A dynamic simulation method suitable for air dropping of fire extinguishing bag cluster

Abstract

The application discloses a kind of dynamics simulation simulation methods suitable for fire extinguishing bag cluster air drop, the steps of this method include: establishing fire extinguishing bag physical model, physical model discretization processing, fire extinguishing bag cluster simulation and simulation simulation and real working condition prediction, this method can accurately simulate fire extinguishing bag drop point distribution, optimize fire extinguishing resource allocation, the delivery strategy of fire extinguishing bag can adapt to changeable meteorological environment, according to real-time meteorological data and fire field change dynamically adjusts the delivery strategy of fire extinguishing bag, so that fire extinguishing action can quickly respond to the change of on-site situation, this real-time adjustment capability greatly improves the flexibility and effectiveness of fire extinguishing action, provides strong decision support for firemen.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of firefighting technology, and in particular to a dynamic simulation method suitable for cluster air-drop of fire extinguishing bags, which provides technical support for auxiliary decision-making and effect prediction of unmanned aerial vehicle fire extinguishing tasks, thereby improving fire extinguishing efficiency and safety. BACKGROUND

[0002] In the prior art, the deployment of fire extinguishing bags mainly relies on manual operation and simple physical calculations, which have certain limitations in actual operation. For example, Chinese patent CN 118105652 A discloses a self-filling fire extinguishing bag group, which is composed of self-filling fire extinguishing bags. The self-filling fire extinguishing bag includes a bag body with an internal space, and a fire extinguishing agent is encapsulated in the internal space. The fire extinguishing bag group includes at least two, preferably at least four self-filling fire extinguishing bags. Adjacent self-filling fire extinguishing bags share a sealing edge and are connected to each other through the sealing edge. A through hole is arranged in the sealing edge. A center hole is arranged at or near the geometric center of the self-filling fire extinguishing bag group. In addition, a hydrophilic-hydrophobic gradient coating can be arranged on the bag body, so that the bag body is configured to allow water to pass from the outside of the bag body to the inside of the bag body in one direction. The self-filling fire extinguishing bag group is deployed in the form of a fire extinguishing bag group, which facilitates the formation of a continuous fire-retardant belt and improves fire extinguishing efficiency. In addition, due to the one-way water permeability, the flexible operation requirements of fire extinguishing aircraft can be met and the leakage of fire extinguishing agent can be effectively avoided. By using polylactic acid material to make the fire extinguishing bag group, the environmental protection requirements for forest fire extinguishing are met. However, in the actual operation process of this technical solution, it is often difficult for the deployment personnel to accurately assess the number and deployment position of the required fire extinguishing bags, resulting in resource waste or insufficient coverage. In addition, the existing deployment method does not fully consider complex meteorological conditions such as changes in wind speed and direction, which have a significant impact on the distribution of fire extinguishing bag landing points.

[0003] For example, Chinese patent CN 118012049A discloses a locomotive cooperative dangerous area fire extinguishing and rescue method based on image processing. The system includes a rescue helicopter and an intelligent fire truck. The rescue helicopter is equipped with a cloud image processing camera, a cloud infrared imaging camera, a bomb thrower, a video transmission and communication module, an electric pulley set, a laser ranging module, and the intelligent fire truck is equipped with a cloud image processing camera, a mechanical arm, an all-terrain tracked wheel, a ranging and obstacle avoidance module, a bomb thrower, a dangerous goods temporary storage box, a video transmission and communication module. The rescue helicopter is used to make overall judgment on the fire scene, send the intelligent fire truck into the fire scene at a specific location, plan the air route and transmit the information to the intelligent fire truck and the ground terminal, transport dangerous goods, and recover the intelligent fire truck to complete the fire extinguishing task of the main passage. Although this technical solution provides advanced air monitoring and guidance capabilities for the entire rescue process through various sensors and devices, there are still the following problems and shortcomings in the process of throwing:

[0004] First, the throwing precision is insufficient. Due to the lack of accurate simulation and prediction, the drop point distribution of the fire extinguishing bag often does not meet the expectations, resulting in poor fire extinguishing effect.

[0005] Second, the resource allocation is unreasonable. It is difficult to accurately assess the number of fire extinguishing bags needed, which may lead to resource waste or ineffective control of the fire.

[0006] Third, the influence of meteorological conditions is ignored. The existing throwing method does not fully consider the influence of wind speed and direction and other meteorological conditions on the drop point of the fire extinguishing bag, resulting in unstable throwing effect.

[0007] Fourth, there is a lack of real-time adjustment capability. In the process of throwing, the existing technology cannot dynamically adjust according to real-time meteorological data and fire field changes, reducing the flexibility and efficiency of the rescue.

