Search Results (26)

This study aims to analyse the effect of partially clogged inlets on the behaviour of urban drainage systems at the city scale, particularly regarding intercepted volumes and flood depths. The main challenges were to represent the inlet network in detail at a rather large scale and to avoid the effect of sewer network surcharging on the draining capacity of inlets. This goal has been achieved through a 1D/2D coupled hydraulic model of the whole urban drainage system in La Almunia de Doña Godina (Zaragoza, Spain). The model focuses on the interaction between grated drain inlets and the sewer network under partial clogging conditions. The model is fed with data obtained on field surveys. These surveys identified 948 inlets, classified into 43 types based on geometry and grouped into 7 categories for modelling purposes. Clogging patterns were derived from field observations or estimated using progressive clogging trends. The hydrological model combines a semi-distributed approach for micro-catchments (buildings and courtyards) and a distributed “rain-on-grid” approach for public spaces (streets, squares). The model assesses the impact of inlet clogging on network performance and surface flooding during four rainfall scenarios. Results include inlet interception volumes, flooded surface areas, and flow hydrographs intercepted by single inlets. Specifically, the reduction in intercepted volume ranged from approximately 7% under a mild inlet clogging condition to nearly 50% under severe clogging conditions. Also, the model results show the significant influence of the 2D mesh detail on flood depths. For instance, a mesh with high resolution and break lines representing streets curbs showed a 38% increase in urban areas with flood depths above 1 cm compared to a scenario with a lower-resolution 2D mesh and no curbs. The findings highlight how inlet clogging significantly affects the efficiency of urban drainage systems and increases the surface flood hazard. Further novelties of this work are the extent of the analysis (city scale) and the approach to improve the 2D mesh to assess flood depth. Full article

Stormwater runoff containing road deicing salts has led to the increasing salinization of surface waters in northern climates, and urban municipalities are increasingly being mandated to manage stormwater runoff to improve water quality. We assessed chloride concentrations in runoff from late-winter snowmelt and rainfall events flowing into an urban Minnesota, USA, lake during two different years, predicting that specific stormwater drainages with greater concentrations of roadways and parking lots would produce higher chloride loads during runoff than other drainages with fewer impervious surfaces. Chloride levels were measured in runoff draining into Lake Winona via 11 stormwater outfalls, a single channelized creek inlet, and two in-lake locations during each snowmelt or rainfall event from mid-February through early April in 2021 and 2023. In total, 33% of outfall runoff samples entering the lake collected over two years had chloride concentrations exceeding the 230 ppm chronic standard for aquatic life in USA surface waters, but no sample exceeded the 860 ppm acute standard. Chloride concentrations in outfall runoff (mean ± SD; 190 ± 191 ppm, n = 143) were significantly higher than in-lake concentrations (43 ± 14 ppm, n = 25), but chloride levels did not differ significantly between snowmelt and rainfall runoff events. Runoff from highway locations had higher chloride concentrations than runoff from residential areas. Site-specific chloride levels were highly variable both within and between years, with only a single monitored outfall displaying high chloride levels in both years. There are several possible avenues available within the city to reduce deicer use, capture and treat salt-laden runoff, and prevent or reduce the delivery of chlorides to the lake. Full article

Surface runoff flows must be drained safely through culverts in ephemeral flow streams and bridges in perennial streams without any damage to the road or highway infrastructure stability. In practice, bridges cross drainage basin channels reliably, and they are more carefully planned, designed, constructed, and maintained against extreme water passages, but culverts are subject to even less frequent and intensive rainfall consequent surface runoff occurrences with higher risk potential. It is, therefore, necessary to design culverts more carefully in such a way that they drain down the upstream surface water without any critical problem to the road downstream of the road stream channels. Most of the hydrological, hydraulic, and sedimentological formulations are empirical expressions that are widely valid for locations where culverts are suitably developed based on simple bivalent logical rules between factors involved in upstream inlet locations of culverts. One of the first logic rule-based methods in the literature is Talbot’s procedural approach to culvert design. This approach is based not only on an explicit equation, but also on a set of linguistically proposed design rules that are expressed deterministically to effectively eliminate most of the ambiguities. This paper proposes a modified approach with additional logistic structural features based on a bivalent logic inference system, which is an improved version of the Talbot procedure and leads to better culvert transition surface flow prediction. The proposed method is applied to a local area in Tekirdağ City, Türkiye, where a serious train accident occurred due to a poorly maintained culvert. Full article

