CN103198227A - Electromagnetic scattering analyzing method for superspeed flight targets - Google Patents

Abstract

The invention discloses an electromagnetic scattering analyzing method for superspeed flight targets. For non-uniform characteristics of plasmas around the superspeed flight targets, a part of equivalent relative dielectric constant, approximate to one, of the plasmas is used as the air to be processed by analyzing through a volume-surface integer equation, and areas with larger equivalent relative dielectric constant are encrypted by the adaptive network so as to achieve required solving accuracy. By adopting conventional method of uniform grid subdivision plasma casing, the electromagnetic scattering analyzing method can greatly save computing resources, green function adopted in the volume-surface integer equation is green function in vacuum, multilayer speedy multi-step ion technology is used for accelerating solving, so that fewer internal memory and shorter computing time are required for solving the problem of scattering of the superspeed flight targets.

Description

The Analysis of Electromagnetic Scattering method of hypervelocity flight target

Technical field

The invention belongs to the quick computing technique of Electromagnetic Scattering of Target characteristic, particularly a kind of Analysis of Electromagnetic Scattering method that is applied to the hypervelocity flight target.

Background technology

The hypervelocity flight target is owing to have very fast flying speed (more than 3 Mach) and higher flying height (more than the 20Km), in its when flight, produce several thousand degrees centigrade pneumatic heat with the windage meeting, makes its surrounding air owing to ionization is the ionic condition existence.When degree of ionization acquired a certain degree, ionized gas had plasma properties.Be commonly called plasma and coat the flow field, reenter plasma or plasma valve jacket this moment in the coating flow field of airbound target near surface, be equivalent to this moment airbound target covered by plasma (normal rain. supersonic speed/hypersonic plasma Field Flow Numerical Simulation and electromagnetic property research thereof, National University of Defense technology's PhD dissertation, 2009).

Because air is ionized the unevenness of the plasma relative dielectric constant of formation, causes using the electromagnetic scattering problems of numerical method analysis airbound target to have certain difficulty.By discovering, the plasma valve jacket that is positioned at the aircraft head portion has bigger equivalent relative dielectric constant, and gas ions valve jacket other parts medium specific inductive capacity is near air.At this metallic plasma mixed structure, the metal part is used as ideal conducting body (PEC) usually and handles, and quilt cover integral Equation Methods (SIE) is come analysis and solution easily, RWG basis function (Rao M wherein, Wilton D and Glisson A.Electromagnetic scattering by surfaces of arbitrary shape.IEEE Transaction on Antennas and Propagation, 1982,30 (3): 409 – 418.) because its dirigibility is used as the basis function that launches unknown current usually.The medium part, usually use body integral Equation Methods (Schaubert D, Wilton D and Glisson A.A tetrahedral modeling method for electromagnetic scattering by arbitrarily shaped inhomogeneous dielectric bodies.IEEE Transaction on Antennas and Propagation, 1984,32 (1): 77 – 85.) analyze.And, when handling, can consider that airlike part is saved nearly, thereby save unknown quantity greatly with honorable integral equation, save the consumption of internal memory.Because article on plasma body valve jacket partly adopts the body subdivision to cause unknown quantity huge, even if taked relative dielectric constant is handled as air close to 1 part, still do not face person's computational resource and consume high problem.

Summary of the invention

The object of the present invention is to provide a kind of Analysis of Electromagnetic Scattering method of hypervelocity flight target, thereby realize obtaining fast the electromagnetic scattering characterisitic parameter of hypervelocity flight target.