[0008] One of the important reasons for the above problems and shortcomings is that the existing technology lacks in-depth dynamic analysis and simulation of the fire extinguishing bag throwing process. The fire extinguishing bag is affected by multiple forces in the throwing process, including gravity, air resistance and lift, etc. The interaction of these forces is complex and difficult to accurately calculate by traditional methods. In addition, the existing technology does not consider the interaction between meteorological conditions and fire extinguishing bags, making it difficult to accurately predict the drop point distribution of the fire extinguishing bag. Therefore, the existing technology has obvious shortcomings in the accuracy of fire extinguishing bag throwing, the rationality of resource allocation, and the adaptability to meteorological conditions. Therefore, a simulation method is needed to improve the efficiency and effectiveness of fire extinguishing bag throwing. SUMMARY

[0009] Invention purposes: In order to solve the problems of the prior art, the application provides a dynamic simulation method suitable for cluster air drop of fire extinguishing bags, which fully considers the influence of meteorological conditions such as wind speed and wind direction during the fire extinguishing bag drop process, so as to improve the stability, reliability and fire extinguishing bag drop precision, when multiple fire extinguishing bags are dropped at the same time, how to consider the mutual influence between the fire extinguishing bags, that is, the aggregation effect, so as to more accurately predict the actual drop point distribution, and optimize the resource allocation, provide auxiliary decision support, optimize the air drop process of the fire extinguishing bags in a scientific and accurate manner, so as to improve the effect and efficiency of forest fire fighting.

[0010] Technical scheme: In order to achieve the above purpose, the application provides a dynamic simulation method suitable for cluster air drop of fire extinguishing bags, and the specific steps of the method include:

[0011] Step one, establishing a physical model of fire extinguishing bags

[0012] After analyzing the gravity, air resistance and lift of the fire extinguishing bag during the drop process, the fire extinguishing bag is regarded as a single point, the dynamic equation of the fire extinguishing bag is established based on the single point space three-degree-of-freedom equation to describe the motion of the fire extinguishing bag in space, in order to make the model more flexible to introduce the lift and drag coefficients, the characteristic length, the characteristic velocity and the characteristic time are used to carry out dimensionless processing on the dynamic equation, so as to simplify the calculation and enhance the universality of the model, the physical model of the fire extinguishing bag is established to simulate the motion characteristics of the fire extinguishing bag during the drop process; the dimensionless processing simplifies the equation and improves the calculation efficiency, which not only helps to reveal the nature of the physical process, but also reduces the numerical error in the calculation;

[0013] Step two, discrete processing of the physical model

[0014] In order to make the physical model be able to process data on the computer, the continuous dynamic model is discretized in time dimension, which involves dividing the time into multiple discrete intervals, and calculating the state quantity matrix s and the control matrix u of the fire extinguishing bag in each interval, through this discretization processing, the model can provide detailed state information of the fire extinguishing bag for each discrete time, which lays a foundation for subsequent simulation and analysis;

[0015] Based on the actual physical process of the fire extinguishing bag, the control quantity, the input quantity and the initial condition of the model are determined to meet the physical actual situation, according to the physical actual situation, the range of each physical parameter is set, the discrete processing method is used to solve the falling trajectory and drop point of the fire extinguishing bag at a specific drop height, and the continuous physical model is converted into a discrete form suitable for computer processing, so as to solve the numerical value of the fire extinguishing bag physical model;

[0016] Step three, cluster simulation of fire extinguishing bags

[0017] After obtaining the discretized physical model, the process of simultaneous launching of multiple fire extinguishing bags is simulated, given the initial height and launching speed, the physical model will generate the state quantity matrix and control matrix corresponding to each fire extinguishing bag according to the preset number, through the simulation of the launching process, the corresponding matrix value at each discrete time is recorded and stored, the fire extinguishing bag launching trajectory, speed change and the aggregation effect between them are obtained, and the simulation results will provide important data for analyzing the landing distribution and coverage effect of fire extinguishing bags;

[0018] Step four, simulation and real working condition prediction

[0019] According to the basic test conditions, Python is used for simulation, based on the simulation results, the fire extinguishing bag distribution area and density results are obtained, and compared with the experimental data, the accuracy of the model is verified, the verified model is used to predict the fire extinguishing bag launching situation under real flight working condition, through calculating and analyzing the final speed of fire extinguishing bag cluster landing, the time required for landing, the center position of cluster landing and the area covered by fire extinguishing bag, the fire extinguishing bag landing distribution map is generated.

