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1.
90°弯管内固液两相流临界流速浅析 总被引:1,自引:0,他引:1
以90°弯管中固液两相流作为研究范围,并将此特殊水力状况下的固体颗粒假设为随液体一起作沿弯管轴线的圆周运动,速度采用断面平均速度的方式,进行受力分析、求解,来研究管道内固液两相流动的颗粒沉降速度以及流体的不淤流速,并做出了针对物料的性质、流体的性质和管道特性等相关影响因素的分析. 相似文献
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在滑坡快速下滑过程中,滑带的剪切运动是某种形式的固液两相流。固相颗粒主要是碎石颗粒,液相则是黏土颗粒和水的混合物。固相颗粒之间的液相,无论是静止、流动还是两相流状态,都会对固相颗粒的粒间作用力产生较大影响。在剪切速率达到一定程度后,固相颗粒的随机碰撞产生的颗粒间作用力将成为颗粒间主要作用力,在此作用力作用下,固相颗粒运动符合Navier-Stokes方程所描述的流体运动。由于滑带特有的边界条件,滑带材料在高速剪切条件下的流体运动,可以用简化的Navier-Stokes方程,即雷诺公式来表示。在一定边界条件下,根据雷诺公式,液相流体产生动压变化,液相的动压变化引起固体颗粒之间的接触应力变化,最终导致滑带整体的抗剪强度的变化。 相似文献
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以90°弯管中固液两相流作为研究范围,并将此特殊水力状况下的固体颗粒假设为随液体一起作沿弯管轴线的圆周运动,速度采用断面平均速度的方式,进行受力分析、求解,来研究管道内固液两相流动的颗粒沉降速度以及流体的不淤流速,并做出了针对物料的性质、流体的性质和管道特性等相关影响因素的分析。 相似文献
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为了进一步研究方腔内固液相变的过程,本文基于格子玻尔兹曼方法(LBM),采用两区域模型探究了方腔内填充不同方向梯度孔隙率分布的多孔骨架固液相变过程,从孔隙尺度分析了相变过程的流动和传热机理;并对梯度孔隙率多孔介质内固液相变过程中的糊状区做了详细的描述;重点研究了方腔内不同方向梯度孔隙率分布和均匀孔隙率骨架分布对相变过程的影响。研究结果表明:在填充多孔介质固液相变过程中,传热方式由热传导逐渐向自然对流换热转变,从而导致了上薄下厚的糊状区;在填充多孔介质骨架方腔内,不同方向的梯度孔隙率分布对相变过程的影响是不同的,与均匀孔隙率相比,从左到右线性减小以及从上到下线性增加和减少的多孔介质孔隙率分布,其融化率和高温壁面平均Nu数都较大,表明其孔隙率梯度分布的多孔骨架对相变换热起到了明显的促进作用;而当多孔介质孔隙率分布从左到右线性增加时,相变过程则受到明显的抑制。 相似文献
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能源塔吸热过程的实质是塔内波纹填料表面液相降膜与逆流气相接触发生热质交换,为探究填料表面液膜流动对能源塔内气液两相热质交换过程的影响机制,文中建立了波纹填料表面液相降膜流动模型,模拟了不同气液相入口参数以及不同波纹结构的填料表面的液膜流动过程,通过对比各工况下填料表面稳定液膜的特性,分析了影响液膜流动的关键因素,从增强气液相接触角度出发,寻求更加合理的气液相入口参数和波纹结构。 相似文献
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在废水处理流化床反应器中,固液两相流的水力相似性,是动力学模型推导、反应吕放大或缩小的基础。据此在扒求流化床反应器内固液两相流水力相似准数的基础上进行了试验,获得了一组相似参量曲线图:(1)Ar△ρ-Re-E曲线;(2)E-U-Ar△ρ曲线;(3)E-Re-Ar△ρ曲线,并运用这些曲线对实际操作进行了分析讨论。 相似文献
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液固两相饱和介质动力分析的一种显式有限元法 总被引:3,自引:1,他引:3
以经典的Biot液固两相饱和介质动力理论为基础,建立了以固相位移和液相移为未知量的液固两相饱和介质动力分析的一种有限元法。该显式方法克服了隐式方法需要求解联立方程组的缺点,具有节省计算机内存空间和计算时间的优点,可以方便地应用于求解大自由度和介质非线性问题。算例分析表明,该方法具有较高的计算精度。 相似文献
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建立了流固耦合传热的数值分析模型,求解得到了流固耦合传热性能如温度、传热系数、摩擦系数、汽相体积分数沿换热元件轴向变化的分布。结果表明:随着质量流量的增加传热性能有被强化的趋势;相变之前,传热性能与热流密度的无关,相变之后,传热性能被强化,但趋势逐渐放缓;热流密度越大,质量流量越小,相变点越靠前。 相似文献
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《Planning》2014,(10)
临界流是在给定上游条件下流速达最大值的一种现象,这种现象在单相和两相中均会发生。对于单相流体,临界流研究已十分清楚,通常发生在最小截面处的流速达到声速的地方。对于两相流动,由于两相之间存在着质量、动量、能量的交换,而两相之间的界面又十分复杂,因而两相临界流的研究十分困难,至今尚未完善。本文是对经典临界流模型进行研究,将模型预测值与Super Moby-dick实验值进行比较,分析出不同模型的特点以及适用范围。 相似文献
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油气流-固耦合渗流研究进展 总被引:7,自引:2,他引:7
介绍了多孔介质流-固耦合渗流研究的重要意义,对多孔介质流-固耦合渗流研究进展加以综述和讨论,提出了进一步深入研究的方向,并着重讨论了近十年来油气流-固耦合多相渗流及其应用研究和各种耦合方法,为其他渗流工作提供一定的参考。 相似文献
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通过实地监测,针对不同车间的棉尘颗粒物的浓度及粒径分布特征进行了对比分析,监测结果表明:清花,梳棉及细纱车间的平均总颗粒物浓度分别为3.65 mg/m 3、2.87 mg/m 3、1.75 mg/m 3,均大于棉尘接触限值.由前纺工艺至后纺工艺,总颗粒物浓度呈逐渐减小的趋势,清花车间总颗粒物浓度是细纱车间浓度的2.08... 相似文献
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通过在砂浆中掺入不同量、不同粒径的橡胶粉,分析了橡胶粉掺量、粒径对砂浆强度、弹性模量、极限拉伸值影响规律。在数据分析基础上,综合评价了橡胶粉掺量、粒径对砂浆抗裂性影响规律。试验结果表明:随着橡胶粉掺入量的增加强度、弹性模量逐渐降低,而极限拉伸值却随着橡胶粉掺入量的增加而增加;在相同配合比时,掺粗橡胶粉砂浆的弹性模量、抗压强度大于掺细橡胶粉砂浆,但轴拉强度、极限拉伸值却低于掺细橡胶粉砂浆;橡胶粉掺入量增加,砂浆抗裂性能提高,掺细橡胶粉砂浆的抗裂性优于掺粗橡胶粉砂浆。 相似文献
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The paper examines the importance of suspended particle size distribution in deep bed filtration. Experiments were conducted with suspensions of different size distributions. The changes in total concentration, concentrations of particles of different sizes and the headloss were observed. The suspension with the largest mean particle size gave the greatest removal. It was also observed that the size distribution changed with depth and time, and this was shown to be crucial in understanding filter behaviour. It was concluded that in modelling filter performance it is not sufficient to use the mean characteristics of the influent suspension. Some evidence was found for the interaction between particles of different sizes, and the particle size distribution also affects the distribution of deposit throughout the bed. 相似文献
