具有水流层的双层玻璃温室模型研究

针对重庆的特殊气候提出了具有水流层的双层玻璃温室的改进模型,并进行了测试分析.对双层玻璃温室进行了建模,得出了双层玻璃温室的两层玻璃间空气层厚度与温室玻璃厚度的比例,及空气层温差与温室玻璃的内外侧温差之比,并得出双层玻璃温室在持续高温且昼夜温差小的情况下隔热效果不明显.从而提出了模型改进方案,在一般的双层玻璃温室的外层内表面上定时喷洒一层水,形成一层薄薄的水流层,直接对玻璃温室的外层玻璃内侧进行降温,让部分热量得以转移,从而提高双层玻璃的隔热效果.通过模型分析和测试表明,具有水流层的双层玻璃温室隔热效果优于普通的双层玻璃温室.

坡面薄层水流水动力学特性试验

坡面流水动学特性对阐明土壤侵蚀和坡面产沙机理均有重要意义,采用坡面定床阻力试验,定量研究了6种不同粗糙度床面、5种不同坡度下坡面薄层水流水力要素关系及阻力的变化特征,以期揭示坡面薄层水流阻力的内在规律性。结果表明,坡面薄层水流流态指数随坡度呈现出的先减小后增加的变化趋势,当试验坡度小于0.15 rad时,流态指数随坡度的增加而逐渐减小,当坡度大于0.15 rad时,出现相反的变化趋势。流态指数随床面粗糙度呈抛物线变化趋势,其均值为0.376,总体上坡面薄层水流属于滚波流区和过渡流区的范畴;水流弗劳德数与单宽流量和试验坡度均成幂函数关系,临界流对应的单宽流量随粗糙度的增加而增大,随坡度的增加而减小,水流流型处于临界流和急流型态;阻力系数与单宽流量呈幂函数关系,而与雷诺数成反比关系,关于增阻的原因主要与绕流产生压差阻力和坡面滚波流引起的局部阻力有关,并根据薄层水流阻力特征,提出了滚波流区阻力计算公式。研究成果可为坡面土壤侵蚀预报模型构建提供理论依据,从而促进明渠水流理论向坡面水流方面扩展。

坡面薄层水流流态判定方法的初步探讨

为了研究坡面薄层水流流态的判定方法，从水力学与泥沙动力学观点出发，在4种不同坡度有机玻璃床面与人工粗糙床面（砂粒粒径为0．5～1mm）上对坡面薄层水流进行了试验研究，并应用水力学二元流雷诺数与泥沙动力学绕流雷诺数对坡面薄层水流流态进行了分析比较，研究结果表明绕流雷诺数能较好反映坡面薄层水流流态。

深水钻井地质灾害浅层水流问题研究

浅层水流是一种严重的深水钻井地质灾害,会延长钻井作业的非生产时间,造成巨大的经济损失,甚至导致井和平台废弃。介绍了浅层水流的概念和5种形成机理,着重描述了异常压力砂体机理,从而加深了对浅层水流灾害的认识,为研究浅层水流灾害的识别预测方法以及处理方法奠定了基础。此外,还介绍了浅层水流的识别方法和浅层水流地层独特的岩石物理特征,阐述了浅层水流的地震预测方法和预测步骤。有效控制和处理浅层水流灾害对深水钻井安全至关重要,介绍了浅层水流灾害的处理流程和3种处理方法,并提出了研究浅层水流危害的方向。

坡面薄层水流流速测量的比较研究

在室内模拟水槽中分别用质心运动学原理、电解质脉冲法和流量法3种方法测量不同坡度、不同泥沙含量条件下的薄层水流流速。比较以上3种测量结果发现在下垫面无渗透时,即加入的盐液没有损失时,电解质脉冲法测量坡面薄层水流流速与质心运动速度及流量法测量结果基本是一致的。在泥沙含量较大时,电解质脉冲法测量结果的误差较大,流量对测量结果影响不显著;随着测量距离的延长,测量误差变小,这可能是随着测量距离的增加,加入电解质的时间与测量时间之比减小,从而使假设加入的电解质为电解质脉冲更加合理。总的来说,电解质脉冲法在实验条件下测量坡面薄层水流流速是可行的。

深水钻井中浅层水流的预防与控制方法

浅层水流是深水钻井中常见的地质灾害之一,由此所造成的经济损失是十分巨大的。如何避免和减轻可能要面对的浅层水流灾害是一个很有挑战性的课题。因此非常有必要开展相关预防与控制方法研究。介绍了诱发浅层水流的4种机理,分别为:高压砂体机理、裂缝诱导机理、流体储藏诱导机理以及高压传递机理。根据浅层砂体的特性和浅层水流诱导机理,提出了浅层水流钻前预防方法和钻井过程中浅层水流预防方法。针对已识别的浅层水流,归纳总结了控制浅层水流发生的5种方法:提高钻井液密度、使用海底分流器、使用化学钻井液、泡沫胶结固井以及使用导管穿过浅层水流层。该研究对于深水钻井中有效地预防和控制浅层水流的发生具有重要意义。

