An analytical model for solute mixing in surcharged manholes

A mathematical model has been developed to describe solute mixing in surcharged manholes using the submerged jet theory. The model has been applied for straight-through flow manholes and for manholes with a difference in the level of the inlet and outlet pipes. The model is applicable to dissolved substances, i.e. the model has not been validated for high sediment concentrations (above 1 g/l) and care should be taken in such cases. Simulation results from the new model are compared with laboratory measurements and are further compared to conventional modelling techniques currently available in commercial software specially developed for modelling the water quality in sewers. The results prove that the new model produces considerably better results compared to the traditional assumption of full mixing in a manhole. The new model compares well to the laboratory measurements and hence improves the accuracy of modelling soluble pollutant transport in sewers. The applicability of the new modelling approach is discussed and further studies are recommended.     

Numerical investigation of the effects of combining sewer junction characteristics on the hydraulic parameters of flow in fully surcharged condition

In this study, the effects of different parameters on flow structure and flow hydraulics for combining sewer junction consisting of manhole and lateral inflow were investigated numerically. For this purpose, the effects of dimension variations, main and lateral pipe slope, angle and the joint position of lateral pipe beside manhole, manhole geometry, and the outflow rate of manhole on flow structure and energy loss coefficients were investigated. Results show that the rate of energy loss decreases by heightening the installation position of lateral pipe beside manhole. In addition, it was shown that the slope variations of main and lateral pipes and outflow rate do not affect the rate of energy loss.     

地井爆炸的原因及防范措施

结合香港的实际情况,分析了可燃气体引起地井爆炸的原因:可燃气体自连接地井的管道上的裂缝或小孔,进入地井密闭空间,逐渐积聚直至形成爆炸性气体,遇点火源而引起地井爆炸,甚至引发一连串多个地井爆炸。提出了封堵地井连接管道的防范措施。     

Air-water flows in circular drop manholes

Drop manholes, a typical element of urban drainage networks in steep catchments and in reaches of supercritical flow, enhance air entrainment and entrapment. The air flow across drop shafts can be remarkably high.

This paper discusses the air transport phenomena and the effects of ventilation absence in drop manholes. Based on an extensive experimental study, air entrainment mechanisms have been accurately described and air demand has been evaluated in different flow regimes. In addition, the effects of ventilation absence on the hydraulics of circular drop manholes, with emphasis on sub-atmospheric pressure onset and pool depth raising, have been investigated. The effects of a possible air flow recirculation have also been evaluated. Issues regarding any scale effects have been discussed.

The influence of the main hydraulic and geometric parameters on drop manhole performance was contemplated to provide improved design concepts for sewer systems.     

Modelling sewer discharge via displacement of manhole covers during flood events using 1D/2D SIPSON/P-DWave dual drainage simulations

In urban areas, overloaded sewers may result in surcharge that causes surface flooding. The overflow from sewer systems mainly starts at the inlets until the pressure head in the manhole is high enough to lift up its cover, at which stage the surcharged flow may be discharged via the gap between the bottom of the manhole cover and the ground surface. In this paper, we propose a new approach to simulate such a dynamic between the sewer and the surface flow in coupled surface and sewer flow modelling. Two case studies are employed to demonstrate the differences between the new linking model and the traditional model that simplifies the process. The results show that the new approach is capable of describing the physical phenomena when manhole covers restrict the drainage flow from the surface to the sewer network and reduce the surcharge flow and vice versa.     

Hydraulic design aspects for supercritical flow in vortex drop shafts

ABSTRACT

Vortex drop shafts, as special sewer manholes, operate optimally if an adequate energy dissipation is guaranteed and the integrity of the structural components is safeguarded. The results of an experimental study on a vortex drop shaft with supercritical inflow are discussed herein. The hydraulic behaviour of the spiral inlet, the vertical shaft and the dissipation chamber is described. Based on detailed flow observations, useful recommendations for designing these structures are provided. It is demonstrated that a relation adopted for supercritical bend flows provides a reliable estimation of the maximum wave height along the inlet. A procedure for predicting the rotational flow angles and the velocity distribution along vertical shafts with swirling flows is developed. Water levels and pressure measurements in the dissipation chamber are further analysed to identify maximum forces acting on the chamber invert and to derive preliminary design equations.     

