CN112487690A - Method for simulating projectile inner trajectory motion under forced angle vibration condition based on ANSYS - Google Patents

Method for simulating projectile inner trajectory motion under forced angle vibration condition based on ANSYS Download PDF

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CN112487690A
CN112487690A CN202011476979.1A CN202011476979A CN112487690A CN 112487690 A CN112487690 A CN 112487690A CN 202011476979 A CN202011476979 A CN 202011476979A CN 112487690 A CN112487690 A CN 112487690A
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刘宗凯
唐维铨
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Nanjing University of Science and Technology
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Abstract

The invention realizes a three-dimensional simulation method for simulating the ballistic motion state and the flow field distribution condition in a projectile under the condition of forced angular vibration by using a bidirectional fluid-solid coupling technology based on an ANSYS software platform. The process of the shot moving in the bore until the shot is taken out of the bore is a process with high temperature, high pressure and multiple chemical reactions, and actual experimental measurement is difficult. The simulation of the process by using a numerical simulation technology is helpful for analyzing the movement state and flow field change of the projectile in the bore. The invention introduces a forced angle vibration equation of a gun barrel by using a bidirectional fluid-solid coupling numerical simulation method, and numerically simulates the process of projectile discharging from a static state under the condition of forced angle vibration. The simulation result obtained by the method is helpful for researching the motion state of the shot and the distribution condition of the flow field inside and outside the bore when the forced angular vibration is generated during the advancing of the artillery, and has certain significance for the research and development of self-propelled weapon equipment.

Description

Method for simulating projectile inner trajectory motion under forced angle vibration condition based on ANSYS
Technical Field
The invention relates to a bidirectional fluid-solid coupling technology, in particular to a projectile internal trajectory motion simulation method under the forced angle vibration condition based on ANSYS.
Background
The shooting ability of a self-weapon during its travel has become an important indicator for evaluating the operational performance of the self-weapon. In order to meet the actual requirements of a battlefield, the self-propelled weapon with the artillery needs to shoot the projectile in the process of high-speed travel, and certain random vibration is usually generated due to the influence of road excitation during the shooting. Random vibrations are complex motions formed by the combined action of multiple vibration modes. Wherein the forced angular vibration can have an obvious influence on the movement of the projectile, thereby causing the reduction of the shot hit precision. The intrabore motion of the projectile under the forced angular vibration condition is simulated by adopting a bidirectional fluid-solid coupling method, so that the change of the motion state of the projectile after being influenced is analyzed.
Chengxi et al (1 Chengxi, Zhang soldier. internal trajectory two-phase flow three-dimensional parallel numerical simulation [ J ]. war institute, 2019,40(04): 769-. However, the method only considers the influence of the flow field distribution on the movement of the projectile, and neglects the action between the projectile and the bore wall and the deformation condition of the solid structure. The method cannot study the influence of the projectile except flow field factors.
Sunjugao et al ([2] Sunjugao, Techun, Dinghongmin, Xujian, Guojun. application of SPH-FEM coupling method in intrabore motion of projectile [ J ] vibration and impact, 2019,38(08):166- + 172+187.) analyzed the stress condition of projectile in the inner trajectory process in the display dynamics by using SPH-FEM coupling method, and obtained the motion state of projectile. The method can be used for analyzing the friction, stress and deformation between the cannon barrel and the projectile in the vibration process, but the method has no flow field and cannot simultaneously consider the action of the flow field on the projectile.
Disclosure of Invention
The invention aims to provide a simulation method of projectile internal trajectory motion under the condition of forced angle vibration based on ANSYS, which is used for researching projectile internal trajectory motion and an outbreak state of a cannon when the cannon is launched under the condition of forced angle vibration and provides reference for actual tests and subsequent improvement and research and development work.
The technical solution for realizing the purpose of the invention is as follows: a method for simulating projectile inner trajectory movement under forced angle vibration conditions based on ANSYS comprises the following steps:
step 1, establishing a forced angular vibration control equation to obtain a forced angular vibration angular velocity expression;
step 2, establishing a three-dimensional geometric model of a gun barrel, a projectile and a flow field by adopting three-dimensional computer aided design software SOLIDWORKS, and outputting a geometric model file;
step 3, importing the established geometric model into an ANSYS Workbench software platform, dividing a solid domain and a fluid domain through Boolean operation, subdividing a flow field area into an inner flow field, a transition area and an outer flow field, and then dividing a grid in a mesh module;
step 4, establishing a bidirectional fluid-solid coupling solver on an ANSYS Workbench software platform, setting simulation conditions, and performing bidirectional fluid-solid coupling numerical simulation to obtain the motion state of the projectile and the distribution of the flow field inside and outside the bore;
and 5: and (4) obtaining a corresponding forced angular velocity change equation according to the actual road surface condition and the vehicle performance parameters, and carrying out numerical calculation by combining the steps 2-4 to obtain the required projectile motion parameters and flow field distribution results.
