Anti-turbulent-flow unshelling and armor-piercing projectile support clamping petal aerodynamic configuration design method

Abstract

The invention provides an anti-turbulent-flow unshelling and armor-piercing projectile support clamping flap aerodynamic configuration design method which comprises the steps that a helicopter platform composite flow field model is constructed, and the speed of a single clamping flap relative to helicopter composite airflow is obtained; simulating and calculating the in-air motion trail of the clamping flap of the shelling and armor-piercing bullet in the helicopter composite flow field; the lift coefficient, the resistance coefficient and the overturning torque coefficient of the clamping flap at different attack angles and speeds are substituted into the air movement track of the clamping flap of the shelling and armor-piercing bullet in the helicopter composite flow field, simulation calculation of the clamping flap trajectory is carried out, and then Monte Carlo simulation is carried out to generate a plurality of different clamping flap movement tracks; setting an objective function meeting a safe distance and carrying out iteration to obtain an optimal aerodynamic coefficient combination; the purpose of optimizing the aerodynamic characteristics of the clamping valve is achieved by modifying the geometric shape parameters of the clamping valve model and adjusting the aerodynamic coefficients of the clamping valve at different attack angles and speeds. The safety problem that the clamping petals collide with the platform due to the influence of complex turbulent flow can be solved.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of ammunition design and aviation weapon safety technology, and specifically relates to an aerodynamic shape design method for the dislodged flap of a discarding sabot armor-piercing projectile used on high-speed flight platforms (especially helicopters). Background Technology

[0002] On land platforms or naval warships, traditional sabot armor-piercing projectiles employ axisymmetric or simple geometric shapes, relying on radial separation to meet safety requirements. However, helicopter platforms face a drastically different and extreme environment: helicopters fly at speeds of hundreds of kilometers per hour, superimposed with the intense downwash generated by the main rotor, creating a highly complex and unsteady composite aerodynamic field. In this environment, traditional designs reveal fatal flaws: firstly, the symmetrical shape leads to a mismatch between the aerodynamic center and the center of mass, causing the sabot to tumble irregularly in the strong shear flow, resulting in a completely unpredictable trajectory; secondly, the randomly moving sabot is highly susceptible to being entrained in the rotor flow field, impacting critical components such as the main rotor and tail rotor, potentially triggering catastrophic accidents.

[0003] Existing solutions, such as separation boosters, can provide initial separation velocity but cannot resist subsequent continuous turbulence, increasing system complexity and cost. Currently, there is a lack of flap designs specifically designed for systematic aerodynamic optimization of helicopter complex flow fields. Therefore, there is an urgent need for a novel flap design capable of actively utilizing ambient airflow to achieve a stable and controllable self-avoidance trajectory, fundamentally ensuring the operational safety of helicopters. Summary of the Invention

[0004] The purpose of this invention is to provide an aerodynamic shape design method for the toggle flap of an armor-piercing discarding sabot projectile that is resistant to turbulence, in order to solve the safety problem of the toggle flap impacting the platform when the armor-piercing discarding sabot projectile is launched on a high-speed helicopter platform.

[0005] The technical solution to achieve the purpose of this invention is as follows:

[0006] A method for designing the aerodynamic shape of the Toka valve of a discarding sabot armor-piercing projectile with anti-turbulence capabilities, comprising:

[0007] A composite flow field model of the helicopter platform was constructed to obtain the velocity of a single lobe relative to the composite airflow of the helicopter.

[0008] Simulation calculation of the aerial trajectory of the sabot fragments of an armor-piercing discarding sabot projectile under a complex flow field in a helicopter;

[0009] By incorporating the lift coefficient, drag coefficient, and rollover moment coefficient of the lobe under different angles of attack and velocities into the aerial trajectory of the lobe of a discarding sabot armor-piercing projectile in a helicopter's composite flow field, the trajectory of the lobe is simulated and calculated. Subsequently, Monte Carlo simulation is performed to generate multiple different lobe trajectories. An objective function that satisfies the safety distance is set and iterated to obtain the optimal combination of aerodynamic coefficients.

[0010] By modifying the geometric parameters of the cardioid model, the aerodynamic coefficients of the cardioid at different angles of attack and velocities can be adjusted to optimize its aerodynamic characteristics.

[0011] The significant advantages of this invention compared to existing technologies are:

[0012] (1) Based on the simulation results, on the one hand, the aerodynamic shape of the card lobe can be optimized to enhance its anti-interference capability, and on the other hand, it can provide pilots with a clear safe launch envelope to guide them to launch weapons in a safe flight attitude and speed. It has strong guiding design significance and operational use impact.