Existing surface inlets behind terraces and water and sediment control basins (WASCoBs) were replaced with alternative tile intakes (ATIs) in agricultural fields of southeast Iowa. These ATIs consisted of a buried column of gravel atop woodchips. Computational, experimental, and field methods were used to design and evaluate the ATIs’ capacity to reduce sediment and nutrient export. Single-storm simulations using the Watershed Erosion Prediction Project (WEPP) provided boundary conditions for permeameter experiments that yielded a hydraulic conductivity for the layered gravel–woodchip configuration of 4.59 cm/s ± 0.36 cm/s. Additionally, a proportional amount of sediment was retained in the permeameter (42%) compared to the amount that settled on the permeameter surface (58%). Event monitoring of field-installed ATIs during three growing seasons measured a sediment trapping efficiency of 86 ± 12% that led to deposition rates of 5.44 ± 3.77 cm/yr, quantified with ²¹⁰Pb profiles. Percent reduction values were 43% for nitrate and 17% for ortho-phosphate. Finally, long-term continuous-storm modeling using the WEPP suggested that these ATIs could withstand at least 75 25-year events before clogging. Modeling using the Agricultural Conservation Planning Framework suggested watershed-scale load reductions of 1.6% for NO₃ and 1.4% for total P for ATIs draining 6.8% of the modeled watershed. Using ATIs in conjunction with WASCOBs and terraces, or as standalone practices, can be a cost-effective means for keeping sediment and nutrients in the landscape. Full article

Centrifugal Partition Chromatography (CPC) utilizes a two-phase liquid–liquid system as mobile and stationary phases. During operation, the latter continuously drains out of the rotor, despite it being in fact stationary, leading to decreasing separation efficiency over time, a phenomenon still poorly understood today because neither simulations nor extensive experimental investigations have addressed this so-called bleeding. With the model presented in this study, the underlying hydrodynamics are discussed in detail. This model can simulate bleeding over 60 s and is verified experimentally for different operating points (volumetric flow rates of 5, 12, and 20 mL⋅min⁻¹) of the Centrifugal Partition Chromatograph utilizing an aqueous–organic phase system. We simulated two interconnected chambers at the rotor inlet and analyzed the loss of the stationary phase over time. The results of the simulated second chamber are closely aligned with the experimental validation results. Thus, the prediction of bleeding utilizing the simulation of hydrodynamics was successful. Moreover, we highlighted the benefits of the two-chamber setup modeled in this study compared to single-chamber models. Full article

Despite the importance of critical infrastructure for the effective functioning of communities, their vulnerability to tsunamis remains unstudied. This study addresses this issue by developing empirical fragility curves for infrastructure components currently absent from tsunami vulnerability research. This research applies post-event damage data from the 2015 Illapel tsunami in a cumulative link model (CLM) to form fragility curves for three-waters (manholes, culverts, and drain inlets) and railway infrastructure components. The synthesized fragility curves reveal that in response to the flow depth, culverts exhibit the highest vulnerability of all the infrastructures studied. The curves also suggest that culverts, drain inlets, and railways have higher vulnerability when compared to infrastructure such as roads or utility poles. Full article