Further, in step 1, a forced angular vibration control equation is established to obtain a forced angular vibration angular velocity expression, and the specific method is as follows:
according to the vibration characteristic of the tracked vehicle in motion, a differential equation of the forced angular vibration of the tracked vehicle is constructed as follows:
Figure BDA0002837533470000021
in the formula IyIs the moment of inertia of the suspended portion, t is time, ω is the angular velocity of vibration, MkIs an elastic moment;
the following steps are provided:
Figure BDA0002837533470000022
Figure BDA0002837533470000023
in the formula: theta is the vibration angle, k is the stiffness coefficient, liIs the center to center of gravity level of the crawler wheelDistance, H is the value of the maximum amplitude of the synthetic disturbance moment curve divided by the rigidity coefficient, v is the horizontal speed, L is the vibration wavelength along the x axis, and T is the vibration period;
according to the three formulas, the expression of the angular velocity ω is solved as follows:
Figure BDA0002837533470000024
wherein:
Figure BDA0002837533470000025
Figure BDA0002837533470000026
further, in the step 2, a three-dimensional geometric model of a gun barrel, a projectile and a flow field is established by adopting three-dimensional computer aided design software SOLIDWORKS, and a geometric model file is output, wherein the whole projectile is streamline, and the size of a projectile band is slightly smaller than the caliber of the gun.
Further, in step 3, the established geometric model is led into an ANSYS Workbench software platform, a solid domain and a fluid domain are divided through Boolean operation, a flow field area is divided into an inner flow field, a transition area and an outer flow field, then grids are divided in a mesh module, wherein in order to adapt to the requirement of the flow grids, the inner flow field area and the transition area near the projectile and the barrel are divided into second-order tetrahedral grids, and the outer flow field area is divided into hexahedral grids.
Further, in step 4, a bidirectional fluid-solid Coupling solver is established on an ANSYS Workbench software platform, simulation conditions are set, bidirectional fluid-solid Coupling numerical simulation is performed, and the motion state and the flow field distribution inside and outside the bore of the projectile are obtained, wherein after entering the ANSYS Workbench software platform, Structural dynamics solution is performed through a Transient Structural module, fluid dynamics solution is performed through a FLUENT module, information exchange between the Transient Structural module and the FLUENT module is realized through a System Coupling module, and finally the motion state parameters of the projectile at each moment in the bore and at the time of delivery are obtained, including displacement, speed, delivery time, stress distribution, and the distribution condition of the flow field inside and outside the barrel, and the specific method is as follows:
introducing the solid domain grid into a Transient Structural calculation module, setting conditions of material parameters of the projectile and the cannon barrel, contact surfaces of the projectile and the barrel, projectile rotation speed, forced angular vibration angular speed omega of the cannon barrel, gravity magnitude and direction, fluid-solid coupling surface and the like in the Transient Structural calculation module, solving the motion state of the projectile at each moment, calculating the mass of the projectile by combining the geometric shapes of the projectile and the cannon barrel, and giving parameters such as material density, elastic modulus, Poisson ratio and the like;
in the solving process of the Transient Structural module, the basic equation for controlling the solid motion is as follows:
Figure BDA0002837533470000031
in the formula: msIs a quality matrix; csIs a damping matrix; k is a radical ofsIs a stiffness matrix; r issIs the solid displacement; tau issStress to which the solid is subjected;
after solving at each time step, storing state data of displacement, stress, deformation and the like of the projectile, and transmitting the displacement data of the projectile to the Fluent module through a System counting module to serve as a calculation condition in the Fluent module;
introducing a fluid domain grid into a FLUENT module, taking a fitted hearth pressure curve equation as an inlet pressure condition in a Transient Structural module, setting conditions such as a pressure outlet, a turbulence equation, a moving grid, a solving method and a solving time step length, solving the distribution condition of the flow field at each moment by combining shot motion data obtained from the Transient Structural module, storing the solving result, and transmitting pressure information on a contact surface corresponding to a fluid-solid Coupling surface back to the Transient Structural module through a System Coupling module, wherein the Transient Structural module starts to calculate the next time step according to the calculation result of the previous time step and feedback data in the FLUENT;
in the solving process of the Fluent module, the fluid is controlled by three conservation equations respectively:
(1) mass equation:
Figure BDA0002837533470000041
in the formula: u. ofx、uy、uzThe ratio of the velocity components is the velocity components in the x, y and z directions; t is time; ρ is the density.