[0013] (2) It is computationally efficient and easy to be engineered, avoiding the huge computational overhead of establishing and solving complex three-dimensional unsteady CFD flow field models. This allows the scheme to run quickly on conventional computing devices and can even be integrated into the fire control system of helicopters for real-time or near-real-time safety assessment.

[0014] (3) As a new type of combat environment, this scheme can make the most of existing mature and verified undisturbed ballistic calculation programs, reducing development difficulty, cost and risk, and has strong compatibility. Attached Figure Description

[0015] Figure 1 This diagram illustrates the steps involved in the aerodynamic design of the anti-helicopter platform spoiler flap of the discarding sabot armor-piercing projectile according to the present invention.

[0016] Figure 2 A three-dimensional flight trajectory diagram of an armor-piercing discarding sabot projectile in a flow field around a helicopter platform.

[0017] Figure 3 The xy curve of an armor-piercing discarding sabot projectile flying under the turbulent airflow field of a helicopter platform.

[0018] Figure 4 The curve shows the velocity of an armor-piercing discarding sabot projectile versus time under the turbulent airflow field of a helicopter platform.

[0019] Figure 5 This is a schematic diagram of the flap model of an armor-piercing discarding sabot projectile.

[0020] Figure 6 This is a schematic diagram of the network model. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] The core of this invention lies in introducing a helicopter turbulence field into existing ballistic calculations through programmed methods, and designing an aerodynamic shape for the sabot with adaptive deflection capability based on this. The following will describe this in detail according to the logical order of technical implementation. A method for designing the aerodynamic shape of the sabot for an armor-piercing discarding sabot projectile with anti-turbulence features, comprising the following steps:

[0023] Step 1: Analyze the aerodynamic environment of the helicopter platform and construct a composite flow field model of the helicopter platform.

[0024] First, a simplified helicopter downwash flow model is established. The intense and complex three-dimensional unsteady downwash flow field generated by the helicopter's main rotor is approximated as a uniform, stable, and vertically downward airflow within the helicopter's spatial range. Taking an attack helicopter as a typical application platform, its key parameters include: rotor diameter D (a critical geometric dimension determining the range of influence of the downwash flow field); typical combat weight W (used to calculate the thrust generated by the rotor to provide lift); and typical forward velocity. It constitutes the main component of the environmental flow, and its direction is forward along the longitudinal axis of the helicopter.

[0025] Based on rotor momentum theory, the complex rotor vortex field is simplified into a uniform, stable, vertically downward airflow below the rotor disk. (Downwash velocity) The calculation formula is:

[0026]

[0027] Where T is the rotor thrust, its value is approximately... Rotor thrust is the upward force generated by the rotor to balance the weight of the helicopter. Let A be the acceleration due to gravity, and let A be the area of ​​the rotor disk, which is the circular area swept by the rotor. This refers to air density.

[0028] Next, a ballistic calculation framework under a composite velocity field is constructed, calculating the time step at each step after cardiolobe separation. Inside, consider two velocity vectors simultaneously: the velocity of the cardioid relative to the still air. and ambient airflow speed The speed of the ambient airflow is determined by the forward speed of the helicopter. With the above-mentioned washing speed Vector composition.

[0029]

[0030] in The direction is vertically downwards.

[0031] Therefore, the aerodynamic force on a single flap is not based on its velocity relative to still air, but rather on its velocity relative to the complex turbulent flow field. The velocity of a single flap relative to the combined flow field of the helicopter platform... The calculation formula is as follows:

[0032]

[0033] Step 2: Simulate and calculate the aerial trajectory of the armor-piercing discarding sabot projectile's flaps under the complex turbulence field of a helicopter.

[0034] To simulate the three-dimensional motion trajectory of the lobes after the explosion of an armor-piercing discarding sabot projectile, a multibody dynamics model was used to simulate and calculate the trajectories of the three lobes.

[0035] The cardioid motion model simulates the three-dimensional motion of the three cardioids under the influence of aerodynamics, gravity, and torque:

[0036] Lift model:

[0037]

[0038] Resistance model:

[0039]

[0040] Torque Model:

[0041]

[0042] in, The lift force on a single card lobe The resistance experienced by a single cardiopulmonary bypass valve. The overturning torque on a single cardia. air density, The velocity of a single card lobe relative to the complex flow field of the helicopter. The characteristic area of ​​a single cardioid flap is simplified here to the maximum cross-sectional area along the cardioid axis. The characteristic length of the scabbard lobe is denoted by , which is the average torque exerted by the aerodynamic force on the scabbard lobe. Here, it is defined as the maximum projected distance along the longitudinal axis of the scabbard lobe. For a single cardiolobe lift coefficient, For a single sac flap drag coefficient, This is the torque coefficient for the flipping of a single card flap.