陡坡条件坡面薄层水流沿程变化及水流阻力计算

基于系列陡坡水槽条件不同坡面粗糙程度薄层水流试验,测试分析了坡面薄层水流运动参数沿程变化,并进一步讨论了坡面水流阻力计算方法。结果表明:光滑坡面条件同一流量流速随坡长的增加而增加,而对于较粗床面或较陡坡面流速沿程出现了峰谷变化;由于陡坡条件下坡面薄层水流参数呈现沿程变化的特征,因而传统意义上常用的平均水力参数法计算水流阻力已不适宜于陡坡条件,基于沿程水流阻力计算的方法更加可靠。

试论初生态侵蚀性坡面薄层水流的基本动力特性

从水力学与泥沙运动力学观点，对初生态侵蚀性坡面薄层水流的基本动力特性，如流道、流态、临界水深、阻力系数等几个基本问题，作了半理论性探讨。

降雨对浅层水流阻力的影响

通过实验室人工降雨水槽试验,研究了降雨影响下浅层水流的阻力规律。根据试验中观察到的物理现象及对实测资料的分析,讨论了降雨对浅层水流特性的影响,提出了"伪层流"的概念,建立了不同流区的Darcy-Weisbach阻力系数∫的估算式。研究成果可用于坡面流计算及土壤侵蚀模拟等方面。

表面张力对坡面薄层水流临界雷诺数的影响

[目的]探究坡面薄层水流流态判别时表面张力的作用。[方法]采用比较作用力大小的理论方法。在比较表面张力(未降雨条件下)在运动方向上的所体现的表面波阻力与黏滞力大小的基础上,基于相关文献试验及数值模拟结果,分析波长、波高与水深的定量关系。[结果](1)层紊流判别临界雷诺数与弗劳德数、滚波波长、波高有关。(2)滚波发生条件(Fr≥2),坡面薄层水流临界雷诺数大于明渠水流临界雷诺数。[结论]滚波发生后坡面薄层水流临界雷诺数最大值为明渠水流的1.187 5倍。

地面灌溉中浅层水流的模拟

通过对小麦和多年生牧草现场研究的试验数据分析，本文对地面灌溉浅层水流情况应用满宁方程提出了疑问。在Ｒ２值大于０．９时，流量──水深方程（方程２）与绝大多数试验结果相吻合。方程中指数α的值取决于作物种类、作物密度、高度、播种型式、生长阶段和水流条件，一般在１．０到３．０之间变化。因而满宁方程把指数定为常数（即５／３）是不合适的。本文提出的流量──水深方程比满宁方程更适合浅层地表水流情况。并且提出了地表水流摩阻系数的变化范围。

低含沙坡面薄层水流垂线流速特征试验分析

为分析低含沙量条件下坡面薄层水流速分布规律.试验选用有机玻璃水槽,基于粒子图像测速(particle image velocimetry,PIV)技术根据5种水深、3种坡度、3种含沙量的垂线流速测量结果.发现含沙量对阻力系数λ,卡门常数κ都具有较大影响,水流的垂线流速分布与明渠存在较大差别.低含沙坡面薄层水流中,阻力系数λ随含沙量增大而增大,随坡度增大而增大,且受边壁影响较大.垂线分布最大流速产生在相对水深0.7~0.8的位置.在低含沙量条件下,水流在内区(底流区和主流区)的垂线流速遵循对数分布规律,其中卡门常数κ随含沙量增大而减小;最大流速约为垂线平均流速的1~1.1倍.

南水北调某泵站联轴层及出水流道模板施工与安全分析

本文针对南水北调工程的特殊性,在联轴层及出水流道模板方面,进行施工方案优化分析,达到在确保安全、质量的前提下,节约成本工期提前对同类工程实施有很大的借鉴作用从实施效果各项指标统计分析表明达到甚至优于规范要求取得了预期成效。

Boussinesq equation-based model for flow in drainage layer of highway

In order to study the water flow in the drainage layer of highway under steady-state condition, one-dimensional （1D） Boussinesq equation-based model with Dupuit-Forchheimer assumption was established and the semi-analytical solutions to predict the water-table height were presented. In order to validate the model, a two-dimensional （2D） saturated flow model based on the Laplace equation was applied for the purpose of the model comparison. The water-table elevations predicted by ID Boussinesq equation-based model and 2D Laplace equation-based model match each other well, which indicates that the horizontal flow in drainage layer is dominated. Also, it validates the 1D Boussinesq equation-based model which can be applied to predict the water-table elevation in drainage layer. Further, the analysis was conducted to examine the effect of infiltration rate, hydraulic conductivity and slope of drainage layer on the water-table elevation. The results show that water-table falls down as the ratio of Is to K decreases and the slope increases. If the aquifer becomes confined by the top of drainage layer due to the larger ratio of Is to K or smaller slope, the solution presented in this work can also be applied to approximate the water-table elevation in unconfined sub-section as well as hydraulic head in the confined sub-section.

