CN103198227B - The Analysis of Electromagnetic Scattering method of hypervelocity flight target - Google Patents

Abstract

The invention discloses a kind of Analysis of Electromagnetic Scattering method of hypervelocity flight target.For being wrapped in the nonuniformity of plasma around hypervelocity flight target, have employed dignity integral Equation Methods to be analyzed, plasma equivalent relative dielectric constant processes close to the part of 1 as air, the region that equivalent relative dielectric constant is bigger uses Adaptive refinement to process, in order to reach required solving precision.Relative to the traditional method using uniform grid body subdivision plasma valve jacket, method in the present invention can greatly save calculating resource, simultaneously because the Green's function used in dignity integral equation is the Green's function in vacuum, the quick multistage sub-technology of multilamellar is used to further speed up and solves so that the present invention needs less calculating internal memory and calculating time for solving hypervelocity flight target scattering problem.

Description

Electromagnetic scattering analysis method for ultrahigh-speed flying target

Technical Field

The invention belongs to a rapid calculation technology of target electromagnetic scattering characteristics, and particularly relates to an electromagnetic scattering analysis method applied to an ultrahigh-speed flying target.

Background

Because the ultra-high speed flight target has a fast flight speed (more than 3 Mach) and a high flight height (more than 20 Km), the friction with air during flight generates aerodynamic heat of thousands of degrees centigrade, so that the surrounding air is ionized and exists in an ionic state. When the degree of ionization reaches a certain level, the ionized gas has a plasma property. The coating flow field near the surface of the flying target is generally called a plasma coating flow field, and then enters the plasma or a plasma shell, which is equivalent to the condition that the flying target is covered by the plasma (raining, supersonic/hypersonic plasma flow field numerical simulation and electromagnetic property research thereof, doctor thesis of national defense science and technology university, 2009).

The problem of electromagnetic scattering of flying targets using numerical methods has been somewhat difficult due to the non-uniformity of the relative dielectric constant of the plasma formed by the ionization of air. Through research, the plasma shell at the top end part of the aircraft has a larger equivalent relative dielectric constant, and the dielectric constant of other parts of the plasma shell is close to that of air. For such metal-plasma hybrid structures, the metal parts are usually treated as ideal electrical conductors (PECs) and are easily solved analytically by the surface-integral-equation method (SIE), where RWG basis functions (Rao M, Wilton D and glissona. electromagnetic scattering by surfaces of the area shape. ieee transformation Antennas and amplification, 1982,30(3): 409-. The media fraction is typically analyzed using the volume fraction equation method (Schaubert D, Wilton D and Glisson A.A quaternary modeling method for electrochemical characterization of byaborral patterned inorganic semiconductors IEEE transfer on extensions and Propagation,1984,32(1): 77-85.). And when the volume-surface integral equation is used for processing, the part similar to air can be omitted, so that the unknown quantity is greatly saved, and the consumption of the memory is saved. Because the unknown quantity is huge due to the fact that the plasma housing part is subjected to volume subdivision, even if the part with the relative dielectric constant close to 1 is treated as air, the problem of high computing resource consumption still exists.

Disclosure of Invention

The invention aims to provide an electromagnetic scattering analysis method of an ultrahigh-speed flying target, so that electromagnetic scattering characteristic parameters of the ultrahigh-speed flying target can be quickly obtained.

The technical solution for realizing the purpose of the invention is as follows: an electromagnetic scattering analysis method for an ultra-high-speed flying target comprises the following steps:

firstly, establishing a plasma shell model of an ultrahigh-speed flight target, carrying out pneumatic simulation calculation on the ultrahigh-speed flight target according to the flight height, the attack angle and the flight Mach number parameters of the flight target to obtain the electronic number density, the temperature and the pressure information data of the target, thus obtaining the characteristic frequency and the collision frequency of plasma, obtaining the equivalent relative dielectric constant of each space position of the plasma shell by the following formula,

