Water Resources
Abstract:
The digital elevation model (DEM) is a type of model that has been widely used in terrain analysis and hydrological modeling. DEM resolution influences the hydrological and geomorphologic features of delineated catchments and consequently affects hydrological simulations. This study investigated the impacts of DEM resolution on the performance of the XAJ-GIUH hydrological model, a model coupling the widely used Xinanjiang (XAJ) hydrological model with the geomorphologic instantaneous unit hydrograph (GIUH), in flood simulations in small and medium-sized catchments. To test the model performance, the model parameters were calibrated at a fine DEM resolution (30 m) and then directly transferred to the simulation runs using coarser DEMs. Afterwards, model recalibration was conducted at coarser DEM resolutions. In the simulation runs with the model parameters calibrated at the 30-m resolution, the DEM resolution slightly affected the overall shape of the simulated flood hydrographs but presented a greater impact on the simulated peak discharges in the two study catchments. The XAJ-GIUH model consistently underestimated the peak discharges when the DEM resolution became coarser. The qualified ratio of peak simulations decreased by 35% when the DEM resolution changed from 30 m to 600 m. However, model recalibration produced comparable model performances when DEMs with different resolutions were used. This study showed that the impact of DEM resolution on model performance can be mitigated by model recalibration to some extent, if the DEM resolution is not too coarse.
Abstract:
The protection zones or capture zones of springs in desert environments can be hard to identify, but they are critical to spring protection. Most springs fed by regional aquifers are susceptible to contamination and groundwater development. The U.S. Environmental Protection Agency has established hydrogeologic mapping methods to delineate protection zones for springs. However, it is often difficult to determine a regional aquifer system's flow pattern with this technique alone, and the use of these methods is not conducive to efficient groundwater management. Particle tracking analysis using a well-conceptualized and calibrated numerical model for the three-dimensional groundwater flow domain feeding a given group of springs can help facilitate the identification of spring capture zone boundaries. Building upon this basis, a multifaceted approach was developed to define clear boundaries of the capture zones for the springs in the Furnace Creek, Ash Meadows, and the Muddy River areas in the southern Great Basin, USA. Capture zones were first delineated from inverse particle tracking and Hydrologic Unit 12 watersheds. Afterwards, they were adjusted based on water budgets, geology, and hydrologically significant faults. Finally, a geochemical analysis of the groundwater chemistry and isotopic data was conducted to verify the extent of each spring capture zone. This multifaceted approach adds confidence to the new delineations.
Aquatic Environment
Abstract:
Given the difficulties of degrading benzotriazole (BTA), this study used a one-pot hydrothermal method to prepare α-Fe2O3/Cu2O (FC) composites for photoelectrocatalytic (PEC) degradation of BTA. The characterization of FC structure showed that Cu2O in cubic crystals was loaded with circular sheets of Fe2O3. Owing to this structure, FC showed efficient PEC degradation of BTA when exposed to ultraviolet light. The experimental results demonstrated that FC efficiently degraded BTA. When the PEC degradation continued for 60 min, 100% degradation of BTA was achieved because FC enhanced the photoelectron-hole separation and the separation and transfer of articulated carriers. High performance liquid chromatography–mass spectrometry showed that intermediates formed during the PEC degradation of BTA. Finally, various pathways for degradation of BTA were postulated. This FC-based PEC system provides a harmless and effective method for degradation of BTA.
Abstract:
Dissolved oxygen (DO) content is an important index of river water quality. Water quality sensors have been used in China for urban river water monitoring and DO content prediction. However, water quality sensors are expensive and difficult to maintain, and have a short operation period and difficult to maintain. This study developed a scientific and accurate method for prediction of DO content changes using fish school features. The behavioral features of the Carassius auratus fish school were described using two-dimensional fish school images. The degree of DO content decline was graded into five levels, and the corresponding numerical ranges of cluster characteristic parameters were determined by considering the opinions of ichthyologists. Finally, the variation of DO content was predicted using the characteristic parameters of the fish school and the multiple-input single-output Takagi–Sugeno fuzzy neural network. The prediction results were basically consistent with the actual variations of DO content. Therefore, it is feasible to use the behavioral features of the fish school to dynamically predict the level of DO content in water, and this method is especially suitable for prediction of sharp decline of DO content in a relatively short time.