The geological resources of salt cavern gas storage in China are mostly complex layered salt beds with many thin inter-layers and high insoluble matter content. In the process of cavity-building by water-solution method, the insoluble matters in salt layers and inter-layers are peeled off and deposited at the bottom of salt cavern, occupying more than one-third of the whole cavity volume. These sediments have a large pore volume and strong compressibility, and they are filled with brine; as a result, they have great potential for gas storage. The research on the flow law of brine and sediment particles in gas-driven brine drainage in the sediments of salt caverns is the basis of utilizing the void space of sediments for gas storage. In this paper, salt cores of salt cavern gas storage wells in the Jintan District were selected, and the physical characteristics of insoluble sediments of the salt cores were analyzed. Then, a laboratory simulation device and experimental method of the gas-driven brine drainage were presented. Using artificial composite sediments in the experimental device, the following was tested: (i) the flow rates of brine and particles in the vicinity of the brine drain pipe in the sediments under different nitrogen displacement pressures, (ii) the relationship between the sand extraction amount and nitrogen displacement pressure of different brine drain pipes, (iii) the sand extraction amount of different sizes of particles with brine drain time, (iv) the cumulative sand extraction amount of different brine drain pipes, and (v) the effect of brine flow rate on the sand extraction amount. The results show that quartz, plagioclase, and ankerite account for 45–94% and clay accounts for 3.3–14.4% of the insoluble minerals of the salt cores from the Jintan District. The particle size distribution of the sediments ranges from 0.04 mm to 6 mm and can be divided into four ranges: <0.5 mm, 0.5 mm~2 mm, 2 mm~4 mm, and >4 mm. The mass percentage of each range is 37.9%, 36.5%, 17%, and 8.6%, respectively. There is a threshold pressure of the gas-driven brine drainage, where the larger the diameter of the sieve hole, the lower the threshold pressure, and the easier the pipe is to sand out. The diameter of the sieve hole has a great influence on the flow rate of the sediment particles near the brine drain pipe. The increase in nitrogen displacement pressure has a positive correlation with the flow rate of sediments near the pipe with 5 mm diameter sieve holes, but has little effect on the flow rate of sediments near pipes with 1.5 mm or 0.5 mm diameter sieve holes. The sand extraction amount is affected by factors such as the nitrogen displacement pressure, diameter of sieve hole, brine drain time, and brine flow rate in the process of gas-driven brine drainage. A higher nitrogen displacement pressure and brine flow rate lead to more sand extraction. A screen pipe with 1 mm diameter sieve holes is suggested to be used for sand control, the sieve holes are recommended to be machined in the shape of a trumpet with a small inlet section (i.e., 1 mm) and a large outlet end (i.e., 1.5 mm), and the brine flow rate is suggested to be about 30 m³/h when the brine removal is carried out in the sediments of salt cavern, which depends on the actual operation on site. Full article

To investigate the impact of parameters of diversion wall holes on the flow state in the forebay of a combined sluice-pumping station project and optimize the relevant parameters, a total of 50 numerical simulations based on the CFD technique were performed, adopting the design of orthogonal experiments with 25 schemes under self-draining conditions and pumping conditions, respectively. For synthesizing flow state evaluation indicators under self-draining and pumping conditions, the variation coefficient method was used, and the results were analyzed through the response surface method. Thus, the relationship between the parameters of the diversion wall holes and the comprehensive evaluation indicator was established. The steepest ascent method was used to obtain the optimal parameters, and the results showed that the optimized holes can balance the flow state under self-draining and pumping conditions in the combined sluice-pumping station project. Compared to the case with the diversion wall unperforated, the uniformity of axial velocity distribution in the 6# inlet channel and 7# sluice chamber increased by 6.6% and 5.2%, respectively, and the maximum transverse velocity decreased from 0.32 m/s to 0.21 m/s, with a fall of 34.4%. This study provides reference and technical support for the hydraulic characteristic analysis, optimization design and rectifying measures selection of the combined sluice-pumping station project. Full article

Automatic flushing valve (AFV) can improve the anti-clogging ability of the drip fertigation system. The minimum inlet pressure (H_amin) required for automatic closing and the maximum flushing duration (FD_max) are two important performance indexes of AFV. The existing AFV products have the problem of larger H_amin and smaller FD_max, which result higher investment and operating cost, and poor flushing efficiency. Based on the mechanical analysis of the AFV elastic diaphragm and the derivation of the FD, elastic diaphragm hardness (E), ascending channel offset distance (D), and drain hole width (W) were selected as the experimental factors, and nine AFVs were designed by L₉(3³) orthogonal test method to investigate the influence of elastic diaphragm hardness and structural parameters on the hydraulic performance of AFVs. The hydraulic performance test results showed that the H_amin of the nine AFVs ranged from 0.026 to 0.082 MPa and FD_max ranged from 36.3 to 95.7 s. H_amin was positively correlated with E and D and negatively correlated with W. FD_max was negatively correlated with E and W and tended to increase and then decrease with D. All elastic diaphragm hardness and structural parameters had a significant effect on H_amin, and E and W had a significant effect on FD_max. Based on the range analysis, two new combinations of AFV elastic diaphragm hardness and structural parameters with minimum H_amin (E = 40 HA, D = 0 mm, W = 2 mm) and maximum FD_max (E = 40 HA, D = 2 mm, W = 1.68 mm) were determined, and the corresponding H_amin was 0.022 MPa, 63.3% lower than that of the existing product, and FD_max was 116.4 s, 71.2% higher than that of the existing product. In this study, two ternary nonlinear mathematical regression models of H_amin and FD_max with elastic diaphragm hardness and structural parameters was constructed. The simulation accuracy of the models is good and can be used to quickly predict the optimal combination of AFV parameters to satisfy the actual engineering-required H_amin and FD_max. Full article

