A simulation method for low-profile evacuation of personnel in a fire environment

Abstract

The present invention provides a method for simulating low-posture evacuation of personnel in a fire environment, comprising the following steps: S1: modeling a fire scene, and calculating and generating the time and space distribution of a temperature field; S2: calculating the shortest path from any position in the scene to a destination, and determining the expected movement direction when there are personnel at any position in the scene; S3: allocating a certain number of personnel to the fire scene, initializing the positions, masses, and postures of the personnel, wherein the posture is selected from one of three postures: crawling with hands and knees touching the ground at the same time, squatting with the upper body upright and knees bent, and walking at the waist with the upper body bent and knees straight; S4: establishing a personnel motion equation, m i dv i / dt=F i , where i represents the number of the individual, F i 、v i They represent the resultant force and velocity vector on individual i, m i represents the mass of individual i, and t is the time; S5: Solve the personnel motion equation to obtain the motion trajectory of each person, that is, the evacuation path.

Description

Technical Field

[0001] The invention relates to the technical field of personnel evacuation, and in particular to a simulation method for low-profile evacuation of personnel in a fire environment. Background Art

[0002] The crowd evacuation simulation system is used to analyze the evacuation process in a fire environment and accurately predict the evacuation time and the distribution of high-risk areas. This is of great significance for formulating scientific emergency response plans, evacuation strategies and rescue measures, as well as evaluating the rationality and effectiveness of building design.

[0003] In a fire environment, as the fire spreads, smoke increases, and temperature rises, people may adopt special low-motion postures such as bending over and crawling to evacuate in order to avoid the stimulation and injury caused by low visibility and high temperature. Currently, there is a lack of mature technical tools for the calculation and evaluation of the low-motion evacuation process.

[0004] Most existing studies have considered the impact of fire environment and movement posture during evacuation independently. Research on low-posture evacuation mainly focuses on experimental data in a fire-free environment, while evacuation models related to fire basically consider upright walking, and rarely consider evacuation in postures such as crawling. In addition, when considering the impact of fire sources, existing fire evacuation models often simplify fire sources as physical obstacles, fail to consider the complex interaction between fire sources and pedestrians, ignore the specific movement patterns displayed by people in the face of fire, and insufficiently consider the impact of people's psychological state in fire situations, failing to capture behavioral changes at a more macro level.

[0005] Therefore, when simulating the evacuation of people in a fire environment, it is necessary to fully consider the movement characteristics of the crowd in a low posture, as well as the interaction pattern between people and fire sources, and establish an evacuation model that comprehensively considers the impact of fire sources and low postures. Summary of the invention

[0006] The present invention provides a method for simulating low-profile evacuation of personnel in a fire environment, comprising the following steps:

[0007] S1: Model the fire scene and calculate the time and space distribution of the temperature field;

[0008] S2: Calculate the shortest path from any location in the scene to the destination, and determine the expected direction of movement when there is a person at any location in the scene;

[0009] S3: assign a certain number of personnel to the fire scene, and initialize the positions, masses, and postures of the personnel, wherein the posture is selected from one of the following three postures: crawling with hands and knees touching the ground at the same time, squatting with the upper body upright and knees bent, and walking at the waist with the upper body bent and knees straight;

[0010] S4: Establish the personnel motion equation, m i dv i / dt=F i , where i represents the number of the individual, F i 、v i They represent the resultant force and velocity vector of individual i, respectively, and m i represents the mass of individual i, and t is the time;

[0011] Furthermore, in step S4, the resultant force on individual i includes: self-driving force f i , individual i is subject to the interaction force of other individuals The combined force between individual i and the environment ∑ W f iW , the physical force f of the fire source on individual i iphy 、The psychological force of fire on individual i ipsy ;

[0012] in represents the force exerted by individual j on individual i, f iW It represents the force of the environment W on individual i, that is:

[0013]

[0014] Furthermore, each individual person is abstracted as an ellipse, the fire source is abstracted as a circle, and mathematical expressions of the various forces acting on the personnel are constructed and solved to obtain the accurate movement trajectory of the personnel.