Abstract:
Nitrate nitrogen (NO3--N) from agricultural activities and in industrial wastewater has become the main source of groundwater pollution, which has raised widespread concerns, particularly in arid and semi-arid river basins with little water that meets relevant standards. This study aimed to investigate the performance of spatial and non-spatial regression models in modeling nitrate pollution in a semi-intensive farming region of Iran. To perform the modeling of the groundwater's NO3--N concentration, both natural and anthropogenic factors affecting groundwater NO3--N were selected. The results of Moran's I test showed that groundwater nitrate concentration had a significant spatial dependence on the density of wells, distance from streams, total annual precipitation, and distance from roads in the study area. This study provided a way to estimate nitrate pollution using both natural and anthropogenic factors in arid and semi-arid areas where only a few factors are available. Spatial regression methods with spatial correlation structures are effective tools to support spatial decision-making in water pollution control.
More
Improvement of wind field hindcasts for tropical cyclones
Yi Pan, Yong-ping Chen, Jiang-xia Li, Xue-lin Ding
2016, 9(1): 58-66.   doi: 10.1016/j.wse.2016.02.002
[Abstract](1383) [PDF 0KB](1722)
摘要:
This paper presents a study on the improvement of wind field hindcasts for two typical tropical cyclones, i.e., Fanapi and Meranti, which occurred in 2010. The performance of the three existing models for the hindcasting of cyclone wind fields is first examined, and then two modification methods are proposed to improve the hindcasted results. The first one is the superposition method, which superposes the wind field calculated from the parametric cyclone model on that obtained from the Cross-Calibrated Multi-Platform (CCMP) reanalysis data. The radius used for the superposition is based on an analysis of the minimum difference between the two wind fields. The other one is the direct modification method, which directly modifies the CCMP reanalysis data according to the ratio of the measured maximum wind speed to the reanalyzed value as well as the distance from the cyclone center. Using these two methods, the problem of underestimation of strong winds in reanalysis data can be overcome. Both methods show considerable improvements in the hindcasting of tropical cyclone wind fields, compared with the cyclone wind model and the reanalysis data.
Urban and river flooding: Comparison of flood risk management approaches in the UK and China and an assessment of future knowledge needs
Matteo Rubinato, Andrew Nichols, Yong Peng, Jian-min Zhang, Craig Lashford, Yan-peng Cai, Peng-zhi Lin, Simon Tait
2019, 12(4): 274-283.   doi: 10.1016/j.wse.2019.12.004
[Abstract](416) [PDF 0KB](363)
摘要:
Increased urbanisation, economic growth, and long-term climate variability have made both the UK and China more susceptible to urban and river flooding, putting people and property at increased risk. This paper presents a review of the current flooding challenges that are affecting the UK and China and the actions that each country is undertaking to tackle these problems. Particular emphases in this paper are laid on (1) learning from previous flooding events in the UK and China, and (2) which management methodologies are commonly used to reduce flood risk. The paper concludes with a strategic research plan suggested by the authors, together with proposed ways to overcome identified knowledge gaps in flood management. Recommendations briefly comprise the engagement of all stakeholders to ensure a proactive approach to land use planning, early warning systems, and water-sensitive urban design or redesign through more effective policy, multi-level flood models, and data driven models of water quantity and quality.
