Calculation Method for Aircraft Airframe Loads and Responses under the Action of Explosion Shock Wave Gust Loads

Abstract

The present application belongs to the field of determining the load and response of an aircraft body under the action of an explosion shock wave gust load, and specifically relates to a method for calculating the load and response of an aircraft body under the action of an explosion shock wave gust load. The method takes the explosion shock wave gust velocity as input, based on the motion characteristics of the aircraft in an explosion scene, and restores the real process of the explosion shock wave advancing from the trailing edge of the aircraft tail wing to surround the aircraft, and obtains the time history of the explosion shock wave gust velocity at any position of the aircraft body. The motion of the rigid body mode of the aircraft is described by aerodynamic equations, and the motion of the elastic mode is described by structural dynamic equations. The aerodynamic coupling of the two motion forms is introduced through the assumption of an average body axis system, and the structural dynamic equations, the aerodynamic equations of the aircraft and the structural dynamic equations are solved by time advancement. The rigid-elastic coupling is considered, and the motion equations are solved jointly to obtain the real load and response history of the aircraft body.

Description

Technical Field

[0001] This application belongs to the field of determining the aircraft airframe loads and responses under the action of explosion shock wave gust loads, and particularly relates to a calculation method for aircraft airframe loads and responses under the action of explosion shock wave gust loads. Background Art

[0002] In GJB3743-99 "Requirements for Safe Use of Aircraft in Nuclear Environments", a calculation formula for the overload increment of an aircraft caused by explosion shock wave gust loads is given. This calculation formula requires few parameters and is simple to calculate, and can quickly calculate the approximate value of the overload increment of an aircraft caused by explosion shock wave gust loads. However, the calculation method of this calculation formula is relatively rough, ignoring the mechanical characteristics of the aircraft itself and the process of the gust surrounding the aircraft, and the calculation results are on the conservative side, making it difficult to be applicable to the accurate analysis of aircraft airframe loads and responses under the action of explosion shock wave gust loads.

[0003] In view of the existence of the above technical defects, this application is proposed.

[0004] It should be noted that the disclosure of the above background art content is only for assisting in understanding the inventive concept and technical solution of the present invention, and it does not necessarily belong to the prior art of this patent application. Without clear evidence indicating that the above content was publicly available on the filing date of this application, the above background art should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0005] The purpose of this application is to provide a calculation method for aircraft airframe loads and responses under the action of explosion shock wave gust loads, so as to overcome or mitigate at least one aspect of the known technical defects.

[0006] The technical solution of this application is as follows:

[0007] A calculation method for aircraft airframe loads and responses under the action of explosion shock wave gust loads, comprising:

[0008] Using the aircraft structural dynamics model, calculate the natural frequencies ω, generalized mass matrix m, and vibration modes of several orders of elastic modes of the aircraft;

[0009] Calculate the velocity of the explosion shock wave gust of the kth aerodynamic grid in the aircraft aerodynamic model at time T

[0010] Wherein,

[0011] V g,T Is the velocity of the explosion shock wave gust at the trailing edge of the aircraft tail at time T. The initial velocity of the explosion shock wave gust is V, which reaches the trailing edge of the aircraft tail at T = 0 and advances towards the aircraft nose;

[0012] K is the number of calculation steps;

[0013] h is the time accumulation;

[0014] d k is the distance between the k-th aerodynamic grid in the aircraft aerodynamic model and the trailing edge of the aircraft tail, 0 ≤ d k ≤ L, where L is the length of the aircraft;

[0015] V OXB,T is the average speed at which the explosion shock wave front advances in the direction of the aircraft nose within time T;

[0016] Calculate the increment of the angle of attack of the k-th aerodynamic grid in the aircraft aerodynamic model at time T

[0017] Among them,

[0018] w is the heaving speed of the aircraft;

[0019] V a is the level flight speed of the aircraft;

[0020] q is the pitch angular velocity at the center of gravity of the aircraft;

[0021] l k,g is the distance between the k-th aerodynamic grid in the aircraft aerodynamic model and the center of gravity of the aircraft;

[0022] v k,i is the mode shape vector of the k-th aerodynamic grid in the aircraft aerodynamic model under the i-th elastic mode shape;

[0023] v k,i ′ is the slope at the downwash control point of the k-th aerodynamic grid in the aircraft aerodynamic model under the i-th elastic mode shape;

[0024] η k,T,i is the coordinate of the i-th elastic mode of the k-th aerodynamic grid in the aircraft aerodynamic model at time T;

[0025] V k,T,Z is the vertical component of the speed of the explosion shock wave gust of the k-th aerodynamic grid in the aircraft aerodynamic model at time T;

[0026] Calculate the aerodynamic load influence coefficient matrix AIC between the aerodynamic grids in the aircraft aerodynamic model;

