基于改进布谷鸟算法识别瞬态热传导问题的导热系数

基于改进布谷鸟算法反演瞬态热传导问题随温度变化的导热系数.采用Kirchhoff变换将非线性热传导问题转换为线性热传导问题,使用边界元法求解瞬态热传导正问题.将导热系数的反演转化为函数表达式中未知参数的反演,使用改进布谷鸟算法求解未知参数.与共轭梯度法相比,改进布谷鸟算法对迭代初值不敏感;与布谷鸟算法相比,改进布谷鸟算法迭代次数大大减少.数值算例表明对改进布谷鸟算法,增加测点数量迭代次数增加;增加鸟巢数量迭代次数减少;减小测量误差计算结果更精确,同时迭代次数更少.数值算例验证了改进布谷鸟算法反演导热系数的准确性和有效性.     

基于MODTRAN的双查找表法反演高光谱数据的水汽含量

基于MODTRAN辐射传输模型,假设近红外波段地物反射率随波长线性变化,考虑程辐射的影响,发展了一种通过双查找表反演高光谱遥感数据水汽含量的方法。建立查找表过程中,使用三次样条插值方法对查找表水汽含量值加密以减少MODTRAN运行时间。使用两个查找表,通过逐步搜索法对高光谱遥感数据进行水汽反演,得到水汽含量分布图。结果显示,使用三次样条插值方法得到的辐亮度值与MODTRAN计算结果只有0.1%的误差。对两景机载可见光/红外成像光谱仪(AVIRIS)高光谱数据进行水汽反演,得到水汽含量分布图,并用其对辐亮度数据进行大气校正,得到反射率数据。水汽含量分布图变化平缓,无亮/暗点出现,反射率数据在水汽吸收波段的光谱曲线没有过/欠校正现象,这表明水汽反演方法有效。     

二维稳态热传导逆问题初步研究

在用有限控制体积法对二维稳态热传导问题进行成功数值模拟的基础上,首先介绍了处理二维稳态热传导逆问题的两种方法:灵敏度法和伴随方程法;然后分别用这两种方法对一典型的圆环域边界条件反演问题进行了计算,并就测量误差对反演结果的影响做了初步分析.结果表明,灵敏度法和伴随方程法都是求解二维稳态热传导逆问题的有效方法.     

基于数值反演的相对渗透率数据处理方法研究

本文针对一维非稳态岩心驱替过程,利用多孔介质多相流动数值反演算法,提出了对一维非稳态驱替实验进行数据处理的方法。利用该方法,可以在毛细数适中的情况下同时求得毛细压力曲线与相对渗透率曲线,简化了驱替实验的复杂程度;比较了反演方法与JBN方法的准确性与适用性,结果表明在对半经验公式的形式推测合理的前提下,反演方法具有更大的适用范围和更好的准确性。该数据处理方法扩展了非稳态相对渗透率测试的适用范围,避免了JBN方法带来的大毛细数限制。     

基于POLDER数据反演陆地上空气溶胶光学特性

针对利用POLDER数据反演陆地上空气溶胶光学特性和地表反射率进行研究.POLDER探测器能够提供可见光到红外的地气系统反射太阳光的反射率和偏振反射率的多方向数据.发展了一种基于多角度的总反射率和偏振反射率联合反演气溶胶光学参数的算法,根据倍加累加法矢量辐射传输模式构建查找表,反演过程中还考虑了测量数据的云检测处理,气体吸收校正和平流层气溶胶校正,通过865 nm波段总反射率和偏振反射率的模拟计算值和实际测量值的对比实现局部区域的气溶胶光学特性参数和地表反射率分布图的同时反演.并用CNES提供的POLDER气溶胶产品对反演结果进行了验证,该方法能够得到气溶胶光学厚度、折射指数、粒子有效半径和地表反射率较合理的反演结果.     

数值求解瞬态温度场的有限体积法

本文介绍了求解三维瞬态热传导的有限体积法,给出了控制方程和数值方法。通过一些算例对该方法进行了验证,数值试验结果表明该方法计算稳定、可靠。     

基于迭代反演的非磁性材料复介电常数测量及初值选取方法

复介电常数是反映材料宏观电磁性质的重要参数,电磁领域相关材料和器件的选取、设计及应用都必须基于材料在工作频段的电磁参数.数值迭代法是反演计算材料复介电常数的重要方法,但一直存在难以准确给出迭代初始值的问题.本文基于吸波材料介电常数与反射率的关系,提出了一种迭代法反演吸波材料介电常数的初值选取方法,以此为基础构建了一种利用反射参数反演计算单层吸波材料、多层材料中唯一未知层材料复介电常数的方法,并通过实例测试验证了方法的有效性.     