(2) The momentum equation:
Figure BDA0002837533470000042
in the formula: u is a velocity vector; p is the pressure on the fluid microcell body; μ is the dynamic viscosity of the fluid; f is the volume force;
Figure BDA0002837533470000044
is a hamiltonian.
(3) Energy equation:
Figure BDA0002837533470000043
in the formula: e is the total energy of the fluid micelle, including the sum of internal energy, kinetic energy and potential energy; p is the pressure on the fluid microcell body, JjIs the diffusion flux of component j; h isjIs the enthalpy of component j; k is a radical ofeffA conductivity that is effective heat; tau iseffEffective viscous stress; shIs a heat source item.
The System Coupling module is used as a channel for data exchange, and the conditions of data exchange content, solving time and solving step number are set in the System Coupling module so as to control the common solving time and step length of the two modules;
in the process of data exchange in the System Coupling, the equivalent exchange of displacement and stress results between fluid and solid needs to be carried out under the bidirectional fluid-solid Coupling action, and the control equation is expressed as:
n·τf＝n·τs
rf＝rs
in the formula: tau isfThe fluid at the interface is stressed; r isfIs the fluid displacement at the interface; n is a unit vector.
Through the numerical simulation, the motion state parameters of the shot at each moment in the bore and during the discharge of the shot are obtained, wherein the motion state parameters comprise displacement, speed, discharge time, stress distribution and the distribution condition of the internal and external flow fields of the cannon barrel.
An ANSYS-based simulation system for intraprojectile trajectory motion under a forced angle vibration condition is used for performing simulation of intraprojectile trajectory motion under the forced angle vibration condition based on ANSYS based on any one of the methods.
A computer apparatus comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor when executing the computer program implementing any of the methods to simulate ballistic movement in a projectile under forced angular vibration conditions based on ANSYS.
A computer readable storage medium having stored thereon a computer program which when executed by a processor implements any of the methods to perform simulation of intraprojectile ballistic motion under forced angular vibration conditions based on ANSYS.
Compared with the prior art, the invention has the following remarkable advantages: 1) the barrel forced angular vibration and bidirectional fluid-solid coupling numerical simulation are combined, the movement condition and the flow field distribution of the projectile under the vibration condition are analyzed, the action of flow field change on the projectile and the deformation and friction of the projectile and the barrel are considered, and the obtained result is more accurate and close to the reality. 2) Compared with actual experimental tests in the initial research, the method has the advantages of higher efficiency, higher safety and higher cost performance.
Drawings
Fig. 1 is a diagram of a geometric model of a projectile.
Fig. 2 is a schematic diagram of a half flow field model field.
Fig. 3 is a comparison graph of measured bullet bottom pressure and simulated bullet bottom pressure.
Fig. 4 is a diagram of the initial shock velocity cloud generated by the bore when the projectile begins to move.
FIG. 5 is a velocity cloud plot of the gradual formation of a bottle-shaped shock wave over a period of time.
Fig. 6 is a velocity cloud of the projectile after it has been discharged.
Fig. 7 is a pressure cloud of the secondary shock wave formed after the projectile exits the chamber.
Fig. 8 is a diagram of muzzle displacement under the influence of forced angular vibration.
Fig. 9 is a diagram showing the change in displacement of the projectile.
Fig. 10 is a partially enlarged view of the variation in shot displacement.
Fig. 11 is a graph of the deflection velocity of the projectile perpendicular to the original direction.
Detailed description of the invention
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are intended merely to illustrate the application and are not intended to limit the application.
The projectile launching process is extremely complex, the whole process relates to a plurality of complex physical and chemical processes such as gunpowder chemical change, material projectile plastic deformation, contact collision between structures and the like, and the whole flow field when the projectile is launched is a multi-dimensional and multi-phase unsteady gas flow field containing high-speed moving projectiles and having strong chemical reactions. Aiming at the above, it is extremely difficult to establish a comprehensive and complete mathematical model, and in order to effectively simplify the calculation model, the numerical simulation model in the whole internal ballistic process makes the following basic assumptions according to the complex changes in the artillery launching process and the ballistic motion conditions in the projectile:
(1) the emission process is adiabatic and there is no heat exchange.