[0043] The motion of the three lobes was obtained through ODE programming with the help of MATLAB software. The trajectory center was set as the center position of the three lobes, thus approximately determining the direction of the aerodynamic force on the lobes. This means that the motion of the projectile center is not set independently, but is calculated in real time from the positions of the three lobes.

[0044] The entire process uses the Newton-Euler equations to establish a dynamic model. The program combines the motion equations of the three lobes into a large ODE system and calculates the current position of the three lobes at each time step.

[0045]

[0046]

[0047] in, The force on a single cardiolobe, The gravitational force acting on a single cardia. The mass of a single lobe is given. The force is calculated by taking the aerodynamic coefficient of the armor-piercing discarding sabot lobe at the end of the current time step. This force is then used to simulate the force on the lobe at the next time step. The acceleration and angular acceleration of the lobe are calculated using Newton's second law. Integrating the acceleration yields the lobe's velocity and angle of attack at the end of the next time step. By interpolating the aerodynamic coefficients at certain preset velocities and angles of attack using Newton's two-dimensional method, the aerodynamic coefficient of the lobe at the end of the next time step is obtained. Simultaneously, a second integration of the acceleration yields the lobe's trajectory and attitude change. This process is repeated for each time step. The average of the three lobe coordinates at each time step is used to determine the projectile's center position. For each lobe, the direction of the lift force is determined based on the current projectile center position, pointing from the projectile center to the lobe's pressure center.

[0048] It is important to note that when calculating the magnitude of the aerodynamic force on the scabbard, the relative velocity of the scabbard with respect to the flow field should be used. However, when simulating parameters such as the angle of attack and trajectory of the card lobe, it is still necessary to use the absolute velocity of the card lobe relative to the stationary air. Perform calculations. Among them... The absolute velocity of the card lobe at each time step can be obtained by integrating the acceleration of the card lobe.

[0049] Step 3: Adjust the cardiopulmonary bypass coefficient to counteract the complex flow field of the helicopter platform.

[0050] The goal of the aerodynamic design of the armor-piercing discarding sabot projectile's lobe is to enable the lobe to autonomously generate stable and controllable directional motion in the complex flow field of the helicopter during the free flight phase after separation, so that the flight trajectory of the armor-piercing discarding sabot projectile is predictable and safe to avoid. Now, a set of aerodynamic force and aerodynamic moment coefficients is needed so that the corresponding aerodynamic force coefficients can be obtained by Newton interpolation at any angle of attack and velocity of the lobe.

[0051] Theoretical basis and design rationale:

[0052] In the principle of aerodynamic torque generation, the core formula is the overturning torque. Calculation:

[0053]

[0054] in The dimensionless aerodynamic overturning moment coefficient is a core indicator for measuring the ability of the flap shape to generate directional deflection. Its sign determines the deflection direction, and its magnitude determines the deflection intensity. The aerodynamic moment coefficient must be adjusted to ensure that, under typical conditions... Within the range, A yaw moment greater than 0 generates a yaw moment far from the fuselage, and its absolute value is large enough to achieve rapid evasive maneuvering. This is necessary to overcome the initial disturbance during flap separation while maintaining typical flight conditions. >0, and its absolute value satisfies:

[0055]

[0056] in, The minimum overturning torque required for a single card lobe to overcome its initial angular momentum. This represents the maximum possible velocity of the lobe relative to the turbulent field during the entire motion. All preset values ​​must be guaranteed. The value satisfies this absolute value range.

[0057] Simultaneously, the lift coefficient, drag coefficient, and rollover moment coefficient of the flap are preset at specific angles of attack and velocities. , , The complex aerodynamic characteristics of the cardioid are considered as three core dimensionless coefficients, forming an optimization vector C:

[0058]

[0059] One thing to note is that , , All three are matrices, representing the drag coefficient, lift coefficient, and overturning moment coefficient of the card flap under different angles of attack and velocities.

[0060] Within a reasonable physical range, randomly generate N sets of initial aerodynamic coefficient combinations. , ... ... This forms the initial population.

[0061] For each set of coefficients in the population ,Will As input, the spool trajectory calculation is performed using the simplified helicopter turbulence field model obtained in step two. Subsequently, Monte Carlo simulations are conducted, with M simulations performed (each simulation randomly changing the initial velocity and initial elevation angle of the discarding sabot armor-piercing projectile, among other initial separation conditions). The optimization parameters are randomly changed in each simulation. This generates M different card-valve motion trajectories.