[0015] In the force analysis of individuals with low postures in a fire, the present invention takes into full account the complex interaction between the fire source and pedestrians, including the physical force of the fire source on the individual and the psychological force of the fire source on the individual, thereby associating the fire with the posture of the personnel, and thus being able to more accurately describe the movement patterns of the personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the main steps of the personnel low-profile evacuation simulation method of the present invention;

[0017] Figure 2 is a schematic diagram of the interaction between individuals i and j when there is no physical contact;

[0018] Figure 3 It is a schematic diagram of the interaction between individuals i and j when there is physical contact;

[0019] Figure 4 is a schematic diagram of the interaction between individual i and boundary W when there is no physical contact;

[0020] Figure 5It is a schematic diagram of the interaction between individual i and boundary W when there is physical contact;

[0021] Figure 6 is a schematic diagram of the direction of individual i circumventing the fire source;

[0022] Figure 7 Schematic diagram of the simulation scenario;

[0023] Figure 8 This is a schematic diagram of the scene built in FDS;

[0024] Fig. 9 is the temperature distribution map of the simulation scene;

[0025] Fig.10 It is a schematic diagram of the time cost of the scenario;

[0026] Fig.11 is a schematic diagram of the desired direction;

[0027] Fig.12 This is the simulation result diagram of the KHC crowd movement trajectory;

[0028] Fig.13 This is the SQW crowd motion trajectory simulation result diagram;

[0029] Fig.14 This is the simulation result of STW crowd motion trajectory. DETAILED DESCRIPTION

[0030] See also Figure 1 ,The simulation method for low posture evacuation of personnel in a fire environment mainly includes the following steps:

[0031] S1: Model the fire scene and calculate the time and space distribution of the temperature field;

[0032] This step generally uses the fire dynamics simulation software FDS to build a scene model, set fire parameters according to the spatial characteristics of the building structure, building material properties, fire type and power, simulate the fire situation, and obtain the spatiotemporal distribution information of the temperature field after the fire occurs.

[0033] S2: Calculate the shortest path from any location in the scene to the destination, and determine the expected direction of movement when there is a person at any location in the scene;

[0034] This step is used to generate the shortest path from any position in the fire scene to the destination (exit) position, thereby determining the expected movement direction of each position in the fire scene if it is occupied by a person.

[0035] Among them, the generation of the shortest path belongs to the existing technology. For example, the Fast Marching Method (FMM) is used to establish a connection between any position (x, y) in the scene and the time cost of reaching the destination from the position at a speed v(x, y), and obtain the time cost field T(x, y) of the scene. The negative gradient of the time cost field T(x, y) is used Represents the local shortest path direction from any location to the target area. Starting from the current location, connect the negative gradient direction of the current location to the target area in sequence to generate the shortest path to the destination area.

[0036] S3: assign a certain number of personnel to the fire scene, and initialize the positions, masses, and postures of the personnel, wherein the posture is selected from one of the following three postures: crawling with hands and knees touching the ground at the same time, squatting with the upper body upright and knees bent, and walking at the waist with the upper body bent and knees straight;

[0037] When simulating the movement of people, based on experimental observations, people have three typical low postures: Knee and Hand Crawling (KHC) with both hands and knees touching the ground, Squat Walking (SQW) with the upper body upright and knees bent, and Stoop Walking (STW) with the upper body bent and knees straight. The behavior patterns are different in different postures. For example, the free movement speed in the crawling mode is lower than in other modes.

[0038] S4: Establish the personnel motion equation, m i dv i / dt=F i , where i represents the number of the individual, F i 、v i They represent the resultant force and velocity vector of individual i, respectively, and m i represents the mass of individual i, and t is the time;

[0039] The establishment of the equation of motion is mainly based on Newton's second law. In the force analysis of individual personnel, five forces are considered, including self-driving force, interaction force between individuals, interaction force between individuals and environmental boundaries, physical force of fire source on individuals, and psychological force of fire source on individuals.