The technical solution that realizes the object of the invention is: a kind of Analysis of Electromagnetic Scattering method of hypervelocity flight target, and step is as follows:

The first step, set up hypervelocity flight target plasma valve jacket model, flying height, the angle of attack and flight Mach number parameter according to airbound target, the hypervelocity flight target is carried out pneumatic analog to be calculated, obtain electron number density, temperature and the pressure information data of target, obtain plasma characteristics frequency and collision frequency thus, obtained the equivalent relative dielectric constant of each locus of plasma valve jacket again by following formula

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

ω wherein _PeBe the plasma characteristics frequency, ω is wave frequency, and v is the plasma collision frequency;

Second step, the airbound target metal is partly adopted triangle subdivision, plasma valve jacket equivalent relative dielectric constant is used as air close to 1 part, do not need to carry out mesh generation, plasma valve jacket non-air area part adopts the tetrahedron subdivision, and the adaptive mesh encryption is adopted in the bigger zone of equivalent relative dielectric constant;

In the 3rd step, the scattering properties according to the high hypervelocity of parcel plasma valve jacket airbound target structure adopts the method for moment basic theory, obtains honorable integral equation, and its matrix form equation is:

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

Z ^DDRepresent medium to the effect of medium, Z ^DMThe expression medium is to the effect of metal, Z ^MDThe interaction part of all representing medium and metal, Z ^MMThe effect of expression metal to metal, D _nAnd I _nBe unknowm coefficient to be asked,

With

It is the right vector excitation;

The 4th step is to the free space Green function in the 3rd step

Launch according to addition theorem, and provide the formula that embodies of body polymerizing factor, transfer factor and the configuration factor in the honorable integral equation;

The 5th step, find the solution matrix equation (2), obtain current coefficient, calculate the electromagnetic scattering parameter according to reciprocal theorem by current coefficient again.

Adopt formula 3 to judge whether the plasma part is used as air:

||εr|-1|≤δ (3)

Wherein, ε _rBe the plasma equivalent relative dielectric constant, δ determines whether the plasma part is used as air-treatment.

In the described step 3 matrix equation to embody form 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, With Represent body and face test basis function respectively, ω is the electromagnetic wave angular frequency,

With

Be respectively With

Represent dielectric (flux) density to be asked and metal covering current density,

It is the Green function of free space;

The right vector is produced by plane wave in the following formula, can be write as

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

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

It is the incident electric field.

Providing body polymerizing factor, transfer factor and the configuration factor in the honorable integral equation in the described step 4, to embody the step of formula as follows:

Step 4.1 is with two the some r of m and n on the same group that are arranged in not in one deck _iAnd r _j, suppose r _iBe the observation point in the m group, r _jBe the source point in the n group, r _mAnd r _nThe group switching centre at expression observation point and source point place, observation point is r to the vector of source point _Ij=r _i-r _j=r _Im+ r _Mn+ r _NjIf group m and n neither overlap also non-conterminous, so | r _Im+ r _Nj|＜| r _Mn|, the scalar Green function is unfolded as follows with the vector addition theorem:

Wherein,

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

Be transfer factor, L is the item number that blocks of infinite summation,

Be the second class ball Hankel function, P _l() is Legendre function, The double integral in expression angular spectrum space needs K usually _L=2 (L+1) ²Individual point, L=kd+ α log (π+kd), and d is the size of group;

Step 4.2 provides Z ^DD, Z ^MD, Z ^DMAnd Z ^MMPolymerizing factor, the formula that embodies of transfer factor and the configuration factor is respectively:

The present invention compared with prior art, its remarkable advantage: 1. unknown quantity is few.Because equivalent relative dielectric constant is used as air-treatment close to 1 plasma area, do not need to carry out mesh generation, reduced unknown quantity, simultaneously because the big plasma area of equivalent relatively economize on electricity parameter has been adopted adaptive refinement, under the condition that does not influence precision, further reduced unknown quantity.2. it is fast to find the solution speed.Because the non-homogeneous plasma that has adopted honorable integral equation to analyze the hypervelocity flight target and be wrapped in hypervelocity flight target outside, used Green function is the Green function of free space, makes things convenient for the multilayer introducing of multistage sub-technology fast, accelerates Matrix Solving.

