CN111651872A - Nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation - Google Patents

Nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation Download PDF

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CN111651872A
CN111651872A CN202010442231.3A CN202010442231A CN111651872A CN 111651872 A CN111651872 A CN 111651872A CN 202010442231 A CN202010442231 A CN 202010442231A CN 111651872 A CN111651872 A CN 111651872A
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卓俊
黄流兴
牛胜利
朱金辉
商鹏
李夏至
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Northwest Institute of Nuclear Technology
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Abstract

The invention provides a radioactive contamination numerical simulation method based on a gas-solid two-phase simulation method, which solves the problem that the gas-solid separation effect and turbulent diffusion effect are unreasonably described in the conventional simulation method for atmospheric transport and settlement of radioactive smoke cloud particles generated by nuclear explosion. The method comprises the following steps: 1) setting a contamination distribution calculation area according to the explosion equivalent and the average wind speed, and setting the total number of simulated particles and recording the grid resolution; 2) establishing initial spatial distribution of nuclear explosion radioactive particles by adopting a stable smoke cloud model; 3) calculating turbulence parameters; 4) simulating the atmospheric transportation and sedimentation process of certain radioactive particles in the stable smoke cloud by using a gas-solid two-phase flow method until the radioactive particles fall to the ground or escape from a calculation boundary, wherein the gas-solid two-phase flow method adopts a time propulsion principle; 5) and counting the distribution result of the surface contamination according to all the calculated radioactive particle sedimentation positions.

Description

Nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation
Technical Field
The invention relates to a nuclear explosion radioactive contamination prediction simulation technology, in particular to a nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation.
Background
The nuclear explosion effect mainly comprises shock wave, light radiation, early nuclear radiation, nuclear electromagnetic pulse and radioactive contamination effect. The radioactive contamination is one of the important killing factors of nuclear explosion, and has the characteristics of long duration and wide action range. During ground nuclear explosion, a large amount of melted and vaporized soil substances are involved in the smoke cloud, so that a large amount of particles with larger diameters exist in the smoke cloud, the sedimentation of the larger radioactive particles mainly occurs in a local area close to an explosion point, serious radioactive contamination can be formed in a range of hundreds of kilometers in the wind direction below the explosion point, the radiation influence of the contamination can last for weeks or even months after the explosion, and the radiation damage can be caused to people in the contamination range.
During atmospheric nuclear test in the sixty-seven decades of the last century, a great deal of test observation is carried out on nuclear explosion radioactive contamination settlement, and a series of radioactive contamination prediction calculation models are formed. For example, the DELFIC (Defence Land flood interference code) program developed by the national Defense Agency (DNA) (norm H G published in 1979 reports "Atmospheric Science Associates" and "Delfic: Department of Defence flood Prediction System Volume II-Initial conditions") and the SEER (simplified Research Institute, SRI) series program developed by Stanford Research Institute (SRI) (Lee H et al published in 1972 US Defense report AD-754144 and "SEER II: A new mass assessment model") were developed by the national Defense Agency (DeFed laboratory) and were predicted by the cloud Atmospheric diffusion process and the computational limitations of Atmospheric diffusion models, and the Prediction of the actual deposition of smoke was made when these models were predicted by the cloud model.
In recent decades, with the development of computer computing power and atmospheric science, conditions are created for establishing a more reasonable computing model and researching the atmospheric transportation and sedimentation process of nuclear explosion radioactive smoke cloud. In recent years, the United States has developed HPAC (Hazard Prediction and Assessment capability) programs for the nuclear biochemical threats that the United States faces, including the programs for predicting radioactive contamination (Chancellor R W published in 2005, "A Complex of Hazardous Prediction and Assessment Capabilities (HPAC) software-site reactions to a sample of localized data from the regulated signatures in the linked United States"). There is literature (Moroz B E et al, published in Health Physics journal, volume 99, 2010, page 2, 252, "Predictions of Dispersion and placement of Falloutfree Nuclear Testing using the NOAA-HYSPLIT Metalogical Model") that studies atmospheric transport and sedimentation processes of radioactive smoke clouds using a Hybrid Single-Particle Lagrangian Integrated Tracjector calculation; there is also literature (Miller A D published in 2011 Master's paper, "A compliance in the access of mapping nuclear floors using HPAC, HYSPLIT, DELFIC FPT and an AFIT Fortran95 floor deposition code") comparing the effects of four different atmospheric transport models, HPAC, HYSPLIT and DELFIC, on the contamination distribution.
In the model, when the atmospheric transport process of the smoke cloud is calculated, only the difference of the sedimentation speeds of the smoke cloud particles with different particle sizes at the gravity terminal in the vertical direction is considered, the mass inertia effect of the smoke cloud particles is neglected in the horizontal direction, the smoke cloud particles are regarded as completely passive particles moving along with the wind, and the atmospheric diffusion behavior of the smoke cloud particles is calculated approximately by adopting a passive particle atmospheric diffusion calculation model moving along with the air flow. In fact, the particles with different particle sizes have completely different motion characteristics in the atmosphere, and the particles with very small particle sizes have small inertia effect and can completely move along with the airflow; the movement speed change of the particles with larger particle size in the wind field generally lags behind the speed change of the wind field, and obvious gas-solid separation effect can be generated.