(2) Neglecting the influence of mutual chemical reaction among the internal components of the gunpowder gas, regarding the gas as an ideal gas medium identical to the external air, and completely obeying a gas state equation; the gunpowder gas enters the barrel through the pressure inlet, and the pressure is a function of time, so that the process of continuously generating the gunpowder gas is simulated.
(3) The complete numerical simulation process is the process from the initial movement of the projectile in the bore to the complete flying away from the bore.
(4) Simplifying the geometric model of the launch device and projectile.
(5) The vibration effect except the forced angle vibration is not considered and the barrel vibration condition is kept consistent with the vehicle as a whole.
(6) The projectile makes uniform accelerated rotation in the process of going out of the chamber.
Based on the hypothesis, the gun barrel vibration and the numerical simulation are combined, and a bidirectional fluid-solid coupling method in ANSYS is utilized to simulate the process that when a barrel generates forced angular vibration, a static projectile in the barrel is continuously accelerated under the pushing of the bottom pressure until the projectile goes out of the barrel, in the process, the solid domain generates displacement and deformation which are consistent with the actual situation according to the material property and the stress, and the flow field distribution is changed accordingly. Simulating the trajectory motion in the projectile under the forced angle vibration condition based on ANSYS, which comprises the following specific steps:
step 1: and establishing a forced angular vibration control equation to obtain a forced angular vibration angular velocity expression.
According to the vibration characteristics of the tracked vehicle when in motion, the differential equation of the forced angular vibration of the tracked vehicle can be written as:
Figure BDA0002837533470000061
in the formula IyIs the moment of inertia of the suspended portion, ω is the angular velocity of vibration, MkIs the elastic moment.
The following steps are provided:
Figure BDA0002837533470000071
Figure BDA0002837533470000072
in the formula: theta is the vibration angle, k is the stiffness coefficient, liThe horizontal distance from the center of the crawler wheel to the center of gravity is shown, H is a value obtained by dividing the maximum amplitude of the synthetic disturbance moment curve by the rigidity coefficient, v is a horizontal speed, L is a vibration wavelength along an x axis, T is time, and T is a vibration period.
From the above three equations, the expression for the angular velocity ω can be solved as:
Figure BDA0002837533470000073
wherein:
Figure BDA0002837533470000074
Figure BDA0002837533470000075
and 2, establishing a three-dimensional geometric model of the gun barrel, the projectile and the flow field by adopting three-dimensional computer aided design software SOLIDWORKS, and outputting a geometric model file. The whole projectile is streamline, and the size of the projectile band is slightly smaller than the caliber of the artillery. The gun barrel can also be simplified to a certain extent.
And 3, importing the geometric model established in the step 1 into an ANSYS Workbench software platform, firstly segmenting a solid domain (projectile, gun barrel) and a fluid domain (flow field) through Boolean operation, subdividing the flow field area into an inner flow field, a transition area and an outer flow field, and then dividing a mesh in a mesh module. In order to meet the requirement of the moving mesh, the inner flow field area and the transition area near the projectile and the barrel are divided into second-order tetrahedral meshes, and the outer flow field area is divided into hexahedral meshes.
And 4, establishing a bidirectional fluid-solid coupling solver on an ANSYS Workbench software platform, setting simulation conditions, starting bidirectional fluid-solid coupling numerical simulation, and storing simulation results.
Entering an ANSYS Workbench software platform, performing Structural dynamics solution through a Transient Structural module, performing fluid dynamics solution through a FLUENT module, and realizing information exchange between the Transient Structural module and the FLUENT module through a System Coupling module to finally obtain motion state parameters of the projectile at each moment in the chamber and during delivery, wherein the motion state parameters comprise displacement, speed, delivery time, stress distribution and distribution conditions of an inner flow field and an outer flow field of the projectile tube.
And (3) introducing the solid domain (projectile and barrel) grids in the step 3 into a Transient Structural calculation module, and introducing the fluid domain grids into a FLUENT calculation module.
In a Transient Structural module, the conditions of material parameters of the projectile and the cannon barrel, the contact surface of the projectile and the barrel, the rotating speed of the projectile, the forced angular vibration angular speed omega of the cannon barrel, the gravity magnitude and direction, a fluid-solid coupling surface and the like are set, the motion state of the projectile at each moment is solved, calculation is carried out, the mass of the projectile is calculated by combining the geometric shapes of the projectile and the cannon barrel, and parameters such as material density, elastic modulus, Poisson's ratio and the like are given.
