Water Resources
Abstract:
Surf-zone hydrodynamics forced by oblique wave shoaling and breaking on beach slopes were investigated. The results showed that in wavebasin experiments with incident angles in the range of 15°-30°, wave breaking was initiated at a breaker coefficient of around 0.67, which was significantly less than that predicted from empirical relations based on normally incident waves for a given beach slope and deep-water wave steepness. The measurements also showed that subsequent saturated breaking occurred at a breaker coefficient of around 0.47 that was independent of beach slope in the range of 1:10 to 1:100. This result is likely applicable to both oblique and normally incident waves. It is shown that the measured wave heights and longshore velocity profiles in wave-basin studies can be reasonably well predicted by theory with proper adjustments to the process parameters. Best-match formulations were identified for quantifying bottom friction, eddy viscosity, and energy loss due to surface rollers.
Abstract:
Mining activities interfere with the natural groundwater chemical environment, which may lead to hydrogeochemical changes of aquifers and mine water inrush disasters. This study analyzed the hydrochemical compositions of 80 water samples in three aquifers and developed a water source identification model to explore the control factors and potential hydraulic connection of groundwater chemistry in a coal mine. The results showed that the hydrochemical types of the three aquifers were different. The main hydrochemical compositions of the loose-layer, coalbearing, and limestone aquifers were HCO3·Cl-Na, SO4·HCO3-Na, and SO4-Na·Ca, respectively. The correlation, Unmix, and factor analyses showed that the hydrochemical composition of groundwater was controlled by the dissolution of soluble minerals (such as calcite, dolomite, gypsum, and halite) and the weathering of silicate minerals. The factor score plot combined with Q-mode cluster analysis demonstrated no remarkable hydraulic connection among the three aquifers in the study area. The water source identification model effectively identified the source of inrush water. Moreover, the mixing ratio model rationally quantified the contributions of the three aquifers to inrush water.
Abstract:
When choosing sites for monitoring of soil moisture for hydrological purposes, a suitable process that considers the factors influencing soil moisture level should be followed. In this study, two multi-criteria decision-making (MCDM) methods, the multi-influencing factor (MIF) method and the analytical hierarchy process (AHP) method, were used to identify the optimal soil moisture monitoring (SMM) sites in the Dry Creek Catchment in South Australia. The most representative areas for nine SMM sites were obtained using the MIF method, considering the factors of rainfall, soil type, land use, catchment slope, elevation, and upslope accumulated area (UAA). The AHP method was used to select the optimal sites using the site-specific criteria. 30.3% of the catchment area in the Australian Water Resources Assessment Landscape (AWRA-L) Grid_DC2 can be considered acceptable as representative area with the MIF method. Four potential sites were evaluated for each AWRA-L grid using the relative weights of the site-specific criteria with the AHP method. The Grid_DC2 required two sites that had the highest overall weight chosen with the AHP analysis. The procedure was repeated for the remaining four AWRA-L grids within the study area to select the required SMM sites.
Aquatic Environment
Abstract:
Fe3O4 magnetic xerogel composites were prepared by polycondensation of resorcinol (R)-formaldehyde reaction via a sol-gel process in an aqueous solution through varying the molar ratio of Fe3O4 nanoparticles (MNPs), catalyst (C), and water (W) content. MNPs were obtained by co-precipitation (MC), oxidation of iron salts (MO), or solvothermal synthesis (MS). Both MNPs and magnetic xerogels were examined regarding the performance of arsenic and fluoride removal in a batch system. The MC-based MNPs had higher adsorption capacities for both fluoride (202.9 mg/g) and arsenic (3.2 mg/g) than other MNPs in optimum conditions. The X-ray diffraction, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy confirmed that Fe was composed into the polymeric matrix of magnetic xerogels that contained 0.59%-4.42% of Fe with a molar ratio of MNPs (M) to R between 0.01 and 0.10. With low R/C and optimum M/R ratios, an increase in the surface area of magnetic xerogels affected the fluoride and arsenic adsorption capacities. The magnetic xerogel composites with the MCbased MNPs prepared at a fixed R/C ratio (100) and at different R/W (0.05-0.06) and M/R (0.07-0.10) ratios had a high arsenic removal efficiency of 100% at an As(V) concentration of 0.1 mg/L and pH of 3.0. The maximum adsorption capacities of magnetic xerogels were approximately five times higher than those of the xerogels without MNP composites. Therefore, Fe3O4 nanoparticles enhanced the adsorption of arsenate and fluoride. The variations of alkaline catalyst and water content significantly affected the resulting properties of textural and surface chemistry of magnetic xerogel composites.
Abstract:
