Effect of manhole molds and inlet alignment on the hydraulics of circular manhole at changing surcharge

1. In intakes of the upper reservoirs of pumped-storage stations for straight variants and for layouts with bends (R=4dc) the coefficients of head losses in the pump operating regime are 2–3 times greater than in the turbine. 2. The experimental value of the coefficient of head losses ξplexy, taking into account losses in the intake proper and in the bend located behind it, in the pump regime, as a rule, differs substantially from the sum ξplexy=0+ξt.b.calc of the experimental value of the coefficient of losses of a straight intake and coefficient of head losses in the bend calculated by the recommendations given in the literature. This is due to the fact that the bend affects the value of losses in elements of the intake located above it. Therefore, a reliable value of the resistance coefficient of an intake with a bend in the pump regime can be obtained only experimentally. In the turbine operating regime the coefficients ξtlexy and ξtlexy=0+ ξt.b.calc for intakes with a bend differ among themselves by less than 12%. 3. Intakes with various degrees of expansion and transition section 2 from a circle to a rectangle (b=1.67dc, h=dc) located between the bend and intake proper have smaller head losses than intakes with transition section 1 from a circle to a square (b=h=dc) for all angles of turn of the bend (γ=0–90°) both in the pump and in the turbine regimes. 4. In intakes with transition section 1 (b=h=dc) in the pump regime the total losses, including also the losses in the bend, increase with increase of γ of the bend. In more extensive intakes with transition section 2 (b=1.67dc, h=dc) straight layouts (γ=0) have minimum losses; in the presence of a bend with γ=25° and γ=90° the coefficients of head losses are practically the same and, on average, are 45% greater than when γ=0, and when γ=60° are 4.5–10.5% less than when γ=25 and 90°. 5. In intakes with bends (R=4dc) of rectangular section (b=1.67dc, h=dc) with an area 2.12 times greater than the area of the conduit and transition 2 located between the conduit and bend, in the pump regime the coefficient of head losses are 1.4–1.5 times less than in intakes with bends of circular section (d=dc) for all investigated angles of turn of the bend. 6. In the turbine operating regime the total coefficients of head losses increase with increase of the angle of turn of the bend.

ABSTRACTThe head loss caused by the surcharged flow from four-way junction manholes is the main cause of increased flood damage in urban areas. The flow pattern significantly varies depending on the inflow conditions of the inlet pipes and constitutes the flow conditions of a four-way junction manhole, three-way junction manholes, and middle manholes. Therefore, the head loss changes with various manhole shapes must be analyzed. In this study, physical model study apparatus was prepared. Various flow rate conditions were selected by changing the flow rate ratios of the inlet pipes at 10% intervals. The head loss coefficients were also estimated. A head loss coefficient range diagram was generated based on the results. A head loss coefficient empirical formula that considers all flow conditions for surcharged four-way junction manholes is proposed. The proposed equation should be applicable to the design and assessment of drainage systems with varying inlet pipe flow rates.

For the different types of throttled surge tanks used in hydropower systems, it is important to comprehensively know the throttle's head loss characteristics for exact surge analysis and transient control. Herein, a general and complete experimental setup was designed to steadily reproduce the 12 typical flow regimes occurring at the surge tank and thus conduct comprehensive experimental research on throttle head loss coefficients. Furthermore, an extended mathematical model for the surge tank was derived by inputting experimental data on the throttle's head loss coefficients to surge analysis. Through experimental research, the throttle's head loss coefficients were determined by fitting formulae relative to the different flow regimes and discharge ratios; via a detailed case analysis, the differences in the head loss characteristics for different throttle types were accurately determined. It was demonstrated that the throttle's head loss coefficient varies with discharge ratio under different flow regimes and found that the experimentally obtained flow coefficients for different throttle types are more accurate and clearly reveal the difference of throttles’ head loss characteristics. The extended mathematical model for the throttled surge tank can provide more accurate simulation results and guidance for its engineering design and layout.