Disclosure of Invention
The invention provides a radioactive contamination numerical simulation method based on a gas-solid two-phase simulation method, aiming at solving the technical problem that the gas-solid separation effect and the turbulent flow diffusion effect are unreasonably described in the existing simulation method for atmospheric transport and settlement of radioactive smoke cloud particles in nuclear explosion.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation is characterized in that: the method comprises the following steps:
1) computing condition initialization processing
Setting initialization conditions, wherein the initialization conditions comprise calculation condition parameters, meteorological parameters and explosion condition parameters; the calculation condition parameters comprise the total number N of simulated particles, the calculation interval of radioactive particles and the spatial resolution of a recording grid; the meteorological parameters comprise wind speeds and boundary layer thicknesses H at different heightsbAnd underlying surface roughness r0The explosion condition parameters comprise an explosion equivalent W, a fission share η and a core explosion height h;
2) stable smoke cloud computing
2.1) simplifying the stable smoke cloud formed at the smoke cloud lifting termination moment into a cylinder combination of an upper smoke cloud column and a lower smoke cloud column, and calculating the characteristic parameters of the stable smoke cloud according to the explosion condition parameters set in the step 1); the characteristic parameters comprise the top height of the smoke cloud column, the bottom height of the smoke cloud column, the diameter of the smoke cloud column and the stability time of the smoke cloud, and are specifically calculated as follows:
the top height of the smoke column is as follows: hTM＝4.5W0.22+h；
The height of the bottom of the smoke cloud column is as follows: hBM＝4.5W0.22-2W0.2+h；
The stabilizing time is as follows: t isM＝648W-0.117；
Diameter of the smoke column:
Figure BDA0002504395290000031
diameter of dust column: dS＝0.4DCM；
2.2) if the particles in the stable smoke cloud are spherical particles with the particle size distribution satisfying the log-normal distribution f (d) and are uniformly distributed in the stable smoke cloud, the particle size distribution function f (d) of the stable smoke cloud particles is as follows:
Figure BDA0002504395290000032
wherein d is50And s are the median diameter and standard deviation of the distribution, respectively;
3) turbulence parameter calculation
Reading in meteorological parameters, and calculating a boundary layer turbulence diffusion parameter sigma and a Lagrange time scale T by using atmospheric science and a planet boundary layer theoryL；
4) Simulating radioactive particle transport and sedimentation process
Simulating the atmospheric transportation and sedimentation process of certain radioactive particles in the stable smoke cloud by using a gas-solid two-phase flow method until the radioactive particles fall to the ground or escape from a calculation boundary, wherein the gas-solid two-phase flow method adopts a time propulsion principle, and the time step length is delta t; the method comprises the following specific steps:
4.1) sampling the initial position X (t) of the particles according to the spatial extent of the stable cloud0) And sampling the particle diameter d according to a particle size distribution function f (d)p；
4.2) calculating the particle position, the movement speed and the stress condition of the sampled particles at the end of each time step by using a gas-solid two-phase flow method based on a double Lagrange model until the particles fall to the ground or are separated from a side boundary;
5) predicting the distribution of surface contamination:
selecting the next radioactive particle, and repeating the step 4) until the number of the calculated particles reaches the total number N of the simulated particles; and counting the distribution result of the surface contamination according to all the calculated radioactive particle sedimentation positions.
Further, the step 3) is specifically as follows: reading in meteorological parameters, and calculating a boundary layer turbulence diffusion parameter sigma and a Lagrange time scale T by using atmospheric science and a planet boundary layer theoryLIf the atmospheric stability is neutral, then σ and TLThe component in downwind direction is σ1And TL1The component in the horizontal crosswind direction is σ2And TL2Component σ in the vertical direction3And TL3The calculation formula is as follows:
σ1＝2.3×u*
σ2＝2.0×u*
Figure BDA0002504395290000041
Figure BDA0002504395290000042
wherein z is the height of the particulate matter from the ground;
u*is the friction speed;
Figure BDA0002504395290000043
wherein κ is a karman constant; u. of0Is the ground wind speed, z0Corresponding to the anemometric height.
Further, the step 4.1) is specifically as follows: sampling particle initial position X (t) according to space range of stable smoke cloud0) And sampling the particle diameter d according to a function f (d) of the particle size distribution of the stable smoke cloud particlesp(ii) a The initial time t of atmospheric transport of the particles0For the time T of cloud stabilityMI.e. t0＝TM。
Further, the step 4.2) is specifically as follows:
4.2.1) calculating the stress F (t) of the particles according to the motion state of the particles and the micro air mass where the particles are positioned at the initial time t of each step, wherein F (t) is gravity G and viscous resistance FD(t) the resultant force;
G＝mpg
Figure BDA0002504395290000044
wherein, Vp(t) is the particle movement speed; vg(t) is the micro-air mass movement speed; g is the acceleration of gravity; rhogIs the air density; coefficient of resistance
Figure BDA0002504395290000051
RepIs the reynolds number of the particles,f is a correction factor;
4.2.2) depending on the position X of the particles at the initial instant t of each stepp(t) and the speed of movement Vp(t) calculating the position X of the particle after a time interval Deltatp(t+Δt)：
Xp(t+Δt)＝Xp(t)+Vp(t)Δt
According to the stress condition F (t) of the particles at the initial moment of each step, calculating the movement speed V of the particles after the time interval delta tp(t+Δt)：
Vp(t+Δt)＝Vp(t)+ΔVp(t)
Wherein the velocity change amount DeltaV of the particlesp(t) is calculated as follows:
Figure BDA0002504395290000052
in the formula (I), the compound is shown in the specification,
Figure BDA0002504395290000053
is the mass of the particles, ppIs the density of the smoke cloud particles;
4.2.3) calculating the position X of the micro-air mass wrapped around the particles at the moment t after the time interval delta tg(t+Δt)：
Xg(t+Δt)＝Xg(t)+Vg(t)Δt+V′g(t)Δt
X due to the gas mass enveloping the particles at time tg(t)＝Xp(t)；
In formula (II) V'g(t) is turbulent pulsating speed, and the components of the turbulent pulsating speed in the directions of three coordinates of x, y and z are recorded as u ', v ' and w ';
the turbulent pulsating speed of the same micro-air mass at different moments follows the Markov assumption, i.e.
Figure BDA0002504395290000054
Wherein ξ is a normally distributed random number, Ru，Rv，RwThree coordinates of x, y and z respectivelyThe Lagrange autocorrelation function of the direction is calculated according to the following formula:
Figure BDA0002504395290000061
wherein σu、σv、σwTurbulent diffusion parameters in the y direction and the z direction; t isLu、TLv、TLwLagrange time scale of x, y, zu、σv、σwAnd TLu、TLv、TLwFrom sigma by coordinate transformation1，σ2，σ3And TL1，TL2，TL3Calculating to obtain;
calculating the turbulent flow velocity of the micro air mass around the particles at the t + delta t moment by using Euler correlation of the turbulent flow velocity at different positions at the same moment:
Figure BDA0002504395290000062
wherein; rE,u、RE,vAnd RE,wEuler correlation coefficient of x, y, x coordinate direction respectively
Figure BDA0002504395290000063
In the formula:
Figure BDA0002504395290000064
Figure BDA0002504395290000065
in the formula: i represents any component of u, v and w;
4.2.4) position X of the particle at time t + Deltatp(t + Δ t), moving speed Vp(t + delta t) and the turbulent flow speed of the micro air mass around the particles are taken as the motion state of the next initial moment, and the steps 3.3.1) to 3.3.3) are repeated untilAnd calculating the motion trail of the particles in the whole atmospheric transportation and sedimentation process when the particles fall to the ground or leave the side boundary.