${\mathrm{\ϵ}}_r=1-\frac{{{\mathrm{\ω}}^2}_{\mathrm{pe}}}{{\mathrm{\ω}}^2+v^2}-j\frac{v}{\mathrm{\ω}}\frac{{{\mathrm{\ω}}^2}_{\mathrm{pe}}}{{\mathrm{\ω}}^2+v^2}---\left(1\right)$

wherein ω is_peIs the plasma characteristic frequency, omega is the electromagnetic wave frequency, v is the plasma collision frequency;

secondly, triangularly dividing a flying target metal part, taking a part of the plasma shell with the equivalent relative dielectric constant close to 1 as air, and performing mesh division without using the part, tetrahedrally dividing a non-air area part of the plasma shell, and performing self-adaptive mesh encryption processing on an area with a large equivalent relative dielectric constant;

thirdly, according to the scattering characteristic of the high-overspeed flying target structure of the wrapping plasma shell sleeve, a moment method basic theory is adopted to obtain a volume-surface integral equation, and the matrix equation form is as follows:

$\left[\begin{array}{cc}{Z}_{\mathrm{mn}}^{\mathrm{DD}}& Z_{\mathrm{mn}}^{\mathrm{MD}}\\ Z_{\mathrm{mn}}^{\mathrm{DM}}& Z_{\mathrm{mn}}^{\mathrm{MM}}\end{array}\right]\left[\begin{array}{c}{D}_n\\ I_n\end{array}\right]=\left[\begin{array}{c}{v}_m^V\\ v_m^S\end{array}\right]---\left(2\right)$

Z^DDrepresents the action of the medium on the medium, Z^DMPair of display mediaAction of a metal, Z^MDAll represent interacting moieties of the medium and the metal, Z^MMRepresenting the effect of the metal on the metal, D_nAnd I_nIs the unknown coefficient to be found,andis the right vector excitation;

step four, the Green function of the free space in the step threeExpanding according to an addition theorem, and giving specific expressions of a volume aggregation factor, a transfer factor and a configuration factor in a volume surface integral equation;

and fifthly, solving the matrix equation (2) to obtain a current coefficient, and calculating the electromagnetic scattering parameter according to the current coefficient for reciprocity reasons.

Whether the plasma part is regarded as air is judged by adopting the formula 3:

||r|-1|≤ (3)

wherein,_rit is determined whether the plasma portion is treated as air for the plasma equivalent relative permittivity.

The specific expression form of the matrix equation in the step 3 is as follows:

$Z^{\mathrm{DD}}=\underset{V_m}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·\frac{\stackrel{\→}{D}\left({\stackrel{\→}{r}}^{\′}\right)}{\widehat{\mathrm{\ϵ}}\left({\stackrel{\→}{r}}^{\′}\right)}d\stackrel{\→}{r}+\mathrm{j\ω}\underset{V_m}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}$

(4)

$-\underset{V_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}+\underset{{\mathrm{\Ω}}_m}{\∫}(\stackrel{\→}{n}\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}$

$Z^{\mathrm{MD}}=\mathrm{j\ω}\underset{V_m}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}-\underset{V_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}+\underset{{\mathrm{\Ω}}_m}{\∫}(\stackrel{\→}{n}\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}---\left(5\right)$

$Z^{\mathrm{DM}}=\mathrm{j\ω}\underset{S_m}{\∫}{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}-\underset{S_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}---\left(6\right)$

$Z^{\mathrm{MM}}=\mathrm{j\ω}\underset{S_m}{\∫}{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}-\underset{S_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}---\left(7\right)$

wherein,andrespectively represent the body and surface test basis functions, omega is the angular frequency of the electromagnetic wave,andare respectively as Andrepresenting the required electric flux density and metal plane current density,is the green function of free space;

the right vector in the above formula is generated by plane wave and can be written as

$v_m^V=\underset{V}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{E}}^{i}d\stackrel{\→}{r}---\left(8\right)$

$v_m^S=\underset{V}{\∫}{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{E}}^{i}d\stackrel{\→}{r}---\left(9\right)$

Is the incident electric field.