Water–gas displacement occurring during the drainage of water-soaked goafs facilitates the oxidation of water-soaked coal. The characteristics of oxygen migration and the oxidation and spontaneous combustion (SC) of soaked residual coal during goaf drainage were explored through laboratory research, water drainage simulation and on-site measurement. The results reveal that compared with raw coal samples, the amount and rate of gas products of water-soaked coal samples are higher in the heating oxidation process, demonstrating a strengthened spontaneous combustion (SC) propensity. Its cross-point temperature falls and the apparent activation energy decreases by 1.43–8.75%, that is, the soaked coal sample is easier to spontaneously combust during the drainage of water-soaked goafs. Through simulation, it is found that after water is drained, air leakage in the goaf is significantly intensified, and the pressure difference inside and outside the goaf reaches 498 Pa. By taking the air inlet roadway as the air leakage point for fitting, it is found that the oxygen concentration in the air leakage range increases to 18% during water drainage. The simulation results are basically consistent with the on-site measurement. The on-site monitoring result shows that during water drainage of 7₂25 goaf in Qinan Coal Mine, water-immersed coal is more prone to spontaneous combustion, and air leakage leads to low-temperature oxidation of water-immersed coal, which increases the on-site temperature rapidly and increases the risk of spontaneous combustion in the goaf. With respect to water drainage in the goaf, an optimization measure of fixed-point and quantitative nitrogen injection during water drainage was put forward on site. Full article

A roadway’s capacity to drain itself is of utmost importance for the safety and comfort of its users. Standing water and any amount of channelized flow on roadways create nuisances to the users, and the extent of encroachment into the lanes and the water-film thickness over the lanes are crucial for motorists with relatively high speed. Guidelines cover a wide range of subjects from size and type of inlets, which capture the channelized flow for conveyance into enclosed drains, to the decision for slope orientation, but the guidelines seem to lack in checking the depth of channelized flow. HEC-22 (the urban drainage design manual of US Department of Transportation) endorses limiting the flow depths to curb height (as if the concern is no longer the roadway users) and fixes the criterion for the inlet spacing (restricted to 90 to 150 m) to maximum allowable flow spreads. This study analyzed the maximum allowable inlet spacing via setting three criteria: fixed maximums to flow depth, spread for the channel flow, and to over-lane water-film thickness. The impact of slope orientation on inlet spacing is tested along with some other factors for roadways of two types (local and highway). The results were graphed for various uniform slope orientations under a wide range of rainfall intensities for the determined inlet spacing values. This was performed by combining a kinematic wave equation solution to dismiss the conditions that lead to hydroplaning depths when using the Rational Method and Manning’s equation to obtain water depths and inlet spacings for an inlet of full capture capacity. It is found that the allowable spacing values do not constitute any major restrictions in highway setting (3 m shoulder) in terms of recommended spacing. In the local setting, however, with a maximum spread of 1.8 m, maximum allowable inlet spacing becomes a limitation in many orientations, and slope optimization under such conditions becomes crucial at times when providing the same spacing for two orientations. Full article

Cryogenic turbopumps are used in high-performance, lightweight liquid rocket engines for space applications. The development of bearings and shaft seals for cryogenic turbopumps requires detailed characterization of the internal flow, taking into account the effects of boiling and multi-component two-phase flow. Here, a flow network solver was developed to analyse the secondary flow circuit of a cryogenic turbopump where the propellant is mixed with high-temperature helium after bearing cooling. The network solver is based on an extension of a classic 1D homogeneous model, originally developed for a pure substance, to the case of two-phase multi-component flow. The solver is capable of predicting pressures, temperatures, flow rates, and species concentrations in a complex two-phase flow in the presence of non-condensable gases. The unsteady mass, momentum, and energy conservation equations are implemented in conjunction with the thermodynamic equations of state using a general-purpose finite volume formulation, where the pressure drop and the heat transfer are calculated using correlations. The numerical tool was validated by comparing its predictions with experimental data obtained during tests on the secondary circuit of an oxygen turbopump developed at Avio S.p.A. A number of engine operating conditions were considered (inlet helium temperature in the range of 250–280 $\mathrm{K}$, helium/liquid oxygen drain in the range of 165–230 $\mathrm{K}$). The predicted temperature values showed good agreement with the experimental data in most conditions. Full article