[0020] As a further preferred embodiment of the present application, in step one, the single particle space three-degree-of-freedom equation calculation process of the fire extinguishing bag is as follows:

[0021] It is assumed that the main forces acting on the fire extinguishing bag after launching include gravity, air resistance and lift, in order to simplify the problem, only the horizontal uniform wind is considered, the vertical wind speed and wind direction change are ignored, and the main assumption conditions are as follows,

[0022] (1) The shape and mass distribution of the fire extinguishing bag remain unchanged after launching;

[0023] (2) The air density is uniform;

[0024] (3) The gravitational acceleration g is a constant;

[0025] (4) The horizontal wind is uniform, that is, the wind speed W and the wind direction remain unchanged;

[0026] (5) The motion of the fire extinguishing bag can be decomposed into X, Y and Z directions;

[0027] Based on the above assumptions, the single particle dynamics equation is as follows:

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] in, The quality of the fire extinguisher bags The speed of the fire extinguishing bag relative to the air. The rate of change of velocity of the fire extinguishing bag relative to the air. The angle between the fire extinguisher bag's velocity and the horizontal plane. Angle rate of change, The yaw angle of the fire extinguisher bag in the horizontal plane. Yaw angle rate of change, Drag, in the opposite direction to the airspeed of the fire extinguisher bag. Lift, perpendicular to the airspeed direction of the fire extinguisher bag. Roll angle, X , Y , Z The coordinates of the fire extinguisher bag in space. , , Fire extinguisher bag , , The velocity component in the direction.

[0035] As a further preferred embodiment of the present invention, the calculation process of dimensionless processing of the dynamic model in step one is as follows:

[0036] When performing dimensionless processing on dynamic models, appropriate characteristic quantities are usually selected to simplify the equations, making the coefficients and variables in the equations dimensionless. This facilitates the introduction of lift and drag coefficients, simplifies calculations and analysis. Dimensionless processing not only helps to reveal the essence of the physical process, but also reduces numerical errors in calculations and improves computational efficiency.

[0037] Selecting a feature: Feature velocity Among them, feature distance Characteristic Time .

[0038] The dynamic model is dimensionless based on characteristic quantities.

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] In matrix form, we have:

[0046]

[0047] where dimensionless variables are dimensionless airspeed dimensionless wind speed dimensionless spatial position , , and dimensionless time lift coefficient drag coefficient , dynamic pressure;

[0048] As a further preferred embodiment of the present application, in step two, the state matrix s contains the position and velocity information of the fire extinguishing bag.

[0049] As a further preferred embodiment of the present application, in step two, the control matrix u contains the control inputs that affect the movement of the fire extinguishing bag, such as lift coefficient and roll angle.

[0050] As a further preferred embodiment of the present application, in step two, the calculation process of discretizing the physical model is as follows:

[0051] (a) Based on the actual physical process of the fire extinguishing bag, determine the control and input variables in the model: In the dynamic system, the state matrix and the control matrix are used to describe the system state and control input. For the single-particle dynamic model described above, the state matrix and control matrix are defined as follows:

[0052]

[0053] (b) Determine the initial conditions of the model to conform to the actual physical reality:

[0054] Initial value matrix,

[0055]

[0056] (c) According to the actual physical situation, set the range of each physical parameter:

[0057]

[0058]

[0059] (d) solving the falling trajectory and landing point of the fire extinguishing bag at a specific release height by using time stepping method, and according to the recursive relationship, the discretization relationship is as follows:

[0060]

[0061] For the state quantity at time t, For the state quantity at time t, is the time difference between two times, is the state quantity change function;

[0062] .

[0063] As a further preferred embodiment of the present application, in step three, the cluster effect is based on the standard aggregation effect experimental data, and the physical correction is performed on the control variable range.

[0064] As a further preferred embodiment of the present application, the values of the control variables and are determined according to the aggregation effect experiment,

[0065] As a further preferred embodiment of the present application, the control variables and are functions of the change of the aggregation effect:

[0066]

[0067]

[0068] The correction of the coverage area can be performed by setting the control variable , defining as the horizontal dispersion intensity, adjusting the size of to conform to the test results, and using a quadratic function to fit, to obtain:

[0069]

[0070]

[0071] Due to the different landing aggregation states, the lift coefficient at landing is different, and the landing lift coefficient corresponding to different release heights is inconsistent, and the aggregation effect affects the aerodynamic force.

[0072] As a further preferred embodiment of the present application, the control variables include the time required for the balance speed, the time of the free fall is analyzed, and is easily obtained, which is the shortest time of falling, and the actual falling time of the fire extinguishing bag is longer than ,

[0073] Therefore, if the speed of the fire extinguishing bag affected by resistance has reached equilibrium within the integral time, the fire extinguishing bag also reaches equilibrium within the fire extinguishing bag falling time in the real longer time, the model can be simplified, that is:

[0074]

[0075]

[0076]

[0077] Assuming that the integral time is the free fall time , if the speed of the fire extinguishing bag has approached the experimentally measured speed within the integral free fall time , therefore, the speed of the fire extinguishing bag has reached equilibrium within the free fall time, and the gravity and the lift have also reached equilibrium.

