优选数值计算方法用于不对称街道峡谷的研究

分别将迎风、混合及调和QUICK格式用于对称街道峡谷的汽车排放污染物浓度预测,并与风洞实验结果相比较,研究表明数值模拟与风洞实验吻合较好,调和QUICK格式的预测效果最佳。将调和QUICK格式用于不对称街道峡谷的研究,发现当迎风面建筑物高于背风面建筑物时,峡谷内的流场和浓度场与对称街道峡谷相似,即峡谷内有一个顺时针方向的强漩涡,使得背风面污染物浓度高于迎风面污染物浓度。同时,随着迎风面建筑物高度的增加,漩涡中心的位置成垂直向上分布,且与迎风面建筑物的高度基本成线性关系;当迎风面建筑物低于背风面建筑物且差别较大时,街道峡谷内出现了两个反时针方向旋转的强漩涡,使得峡谷内的流场与浓度场都发生较大的变化,迎风面污染物浓度会高于背风面污染物浓度。同时表明,峡谷上方的顺时针方向漩涡的中心呈抛物线向右上方向发展,而峡谷下方的逆时针方向旋涡的中心呈抛物线向左E方向发展。     

TRAFFIC EMISSION TRANSPORTATION IN STREET CANYONS

Spatial distributions of traffic-related pollutants in street canyons were investigated by field measurements and Computational Fluid Dynamics (CFD). Two typical street canyons were selected for field monitoring, and a three-dimensional numerical model was built based on Reynolds-averaged Navier–Stokes equations equipped with the standard k ? ε turbulence models for CFD simulations. The study shows that the pollutant concentrations of vehicle emission correlate well with the traffic volume variation, wind d...     

城市对称街道峡谷气流及污染物扩散特征的研究

与风洞实验的对比表明数值模拟能较好地预测街道峡谷浓度场。研究了宽、窄两种峡谷（高宽比范围为0．17～3．25）的内部流场和浓度场。表明：当高宽比大于1时,随着高宽比的增加,峡谷内旋涡数逐渐增多,污染物浓度也随着旋涡的变化而变化;当高宽比小于1时,峡谷内由一个旋涡演变为两个方向相反的旋涡,随着高度的进一步减小,两个旋涡开始左右分离,其浓度也随着旋涡的变化而变化。当旋涡为顺时针时,使得背风面污染物浓度出现显著上升的趋势,而当旋涡为逆时针时,会使得迎风面的污染物浓度出现显著上升的趋势。总体看来,随着建筑物高度的增加,污染物难以扩散,从而使峡谷近地面处的污染物浓度增大。     

Wind tunnel simulation of pollutant dispersion inside street canyons with galleries and multi-level flat roofs

In this study, the pollutant dispersion within street canyons is studied by experiments conducted in an environmental wind tunnel. The vehicular exhaust emissions are modeled using a line source. The pollutant(smoke) concentrations inside the canyons are measured based on a light scattering technique. The pollutant concentrations within the four different street canyons containing the galleries and the three-level flat-roofs under both the isolated and urban environments are obtained and discussed. For each of the four canyon configurations investigated, it is found that there is an obvious discrepancy between the pollutant dispersion patterns under the isolated environment and the urban environment. The three-level flat roof is found to significantly influence the pollutant distribution pattern in a street canyon. In order to clarify the impacts of the wedge-shaped roofs on the pollutant dispersion inside an urban street canyon of an aspect ratio of 1.0, the pollutant distributions inside urban street canyons of three different wedge-shaped roof combinations are measured and analyzed. It is revealed that the pollutant distribution pattern inside the urban street canyon of an aspect ratio of 1.0 is influenced greatly by the wedge-shaped roof, especially, when an upward wedge-shaped roof is placed on the upstream building of the canyon. Images from this study may be utilized for a rough evaluation of the computational fluid dynamics(CFD) models and for helping architects and urban planners to select the canyon configurations with a minimum negative impact on the local air quality.     