Further, in step 2.2), d50＝0.407μm，s＝4.0；
In step 4.2.1), when Rep<When 1, f is 1; when RepWhen f is more than or equal to 1, f can be expressed as
Figure BDA0002504395290000073
Meanwhile, the invention also provides another prediction method of nuclear explosion radioactive contamination based on gas-solid two-phase flow simulation, which is characterized in that: the method comprises the following steps:
1) computing condition initialization processing
Setting initialization conditions, wherein the initialization conditions comprise calculation condition parameters, meteorological parameters and explosion condition parameters; the calculation condition parameters comprise the total number N of simulated particles, the calculation interval of radioactive particles and the spatial resolution of a recording grid; the meteorological parameters comprise wind speeds and boundary layer thicknesses H at different heightsbAnd underlying surface roughness r0The explosion condition parameters comprise an explosion equivalent W, a fission share η and a core explosion height h;
2) stable smoke cloud computing
2.1) simplifying the stable smoke cloud formed at the smoke cloud lifting termination moment into a cylinder combination of an upper smoke cloud column and a lower smoke cloud column, and calculating the characteristic parameters of the stable smoke cloud according to the explosion condition parameters set in the step 1); the characteristic parameters comprise the top height of the smoke cloud column, the bottom height of the smoke cloud column, the diameter of the smoke cloud column and the stability time of the smoke cloud, and are specifically calculated as follows:
the top height of the smoke column is as follows: hTM＝4.5W0.22+h；
The height of the bottom of the smoke cloud column is as follows: hBM＝4.5W0.22-2W0.2+h；
The stabilizing time is as follows: t isM＝648W-0.117；
Diameter of the smoke column:
Figure BDA0002504395290000071
diameter of dust column: dS＝0.4DCM；
2.2) if the particles in the stable smoke cloud are spherical particles with the particle size distribution satisfying the log-normal distribution f (d) and are uniformly distributed in the stable smoke cloud, the particle size distribution function f (d) of the stable smoke cloud particles is as follows:
Figure BDA0002504395290000072
wherein d is50And s are the median diameter and standard deviation of the distribution, respectively;
3) simulating radioactive particle transport and sedimentation process
Simulating the atmospheric transportation and sedimentation process of certain radioactive particles in the stable smoke cloud by using a gas-solid two-phase flow method until the radioactive particles fall to the ground or escape from a calculation boundary, wherein the gas-solid two-phase flow method adopts a time propulsion principle, and the time step length is delta t; the method comprises the following specific steps:
3.1) reading in meteorological parameters and calculating a boundary layer turbulence diffusion parameter sigma and a Lagrange time scale T by using atmospheric science and a planet boundary layer theoryL；
3.2) sampling the initial position X (t) of the particles according to the spatial range of the stable smoke cloud0) And sampling the particle diameter d according to a particle size distribution functionp；
3.3) calculating the particle position, the movement speed and the stress condition of the sampled particles at the end of each time step by using a gas-solid two-phase flow method based on a double Lagrange model until the particles fall to the ground or are separated from a side boundary;
4) predicting the distribution of surface contamination:
selecting the next radioactive particle, and repeating the step 3) until the number of the calculated particles reaches the total number N of the simulated particles; and counting the distribution result of the surface contamination according to all the calculated radioactive particle sedimentation positions.
Further, the step 3.1) is specifically as follows: reading in meteorological parameters, and calculating boundary layer turbulence diffusion parameter sigma and Lagrange time scale by atmospheric science and planet boundary layer theoryTLIf the atmospheric stability is neutral, then σ and TLThe component in downwind direction is σ1And TL1The component in the horizontal crosswind direction is σ2And TL2Component σ in the vertical direction3And TL3The calculation formula is as follows:
σ1＝2.3×u*
σ2＝2.0×u*
Figure BDA0002504395290000081
Figure BDA0002504395290000082
wherein z is the height of the particulate matter from the ground;
u*is the friction speed;
Figure BDA0002504395290000083
wherein κ is a karman constant; u. of0Is the ground wind speed, z0Is the corresponding wind height;
the step 3.2) is specifically as follows: sampling particle initial position X (t) according to space range of stable smoke cloud0) And sampling the particle diameter d according to a function f (d) of the particle size distribution of the stable smoke cloud particlesp(ii) a The initial time t of atmospheric transport of the particles0For the time T of cloud stabilityMI.e. t0＝TM。
Further, step 3.3) is specifically:
3.3.1) calculating the stress F (t) of the particles according to the motion state of the particles and the micro air mass where the particles are positioned at the initial time t of each step, wherein F (t) is gravity G and viscous resistance FD(t) the resultant force;
G＝mpg
Figure BDA0002504395290000091
wherein, Vp(t)Is the particle movement speed; vg(t) is the micro-air mass movement speed; g is the acceleration of gravity; rhogIs the air density; coefficient of resistance
Figure BDA0002504395290000092
RepIs the particle Reynolds number, f is the correction factor;
3.3.2) depending on the position X of the particles at the initial moment t of each stepp(t) and the speed of movement Vp(t) calculating the position X of the particle after a time interval Deltatp(t+Δt)：
Xp(t+Δt)＝Xp(t)+Vp(t)Δt
According to the stress condition F (t) of the particles at the initial moment of each step, calculating the movement speed V of the particles after the time interval delta tp(t+Δt)：
Vp(t+Δt)＝Vp(t)+ΔVp(t)
Wherein the velocity change amount DeltaV of the particlesp(t) is calculated as follows:
Figure BDA0002504395290000093
in the formula (I), the compound is shown in the specification,
Figure BDA0002504395290000094
is the mass of the particles, ppIs the density of the smoke cloud particles;
3.3.3) calculating the position X of the micro-air mass wrapped around the particles at the moment t after a time interval delta tg(t+Δt)：
Xg(t+Δt)＝Xg(t)+Vg(t)Δt+V′g(t)Δt
X due to the gas mass enveloping the particles at time tg(t)＝Xp(t)；
In formula (II) V'g(t) is turbulent pulsating speed, and the components of the turbulent pulsating speed in the directions of three coordinates of x, y and z are recorded as u ', v ' and w ';
the turbulent pulsating speed of the same micro-air mass at different moments follows the Markov assumption, i.e.