[0078] Beneficial effects: the dynamic simulation method suitable for the cluster air drop of the fire extinguishing bag has the following advantages compared with the prior art:

[0079] (1) Accurately simulate the falling point distribution of the fire extinguishing bag: by establishing a single particle dynamics model and carrying out dimensionless treatment and discretization treatment, the motion trajectory of the fire extinguishing bag in a complex wind field can be accurately simulated. This simulation not only considers the lift and drag of the fire extinguishing bag itself, but also considers the aggregation effect between the fire extinguishing bags, so that the simulation result is closer to the actual situation. Compared with the prior art, the accurate simulation capability significantly improves the accuracy of the fire extinguishing bag drop, ensures that the fire extinguishing agent can uniformly cover the target area, and effectively improves the fire extinguishing efficiency.

[0080] (2) Optimize the allocation of fire extinguishing resources: according to the simulation result, the number of fire extinguishing bags required under different fire conditions is accurately evaluated, so as to realize the optimization of resource allocation. This optimization not only avoids waste of resources, but also ensures that the most effective fire extinguishing coverage can be realized under the condition of limited resources. Compared with the prior art, scientific calculation replaces rough estimation depending on experience, so that the resource allocation is more reasonable and efficient.

[0081] (3) Adapt to changing weather conditions: the changes of weather conditions such as wind speed and wind direction are fully considered in the simulation process, so that the drop strategy of the fire extinguishing bag can adapt to the changing weather environment. This adaptability is lacking in the prior art, which makes the fire extinguishing bag drop no longer limited by specific weather conditions, improves the flexibility and success rate of fire extinguishing operation, and provides reliable drop strategy even in the case of large changes in wind speed and wind direction, so as to ensure that the fire extinguishing bag can effectively cover the fire field.​

[0082] (4) Provide auxiliary decision-making and real-time adjustment capability: The simulation tool can provide real-time auxiliary decision-making support for firefighters. Through the simulation results, firefighters can intuitively understand the expected landing point and coverage range of the fire extinguishing bag, so as to make a more accurate fire extinguishing plan. In addition, the technical solution also allows dynamic adjustment of the fire extinguishing bag dropping strategy according to real-time meteorological data and fire field changes, so that the fire extinguishing action can quickly respond to changes in the field situation. Compared with the prior art, this real-time adjustment capability greatly improves the flexibility and effectiveness of the fire extinguishing action, and provides strong decision-making support for firefighters. BRIEF DESCRIPTION OF DRAWINGS

[0083] Figure 1 The schematic diagram is defined for the physical quantity related to the single particle space three-degree-of-freedom equation of the fire extinguishing bag.

[0084] Figure 2 The falling velocity analysis diagram of the fire extinguishing bag is shown.

[0085] Figure 3 The falling velocity analysis diagram of the fire extinguishing bag is shown. The falling velocity analysis diagram of the fire extinguishing bag is shown.

[0086] Figure 4 The falling velocity analysis diagram of the fire extinguishing bag is shown. The falling velocity analysis diagram of the fire extinguishing bag is shown.

[0087] Figure 5 The falling velocity analysis diagram of the fire extinguishing bag is shown. DETAILED DESCRIPTION

[0088] The present application will be further illustrated below in combination with the drawings and specific examples.

[0089] The present application is a kind of dynamic simulation simulation method suitable for fire extinguishing bag cluster air drop, the steps of the method include: establishing fire extinguishing bag physical model, physical model discretization processing, fire extinguishing bag cluster simulation and simulation simulation and real working condition prediction, the method can accurately simulate the fire extinguishing bag landing point distribution, optimize fire extinguishing resource allocation, the dropping strategy of fire extinguishing bag can adapt to changeable meteorological environment, and effectively provide auxiliary decision-making and real-time adjustment capability. EMBODIMENT

[0090] Step one, fire extinguishing bag physical model establishment

[0091] Firstly, after analyzing the gravity, air resistance and lift of the fire extinguishing bag during the dropping process, the fire extinguishing bag is regarded as a single particle. Based on the single particle space three-degree-of-freedom equation, the dynamics equation of the fire extinguishing bag is established to describe its movement in space. In order to make the model more flexible to introduce the lift and drag coefficients, the establishment process of the single particle space three-degree-of-freedom equation of the fire extinguishing bag is as follows:

[0092] Assume that the main forces on the fire extinguishing bag after being dropped include gravity, air resistance and lift, in order to simplify the problem, only consider the horizontal uniform wind, ignore the vertical wind speed and wind direction changes, the main assumptions are as follows,