The step 4 of giving specific expressions of the bulk polymerization factor, the transfer factor and the configuration factor in the bulk area integral equation is as follows:

step 4.1, two points r in different groups m and n in the same layer_iAnd r_jLet r be_iIs the observation point in the m group, r_jIs the source point in the n groups, r_mAnd r_nRepresenting the center of the group where the viewpoint and the source point are located, the vector from the viewpoint to the source point being r_ij＝r_i-r_j＝r_im+r_mn+r_njIf groups m and n are neither coincident nor adjacent, | r_im+r_nj|＜|r_mnThe scalar green function is expanded using the vector addition theorem as follows:

wherein,

$T_L(\hat{k}\·\hat{r})=\underset{l=0}{\overset{L}{\mathrm{\Σ}}}{(-j)}^l(2l+1)h_l^{\left(2\right)}\left(\mathrm{kr}\right)P_l(\hat{k}\·\hat{r})---\left(12\right)$

for the transfer factor, L is the number of truncated terms for the infinite sum,is a second class of spherical Hank function, P_l(. cndot.), which is a Legendre function,representing a double integral of angular spectral space, usually requiring K_L＝2(L+1)²An integration point, L ═ kd + α log (pi + kd), and d is the group size;

step 4.2, give Z^DD、Z^MD、Z^DMAnd Z^MMThe specific expressions of the aggregation factor, the transfer factor and the configuration factor are respectively as follows:

compared with the prior art, the invention has the following remarkable advantages: 1. the unknown quantity is small. Because the plasma region with the equivalent relative dielectric constant close to 1 is treated as air, mesh division is not needed, the unknown quantity is reduced, and meanwhile, because the plasma region with the relative equivalent power-saving parameter large is subjected to self-adaptive encryption, the unknown quantity is further reduced under the condition of not influencing the precision. 2. The solving speed is fast. Because the volume surface integral equation is adopted to analyze the ultrahigh-speed flying target and the non-uniform plasma wrapped outside the ultrahigh-speed flying target, the Green function is a Green function of free space, the introduction of a multilayer rapid multilevel sub-technology is facilitated, and the matrix solution is accelerated.

Drawings

Fig. 1 is a subdivision diagram of a subdivision point, a is an initialization diagram, b is a subdivision diagram, and c is each tetrahedron after subdivision.

Fig. 2 is a schematic diagram of two-subdivision point subdivision, a is an initialization diagram, b is a schematic diagram of the remaining polyhedron, c is a schematic diagram of subdivision, and d is each tetrahedron after subdivision.

Fig. 3 is a schematic diagram of three-subdivision-point subdivision, a is an initialization diagram, b is a schematic diagram of the remaining polyhedron, c is a schematic diagram of subdivision, and d is each tetrahedron after subdivision.

Fig. 4 is a schematic diagram and a dimension diagram of a two-dimensional structure of a blunt cone.

Fig. 5 is a relative permittivity distribution.

Figure 6 compares the two results of the vsees.

FIG. 7 is a diagram of a blunt cone model dual station RCS.

Detailed Description

The invention relates to an electromagnetic scattering analysis method of an ultra-high-speed flying target, which comprises the following steps:

firstly, establishing a high-speed flight target and a plasma shell model, mainly determining an electromagnetic parameter model of the plasma shell, wherein the electromagnetic parameter model is related to the flight environment of the high-speed flight target, such as flight height, flight speed, atmospheric pressure and temperature around the flight target, and the like.

And secondly, grid processing. And a triangular subdivision is adopted for the metal part, and a tetrahedral subdivision is adopted for the plasma shell part.

And thirdly, establishing a volume-surface integral equation. Depending on the scattering properties of the hybrid structure, the total field at the target is equal to the sum of the incident field, which is a known excitation, and all scattered fields, which are typically used as incident electric fields, can be represented by the required electric flux density and induced current density.

And fourthly, expanding the Green function in the free space based on the addition theorem, and combining an expression of a surface integral equation to provide a specific expression form of the aggregation factor, the transfer factor and the configuration factor of the far field part.