Figure BDA0002504395290000101
Wherein ξ is a normally distributed random number, Ru，Rv，RwThe lagrangian autocorrelation function of the three coordinate directions of x, y and z respectively has the following calculation formula:
Figure BDA0002504395290000102
wherein σu、σv、σwTurbulent diffusion parameters in the y direction and the z direction; t isLu、TLv、TLwLagrange time scale of x, y, zu、σv、σwAnd TLu、TLv、TLwFrom sigma by coordinate transformation1，σ2，σ3And TL1，TL2，TL3Calculating to obtain;
calculating the turbulent flow velocity of the micro air mass around the particles at the t + delta t moment by using Euler correlation of the turbulent flow velocity at different positions at the same moment:
Figure BDA0002504395290000103
wherein; rE,u、RE,vAnd RE,wEuler correlation coefficient of x, y, x coordinate direction respectively
Figure BDA0002504395290000104
In the formula:
Figure BDA0002504395290000105
Figure BDA0002504395290000111
in the formula: i represents any component of u, v and w;
3.3.4) position X of the particle at time t + Deltatp(t + Δ t), moving speed Vp(t + delta t) and the turbulent flow speed of the micro air mass around the particles are used as the motion state of the next initial moment, and the steps 3.3.1) -3.3.3) are repeated until the particles fall to the ground or leave the side boundary, and the motion trail of the particles in the whole atmospheric transportation and sedimentation process is calculated.
Further, in step 2.2), d50＝0.407μm，s＝4.0。
Further, in step 3.3.1), when Rep<When 1, f is 1; when RepWhen f is more than or equal to 1, f can be expressed as
Figure BDA0002504395290000112
Compared with the prior art, the invention has the advantages that:
1. the method adopts a gas-solid two-phase flow method to simulate the atmospheric transportation process of the radioactive particles of the nuclear explosion, realizes the tracking simulation of the atmospheric transportation process of the radioactive particles with different particle sizes in the dilute phase flow, can reasonably reflect the gas-solid separation physical phenomenon of the particles in the atmospheric diffusion process, combines a nuclear explosion smoke cloud source item calculation model (stabilizing smoke cloud characteristic parameters and stabilizing smoke cloud particle size distribution functions), considers the influence of turbulence on the radioactive particles with different particle sizes in the atmospheric transportation process, and realizes the three-dimensional calculation of the atmospheric transportation and sedimentation process of the radioactive particles of the near-earth nuclear explosion.
2. The prediction method can give out the ground surface contamination distribution of the smoke cloud particles and also can give out the radioactive concentration distribution of the smoke cloud operating in the air.
3. The method can calculate the movement and sedimentation behaviors of radioactive smoke cloud particles with different particle sizes in the process of atmospheric transportation in the near-earth nuclear explosion, give out the ground distribution and the dose field of radioactive contamination, and play an important role in evaluating the possible irradiation hazard to the public in the contaminated area after the nuclear explosion.
4. The particulate matter gas-solid two-phase flow simulation method can also be used for calculation research of radioactive particulate matter diffusion distribution caused by nuclear power station accidents and the like, and has important significance for formulating emergency protection measures after the accidents.
Drawings
FIG. 1 is a flow chart of a method for predicting radioactive contamination of nuclear explosion based on gas-solid two-phase flow simulation according to the present invention;
FIG. 2 is a simplified model diagram of a stable smoke cloud in the nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation;
FIG. 3 is a schematic diagram of a calculation model of gas-solid two-phase flow for atmospheric transport of particulate matter in the method for predicting radioactive contamination of nuclear explosion based on gas-solid two-phase flow simulation of the present invention;
FIG. 4 is a movement track of 50 μm and 500 μm smoke cloud particles in the atmospheric transportation process in the nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation of the present invention; wherein a is 50 μm, and b is 500 μm;
FIG. 5 is a comparison between the calculation result of radioactive contamination distribution and the actual measurement structure in the method for predicting nuclear explosion radioactive contamination based on gas-solid two-phase flow simulation according to the present invention; wherein, a is the calculation result, and b is the actual measurement result.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
A nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation comprises the following steps:
1) setting a contamination distribution calculation area according to the explosion equivalent and the average wind speed, and setting the total number of simulated particles and recording the space-time resolution of a grid according to the requirement of a user on the precision of a calculation result;
2) establishing initial spatial distribution of nuclear explosion radioactive particles by adopting a stable smoke cloud model, and giving particle size distribution by adopting a lognormal distribution model;
3) calculating turbulence parameters under different atmospheric stability conditions according to an atmospheric boundary layer dynamics theory in atmospheric science;
4) calculating the movement of the particles and micro air mass around the particles by adopting a gas-solid two-phase flow method, wherein the movement of the micro air mass is simulated by adopting a random walk method; establishing a Newtonian dynamic control equation for describing the movement of the particles according to the stress condition of the particles in the air flow, wherein the influence of gravity and drag force on the movement of the particles is mainly considered in the model;
5) and (4) counting the distribution of the radioactive contamination on the ground surface according to the final landing positions of all the particles.
The method comprises the steps of firstly, calculating the thermodynamic rising process of the smoke cloud according to initialization conditions, and giving particle source parameters such as space distribution, speed distribution and particle size distribution of radioactive particles in the smoke cloud; then, according to the initial state of the radioactive particles obtained by sampling, simulating the movement process of the particles in the atmosphere by using a gas-solid two-phase flow method until the particles fall to the ground or escape from the calculation boundary; the calculation results such as the distribution of surface contamination can be obtained through counting the motion process of a large number of radioactive particles repeatedly. The invention can reasonably simulate the movement rule of particles with different particle diameters in the atmosphere, and the coincidence of the calculated result and the actual measurement result is higher.
Example one
Setting the explosion equivalent W to 1.65 kt; the fission fraction is 1; the ground clearance h of the center of the explosion point is 3 m; density of smoke cloud particles rhopIs 2.6 × 103kg/m3(ii) a Wind speeds at different heights are shown in table 1; thickness H of boundary layerbIs 1500 m; the length L of the molinin is-10; roughness of the earth's surface r00.3m, a calculation interval of-3000-48000 for radioactive particles, a calculation interval of-3000-28000 for unit m, a spatial resolution of a recording grid of 100m × 100m, a calculation truncation time of 24hr, and a simulated particle number N of 107A plurality of;
TABLE 1
Figure BDA0002504395290000131
The flowchart of the prediction method of the present embodiment is shown in fig. 1, and includes the following steps:
1) computing condition initialization processing
1.1) carrying out initialization setting on parameters of calculation conditions such as the number of simulated particles, truncation time, calculation range and grid division;
1.2) reading weather parameters required by calculation, and calculating the total mass of the molten solid and the initial conditions of smoke cloud according to explosion condition parameters such as explosion equivalent, explosion height, fission share and the like;
2) smoke cloud rising computing
The radioactive cloud formed by the nuclear explosion will rise and expand rapidly under the action of heat and will continuously entrain large amounts of ambient material. The termination time of the smoke cloud lifting is called as the smoke cloud stabilization time, the appearance of the stabilized smoke cloud is like mushroom, and in order to simplify the calculation, the geometric shape of the stabilized smoke cloud is simplified into a combination of two cylinders of an upper smoke cloud column and a lower dust column, as shown in fig. 2.