[0093] (1) The shape and mass distribution of the fire extinguishing bag remain unchanged after being dropped;

[0094] (2) The air density is uniform;

[0095] (3) The gravitational acceleration g is a constant;

[0096] (4) The horizontal wind is a uniform flow, that is, the wind speed W and the wind direction remain unchanged;

[0097] (5) The movement of the fire extinguishing bag can be decomposed into X, Y and Z direction components;

[0098] Based on the above assumptions, the single-particle dynamics equation is as follows:

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] Wherein, : the mass of the fire extinguishing bag, : the speed of the fire extinguishing bag relative to the air, : the speed change rate of the fire extinguishing bag relative to the air, : the angle between the speed of the fire extinguishing bag and the horizontal plane, : the change rate of the angle : the yaw angle of the fire extinguishing bag in the horizontal plane, : the change rate of the yaw angle : the resistance, opposite to the direction of the air speed of the fire extinguishing bag, : the lift, perpendicular to the direction of the air speed of the fire extinguishing bag, : the roll angle, , , X : the coordinates of the fire extinguishing bag in space, Y , Z : the coordinates of the fire extinguishing bag in , , : the coordinates of the fire extinguishing bag in , 、 The velocity component in the direction of the velocity vector, the definition of the relevant physical quantities is shown in Figure 1

[0106] Then, the characteristic length, characteristic velocity, characteristic time are used to carry out dimensionless processing of the dynamic equation, so as to simplify the calculation and enhance the universality of the model, establish the physical model of the fire extinguishing bag, simulate the motion characteristics of the fire extinguishing bag in the process of throwing, the dimensionless processing simplifies the equation and improves the calculation efficiency, which is not only helpful to reveal the nature of the physical process, but also can reduce the numerical error in the calculation;

[0107] The calculation process of the dimensionless processing of the dynamic model is as follows:

[0108] In the dimensionless processing of the dynamic model, the appropriate characteristic quantity is usually selected to simplify the equation, so that the coefficients and variables in the equation are dimensionless, thereby facilitating the introduction of the lift and drag force coefficient, simplifying the calculation and analysis; Dimensionless processing not only helps to reveal the nature of the physical process, but also can reduce the numerical error in the calculation and improve the calculation efficiency.

[0109] Selection of characteristic quantity: characteristic velocity , the characteristic distance , the characteristic time .

[0110] Based on the characteristic quantity, the dynamic model is dimensionless processed,

[0111]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117] Written in matrix form, that is,

[0118]

[0119] Among them, the dimensionless variable is the dimensionless airspeed , the dimensionless wind speed , the dimensionless spatial position , , , and the dimensionless time , the lift coefficient ​, drag coefficient , is the dynamic pressure;

[0120] In this embodiment, the basic physical quantities of the fire extinguishing bag are:

[0121] Fire extinguishing bag mass m / kg 0.27 Acceleration of gravity g 9.8 Air density kg / m 3 ]] 1.225 Fire extinguishing bag size m x m 0.08×0.165

[0122] From the calculation, the relevant characteristic values are:

[0123]

[0124] Step two, physical model discretization processing

[0125] In order to make the physical model be able to carry on the data processing on the computer, the continuous dynamics model is discretized in time dimension, and this processing process involves dividing the time into multiple discrete intervals, and calculating the state quantity matrix s and control matrix u of the fire extinguishing bag in each interval; The state quantity matrix s contains the position and speed information of the fire extinguishing bag, and the control matrix u contains the control input affecting the movement of the fire extinguishing bag, such as the lift coefficient and the roll angle. Through this discretization processing, the model can provide detailed state information of the fire extinguishing bag for each discrete time, which lays a foundation for subsequent simulation and analysis;

[0126] The calculation process of the physical model discretization processing is as follows:

[0127] (a) Based on the actual physical process of the fire extinguishing bag, determine the control quantity and input quantity in the model:

[0128] In the dynamics system, the state quantity matrix and the control matrix are used to describe the system state and control input. For the above single-particle dynamics model, the following state quantity matrix and control matrix are defined:

[0129]

[0130] (b) Determine the initial conditions of the model to meet the actual physical actual:

[0131] The initial value matrix,

[0132]

[0133] (c) According to the physical actual situation, set the range of each physical parameter:

[0134]

[0135]

[0136] (d), the falling trajectory and landing point of the fire extinguishing bag with a specific release height are solved by using time stepping method, and according to the recursive relationship, the discretization relationship is as follows,

[0137]

[0138] For the state quantity at time t, For the state quantity at time t, is the time difference between two time points. is the state quantity change function,

[0139] .