Description of drawings

Fig. 1 is segmentation point segmentation synoptic diagram, and a is initialization figure, and b is the segmentation synoptic diagram, and c is each tetrahedron after the segmentation.

Fig. 2 is two segmentations point segmentation synoptic diagram, and a is initialization figure, and b is residue polyhedron synoptic diagram, and c is the segmentation synoptic diagram, and d is each tetrahedron after the segmentation.

Fig. 3 is three segmentations point segmentation synoptic diagram, and a is initialization figure, and b is residue polyhedron synoptic diagram, and c is the segmentation synoptic diagram, and d is each tetrahedron after the segmentation.

Fig. 4 is the signal of blunted cone two-dimensional structure and dimensional drawing.

Fig. 5 is that relative dielectric constant distributes.

Fig. 6 is that two kinds of results of VSIE compare.

Fig. 7 is the two station of blunted cone model RCS figure.

Embodiment

The Analysis of Electromagnetic Scattering method of hypervelocity flight target of the present invention, step is as follows:

The first step, set up high-speed flight target and plasma valve jacket model, mainly be the plasma valve jacket the electromagnetic parameter model determine that its flight environment of vehicle with the high-speed flight target is relevant, as flying height, flying speed and airbound target ambient atmosphere pressure and temperature etc.

In second step, grid is handled.Partly adopt triangle subdivision for metal, partly adopt the tetrahedron subdivision for the plasma valve jacket.

In the 3rd step, set up honorable integral equation.Scattering properties according to mixed structure, the incident field that resultant field on the target equals and all scattered field sum, the incident electric field is known excitation, and uniform plane wave is used as the incident electric field usually, and scattering electric field can be represented with electric flux density to be asked and induced current density.

The 4th step, Green function in the free space is launched based on addition theorem, the combination area divides the expression formula of equation, provides the polymerizing factor of far field part, the form that embodies of transfer factor and the configuration factor.

In the 5th step, matrix equation is found the solution and the electromagnetic scattering CALCULATION OF PARAMETERS.

Below in conjunction with accompanying drawing the present invention is described in further detail.

The first step, set up hypervelocity flight target and plasma valve jacket model, mainly be the plasma valve jacket the electromagnetic parameter model determine that its flight environment of vehicle with the hypervelocity flight target is relevant, as flying height, flying speed and airbound target ambient atmosphere pressure and temperature etc.Flying height, the angle of attack and flight Mach number parameter by airbound target, object module is carried out pneumatic analog to be calculated, obtain the electron number density of target, temperature, the pressure information data, obtain plasma characteristics frequency and collision frequency thus, obtained the equivalent relative dielectric constant of plasma valve jacket again by following formula

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

ω wherein _PeBe the plasma characteristics frequency, ω is wave frequency, and v is the plasma collision frequency.

Second step, partly adopt triangle subdivision for metal, partly adopt the tetrahedron subdivision for the plasma valve jacket.The computational accuracy that requires at difference can adopt different threshold value δ to decide the plasma part whether to be used as air-treatment, does not namely need to carry out mesh generation.Basis for estimation is as follows

||ε _r|-1|≤δ (2)

Wherein, ε _rBe the plasma equivalent relative dielectric constant.The adaptive mesh encryption then need be adopted in the zone that equivalent relative dielectric constant is bigger; The three-dimensional adaptive grid is owing to press the node self-adapting encryption, and the contained difference of encryption node number that needs is divided into four kinds of modes so tetrahedron divides.

The situation that tetrahedron only contains a segmentation point as shown in Figure 1, label is that 7 point is the segmentation point, former tetrahedron is divided into four parts: 4567,2675,1752 and 1237.

Tetrahedron element comprises two segmentation node situations as shown in Figure 2, and tetrahedron is subdivided into 7 tetrahedrons: 1567,4789,5678,6789,2568,2689 and 2369.

Tetrahedron element comprises three segmentation node situations as shown in Figure 3, and tetrahedron is subdivided into 7 tetrahedrons: 1578,5789,2569,5679,3671,6791,4891 and 7891.