And fifthly, solving a matrix equation and calculating electromagnetic scattering parameters.

The present invention is described in further detail below with reference to the attached drawing figures.

Firstly, establishing a super-high speed flight target and a plasma shell model, mainly determining an electromagnetic parameter model of the plasma shell, wherein the electromagnetic parameter model is related to the flight environment of the super-high speed flight target, such as flight altitude, flight speed, atmospheric pressure and temperature around the flight target, and the like. Performing pneumatic simulation calculation on a target model according to the flight altitude, the attack angle and the flight Mach number parameters of a flight target to obtain the electronic number density, the temperature and the pressure information data of the target, thereby obtaining the characteristic frequency and the collision frequency of the plasma, obtaining the equivalent relative dielectric constant of the plasma shell by the following formula,

${\mathrm{\ϵ}}_r=1-\frac{{{\mathrm{\ω}}^2}_{\mathrm{pe}}}{{\mathrm{\ω}}^2+v^2}-j\frac{v}{\mathrm{\ω}}\frac{{{\mathrm{\ω}}^2}_{\mathrm{pe}}}{{\mathrm{\ω}}^2+v^2}---\left(1\right)$

wherein ω is_peIs the characteristic frequency of the plasma, omega is the frequency of the electromagnetic wave, and v is the collision frequency of the plasma.

And secondly, performing triangular subdivision on the metal part, and performing tetrahedral subdivision on the plasma shell part. Different thresholds can be used for different required calculation accuracy to decide whether the plasma part is treated as air or not, namely, mesh division is not needed. The judgment is based on

||_r|-1|≤ (2)

Wherein,_ris the plasma equivalent relative permittivity. The area with larger equivalent relative dielectric constant needs to adopt self-adaptive grid encryption processing; the three-dimensional self-adaptive grid is self-adaptively encrypted according to nodes, so the tetrahedron is divided into four modes according to the different numbers of the nodes needing to be encrypted.

The case where the tetrahedron contains only one subdivision point is shown in fig. 1, the point denoted by reference numeral 7 being a subdivision point, the original tetrahedron being divided into four parts: 4567. 2675, 1752, and 1237.

The tetrahedral unit comprises two subdivision nodes as shown in fig. 2, the tetrahedron is subdivided into 7 tetrahedrons: 1567. 4789, 5678, 6789, 2568, 2689 and 2369.

The tetrahedral cell comprises three subdivision nodes as shown in fig. 3, the tetrahedron is subdivided into 7 tetrahedrons: 1578. 5789, 2569, 5679, 3671, 6791, 4891 and 7891.

Thirdly, according to the scattering characteristic of the high-overspeed flying target structure of the wrapping plasma shell sleeve, a moment method basic theory is adopted to obtain a volume-surface integral equation, and the matrix equation form is as follows:

$\left[\begin{array}{cc}{Z}_{\mathrm{mn}}^{\mathrm{DD}}& Z_{\mathrm{mn}}^{\mathrm{MD}}\\ Z_{\mathrm{mn}}^{\mathrm{DM}}& Z_{\mathrm{mn}}^{\mathrm{MM}}\end{array}\right]\left[\begin{array}{c}{D}_n\\ I_n\end{array}\right]=\left[\begin{array}{c}{v}_m^V\\ v_m^S\end{array}\right]---\left(3\right)$

wherein:

$Z^{\mathrm{DD}}=\underset{V_m}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·\frac{\stackrel{\→}{D}\left({\stackrel{\→}{r}}^{\′}\right)}{\widehat{\mathrm{\ϵ}}\left({\stackrel{\→}{r}}^{\′}\right)}d\stackrel{\→}{r}+\mathrm{j\ω}\underset{V_m}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}$

(4)

$-\underset{V_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}+\underset{{\mathrm{\Ω}}_m}{\∫}(\stackrel{\→}{n}\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}$

$Z^{\mathrm{MD}}=\mathrm{j\ω}\underset{V_m}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}-\underset{V_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}+\underset{{\mathrm{\Ω}}_m}{\∫}(\stackrel{\→}{n}\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}---\left(5\right)$