[0140] Step three, simulation of fire extinguishing bag cluster

[0141] After obtaining the discretized physical model, the process of simultaneous release of multiple fire extinguishing bags is simulated. Given the initial height and release speed, the physical model will generate the state quantity matrix and control matrix corresponding to each fire extinguishing bag according to the preset number. Through simulation of the release process, the corresponding matrix values at each discrete time are recorded and stored to obtain the fire extinguishing bag release trajectory, speed change and aggregation effect between them. The simulation results will provide important data for analyzing the landing distribution and coverage effect of fire extinguishing bags;

[0142] According to the experimental data, different initial heights correspond to different landing aggregation states. When the release height is low, the distance between the fire extinguishing bags at landing is small; when the release height is high, the distance between the fire extinguishing bags at landing is large. Given the landing speed, assuming that the fire extinguishing bag has reached the balance of gravity and aerodynamic lift at landing, the lift coefficient at landing can be calculated.

[0143] It is known that the weight is 0.27 kg, the characteristic area According to the balance of gravity and lift, we can get ; Therefore, the lift coefficient is .

[0144] It can be calculated that the landing lift coefficient corresponding to different release heights is not consistent. Due to the different landing aggregation states, the lift coefficient at landing is different, which shows that the aggregation effect affects the aerodynamic force.

[0145] The condition for the above inference to be true is: whether the fire extinguishing bag has reached the balance of gravity and aerodynamic lift at landing? As Figure 2 shown, this problem can be changed to whether the speed of the fire extinguishing bag is no longer changed at the end of the landing. If the speed of the fire extinguishing bag is no longer changed, it means that the fire extinguishing bag has reached the balance of gravity and aerodynamic lift.

[0146] It takes time to reach the equilibrium velocity, and the time of free fall is easy to analyze This is the shortest time of falling, and the actual falling time of the fire extinguishing bag is longer than Therefore, if The velocity of the fire extinguishing bag affected by resistance has reached equilibrium within the time, and the fire extinguishing bag also reaches equilibrium within the actual longer falling time of the fire extinguishing bag in the real longer time, so the model can be simplified as follows:

[0147]

[0148]

[0149]

[0150] The above equation can calculate its analytical and numerical solutions. This report adopts the numerical solution method, assuming that the integral time is the free fall time Then, if the velocity of the fire extinguishing bag has approached the experimentally measured velocity within the integral free fall time , it is considered that the velocity is in equilibrium.

[0151] The calculated results are shown in Table 1, and from Table 1, it can be seen that the simulation results are close to the experimental results. Therefore, within the free fall time, the velocity of the fire extinguishing bag has reached equilibrium, and the gravity and lift have also reached equilibrium. Therefore, the aggregation effect exists, which further affects the actual lift coefficient of a single fire extinguishing bag at different positions.

[0152] Table 1 Velocity simulation within the free fall integral time

[0153] Experimentally measured final velocity m / s 22.513 25.432 29.534 30.558 Velocity over free fall volume integral time m / s 19.8 23.8 28.5 30.2

[0154] Then, the lift coefficient in the original code is optimized, and the results are shown in Table 2, and the final simulation velocity and the experimentally measured final velocity are basically consistent.

[0155] Table 2 Simulation of final velocity and falling time

[0156]

[0157] Therefore, the control variables and are functions of the change of height (aggregation effect), as shown in Figure 3 The figure showing the change of with the drop height is as follows:

[0158]

[0159]

[0160] The correction of the coverage area can be achieved through control measures. Settings, definitions To determine the horizontal dispersion intensity, by adjusting... The size should conform to the test results, such as Figure 4 As shown The diagram illustrates the variation with deployment height. By fitting the data using a quadratic function, we obtain the following:

[0161]

[0162] ;

[0163] Due to different landing aggregation states, the lift coefficient at landing varies, and the landing lift coefficient corresponding to different deployment heights is not the same. The aggregation effect affects aerodynamic forces.

[0164] Step 4: Simulation and Prediction of Real-World Operating Conditions

[0165] Based on the basic experimental conditions, Python was used to conduct simulations. Based on the simulation results, the distribution area and density of fire extinguishing bags were obtained and compared with experimental data to verify the accuracy of the model. The verified model was used to predict the deployment of fire extinguishing bags under real flight conditions. By calculating and analyzing the final speed of the fire extinguishing bag cluster landing, the time required for landing, the center position of the cluster landing, and the area covered by the fire extinguishing bags, a landing distribution map of the fire extinguishing bags was generated.

