The spatial models of radiation of jets of combustion products of rocket engines

Main results

• A software package has been developed for calculating directional spectral emissivity (signatures) of emitting spatial objects of astrophysics and atmospheric physics, based on Monte-Carlo simulation methods;
• The principal scientific novelty of the developed program complex is the ability to determine the spectral emissivity of jets, emitting volumes of arbitrary geometry;
• This software package includes an electronic database of spectral optical properties of heated gases and low-temperature plasma;
• More information may be found in the book (in russian): Surzhikov S.T. Thermal radiation of gases and plasma, Moscow: BMSTU publishing, 2004. 544 p. (Computer models of physical mechanics).

Actual problems

• Creation of a database of spectral optical properties of the emitting gases at high temperatures taking into account the fine structure of the rotational spectrum and the nonequilibrium excitation of molecular components;
• Development of new Monte Carlo algorithms (including algorithms for parallel computing) for calculation of the spectral emissivity with and without consideration of the fine rotational structure;
• Calculation of signatures of emitting objects taking into account fine rotational structure of the spectrum;
• Development of 3-dimensional models taking into account the spatial and temporal fluctuations and nonequilibrium radiation.

The development of algorithms of local sampling for simulation of signatures

Generation of quasi-random numbers; Calculation of the angular coordinates of the isotropic and anisotropic random unit vector; Statistical estimation of the initial coordinates of the trajectories of photons; Calculation of the trajectory of group of photons in an inhomogeneous medium; Simulation of the mean free path; Statistical estimation of collision processes of photons with particles of the medium; Calculation of the probability of absorption or scattering of group of photons; Assessment of the contribution to the radiation after each elementary act of interaction of group of photons with particles of the medium; The calculation of the spectral intensity based on the results of simulation; The calculation of the spectral flux of thermal radiation; Evaluation of the statistical error of the simulation results.

Temperature of the gas (left) and of the condensed phase (right) in the axisymmetric jet

The temperature of the gas in the block jet

The integral emissivity of the 3 block jet of the first type with a high level of scattering
N_ph=10⁶, where N_ph - number of photon

(a)

(b)

The spectral signature of a tactical missile with fuel based on AP/HTPB:
a) x_Al2O3=0.0005, r_p=1.0 μm, N_Al2O3=4.04*10⁴ cm^-3;
b) x_Al2O3=0.05, r_p=1.0 μm, N_Al2O3=4.25*10⁶ cm^-3.

The prediction of the spectral directional emissivity of a cylindrical volume (H₂O/N₂) at high temperatures

(a)

(b)

Interpretation of ERIM experimental data:
a) Spectral optical model with averaging on 25 cm^-1;
b) Optical model based on the HITRAN data.

The prediction of the spectral directional emissivity of a cylindrical volume (CO₂/N₂) at high temperatures

(a)

(b)

(c)

Interpretation of ERIM experimental data (results were obtained using temperature extrapolated HITRAN data):
a) Averaging over the rotational structure (JLBL=0, JSUM=1);
b) Averaging over the rotational structure (JLBL=0, JSUM=0);
c) A statistical model of the rotational lines (JLBL=3).

The prediction of the spectral directional emissivity of a cylindrical volume (CO₂/N₂), weakned by a cold gas

(a)

(b)

Interpretation of ERIM experimental data (results were obtained using temperature extrapolated HITRAN data):
a) A statistical model of the rotational lines (JLBL=2, approximation of the weak line),
a spectral group model 25 cm^-1;
b) A statistical model (JLBL=2), a spectral group model 25 cm^-1.

The prediction of the spectral directional emissivity of a cylindrical volume (CO₂/N₂), weakned by a cold gas

Interpretation of ERIM experimental data. Line-by-line calculations with the spectral resolution of 0.0083 cm^-1

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