[0062] Calculate the objective function:

[0063]

[0064] in, In the first In the Monte Carlo simulation, the trajectory of the card lobe is calculated by combining the input of the optimization vector C in step two, the coordinates of the card lobe are extracted, and the minimum distance between the card lobe and the helicopter platform is obtained. The safety distance threshold is preset based on the actual situation of the project. The smaller the value, the safer the spool trajectory corresponding to that set of aerodynamic coefficients.

[0065] Finally, the objective functions are compared, and the optimal combination of aerodynamic coefficients is selected when the objective function is minimized.

[0066] The above calculation and selection process is repeated for each card segment to obtain the optimal aerodynamic coefficient of the card segment.

[0067] Step 4: Design of the optimal aerodynamic coefficient shape for the cardioid.

[0068] Simulations were performed using Fluent software. The basic model of the discarding sabot armor-piercing projectile employed a density-based coupled solution approach, while the turbulence model used a k-ε-Realizable model. For the discrete scheme, the time term adopted an implicit backward difference scheme, the spatial term used the finite volume method, and the convection term used the Roe-FDS scheme.

[0069] To simplify mesh generation and calculations, the threaded portion between the projectile and sabot is omitted. A coordinate system is established at the projectile's head. The projectile and sabot models, constructed using 3D software, are as follows: Figure 5 As shown.

[0070] First, surface meshes were created for the projectile body and sabot. Then, after modeling the air domain, volume meshes were created between the air domain and the projectile body and sabot. Due to the special nature of dynamic meshing technology, an unstructured hybrid mesh was used for the overall meshing. Simultaneously, the mesh near the projectile was refined, resulting in a total of approximately 1.45 million elements. Figure 6 As shown.

[0071] When designing the aerodynamic shape of an aircraft, optimizing its aerodynamic characteristics often only requires designing a few key shape parameters. Therefore, the camber, maximum camber position, and relative thickness of the flaps are selected as key parameters for the flap's aerodynamic shape. When these key parameters change, the flap's aerodynamic coefficients also change at different angles of attack and velocities. In this embodiment, by modifying the key geometric parameters of the flap model, its aerodynamic coefficients at different angles of attack and velocities can be systematically adjusted, thereby optimizing the flap's aerodynamic characteristics.

[0072] Cardiac flexure :

[0073]

[0074] in, It is expressed as a percentage of the maximum perpendicular distance from the mid-arc line to the chord line. It is the maximum height of the arc line in the airfoil. The arc line is the set of points equidistant from the upper and lower surfaces of the airfoil along the chord normal direction. It is the chord length of the flap, that is, the length of the chord line of the flap airfoil.

[0075] Location of maximum curvature : is the distance from the leading edge of the card flap to the point of maximum curvature, usually expressed as a percentage of chord length.

[0076] relative thickness : represents the maximum thickness t of the cardiopulmonary bypass and the chord length The ratio.

[0077] Establish the objective function, and then construct the kavallograph model corresponding to the optimal combination of aerodynamic coefficients:

[0078]

[0079] in, To determine the total number of design scenarios, the scenarios were modified by altering the different velocities and angles of attack of the cardioids during Fluent simulation. For the weighting of working conditions based on Monte Carlo statistics, , , The importance weights of each aerodynamic coefficient are given. , , In the current preset , , The cardioid is modeled under three key geometric parameters, and the aerodynamic coefficients of the cardioid are simulated using Fluent simulation results. , , This represents the target aerodynamic coefficient obtained in step three. When the objective function... The smaller the value, the more the aerodynamic characteristics of the Kavallois model match the target aerodynamic characteristics obtained in step three. Within the range conforming to physical laws, three key aerodynamic geometry design parameters of the Kavallois model are randomly generated. , , Through the calculation of the objective function, when the objective function When the value is minimized, the three key aerodynamic shape parameters of the card lobe best match the ideal value, thus selecting the optimal aerodynamic shape of the card lobe.

[0080] Obviously, the above embodiments of the present invention are merely examples to clearly illustrate the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for designing the aerodynamic shape of the Tokami flap of a discarding sabot armor-piercing projectile with anti-turbulence properties, characterized in that, include: A composite flow field model of the helicopter platform was constructed to obtain the velocity of a single lobe relative to the composite airflow of the helicopter. Simulation calculation of the aerial trajectory of the sabot fragments of an armor-piercing discarding sabot projectile under a complex flow field in a helicopter; By incorporating the lift coefficient, drag coefficient, and rollover moment coefficient of the lobe under different angles of attack and velocities into the aerial trajectory of the lobe of a discarding sabot armor-piercing projectile in a helicopter's composite flow field, the trajectory of the lobe is simulated and calculated. Subsequently, Monte Carlo simulation is performed to generate multiple different lobe trajectories. An objective function that satisfies the safe distance is set and iterated to obtain the optimal combination of aerodynamic coefficients. By modifying the geometric parameters of the cardioid model, the aerodynamic coefficients of the cardioid at different angles of attack and velocities can be adjusted to optimize its aerodynamic characteristics.