[0040] As the main innovation of the present invention, in the force analysis of individuals with low posture in a fire, the anisotropy of the forces between individuals is fully considered for the special posture of low posture personnel, and the interaction force between individuals is corrected by position and velocity anisotropy parameters. The newly introduced physical force of the fire source on the individual and the psychological force of the fire source on the individual fully consider the complex interaction between the fire source and pedestrians, thereby associating the fire development process with the posture of the personnel. In addition, considering the comprehensive influence of temperature and crowd density on the movement speed, a more reasonable expected speed is set in combination with the scene structure characteristics, so that the movement law of personnel can be described more accurately. Compared with the existing technology, the comprehensive influence of low posture and fire environment on the movement characteristics of personnel is fully considered, and the avoidance and detour behavior of personnel and the path selection strategy for fire sources in different states during the evacuation process can be more reasonably described.

[0041] S5: Solve the personnel motion equation to obtain the motion trajectory of each person, that is, the evacuation path.

[0042] The main forces acting on personnel are introduced below:

[0043] (1) Self-motivation:

[0044] The self-motivation f of individual i i The calculation of is shown in formula (1), which is used to quantify the driving force of individual movement, that is, the intensity of the desire to reach the destination as soon as possible.

[0045] f i =m i (v e,i (t)-v i (t)) / τ i ,#(1)

[0046] Where m i represents the mass of individual i, v e,i (t) represents the expected speed of individual i, and its direction is determined by the direction field determined by the expected direction generation module, v i (t) represents the actual movement speed and relaxation time τ of individual i i It can reflect the intensity of individual i's subjective willingness to achieve the expected speed.

[0047] Stimulated by the high temperature of the fire scene, evacuees will speed up to pass through the high temperature area to reduce discomfort. At the same time, excessively high temperatures will also lead to reduced evacuation capacity and reduced evacuation speed. In order to reflect this feature, this model proposes a temperature influence factor f v (T), as shown in Formula 1-1.

[0048]

[0049] Where: v in formula (1-1)max is the maximum movement speed that an individual can achieve in the corresponding posture; v free is the individual's free movement rate; T, T1, T2 and T3 are the temperatures at the current position, the individual feeling uncomfortable, the individual being injured, and the individual dying, respectively.

[0050] The expected speed of individual i at a certain time t |v e,i (t)|Except for the free motion rate v free In addition to the influence of the local density of the crowd at its location, ρ i (t). As the crowd density increases, the expected speed tends to decrease. When the local density reaches a certain threshold, the expected speed remains unchanged. The model introduces the density influencing factor f ρ , the expected speed is ultimately determined by formula 1-2.

[0051]

[0052] Where: j represents the location of individual i All individuals within the surrounding radius R (including i), Represents the position coordinates of individual j, and the size of R determines The influence range of surrounding pedestrians considered in the local density process is usually taken as R = 1m.

[0053] (2) Interaction forces between individuals

[0054] As shown in formula (2):

[0055]

[0056] Among them: the anisotropy coefficient W is used l and W v To reflect the interaction between individuals Weights for different directions and speed differences.

[0057] W l =k l +(1-k l )(1+cosα i ) / 2,#(3)

[0058] W v =k v +(1-k v )[1+(v j -v i )·n ij / |v j -v i |] / 2, #(4)

[0059]

[0060] Where: In formula (3), k l is the position anisotropy parameter, with a value range of [0, 1]. The personnel are abstracted as ellipses. i It is the angle between the movement direction of individual i and the line connecting the center points of the ellipses of individuals i and j, and its value range is [0°, 180°].

[0061] In formula (4), k v is the velocity anisotropy parameter, with a value range of [0, 1], v i 、v j is the movement speed of individuals i and j.

[0062] In formula (5), r ij -d ij represents the adjacent distance between individual i and individual j on the line connecting their body centers, such as Figure 2 .