[0166] Simulations were performed for four typical working conditions in the basic experiment, with drop heights of 50m, 100m, 200m, and 300m, respectively. Figure 5 The figure shows the distribution of fire extinguishing bags landing points at different heights. As can be seen, the landing points exhibit a Gaussian distribution, with higher points in the center and lower points around the edges. With increasing height, the landing points gradually disperse, the coverage area increases, and the coverage density decreases. These results are consistent with experimental results.

[0167] The quantitative comparison between simulation and experimental results is shown in Tables 3 and 4, with the endpoint velocity (Table 3) and coverage area (Table 4) selected as the two key parameters for comparison. Tables 3 and 4 show that the overall relative error between the theoretical simulation results and experimental measurements is <10%. The relative error decreases with increasing drop height because the base of the relative error is relatively large. In summary, the dynamic simulation model proposed in this study demonstrates good simulation performance for the descent of fire extinguishing bags.

[0168] Table 3 Comparison of simulated and experimental results of the endpoint velocity of the fire extinguishing bag

[0169] Drop height (m) Experimentally measured end velocity (m / s) Theoretically simulated end velocity (m / s) Error 50 22.513 20.70 8.8% 100 25.432 24.65 3.2% 200 29.534 29.10 1.5% 300 30.558 30.45 0.4%

[0170] Table 4 Comparison of simulation results and experimental results of fire extinguishing bag drop point coverage area

[0171] Drop height (m) Experimentally measured coverage area (m2) Theoretically simulated coverage area (m2) Error 50 39.18 41.5 5.6% 100 92.92 84.9 9.4% 200 262.54 262.9 0.1% 300 546.20 550.7 0.8%

[0172] The above is the model prediction data of the fire extinguishing bag drop situation under the real flight working condition, which is verified by actual operation.

[0173] The above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable the skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent transformation or modification made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method of dynamic simulation suitable for air dropping of clusters of fire extinguishing bags, characterized in that: The specific steps of the method include: Step one, physical model establishment of fire extinguishing bag After analyzing the gravity, air resistance and lift force experienced by the fire extinguishing bag during the dropping process, the fire extinguishing bag is regarded as a single particle. Based on the single particle space three-degree-of-freedom equation, the dynamics equation of the fire extinguishing bag is established. The dynamics equation is dimensionless processed using characteristic length, characteristic velocity and characteristic time to simplify the calculation and enhance the universality of the model. The physical model of the fire extinguishing bag is established to simulate the motion characteristics of the fire extinguishing bag during the dropping process. Step two, discrete processing of the physical model In order to enable the physical model to be data-processed on the computer, the continuous dynamics model is discretely processed in the time dimension. This processing process involves dividing the time into multiple discrete intervals and calculating the state quantity matrix s and the control matrix u of the fire extinguishing bag in each interval. Step three, simulation of fire extinguishing bag cluster After obtaining the discretely processed physical model, the process of simultaneously dropping multiple fire extinguishing bags is simulated. Given the initial height and dropping speed, the physical model will generate the state quantity matrix and the control matrix corresponding to each fire extinguishing bag according to the preset number. Through the simulation of the dropping process, the corresponding matrix values at each discrete time are recorded and stored to obtain the dropping trajectory, speed change and aggregation effect of the fire extinguishing bags. Step four, simulation and real working condition prediction According to the basic test conditions, Python is used for simulation. Based on the simulation results, the fire extinguishing bag distribution area and density results are obtained, which are compared with the experimental data to verify the accuracy of the model. The verified model is used to predict the fire extinguishing bag dropping situation under real flight conditions. Through calculation and analysis of the final speed, time required for landing, center position of the cluster landing and the area covered by the fire extinguishing bag cluster, a fire extinguishing bag landing distribution map is generated.

2. The method for dynamic simulation of the cluster air-drop of fire-extinguishing bags according to claim 1, characterized in that: In step one, the single particle space three-degree-of-freedom equation of the fire extinguishing bag is calculated as follows: Assuming that the main forces experienced by the fire extinguishing bag after being dropped include gravity, air resistance and lift force, in order to simplify the problem, only the horizontal uniform wind is considered, and the vertical wind speed and wind direction changes are ignored. The main assumptions are as follows, (1) The shape and mass distribution of the fire extinguishing bag remain unchanged after being dropped; (2) The air density is uniform; (3) The gravitational acceleration g is constant; (4) The horizontal wind is uniform, i.e. the wind speed W and wind direction remain unchanged; (5) The motion of the fire extinguishing bag can be decomposed into X, Y and Z direction components; Based on the above assumptions, the single particle dynamics equation is as follows: wherein m: mass of the fire extinguishing bag, U: velocity of the fire extinguishing bag relative to air, : rate of change of the velocity of the fire extinguishing bag relative to air, γ: angle of the fire extinguishing bag velocity with the horizontal plane, : rate of change of the angle γ, ψ: yaw angle of the fire extinguishing bag in the horizontal plane, : rate of change of the yaw angle ψ, D: drag, opposite to the direction of the fire extinguishing bag airspeed, L: lift, perpendicular to the direction of the fire extinguishing bag airspeed, φ: roll angle, X, Y, Z: coordinates of the fire extinguishing bag in space, : velocity components of the fire extinguishing bag in the X, Y, Z directions.

