of the aircraft wake flow field until a stable oscillation period of the monitoring point is obtained. After obtaining a stable oscillating flow field, the restrictions on the separation position and posture of the object are released, and the separation trajectory of the object is continued to be calculated.

[0076] Preferably, the strongly time-varying flow characteristics in the aircraft's internal separation wake region are simulated based on a variable time step method, including: when performing a strong time-varying flow field budget for the aircraft, a time step smaller than a preset value is used to obtain the strong time-varying flow field; after the launch object begins its internal separation movement, a time step larger than a preset value is used to obtain the launch separation characteristics of the launch object.

[0077] Example 2

[0078] This embodiment is based on embodiment 1:

[0079] This embodiment provides a simulation method for internal backward multi-body separation based on a delivery channel, such as Figure 2 As shown, this embodiment carries out numerical simulation on the separation of multiple bodies ejected backwards inside the aircraft. Figure 2The aircraft is a simplified model of a C17 transport aircraft, and the object to be dropped is a simplified cone-cylindrical configuration with an active control surface at the tail. The internal rearward multi-body separation simulation method based on the drop channel of this embodiment is implemented by the following contents.

[0080] 1. Construct an internal rearward multi-body separation basic parabolic delivery channel.

[0081] ① If the minimum backward ejection speed of the projectile is V min , the maximum ejection speed is V max , the acceleration due to gravity is g, and the separation time is t, then:

[0082] Calculate the minimum parabola trajectory S min :

[0083] Axial direction: x min =V min t; vertical: z min =0.5gt 2 ;

[0084] Calculate the maximum parabola trajectory S max :

[0085] Axial direction: x max =V max t; vertical: z max =0.5gt 2 ;

[0086] like Figure 3 As shown, the minimum parabolic curve and the maximum parabolic curve are connected to form a plane diagram of the parabolic channel.

[0087] ② The minimum and maximum initial separation position envelopes of the dropped object on the side of the aircraft are y min =-1.2m,y max =1.2m, so the lateral range of the basic parabolic release channel is defined as [-1.2, 1.2].

[0088] ③The minimum parabola trajectory S min The starting point is set as the initial separation position that is closest to the aircraft in the axial direction and the lowest in the longitudinal direction, and the maximum parabolic trajectory S max The starting point is set to the initial separation position that is axially farthest from the aircraft and longitudinally most upward.

[0089] ④ The minimum parabola trajectory S min and the maximum parabolic curve trajectory S max The plane of the composition is stretched laterally to y min With y max ,like Figure 4 As shown, the formed space envelope area is defined as the basic parabolic delivery channel.

[0090] 2. Construct a parabolic delivery channel that takes uncertainty into account.

[0091] ① In this embodiment, the uncertainty U of the backward ejection velocity of the projectile is evaluated by using the error analysis method and prior knowledge. v = 8%, angle of attack uncertainty U a =5%, sideslip angle uncertainty U b =5%, aerodynamic influence deviation U f =10%, gust uncertainty U t =15%.

[0092] ② If Figure 4 As shown in the figure, the envelope range of the basic parabolic delivery channel is enlarged to obtain the parabolic delivery channel considering uncertainty. The magnification factor in each direction is:

[0093] Axial magnification: (1+U v )×(1+U f )×(1+U t )=1.08×1.10×1.15=1.366;

[0094] Vertical magnification: (1+U a )×(1+U f )×(1+U t )=1.05×1.10×1.15=1.328;

[0095] Lateral magnification: (1+U b )×(1+U f )×(1+U t )=1.05×1.10×1.15=1.328.

[0096] like Figure 5 Shown is a schematic diagram of an aircraft parabolic delivery channel taking uncertainty into account in this embodiment.

[0097] 3. Generate multi-scale gradient mixed overlapping grids.

[0098] ① Such as Figure 6 As shown, the surface mesh of the aircraft and the dropped objects is generated, and the surface mesh adopts as many quadrilateral structure meshes as possible.

[0099] ② The space grid of the aircraft adopts a spherical large far field. The length of the aircraft is 53m and the diameter of the far field boundary is 1200m.

[0100] ③ The far field of the projected object adopts a cylindrical small far field, such as Figure 7 As shown, the length of the object is L t , the radial maximum radius envelope is R t, then the length of the far-field boundary of the object in this embodiment is 1.25L t , radial radius is 3.2R t ; and the grid size D of the far field boundary of the projectile t It is 2.5 times the surface grid size.

[0101] ④ When the space grid of the aircraft is generated, the spatial grid scale inside the parabolic delivery channel is gradually changed considering the uncertainty. The gradual change rule is: the grid scale of the initial delivery area is the same as the far field scale of the delivery object. As the parabola distance increases, the grid scale gradually changes to 1.3 times D t (Grid scale of the far-field boundary of the projectile). Considering the uncertainty, the grid space scale outside the parabolic delivery channel gradually changes to its far-field grid scale. The final spatial grid distribution effect is as follows: Figure 8 As shown in the figure, the grid distribution is optimized inside and near the parabolic channel, and the grid gradient transition between the parabolic channel and the rest of the aircraft space is good.