[0063] n ij represents the normalized vector from the center of j to the center of i. Constants A and B reflect the strength and scope of social force, respectively. g(x) is the Heaviside function, which is used to determine whether there is physical contact between individuals. ij It represents the direction of the sliding friction force generated by body contact, which is a tangential normalized vector and is related to n ij The direction is perpendicular to and is always opposite to the tangential relative velocity direction of individual i (that is, the angle with the velocity direction of individual i is greater than 90°), such as Figure 3 .

[0064] Formula (6) indicates that the speed difference between individual i and individual j is ij The projection in the direction, the constant parameters K and k represent the strength of the reaction force and friction force respectively.

[0065] (3) Interactions between individuals and the environment

[0066] As shown in formula (7):

[0067]

[0068] The force acting on the boundary with the environment f iW The distance between individuals and environmental boundaries such as walls can be limited to avoid overlaps that violate reality. Among them, constants A and B reflect the intensity and scope of social forces, respectively.

[0069] See also Figure 4-5 , r i -d iWRepresents the difference between the body width of individual i and the distance from its center to the boundary W wall. A value greater than 0 indicates that there is physical contact and potential squeezing between the individual and the wall, and a value less than 0 indicates that there is no physical contact between the individual and the wall. iW represents the normalized vector from the boundary W to the center of individual i, g(x) is the Heaviside function, which is used to determine whether there is physical contact between the individual and the boundary; t iW It represents the direction of the friction force generated by the contact between the individual and the wall. It is a tangential normalized vector, which is opposite to the tangential relative velocity direction of individual i (that is, the angle with the velocity direction of individual i is greater than 90°).

[0070] represents the speed of individual i at t iW The projection of the direction is determined by formula (8), and the constant parameters K and k represent the strength of the reaction force and friction force respectively.

[0071]

[0072] (4) Physical force of fire on individuals

[0073] In the present invention, f iphy Describes the physical force exerted on individual i by the fire source, reflecting the tendency of the evacuated individual to move away from the fire source after being physiologically stimulated in the fire environment. Its magnitude is related to the temperature of the individual's location. The specific expression is shown in formula (9).

[0074] f iphy =[A p (exp((T i -T0) / B p )-1)(1+|cosα iH |) / 2]n iH ,#(9)

[0075] Where: In formula (9): A p and B p are all constants, reflecting the expected degree of individual i to stay away from the fire source and the affected temperature range respectively; T0 is the ambient temperature (room temperature under normal circumstances, such as 20-30℃), T i is the temperature felt by the personnel's head (which can be obtained by importing the fire environment data into the module mentioned above); see Figure 6 , n iH Represents the unit vector from the center of the fire source to the person's head, d e,n Represents the unit vector of the vertical outlet, α iH n iH With d e,n Angle.

[0076] (5) The psychological impact of fire on individuals

[0077] When the fire source appears in the individual's field of vision, the psychological force f ipsy is activated. ipsy As the distance between the individual and the fire source decreases, it increases. Under its influence, the individual will actively avoid the fire source and maintain a certain safe distance. The specific expression is shown in formula (10).

[0078]

[0079] In the above formula, the first term on the right side represents f ipsy The activation mechanism of iH ≥π / 2, the fire source is within the personnel’s field of vision. iH <π / 2, the psychological effect of the fire source on the individual does not need to be considered, f ipsy =0.

[0080] See also Figure 6 , d e,t represents the unit vector parallel to the exit, Δy represents the distance between the head of individual i and the center of the fire source in d e,t Projection distance in the direction, d e,t Represents the unit vector of the parallel exit, r H is the radius of the fire source; d iH represents the distance between individual i and the fire source; constant B s , B y They represent the distance of the fire source's psychological effect on the individual, and the influence coefficient of the evacuation path affected by the fire source on the psychological effect, A n,s and A t,s Represent the expected intensity of individuals staying away from and avoiding fire sources, is the unit vector pointing from the center of the fire source to the head of individual i. iH is perpendicular to n iH The specific direction is related to the danger level and evacuation distance of the path chosen by individual i, as shown in the following formula