[0027] Calculate the vorticity γ of the k-th aerodynamic grid in the aircraft aerodynamic model at time T k,T :

[0028]

[0029] Calculate the aerodynamic force F of the k-th aerodynamic grid in the aircraft aerodynamic model at time T k,T = ρVa γ k,T ;

[0030] Wherein,

[0031] ρ is the air density;

[0032] Calculate the i-th order elastic mode coordinate η k,T,i , elastic mode velocity η k,T,i ′, and elastic mode acceleration increment η k,T,i ″ of the k-th aerodynamic grid in the aircraft aerodynamic model at time T:

[0033] η k,T,i ″ + ω i 2 η k,T,i = Q k,T / m i ;

[0034] Wherein,

[0035] ω i is the natural frequency of the i-th order elastic mode of the aircraft;

[0036] m i is the generalized mass matrix of the i-th order elastic mode of the aircraft;

[0037] Q k,T is the generalized force of the k-th aerodynamic grid in the aircraft aerodynamic model at time T, and is obtained by solving based on the aerodynamic force F k,T of the k-th aerodynamic grid in the aircraft aerodynamic model at time T through the principle of virtual work.

[0038] According to at least one embodiment of the present application, in the above method for calculating the aircraft body load and response under the action of an explosion shock gust load, the element C ij in the i-th row and j-th column of the aerodynamic load influence coefficient matrix AIC between the aerodynamic grids in the aircraft aerodynamic model is calculated by the vortex lattice method based on the x and z coordinates of the two corner points of the horseshoe vortices on the i-th aerodynamic grid and the j-th aerodynamic grid.

[0039] According to at least one embodiment of the present application, in the above method for calculating the aircraft body load and response under the action of an explosion shock gust load, η k,T,i ″ + ω i 2 η k,T,i = Q k,T / m i is solved by the Runge - Kutta method. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1It is the velocity V of the blast shock gust of the k-th aerodynamic grid in the aircraft aerodynamic model at time T provided by the embodiment of the present application. k,T Schematic diagram;

[0041] Figure 2 It is a schematic diagram of the typical blast shock gust velocity curve provided by the embodiment of the present application;

[0042] Figure 3 It is a schematic diagram of the aircraft aerodynamic model provided by the embodiment of the present application;

[0043] Figure 4 It is a schematic diagram of the first bending vibration mode and the coupling interpolation result of the aircraft wing symmetry provided by the embodiment of the present application;

[0044] Figure 5 It is a schematic diagram of the time history result of the elastic modal coordinates of the aircraft provided by the embodiment of the present application;

[0045] To better illustrate this embodiment, some components in the drawings are omitted, enlarged or reduced, which do not represent the dimensions of the actual product. In addition, the drawings are only for illustrative purposes and cannot be construed as a limitation of this patent. Detailed implementation manners

[0046] To make the technical solutions and their advantages of the present application clearer, the technical solutions of the present application will be further described clearly and completely in conjunction with the drawings. It can be understood that the specific embodiments described herein are only partial embodiments of the present application, which are only used to explain the present application and not to limit the present application. It should be noted that for the convenience of description, only the parts related to the present application are shown in the drawings, and other related parts can refer to the general design. Without conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0047] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application shall have the ordinary meanings understood by those of ordinary skill in the art to which this application pertains. The terms indicating directions such as "upper", "lower", "left", "right", "center", "vertical", "horizontal", "inner", "outer", etc. used in the description of this application are only used to indicate relative directions or positional relationships, rather than implying that the device or component must have a specific orientation, be constructed and operated in a specific orientation. When the absolute position of the object being described changes, its relative positional relationship may also change accordingly. Therefore, it should not be construed as a limitation to this application. The terms "first", "second", "third" and similar terms used in the description of this application are only for descriptive purposes to distinguish different components, and should not be construed as indicating or implying relative importance. The similar terms such as "a", "an" or "the" used in the description of this application should not be construed as an absolute limitation on the quantity, but should be understood as meaning at least one. The similar terms such as "including" or "comprising" used in the description of this application are intended to mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects.

[0048] In addition, it should be noted that, unless otherwise clearly specified and limited, the similar terms such as "installed", "connected", "joined" used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can also be the communication inside two components. Those skilled in the art can understand its specific meaning in this application according to the specific situation.