In the 3rd step, the scattering properties according to the high hypervelocity of parcel plasma valve jacket airbound target structure adopts the method for moment basic theory, obtains honorable integral equation, and its matrix form equation is:

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

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, With

Represent body and face test basis function respectively, ω is the electromagnetic wave angular frequency,

With

Be respectively

With Represent dielectric (flux) density to be asked and metal covering current density,

It is the Green function of free space.

The right vector is produced by plane wave in the following formula, can be write as

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

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

It is the incident electric field.

Z ^DDRepresent medium to the effect of medium, Z ^DMThe expression medium is to the effect of metal, Z ^MDThe interaction part of all representing medium and metal, Z ^MMThe effect of expression metal to metal;

In the 4th step, the Green function of free space is launched according to addition theorem, and provide body polymerizing factor in the honorable integration, the formula that embodies of transfer factor and the configuration factor.In Fast Multiple Method method implementation process, we consider with two not on the same group the points that are arranged in one deck.Suppose r _iBe the observation point in the m group, r _jIt is the source point in the n group.If we use r _mAnd r _nThe group switching centre of representing observation point and source point place, observation point is r to the vector of source point so _Ij=r _i-r _j=r _Im+ r _Mn+ r _NjIf it is also non-conterminous that group m and n neither overlap, so | r _Im+ r _Nj|＜| r _Mn|.So the scalar Green function of three-dimensional problem can be unfolded as follows with the vector addition theorem:

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

In the following formula,

Be transfer factor, L is the item number that blocks of infinite summation,

Be the second class ball Hankel function, P _l() is Legendre function.

The double integral in expression angular spectrum space needs K usually _L=2 (L+1) ²Individual point.General L=kd+ α log (π+kd), and d is the size of group.

Provide Z ^DD, Z ^MD, Z ^DMAnd Z ^MMPolymerizing factor, the formula that embodies of transfer factor and the configuration factor is respectively:

The 5th step, find the solution matrix equation, obtain current coefficient, calculate the electromagnetic scattering parameter according to reciprocal theorem by current coefficient again.

For efficient and the precision of verification method, provided the example of the electromagnetic scattering of hypervelocity flight target below, the property of this method as can be seen in the chart.

Blunted cone model, two-dimensional structure as shown in Figure 1, the electromagnetic parameter model as shown in Figure 2, left side figure be relatively dielectric parameter value of real part of equivalence, right figure is equivalent relative dielectric parameter imaginary values.Through behind the mesh generation, total unknown quantity is 686230+8379(medium triangle+inner edge), in guaranteeing the computational accuracy scope, if the plasma of equivalent relative dielectric constant mould value between 0.95～1.05 (δ=0.5) partly treated as air-treatment, final unknown quantity adds up to 133399+8379, if the plasma of equivalent relative dielectric constant mould value in 0.9～1.1 (δ=1) scope is used as the air portion divisional processing, then final unknown quantity adds up to 72469+8379, uses three layers of Fast Multiple Method to calculate.Calculate under the LINUX translation and compiling environment, call 32 process parallel computations, use the pre-condition of MUMPS, incident angle is Frequency is 2GHz, and the two station RCS under two kinds of different threshold value selection situations compare, as shown in Figure 3.Fig. 4 then is the comparison of the inventive method result of calculation (relative dielectric constant mould value is in 0.9～1.1 scope) and FEBI method result of calculation.

Table 1 blunted cone model example result of calculation comparison sheet.