3. The method for dynamic simulation of the cluster air-drop of fire-extinguishing bags according to claim 1, characterized in that: In step one, the dimensionless processing of the dynamics model is calculated as follows: When dimensionless processing of the dynamics model is performed, appropriate characteristic quantities are usually selected to simplify the equation, so that the coefficients and variables in the equation are dimensionless, thereby facilitating the introduction of lift and drag coefficients, simplifying calculation and analysis. Selected characteristic quantity: characteristic velocity Characteristic distance Characteristic time t c = V c / g; Based on the characteristic quantities, the dynamics model is dimensionless processed, Written in matrix form, that is, where the dimensionless variables are dimensionless velocity v = U / V c dimensionless wind speed w = W / V c dimensionless spatial position x = X / L c , y = Y / L c , z = Z / L c and dimensionless time τ = t / t c , lift coefficient C L = L / q ∞ , drag coefficient C D = D / q ∞ , is the dynamic pressure.

4. The method for dynamic simulation of air-drop of cluster of fire-extinguishing bags according to claim 1, characterized in that: In step two, the state quantity matrix s contains the position and speed information of the fire extinguishing bag.

5. The method for dynamic simulation of air-drop of cluster of fire-extinguishing bags according to claim 1, characterized in that: In step two, the control matrix u contains the control inputs that affect the motion of the fire extinguishing bag, such as lift coefficient and roll angle.

6. The method for dynamic simulation of air-drop of cluster of fire extinguishing bags according to claim 1, characterized in that: The calculation process of the physical model discretization in step two is as follows: (a) Based on the actual physical process of the fire extinguishing bag, the control quantity and input quantity in the model are determined: in the dynamic system, the state quantity matrix s and the control matrix u are used to describe the system state and the control input, and for the single-particle dynamic model, the state quantity matrix and the control matrix are defined as follows: (b) The initial conditions of the model are determined to conform to the actual physical reality: The initial value matrix, (c) According to the physical reality, the range of each physical parameter is set: - φ max ≤ φ ≤ φ max (d) The falling trajectory and landing point of the fire extinguishing bag at a specific dropping height are solved by using the time stepping method, and according to the recursive relationship, the discretization relationship is as follows, s N is the state quantity at time t N is the state quantity at time t N-1 is the state quantity at time t N-1 is the state quantity at time t N is the state quantity at time t N-1 is the state quantity at time t is the state quantity change function 7. The method for dynamic simulation of air-drop of cluster of fire-extinguishing bags according to claim 1, characterized in that: In step three, the cluster effect is based on the standard aggregation effect experimental data, and the control variable range is physically corrected.

8. The method for dynamic simulation of the cluster air-drop of fire-extinguishing bags according to claim 7, characterized in that: Controlled variables and φ max The values of φ were determined according to the aggregation effect experiment.

9. The method for dynamic simulation of the cluster air-drop of fire-extinguishing bags according to claim 8, characterized in that: Controlled variables and φ max Function of the change in the aggregation effect: R 2 ＝0.996 The correction for the area covered can be defined by setting the amount φ max For the horizontal dispersion intensity, the size of φ max was adjusted to fit the test results, using a quadratic function, which gave: φ max = -2.2804 x 10 -6 h 2 + 1.1352 x 10 -3 h + 8.3602 x 10 -1 R 2 ＝0.941 Due to the different landing aggregation states, the lift coefficient at landing is different, and the landing lift coefficient corresponding to different dropping heights is inconsistent, and the aggregation effect affects the aerodynamic force.

10. The method for dynamic simulation of air-drop of cluster of fire-extinguishing bags according to claim 7, characterized in that: The control variables include the time needed to reach equilibrium velocity, the time to analyze the free fall, and the time to get the This is the shortest time for the fall, and the actual fall time of the fire extinguishing bag is longer than t f ; Therefore, if t f If the speed of the fire extinguishing bag with resistance has reached equilibrium within a certain time, the fire extinguishing bag also reaches equilibrium within the fire extinguishing bag falling time in the real longer time, and the model can be simplified, that is: Assume the integration time is the free fall time t f Then, if the velocity of the fire extinguishing bag has reached the experimentally measured velocity within the integration free fall time t f Therefore, the velocity of the fire extinguishing bag reaches equilibrium within the free fall time, and the gravity and the lift also reach equilibrium.

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