CFD与Matlab方法优化亚音速航空电光系统气动光学效应

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本文主要探讨了亚音速空中电光系统(aero-optic effects of subsonic airborne electro-optical system)的评估方法，作者是 Yin Kexin 和 Jiang Huilin，发表于2006年8月10日的《中国光学学会》。他们提出了一种基于计算流体动力学(CFD)代码和MATLAB的简化评估策略。这种方法的核心在于通过CFD模拟计算出空气密度波动，这些波动受到诸如高度、速度、设备位置以及波长等因素的影响。这些波动数据被作为输入导入到MATLAB中进行进一步的分析。研究结果显示，为了优化电光系统(EO system)的性能，有几个关键因素需考虑。首先，随着海拔的增加，系统的稳定性通常会有所改善，因为较高的高度有助于减小大气湍流的影响。其次，为了最小化光学失真，建议尽可能地减缓飞行速度，因为高速可能会加剧气流对光学系统的扰动。设备的位置也对性能有显著影响，放置在飞行平台前端（即靠近气流边界）可以降低风阻引起的波动，从而提高系统的分辨率和对比度。论文指出，对于特定的波长，当同时考虑系统的对比度和分辨率时，存在一个最佳工作条件。通过数值模拟，作者验证了这种方法的有效性，证明了通过调整这些参数，可以显著提升电光系统的整体性能。研究使用的光学科学与应用的OCIS分类代码包括010.1330（光学仪器和系统），010.3310（光学工程中的光学波动和湍流），以及000.4430（光学测量和传感技术）。总结来说，这篇论文提供了一个实用的工具，用于预测和优化亚音速空中电光系统在实际飞行环境中的性能，通过精确控制空气动力学影响和设备布局，可以在保证系统稳定性和精确度的前提下，有效地提高其效能。这对于设计和改进现代航空电子设备，特别是在高精度成像和导航系统方面具有重要的理论指导意义。

August 10, 2006 / Vol. 4, No. 8 / CHINESE OPTICS LETTERS 435

Evaluations on aero-optic effects of subsonic airborne

electro-optical system

Kexin Yin (



) and Huilin Jiang (



)

Changchun University of Science and Technology, Changchun 130022

Received February 24, 2006

A simple method based on CFD code and Matlab for aero-optic effects is presented. Density fluctuation

from CFD code due to the changes of such factors as altitude, speed, equipment location, and wavelength

is introduced as an input to Matlab. The overall calculations are in Matlab. The results show that the

p erformance of electro-optical (EO) system can be improved when the altitude increasing, the speed is as

slo w ly as possible, and the equipment location moves to the leading edge of the airborne platform as far

as possible, for the wavelength there is an optimum one when the indexes of contrast and resolution of the

system are both considered. All of these methods can minimize the optical aberrations. Several numerical

simulations demonstrate the method.

OCIS co des: 010.1330, 010.3310, 000.4430.

When an otherwise-collimated laser beam passes through

a turbulent flow with variable index of refraction, its

wavefront becomes dynamically aberrated. These aber-

rations degrade the beam’s ability focused on the far

field, so reducing the system utility of the beam that

may be used for communication. When the laser plat-

form is an aircraft, one of the causes of beam degradation

is the thin layer and immediate air flow around the air-

craft, which is referred to the aero-optic effects (see Fig.

1). It is necessary to quantitatively evaluate these degra-

dations for correct and reliable airborne electro-optical

(EO) system. A wide variety of different methods have

been developed for aero-optical measurements. Daniel

[1]

applied a Shack Hartman wavefront sensor to measure

the optical distortions caused by the density fluctuation.

Jiang

[2]

introduced a novel two-dimensional (2D) Hart-

man wavefront sensor to measure aero-optic effects when

the b eam passes through a low velocity heat turbulent

jet. The wind tunnel tests have been made successfully

in American since 1980s’ and until recently American

and Israel have cooperated to develop an “arrow” missile

that solved a series o f aero-optical problems and suc-

ceeded in the flying test

[3]

.Jumperet al. have demon-

strated a small aperture beam technique (SABT) for

quantifying the optical wavefront distortions imposed by

passing through the turbulent flow field

[4]

. The studies

of aero-optic field in China originated from 1990s’ and

made great progress, the investigative emphasis has b een

gradually transferred from the initial understanding of

aero-optical statistical characteristics to the mechanism.

Fig. 1. Schematic of TBL adhere to the airborne platform.

Though some facilities or techniques have been devel-

oped to test aero-optical wavefront distortions

[5−8]

,the

advances in aero-optical computational simulations have

not come as rapidly. The computational simulations play

a vital, complementary role in test planning as well as test

data interpretation. This paper introduces a simple com-

putational simulation methodology for evaluating aero-

optic effects around subsonic airborne EO system based

on the combination of CFD code and Matlab. Several

numerical simulations that demonstrate the method are

presented. The results show that the proposed method

can easily assess the aero-optic effects around airborne

EO system and make useful predictions or corrections.

Density fluctuation is a key parameter for evaluat-

ing aero-optic effects in aerodynamic flow field. In

the present study, we use FLUENT

[9]

to produce den-

sity fluctuation. FLUENT is a m ultiblock CFD code,

which can solves the three-dimensional (3D) Navier-

Stokes equations. Here flow is turbulent and a regular

k-ε model is chosen as current flig ht conditions. Several

parameters such as altitude (affects pressure and density)

and Mach number must b e s pecified in FLUENT simula-

tion. Then the turbulent effects are calculated based on

turbulent model. The output data of FLUENT code are

a discrete set of air density values on an unstructured grid

and are resolved in a fluid density file for later use. In

this paper we use ICEM CFD 4.1.3 mesh generator that

is a multiblock grid generator to produce computational

mesh and we make sure that the grid around the win-

dow is dense enough. With the comprehensive studies,

it has been found that the density fluctuation in turbu-

lent boundary layer (TBL) is determined by the density

difference (between wall density and free stream density)

that comes from the flow velocity variations due to the

increases of the temperature and the fluid speed in the

boundary layer. We have an assumption that the density

discontinuity occurs in TBL, the peak density is in the

middle of overall TBL, and its average value is 10% of

this density difference, defined by

[10]



average

∼



∼

|ρ

− ρ

|×10%, (1)

where ρ

is wall density and ρ

is free stream density.

1671-7694/2006/080435-04 http://www.col.org.cn

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