[0081]

[0082] where e H Represents the risk factor, are the average temperatures on the two evacuation paths separated by the fire source, d1 and d2 represent the lengths of the two evacuation paths (evacuation path 1 that points directly from the personnel's head to the exit, and evacuation path 2 that bypasses the fire source). In order to simplify the calculation, the following can be used: Figure 6 The length of line segments OA and OAB is used as the substitute, and point B is the center of the exit. Among them, O is the position of the head of the person, and OA and OB are tangent to the periphery of the fire source respectively.

[0083] Therefore, the motion description of the low-posture motion individual in the low-posture motion module under fire environment is as follows:

[0084]

[0085] The personnel motion module is mainly used to establish the motion equations of low-profile personnel in a fire environment and calculate the trajectory of personnel.

[0086] The following is a specific calculation example using the above simulation method. Figure 7-8 The room size is 1m×1m, the exit width is 1m, the height of the ceiling and exit are set to 3m and 2m respectively, and a 1m×1m fire source is set in the center of the room. The combustion material is polyurethane foam, a widely used furniture material. The fire simulation parameters are set as shown in the following table. FDS software is used for simulation to obtain fire scene data such as the room temperature field and smoke distribution.

[0087] Table 1 Fire simulation parameters of FDS model

[0088]

[0089]

[0090] See also Fig. 9 , the fire simulation data at a height of 1m above the ground is selected as the fire characteristic data input in the model. Since pedestrians will show a low posture only when the smoke layer gathers and descends to a certain height, most of the existing experimental studies control the height at 1-1.6m, and the height of the human body in the low posture is also about 1m, so the temperature 1m above the ground is selected.

[0091] The room area is gridded, the exit is taken as the starting point, that is, the known point set, the fire source is regarded as an obstacle, the time cost is infinite and set to nan value, and the time cost field T ( Fig.10 ), use the gradient descent method to obtain the direction of the fastest gradient descent at each grid in the generated time cost field, and use this direction as the local desired direction of each grid ( Fig.11 ).

[0092] When simulating the movement of a person, the person's posture is first determined. Based on experimental observations, there are three typical low postures of a person: Knee and Hand Crawling (KHC) with both hands and knees touching the ground, Squat Walking (SQW) with an upright upper body and bent knees, and Stoop Walking (STW) with a bent upper body and straight knees. The calculation parameters for each posture are different, see the table below for details.

[0093] Table 2 Summary of fire source force parameters

[0094] Low Profile Model <![CDATA[A p (N)]]> <![CDATA[B p (℃)]]> <![CDATA[A n,s (N)]]> <![CDATA[A t,s (N)]]> <![CDATA[B s (m)]]> KHC 600 130 130 1500 3 QW 2000 300 400 7000 1 STW 70 20 400 6000 1.5 Low Profile Model <![CDATA[v free (m / s)]]> <![CDATA[v max (m / s)]]> τ(s) <![CDATA[f ρ (m 3 / s)]]> KHC 0.72 3 0.53 0 QW 0.92 3.5 0.87 1.14 STW 1.44 4.5 0.85 1.28

[0095] Table 3 Other parameter values

[0096]

[0097]

[0098] The final simulated evacuation trajectories and speed distributions of the three pedestrian postures are shown in the figure below: Figure 12-14 As shown. It can be seen that for the same ambient temperature distribution, there are certain differences in the speed, evacuation efficiency and spatial distribution of trajectories when evacuating in different postures. When crawling from a single-exit room, due to the large space occupied by individuals and the slow speed, once exiting, some individuals will be relatively close to the high-temperature fire source. When evacuating by bending over and squatting, most individuals can quickly avoid the high-temperature area.