$Z^{\mathrm{DM}}=\mathrm{j\ω}\underset{S_m}{\∫}{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}-\underset{S_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}---\left(6\right)$

$Z^{\mathrm{MM}}=\mathrm{j\ω}\underset{S_m}{\∫}{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{A}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}-\underset{S_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_S\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}---\left(7\right)$

wherein,andrespectively represent the body and surface test basis functions, omega is the angular frequency of the electromagnetic wave,andare respectively as Andrepresenting the required electric flux density and metal plane current density,is the green function of free space.

The right vector in the above formula is generated by plane wave and can be written as

$v_m^V=\underset{V}{\∫}{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{E}}^{i}d\stackrel{\→}{r}---\left(8\right)$

$v_m^S=\underset{V}{\∫}{\stackrel{\→}{f}}_m^S\left(\stackrel{\→}{r}\right)\·{\stackrel{\→}{E}}^{i}d\stackrel{\→}{r}---\left(9\right)$

Is the incident electric field.

Z^DDRepresents the action of the medium on the medium, Z^DMShowing the effect of the medium on the metal, Z^MDAll represent interacting moieties of the medium and the metal, Z^MMRepresents the effect of metal on metal;

and fourthly, expanding the Green function of the free space according to the addition theorem, and giving specific expressions of the volume aggregation factor, the transfer factor and the configuration factor in the volume surface integral. In the fast multipole method implementation we consider points in the same layer that are in two different groups. Let r be_iIs the observation point in the m group, r_jAre the source points in the n groups. If we use r_mAnd r_nTo represent the center of the group where the viewpoint and source point are located, the viewpoint to source point vector is r_ij＝r_i-r_j＝r_im+r_mn+r_nj. If groups m and n are neither coincident nor adjacent, | r_im+r_nj|＜|r_mnL. The scalar green function of the three-dimensional problem can be expanded using the vector addition theorem as follows:

$T_L(\hat{k}\·\hat{r})=\underset{l=0}{\overset{L}{\mathrm{\Σ}}}{(-j)}^l(2l+1)h_l^{\left(2\right)}\left(\mathrm{kr}\right)P_l(\hat{k}\·\hat{r})---\left(12\right)$

in the above formula, the first and second carbon atoms are,for the transfer factor, L is the number of truncated terms for the infinite sum,is a second class of spherical Hank function, P_l(·)Is the legendre function.Representing a double integral of angular spectral space, usually requiring K_L＝2(L+1)²Typically L ═ kd + α log (pi + kd), and d is the size of the group.

Giving Z^DD、Z^MD、Z^DMAnd Z^MMThe specific expressions of the aggregation factor, the transfer factor and the configuration factor are respectively as follows:

and fifthly, solving a matrix equation to obtain a current coefficient, and calculating the electromagnetic scattering parameter according to the current coefficient for reciprocity reasons.

In order to verify the efficiency and accuracy of the method, an example of electromagnetic scattering of a very high speed flying target is given below, and the performance of the method can be seen in the graph.

The two-dimensional structure of the blunt cone model is shown in figure 1, the electromagnetic parameter model is shown in figure 2, the left graph is the real part value of the equivalent relative dielectric parameter, and the right graph is the imaginary part value of the equivalent relative dielectric parameter. After mesh division, the total unknown quantity is 686230+8379 (medium triangle + inner side), and if the equivalent relative dielectric constant modulus is within the range of ensuring the calculation accuracy, the equivalent relative dielectric constant modulus is between 0.95 and 1.05(=0.5)The plasma part is treated as air, the final total unknown quantity is 133399+8379, if the plasma with the equivalent relative dielectric constant modulus value in the range of 0.9-1.1 (=1) is treated as air part, the final total unknown quantity is 72469+8379, and three-layer fast multipole calculation is used. Calculating in LINUX compiling environment, calling 32 processes for parallel calculation, using MUMPS precondition, and making incidence angle beAt a frequency of 2GHz, two station RCSs with two different threshold selections were compared, as shown in fig. 3. FIG. 4 is a comparison of the calculation results of the present invention (the relative dielectric constant modulus is in the range of 0.9 to 1.1) and the FEBI method.