In the solving process of the Transient Structural module, the basic equation for controlling the solid motion is as follows:
Figure BDA0002837533470000081
in the formula: msIs a quality matrix; csIs a damping matrix; k is a radical ofsIs a stiffness matrix; r issIs the solid displacement; tau issIs the stress to which the solid is subjected.
And after the solution of each time step is completed, storing the displacement, stress, deformation and other state data of the projectile, and transmitting the obtained displacement data of the projectile to the Fluent module through the System counting module to serve as the calculation condition in the Fluent module.
Introducing a fluid domain (inner flow field, transition region and outer flow field) grid into a FLUENT module, taking a fitted hearth pressure curve equation as an inlet pressure condition, setting conditions such as a pressure outlet, a turbulence equation, a moving grid, a solving method, a solving time step and the like, solving the distribution condition of the flow field at each moment by combining shot motion data obtained from a Transent Structural module, storing a solving result, transmitting pressure information on a contact surface corresponding to a fluid-solid Coupling surface back to the Transent Structural module through a System Coupling module, and starting to calculate the next time step by the Transent Structural module according to the calculation result of the previous time step and feedback data in the FLUENT.
In the solving process of the Fluent module, the fluid is controlled by three conservation equations respectively:
(1) mass equation:
Figure BDA0002837533470000082
in the formula: u. ofx、uy、uzThe ratio of the velocity components is the velocity components in the x, y and z directions; t is time; ρ is the density.
(2) The momentum equation:
Figure BDA0002837533470000083
in the formula: u is a velocity vector; p is the pressure on the fluid microcell body; μ is the dynamic viscosity of the fluid; f is the volume force;
Figure BDA0002837533470000084
is a hamiltonian.
(3) Energy equation:
Figure BDA0002837533470000091
in the formula: e is the total energy of the fluid micelle, including the sum of internal energy, kinetic energy and potential energy; p is the pressure on the fluid microcell body, JjIs the diffusion flux of component j; h isjIs the enthalpy of component j; k is a radical ofeffA conductivity that is effective heat; tau iseffEffective viscous stress; shIs a heat source item.
The System Coupling module is used as a data exchange channel, conditions such as data exchange content, solving time, solving step number and the like need to be set, and the module can control the common solving time and step length of the two modules.
In the process of data exchange in System Coupling, the equivalent exchange of displacement and stress results between fluid and solid is required for bidirectional fluid-solid Coupling, and the control equation can be expressed as:
n·τf＝n·τs
rf＝rs
in the formula: tau isfThe fluid at the interface is stressed; r isfIs the fluid displacement at the interface; n is a unit vector.
Through the numerical simulation, on one hand, the motion state parameters of the shot at each moment in the bore and during the discharge of the shot, including displacement, speed, discharge time, stress distribution and the like, are obtained. And on the other hand, the distribution condition of the inner and outer flow fields of the gun tube is obtained.
And 5: and analyzing the motion state of the projectile and the distribution of the flow field inside and outside the bore according to the simulation result, and verifying the reasonability of the numerical simulation result.
Step 6: and obtaining a corresponding forced angular velocity change equation according to the actual road surface condition and the vehicle performance parameters, and performing numerical calculation through the steps to obtain the required projectile motion parameters and flow field distribution results.
The invention also provides a simulation system of the trajectory movement in the projectile under the forced angle vibration condition based on ANSYS, and the simulation of the trajectory movement in the projectile under the forced angle vibration condition based on ANSYS is carried out based on any one of the methods.
A computer apparatus comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor when executing the computer program implementing any of the methods to simulate ballistic movement in a projectile under forced angular vibration conditions based on ANSYS.
A computer readable storage medium having stored thereon a computer program which when executed by a processor implements any of the methods to perform simulation of intraprojectile ballistic motion under forced angular vibration conditions based on ANSYS.
Examples
To verify the validity of the scheme of the present invention, the following simulation experiment was performed.
The method is based on the method, the situation that the projectile is shot after the forced angle vibration starts for 0.1s is simulated, and the specific steps are as follows:
firstly, the equation of the change of the forced angular vibration angular velocity ω with the time t obtained from the parameters is:
ω＝54.0535[cos15.56(t+0.1)-cos15.71(t+0.1)]
and then, establishing a three-dimensional geometric model of the gun barrel, the projectile and the flow field. And considering the symmetry of the flow field, a bilateral symmetry model is adopted to save computing resources. The geometric model used in the invention is shown in figures 1 and 2, a 75mm caliber gun barrel is adopted, the length is 1.4m, and the actual movement distance of the projectile is 1.3 m. The size of the missile belt is slightly smaller than the caliber of the artillery. The external flow field is a hexahedron of 4 m.