[0049] The following will Figures 1 to 5 make a further detailed description of this application in conjunction with the attached

[0050] A method for calculating the load and response of an aircraft airframe under the action of an explosive shock gust load, comprising:

[0051] Using the aircraft structural dynamics model, calculate the natural frequencies ω, generalized mass matrices m and vibration modes of several orders of elastic modes of the aircraft, specifically, it can be the third order;

[0052] Calculate the velocity of the explosive shock gust of the k-th aerodynamic grid in the aircraft aerodynamic model at time T T = Kh, as Figure 1 shown;

[0053] wherein,

[0054] V g,Tis the velocity of the blast shock gust at the trailing edge of the aircraft tail at time T. The initial velocity of the blast shock gust is V, which reaches the trailing edge of the aircraft tail at T = 0 and advances towards the aircraft nose. The typical blast shock gust velocity curve is as Figure 2 shown;

[0055] K is the number of calculation steps;

[0056] h is the time accumulation;

[0057] d k is the distance between the k-th aerodynamic grid in the aircraft aerodynamic model and the trailing edge of the aircraft tail, 0 ≤ d k ≤ L, where L is the length of the aircraft;

[0058] V OXB,T is the average velocity of the blast shock advancing towards the aircraft nose within time T;

[0059] The aircraft aerodynamic grid model is as Figure 3 shown;

[0060] The radial basis function method RBF is used to calculate the interpolation relationship between the aerodynamic grid and the modal vibration mode of the aircraft structural aerodynamic model, and the coupling difference between the aircraft structural dynamics model and the aerodynamic grid of the aircraft structural aerodynamic model. The symmetric first bending vibration mode of the aircraft wing and the coupling interpolation results are as Figure 4 shown, and calculate the increment of the angle of attack of the k-th aerodynamic grid in the aircraft aerodynamic model at time T

[0061] where

[0062] w is the heave velocity of the aircraft;

[0063] V a is the level flight velocity of the aircraft;

[0064] q is the pitch angular velocity at the center of gravity of the aircraft;

[0065] l k,g is the distance between the k-th aerodynamic grid in the aircraft aerodynamic model and the center of gravity of the aircraft;

[0066] v k,i is the modal vector of the k-th aerodynamic grid in the aircraft aerodynamic model under the i-th order elastic modal vibration mode;

[0067] v k,i ′ is the slope at the downwash control point of the k-th aerodynamic grid in the aircraft aerodynamic model under the i-th order elastic modal vibration mode;

[0068] η k,T,i is the coordinate of the k-th aerodynamic grid in the aircraft aerodynamic model in the i-th order elastic mode at time T;

[0069] V k,T,Z is the vertical component of the velocity of the blast shock gust of the k-th aerodynamic grid in the aircraft aerodynamic model at time T;

[0070] Calculate the aerodynamic load influence coefficient matrix AIC between the aerodynamic grids in the aircraft aerodynamic model;

[0071] Using the vortex lattice method, calculate the vorticity γ of the k-th aerodynamic grid in the aircraft aerodynamic model at time T k,T :

[0072]

[0073] Calculate the aerodynamic force F of the k-th aerodynamic grid in the aircraft aerodynamic model at time T k,T = ρV a γ k,T ;

[0074] where,

[0075] ρ is the air density;

[0076] Calculate the i-th order elastic mode coordinate η k,T,i , elastic mode velocity η k,T,i ′, and elastic mode acceleration increment η k,T,i ″ of the k-th aerodynamic grid in the aircraft aerodynamic model at time T:

[0077] η k,T,i ″ + ω i 2 η k,T,i = Q k,T / m i ;

[0078] where,

[0079] ω i is the natural frequency of the i-th order elastic mode of the aircraft;

[0080] m i is the generalized mass matrix of the i-th order elastic mode of the aircraft;

[0081] Q k,T is the generalized force of the k-th aerodynamic grid in the aircraft aerodynamic model at time T, which is obtained by solving through the principle of virtual work based on the aerodynamic force F k,T of the k-th aerodynamic grid in the aircraft aerodynamic model at time T;

[0082] Integrate the i-th order elastic mode coordinate η k,T,i , elastic mode velocity η k,T,i ′ , and elastic mode acceleration increment η k,T,i″, the i-th order elastic modal coordinates, elastic modal velocity, and elastic modal acceleration increment of the whole aircraft can be obtained. Repeat the above steps and end at the speed of the explosion shock wave gust at the trailing edge of the aircraft tail wing. The obtained aircraft elastic modal coordinate time history results are as follows: Figure 5 shown.

[0083] In some optional embodiments, in the above-mentioned method for calculating the load and response of the aircraft body under the action of the explosion shock wave gust load, the element C in the i-th row and j-th column of the aerodynamic load influence coefficient matrix AIC between the aerodynamic grids in the aircraft aerodynamic model is ij , based on the x and z coordinates of the two corner points of the horseshoe vortex on the i-th aerodynamic grid and the j-th aerodynamic grid, it is calculated using the vortex grid method.

[0084] In some optional embodiments, in the above-mentioned method for calculating the load and response of the aircraft body under the action of the explosion shock wave gust load, η k,T,i ″+ω i 2 η k,T,i =Q k,T / m i , and the Runge-Kutta method is used to solve it.