Antibiotics and antibiotic resistance genes (ARGs) pose health risks in aquatic environments because of their persistence and mobility. River networks can provide a perfect opportunity for exploring the occurrence and enrichment of ARGs and antibiotics in freshwater environments. On this basis, the abundances of four types of antibiotics (sulfonamides, quinolones, tetracyclines, and macrolides) and 13 ARGs (sulⅠ, sulⅡ, tetA, tetB, tetO, tetW, qnrA, qnrS, qnrD, ermB, ermF, ermC, and ereA) were measured in the river networks of the west bank of the Wangyu River in China. The spatial distribution and temporal variation of these antibiotics and ARGs were characterized, and their controlling factors were analyzed. All four types of antibiotics were detected with high frequencies between 41% and 100%. Quinolone antibiotics exhibited the highest average concentration (286.53 ng/L). The concentrations of quinolones, tetracyclines, and macrolides were significantly higher in the winter than in the summer, whereas the concentration of sulfonamides was higher in wet periods than in dry periods. Of the 13 ARGs, sulI was the most abundant (1.28 ×105 copies per milliliter), followed by sulII and tetO (5.41×104 and 4.45×104 copies per milliliter, respectively). The canonical correspondence analysis showed that environmental factors, including dissolved oxygen, water temperature, total nitrogen, pH, and total phosphorus, had significant effects on the abundance of ARGs. sulⅠ, sulⅡ, tetA, and tetB were significantly correlated with 16S ribosomal RNA sequences, indicating that the bacterioplankton community might affect the distribution of ARGs. The correlation heat map analysis showed that the spread of ARGs was influenced by specific bacterial groups, such as Acidobacteria and Cyanobacteria, indicating that these bacterioplankton may be the hosts of environmental ARGs.
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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](1416) [PDF 9190KB](1899)
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](456) [PDF 388KB](533)
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](1412) [PDF 8704KB](2782)
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.
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](443) [PDF 2519KB](422)
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.
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](526) [PDF 10109KB](491)
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.
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](1405) [PDF 8393KB](1414)
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.
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](458) [PDF 1653KB](424)
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.
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](300) [PDF 2667KB](370)
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.
Modeling river water quality parameters using modified adaptive neuro fuzzy inference system
Armin Azad, Hojat Karami, Saeed Farzin, Sayed-Farhad Mousavi, Ozgur Kisi
2019, 12(1): 45-54.   doi: 10.1016/j.wse.2018.11.001
[Abstract](357) [PDF 1344KB](404)
摘要:
Water quality is always one of the most important factors in human health. Artificial intelligence models are respected methods for modeling
water quality. The evolutionary algorithm (EA) is a new technique for improving the performance of artificial intelligence models such as the
adaptive neuro fuzzy inference system (ANFIS) and artificial neural networks (ANN). Attempts have been made to make the models more
suitable and accurate with the replacement of other training methods that do not suffer from some shortcomings, including a tendency to being
trapped in local optima or voluminous computations. This study investigated the applicability of ANFIS with particle swarm optimization (PSO)
and ant colony optimization for continuous domains (ACOR) in estimating water quality parameters at three stations along the Zayandehrood
River, in Iran. The ANFIS-PSO and ANFIS-ACOR methods were also compared with the classic ANFIS method, which uses least squares and
gradient descent as training algorithms. The estimated water quality parameters in this study were electrical conductivity (EC), total dissolved
solids (TDS), the sodium adsorption ratio (SAR), carbonate hardness (CH), and total hardness (TH). Correlation analysis was performed using
SPSS software to determine the optimal inputs to the models. The analysis showed that ANFIS-PSO was the better model compared with
ANFIS-ACOR. It is noteworthy that EA models can improve ANFIS' performance at all three stations for different water quality parameters.
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](649) [PDF 912KB](491)
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](2802) [PDF 124KB](133)
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](3633) [PDF 429KB](130)
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](3019) [PDF 434KB](114)
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](3386) [PDF 423KB](137)
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](3497) [PDF 283KB](114)
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](3078) [PDF 313KB](133)
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.
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Volume 15,Issue 4, Dec. 2022

Editor-in-ChiefChao Wang

Edited byEditorial Board of Water Science and Engineering

Distributed byEditorial Office of Water Science and Engineering