Claims (4)

1. the Analysis of Electromagnetic Scattering method of a hypervelocity flight target is characterized in that step is as follows:

The first step, set up hypervelocity flight target plasma valve jacket model, flying height, the angle of attack and flight Mach number parameter according to airbound target, the hypervelocity flight target is carried out pneumatic analog to be calculated, obtain electron number density, temperature and the pressure information data of target, obtain plasma characteristics frequency and collision frequency thus, obtained the equivalent relative dielectric constant of each locus of plasma valve jacket again by following formula

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

ω wherein _PeBe the plasma characteristics frequency, ω is wave frequency, and v is the plasma collision frequency;

Second step, the airbound target metal is partly adopted triangle subdivision, plasma valve jacket equivalent relative dielectric constant is used as air close to 1 part, do not need to carry out mesh generation, plasma valve jacket non-air area part adopts the tetrahedron subdivision, and the adaptive mesh encryption is adopted in the bigger zone of equivalent relative dielectric constant;

In the 3rd step, the scattering properties according to the high hypervelocity of parcel plasma valve jacket airbound target structure adopts the method for moment basic theory, obtains honorable integral equation, and its matrix form equation is:

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

(2)

Z ^DDRepresent medium to the effect of medium, Z ^DMThe expression medium is to the effect of metal, Z ^MDThe interaction part of all representing medium and metal, Z ^MMThe effect of expression metal to metal, D _nAnd I _nBe unknowm coefficient to be asked, With

It is the right vector excitation;

The 4th step is to the free space Green function in the 3rd step

Launch according to addition theorem, and provide the formula that embodies of body polymerizing factor, transfer factor and the configuration factor in the honorable integral equation;

The 5th step, find the solution matrix equation (2), obtain current coefficient, calculate the electromagnetic scattering parameter according to reciprocal theorem by current coefficient again.

2. the Analysis of Electromagnetic Scattering method of hypervelocity flight target according to claim 1 is characterized in that, adopts formula 3 to judge whether the plasma part is used as air:

||ε _r|-1|≤δ (3)

Wherein, ε _rBe the plasma equivalent relative dielectric constant, δ determines whether the plasma part is used as air-treatment.

3. the Analysis of Electromagnetic Scattering method of hypervelocity flight target according to claim 1 is characterized in that, in the described step 3 matrix equation to embody form as follows:

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

$-\underset{V_m}{\∫}(\▿\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}+\underset{{\mathrm{\Ω}}_m}{\∫}(\stackrel{\→}{n}\·{\stackrel{\→}{f}}_m^V\left(\stackrel{\→}{r}\right)){\mathrm{\Φ}}_V\left({\stackrel{\→}{r}}^{\′}\right)d\stackrel{\→}{r}---\left(4\right)$

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

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

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

Wherein,

With

Represent body and face test basis function respectively, ω is the electromagnetic wave angular frequency,

With

Be respectively

With

Represent dielectric (flux) density to be asked and metal covering current density,

It is the Green function of free space;

The right vector is produced by plane wave in the following formula, can be write as

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

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

It is the incident electric field.

4. the Analysis of Electromagnetic Scattering method of hypervelocity flight target according to claim 1 is characterized in that, providing body polymerizing factor, transfer factor and the configuration factor in the honorable integral equation in the described step 4, to embody the step of formula as follows:

Step 4.1 is with two the some r of m and n on the same group that are arranged in not in one deck _iAnd r _j, suppose r _iBe the observation point in the m group, r _jBe the source point in the n group, r _mAnd r _nThe group switching centre at expression observation point and source point place, observation point is r to the vector of source point _Ij=r _i-r _j=r _Im+ r _Mn+ r _NjIf group m and n neither overlap also non-conterminous, so | r _Im+ r _Nj|＜| r _Mn|, the scalar Green function is unfolded as follows with the vector addition theorem:

Wherein,

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

Be transfer factor, L is the item number that blocks of infinite summation,

Be the second class ball Hankel function, P _l() is Legendre function,

The double integral in expression angular spectrum space needs K usually _L=2 (L+1) ²Individual point, L=kd+ α log (π+kd), and d is the size of group;

Step 4.2 provides Z ^DD, Z ^MD, Z ^DMAnd Z ^MMPolymerizing factor, the formula that embodies of transfer factor and the configuration factor is respectively:

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