STABILITY OF VORTEX STREET IN GAS-LIQUID TWO-PHASE FLOW

The stability of the Karmen vortex street in gas-liquid two-phase flow was studied experimentally and theoretically. The values of the parameter h/l characterizing the vortex street structure (i. e. , the ratio of the vortex street width to the distance between two vortexes) for a stable vortex street in gas-liquid two-phase flow were obtained for the first time. The parameter h/l was prpved to be a variable, not a constant as in single-phase flow, h/l is related to the upstream fluid void fraction. In gas-liquid two-phase fluid flow to form a steady vortex street is more difficult than in a single-phase fluid flow. Because in the unsteady vortex shedding the vortex shedding band frequency is broader than the one in the single phase fluid flow, so it is easier to induce the cross-cylinder resonance than in the single phase fluid flow, and this case should give rise to the attention of engineers.     

垂直上升气液两相流中三角形柱体两相斯托拉赫数的研究

本文试验研究了两种规格三角形柱体，在垂直上升气液两相流中，发生气液两相涡街时，气液两相斯托拉赫数的变化规律。在测得大量数据的基础上，得出了发生气液两相涡街时，气液两相斯托拉赫数的通用关系式，研究表明，气液两相斯托拉赫数在两相工况下为一变数，与来流截面含气率、涡街发生体形状和特征尺寸、来流方向等因素有关，应用此关系式，根据测得的两相涡街频率可钎涡街发展体作为测量两相流流量与组分的测量元件。     

孤立波与不同淹没深度水平圆柱体的相互作用

用基于时变雷诺方程和方程为基础的数学模型模拟了孤立波与近海不同淹没深度水平圆柱的相互作用过程,其中自由表面的跟踪采用了分段线性近似的VOF方法.结果表明：当圆柱靠近水底时,尤其是在圆柱与底部海床有较小缝隙时,圆柱底部附近的涡旋较强;而圆柱靠近水面时,水面附近的涡旋较强,圆柱越靠近水面,圆柱背浪面一侧的水面附近产生的涡对越多.     

Intensification of sonochemical degradation of phenol using additives at pilot scale operation

The present work reports the use of sonochemical reactors for the degradation of phenol in the presence of additives with an objective of enhancing the rates of degradation at a pilot scale operation. Process intensification studies have been carried out using additives such as hydrogen peroxide (H2O2) (0.5-2.0 g/L), sodium chloride (0.5-1.5 g/L) and solid particles viz. cupric oxide (CuO) and titanium dioxide (TiO2) (0.5-2.5 g/L). Optimum concentration for H2O2 and sodium chloride has been observed beyond which no beneficial effects are obtained even with additional loadings. Maximum extent of degradation has been observed by using ultrasound/H2O2/CuO approach at a solid loading of 1.5 g/L followed by ultrasound/H2O2/TiO2 approach at a loading of 2.0 g/L. The obtained results at pilot scale operation in the current work are very important especially due to the fact that the majority of earlier studies are at laboratory scale which cannot provide the design related information for large scale operation as required scale up ratios are quite high adding a degree of uncertainty in the design. The novelty of the present work lies in the fact that it highlights successful application of sonochemical reactors for wastewater treatment at pilot scale operation.     

KUROSHIO INTRUSION INTO THE SOUTH CHINA SEA

1. INTRODUCTION Under the role of the geostrophic β -effect, wind driven ocean circulation encounters the western boundary and forms the westward intensification current with the longitude movement along the boundary in the direction of the leaving equat…     

利用分离盘控制隔水管涡激振动的数值模拟

涡激振动是导致深海隔水管疲劳失效的重要因素.为有效控制隔水管涡激振动,提出了利用分离盘控制涡激振动的方法.对加装0.25～2.0倍隔水管直径的分离盘后的隔水管流动进行了二维数值模拟.研究了亚临界状态下各种模型旋涡脱落的流场结构、脱落模态、隔水管升阻力系数和旋涡泄放频率的变化特征.结果表明:分离盘加装前与经典的实验和计算结果吻合很好;不同尺寸的分离盘对隔水管涡激振动控制效果具有明显差异;当分离盘的长度为1.0至1.5倍的隔水管直径时,平均阻力系数可以减小20%,尾迹涡街的频率也有了较大的减小,达到控制涡激振动的最优效果.     