Evaluation of latest TMPA and CMORPH satellite precipitation products for Yellow River Basin
Shan-hu Jiang, Meng Zhou, Li-liang Ren, Xue-rong Cheng, Peng-ju Zhang
2016, 9(2): 87-96.   doi: 10.1016/j.wse.2016.06.002
[Abstract](1398) [PDF 0KB](2599)
摘要:
The main objective of this study was to evaluate four latest global high-resolution satellite precipitation products (TMPA 3B42RT, CMORPH, TMPA 3B42V7, and CMORPH_adj) against gauge observations of the Yellow River Basin from March 2000 to December 2012. The assessment was conducted with several commonly used statistical indices at daily and monthly scales. Results indicate that 3B42V7 and CMORPH_adj perform better than the near real-time products (3B42RT and CMORPH), particularly the 3B42V7 product. The adjustment by gauge data significantly reduces the systematic biases in the research products. Regarding the near real-time datasets, 3B42RT overestimates rainfall over the whole basin, while CMORPH presents a mixed pattern with negative and positive values of relative bias in low- and high-latitude regions, respectively, and CMORPH performs better than 3B42RT on the whole. According to the spatial distribution of statistical indices, these values are optimized in the southeast and decrease toward the northwest, and the trend is similar for the spatial distribution of the mean annual precipitation during the period from 2000 to 2012. This study also reveals that all the four products can effectively detect rainfall events. This study provides useful information about four mainstream satellite products in the Yellow River Basin, and the findings can facilitate the use of global precipitation measurement (GPM) data in the future.
Application of SWAN+ADCIRC to tide-surge and wave simulation in Gulf of Maine during Patriot’s Day storm
Dong-mei Xie, Qing-ping Zou, John W. Cannon
2016, 9(1): 33-41.   doi: 10.1016/j.wse.2016.02.003
[Abstract](1342) [PDF 0KB](1375)
摘要:
The southern coast of the Gulf of Maine in the United States is prone to flooding caused by nor’easters. A state-of-the-art fully-coupled model, the Simulating WAves Nearshore (SWAN) model with unstructured grids and the ADvanced CIRCulation (ADCIRC) model, was used to study the hydrodynamic response in the Gulf of Maine during the Patriot’s Day storm of 2007, a notable example of nor’easters in this area. The model predictions agree well with the observed tide-surges and waves during this storm event. Waves and circulation in the Gulf of Maine were analyzed. The Georges Bank plays an important role in dissipating wave energy through the bottom friction when waves propagate over the bank from offshore to the inner gulf due to its shallow bathymetry. Wave energy dissipation results in decreasing significant wave height (SWH) in the cross-bank direction and wave radiation stress gradient, which in turn induces changes in currents. While the tidal currents are dominant over the Georges Bank and in the Bay of Fundy, the residual currents generated by the meteorological forcing and waves are significant over the Georges Bank and in the coastal area and can reach 0.3 m/s and 0.2 m/s, respectively. In the vicinity of the coast, the longshore current generated by the surface wind stress and wave radiation stress acting parallel to the coastline is inversely proportional to the water depth and will eventually be limited by the bottom friction. The storm surge level reaches 0.8 m along the western periphery of the Gulf of Maine while the wave set-up due to radiation stress variation reaches 0.2 m. Therefore, it is significant to coastal flooding.
Using multi-satellite microwave remote sensing observations for retrieval of daily surface soil moisture across China
Ke Zhang, Li-jun Chao, Qing-qing Wang, Ying-chun Huang, Rong-hua Liu, Yang Hong, Yong Tu, Wei Qu, Jin-yin Ye
2019, 12(2): 85-97.   doi: 10.1016/j.wse.2019.06.001
[Abstract](506) [PDF 0KB](475)
摘要:
    The objective of this study was to retrieve daily composite soil moisture by jointly using brightness temperature observations from multiple operating satellites for near real-time application with better coverage and higher accuracy. Our approach was to first apply the single-channel brightness radiometric algorithm to estimate soil moisture from the respective brightness temperature observations of the SMAP, SMOS, AMSR2, FY3B, and FY3C satellites on the same day and then produce a daily composite dataset by averaging the individual satellite-retrieved soil moisture. We further evaluated our product, the official soil moisture products of the five satellites, and the ensemble mean (i.e., arithmetic mean) of the five official satellite soil moisture products against ground observations from two networks in Central Tibet and Anhui Province, China. The results show that our product outperforms the individual released products of the five satellites and their ensemble means in the two validation areas. The root mean square error (RMSE) values of our product were 0.06 and 0.09 m3/m3 in Central Tibet and Anhui Province, respectively. Relative to the ensemble mean of the five satellite products, our product improves the accuracy by 9.1% and 57.7% in Central Tibet and Anhui Province, respectively. This demonstrates that jointly using brightness temperature observations from multiple satellites to retrieve soil moisture not only improves the spatial coverage of daily observations but also produces better daily composite products.
