An Improved Reverse Monte Carlo Method for the Investigation of Aerodynamic and Infrared Radiation Characteristics of a Flying Wing UAV

2020 ◽  
Author(s):  
Xiang Gao ◽  
Qingzhen Yang ◽  
Huicheng Yang ◽  
Jin Bai ◽  
Yubo He
Keyword(s):  
Monte Carlo ◽  
Ray Tracing ◽  
Infrared Radiation ◽  
Exhaust System ◽  
Aerodynamic Performance ◽  
Spectral Radiance ◽  
Reverse Monte Carlo ◽  
Carbon Dioxide Absorption ◽  
Lateral Direction ◽  
Shaped Nozzle

Abstract Using the improved ray tracing method to improve the reverse Monte Carlo (RMC) method, which is used to analyze the infrared radiation (IR) characteristics of the exhaust system, can greatly improve the computational efficiency and accuracy, and the calculation accuracy is improved by more than 8% compared with the RMC using ray tracing algorithm. For a flying wing unmanned aerial vehicle (UAV), the influence of the geometry of the double S-shaped nozzles and the single S-shaped nozzles on the internal flow field were analyzed, then the influence of the internal and external flow on the aerodynamic performance of the S-shaped exhaust system, and the IR characteristics of the aircraft with different inlet and exhaust system in the 3μm-5μm and 8μm-14μm bands were studied. The aerodynamic performance of the S-shaped nozzles are studied by numerical simulations. The IR characteristics of the rear hemisphere on the single S-shaped nozzles and the double S-shaped nozzles were obtained, those nozzles have the similar engine matching performance. The double S-shaped nozzle, resulting in a decrease of the radiation intensity of the nozzle by at least 65%, compared to the single S-shaped nozzle in the 3μm-5μm band. The aerodynamic characteristics of the flying wing UAV with the two S-shaped exhaust systems are also compared, and the changes in lift and resistance are analyzed. The forward IR intensity of the flying wing UAV is significantly lower than that of the backward direction, and the upper direction IR intensity is higher than that of the lateral direction and the downward direction. Compared to the flying wing UAV with the single S-shaped exhaust system, the flying wing of the double S-shaped exhaust system has a lower IR intensity, for the peak intensity of the rear hemisphere in the 3μm-5μm band is reduced at least 80%, the maximum value of the locked distance is reduced to 25% of the UAV using the single S curved exhaust system. The ratio of the amount of aircraft skin radiation to the total radiation increases from 30% in the 3μm-5μm band to more than 70% in the 8μm-14μm band. From the results of spectral analysis of UAV from 13μm-14μm, the spectral radiance of the carbon dioxide absorption and emission band in the detector image is significantly less than that of the UAV with a single S-shaped nozzle.

Numerical Simulation on the Infrared Radiation Characteristics of S-Shaped Nozzles

2013 ◽  
Vol 482 ◽  
pp. 282-286 ◽  
Author(s):  
Xiang Gao ◽  
Qing Zhen Yang ◽  
Hong Zhou ◽  
Jian Nan He
Keyword(s):  
Infrared Radiation ◽  
Exhaust System ◽  
Reverse Monte Carlo ◽  
Axisymmetric Nozzle ◽  
Radiation Characteristics ◽  
Turbofan Engine ◽  
Infrared Intensity ◽  
Shaped Nozzle ◽  
Reverse Monte Carlo Method ◽  
Eccentric Distance

Infrared stealth is of great importance to increase the survival ability of the aircraft. The exhaust system is the main radiation source of the aircraft at the rare hemisphere. A program using reverse Monte-Carlo method was developed to calculate the infrared radiation intensity of afterburning turbofan engine under non-afterburning condition, and simulate axisymmetric nozzle and three S-shaped nozzles with different relative eccentric distances. The results demonstrate that: the infrared intensity of S-shaped nozzle is much lower than that of axisymmetric nozzle; S-shaped nozzle can effectively reduce the maximum of IR intensity in the rear hemispheric space; the S-shaped nozzle with the relative eccentric distance of 0.5 can reduce the intensity of infrared radiation in critical detection directions effectively.

A Parametric Case Study in Radiative Heat Transfer Using the Reverse Monte-Carlo Ray-Tracing With Full-Spectrum k-Distribution Method

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Xiaojing Sun ◽  
Philip J. Smith
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Ray Tracing ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Reverse Monte Carlo ◽  
Full Spectrum ◽  
Distribution Method ◽  
Mesh Resolution ◽  
Emitting Media

A combined method of reverse Monte-Carlo ray-tracing with full-spectrum k-distribution (FSK) for computing the radiative heat transfer is applied to an extreme nonhomogeneous case (both temperature and gas mixture composition vary with positions) with an absorbing, emitting media. The parameter studies of the scaled FSK (FSSK) and correlated FSK (FSCK) methods for the case, such as g point resolution, mesh resolution, reference states, and integration quadratures, are carried out. The results from the FSSK and FSCK are only affected by the chosen reference states and are not sensitive to other parameters.

Numerical Simulation on the Infrared Radiation Characteristics of Ejector Nozzle Based on RMCM

2011 ◽  
Vol 138-139 ◽  
pp. 879-885
Author(s):  
Li Hai Chen ◽  
Qing Zhen Yang ◽  
Jin Hui Cui
Keyword(s):  
Flow Field ◽  
Infrared Radiation ◽  
Exhaust System ◽  
Three Dimension ◽  
Radiation Characteristics ◽  
Lateral Direction ◽  
Average Temperature ◽  
System A ◽  
Infrared Intensity ◽  
Ejector Nozzle

Based on the numerical calculation of three-dimension flow field of the exhaust system, a code is developed by the reverse Monte-Carlo method (RMCM) to simulate the infrared radiation characteristics of the aeroengine exhaust system and the plume. A ray-tracing method (RTM) is introduced to seek the meshes of the flow field which the ray travels through to avoid the trouble of interpolation. The infrared radiation characteristics of a certain turbo-fan engine’s ejector nozzle in the waveband of 3-5μm is simulated at non-afterburning condition. The results of the simulation show that : (1)Because of the introduction of the secondary flow, the average temperature of the ejector nozzle’s core plume is 20K lower than the baseline one’s.(2) The infrared intensity for the ejector nozzle is most reduced relatively by 44.5% in comparison with the baseline nozzle along lateral direction.(3) The ejector nozzle has a better performance of infrared stealth.

A Parametric Case Study in Radiative Heat Transfer Using the Reverse Monte-Carlo Ray-Tracing With Full-Spectrum k-Distribution Method

2009 ◽  
Author(s):  
Xiaojing Sun ◽  
Philip J. Smith
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Ray Tracing ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Reverse Monte Carlo ◽  
Full Spectrum ◽  
Distribution Method ◽  
Mesh Resolution ◽  
Emitting Media

A combined method of Reverse Monte-Carlo Ray-tracing (RMCRT) with Full-Spectrum k-distribution (FSK) for computing the radiative heat transfer is applied to an extreme non-homogeneous case (both temperature and gas mixture composition vary with positions) with absorbing, emitting media. Parameter Studies of the scaled FSK (FSSK) and correlated FSK (FSCK) methods for the case, such as g point resolution, mesh resolution, reference states and integration quadratures, are carried out. The results from the FSSK and FSCK are only affected by the chosen reference states, and are not sensitive to other parameters.

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