多孔方型人工鱼礁绕流的数值模拟研究

数值模拟得到了5种不同来流速度(0.1 ～0.8 n/s)下的多孔方型人工鱼礁周围的水流场.过礁体中心的铅垂面上速度分布表明:①不同来流速度下,上升流的最大速度和平均速度均分别为来流速度的0.74倍和0.12倍,上升流最大高度均为礁体高度的2.6 ～2.7倍,背涡区的长度和高度均分别为礁体高度的4倍和1.25倍;②在靠近礁体背流面形成水流方向与来流方向相一致的透水区.过礁体中心的水平面上速度分布表明:①不同来流速度下,背涡区的长度和宽度均分别为礁体宽度的4倍和1.8倍;②在鱼礁内部形成水流方向杂乱的旋涡区.本研究还初步比较了多孔方型人工鱼礁绕流与无孔方型人工鱼礁绕流的流场效应异同点.     

Deciphering the science behind electrocoagulation to remove suspended clay particles from water.

Electrocoagulation removes pollutant material from water by a combination of coagulant delivered from a sacrificial aluminium anode and hydrogen bubbles evolved at an inert cathode. Rates of clay particle flotation and settling were experimentally determined in a 7 L batch reactor over a range of currents (0.25-2.0 A) and pollutant loadings (0.1-1.7 g/L). Sedimentation and flotation are the dominant removal mechanism at low and high currents, respectively. This shift in separation mode can be explained by analysing the reactor in terms of a published dissolved air flotation model.     

Turbulent heat transfer and pressure loss in a square channel with discrete broken V-rib turbulators

Turbulent periodic flow, heat transfer, friction loss and thermal enhancement characteristics in a three-dimensional horizontal square channel with broken V-ribs(B-VR) are numerically investigated. The computations are based on the finite volume method, and the SIMPLE algorithm with QUICK scheme is implemented. The B-VR were installed on both sides of a plate which was diagonally placed in a square channel to produce longitudinal vortex flows through the tested section. Effects of different open corner ratios( d/ H= 0, 0.01, 0.02, 0.03, 0.04 and 0.05) on heat transfer and pressure loss in the channel and the results of the B-VR are studied. The pitch ratio(PR = p/ H) and blockage ratio(BR = p/ H) of B-VRs were fixed at 1.0 and 0.15, respectively. As compared with the channel without V-rib, the one with B-VRs possessed considerably higher heat transfer and friction loss. It is observed that apart from the rise of Reynolds number, the reduction of the open corner ratios leads to an increase in the Nusselt number and friction factor due to the weaker turbulence and lower resistance to the flow. According to the computational results for B-VRs, the optimum thermal enhancement is found at d/ H= 0.     

排水系统入海口新型消能工

通过实体模型试验研究了某排水系统入海口水工建筑物的水力性能,设计提出一种新型的墩栅涡流室消能工。该新型消能工的水力特点是:流出排水隧洞的高速水流大部分通过进口墩栅空隙流入涡流室,小部分在进口墩栅前发生水跃后扎入涡流室中产生强烈的顺时针漩涡,通过水跃、墩栅的阻力和涡流室漩涡的共同作用消能,并将来流的动能转换为势能,之后,涡流室中的大部分水流在重力作用下通过出口墩栅空隙流向下游,其余水流从墩栅顶部溢流。这种新型的墩栅涡流室不仅消能效果良好而且出流均匀,并容许各种杂物如石块、泥沙等自由通过,避免涡流室中发生严重的淤积。     

绕圆柱非定常周期性涡旋脱落的数值模拟

利用非定常流函数涡量方程数值模拟圆柱突然起动尾流涡旋的形成及周期性脱落过程。对求解的流函数的一阶导数即速度项采用四阶精度的Hermitian公式，而方程的对流项则采用四阶精度的差分格式，并利用ADI方法迭代求解差分方程组。当雷诺数Re不大于40时，圆柱尾流为附体的两个对称涡，为定常解。当Re大于40后流动为非定常及非对称的，圆柱尾流呈现周期性涡旋交替脱落而形成著名的Karman涡街。选择Re=100为例，在初始条件未加任何扰动情况下，成功地模拟了圆柱非定常涡旋形成与脱落的完整过程（无量纲时间算到t=250及以上）。所计算的阻力系数与实验结果及其它数值方法的计算结果一致。约在t=200形成严格的Karman涡街。对涡量方程ADI求解方法的稳定性进行了分析。对流项采用四阶精度差分格式，若应用于定常问题，将极大提高数值求解的精度，若应用于非定常问题的求解，将对求解精度有所改善，其中时间空间两阶混合偏导数的处理是关键，有待进一步的数值实验。     