2. The method for designing the aerodynamic shape of the Tokami flap of an armor-piercing discarding sabot projectile with anti-turbulence according to claim 1, characterized in that, The complex flow field model for the helicopter platform employs a uniform and stable vertically downward airflow field model below the rotor disk, with the velocity of a single flap relative to the helicopter's complex airflow. for: ； ； ； in For ambient airflow velocity, This refers to the forward speed of the helicopter. Let T be the downwash velocity, T be the rotor thrust, and W be the helicopter's combat weight. Let A be the air density and A be the rotor disk area.

3. The method for designing the aerodynamic shape of the Tokami flap of an armor-piercing discarding sabot projectile with anti-turbulence according to claim 1, characterized in that, The trajectory of the cardioid in mid-air was simulated using a multibody dynamics model: Lift model: ； Resistance model: ； Torque Model: ； in, The lift force on a single card lobe The resistance experienced by a single cardiopulmonary bypass valve. The overturning torque on a single cardia. air density, The velocity of a single card lobe relative to the complex flow field of the helicopter. The characteristic area of ​​a single card lobe. The characteristic length of the cardiolobe. For a single cardiolobe lift coefficient, For a single sac flap drag coefficient, The flipping moment coefficient for a single card flap; The magnitude of the force is calculated by taking the aerodynamic coefficient of the lobe at the end of the current time step. This force is then used to simulate the force on the lobe at the next time step. The acceleration and angular acceleration of the lobe are calculated, and the obtained acceleration is integrated to calculate the velocity and angle of attack of the lobe at the end of the next time step. The aerodynamic coefficient of the lobe at the end of the next time step is obtained by Newton's two-dimensional interpolation of the aerodynamic coefficient at the preset velocity and angle of attack. At the same time, the trajectory and attitude change of the lobe are calculated by double integration of the obtained acceleration. The motion trajectory is calculated by iterating through the time steps.

4. The method for designing the aerodynamic shape of the Tokami flap of an armor-piercing discarding sabot projectile with anti-turbulence according to claim 3, characterized in that, The formula for calculating the force on the cardia is: ； in, The lift force on a single card lobe The resistance experienced by a single cardiopulmonary bypass valve. The gravitational force acting on a single cardiolobe.

5. The method for designing the aerodynamic shape of the Tokami flap of an armor-piercing discarding sabot projectile with anti-turbulence according to claim 1, characterized in that, Let the objective function that satisfies the safe distance be: ； in, In the first The trajectory of the card lobe obtained in the Monte Carlo simulation is used to obtain the coordinates of the card lobe and the minimum distance between it and the helicopter platform. The preset safe distance threshold; Preserve the objective function The optimal aerodynamic coefficient combination is output after iterative optimization of smaller coefficient combinations.

6. The method for designing the aerodynamic shape of the Tokami flap of an armor-piercing discarding sabot projectile with anti-turbulence according to claim 5, characterized in that, Single card flap overturning moment coefficient Its absolute value satisfies: ； in, The minimum overturning torque required for a single card lobe to overcome its initial angular momentum. The maximum velocity of the cardioid relative to the turbulent flow field. air density, The characteristic area of ​​a single card lobe. The characteristic length of the cardiolobe.

7. The method for designing the aerodynamic shape of the Tokami flap of an armor-piercing discarding sabot projectile with anti-turbulence according to claim 1, characterized in that, The geometric parameters of the scaphoid model include scaphoid curvature, location of maximum curvature, and relative thickness. The aerodynamic coefficients are adjusted by establishing an objective function for the aerodynamic coefficients at different angles of attack and velocities. ； in, The total number of design operating conditions, , , To model the card flap under the current preset card flap curvature, maximum curvature position, and relative thickness, the lift coefficient, drag coefficient, and torque coefficient were obtained through simulation using the card flap aerodynamic coefficients obtained from Fluent. , , To obtain the optimal combination of lift coefficient, drag coefficient, and torque coefficient; When the objective function When the value is minimized, the three geometric parameters of the card lobe best match the ideal value, thus selecting the optimal aerodynamic shape of the card lobe.

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