云滴谱分布对FY-4A/AGRI水云光学厚度与有效粒子半径反演的影响

为了定量评估对数正态谱分布假设对水云光学厚度(COT)与有效粒子半径(Re)反演的影响，利用欧洲中期数值天气预报中心建立的RTTOV(Radiative Transfer for TIROS Operational Vertical Sounder)模式，对比模拟了基于对数正态谱和修正Gamma谱两种云滴谱分布下FY-4A/AGRI(Advanced Geosynchronous Radiation Imager)的第2、5通道液态水云的反射率，分析了这两个谱分布假设条件下水云反射率随COT以及Re的变化特征。在此基础上，建立了两种谱分布条件下的COT和Re查算表，并基于2020年夏季的一个初生对流云个例，定量分析了云滴谱分布类型对云参数反演结果的影响。结果表明，在第2通道，两个云滴谱类型假设下计算的反射率仅有0.1%～2%的差异，但在第5通道，采用修正Gamma云滴谱计算的反射率比采用对数正态云滴谱计算的反射率低10%～20%。反演结果表明，采用对数正态云滴谱反演的有效粒子半径Re比采用修正Gamma云滴谱反演的Re整体偏大，前者反演的Re集中在15～35μm,而后者反演的Re集中在...     

共轭梯度法求解多宗量瞬态热传导反问题

提出瞬态热传导反问题中热物性参数和边界条件多宗量反演的一般数值求解模式,导出了敏度计算公式,并用共轭梯度法求解,探讨了测点数目、测量误差和变量初值对反演结果的影响,并进行了数值验证.     

一维量子散射问题的“倒算法”

提出了一维量子散射数值计算的"倒算法",假定透射一侧只有透射波,从透射一侧向入射一侧按初值问题求解薛定谔方程,得到波函数的实部与虚部,进而求出入射一侧的概率密度函数,求出该函数的极大值和极小值,就可以算出透射率和反射率,使一维量子散射的计算简洁明了.用此法研究了散射过程中量子相位的变化,发现在透明点反射波相位有π的跃变.     

气冷涡轮叶片传统热分析中热边界条件的影响

以MarkII气冷涡轮叶片为研究对象,考察了换热系数分布对叶片外表面温度分布的影响。首先分别以温度和换热系数实验值作为热边界条件验证了固体导热计算方法和CFD程序的有效性,然后分析了6种典型热边界条件下的叶片外表面温度分布,并与实验值进行对比。由分析结果可知:叶片外表面温度与换热系数紧密关联,经验关联式(层流、湍流)条件下预测得到的温度偏差较大,当换热系数由能考虑边界层转捩影响的CFD计算得到时,预测得到的温度与实验值较为接近。     

基于微面斜率法的粗糙表面半透明介质层光谱散射特性分析

对具有一维高斯分布粗糙表面的半透明介质层光谱散射,基于微面斜率法建立了考虑遮蔽效应的粗糙表面光谱辐射传递概率模型,采用蒙特卡罗法模拟光谱辐射能束在粗糙表面、半透明介质层介质与镜反射基底之间的多次反射、折射和吸收等传递过程。通过数值模拟,分析了介质层表面粗糙度、光谱光学厚度、折射率和基底反射率对介质层双向反射分布函数(BRDF)的影响。结果表明,表面粗糙程度不同时,反射峰值随入射角度呈现不同的变化趋势;表面粗糙度增加或折射率增大都将导致漫反射份额增大;介质层光谱光学厚度和基底反射率主要影响BRDF的数值大小,而对BRDF的分布形态影响很小。     

水射流冷却过程中表面热流密度的预测

建立了由内部一点测量温度值,选取多个时间步长计算未知的表面热流密度与换热系数的导热反问题算法。该算法采用有限容积法离散方程,附加源项法处理边界条件。将该计算模型应用于求解浸没水射流冷却过程中表面热流密度,将计算温度值与实验测温值进行比较验证了算法的正确性。在此基础上分析了水射流冲击过程中薄钢片表面热流密度随表面温度与时间的变化特性。     

Discrete curved ray-tracing method for radiative transfer in an absorbing-emitting semitransparent slab with variable spatial refractive index

A discrete curved ray-tracing method is developed to analyze the radiative transfer in one-dimensional absorbing-emitting semitransparent slab with variable spatial refractive index. The curved ray trajectory is locally treated as straight line and the complicated and time-consuming computation of ray trajectory is cut down. A problem of radiative equilibrium with linear variable spatial refractive index is taken as an example to examine the accuracy of the proposed method. The temperature distributions are determined by the proposed method and compared with the data in references, which are obtained by other different methods. The results show that the discrete curved ray-tracing method has a good accuracy in solving the radiative transfer in one-dimensional semitransparent slab with variable spatial refractive index.     