Then, the geometric model is led into an ANSYS Workbench software platform, the projectile, the gun barrel and the flow field are divided through Boolean operation, and the flow field area is subdivided into an inner flow field, a transition area and an outer flow field. And dividing the shot and gun barrel grids by adopting a second-order tetrahedron unit, and refining the grids at the shot belt and the bullet head. The total number of the shots and the gun barrel grids is 150353, the number of the nodes is 237969, and the minimum quality is 0.44. In the fluid area, considering the existence of the dynamic grids, a second-order tetrahedral grid is used in the inner flow field area and the transition area, and a hexahedral grid is used in the outer flow field area. The total number of fluid region grids is 2301526, the number of nodes is 4227092, and the minimum grid mass is 0.4.
After the grid division is completed, a Transmission Structural calculation module, a FLUENT calculation module and a System Coupling joint solving module in an ANSYS Workbench software platform are connected. And introducing the shot and the gun barrel grids into a Transient Structural calculation module, and introducing the fluid domain grids into a FLUENT calculation module.
In the Transmission Structure Module, the Material parameter, Pair are setThe conditions of a weighing surface, a contact surface between the projectile and the barrel, the rotating speed of the projectile, a vibration equation of a cannon forced angle, a gravity direction, a fluid-solid coupling surface and the like. The method specifically comprises the following steps: the material of the bullet and the gun barrel is alloy steel, and the quality of the bullet is given again according to the size reduction proportion. The final complete pellet mass was 4 kg. The projectile rotates with uniform acceleration of 400000rad/s2. The projectile is constrained by the inner wall of the gun barrel, and the friction factor between the projectile and the gun barrel is 0.05. In an initial state, the projectile is at a position 100mm away from the bottom of the gun barrel, the gun barrel is horizontally placed, the whole model is under the action of gravity, and the gravity direction is vertical to the horizontal direction.
And setting conditions such as turbulence equations, boundary conditions, moving grid motion surfaces and parameters, solving methods, solving time step lengths and the like in the FLUENT module. The method specifically comprises the following steps: and selecting a SIMPLE solver, wherein the solving time step length is 1e-6s, and the discrete formats are second-order precision. The chamber bottom is arranged as a pressure inlet, and an equation is fitted according to a chamber bottom pressure curve in a document. The fitted polynomial distorts the pressure curve before time reaches 0.3ms, so this curve is not considered. The pressure fit equation finally used is as follows:
Figure BDA0002837533470000111
in the formula: pdIs the pressure of the chamber bottom; t is the solution time in units of ms and 0<t<0.8ms。
The degree of fit R2 of the fitting polynomial equation was 0.9973.
And writing the UDF of pressure change of the pressure inlet according to a fitting equation, and introducing Fluent as an input value of the pressure inlet. The UDF is specifically as follows:
DEFINE_PROFILE(pressure_profile,thread,position)
{
face_t f；
begin_f_loop(f,thread)
{
real t＝RP_Get_Real("flow-time")+0.0003；
F_PROFILE(f,thread,position)＝1e6*(t*t*t*t*t*1e15*(-0.3329)+t*t*t*t*1e12*
7.8824-t*t*t*1e9*65.463+t*t*1e6*209.33-t*1e3*156.58+85.628)；
}
end_f_loop(f,thread)
}
except for the pressure inlet, the outer surfaces of other areas of the flow field model are pressure outlets, the initial static pressure is 101325Pa, and the initial temperature is 300K. The turbulence equation uses an realizable k-epsilon model. And setting dynamic grid parameters on the flow field interface between the projectile and the barrel. The flexible gridding Method in Fluent is a Method of mixing an elastic Smoothing Method (Spring Smoothing) with a gridding reconstruction Method (Remeshing Method). The elastic fairing method can properly adjust the shape of the grid according to the change of a coupling interface and the initial condition when a solid domain moves, and when the change exceeds the set limit, the local re-planning method can re-reconstruct the grid in the area at the grid with larger distortion, and simultaneously remove the grid with larger distortion degree.
The curve of the variation of the pressure of the bullet bottom without forced angular vibration and the curve experimentally measured in the literature are shown in fig. 3. As can be seen from the figure, the bullet bottom pressure in the simulation is slightly earlier than the actual bullet bottom pressure in rising time, but the maximum pressure values are all about 250MPa, the deviation value is less than 1%, and the rising speed and the falling speed are very close. The bottom stress of the projectile in the simulation can be considered to be in accordance with the actual situation.