Supercritical flow in the 90° junction manhole

Based on previous observations of the 45° junction manhole for supercritical flow in the main and lateral branches, the hydraulics of the more common 90° junction manhole were explored. Using a selected manhole geometry involving: (1) a short straight piece in the lateral branch to inhibit full development of the bend wave, and (2) the addition of the junction extension as used in previous designs for the bend manhole, the present study gives results that are in basic agreement with those collected in the 45° junction manhole. This surprising result thus allows for a design basis independent of the junction angle.The present paper defines three waves that may occur in a junction manhole, i.e. bend wave, junction wave and the swell at the manhole outlet into the downstream pipe. In addition, the position of the determining junction wave was established. Important for the junction design is the discharge capacity for which supercritical flow can be maintained across the manhole. It was found that the lateral branch flow depth and the pipe diameter have an important effect on this capacity, for both branches or only one of the branches in operation.     

单箱多室预应力连续梁桥横梁人孔的受力分析

单箱多室截面的预应力混凝土连续梁桥,由于多道腹板的影响,横梁的剪力分布范围较大,在横梁上设置人孔将对梁体形成削弱,引起明显的应力集中,影响结构安全,故一般须对人孔周围进行加强配筋设计。鉴于预应力混凝土横梁开洞的复杂应力状态,通过对一座单箱双室截面的预应力混凝土连续梁桥设置人孔的中横梁的分析,运用空间有限元模型计算了预应力横梁孔洞周边的应力情况,为人孔的配筋设计提供依据。     

Validation of 2D shock capturing flood models around a surcharging manhole

This work offers a detailed validation of finite volume (FV) flood models in the case where horizontal floodplain flow is affected by sewer surcharge flow via a manhole. The FV numerical solution of the 2D shallow water equations is considered based on two approximate Riemann solvers, HLLC and Roe, on both quadrilateral structured and triangular unstructured mesh-types. The models are validated against a high resolution experimental data-set obtained using a physical model of a sewer system linked to a floodplain via a manhole. It was verified that the sensitivity of the models is inversely proportional to the surcharged flow/surface inflow ratio, and therefore requires more calibration from the user especially when concerned with localised modelling of sewer-to-floodplain flow. Our findings provide novel evidence that shock capturing FV-based flood models are applicable to simulate localised sewer-to-floodplain flow interaction.     

Centrifuge Modeling on Manhole Uplift in a Liquefied Trench

The uplift behavior of sewage manholes due to liquefaction in a trench is investigated through a series of dynamic centrifuge model tests. The objectives of a series of tests are to study the mechanism of the uplift and to obtain relationships among uplift displacement and factors affecting the uplift. The factors considered in the experiments are the ground water levels, the magnitude of input accelerations, the duration time of shaking, the relative densities of trench backfill and the native ground, the material of native ground, the volume of a trench, the apparent unit weight of a manhole, and the contact conditions at the bottom of a manhole. Test results show that the primary cause of uplift is the reduction of the effective confining stress near the bottom of a manhole due to strong shaking. The magnitude of uplift is found to be strongly correlated with the ground water depth, the intensity of shaking, the shear deformation of the trench, and the contact conditions at the bottom of the manhole. These findings are believed to be useful for engineering practice in the mitigation of the manhole uplift.     