Table 1 comparison of the results of the blunt cone model calculation.

Claims (4)

1. An electromagnetic scattering analysis method of a super-high-speed flying target is characterized by comprising the following steps:

firstly, establishing a plasma shell model of an ultrahigh-speed flight target, carrying out pneumatic simulation calculation on the ultrahigh-speed flight target according to the flight height, the attack angle and the flight Mach number parameters of the flight target to obtain the electronic number density, the temperature and the pressure information data of the target, thus obtaining the characteristic frequency and the collision frequency of plasma, obtaining the equivalent relative dielectric constant of each space position of the plasma shell by the following formula,

wherein ω is_peIs the plasma characteristic frequency, omega is the electromagnetic wave frequency, v is the plasma collision frequency;

secondly, triangularly dividing a flying target metal part, taking a part of the plasma shell with the equivalent relative dielectric constant close to 1 as air, and performing mesh division without using the part, tetrahedrally dividing a non-air area part of the plasma shell, and performing self-adaptive mesh encryption processing on an area with a large equivalent relative dielectric constant;

thirdly, according to the scattering characteristic of the high-overspeed flying target structure of the wrapping plasma shell sleeve, a moment method basic theory is adopted to obtain a volume-surface integral equation, and the matrix equation form is as follows:

Z^DDrepresents the action of the medium on the medium, Z^DMShowing the effect of the medium on the metal, Z^MDAll represent interacting moieties of the medium and the metal, Z^MMRepresenting the effect of the metal on the metal, D_nAnd I_nIs the unknown coefficient to be found,andis the right vector excitation;

the fourth step, to the Green function of free spaceExpanding according to an addition theorem, and giving specific expressions of a volume aggregation factor, a transfer factor and a configuration factor in a volume surface integral equation;

and fifthly, solving the matrix equation (2) to obtain a current coefficient, and calculating the electromagnetic scattering parameter according to the current coefficient for reciprocity reasons.

2. The method of claim 1, wherein the plasma portion is determined as air by formula 3:

||_r|-1|≤ (3)

wherein,_rit is determined whether the plasma portion is treated as air for the plasma equivalent relative permittivity.

3. The method for analyzing electromagnetic scattering of an ultra-high speed flying target according to claim 1, wherein the matrix equation in the third step is expressed as follows:

wherein,andrespectively represent the body and surface test basis functions, omega is the angular frequency of the electromagnetic wave,andare respectively as Andrepresenting the required electric flux density and metal plane current density,is the green function of free space;

the right vector in equation (2) is generated by plane waves and can be written as

Is the incident electric field.

4. The method for analyzing electromagnetic scattering of an ultra-high speed flying target according to claim 1, wherein the step of giving specific expressions of bulk polymerization factor, transfer factor and configuration factor in the bulk area integral equation in the fourth step is as follows:

step 4.1, two points r in different groups m and n in the same layer_iAnd r_jLet r be_iIs the observation point in the m group, r_jIs in group nSource point, r_mAnd r_nRepresenting the center of the group where the viewpoint and the source point are located, the vector from the viewpoint to the source point being r_ij＝r_i-r_j＝r_im+r_mn+r_njIf groups m and n are neither coincident nor adjacent, | r_im+r_nj|＜|r_mnThe scalar green function is expanded using the vector addition theorem as follows:

wherein,

for the transfer factor, L is the number of truncated terms for the infinite sum,is a second class of spherical Hank function, P_l(. cndot.) is a Legendre function,representing a double integral of angular spectral space, usually requiring K_L＝2(L+1)²An integration point, L ═ kd + α log (pi + kd), and d is the group size;

step 4.2, give Z^DD、Z^MD、Z^DMAnd Z^MMThe specific expressions of the aggregation factor, the transfer factor and the configuration factor are respectively as follows:

。