The loss coefficient is one of the most critical parameters in computing the hydraulic grade line of sewer systems. The head loss coefficient of a manhole is dependent on various hydraulic and structural characteristics, such as manhole mold, connection angle, and the ratio of manhole diameter to pipe diameter. Three different manhole molds, flat, half-bench, and full-bench, and connection angles of 180°, 90°, and 135° are investigated, where the manhole diameter to pipe diameter ratio is 5.3. This paper presents the results of experimental and numerical investigations focused on determining the loss coefficient for two-way straight-through and angled manholes. The flow structure inside the chimney is the significant parameter for the magnitude of the energy loss coefficient. The head loss coefficient is almost constant under the surcharged flow conditions for all kinds of manholes. In terms of head loss coefficients, half-channel manholes do not have a significant advantage over flat-bottomed manholes in the cases of 135° and 90° flow inputs. The full-bench bottom manhole head loss coefficient is the smallest. The computational fluid dynamic modeling results agree with the experimental studies.

Cavitation effects in valves and other sudden transitions in water distribution systems are studied as their better understanding and quantification is needed for design and analysis purposes and for predicting and controlling their operation. Two dimensionless coefficients are used to characterize and verify local effects under cavitating flow conditions: the coefficient of local head losses and the minimum value of the cavitation number. In principle, both coefficients must be determined experimentally, but a semianalytical relationship between them is here proposed so that if one of them is known, its value can be used to estimate the corresponding value of the other one. This relationship is experimentally contrasted by measuring head losses and flow rates. It is also shown that cavitation number values, called cavitation limits, such as the critical cavitation limit, can be related in a simple but practical way with the mentioned minimum cavitation number and with a given pressure fluctuation level. Head losses under conditions of cavitation in sharp-edged orifices and valves are predicted for changes in upstream and downstream boundary conditions. An experimental determination of the coefficient of local head losses and the minimum value of the cavitation number is not dependent on the boundary conditions even if vapor cavity extends far enough to reach a downstream pressure tap. Also, the effects of cavitation and displacement of moving parts of valves on head losses can be split. A relatively simple formulation for local head losses including cavitation influence is presented. It can be incorporated to water distribution analysis models to improve their results when cavitation occurs. Likewise, it can also be used to elaborate information about validity limits of head losses in valves and other sudden transitions and to interpret the results of head loss tests.

Head losses at sewer pipe junctions have been studied in a model. The junction geometry was varied by using manholes of different widths and cross-sections, and by using various arrangements inside the manholes. The pipe diameter and alinement upstream and downstream of the junction were identical. In all experiments, pipes were flowing under pressure, but a free water surface was maintained inside the junction manhole. Observed piezometric heads and flow velocities served to calculate the upstream and downstream energy grade lines and the junction head loss. The head loss was found to increase linearly with the increasing velocity head and the observed experimental relationship was therefore approximated by a regression line. The head loss coefficient was then determined as the slope of the regression line. Head loss coefficients are presented for nine cases studied.

In general, XP-SWMM regards manholes as nodes, so it can not consider local head loss in surcharged manhole depending on shape and size of the manhole. That might be a reason why XP-SWMM underestimates inundated-area compared with reality. Therefore, it is necessary to study how we put the local head loss in surcharged manhole in order to simulate storm drain system with XP-SWMM. In this study, average head loss coefficients at circular and square manhole were estimated as 0.61 and 0.68 respectively through hydraulic experiments with various discharges. The estimated average head loss coefficients were put into XP-SWMM as inflow and outflow energy loss of nodes to simulate inundation area of Gunja basin. Simulated results show that not only overflow discharge amount but inundated-area increased considering the head loss coefficients. Also, inundation area with considering head loss coefficients was matched as much as 58% on real inundation area. That was more than simulated results without considering head loss coefficients as much as 18 %. Considering energy loss in surcharged manholes increases an accuracy of simulation. Therefore, the averaged head loss coefficients of this study could be used to simulate storm drain system. It was expected that the study results will be utilized as basic data for establishing the identification of the inundation risk area.

The head loss is a decrease in compressive height caused by friction and direction changes of flow at the sliced bend. This method expected to provide is easy, fast, and economical. The elements of influence are the velocity of flow, the num-ber of slices, average length of sliced walls, angle changes of the sliced, coefficient of friction, acceleration of gravity, and slope of the pipe. Equation for coefficient of head loss (Kb) is an analysis method for the head loss (hL) calculation. The analysis results that have obtained are the larger diameter of the pipe, and the more slices with a fixed discharge, the coefficient of hL becomes small. Conversely, if the diameter of the pipe is getting smaller, and the slice is getting less, then the coefficient of hL becomes bigger. This method, expected to give new knowledge in pipeline network applications, especially for the large diameter of pipelines.