Performance of radiator by using SiO2 nano fluids

ABSTRACT

This article reports a study on heat transfer and flow characteristics of nano fluid consisting of water and ethylene glycol as base fluid with different concentrations of SiO₂as nanoparticles (0.1% and 0.15%) are flowing in a shell and tube exchanger. The SiO₂ nanoparticles of about 15 nm diameter are used in this study. The results showed that the heat transfer coefficient of nano fluid was slightly higher than that of the base fluid at the same inlet temperature and at the same mass flow rate. It was observed that heat transfer coefficient of nano fluid was increased with an increased mass flow rate. Heat transfer coefficient was noticed to increase with the increase of the volumetric concentration of the SiO₂. But increasing the volume concentration caused the increase in the viscosity of the nano fluid resulted in an increase in friction factor.     

Quantification of energy losses at a surcharging manhole

Hydraulic models of sewer systems are commonly used to predict the risk of urban flooding. However, suitable calibration datasets in flood conditions are scarce. The quantification of energy losses within manhole structures is a current source of uncertainty within such models. To address this gap, a scaled physical manhole model is used to quantify hydraulic energy losses during surcharging and non-surcharging conditions. Two different novel configurations were tested; (1) With and without the presence of a manhole lid; (2) With and without the presence of a shallow flow on the surface. Results showed that total head losses were found to increase in surcharging conditions. The presence of the lid also marginally increased total head losses. The datasets are used to assess the performance of a numerical urban flood model (SIPSON) and comparisons highlighted that SIPSON tends to overestimate energy losses in surcharging conditions.     

The importance of gully flow modelling to urban flood simulation

ABSTRACT

Urban flood simulation often ignores or simplifies the function of underground gully systems due to data and computational limitations. To discover the influence of gullies on urban flooding, a novel approach is proposed in this study, by fully-coupling a 1D gully flow model (GFM), a 1D sewer flow model (SFM), and a 2D overland flow model (OFM) to simultaneously simulate the flow exchanges between surface, gullies and sewer pipes. This fully-coupled approach is compared with a simplified approach which directly introduces surface water into sewer pipes without being via gullies. The validation results show that the fully-coupled approach considerably reduces the underestimation of flood extent by 27% compared with the simplified approach. Without considering the capacity of lateral tubes between gullies and sewer pipes, the simplified approach over-drains the surface water into sewer pipes. The modelling of gully flow is crucial for correctly evaluating the efficiency of drainage systems.     

Optimization of sewer networks using the mixed-integer linear programming

This paper introduces a method for optimizing sewer networks using the mixed-integer linear programming (MILP) for a given layout. The objective function is defined as the sum of the costs for pipe purchase, pipe-laying, and manhole construction expressed in linear terms and subject to minimum and maximum allowable slopes, velocities, and relative depths for both minimum and maximum sewage discharge rates in each pipe. Additionally, provisions are made as constraints or conditions to ensure that a minimum pipe cover is required, that pipe diameters do not decrease in the flow direction, and that pipes maintain a steady elevation at each manhole. All the non-linear constraints are transformed into the linear format. Pipe slope, binary variables accounting for commercial pipe diameters and average implemented depths have also been considered as decision variables. Finally, the performance of the proposed optimization method is evaluated in a benchmark sewer network from the literature.     

Numerical simulation of wind flow near a forest edge

This paper presents a computational fluid dynamics (CFD) model to simulate wind flow near a forest edge for the purpose of wind energy applications. The model uses a porous media analogy combined with a modified k–ε turbulence model to simulate momentum losses and turbulence generation within the forest. The momentum losses are represented by a drag coefficient and a leaf area density. Two directions were investigated: wind flow entering and wind flow leaving the forest. A fully developed solution with original boundary conditions was used as the inlet boundary condition in the two-dimensional CFD model for wind flow leaving the forest. Original boundary conditions were also proposed for the ground boundary within the forest. The model was solved using FLUENT 6.2 and validated against field measurements from three different authors. A sensitivity analysis was performed on two key parameters: drag coefficient and leaf area density. The results obtained using the proposed method show good agreement with the wind velocity and turbulence intensity measured experimentally.     