Performance assessment of two-dimensional hydraulic models for generation of flood inundation maps in mountain river basins
Juan Pinos, Luis Timbe
2019, 12(1): 11-18.   doi: 10.1016/j.wse.2019.03.001
[Abstract](410) [PDF 0KB](405)
摘要:
Hydraulic models for the generation of ?ood inundation maps are not commonly applied in mountain river basins because of the dif?culty in modeling the hydraulic behavior and the complex topography. This paper presents a comparative analysis of the performance of four twodimensional hydraulic models (HEC-RAS 2D, Iber 2D, Flood Modeller 2D, and PCSWMM 2D) with respect to the generation of ?ood inundation maps. The study area covers a 5-km reach of the Santa Barbara River located in the Ecuadorian Andes, at 2330 masl, in Gualaceo. The model's performance was evaluated based on the water surface elevation and ?ood extent, in terms of the mean absolute difference and measure of ?t. The analysis revealed that, for a given case, Iber 2D has the best performance in simulating the water level and inundation for ?ood events with 20- and 50-year return periods, respectively, followed by Flood Modeller 2D, HEC-RAS 2D, and PCSWMM 2D in terms of their performance. Grid resolution, the way in which hydraulic structures are mimicked, the model code, and the default value of the parameters are considered the main sources of prediction uncertainty.
Biosorption of Ni(II) ions from aqueous solution using modified Aloe barbadensis Miller leaf powder
Shweta Gupta, S. K. Sharma, Arinjay Kumar
2019, 12(1): 27-36.   doi: 10.1016/j.wse.2019.04.003
[Abstract](443) [PDF 0KB](407)
摘要:
This study aimed to investigate the biosorption potential of Na2CO3-modified Aloe barbadensis Miller (Aloe vera) leaf (MABL) powder for removal of Ni(II) ions from a synthetic aqueous solution. Effects of various process parameters (pH, equilibrium time, and temperature) were investigated in order to optimize the biosorptive removal. The maximum biosorption capacity of MABL was observed to be 28.986 mg/g at a temperature of 303 K, a biosorbent dose of 0.6 g, a contact time of 90 min, and a pH value of 7. Different kinetic models (the pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models) were evaluated. The pseudo-second-order kinetic model was found to be the best fitted model in this study, with a coefficient of determination of R2 = 0.974. Five different isotherm models (the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Brunauer-Emmett-Teller (BET) models) were investigated to identify the best-suited isotherm model for the present system. Based on the minimum chi-square value (χ2 = 0.027) and the maximum coefficient of determination (R2 = 0.996), the Langmuir isotherm model was found to represent the system well, indicating the possibility of monolayer biosorption. The sticking probability (S*) was found to be 0.41, suggesting a physisorption mechanism for biosorption of Ni(II) on MABL. The biosorbent was characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), zeta potential, and BET surface area, in order to understand its morphological and functional characteristics.
Seismic responses of high concrete face rockfill dams: A case study
Sheng-shui Chen, Zhong-zhi Fu, Kuang-ming Wei, Hua-qiang Han
2016, 9(3): 195-204.   doi: 10.1016/j.wse.2016.09.002
[Abstract](1047) [PDF 0KB](1540)
摘要:
Seismic responses of the Zipingpu concrete face rockfill dam were analyzed using the finite element method. The dynamic behavior of rockfill materials was modeled with a viscoelastic model and an empirical permanent strain model. The relevant parameters were obtained either by back analysis using the field observations or by reference to parameters of similar rockfill materials. The acceleration responses of the dam, the distribution of earthquake-induced settlement, and the gap propagation under the concrete slabs caused by the settlement of the dam were analyzed and compared with site investigations or relevant studies. The mechanism of failure of horizontal construction joints was also analyzed based on numerical results and site observations. Numerical results show that the input accelerations were considerably amplified near the top of the dam, and the strong shaking resulted in considerable settlement of the rockfill materials, with a maximum value exceeding 90 cm at the crest. As a result of the settlement of rockfill materials, the third-stage concrete slabs were separated from the cushion layer. The rotation of the cantilever slabs about the contacting regions, under the combined action of gravity and seismic inertial forces, led to the failure of the construction joints and tensile cracks appeared above the construction joints. The effectiveness and limitations of the so-called equivalent linear method are also discussed.
