基于均匀化理论的多孔板弯曲问题新解

由于密集型分布孔的存在,通常的有限元法不能有效地分析多孔板的弯曲问题.该文基于均匀化理论建立了该类问题的新解法.对含密集型分布的阶梯型圆孔板的分析结果,说明了该文方法是有效的.     

Homogenization-based method for bending analysis of perforated plate

Owing to the existence of distributed holes, it is difficult to solve the bending problem of perforated plates by the conventional finite element method. A homogenization-based method for this problem is presented in this paper. As an example, the bending analysis of a circular perforated plate with distributed step-wise cylindrical holes is made. The deflection and the fundamental frequency obtained by present method are in good agreement with experimental data, this implies that the method is effective. This project is supported by the National Natural Science Foundation (19602007) and National Outstanding Youth Foundation (19525206).     

Inverse doubly periodic problem of the theory of bending of a plate with elastic inclusions

Based on the balanced strength principle, a problem of determining the optimal interference for fitting elastic inclusions into holes of an isotropic elastic plate weakened by a doubly periodic system of circular holes is solved. A closed system of algebraic equations is derived, which allows solving this problem. The resultant interference increases the load-carrying capacity of the composite plate being bent. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 4, pp. 153–161, July–August, 2006.     

Measurement and Modelling of Gas Condensate Flow Around Rock Perforation

In the petroleum production industry wells are mostly cased and perforated in the producing formation. Perforation characteristics such as size, length, number of perforation tunnels and their arrangements as well as fluid and rock properties determine fluid flow behaviour in the wellbore region, hence, well productivity. Flow of gas and condensate around a perforation tunnel (including the damaged zone) has been studied by performing steady-state core experiments and simulating the results numerically, using a finite element modelling approach. The model allows for the changes in fluid properties and accounts for the coupling of the two phases and the inertial effect using a fractional flow based correlation. The results indicated that different sets of thickness-permeability (h−k) values obtained from matching single-phase flow performance could be assigned to the damaged zone around perforation to represent the two-phase flow performance. The status of the tip of the perforation for two extreme cases of totally closed and fully open was investigated and found to have a minimal effect on the performance of the system.     

Topology optimization of multi-purpose structures

Whilst most of the literature on topology optimization of structures deals with so-called selfadjoint problems involving highly idealized, single-purpose structures, this paper discusses topology optimization of multi-purpose structures which concerns nonselfadjoint problems. General methods based on the so-called layout theory, application to trusses and perforated plates and computational difficulties are discussed.     

开孔簿板非线性分析的数学模型和广义变分原理*

基于薄板非线性弯曲的Kirchhoff-Kármán假设.本文提出了在任意中面边界条件下任意开孔薄板非线性分析的三类边值问题并建立了相应的广义变分原理.能够看到在本文中提出的数学模型完全是一种新的不同于Karman理论的模型.这些数学模型能够应用于任意中面边界条件下开孔薄板的非线性分析和稳定性分析.     

两种不同气体中的高速爆燃波及其向爆轰的转变

对2C2H2 5O2及2C2H2 5O2 80%Ar两种可燃混合气体中的高速爆燃波及其向爆轰的转变过程进行实验研究.高速爆燃波由孔栅干涉爆轰波的方法直接生成,观测手段则以高速转鼓摄影获取孔栅近场流场x-t纹影图,以传感器追踪波面的后继发展.研究发现,两种气体中的爆燃波具有迥异的特性.前者燃烧波面在较低初压条件下为层流结构,而较高初压下为湍流结构,向爆轰转变点可以延伸至下游较长距离;后者在不同初压条件下燃烧波面无明显差异,爆轰的再次形成只能在孔栅下游近场内建立.两种气体中高速爆燃波的维持和爆轰转变过程均非纯粹激波压缩所致,湍流输运在其中起着必不可少的作用.分析显示,激波压缩效应对纯氧炔气体的高速爆燃和DDT贡献较小,湍流输运占主导地位;而氩气稀释气体较为稳定,缺乏自行衍生剧烈湍流燃烧的能力,因而激波压缩和外界扰动对其高速爆燃传播和爆轰转变起十分重要的作用.     

Separation of Scales and Almost-Periodic Effects in the Asymptotic Behaviour of Perforated Periodic Media

We study the asymptotic behaviour of highly oscillating functionals in finely perforated domains, when the periods of the oscillation and of the perforation may be at different scales. We highlight two types of regimes: in the first one we have separation of scales and the two process superimpose. In the second one the scales interact in a periodic or almost-periodic fashion; as a consequence we may not have a unique limit behaviour.     

Investigation of Thermal Performance of Perforated Finned Heat Exchangers

In this study, the thermal performance of perforated finned heat exchangers with angle of rotation θ was experimentally investigated. Six-millimeter-diameter holes that were opened on each circular fin on a heating tube have a potential to reduce the thickness of the boundary layer that is formed on the circular fins placed on the heating tube, thus increasing heat transfer through convection in this area. The experiments were carried out at six different angular locations to determine the best angular location. In addition, a perforated finned heater was compared with an imperforate finned heater. For the finned heater at 60°, the effectiveness is 18% higher and the pressure drop is 1.16% lower than other angular positions. In this respect, it can be concluded that the best angular position is 60°. In addition, results show an increase in effectiveness with an increasing number of transfer units.     

Nucleation of cracks in a perforated fuel cell

A mathematical model is constructed for crack nucleation in an isotropic fuel cell (heat-releasing solid material) attenuated by a biperiodic system of cooling cylindrical channels with a circular cross section. Cracks are assumed to appear with increasing heat-release intensity in the bulk of the material. The solution of the problem on equilibrium of an isotropic perforated fuel cell with crack nuclei reduces to the solution of a nonlinear singular integral equation with a Cauchy-type kernel. The solution of the latter equation yields the forces in the band of crack nucleation. The condition of crack nucleation is formulated with allowance for the criterion of ultimate extension of bonds in the material. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 121–133, September–October, 2007.