Characterization of countercurrent liquid-upward and solid-downward fluidized system

Acting as an operating mode of fluidization, the flow characteristics of a countercurrent liquid–solid fluidized bed (CCLSFB) were experimentally investigated using a Plexiglas column of 1.5 m in height. Countercurrent liquid-upward and solid-downward fluidization was achieved under a limited solid flowrate before flooding occurred.The “flooding” phenomena and the flooding velocity were identified by measuring the variations in pressure drop in the axial direction of the column. Two different methods were used to quantify the flooding point that led to the instability of the system. Axial solids holdup profiles were also obtained from the pressure drop data along the column and the influences of device structure and operating conditions on the solids holdup were also studied. Seven types of particles with different diameters and densities were used. An agreement was found between the experimental results and the mathematic prediction derived from the Richardson–Zaki equation on the data of the solids holdup.     

Numerical simulation and convergence analysis of a high-order conservative difference scheme for SRLW equation

Coupled with the Richardson extrapolation, a new conservative Crank–Nicolson finite difference scheme, which has the accuracy of O(τ²+h⁴)$O({\tau }^2+h^4)$ without refined mesh for the symmetric regularized long wave equation is proposed. The corresponding conservative quantities are discussed, and the existence of numerical solution is proved by the Browder fixed point theorem. The convergence, unconditional stability and uniqueness of the scheme are also derived using the energy method. Numerical results are given to verify the accuracy and the efficiency of proposed algorithm.     

网箱养殖大黄鱼弧菌病研究

1999年夏季,福建省宁德北斗都网箱养殖大黄鱼发生大面积死亡,从病鱼体内分离出两株细菌：ND-01和ND-02,人工感染试验证实这两株菌皆为大黄鱼的病原菌,经鉴定,菌株ND-01为溶藻弧菌,菌株ND-02为副溶血弧菌,51种药物的药敏试验表明;青霉素G、万古霉素等19种药物对ND-01没有抗菌作用,青霉素G、头孢拉定等10种药物对ND-02没有抗菌作用;ND-01对氯霉素、氟派酸等9种药物敏感,而ND-02则对氟派酸、氟嗪酸等10种药物敏感。     

养殖密度和温度对瓦氏黄颡鱼幼鱼生长影响实验研究

研究了养殖密度和温度对瓦氏黄颡鱼幼鱼在设施养殖中生长的影响.分别设置5个养殖密度(80、160、240、320和400ind/m3)和5个温度(18℃、22℃、26℃、30℃和自然水温),经过30 d的养殖试验发现养殖密度和温度对瓦氏黄颡鱼幼鱼在设施养殖中的摄食和生长都有显著影响.日增重、特定增长率、生长效率、摄食效率随密度的增大而减小,净增重240和160ind/m3两密度组最高;随着温度的升高,日增重、特定增长率、生长效率均呈现先升高后下降的趋势,其中26℃组生长最快,摄食效率则随温度的升高而增大.特定生长率与密度之间存在显著负线性相关,其关系式为:SGR=2.4328-0.0041SD(r2=0.9948);养殖温度和特定增长率之间存在显著二次曲线相关,其回归方程式为:SGR=-0.0049T- 0.2669T-1.7871(r2=0.9645),当水温为27.2℃,瓦氏黄颡鱼幼鱼的特定增长率为最大1.847,表明瓦氏黄颡鱼幼鱼最适生长水温应在26～29℃之间.     

高维理查森外推算法的研究和应用

在理查森外推法算法的基础上,提出了广义理查森外推法算法,在此基础上构造了高精度高阶导数的数值计算法,实验结果表明,该算法的有效性.     

非线性Fredholm积分方程迭代Galerkin解的渐近展开及其外推

讨论了一维非线性Fredholm积分方程迭代Galerkin方法，证明了迭代Galerkin解的误差可展开为h的偶次幂，且首项为h^2p。从而可进行Richardson外推，提高数值解的精度。同时我们还给出了数值例子，数值计算结果与理论预测相符。     

Assessment of numerical uncertainty for the calculations of turbulent flow over a backward‐facing step

Numerical uncertainty analysis has been performed for the turbulent flow past a backward‐facing step. The analysis is based on calculations on seven non‐rectangular, but structured, grid sets that were provided by the organizers of the 2004 Lisbon Workshop (Proceedings of the Workshop on CFD Uncertainty Analysis, Lisbon, 21–22 October 2004). The calculations were performed by using a commercial code, namely, FLUENT with the Spalart–Allmaras one‐equation turbulence model. The present study constitutes a calculation verification process: a set of partial differential equations are solved on gradually refined grid sets, the selected quantities are extrapolated, and then the overall numerical uncertainty in selected quantities is estimated by various methods. Some new ideas are presented for estimating the coefficient of variation, which is related to standard deviation (or standard error of estimate in case of the least squares method). The major problem that stands out in extrapolation is the cases of non‐monotonic convergence. For such cases some alternative methods are proposed, and the results are compared to assess these methods. Copyright © 2005 John Wiley & Sons, Ltd.     

The thermoconvective instability of plane poiseuille flow heated from below: A proposed benchmark solution for open boundary flows

The transient two-dimensional Navier-Stokes and energy equations have been solved numerically for flow in a horizontal channel heated from below in the Boussinesq limit. For the set of dimensionless parameters chosen, the flow consists of periodic transverse travelling waves resulting from a convective instability. The solution is proposed as a benchmark for the application of outflow boundary conditions (OBC) in time-dependent flows with strong buoyancy effects. Richardson extrapolation in both time and space is used in obtaining the solution. Field plots and profiles of velocity, temperature, vorticity and streamfunction at selected axial positions and times are also presented from the finest grid and smallest time step calculation. The calculations have been made on an extended domain so that the effects of OBC used in the present study would be negligible in the test region.     

Enhancement of turbulence in a stratified fluid by the presence of a shear field

Time-dependent solutions are obtained for turbulent flow in a stratified fluid in the presence of a shear field. Within the stated closure assumptions, it is shown that for certain shear fields that the turbulent intensity is enhanced.     

Richardson Elements for Parabolic Subgroups of Classical Groups in Positive Characteristic

Let G be a simple algebraic group of classical type over an algebraically closed field k. Let P be a parabolic subgroup of G and let be the Lie algebra of P with Levi decomposition , where is the Lie algebra of the unipotent radical of P and ł is a Levi complement. Thanks to a fundamental theorem of Richardson (Bull. London Math. Soc. 6:21–24, 1974), P acts on with an open dense orbit; this orbit is called the Richardson orbit and its elements are called Richardson elements. Recently Baur (J. Algebra 297(1):168–185, 2006), the first author gave constructions of Richardson elements in the case for many parabolic subgroups P of G. In this note, we observe that these constructions remain valid for any algebraically closed field k of characteristic not equal to 2 and we give constructions of Richardson elements for the remaining parabolic subgroups. Presented by Peter Littelmann.