Characterization of cobalt ferrite-supported activated carbon for removal of chromium and lead ions from tannery wastewater via adsorption equilibrium
Muibat Diekola Yahya, Kehinde Shola Obayomi, Mohammed Bello Abdulkadir, Yahaya Ahmed Iyaka, Adeola Grace Olugbenga
2020, 13(3): 202-213.   doi: 10.1016/j.wse.2020.09.007
[Abstract](273) [PDF 0KB](353)
摘要:
In this experiment, cobalt ferrite-supported activated carbon (CF-AC) was developed and characterized via the wet impregnation method for the removal of Cr and Pb(II) ions from tannery wastewater. Batch adsorption was carried out to evaluate the effect of experimental operating conditions (pH of solution, contact time, adsorbent dose, and temperature), and the removal efficiencies of Cr and Pb(II) ions by the developed adsorbents were calculated and recorded for all experimental conditions. These variables were estimated and reported as removal efficiencies of 98.2% for Cr and 96.4% for Pb(II) ions at the optimal conditions of 5, 0.8 g, 80 min, and 333 K for pH, adsorbent dose, contact time, and temperature, respectively. The equilibrium for the sorption of Cr and Pb(II) ions was studied using four widely used isotherm models (the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models). It was found that the Freundlich isotherm model fit better with the coefficient of determination (R2) of 0.948 4 and a small sum of square error of 0.000 6. The maximum adsorption capacities (Qm) of Pb(II) and Cr adsorbed onto CF-AC were determined to be 6.27 and 23.6 mg/g, respectively. The adsorption process conformed well to pseudo-second order kinetics as revealed by the high R2 values obtained for both metals. The thermodynamic parameters showed that adsorption of Cr and Pb(II) ions onto CF-AC was spontaneous, feasible, and endothermic under the studied conditions. The mean adsorption energy (E) values revealed that the adsorption mechanism of Cr and Pb(II) by CF-AC is physical in nature. The results of the study showed that adsorbent developed from CF-AC can be efficiently used as an environmentally friendly alternative adsorbent, for removal of Cr and Pb(II) ions in tannery wastewater.
Disinfection of dairy wastewater effluent through solar photocatalysis processes
Mojtaba Afsharnia, Mojtaba Kianmehr, Hamed Biglari, Abdollah Dargahi, Abdolreza Karimi
2018, 11(3): 214-219.   doi: 10.1016/j.wse.2018.10.001
[Abstract](588) [PDF 0KB](452)
摘要:
Due to the strict regulations and reuse policies that govern wastewater’s use as an irrigation water resource for agricultural purposes, especially in dry climates, optimization of the disinfection process is of the utmost importance. The effects of solar radiation along with Titanium dioxide (TiO2) nanoparticles applied to optimization of the photolysis and photocatalysis processes for inactivating heterotrophic bacteria were investigated. Temperature, pH, and dissolved oxygen fluctuations in the dairy wastewater effluent treated by activated sludge were examined. In addition, different dosages of TiO2 were tested in the solar photocatalysis (ph-C S) and concentrated solar photocatalysis (ph-C CS) processes. The results show that the disinfection efficiencies of the solar photolysis (ph-L S) and concentrated solar photolysis (ph-L CS) processes after 30 minutes were about 10.5% and 68.9%, respectively, and that the ph-C S and ph-C CS processes inactivated 41% and 97% of the heterotrophic bacteria after 30 minutes, respectively. The pH variation in these processes was negligible. Using the ph-L CS and ph-C CS processes, the synergistic effect between the optical and thermal inactivation caused complete disinfection after three hours. However, disinfection was faster in the ph-C CS process than in the ph-L CS process. Significant correlations were found between the disinfection efficiency and the variation of the dissolved oxygen concentration in the ph-C S and ph-C CS processes, while the correlations between the disinfection efficiency and temperature variation were not significant in the ph-L S and ph-C S processes. Moreover, the oxygen consumption rate was greatest (3.2 mg?L-1) in the ph-C CS process. Hence, it could be concluded that ph-C CS is an efficient photocatalysis process for disinfection of dairy wastewater effluent.