An experimental investigation into the passive damping properties of various fluids, including magnetorheological (MR) fluid, in a tuned liquid column damper (TLCD) is undertaken. The coefficient of head loss for different fluids used in TLCDs to reduce structural responses in single-degree-of-freedom (SDOF) structures subjected to base excitation is experimentally determined. Experimental results are used to calculate the nonlinear coefficient of head loss based on a theoretical formulation. The numerical simulations of the responses of the structure-TLCD system with various fluids used in TLCDs are validated with the experimental results. Water has traditionally been used in TLCDs although semiactive control and additional functional requirements (antifreezing) of TLCDs can be achieved with MR fluids and glycol as resident TLCD liquids, respectively. The semiactive MR-TLCD works by utilizing the ability to change the damping properties (i.e., head loss) of the MR fluid by applying a magnetic field within the TLCD. However, the effectiveness of the MR-TLCD relies upon an adequate movement of the MR fluid within the TLCD (for both tuning and damping through head loss). Hence, an investigation into the passive damping properties of an MR fluid as the residing liquid within the TLCD is imperative for semiactive MR-TLCDs to be realizable. The performances of water, glycol, and a MR fluid are compared and the merits of each of the fluids in providing adequate passive damping to the structural system are discussed. The equivalent viscous damping in the structure provided by the TLCDs using each of the fluids is obtained for both harmonic and broad banded excitations. The theoretical analysis also examines if the existing TLCD theory may be implemented to accurately describe the passive damping performance of the MR-TLCD.

Characteristics of multiple tuned liquid column dampers in suppressing structural vibration

도시 우수 배수 시스템에서 우수 관거는 개수로 흐름 상태로 가정하여 설계되었기 때문에 맨홀에서의 에너지 손실은 일반적으로 중요하게 고려되지 않았다. 그러나 과부하흐름에서 에너지 손실은 관거의 배수능력을 저하시켜 도심지역의 침수피해를 가중시키는 요인이 된다. 그러므로 과부하 사각형 맨홀 내에서의 수두 손실을 분석할 필요가 있다. 본 연구에서는 FLUENT 6.3 모형을 이용하여 과부하 사각형 합류맨홀에서의 흐름특성을 모의하고 맨홀 내 손실수두의 변화를 계산하여 손실계수를 산정하였다. 또한 실험결과와 수치모의 결과를 비교 및 분석하여 사각형 맨홀에서의 손실계수 산정에 FLUENT 6.3모형의 적용성을 확인하였다. 맨홀 폭(B)과 연결관경(d)의 비(B/d)에 따른 손실계수를 산정하였다. B/d가 증가할수록 사각형 합류 맨홀에서의 손실계수는 증가하였다. 중간 단차 맨홀에서 단차 변화에 따른 손실계수의 변화를 산정하였다. 단차가 5 cm이상 증가하면 맨홀 내 수심과 손실계수가 점진적으로 증가하였으므로 중간 맨홀에서의 적정 단차는 5 cm로 판단된다. 따라서 우수 관거 시스템의 여러 형태의 사각형 맨홀에서의 흐름의 변화 및 손실계수를 예측할 때, Fluent 6.3 모형은 사용 가능하리라 판단된다. Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban area. Therefore, it is important to analyze the head losses at manholes, especially in case of surcharged flow. The stream characteristics were analyzed and head loss coefficients were estimated by using the computational fluid dynamics(CFD) model, FLUENT 6.3, at surcharged square manhole in this study. The CFD model was carefully assessed by comparing simulated results with the experimental ones. The study results indicate that there was good agreement between simulation model and experiment. The CFD model was proved to be capable of estimating the head loss coefficients at surcharged manholes. The head loss coefficients with variation of the ratio of manhole width(B) to inflow pipe diameter(d) and variation of the drop height at surcharged square manhole with a straight-path through were calculated using FLUENT 6.3. As the ratio of B/d increases, head loss coefficient increases. The depth and head loss coefficient at manhole were gradually increased when the drop height was more than 5cm. Therefore, the CFD model(Fluent 6.3) might be used as a tool to simulate the water depth, energy losses, and velocity distribution at surcharged square manhole.

