矩形鳍片膜式水冷壁辐射角系数的求解

文中结出矩形鳍片模式水冷壁温度场计算所必需的辐射角系数的求解方法，从而可求出表面热流密度分布的精确群。     

角系数计算的有孔面的有效点识别

为了计算卫星内部的温度,经常需要计算有孔曲面之间的角系数。介绍了角系数计算中所遇到的带孔面的有效点的一种虚设边界面的判别方法,方法巧妙且具有通用性,实际计算结果表明,实际温度与计算温度差小于3℃。     

不同冲角下汽轮机拉筋气动损失系数的计算

采用Fluent软件对装有圆柱拉筋的平面叶栅进行了数值模拟,主要研究了圆柱拉筋引起的平面叶栅气动性能的变化以及叶片冲角对装有圆柱拉筋的平面叶栅的影响,计算了不同冲角下拉筋引起的损失系数,并与前人所做的实验结果吻合较好。结果表明:拉筋促使吸力面的流动分离加剧,使得吸力面附近的流动异常复杂。关于拉筋中心线形成上、下一个高损失涡对,在该处气流欠偏转;而在这个涡对中间的流体马赫数较高,气流呈过偏转。     

单轴自旋平面对固定平面的旋转角系数研究

为了实现表面辐射换热领域转动部件角系数的高精度计算,本文采用蒙特卡洛法建立了单轴自旋平面对固定平面的旋转角系数计算模型。通过与典型自旋平面位置下解析式计算值的比对,验证了物理模型及数值算法的正确性。在此基础上,分析了旋转角度、初始相对位置、发射光线数目等因素对角系数大小和统计标准差的影响。研究表明,当平移矢量不存在-x方向分量时,角系数随旋转角的增大而减小,且平移距离越大,角系数变化范围越小,若Δ(+x)≥0.5,大角度角系数将出现"零值现象";当平移矢量存在-x方向分量时,对于任意非零平移距离Δs,存在非零旋转角αmax使得角系数取得极大值,且两者呈正相关;对于平移距离较大的初始相对位置,适当增大发射光线数目即可获得计算精度高、标准偏差小的理想结果。     

城市屋顶储热特征的观测与分析

利用2005～2006年夏、冬两季南京城市边界层外场试验中湍流通量观测资料,对城市屋顶储热特征进行了初步分析.结果表明:屋顶储热项在地表能量收支过程中的作用明显大于感热和潜热.储热项与净辐射的比值,在夏季白天为0.75,夜间为1.20;冬季白天为0.80,夜间为0.95.并给出了夏、冬两季屋顶储热项参数化方案OHM(Objective Hysteresis Model)的拟合系数,与相关研究结果比较表明,所得系数能较好地反映南京地区屋顶的储热特征.     

APPLICATION OF IMPLICIT NUMERICAL TECHNIQUES TO THE SOLUTION OF THE THREE-DIMENSIONAL DIFFUSION EQUATION

Implicit techniques for calculating three-dimensional, time-dependent heat diffusion in a cube are tested with emphasis on storage efficiency, accuracy, and speed of calculation. For this purpose, a tensor product technique with both Chebyshev collocation and finite differences and a generalized conjugate gradient technique with finite differences are used in conjunction with Crank-Nicolson discretization. An Euler explicit finite difference calculation is performed for use as a benchmark. The implicit techniques are found to be competitive with the Euler explicit method in terms of storage efficiency and speed of calculation and offer advantages both in accuracy and stability. Mesh stretching in the finite difference calculations is shown to markedly improve the accuracy of the solution.     

GREEN'S FUNCTION SOLUTION TO HEAT TRANSFER OF A TRANSPARENT GAS THROUGH A TUBE

A heat transfer analysis of a transparent gas flowing through a circular tube of finite thickness is presented. This study includes the effects of wall conduction, internal radiative exchange, and connective heat transfer. The natural mathematical formulation produces a nonlinear, integrodifferential equation governing the wall temperature and an ordinary differential equation describing the gas temperature. This investigation proposes to convert the original system of equations into an equivalent system of integral equations. The Green's function method permits the conversion of an integrodifferential equation into a pure integral equation. The proposed integral formulation and subsequent computational procedure are shown to be stable and accurate.     

生物质灰渣对甲基橙废水的去除性能及机制

为将资源化生物质灰渣用于甲基橙(MO)废水的处理,在明确MO初始浓度、pH值、反应时间和温度影响的基础上,探讨MO去除的潜在机制和效果提升途径.结果表明,MO的去除随MO初始浓度的增加而增加,并在80mg/L时趋于平衡.pH值为2时有利于吸附的进行,且MO去除在12 h内较为迅速,24 h后趋于平衡.Langmuir模...     