A simple formula for predicting settling velocity of sediment particles
Song Zhiyao, Wu Tingting, Xu Fumin, Li Ruijie
2008, 1(1): 37-43 .   doi: 10.3882/j.issn.1674-2370.2008.01.005
[Abstract](2772) [PDF 0KB](127)
Abstract:
Based on the general relationship described by Cheng between the drag coefficient and the Reynolds number of a particle, a new relationship between the Reynolds number and a dimensionless particle parameter is proposed. Using a trial-and-error procedure to minimize errors, the coefficients were determined and a formula was developed for predicting the settling velocity of natural sediment particles. This formula has higher prediction accuracy than other published formulas and it is applicable to all Reynolds numbers less than 2×105.
Calculation of passive earth pressure of cohesive soil  based on Culmann’s method
Hai-feng LU, Bao-yuan YUAN
2011, 4(1): 101-109.   doi: 10.3882/j.issn.1674-2370.2011.01.010
[Abstract](3576) [PDF 0KB](110)
Abstract:
Based on the sliding plane hypothesis of Coulumb earth pressure theory, a new method for calculation of the passive earth pressure of cohesive soil was constructed with Culmann’s graphical construction. The influences of the cohesive force, adhesive force, and the fill surface form were considered in this method. In order to obtain the passive earth pressure and sliding plane angle, a program based on the sliding surface assumption was developed with the VB.NET programming language. The calculated results from this method were basically the same as those from the Rankine theory and Coulumb theory formulas. This method is conceptually clear, and the corresponding formulas given in this paper are simple and convenient for application when the fill surface form is complex.   
Modeling atrazine transport in soil columns with HYDRUS-1D
John Leju CELESTINO LADU, Dan-rong ZHANG
2011, 4(3): 258-269.   doi: 10.3882/j.issn.1674-2370.2011.03.003
[Abstract](2997) [PDF 0KB](111)
Abstract:
Both physical and chemical processes affect the fate and transport of herbicides. It is useful to simulate these processes with computer programs to predict solute movement. Simulations were run with HYDRUS-1D to identify the sorption and degradation parameters of atrazine through calibration from the breakthrough curves (BTCs). Data from undisturbed and disturbed soil column experiments were compared and analyzed using the dual-porosity model. The study results show that the values of dispersivity are slightly lower in disturbed columns, suggesting that the more heterogeneous the structure is, the higher the dispersivity. Sorption parameters also show slight variability, which is attributed to the differences in soil properties, experimental conditions and methods, or other ecological factors. For both of the columns, the degradation rates were similar. Potassium bromide was used as a conservative non-reactive tracer to characterize the water movement in columns. Atrazine BTCs exhibited significant tailing and asymmetry, indicating non-equilibrium sorption during solute transport. The dual-porosity model was verified to best fit the BTCs of the column experiments. Greater or lesser concentration of atrazine spreading to the bottom of the columns indicated risk of groundwater contamination. Overall, HYDRUS-1D successfully simulated the atrazine transport in soil columns.