[0102] 4. This embodiment uses NNW-FlowStar fluid simulation software to carry out numerical simulation of internal backward ejection separation. NNW-FlowStar flow field calculation software is a ground simulation software featuring multi-body separation. It can solve control equations such as flow field equations and adjoint equations, and is widely used in wide-speed domain multi-body separation, aircraft-missile separation, and numerical simulation of variant aircraft. The adaptive low-speed preprocessing function is turned on during calculation, and the time derivative term of the Navier-Stokes equation is changed during simulation calculation to keep the characteristic velocity of the equation in the low-speed area with strong wake shear at the same order of magnitude as the high-speed area, eliminating the problem of numerical simulation rigidity and improving the simulation accuracy and robustness of strong shear wake.

[0103] 5. Prediction of strong time-varying wake field for separation inside the aircraft.

[0104] ① FlowStar fluid simulation software was used to carry out the internal backward multi-body separation simulation. The dropped object was placed at the initial separation position. The relative position of the dropped object and the aircraft was kept fixed at the initial stage of the calculation. 300 unsteady physical time steps were pre-calculated to obtain the stable oscillation period of the monitoring point.

[0105] ② After 300 unsteady physical time steps, the restrictions on the separation position and posture of the projectile are lifted, and the separation trajectory of the projectile is continued to be calculated.

[0106] 6. When estimating the strong time-varying flow field of the aircraft, the time step is 0.001s to obtain a high-precision strong time-varying flow field; after the drop starts to move, the time step is 0.01s to obtain the drop separation characteristics of the drop.

[0107] Fig. 9A comparative verification of the numerical simulation results of this embodiment and the wind tunnel CTS experiment is given. The comparison results show that the simulation method is basically consistent with the wind tunnel experiment results. This method can achieve high-fidelity numerical simulation of internal rearward multi-body separation and provide high-reliability data support for separation safety assessment.

[0108] Example 3

[0109] This embodiment is based on embodiment 1:

[0110] This embodiment provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the built-in backward multi-body separation simulation method based on the delivery channel of embodiment 1 are implemented. The computer program may be in source code form, object code form, executable file, or some intermediate form.

[0111] Example 4

[0112] This embodiment is based on embodiment 1:

[0113] This embodiment provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the built-in backward multi-body separation simulation method based on the delivery channel of Embodiment 1. The computer program may be in source code form, object code form, executable file, or some intermediate form, etc. The storage medium includes: any entity or device capable of carrying computer program code, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content contained in the storage medium may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the storage medium does not include electric carrier signals and telecommunication signals.

[0114] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity of description, they are expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

Claims

1. A simulation method for rearward multi-body separation based on a delivery channel, characterized in that: include: Grid generation: construct a basic parabolic delivery channel for rearward multi-body separation inside the aircraft, construct a parabolic delivery channel considering uncertainty based on the basic parabolic delivery channel, and generate multi-scale gradient mixed overlapping grids; Strong shear and strong time-varying flow simulation: Based on the multi-scale gradient mixed overlapping grid, the strong shear flow characteristics in the separated wake area of ​​the aircraft are simulated based on the adaptive low-speed preprocessing method, and the strong time-varying flow characteristics in the separated wake area of ​​the aircraft are simulated based on the strong time-varying flow field budget method and the variable time step method; The strong shear flow characteristics include flow characteristics whose shear characteristics are higher than a first threshold value, and the strong time-varying flow characteristics include flow characteristics whose flow field characteristics change with time and are higher than a second threshold value.

2. The method for simulating the internal backward multi-body separation based on the delivery channel according to claim 1 is characterized in that: The method of constructing a basic parabolic delivery channel for rearward multi-body separation inside an aircraft comprises: constructing a basic parabolic delivery channel for rearward multi-body separation inside an aircraft based on the axial, lateral and longitudinal initial separation positions of the delivery objects, the rearward ejection speed, the parabolic formula and the lateral envelope.

3. The method for simulating the internal backward multi-body separation based on the delivery channel according to claim 1 is characterized in that: A parabolic delivery channel taking uncertainty into consideration is constructed based on the basic parabolic delivery channel, including: according to the uncertainty of axial, lateral and longitudinal separation conditions and the uncertainty of aerodynamic conditions, the uncertainty multiple is amplified on the basis of the basic parabolic delivery channel to obtain the parabolic delivery channel taking uncertainty into consideration.

4. The method for simulating the internal backward multi-body separation based on the delivery channel according to claim 1 is characterized in that: Based on the strong time-varying flow field budget method, the strong time-varying flow characteristics in the aircraft internal separation wake area are simulated, including: pre-calculating the unsteady physical time steps before the internal separation movement of the dropped object to obtain a regularly oscillating strong time-varying wake field.