[0085] As for the method for calculating the load and response of an aircraft body under the action of an explosion shock wave gust load disclosed in the above-mentioned embodiment, it can be understood by those skilled in the art that, based on the motion characteristics of the aircraft in an explosion scenario, the explosion shock wave gust velocity is used as input to restore the actual process of the explosion shock wave advancing from the trailing edge of the aircraft tail wing to surround the aircraft, and the time history of the explosion shock wave gust velocity at any position of the aircraft body is obtained. The motion of the rigid body mode of the aircraft is described by aerodynamic equations, and the motion of the elastic mode is described by structural dynamic equations. The aerodynamic coupling of the two motion forms is introduced through the assumption of an average body axis system, and the structural dynamic equations, the aerodynamic equations and the structural dynamic equations of the aircraft are solved by time advancement. The rigid-elastic coupling is considered and the motion equations are solved jointly to obtain the actual load and response history of the aircraft body.

[0086] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0087] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A calculation method for aircraft airframe loads and responses under the action of explosion shock wave gust loads, characterized in that Including: Based on the aircraft structural dynamics model, calculate the natural frequencies ω, generalized mass matrices m, and vibration modes of several elastic modes of the aircraft; Calculate the velocity of the blast shock gust of the k-th aerodynamic grid in the aircraft aerodynamic model at time T Wherein, V g,T is the velocity of the blast shock gust at the trailing edge of the aircraft tail fin at time T. The initial velocity of the blast shock gust is V, which reaches the trailing edge of the aircraft tail fin at T = 0 and advances towards the aircraft nose. K is the number of calculation steps; h is the time accumulation; d k is the distance between the k-th aerodynamic grid in the aircraft aerodynamic model and the trailing edge of the aircraft tail, where 0 ≤ d k ≤ L, and L is the length of the aircraft; V OXB,T is the average velocity of the blast shock wave front advancing towards the aircraft nose direction within time T; Calculate the increment of the angle of attack of the k-th aerodynamic grid in the aircraft aerodynamic model at time T Wherein, w is the heave velocity of the aircraft; V a is the level flight speed of the aircraft; q is the pitch angular velocity at the center of gravity of the aircraft; l k,g is the distance between the k-th aerodynamic grid in the aircraft aerodynamic model and the aircraft center of gravity; v k,i is the modal vector of the k-th aerodynamic grid in the aircraft aerodynamic model under the i-th order elastic modal shape; v k,i ′ is the slope at the downwash control point of the k-th aerodynamic grid in the aircraft aerodynamic model under the i-th order elastic modal vibration mode; η k,T,i is the coordinate of the i-th elastic mode of the k-th aerodynamic grid in the aircraft aerodynamic model at time T; V k,T,Z is the vertical component of the velocity of the blast shock gust of the k-th aerodynamic grid in the aircraft aerodynamic model at time T; Calculate the aerodynamic load influence coefficient matrix AIC between the aerodynamic grids in the aircraft aerodynamic model; Calculate the vorticity γ of the k-th aerodynamic grid in the aircraft aerodynamic model at time T k,T : Calculate the aerodynamic force F of the k-th aerodynamic grid in the aircraft aerodynamic model at time T k,T = ρV a γ k,T ; Wherein, ρ is the air density; Calculate the $i$-th elastic mode coordinate $\eta$, the elastic mode velocity $\dot{\eta}$, and the increment of elastic mode acceleration $\ddot{\eta}$ of the $k$-th aerodynamic grid in the aircraft aerodynamic model at time $T$. k,T,i , elastic mode velocity $\dot{\eta}$ k,T,i ′ , increment of elastic mode acceleration $\ddot{\eta}$ k,T,i ″: η k,T,i ″ + ω i 2 η k,T,i = Q k,T / m i ; Wherein, ω i is the natural frequency of the i-th elastic mode of the aircraft; m i Generalized mass matrix of the i-th elastic mode of the aircraft; Q k,T is the generalized force of the k-th aerodynamic grid in the aircraft aerodynamic model at time T, and is obtained by solving based on the aerodynamic force F of the k-th aerodynamic grid in the aircraft aerodynamic model at time T k,T through the principle of virtual work.

2. The method for calculating the aircraft body load and response under the action of blast shock gust load according to claim 1, characterized in that, The element C in the i-th row and j-th column of the aerodynamic load influence coefficient matrix AIC between aerodynamic grids in an aircraft aerodynamic model ij , is calculated by the vortex lattice method based on the x and z coordinates of the two corner points of the horseshoe vortices on the i-th aerodynamic grid and the j-th aerodynamic grid.

3. The method for calculating the aircraft body load and response under the action of blast shock gust load according to claim 1, characterized in that, η k,T,i ″ + ω i 2 η k,T,i = Q k,T / m i , and the Runge-Kutta method is used to solve it.

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