Enhanced biodegradation of 4-aminobenzenesulfonate in membrane bioreactor by Pannonibacter sp. W1

4-Aminobenzenesulfonate (4-ABS), an aromatic amine and recalcitrant toxic pollutant, is widely used in the dye and pharmaceutical industry. Pannonibactersp. W1 is a specialized microbial strain which can efficiently degrade 4-ABS. This study shows the feasibility of using the specialized strain in an MBR system to treat synthetic wastewater containing large amount of 4-ABS. Due to membrane retention, the biomass concentration is able to reach 5 g/L within two months of continuous operation. Pannonibacter sp. W1 is able to adapt to the high loading rate of 1000 mg 4-ABS/L and achieve a remarkable 4-ABS removal efficiency of 99% within 6 h. Strain W1 grows well under the MBR continuous operation and remains as the dominant bacterium at the end of 60 days continuous operation. Minor membrane fouling has been detected within 40 days of operating at 15 LMH. At a flux of 25 LMH, the system experiences the 'TMP jump'. The high organic removal rate and low membrane fouling results illustrate the excellent performance of the bioaugmented MBR system in 4-ABS wastewater treatment.     

二维矩形突起物绕流流动结构的实验研究

流场中旋涡的生成、演化与二维矩形突起物上游的流动分离有着密切的关系,该文利用PIV技术,对在均匀来流条件下无压流流道内底壁矩形突起物流动的二维瞬时流速场进行了测量,得到了湍流情况下,不同台阶比（h1/h）为2和4时流场中旋涡的生成发展与演化的一般规律。文中分析了两种工况下流场中的旋涡结构的特点和突起物上、下游及顶部旋涡的运动特性和细部特征。     

均匀流绕旋转圆柱分离流动的数值模拟

本文利用离散涡模型与边界层理论相结合的方法，研究了高雷诺数下，均匀流绕旋转圆柱的分离流动以及有关动力学特性，并验证了Magnus效应，数值模拟过程中，边界层方程用Keller盒式法求解，离散涡采用涡量均匀分布的圆形涡团模型并以涡核半径随时间增长来模拟涡旋的粘性扩散效应。在计算绕旋转圆柱的流动中，无须人为地引进非对称扰动，到一定时候就能自动形成交替脱落的涡街，旋转圆柱周向速度与来流速度比值α的变化范围为0.05-0.3。计算所得升阻系数、分离点的位置以及压力分布与理论和实验结果相符。     

一体化脱氮除磷污水净化装置的开发及处理效果研究

好氧缺氧一体化的高效分离生物流化复合反应器(HSBCR)是在内循环三相生物流化床的基础上发展起来的一种新型反应器.考察HSBCR在较短停留时间内处理生活污水时的脱碳、脱氮和除磷效果,结果表明:好氧区HRT为1.5 h时,COD_(Cr)、氨氮、总氮、总磷去除率分别为81%、51%、47%和50%;HRT为2.0 h时分别为84%、64%、54%和57%.HSBCR不仅能在短时间内使COD_(Cr)快速高效地去除,而且可以实现硝化与反硝化的一体化,满足脱氮除磷的要求,有望成为小城镇污水处理的适用技术.     

Spatial Distribution and Seasonal Variability of Rainfall in a Mountainous Basin in the Himalayan Region

The average distribution of precipitation provides essential input for understanding the hydrological process. The role of complex topography in mountainous basins makes the spatial distribution of precipitation different than the plain areas. Besides the rugged topography, the Himalayan basins also face the problem of limited physical accessibility and data availability. In this study, seasonal and annual distribution of rainfall with elevation and distance from the lower most station (Akhnoor) has been studied for the Chenab basin (western Himalayas). The study basin covers all the three ranges i.e. outer, middle and greater Himalayas. The rainfall stations are grouped into windward and leeward categories. The trends of spatial distribution of rainfall are discussed in detail. Attempts are also made to investigate the impact of reduced network on the mean annual rainfall of the Chenab basin. A reduction in rain gauges from 42 to 19 has resulted in an increase in the estimate of mean annual rainfall by 14% with respect to the estimate obtained using 42 stations network.