OCS4格式的数值边界格式及其渐近稳定性

 根据多项式拟合数值边界格式(SFEBS)和Taylor展开数值边界格式(TEBS)相结合的思想,构造了与优化3对角4阶跳点紧致差分格式(OCS4)及其插值格式(OCI4)相匹配的具有4阶精度的数值边界格式(SF-TEBS4).通过计算格式特征值的理论分析表明,OCS4、OCI4格式在与数值边界格式SF-TEBS4格式相结合时,数值格式在整体上能够满足渐进稳定性的要求.一阶导数数值试验表明,OCS4、OCI4与4阶数值边界格式SF-TEBS4在数值模拟中相结合使用时,能够保证格式整体精度达到4阶,且计算误差较小;行波解数值模拟表明,这些格式的组合能够有效抑制数值计算的误差,具有能够长时间保持群速度和较强渐进稳定性的特性.理论分析和数值算例均表明,SF-TEBS4与OCS4和OCI4相结合,能够很好地求解小尺度波动问题.     

Taylor-Hadamard乘积的q-级和q-型

通过构造Taylor-Hadamard乘积,讨论了泰勒级数的增长性,获得了此Taylor-Hadamard乘积与原泰勒级数关于q-级和q-型的几个关系定理,并给出相应的例子说明了结果的正确性.     

Critical condition for the transformation from Taylor cone to cone-jet

An energy method is proposed to investigate the critical transformation condition from a Taylor cone to a cone-jet.Based on the kinetic theorem, the system power allocation and the electrohydrodynamics stability are discussed. The numerical results indicate that the energy of the liquid cone tip experiences a maximum value during the transformation.With the proposed jetting energy, we give the critical transformation condition under which the derivative of jetting energy with respect to the surface area is greater than or equal to the energy required to form a unit of new liquid surface.     

A localised dynamic closure model for Euler turbulence

ABSTRACT

In this work, we present a localised form of the dynamic eddy viscosity model for computationally efficient and accurate simulation of the turbulent flows governed by Euler equations. In our framework, we determine the dynamic model coefficient locally using the information from neighbouring grid points through a test filtering process. We then develop an optimised Gaussian filtering kernel, using a consistent definition with respect to the test filtering ratio, which gives full attenuation at the grid cut-off wave number. A systematic a-posteriori analysis of our model is performed by solving two 3D test problems: (i) incompressible Taylor–Green vortex flow and (ii) compressible shear layer turbulence induced by Kelvin–Helmholtz instability to show the wide range of applicability of the proposed localised dynamic model. We demonstrate that the proposed dynamic model is robust and provides a better estimation of the inertial range turbulence dynamics than other numerical models tested in this study.     

低煤级煤生烃与结构演化的耦合机理研究

应用傅里叶变换红外光谱(FTIR)、热解气相色谱(GC)对低煤级煤生烃过程中有机质结构演化进行表征,剖析了人工热演化过程中气态烃产率,解析了煤结构官能团的变化规律,揭示了低煤级煤生烃与结构演化的耦合机理。结果表明：煤热模拟产物主要为气态烃C_1-5,甲烷生成瞬时产率包含四个峰值,低煤级煤化学结构中含氧官能团和烷基侧链随煤化程度的增高以不同的速度发生脱落,随煤级的增加,其芳构化程度增大。分别对煤结构中的脂肪烃甲基、CO基、芳香烃芳核CC和烷烃结构上甲基、亚甲基进行表征。存在420 ℃温度转折点,之前吸收峰强度逐渐减小,之后又略有增大,揭示了低煤级煤三个主要结构演化阶段煤化作用机理,提出了低煤级煤生烃结构演化模式图。     

On the time development of dispersion in electroosmotic flow through a rectangular channel

This is an analytical study on the time development of hydrodynamic dispersion of an inert species in electroosmotic flow through a rectangular channel.The objective is to determine how the channel side walls may affectthe dispersion coefficient at different instants of time.Tothis end,the generalized dispersion model,which is valid forshort and long times,is employed in the present study.Analytical expressions are derived for the convection and dispersion coefficients as functions of time,the aspect ratio ofthe channel,and the Debye-Hu¨ckel parameter representingthe thickness of the electric double layer.For transport ina channel of large aspect ratio,the dispersion may undergoseveral stages of transience.The initial,fast time development is controlled by molecular diffusion across the narrowchannel height,while the later,slower time development isgoverned by diffusion across the wider channel breadth.Fora sufficiently large aspect ratio,there can be an interludebetween these two periods during which the coefficient isnearly steady,signifying the resemblance of the transportto that in a parallel-plate channel.Given a sufficiently longtime,the dispersion coefficient will reach a fully-developedsteady value that may be several times higher than that without the side wall effects.The time scales for these periods oftransience are identified in this paper.     

基于Taylor变换法的转子系统非线性动力学特性

在考虑了非线性油膜力的基础上,建立了转子系统的非线性动力学模型,引入了求解非线性微分方程的Taylor变换法,并将转子振动系统原分析模型变换为离散域内的代数方程组,采用Taylor变换法,对第一跨转子振动系统动力学特性进行非线性分析,求得转子系统的响应,找出转子系统的分岔规律,用分岔图、频谱图、庞加莱映射、轴心轨迹等多种方法表现了转子系统的非线性现象,结果表明考虑油膜力影响后,转子系统的运动状态随转速增加由周期至二倍周期再至周期再至拟周期,或者经周期运动直接至混沌运动·     

高校教师晋升职称评审体系数字化方案研究

利用计算机算法程序,构建一套实际工作与专家评判相结合的计算机评审方案。在评审过程中,即考虑了申报者的工作情况,又充分听取了专家的意见。     

向量函数的Taylor展开式探讨

主要剖析教材[2]和[3]中关于向量函数的Taylor展开式与收敛问题,指出一些存在问题,并提出利于教与学的见解.     

Peak parking method for measurement of molecular diffusivity in liquid phase systems

The combination of series of measurements of band broadening made with the peak parking (PP) method, using successively an open capillary tube and a HPLC column, gives a convenient procedure for the measurement of the molecular diffusivity (D_m) of compounds in solutions, of their axial dispersion coefficient (D_ax,m) in chromatographic columns, and of the tortuosity or obstructive factor of the column bed. The molecular diffusivity measured for benzene in methanol was in excellent agreement with literature data. The ratio of the axial dispersion coefficient to this diffusivity gives the obstructive factor (γ_m) of the packed bed, which was 0.74 for the column used. The values of D_m in other solutions were obtained from the D_ax,m values measured by the PP method, by correcting the D_ax,m values with the γ_m value. The D_m values determined by this method were in good agreement with those previously reported or estimated using literature correlations. These results showed that the PP method is effective for the experimental measurement of D_m.