Urban rainstorm drainage systems are used to collect the surface runoff from streets and other land surfaces through grate or curb openings that convey it to the drains. The quantity of surface runoff that is not discharged to the urban rainstorm drainage systems due to inadequate grate size or because the grate capacity is exceeded can cause flooding, immoderate hazards to drivers and pedestrians, and disrupt urban activities. This study aims to carry out experimental work to investigate the hydraulic efficiency of urban rainstorm drainage systems using different types of grates (shape and size of inlet area) for harvesting excess rainwater. Different grate shapes (five) with different inlet areas were investigated, as well as using three relative grate inlet areas (26%, 51%, and 64%). The results of the experimental work indicated that the best grate shape is the grate type 4 which provided the smallest reduction in discharge efficiency within 8.7%. The results specified that changing the size of the inlet area of grates from (26%) to (64%) has a significant impact on urban rainstorm drainage systems efficiency which decreased by 4%. In addition, the dimensional analysis principle with multi regression analysis were used to develop an empirical equation to compute the efficiency of urban rainstorm drainage systems. The relation between grate shapes and the relative inlet area with the efficiency of grate capture provides an indication to the decisionmakers to increase the time period for maintenance which will save the cost for further maintenance. The presented empirical equation can help decisionmakers for monitoring the current situation of grate blockage (relative grate inlet areas) and the corresponding efficiency. This study is beneficial for future road drainage system construction to avoid problems by assessing the performances of the current drainage systems and proposing mitigation measures to avoid improper functioning. Finally, this methodology can help to improve the efficiency of urban rainstorm drainage systems that can reduce the risks of urban floods. Full article

Vapor-liquid separation during condensation enables the enhancement of heat transfer coefficient and reduction in pressure drop simultaneously. The vapor-liquid separator is vital to the performance of such a liquid-separation condenser (LSC). It should fulfill the functions of allowing the condensate to drain away as much as possible from the separator and leaving only vapor to continue condensing afterwards. However, due to the intensive interactions between the liquid and vapor, it is really hard to achieve perfect vapor-liquid separation, adding new uncertainties to the maldistributions in the branch outlets of a parallel condenser. To discover more insights of the flow conditions in the header and phase distributions, the characteristics of the orifice-baffle header are studied by using CFD and the mechanistic model for the droplet analysis is established by means of force balance in this paper. A parametrical analysis is carried out to discover the effects of operating conditions. It is found that the maximum vapor-liquid separation efficiency (η) is 51.94% as the inlet mass flow rate (ṁ_in) is 12 g/s. The vapor leakage from the orifice because of the liquid impact is one of the main reasons that deteriorate the vapor-liquid separation performance. Moreover, the vortex in the header increases the local mass flux, thereafter decreasing the droplet diameter. With the increasing of ṁ_in, the dominant force of the droplet in the vertical direction switches from F_G to F_D2. Full article

To ameliorate the inflow state of the joint hub of a pump station and sluice, a γ-shaped settlement training wall was designed with its state adjusted automatically in line with the actual working condition of the project. The central composite design (CCD) of the response surface method was adopted to optimize the geometrical size of the training wall in the operational states of pumping and free-draining separately. The results showed that the alteration of different size factors of the γ-shaped settlement training wall had different degrees of influence on its rectification effect; the intake flow state of the joint hub of the sluice and pumping station with the γ-shaped settlement training wall can be significantly improved with the flow velocity uniformity in the inlet channel next to the junction of the sluice chamber, reaching 80.42%, and the flow velocity uniformity ahead of the sluice, reaching 84.78%, in the operational state of free-draining. By combining the results of numerical simulation, the feasibility of the response surface method was further verified and the optimal combination of geometric parameters of the γ-shaped settlement training wall were also obtained, which can be adopted in the design of the actual joint hub of the pump station and sluice. Full article