2.1) calculating stable smoke cloud characteristic parameters according to the explosion condition parameters set in the step 1); the characteristic parameters comprise the top height of the smoke cloud column, the bottom height of the smoke cloud column, the diameter of the dust column and the stability time of the smoke cloud, the stability time is the time required from explosion to stable smoke cloud formation, and the specific calculation is as follows:
the top height of the smoke column is as follows: hTM＝4.5W0.22+h；
The height of the bottom of the smoke cloud column is as follows: hBM＝4.5W0.22-2W0.2+h；
The stabilizing time is as follows: t isM＝648W-0.117；
Diameter of the smoke column:
Figure BDA0002504395290000132
diameter of dust column: dS＝0.4DCM；
2.2) assuming that the particles of the smoke cloud are spherical and the particle size distribution thereof satisfies the log-normal distribution, the stable smoke cloud particle size distribution function f (d) is:
Figure BDA0002504395290000141
wherein d is50And s is the median diameter (i.e., mean diameter) and standard deviation of the distribution, respectively. When the near-surface explosion occurs, take d50＝0.407μm，s＝4.0。
3) Turbulence parameter calculation
The particles move under the action of the atmospheric wind field, corresponding meteorological parameters are obtained from meteorological data according to the positions and time of the particles, and boundary layer turbulence diffusion parameters sigma and Lagrange time scale T are calculated by using atmospheric science and planet boundary layer theoryLThe specific calculation method is closely related to the stability of the atmosphere; when the atmospheric stability is neutral, then σ and TLThe component in downwind direction is σ1And TL1The component in the horizontal crosswind direction is σ2And TL2Component σ in the vertical direction3And TL3The calculation formula is as follows:
σ1＝2.3×u*
σ2＝2.0×u*
Figure BDA0002504395290000142
Figure BDA0002504395290000143
wherein z is the height above the ground; l is the length of the molinin; u. of*Is the speed of friction
Figure BDA0002504395290000144
Since the atmospheric stability is neutral, then
Figure BDA0002504395290000145
Wherein κ is a karman constant; c. CpAir isobaric heat capacity; u. of0Is z0Wind speed in altitude, generally using z0The observed wind speed value at 10m height. Other calculation methods under stability conditions can be given by reference to the existing literature.
4) Simulating the atmospheric transport and sedimentation process of certain radioactive particles in the stable smoke cloud by using a gas-solid two-phase flow method until the radioactive particles fall to the ground or escape from a calculation boundary; the time advancing principle is adopted in the calculation, and the time step is delta t; the method comprises the following specific steps:
4.1) sampling the initial position X (t) of the particles according to the spatial range of the stable smoke cloud, assuming that the particles are uniformly distributed in the stable smoke cloud0) And sampling the particle diameter d according to a particle size distribution function f (d)p(ii) a Initial time t of atmospheric transport of particles0For the time T of cloud stabilityMI.e. t0＝TM；
4.2) calculating the position, the movement speed and the stress condition of the particles at the end of each time step of the sampled particles by a gas-solid two-phase flow method based on a double Lagrange model until the particles fall to the ground or are separated from the side boundary. The particle motion is calculated by a gas-solid two-phase flow method based on a double Lagrange model, and the calculation model is shown in figure 3. Assuming that the position of the particulate matter is O at the initial moment, after a period of time interval delta t, the position S of the particulate matter can be calculated according to the stress condition of the particulate matter, meanwhile, the position F of an air mass around the particulate matter is calculated by adopting a random walk method, then, the fluid motion state at the position S can be calculated from the fluid state at the position F by utilizing the Euler correlation, and the stress condition of the particulate matter at the position S can be calculated after the fluid motion state at the position S is known, so that the particle position at the next time step can be continuously calculated. By analogy, the motion trail of the whole atmospheric transportation and sedimentation process of the particles can be calculated. The step 4.2) is specifically as follows:
4.2.1) calculating the stress F of the particles according to the motion state of the particles and the micro air mass of the particles at the initial time t of each stepD(t); the particles are mainly subjected to gravity G and viscous resistance F when moving in the air flowDThe function of (1);
G＝mpg
Figure BDA0002504395290000151
wherein, Vp(t) is the particle movement speed; vg(t) is the micro-air mass movement speed; g is the acceleration of gravity; rhogIs the air density; coefficient of resistance
Figure BDA0002504395290000152
RepIs the particle Reynolds number, and f is the correction factor. When Rep<When 1, the flow is Stokes flow, and when f is 1; when RepWhen f is more than or equal to 1, f can be expressed as
Figure BDA0002504395290000153
4.2.2) depending on the position X of the particles at the initial instant t of each stepp(t) and the speed of movement Vp(t) calculating the position X of the particle after a time interval Deltatp(t+Δt)：
Xp(t+Δt)＝Xp(t)+Vp(t)Δt
According to the stress condition F (t) of the particles at the initial moment of each step, calculating the movement speed V of the particles after the time interval delta tp(t+Δt)：
Vp(t+Δt)＝Vp(t)+ΔVp(t)
Wherein the velocity change amount DeltaV of the particlesp(t) is given by solving the newtonian force equation for the particle:
Figure BDA0002504395290000161
in the formula (I), the compound is shown in the specification,
Figure BDA0002504395290000162
is the mass of the particles;
4.2.3) calculating the position X of the micro-air mass wrapped around the particles at the moment t after the time interval delta tg(t+Δt)：
Xg(t+Δt)＝Xg(t)+Vg(t)Δt+V′g(t)Δt
Since the air mass envelops the particles at time t, the two positions are the same, i.e. both are
Xg(t)＝Xp(t)
In the formula, the components of the air mass in the three directions of x, y and z are recorded as u, v and w;
V′g(t) is the turbulent pulsating velocity, whose components in the three coordinate directions are denoted u ', v ', w '. The average wind speeds at different positions and moments are interpolated from the read-in meteorological data.
The turbulent pulsating velocities of the same micro-air mass at different moments follow the Markov (Markov) assumption (the motion state at time t + Deltat is only related to the motion state at time t), i.e.