Currently, adopted runoff analysis models focus on the characteristic factors of watersheds and neglect the analysis of the flow in conduits. Additionally, the usually employed XP-SWMM modeling package generally underestimates the flood area because it considers manholes as nodes and does not consider local head losses according to the shape and size of the nodes. Therefore, it is a necessity to consider the loss coefficient in surcharge manholes to improve inundation and runoff analysis methods. This study aims at improving the accuracy of discharge analysis before analyzing the storage and runoff reduction effects of storage facilities. Hydraulic experiments were conducted according to the changes in discharge and manhole shapes. We show that the flood area increases as the overflow discharge at manhole increases due to the application of the head loss coefficient. We demonstrate a concordance rate ≥95% between results and observed flood area when accurate input data (from the parameters of the target watershed) and the head loss coefficient (from hydraulic experiments) are applied. Therefore, we demonstrate that the result of our 2D inundation analysis, considering the head loss coefficient in surcharge manhole, can be used as basic data for accurately identifying urban flood risk areas.

This study has clarified the relations between the coefficient of additional head loss and valve lifts, and the relations between the pressure distribution and valve lifts. We assume that the total head (head of valve center) is equal to the summation of frictional loss of head in the parallel plate, velocity head at outlet and additional loss of head. For those purpose we have experimented on many valves under the condition of various valve lifts and three fluids; water, kerosene and motor oil. There three fluids are used to expand the equivalent Reynolds number range. The conclusion is that the coefficient of additional head loss in nearly zero but a positive value and gets larger in proportion as valve lifts increase at the same equivalent Reynolds number in the range of the experiments. The pressure distribution at the inlet of valves does not show the same tendency as each valve and it depends on valve lifts.

The available information describing the various stages of flow conditions that occur as the flow transitions from noncavitation to cavitation (turbulent flow), supercavitation, and finally separation in sharp-edge 90 deg orifices is extensive. However, although sharp-edge orifices in cross flow represent a significant number of injection schemes inherent in many applications, data for this configuration are sparse or nonexistent. This study is intended to increase the database and understanding of the driving variables affecting the flow in all of these conditions. Tests were carried out in a unique test facility capable of achieving large variations in back pressure, flowrate, and operating upstream pressure. The configuration and test ranges of this study includes orifice length/diameter ratios from 2 to 10, upstream pressures from 7.03 kg/cm2 to 105.1 kg/cm2, orifice/manifold area ratio of 0.028 to 0.082, and manifold cross flow velocity of from 410 cm/s to 1830 cm/s. The results for these small area ratio configurations support two different first order models, one for cavitation and the other noncavitation both in turbulent flow. Under cavitation conditions the discharge coefficient is related to the contraction coefficient and the cavitation parameter to the 1/2 power. In the noncavitation flow regime the head loss is related to the loss coefficient and the dynamic pressure at the orifice exit. Both the head loss and contraction coefficient were found to be a strong function of the ratio of manifold/orifice exit velocity. Equations are provided defining the relationships that allow determination of the contraction coefficient, discharge coefficient, and head loss between the contraction coefficient, as well as the loss coefficient and operating conditions. Cavitation parameter values for cavitation inception, cavitation, and supercavitation are also provided. The potential flow theory was shown to predict the contraction coefficient when upstream (manifold to vena-contracta) losses are minimal.

Channel expansions are common in both natural and artificial open channels. With increasing cross-sectional dimensions in an expansion, the flow decelerates. Due to separation of flow and subsequent eddy formation, a significant head loss is occurred along the transition. This study presents the results of experimental investigations on subcritical flow along the expansive transition of rectangular to trapezoidal channels. Also, a numerical simulation was developed using the finite volume method with Reynolds Stress turbulent model. Water surface profiles and velocity distributions of flow through the transition were measured experimentally and compared with the numerical results. Also, hydraulic efficiency of the transition and coefficient of energy head loss were calculated. The results show that with increasing the upstream Froude number, hydraulic efficiency of the transition and coefficient of energy head loss are decreased and increased, respectively. The results also showed the ability of numerical simulation for simulating the flow separation zones and bed shear stress along the transition for different inlet discharges and inflow Froude numbers.