Analysis of dynamic wave model for flood routing in natural rivers
Reza BARATI, Sajjad RAHIMI, Gholam Hossein AKBARI
2012, 5(3): 243-258.   doi: 10.3882/j.issn.1674-2370.2012.03.001
[Abstract](3348) [PDF 0KB](125)
Abstract:
 Flooding is a common natural disaster that causes enormous economic, social, and human losses. Of various flood routing methods, the dynamic wave model is one of the best approaches for the prediction of the characteristics of floods during their propagations in natural rivers because all of the terms of the momentum equation are considered in the model. However, no significant research has been conducted on how the model sensitivity affects the accuracy of the downstream hydrograph. In this study, a comprehensive analysis of the input parameters of the dynamic wave model was performed through field applications in natural rivers and routing experiments in artificial channels using the graphical multi-parametric sensitivity analysis (GMPSA). The results indicate that the effects of input parameter errors on the output results are more significant in special situations, such as lower values of Manning’s roughness coefficient and/or a steeper bed slope on the characteristics of a design hydrograph, larger values of the skewness factor and/or time to peak on the channel characteristics, larger values of Manning’s roughness coefficient and/or the bed slope on the space step, and lower values of Manning’s roughness coefficient and/or a steeper bed slope on the time step and weighting factor.
Orifice plate cavitation mechanism and its influencing factors
Wan-zheng AI, Tian-ming DING
2010, 3(3): 321-330.   doi: 10.3882/j.issn.1674-2370.2010.03.008
[Abstract](3448) [PDF 0KB](100)
Abstract:
The orifice plate energy dissipater is an economic and highly efficient dissipater. However, there is a risk of cavitaion around the orifice plate flow. In order to provide references for engineering practice, we examined the cavitation mechanism around the orifice plate and its influencing factors by utilizing mathematical analysis methods to analyze the flow conditions around the orifice plate in view of gas bubble dynamics. Through the research presented in this paper, the following can be observed: The critical radius and the critical pressure of the gas nucleus in orifice plate flow increase with its initial state parameter ; the development speed of bubbles stabilizes at a certain value after experiencing a peak value and a small valley value; and the orifice plate cavitation is closely related to the distribution of the gas nucleus in flow. For computing the orifice plate cavitation number, we ought to take into account the effects of pressure fluctuation. The development time of the gas nucleus from the initial radius to the critical radius is about 10-7-10-5 s; therefore, the gas nucleus has sufficient time to develop into bubbles in the negative half-cycle of flow fluctuation. The orifice critical cavitation number is closely related to the orifice plate size, and especially closely related with the ratio of the orifice plate radius to the tunnel radius. The approximate formula for the critical cavitation number of the square orifice plate that only considers the main influencing factor was obtained by model experiments.
Modified theoretical stage-discharge relation for circular sharp-crested weirs
Rasool GHOBADIAN, Ensiyeh MERATIFASHI
2012, 5(1): 26-33.   doi: 10.3882/j.issn.1674-2370.2012.01.003
[Abstract](3042) [PDF 0KB](122)
Abstract:
A circular sharp-crested weir is a circular control section used for measuring flow in open channels, reservoirs, and tanks. As flow measuring devices in open channels, these weirs are placed perpendicular to the sides and bottoms of straight-approach channels. Considering the complex patterns of flow passing over circular sharp-crested weirs, an equation having experimental correlation coefficients was used to extract a stage-discharge relation for weirs. Assuming the occurrence of critical flow over the weir crest, a theoretical stage-discharge relation was obtained in this study by solving two extracted non-linear equations. To study the precision of the theoretical stage-discharge relation, 58 experiments were performed on six circular weirs with different diameters and crest heights in a 30 cm-wide flume. The results show that, for each stage above the weirs, the theoretically calculated discharge is less than the measured discharge, and this difference increases with the stage. Finally, the theoretical stage-discharge relation was modified by exerting a correction coefficient which is a function of the ratio of the upstream flow depth to the weir crest height. The results show that the modified stage-discharge relation is in good agreement with the measured results.
  • Top Download
  • Top Click
Advanced Search
Volume 15,Issue 3, Aug. 2022

Editor-in-ChiefChao Wang

Edited byEditorial Board of Water Science and Engineering

Distributed byEditorial Office of Water Science and Engineering