USE OF GCG METHODS FOR THE EFFICIENT SOLUTION OF MATRIX PROBLEMS ARISING FROM THE FVM FORMULATION OF RADIATIVE TRANSFER

Preconditioned generalized conjugate gradient (GCG) iterative methods are applied to the solution of large, sparse, and unsymmetric linear algebraic equations resulting from the application of the finite-volume method to the problem of radiative heat transfer in an absorbing, emitting, and scattering gray medium, with the boundary surfaces reflecting radiation in both diffuse and specular regimes. The governing radiative transfer equation, which is a complicated integro-differential equation, has been discretized using the S N finite-volume method (FVM). Different variants of GCG methods have been tested on a problem of 2-D radiation in a cylinder, and efficiencies of the methods have been compared. Numerical results indicate that preconditioning suggested in the article dramatically improves the performance of the GCG methods. Results on test problems based on S 8 FVM agree well with exact results reported in the literature.     

非标条件下太阳电池短路电流向标准条件下的转化

分析了在太阳电池测试过程中，模拟器的光谱失配、光强、太阳电池的光谱响应和测试时太阳电池PN结温度这四个因素共同对测试结果的影响。找到了太阳电池在非标准测试条件下测试结果向标准测试条件下转换的一般方法。给出诸多实验，并确定该种转换方法中的一些经验参数。     

水域边界上存在点源流动的相似性解的一种求解方法

从流体力学复位势出发，对水域边界上存在点源流动问题给上似变量及相似性解，导出了相似函数所满足的常微分方程及边界条件，该方法物理概念清晰，结果简明，对水利资源 的扩散问题有理论参考及工程应用意义 。     

1961—2017年黄河源区日照时数变化趋势响因子分析

利用黄河源区7个气象站1961—2017年的日照时数、平均总云量、降水日数、相对湿度等地面气象观测资料,对近57年黄河源区日照时数的变化趋势及影响因子进行分析。发现黄河源区年日照时数的空间分布呈北多南少的特点,位于北部的玛多、兴海日照时数最多,而位于南部的久治、红原最少;各季节日照时数的空间分布特征与年日照时数相似。黄河源区日照时数的年际变化表现为兴海、红原的年日照时数呈下降趋势,下降趋势分别为-28.6 h/10 a、-18.4 h/10 a,其余各地均呈上升的趋势,玛多上升趋势最明显,为22.4 h/10 a。黄河源区日照时数的月际变化表现为明显的三峰二谷的特征,4、8、11月份为3个高值时段,6、9月份为2个低值时段,其中9月份日照时数为全年最低。周期分析结果表明：黄河源区日照时数的周期变化主要以2 a、4~6 a、10~13 a和22~30 a周期为主。源区日照时数和平均总云量、降水日数、相对湿度呈明显的负相关;空间分布上随总云量、降水日数、相对湿度自南向北的减少日照时数明显增多;日照时数与总云量的相关性最好,尤其季节总云量的变化对年日照时数的变化影响最敏感。源区总云量与日照时数在空间分布上恰好相反。降水日数、相对湿度的减少也是源区日照时数增加的一个重要原因。黄河源区太阳能资源丰富,且黄河源头—吉迈区间日照时数呈持续增加的趋势,有利于太阳能资源的开发和利用。     

TWO-DIMENSIONAL TRANSIENT NATURAL CONVECTION IN A REPETITIVE GEOMETRY SUBMITTED TO VARIABLE HEATING FROM BELOW: NUMERICAL IDENTIFICATION OF ROUTES LEADING TO CHAOS

Two-dimensional transient natural convection in a horizontal channel periodically heated from below with a temperature varying sinusoidally with time and containing rectangular adiabatic blocks periodically distributed on its lower wall is studied numerically. Parameters of the problem are the Rayleigh number (Ra), the amplitude of the variable temperature, and its temporal period. By considering air (Pr 0.72) as a working fluid and maintaining the geometrical parameters constant, different routes leading to chaos are identified by progressively varying the influencing parameters.     

NORMALIZED STRESS INTENSITY FACTOR RANGE SOLUTIONS OF AN INNER-SURFACE CIRCUMFERENTIAL CRACK IN THIN- TO THICK-WALLED CYLINDERUNDER THERMAL STRIPING BYSEMI-ANALYTICAL NUMERICAL METHOD

The normalized stress intensity factor (SIF) range of an inner-surface circumferential crack in a thin to thick-walled finite-length cylinder under thermal striping was considered in this paper. The edges of the cylinder were rotation-restrained and the outer surface was adiabatically insulated. The inner surface of the cylinder was heated by a fluid with sinusoidal temperature fluctuation. An analytical temperature solution for the problem and our semianalytical numerical SIF evaluation method for the crack were combined and, as a result, it was shown that the transient SIF solution can be expressed in a generalized form by dimensionless parameters such as mean-radius-to-wall-thickness ratio, Biot number, normalized striping frequency, and Fourier number. Finally, normalized SIF ranges for the first cycle and steady state were given for these dimensionless parameters in tables for mean-radius-to-wall-thickness ratio of 10, 5, and 1.