The flow field distribution result obtained by simulation also conforms to the actual situation. As shown in fig. 4, 5, 6 and 7, the gas flow escaping before the projectile exits the chamber forms a shock wave at the nozzle and gradually develops into a bottle-shaped shock wave. After the shot is taken out of the chamber, a large amount of high-density gas is rushed out to form secondary shock waves.
When there is an influence of forced angular vibration, the barrel is deflected in a certain direction as shown in fig. 8, resulting in a more complex interaction of the projectile with the bore wall. As shown in fig. 9, 10 and 11, the discharging speed and the discharging time of the shot are changed, and the change trend is consistent with the actual situation. The time and velocity at which the final projectile completely exited the muzzle are shown in the table below:
TABLE 1 time and speed of projectile discharge
Angular vibration Time (ms) Speed (m/s) Displacement of the projectile when it comes out of the chamber (m)
0 4.804 683.09 1.3
ω 4.815 679.83 1.3
2ω 4.981 671.95 1.3
The simulation result is consistent with the actual situation, and the numerical simulation method is proved to be reasonable.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (8)

1. A method for simulating projectile internal trajectory motion under the condition of forced angular vibration based on ANSYS is characterized by comprising the following steps:
step 1, establishing a forced angular vibration control equation to obtain a forced angular vibration angular velocity expression;
step 2, establishing a three-dimensional geometric model of a gun barrel, a projectile and a flow field by adopting three-dimensional computer aided design software SOLIDWORKS, and outputting a geometric model file;
step 3, importing the established geometric model into an ANSYS Workbench software platform, dividing a solid domain and a fluid domain through Boolean operation, subdividing a flow field area into an inner flow field, a transition area and an outer flow field, and then dividing a grid in a mesh module;
step 4, establishing a bidirectional fluid-solid coupling solver on an ANSYS Workbench software platform, setting simulation conditions, and performing bidirectional fluid-solid coupling numerical simulation to obtain the motion state of the projectile and the distribution of the flow field inside and outside the bore;
and 5: and (4) obtaining a corresponding forced angular velocity change equation according to the actual road surface condition and the vehicle performance parameters, and carrying out numerical calculation by combining the steps 2-4 to obtain the required projectile motion parameters and flow field distribution results.
2. The simulation method of ballistic motion in a projectile under the forced angular vibration condition based on ANSYS according to claim 1, wherein in step 1, a forced angular vibration control equation is established to obtain a forced angular vibration angular velocity expression, and the specific method is as follows:
according to the vibration characteristic of the tracked vehicle in motion, a differential equation of the forced angular vibration of the tracked vehicle is constructed as follows:
Figure FDA0002837533460000011
in the formula: i isyIs the moment of inertia of the suspended portion, t is time, ω is the angular velocity of vibration, MkIs an elastic moment; the following steps are provided:
Figure FDA0002837533460000012
Figure FDA0002837533460000013
in the formula: theta is the vibration angle, k is the stiffness coefficient, liThe horizontal distance from the center of the crawler wheel to the gravity center is H, the value of the maximum amplitude of the synthetic disturbance moment curve divided by the rigidity coefficient is V, the horizontal speed is V, the vibration wavelength along the x axis is L, and the vibration period is T;
according to the three formulas, the expression of the angular velocity ω is solved as follows:
Figure FDA0002837533460000014
wherein:
Figure FDA0002837533460000021
Figure FDA0002837533460000022
3. the method for simulating ballistic motion in a projectile under the forced angular vibration condition based on ANSYS as claimed in claim 1, wherein in step 2, a three-dimensional geometric model of a gun barrel, the projectile and a flow field is established by using three-dimensional computer aided design software SOLIDWORKS, and a geometric model file is output, wherein the projectile is streamline as a whole, and the size of a projectile band is slightly smaller than the caliber of the gun.
4. The simulation method of ballistic motion in a projectile under the forced angular vibration condition based on ANSYS according to claim 1, wherein in step 3, the established geometric model is introduced into an ANSYS Workbench software platform, a solid domain and a fluid domain are divided through Boolean operation, a flow field area is subdivided into an inner flow field, a transition area and an outer flow field, then meshes are divided in a mesh module, wherein in order to adapt to the requirement of the moving meshes, the inner flow field area and the transition area near the projectile and the barrel are divided into second-order tetrahedral meshes, and hexahedral meshes are divided in the outer flow field area.