Turbulent boundary layers and hydrodynamic flow analysis of nanofluids over a plate

A numerical analysis of the log-law behavior for the turbulent boundary layer of a wall-bounded flow is performed over a flat plate immersed in three nanofluids(Zn O-water,SiO_(2)-water,TiO_(2)-water).Numerical simulations using CFD code are employed to investigate the boundary layer and the hydrodynamic flow.To validate the current numerical model,measurement points from published works were used,and the compared results were in good compliance.Simulations were carried out for the velocity series of 0.04,0.4 and 4 m/s and nanoparticle concentrations0.1% and 5%.The influence of nanoparticles’ concentration on velocity,temperature profiles,wall shear stress,and turbulent intensity was investigated.The obtained results showed that the viscous sub-layer,the buffer layer,and the loglaw layer along the potential-flow layer could be analyzed based on their curving quality in the regions which have just a single wall distance.It was seen that the viscous sub-layer is the biggest area in comparison with other areas.Alternatively,the section where the temperature changes considerably correspond to the thermal boundary layer’s thickness goes a downward trend when the velocity decreases.The thermal boundary layer gets deep away from the leading edge.However,a rise in the volume fraction of nanoparticles indicated a minor impact on the shear stress developed in the wall.In all cases,the thickness of the boundary layer undergoes a downward trend as the velocity increases,whereas increasing the nanoparticle concentrations would enhance the thickness.More precisely,the log layer is closed with log law,and it is minimal between Y^(+)=50 and Y^(+)=95.The temperature for nanoparticle concentration φ=5%is higher than that for φ=0.1%,in boundary layers,for all studied nanofluids.However,it is established that the behavior is inverted from the value of Y^(+)=1 and the temperature for φ =0.1% is more important than the case of φ =5%.For turbulence intensity peak,this peak exists at Y^(+)=100 for v=4 m/s,Y^(+)=10 for v=0.4 m/s and Y^(+)=8 for v=0.04 m/s.

An experimental comparison of water based alumina and silica nanofluids heat transfer in laminar flow regime

Experimental investigations were carried out to determine the Al2O3/water and SiO2/water nanofluids flowing through a circular tube. convective heat transfer performance and pressure drop of Measurements show that the addition of small amounts of nano-sized Al2O3 particles to the base fluid increases heat transfer coefficients considerably, while the result for the silica nanofluids contradicts with the alumina nanofluids and this leads to some interesting results. In the case of alumina nanofluids, an average increase of 16% in convective heat transfer coefficient is observed with an average penalty of 28% in pressure drop. Moreover, flow resistance increases significantly compared to the base fluid even at very low concentrations of nanofluids. Finally, measured heat transfer coefficients are compared with predicted ones from the correlation of Shah under the same conditions.

Variation characteristics of aquifer parameters induced by groundwater source heat pump operation under variable flow

The variation characteristics of aquifer parameters,induced by groundwater source heat pump(GWSHP) operation under variable flow,were theoretically analyzed through a case study,in which the characteristics of building air conditioning load were considered.The results,compared with the constant flow operation,indicate that the influence on the variations of porosity,hydraulic conductivity and confined water head is decreased by 48%,51% and 71%,respectively,under variable flow operation.The security of variable flow operation is superior to that of constant flow.It is also concluded that the climate region and function of the buildings are primary factors which affect the suitability of variable flow operation in GWSHP.

Water slip flow in superhydrophobic microtubes within laminar flow region

The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were car- ried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within lam- inar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching- fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduc- tion ranges from 8% to 31%. It decreases with increasing Reynolds number when Re 〈 900, owing to the transition from Cassie state to Wenze] state. However, it is almost unchanged with further increasing Re after Re 〉 900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.

Experimental Research on Gas-Liquid Two-Phase Spiral Flow in Horizontal Pipe

In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.

Interfacial Shear Stress of Stratified Flow in a Horizontal Pipe

Experimental data are presented for the void fraction and the shear stresses of stratified gas-liquid flow in a pipe. A new technique was used to measure the interface shear stress. The interfacial shear stress was determined by using two methods: a momentum balance of gas and an extrapolation of the Reynolds shear stress profile at the gas-liquid interface. A new formula , relating to the interfacial friction factor with the void fraction and superficial gas Reynold number, was developed to predict the interface shear stress . The predicted values are in good agreement with experimental data.