寒区隧道地源热泵型供热系统岩土热响应试验

 为解决寒区隧道冻害问题,将地源热泵型供热系统应用于内蒙古博牙高速林场隧道中。通过开展寒区隧道地源热泵供热系统岩土热响应试验,研究热交换管管内循环介质的入口温度、流量和管间距对换热量的影响以及热交换对隧道围岩和衬砌温度场的影响。试验结果表明：管内循环介质的流量一定时,换热量随着入口温度的增加而呈线性增加;管内循环介质的入口温度一定时,换热量随着流量的增加而呈指数增加。增加流量可以提高热交换管内循环介质的换热能力,但却增加管内循环介质与管壁之间的阻力,建议热交换管管内循环介质流量不宜超过0.75 m3/h。热交换管间距为100和50 cm时,围岩温度场的影响深度分别约为75和100 cm。热交换管间距越小,围岩温度场的影响范围则越大,温度增量也越大。     

Uplift of Sewage Manholes and Pipes During the 2004 Niigataken-Chuetsu Earthquake

About 1,400 sewage manholes were uplifted during the 2004 Niigataken-chuetsu earthquake in Japan. Many buried sewage pipes were also uplifted. Before the restoration work, detailed soil investigations were carried out to reveal the mechanism of the uplift. Based on the investigations, it was clarified that uplift occurred in mainly clayey grounds. No sand boils were observed on the clayey ground. However, boiled sands were observed just beside the uplifted manholes and above the buried pipes. During the construction of buried pipes and manholes, the ground was excavated first, the pipes and manholes were placed in the ditches, then the ditches were filled with sand. The soil investigation of the sand fill after the earthquake revealed that the sands were very loose and easy to liquefy. It was concluded that the uplift of the manholes and pipes occurred due to the liquefaction of the sand fill. In preparation for the restoration work, appropriate countermeasures for future earthquakes were discussed, and finally, the cement mixing method was selected.     

新型装配式预制混凝土圆形电力工作井的设计与制作

电力工作井的预制化、装配化是我国电力管沟施工机械化发展的方向。研发了一种新型的装配式预制混凝土圆形电力工作井。根据实际工程需求,提出了相应的模块化方案和结构设计方案,可适应多种入孔所处地形条件。通过有限元计算对结构整体和装配连接部位进行了细致的分析。设计制作了相应的模板并最终制作了一个足尺结构。结果表明,采用等同设计进行结构整体设计再对连接部位进行细部加强的举措,可以使得该结构满足实际工程需求。模块化设计可以有效地减少预制、运输和现场机械化施工成本,并缩短施工周期。     

城镇排水系统设计与运行中的若干问题探讨

按照传统规范设计的排水系统,在实际运行中存在很多问题,不便于维护管理。为此对雨水系统设计运行中的以下内容提出了改进措施:雨水口和淹没出水口的设置,在适当位置铺设雨水系统的连通管,积水严重段临时增设直通污水检查井的雨水口,合理铺设住宅区雨水系统、加快雨洪资源利用的推广应用等。另外,还对污水系统中的以下内容提出了改进措施:设计运行改进检查井构造,在适当位置铺设污水管系统之间的连通管,铺设污水厂进水总管复线,闸槽井做法,旧泵站集水池有效容积和最低水位线的确定,污水厂的规模和效率,排水体制的确定等,可供相关人员参考。     

Experimental study of cooling water pipe circuits by theoretical and numerical analysis in a reactor vault

Our aim is to study the heat transfer processes in a cooling circuit. In this project, a mild steel plate of 1.1 m?×?1.1 m?×?6 mm dimensions is used. Square pipes are embedded in a liner plate, through which the water is circulated to remove heat from the reactor vault. To improve the contact between the pipes and the liner, the pipes are welded to the liner throughout their length. A heater plate simulating main vessel was placed, and the electrical heaters were laid all over the inner surface of main vessel. The square pipes were made to let the water flow through them, and the flow rate is set using a flow meter and this water is heated by convection and it is condensed by passing through a heat exchanger. Thermocouples are fixed at different locations of cooling pipes, the liner and the water inlet/outlet.