Figure BDA0002504395290000163
In the formula, the second term on the right represents the random part of the velocity fluctuation amount, ξ is a random number conforming to the normal distribution (average value is 0, standard deviation is 1); Ru，Rv，RwThe Lagrange autocorrelation function of the three coordinate directions of x, y and z respectively, and the calculation method comprises the following steps
Figure BDA0002504395290000164
Wherein, the turbulent diffusion parameter sigma of the x, y and z directionsu，σv，σwAnd lagrange time scale TLu，TLv，TLwFrom sigma by coordinate transformation1，σ2，σ3And TL1，TL2，TL3And (4) calculating.
Calculating the turbulent flow velocity of the micro air mass around the particles at the t + delta t moment by using Euler correlation of the turbulent flow velocity at different positions at the same moment:
Figure BDA0002504395290000171
wherein the content of the first and second substances,
Figure BDA0002504395290000172
RE,u、RE,vand RE,wEuler correlation coefficient of x, y, x coordinate direction respectively
Figure BDA0002504395290000173
Euler correlation time scale TECan be calculated from the following formula
Figure BDA0002504395290000174
Wherein the subscript i represents any of the u, v, w components.
4.2.4) position X of the particle at time t + Deltatp(t + Δ t), moving speed Vp(t + delta t) and the turbulent flow speed of the micro air mass around the particles are used as the motion state of the next initial moment, and the steps 4.2.1) -4.2.4 are repeated, so that the position, the motion state and the stress condition of the particles after the next time interval can be obtained continuously; calculating the motion trail of the particles in the whole atmospheric transportation and sedimentation process by analogy until the particles fall to the ground or are separated from the side boundary;
5) predicting the distribution of surface contamination:
selecting the next radioactive particle, and repeating the step 4) until the number of the calculated particles reaches the total number N of the simulated particles; and counting the distribution result of the surface contamination according to all the calculated radioactive particle sedimentation positions.
FIG. 4 shows the movement traces of two kinds of particles of 50 μm and 500 μm in atmospheric transportation, where the abscissa is the distance x in the downwind directionlThe ordinate is the height z. As can be seen from the figure, the motion trajectory of larger smoke cloud particles like 500 μm is similar to a parabolic motion under the influence of average wind speed and gravity only; while the 50 μm smaller smoke cloud particle can completely follow the flow field, the motion track of the smoke cloud particle obviously deviates from the parabolic motion under the influence of atmospheric turbulence. In fig. 5, a is the calculated ground contamination distribution, and b is the actual measurement result of the contamination distribution. As can be seen from fig. 5, the calculated contamination distribution map can better conform to the actually measured contour map on the characteristic parameters such as the hot line trend, the distribution area, the contamination area and the like.
Example two
Different from the first embodiment, the calculation of the turbulence parameters in the step 3) is shifted to the first step of simulating the transport and sedimentation process of the radioactive particles in the step 4), the turbulence parameters of the radioactive particles are calculated at each time step, the positions, the movement speeds and the stress conditions of the particles are calculated more accurately, and the contamination prediction precision of the radioactive particles is improved.
The above description is only for the purpose of describing the preferred embodiments of the present invention and does not limit the technical solutions of the present invention, and any known modifications made by those skilled in the art based on the main technical concepts of the present invention fall within the technical scope of the present invention.

Claims (10)

1. A nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation is characterized by comprising the following steps: the method comprises the following steps:
1) computing condition initialization processing
Setting initialization conditions, wherein the initialization conditions comprise calculation condition parameters, meteorological parameters and explosion condition parameters; the calculation condition parameters comprise the total number N of simulated particles, the calculation interval of radioactive particles and the spatial resolution of a recording grid; the meteorological parameters comprise wind speeds and boundary layer thicknesses H at different heightsbAnd underlying surface roughness r0The explosion condition parameters comprise an explosion equivalent W, a fission share η and a core explosion height h;
2) stable smoke cloud computing
2.1) simplifying the stable smoke cloud formed at the smoke cloud lifting termination moment into a cylinder combination of an upper smoke cloud column and a lower smoke cloud column, and calculating the characteristic parameters of the stable smoke cloud according to the explosion condition parameters set in the step 1); the characteristic parameters comprise the top height of the smoke cloud column, the bottom height of the smoke cloud column, the diameter of the smoke cloud column and the stability time of the smoke cloud, and are specifically calculated as follows:
the top height of the smoke column is as follows: hTM＝4.5W0.22+h；
The height of the bottom of the smoke cloud column is as follows: hBM＝4.5W0.22-2W0.2+h；
Stabilization
Diameter of the smoke column:
Figure FDA0002504395280000011
diameter of dust column: dS＝0.4DCM；
2.2) if the particles in the stable smoke cloud are spherical particles with the particle size distribution satisfying the log-normal distribution f (d) and are uniformly distributed in the stable smoke cloud, the particle size distribution function f (d) of the stable smoke cloud particles is as follows:
Figure FDA0002504395280000012
wherein d is50And s are the median diameter and standard deviation of the distribution, respectively;
3) turbulence parameter calculation
Reading in meteorological parameters, and calculating a boundary layer turbulence diffusion parameter sigma and a Lagrange time scale T by using atmospheric science and a planet boundary layer theoryL；
4) Simulating radioactive particle transport and sedimentation process
Simulating the atmospheric transportation and sedimentation process of certain radioactive particles in the stable smoke cloud by using a gas-solid two-phase flow method until the radioactive particles fall to the ground or escape from a calculation boundary, wherein the gas-solid two-phase flow method adopts a time propulsion principle, and the time step length is delta t; the method comprises the following specific steps:
4.1) sampling the initial position X (t) of the particles according to the spatial extent of the stable cloud0) And sampling the particle diameter d according to a particle size distribution function f (d)p；
4.2) calculating the particle position, the movement speed and the stress condition of the sampled particles at the end of each time step by using a gas-solid two-phase flow method based on a double Lagrange model until the particles fall to the ground or are separated from a side boundary;
5) predicting the distribution of surface contamination:
selecting the next radioactive particle, and repeating the step 4) until the number of the calculated particles reaches the total number N of the simulated particles; and counting the distribution result of the surface contamination according to all the calculated radioactive particle sedimentation positions.
