一种基于修正西原模型的冻土蠕变本构关系

冻土在高应力水平下通常会表现出加速蠕变特性。经典西原（Nishihara）模型可以反映衰减蠕变和稳态蠕变,但不适用于描述加速蠕变。通过对Nishihara模型中黏性元件进行修正,将黏弹性元件中的定常的黏滞系数修正为时间的函数,并在黏塑性元件中采用非定常、非牛顿黏性元件,得到的蠕变柔量可以考虑应力水平和时间的影响,使其能够反映其加速蠕变的过程。用提出的模型分别对一维和三维应力、不同应力水平下的冻土蠕变试验数据进行了拟合,拟合结果能够反映冻土从衰减蠕变和稳定蠕变状态进入加速蠕变的过程,说明了该模型对于描述冻土在不同应力下不同蠕变状态的适用性。     

The effects of vertical viscosity coefficients with different distribution characteristics on classical Ekman spiral structure

The classical Ekman theory tells us that the ocean surface current turns to the right(left) side of wind direction with 45° in the north(south) hemisphere,but the observation and research results show that the surface current deflexion angle is smaller than 45° in the Arctic and high latitude areas while larger than 45° in the low latitude areas.In order to explain these phenomena,a series of idealized numerical experiments are designed to investigate the influence of vertical viscosity coefficients with different vertical distribution characteristics on the classical and steady Ekman spiral structure.Results show that when the vertical viscosity coefficient decreases with water depth,the surface current deflexion angle is larger than 45°,whereas the angle is smaller than 45° when the vertical viscosity coefficient increases with water depth.So the different observed surface current deflexion angles in low latitude sea areas and the Arctic regions should be attributed to the different vertical distribution characteristics of vertical viscosity coefficients in the upper ocean.The flatness of the Ekman spiral is not equal to one and does not show regular behaviors for the numerical experiments with different distribution of vertical viscosity.However,the magnitudes and directions of volume transport of Ekman spirals are almost the same as the results of classical Ekman theory,i.e.,vertical viscosity coefficient distributions have no effect on the magnitudes and directions of volume transport.     

三维地震波速结构约束下的变黏度地幔对流及其动力学意义

建立了三维黏度扰动下的变黏度地幔对流模型,并提供了在引入地幔的三维地震波速度结构下相应的求解方法. 依此反演了瑞利数Ra = 106时,两种不同边界条件下的极、环型场对流图像,这有助于深化对地幔物质流动和大地构造运动的深部动力学过程的认识和理解. 研究结果表明,不但地幔浅部的极型场对流图像显示出了与大地构造运动的相关性并揭示了其深部动力学过程,更重要的是,地幔浅部的环型场对流图像首次为我们认识和理解板块构造的水平与旋转运动提供了重要的信息：环型场速度剖面中在赤道附近存在一条大致南东东—北西西向的强对流条带,可能与环赤道附近大型剪切带的形成相关,进而表明可能是该带强震发生的深部动力学背景;在南北半球存在的旋转方向相反的对流环表明它们整体上可能存在差异旋转.     

Transitions in thermal convection with strongly temperature-dependent viscosity in a wide box

Numerical models are systematically presented for time-dependent thermal convection of Newtonian fluid with strongly temperature-dependent viscosity in a two-dimensional rectangular box of aspect ratio 3 at various values of the Rayleigh number Ra_b defined with viscosity at the bottom boundary up to 1.6×10⁸ and the viscosity contrast across the box r_η up to 10⁸. We found that there are two different series of bifurcations that take place as r_η increases. One series of bifurcations causes changes in the behavior of the thermal boundary layer along the surface boundary from small-viscosity-contrast (SVC) mode, through transitional (TR) mode, to stagnant-lid (ST) mode, or from SVC mode directly to ST mode, depending on Ra_b. Another series of bifurcations causes changes in the aspect ratio of convection cells; convection with an elongated cell can take place at moderate r_η (10³–10^5.5 at Ra_b=6×10⁶), while only convection of aspect ratio close to 1 takes place at small r_η and large r_η. The parameter range of r_η and Ra_b for elongated-cell convection overlaps the parameter range for SVC and ST modes and include the entire parameter range for TR mode. In the elongated-ST regime, the lid of highly viscous fluid along the top boundary is not literally ‘stagnant’ but can horizontally move at a velocity high enough to induce a convection cell with aspect ratio much larger than 1.     

磁化水—膨润土浆液流变特性的实验研究

摘要：对不同磁化条件下产生的磁化水进行了配浆实验,并对磁化水—膨润土浆液的流变参数进行了测定和分析。讨论了磁化水降粘、降切的机理     

油田聚合物产出液黏度的影响因素

三次采油含聚污水中残留HPAM的含量体现在采出液的黏度上,直接影响到含聚污水的处理。实验以乌氏黏度计法测量聚合物溶液的黏度下降率,通过对pH值、水质阴阳离子量、黏均分子量和剪切速率等相关因素的研究发现,渤海JZ9—3油田注聚用FP3640C型聚合物的溶液黏度在pH值2～4范围内影响明显,pH〉7以后,黏度损失率减小;JZ9～3油田地层水中的Mg2＋、Ca2＋对聚合物的黏度影响显著;当离子浓度在2500～4000mg／L范围内,Na＋和K＋对黏度的降低有明显的影响;恒温60℃时,聚合物的黏度随着恒温时间的延长而下降,至30d后趋于稳定;剪切速率增加,黏度逐渐降低,转速达到8000r／min后,黏度亦趋于稳定。     

Boussinesq方程与抛物型缓坡方程2种波浪模型的比较分析

波浪破碎的模拟对于波浪模拟的准确性十分重要。为了解波浪破碎模型的问题,本文对抛物型缓坡方程和Boussinesq方程这2种波浪模型所采用的破碎方法进行比较和分析。运用基于Boussinesq方程的Funwave模型和基于抛物型缓坡方程的REF/DIF模型,分别对特拉华大学的未破碎圆形浅滩试验和作者于实验水槽进行的Undertow试验这2个物理模型进行波高模拟、比较与分析。模拟结果表明:Funwave和REF/DIF这2种波浪模型都能准确的模拟出波高随水深的变化情况,但对于波浪破碎后的情况,REF/DIF模型模拟的更为精确一些。     

The aggregation behavior and formation of nanoparticles of oleoylchitosan in dilute aqueous solution

Oleoylchitosans (O-chitosans) with different degrees of substitution (DS) were synthesized by reacting chitosan with oleoyl chloride. The chemical structures of the products were characterized by 1H NMR and FT-IR. These results suggested the for-mation of an amide linkage between the amino groups of chitosan and the carboxyl groups of oleic acid. The viscosity of O-chitosan sharply increased with the increase of concentration, whereas that of unmodified chitosan rose only slightly. This increase became larger as the DS increased. All of the O-chitosans could reduce surface tension slightly. The critical aggregation concentration (CAC) of O-chitosans with DS 5%, 11%, and 27% were 79.43 mgL-1, 31.6 mgL-1, and 10mgL-1, respectively. Nanoparticles were prepared using an O/W emulsification method. The mean diameters of the polymeric amphiphilic nanoparticles of O-chitosans with DS 5% and 11% were around 327.4 nm and 275.3 nm, respectively.