太阳辐照对静止水面稳态蒸发的影响

针对低风速下静止水面的蒸发过程,考虑水面与气流的对流传热传质、水体对太阳能辐射的容积内光谱吸收及内部传热,建立分析太阳辐照作用的水面稳态蒸发模型.采用控制容积法结合蒙特卡洛法和谱带模型数值求解水体内部、表面、气流之间的能量传递与质交换.分析空气湿度、温度、流速及正逆温差下,太阳辐照强度对于水面蒸发的影响.结果表明,太阳辐照强度对低风速下静止水面蒸发的影响很大.     

INVESTIGATION OF A QUASI-STEADY LIQUID CRYSTAL TECHNIQUE FOR FILM COOLING HEAT TRANSFER MEASUREMENTS

A quasi-steady technique to simultaneously measure the local heat transfer coefficient and cooling effectiveness on surfaces involving film cooling situations is investigated. The method employs a composite slab consisting of a very thin laminate layer of low-thermal-conductivity material superposed upon a highly conductive metal substrate. The resulting heat transfer in the thin laminate is described by one-dimensional conduction. A very thin coating of thermochromic liquid crystals sprayed onto the surface of the laminate is used in conjunction with a computer image processing procedure to provide local surface temperature data. This information, combined with the substrate and mainstream gas temperatures, provides highly detailed (90 video pixels/cm²) local convection heat transfer distributions. The method is used to conduct flat-plate film cooling experiments consisting of a single row of discrete holes inclined at 35 to the mainstream flow. The local surface temperature is influenced by the combination of two interacting fluid streams at different temperatures. A numerical analysis was performed to assess the assumptions underlying the data reduction procedure. The experimental uncertainty of 7% in the heat transfer coefficient is comparable to prior studies. Furthermore, the uncertainty of 5% in the film cooling effectiveness, coupled with the negligible lateral conduction errors, indicates the present technique offers a unique capability for accurate measurement of the local film cooling effectiveness.     

Effect of heat transfer on the penetration of an electromagnetic pulse into a plasma layer and the inverse skin effect

Penetration of a heating pulse into a plasma layer was studied using the system of coupled nonlinear equations for electric field, electron, and ion temperatures. Numerical calculations of field structure and temperature evolution are performed both in the absence and in the presence of heat transfer. It is established that heat transfer leads to a more rapid penetration of the field near the illuminated surface of the layer and impairs penetration in regions of the layer far from this surface. We found that heat transfer promotes the creation of more favourable conditions for manifestation of the inverse skin effect.     

Inverse estimation of the pulse parameters of a time-varying laser pulse to obtain desired temperature at the material surface

A proper selection of the pulse parameters is essential to achieve desired temperature at the material surface. This leads to obtain the required metallurgical changes in the surface vicinity when a time-varying laser pulse is used in a heating process such as surface modification. In this paper, the conjugate gradient method (CGM) for parameter estimation is successfully applied to estimate the unknown laser pulse parameters for those purposes during laser heating process. The determination of the pulse parameters is treated as a one-dimensional, transient, non-linear inverse heat conduction problem (IHCP). Based on a sensitivity analysis, the inverse problem is solved as an optimization problem comparing a desired temperature at the surface and a calculated one where the objective function is minimized by CGM. The method has been applied to a test case of a heating process on steel, appropriate pulse parameters and desired temperature distribution can also be returned.     

温敏涂料TSP热流密度测量方法及应用

温度敏感涂料（temperature-sensitive paint，TSP）可以实现高空间分辨率的温度测量.基于时间解析温度数据计算热流密度是典型的导热反问题.基于一维双层导热模型，通过解析或数值求解的方法计算热流密度，是上述问题的通用解法.在工程应用中，可根据试验工况简化一维双层导热模型，采用更简便的方法进行热流计算.TSP测量热流的精度受涂料厚度、TSP测温真实位置和材料热物性变化等因素影响，相应地可以在涂料设计、物理建模以及计算方法等方面进行完善，提高TSP热流测量的精度.TSP热流测量在暂冲式和激波式两类高超声速风洞中均已得到成功应用，文章结合两个应用实例对工程应用中的挑战与对策进行了讨论.      

Solution of the inverse radiative load problem in a two-dimensional system

An inverse radiation analysis is presented for estimating the temperature and the heat load distributions of the heating surface from the temperature and the heat flux measurements of the heated object. The Monte Carlo method is employed to solve the direct radiation problem. The inverse radiation problem is solved using the conjugate gradient and singular value decomposition methods. The measured data are simulated by adding random errors to the exact solution of the direct problem. The effects of the measurement errors on the accuracy of the inverse analysis are investigated. The study shows that the heat load distribution of the heating surface can be estimated accurately for the exact and noisy data. And the conjugate gradient method is better than the singular value decomposition method since the former can obtain more accurate results if the measurement errors are the same.