5. The method for simulating projectile internal trajectory motion under the forced angle vibration condition based on ANSYS as claimed in claim 1, wherein in step 4, a bidirectional fluid-solid Coupling solver is established on an ANSYS Workbench software platform, simulation conditions are set, bidirectional fluid-solid Coupling numerical simulation is performed, so as to obtain the motion state of the projectile and the distribution of flow fields inside and outside the bore, wherein after entering the ANSYS Workbench software platform, Structural dynamics solution is performed through a Transient Structural module, fluid dynamics solution is performed through a FLUENT module, information exchange between the Transient Structural module and the FLUENT module is realized through a System Coupling module, and finally, the motion state parameters of the projectile at each moment in the bore and during delivery are obtained, wherein the parameters comprise displacement, speed, delivery time, stress distribution and the distribution condition of outflow fields in the bore, and the specific method comprises the following steps:
introducing the solid domain grid into a Transient Structural calculation module, setting conditions of material parameters of the projectile and the cannon barrel, contact surfaces of the projectile and the barrel, projectile rotation speed, forced angular vibration angular speed omega of the cannon barrel, gravity magnitude and direction, fluid-solid coupling surface and the like in the Transient Structural calculation module, solving the motion state of the projectile at each moment, calculating the mass of the projectile by combining the geometric shapes of the projectile and the cannon barrel, and giving parameters such as material density, elastic modulus, Poisson ratio and the like;
in the solving process of the Transient Structural module, the basic equation for controlling the solid motion is as follows:
Figure FDA0002837533460000023
in the formula: msIs a quality matrix; csIs a damping matrix; k is a radical ofsIs a stiffness matrix; r issIs the solid displacement; tau issStress to which the solid is subjected;
after solving at each time step, storing state data of displacement, stress, deformation and the like of the projectile, and transmitting the displacement data of the projectile to the Fluent module through a System counting module to serve as a calculation condition in the Fluent module;
introducing a fluid domain grid into a FLUENT module, taking a fitted hearth pressure curve equation as an inlet pressure condition in a Transient Structural module, setting conditions such as a pressure outlet, a turbulence equation, a moving grid, a solving method and a solving time step length, solving the distribution condition of the flow field at each moment by combining shot motion data obtained from the Transient Structural module, storing the solving result, and transmitting pressure information on a contact surface corresponding to a fluid-solid Coupling surface back to the Transient Structural module through a System Coupling module, wherein the Transient Structural module starts to calculate the next time step according to the calculation result of the previous time step and feedback data in the FLUENT;
in the solving process of the Fluent module, the fluid is controlled by three conservation equations respectively:
(1) mass equation:
Figure FDA0002837533460000031
in the formula: u. ofx、uy、uzThe ratio of the velocity components is the velocity components in the x, y and z directions; t is time; ρ is the density.
(2) The momentum equation:
Figure FDA0002837533460000032
in the formula: p is the pressure on the fluid microcell body; μ is the dynamic viscosity of the fluid; f is the volume force;
Figure FDA0002837533460000033
is a hamiltonian.
(3) Energy equation:
Figure FDA0002837533460000034
in the formula: e is the total energy of the fluid micelle, including the sum of internal energy, kinetic energy and potential energy; p is the pressure on the fluid microcell body; j. the design is a squarejIs the diffusion flux of component j; h isjIs the enthalpy of component j; k is a radical ofefA conductivity that is effective heat; tau iseffEffective viscous stress; u is a velocity vector; shIs a heat source item.
The System Coupling module is used as a channel for data exchange, and the conditions of data exchange content, solving time and solving step number are set in the System Coupling module so as to control the common solving time and step length of the two modules;
in the process of data exchange in the System Coupling, the equivalent exchange of displacement and stress results between fluid and solid needs to be carried out under the bidirectional fluid-solid Coupling action, and the control equation is expressed as:
n·τf＝n·τs
rf＝rs
in the formula: tau isfThe fluid at the interface is stressed; r isfIs the fluid displacement at the interface; n is a unit vector.
Through the numerical simulation, the motion state parameters of the shot at each moment in the bore and during the discharge of the shot are obtained, wherein the motion state parameters comprise displacement, speed, discharge time, stress distribution and the distribution condition of the internal and external flow fields of the cannon barrel.
6. An ANSYS-based simulation system of intraprojectile ballistic motion under forced angle vibration conditions, characterized in that simulation of intraprojectile ballistic motion under ANSYS-based forced angle vibration conditions is performed based on the method of any one of claims 1-5.
7. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor when executing the computer program implementing the method of any one of claims 1-5 for simulation of intraprojectile ballistic motion under ANSYS-based forced angular vibration conditions.
8. A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method of any of claims 1-5 for simulation of intraprojectile ballistic motion under forced angular vibration conditions based on ANSYS.
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