2. The method for predicting the radioactive contamination of nuclear explosion based on gas-solid two-phase flow simulation of claim 1, wherein the method comprises the following steps:
the step 3) is specifically as follows: reading in meteorological parameters, and calculating a boundary layer turbulence diffusion parameter sigma and a Lagrange time scale T by using atmospheric science and a planet boundary layer theoryLIf the atmospheric stability is neutral, then σ and TLThe component in downwind direction is σ1And TL1The component in the horizontal crosswind direction is σ2And TL2Component σ in the vertical direction3And TL3The calculation formula is as follows:
σ1＝2.3×u*
σ2＝2.0×u*
Figure FDA0002504395280000021
Figure FDA0002504395280000022
wherein z is the height of the particulate matter from the ground;
u*is the friction speed;
Figure FDA0002504395280000023
wherein κ is a karman constant; u. of0Is the ground wind speed, z0Corresponding to the anemometric height.
3. The method for predicting the radioactive contamination of the nuclear explosion based on the gas-solid two-phase flow simulation of claim 2, wherein the step 4.1) is specifically as follows: sampling particle initial position X (t) according to space range of stable smoke cloud0) And sampling the particle diameter d according to a function f (d) of the particle size distribution of the stable smoke cloud particlesp(ii) a The initial time t of atmospheric transport of the particles0For the time T of cloud stabilityMI.e. t0＝TM。
4. The method for predicting the radioactive contamination of the nuclear explosion based on the gas-solid two-phase flow simulation of claim 3, wherein the step 4.2) is specifically as follows:
4.2.1) calculating the stress F (t) of the particles according to the motion state of the particles and the micro air mass where the particles are positioned at the initial time t of each step, wherein F (t) is gravity G and viscous resistance FD(t) the resultant force;
G＝mpg
Figure FDA0002504395280000031
wherein, Vp(t) is the particle movement speed; vg(t) is the micro-air mass movement speed; g is the acceleration of gravity; rhogIs the air density; coefficient of resistance
Figure FDA0002504395280000032
RepIs the particle Reynolds number, f is the correction factor;
4.2.2) depending on the position X of the particles at the initial instant t of each stepp(t) and the speed of movement Vp(t) calculating the position X of the particle after a time interval Deltatp(t+Δt)：
Xp(t+Δt)＝Xp(t)+Vp(t)Δt
According to the stress condition F (t) of the particles at the initial moment of each step, calculating the movement speed V of the particles after the time interval delta tp(t+Δt)：
Vp(t+Δt)＝Vp(t)+ΔVp(t)
Wherein the velocity change amount DeltaV of the particlesp(t) is calculated as follows:
Figure FDA0002504395280000033
in the formula (I), the compound is shown in the specification,
Figure FDA0002504395280000034
is the mass of the particles, ppIs the density of the smoke cloud particles;
4.2.3) calculating the position X of the micro-air mass wrapped around the particles at the moment t after the time interval delta tg(t+Δt)：
Xg(t+Δt)＝Xg(t)+Vg(t)Δt+V′g(t)Δt
X due to the gas mass enveloping the particles at time tg(t)＝Xp(t)；
In formula (II) V'g(t) is turbulent pulsating speed, and the components of the turbulent pulsating speed in the directions of three coordinates of x, y and z are recorded as u ', v ' and w ';
the turbulent pulsating speed of the same micro-air mass at different moments follows the Markov assumption, i.e.
Figure FDA0002504395280000041
Wherein ξ is a normally distributed random number, Ru，Rv，RwThe lagrangian autocorrelation function of the three coordinate directions of x, y and z respectively has the following calculation formula:
Figure FDA0002504395280000042
wherein σu、σv、σwTurbulent diffusion parameters in the y direction and the z direction; t isLu、TLv、TLwLagrange time scale of x, y, zu、σv、σwAnd TLu、TLv、TLwFrom sigma by coordinate transformation1，σ2，σ3And TL1，TL2，TL3Calculating to obtain;
calculating the turbulent flow velocity of the micro air mass around the particles at the t + delta t moment by using Euler correlation of the turbulent flow velocity at different positions at the same moment:
Figure FDA0002504395280000043
wherein; rE,u、RE,vAnd RE,wEuler correlation coefficient of x, y, x coordinate direction respectively
Figure FDA0002504395280000044
In the formula:
Figure FDA0002504395280000051
Figure FDA0002504395280000052
in the formula: i represents any component of u, v and w;
4.2.4) position X of the particle at time t + Deltatp(t + Δ t), moving speed Vp(t + delta t) and the turbulent flow speed of the micro air mass around the particles are used as the motion state of the next initial moment, and the steps 3.3.1) -3.3.3) are repeated until the particles fall to the ground or leave the side boundary, and the motion trail of the particles in the whole atmospheric transportation and sedimentation process is calculated.
5. The method for predicting the radioactive contamination of nuclear explosion based on gas-solid two-phase flow simulation of claim 4, wherein in the step 2.2), d is50＝0.407μm，s＝4.0；
In step 4.2.1), when Rep<When 1, f is 1; when RepWhen f is more than or equal to 1, f can be expressed as
Figure FDA0002504395280000053
6. A nuclear explosion radioactive contamination prediction method based on gas-solid two-phase flow simulation is characterized by comprising the following steps: the method comprises the following steps:
1) computing condition initialization processing
Setting initialization conditions, wherein the initialization conditions comprise calculation condition parameters,Meteorological parameters and explosion condition parameters; the calculation condition parameters comprise the total number N of simulated particles, the calculation interval of radioactive particles and the spatial resolution of a recording grid; the meteorological parameters comprise wind speeds and boundary layer thicknesses H at different heightsbAnd underlying surface roughness r0The explosion condition parameters comprise an explosion equivalent W, a fission share η and a core explosion height h;
2) stable smoke cloud computing
2.1) simplifying the stable smoke cloud formed at the smoke cloud lifting termination moment into a cylinder combination of an upper smoke cloud column and a lower smoke cloud column, and calculating the characteristic parameters of the stable smoke cloud according to the explosion condition parameters set in the step 1); the characteristic parameters comprise the top height of the smoke cloud column, the bottom height of the smoke cloud column, the diameter of the smoke cloud column and the stability time of the smoke cloud, and are specifically calculated as follows:
the top height of the smoke column is as follows: hTM＝4.5W0.22+h；
The height of the bottom of the smoke cloud column is as follows: hBM＝4.5W0.22-2W0.2+h；
The stabilizing time is as follows: t isM＝648W-0.117；
Diameter of the smoke column:
Figure FDA0002504395280000061
diameter of dust column: dS＝0.4DCM；
2.2) if the particles in the stable smoke cloud are spherical particles with the particle size distribution satisfying the log-normal distribution f (d) and are uniformly distributed in the stable smoke cloud, the particle size distribution function f (d) of the stable smoke cloud particles is as follows:
Figure FDA0002504395280000062
wherein d is50And s are the median diameter and standard deviation of the distribution, respectively;
3) simulating radioactive particle transport and sedimentation process
Simulating the atmospheric transportation and sedimentation process of certain radioactive particles in the stable smoke cloud by using a gas-solid two-phase flow method until the radioactive particles fall to the ground or escape from a calculation boundary, wherein the gas-solid two-phase flow method adopts a time propulsion principle, and the time step length is delta t; the method comprises the following specific steps:
3.1) reading in meteorological parameters and calculating a boundary layer turbulence diffusion parameter sigma and a Lagrange time scale T by using atmospheric science and a planet boundary layer theoryL；
3.2) sampling the initial position X (t) of the particles according to the spatial range of the stable smoke cloud0) And sampling the particle diameter d according to a particle size distribution functionp；
3.3) calculating the particle position, the movement speed and the stress condition of the sampled particles at the end of each time step by using a gas-solid two-phase flow method based on a double Lagrange model until the particles fall to the ground or are separated from a side boundary;
4) predicting the distribution of surface contamination:
selecting the next radioactive particle, and repeating the step 3) until the number of the calculated particles reaches the total number N of the simulated particles; and counting the distribution result of the surface contamination according to all the calculated radioactive particle sedimentation positions.