5. The method for simulating the internal backward multi-body separation based on the delivery channel according to claim 1 is characterized in that: The strong time-varying flow characteristics in the internal separation wake area of ​​the aircraft are simulated based on the variable time step method, including: when performing the strong time-varying flow field budget of the aircraft, a time step smaller than a preset value is used to obtain the strong time-varying flow field; after the release begins the internal separation movement, a time step larger than the preset value is used to obtain the release separation characteristics of the release.

6. The method for simulating rearward multi-body separation based on a delivery channel according to claim 1, characterized in that: The method of constructing a basic parabolic delivery channel for rearward multi-body separation inside an aircraft comprises: Based on the minimum backward ejection velocity V of the projectile min , Maximum ejection speed V max , gravitational acceleration g and separation time t, calculate the minimum parabolic curve trajectory S min (x min , z min ) and the maximum parabola trajectory S max (x max , z max ), where x min =V min t, z min =0.5gt 2 ;x max =V max t, z max =0.5gt 2 ; According to the minimum initial separation position envelope y of the dropped object on the side of the aircraft min and the maximum initial separation position envelope y max , the lateral interval of the basic parabolic release channel is defined as [y min ,y max ]; The minimum parabola trajectory S min The starting point is set as the initial separation position that is closest to the aircraft in the axial direction and the lowest in the longitudinal direction, and the maximum parabolic trajectory S max The starting point is set as the initial separation position which is axially farthest from the aircraft and longitudinally most upward; The minimum parabola trajectory S min and the maximum parabolic curve trajectory S max The plane of the composition is stretched laterally to y min With y max The formed spatial envelope area serves as the basic parabolic delivery channel.

7. The method for simulating the internal backward multi-body separation based on the delivery channel according to claim 1 is characterized in that: A parabolic delivery channel considering uncertainty is constructed according to the basic parabolic delivery channel, including: The uncertainty U of the backward ejection velocity of the projectile is evaluated by using error analysis method and prior knowledge. v , angle of attack uncertainty U a , Sideslip angle uncertainty U b , Aerodynamic influence deviation U f and the gust uncertainty U t ; The envelope range of the basic parabolic delivery channel is amplified by uncertainty to obtain a parabolic delivery channel taking uncertainty into consideration. The amplification factors in each direction include: Axial magnification: (1+U v )×(1+U f )×(1+U t ); Vertical magnification: (1+U a )×(1+U f )×(1+U t ); Lateral magnification: (1+U b )×(1+U f )×(1+U t ).

8. The method for simulating rearward multi-body separation based on a delivery channel according to claim 1, characterized in that: The generating of multi-scale gradient mixed overlapping grids comprises: Generate surface meshes of the aircraft and the dropped objects, wherein the surface meshes adopt quadrilateral structure meshes; The space grid of the aircraft adopts a spherical far field. If the scale of the aircraft is L f , then the diameter of the far field boundary must exceed 20L f ; The spatial grid of the projectile adopts the cylindrical far field. If the length of the projectile is L t , the radial maximum radius envelope is R t , then the length of the far-field boundary should be 1.2L t ~1.5L t , the radial radius should be 2R t ~4R t ; Grid size D at the far field boundary of the projectile t No more than 3 times the surface grid size; When the space grid of the aircraft is generated, the space grid scale inside the parabola delivery channel is gradually changed. The gradual change rules include: the grid scale of the initial delivery area is the same as the far field scale of the delivery object. As the parabola distance increases, the grid scale gradually changes to 1.2D. t ~1.5D t ; The grid scale of the grid space outside the parabola delivery channel gradually changes to its far-field grid scale.

9. The method for simulating the internal backward multi-body separation based on the delivery channel according to claim 1, characterized in that: The method of simulating the strong shear flow characteristics in the separated wake region inside the aircraft based on the adaptive low-speed preprocessing method includes: changing the time derivative term of the Navier-Stokes equation during the simulation calculation so that the characteristic speed of the equation remains at the same order of magnitude in the low-speed region of strong shear and the high-speed region.

10. The method for simulating the internal backward multi-body separation based on the delivery channel according to claim 1, characterized in that: Based on the strong time-varying flow field budget method, the strong time-varying flow characteristics in the separation wake area inside the aircraft are simulated, including: using fluid solving software and unsteady methods to carry out internal backward multi-body separation simulation, placing the release object at the initial separation position, keeping the relative position of the release object and the aircraft fixed at the initial stage of calculation, pre-calculating a preset unsteady step number, monitoring the pressure and velocity distribution of the aircraft wake field until a stable oscillation period of the monitoring point is obtained; after obtaining a stable oscillating flow field, removing the restrictions on the separation position and posture of the release object, and continuing to calculate the separation trajectory of the release object.

Images