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Franck U Odeh S Wiedensohler A Wehner B Herbarth O 《The Science of the total environment》2011,409(20):4217-4221
Background
Previous studies observed associations between airborne particles and cardio-vascular disease. Questions, however, remain as to which size of the inhalable particles (coarse, fine, or ultrafine) exerts the most significant impact on health.Methods
For this retrospective study, data of the total number of 23,741 emergency service calls, registered between February 2002 and January 2003 in the City of Leipzig, were analysed, identifying 5326 as being related to cardiovascular incidences. Simultaneous particle exposure was determined for the particle sizes classes < 100 nm (UFP), < 2.5 μm (PM2.5) and < 10 μm (PM10). We used a time resolution of 1 day for both parameters, emergency calls and exposure.Results
Within the group of cardiovascular diseases, the diagnostic category of hypertensive crisis showed a significant association with particle exposure. The significant effect on hypertensive crisis was found for particles with a size of < 100 nm in diameter and starting with a lag of 2 days after exposure. No consistent influence could be observed for PM2.5 and PM10. The Odds Ratios on hypertensive crisis were significant for the particle size < 100 nm in diameter from day 2 post exposure OR = 1.06 (95%CI: 1.02-1.10, p = 0.002) up to day 7 OR = 1.05 (95%CI 1.02-1.09, p = 0.005).Conclusion
Ultrafine particles affect cardiovascular disease adversely, particularly hypertensive crises. Their effect is significant compared with PM2.5 and PM10. It appears necessary, from a public health point of view, to consider regulating this type of particles using appropriate measurands as particle number. 相似文献18.
《Soils and Foundations》2023,63(4):101336
In practice, post-liquefaction strength is largely determined from case histories, but the case history database is limited and there are gaps in the information available in each case. As a result, laboratory tests have continued to play a key role in determining how various factors influence post-liquefaction strength. This paper presents an investigation into how factors such as particle size, particle size distribution, fines content, and compressibility influence post-liquefaction strength in simple shear tests. Eleven particle size distributions of a natural soil and a tailings material, ranging from silt to fine gravel, were studied. The results were compared with case histories.Materials of different geologic origins have meaningfully different post-liquefaction strengths. Particle size and particle size distributions were both found to significantly affect post-liquefaction response as well. Post-liquefaction strengths obtained from simple shear tests agreed well with those back calculated from case histories. Laboratory testing can be utilized to determine how the post-liquefaction strength of a given material may compare to the case history database, and can be used to guide design decisions. This is an important practical finding, given the sparse case history database. 相似文献
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