7. The method for predicting the radioactive contamination of nuclear explosion based on gas-solid two-phase flow simulation of claim 6, wherein the method comprises the following steps:
the step 3.1) is specifically as follows: reading in meteorological parameters, and calculating a boundary layer turbulence diffusion parameter sigma and a Lagrange time scale T by using atmospheric science and a planet boundary layer theoryLIf the atmospheric stability is neutral, then σ and TLThe component in downwind direction is σ1And TL1The component in the horizontal crosswind direction is σ2And TL2Component σ in the vertical direction3And TL3The calculation formula is as follows:
σ1＝2.3×u*
σ2＝2.0×u*
Figure FDA0002504395280000071
Figure FDA0002504395280000072
wherein z is the height of the particulate matter from the ground;
u*in order to determine the speed of the friction,
Figure FDA0002504395280000073
wherein κ is a karman constant; u. of0Is the ground wind speed, z0Is the corresponding wind height;
the step 3.2) is specifically as follows: sampling particle initial position X (t) according to space range of stable smoke cloud0) And sampling the particle diameter d according to a function f (d) of the particle size distribution of the stable smoke cloud particlesp(ii) a The initial time t of atmospheric transport of the particles0For the time T of cloud stabilityMI.e. t0＝TM。
8. The method for predicting the radioactive contamination of the nuclear explosion based on the gas-solid two-phase flow simulation of claim 7, wherein the step 3.3) is specifically as follows:
3.3.1) calculating the stress F (t) of the particles according to the motion state of the particles and the micro air mass where the particles are positioned at the initial time t of each step, wherein F (t) is gravity G and viscous resistance FD(t) the resultant force;
G＝mpg
Figure FDA0002504395280000074
wherein, Vp(t) is the particle movement speed; vg(t) is the micro-air mass movement speed; g is the acceleration of gravity; rhogIs the air density; coefficient of resistance
Figure FDA0002504395280000075
RepIs the particle Reynolds number, f is the correction factor;
3.3.2) depending on the position X of the particles at the initial moment t of each stepp(t) and the speed of movement Vp(t) calculating the time between particlesPosition X after Δ tp(t+Δt)：
Xp(t+Δt)＝Xp(t)+Vp(t)Δt
According to the stress condition F (t) of the particles at the initial moment of each step, calculating the movement speed V of the particles after the time interval delta tp(t+Δt)：
Vp(t+Δt)＝Vp(t)+ΔVp(t)
Wherein the velocity change amount DeltaV of the particlesp(t) is calculated as follows:
Figure FDA0002504395280000081
in the formula (I), the compound is shown in the specification,
Figure FDA0002504395280000082
is the mass of the particles, ppIs the density of the smoke cloud particles;
3.3.3) calculating the position X of the micro-air mass wrapped around the particles at the moment t after a time interval delta tg(t+Δt)：
Xg(t+Δt)＝Xg(t)+Vg(t)Δt+V′g(t)Δt
X due to the gas mass enveloping the particles at time tg(t)＝Xp(t)；
In formula (II) V'g(t) is turbulent pulsating speed, and the components of the turbulent pulsating speed in the directions of three coordinates of x, y and z are recorded as u ', v ' and w ';
the turbulent pulsating speed of the same micro-air mass at different moments follows the Markov assumption, i.e.
Figure FDA0002504395280000083
Wherein ξ is a normally distributed random number, Ru，Rv，RwThe lagrangian autocorrelation function of the three coordinate directions of x, y and z respectively has the following calculation formula:
Figure FDA0002504395280000084
wherein σu、σv、σwTurbulent diffusion parameters in the y direction and the z direction; t isLu、TLv、TLwLagrange time scale of x, y, zu、σv、σwAnd TLu、TLv、TLwFrom sigma by coordinate transformation1，σ2，σ3And TL1，TL2，TL3Calculating to obtain;
calculating the turbulent flow velocity of the micro air mass around the particles at the t + delta t moment by using Euler correlation of the turbulent flow velocity at different positions at the same moment:
Figure FDA0002504395280000091
wherein; rE,u、RE,vAnd RE,wEuler correlation coefficient of x, y, x coordinate direction respectively
Figure FDA0002504395280000092
In the formula:
Figure FDA0002504395280000093
Figure FDA0002504395280000094
in the formula: i represents any component of u, v and w;
3.3.4) position X of the particle at time t + Deltatp(t + Δ t), moving speed Vp(t + delta t) and the turbulent flow speed of the micro air mass around the particles are used as the motion state of the next initial moment, and the steps 3.3.1) -3.3.3) are repeated until the particles fall to the ground or leave the side boundary, and the motion trail of the particles in the whole atmospheric transportation and sedimentation process is calculated.
9. The method for predicting the radioactive contamination of nuclear explosion based on gas-solid two-phase flow simulation of claim 8, wherein in the step 2.2), d is50＝0.407μm，s＝4.0。
10. The method for predicting the radioactive contamination of nuclear explosion based on gas-solid two-phase flow simulation of claim 9, wherein in the step 3.3.1), when Re is reachedp<When 1, f is 1; when RepWhen f is more than or equal to 1, f can be expressed as
Figure FDA0002504395280000095
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