[0099] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A simulation method for low-profile evacuation of personnel in a fire environment, characterized in that: The following steps are involved: S1: Model the fire scene and calculate the time and space distribution of the temperature field; S2: Calculate the shortest path from any location in the scene to the destination, and determine the expected direction of movement when there is a person at any location in the scene; S3: assign a certain number of personnel to the fire scene, and initialize the positions, masses, and postures of the personnel, wherein the posture is one of the following: crawling with both hands and knees touching the ground, squatting with the upper body upright and the knees bent, and walking at the waist with the upper body bent and the knees straight; S4: Establish the personnel motion equation, ,in, i The number of the individual person. , Respectively represent individuals i The net force and velocity vector, Represents an individual i Quality, t For time; S5: Solve the personnel motion equation to obtain the motion trajectory of each personnel, that is, the evacuation path; In step S4, individual i The combined forces include: self-driving force ,individual i The combined force of the interaction with other individuals ,individual i The combined force between the environment 、The impact of fire on individuals i The physical force 、The impact of fire on individuals i Psychological force ; in Represents an individual j For individuals i The force of It represents the effect of environment W on individual i The force of ； Each individual is abstracted as an ellipse, and the self-driving force Determined by the following formula: , in Represents an individual i Quality, t For time; Represents an individual i The expected speed, Represents an individual i The actual speed of movement, is the relaxation time, which indicates the intensity of individual i’s subjective willingness to reach the expected speed; Expected speed The direction is determined by step S2, and the size is determined by the following formula: in, ρ i ( t ) is an individual i The local density of people within a certain radius of the location, is the density influencing factor, For individuals i The free movement rate of f v ( T ) is the temperature influence factor, which represents the influence of temperature on personnel evacuation: ， in, For individuals i The maximum achievable movement rate in the corresponding posture; For individuals i The free movement rate of , , and are the temperatures at the current location, when the individual feels uncomfortable, when the individual is injured, and when the individual dies; The individual j For individuals i The force Determined by the following formula: ， in, and are the anisotropy coefficients, respectively representing the forces weights for different directions and speed differences; ， ， In the formula, A, B, K, k are constants representing the strength of social force, the strength of the range of social force, the strength of reaction force, and the strength of friction force, respectively. Indicates that from individual j Centered on the individual i The normalized vector to the center, g is the Heaviside function, which is used to determine whether there is physical contact between individuals. Represents the direction of the sliding friction force generated by body contact, which is a tangential normalized vector, that is, The direction is perpendicular to the individual i The angle between the velocity directions is greater than 90°. Representing an individual i With individuals j The distance between The environment W is for individuals i The force Determined by the following formula: ， ， in, Representing an individual i The width of the body from its center to the border W The difference in the distance between the walls. A value greater than 0 indicates that there is physical contact and potential compression between the individual and the wall, and a value less than 0 indicates that there is no physical contact between the individual and the wall. Indicated by the boundary Towards individuals i Normalized vector to the center, t iW Represents the direction of the friction force generated by the contact between the individual and the wall, which is a tangential normalized vector and Vertically and with the individual i The angle between the velocity directions is greater than 90°; Physical force of fire on individuals Determined by the following formula: ， in, and are all constants, reflecting the individual i the desired degree of separation from ignition sources and the temperature range affected; is the ambient temperature, Is an individual i The temperature felt in the head, Represents the fire source center pointing to the individual i The unit vector of the head, for and The angle of The unit vector representing the vertical exit; The psychological impact of fire on individuals Determined by the following formula: ， Among them, sgn is the sign function, the constant , B y Represents the fire source to the individual i The influence distance of psychological force and the influence coefficient of evacuation path affected by fire source on psychological force, and Represent the expected intensity of individuals staying away from and avoiding fire sources, is the radius of the fire source; Representing an individual i Distance from the fire source; Represents an individual i The distance between the head and the center of the fire is Projection distance in direction; represents the unit vector of the parallel exit, n iH To point from the center of the fire to the individual i The unit vector of the head, t iH is perpendicular to n iH The unit vector of the fire source is determined by the distance from the personnel to the exit directly and the distance from the personnel to the exit bypassing the fire source.

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