Water Science and Engineering - 开云电竞网

Hydrological Daily Rainfall-runoff Simulating with BTOPMC model and Comparison with Xin’anjiang model

Hong-jun BAO, Li-li WANG, Zhi-jia LI, Lin-na ZHAO, Guo-ping ZHANG — 2010-06-30

Hong-jun BAO, Li-li WANG, Zhi-jia LI, Lin-na ZHAO, Guo-ping ZHANG A grid-based distributed hydrological model BTOPMC (Block-wise use of TOPMODEL) is applied for hydrological daily rainfall-runoff simulation, which was developed from the original TOPMODEL. The runoff is explicitly calculated on a grid by grid basis and flow concentration method is Muskingum-Cunge in BTOPMC model. In order to testify the model’s application, BTOPMC model and Xin’anjiang model were applied in humid watersheds and semi-humid and semi-arid watersheds in China. The models parameters were optimized by SCE-UA method. Results show that both models are good at simulating the daily hydrograph in humid watersheds and BTOPMC model perform poor in semi-humid and semi-arid watersheds. The excess infiltration mechanism should be incorporated into BTOPMC model for broadening the model’s application region. Water Science and Engineering. 2010 3(2): 121-131.

Rainwater harvesting to alleviate water scarcity in dry conditions: A case study in Faria Catchment, Palestine

Sameer SHADEED, Jens Lange — 2010-06-30

Sameer SHADEED, Jens Lange In arid and semi-arid regions, the availability of adequate water of appropriate quality has become a limiting factor for development. This paper aims to evaluate the potential for rainwater harvesting in the arid to semi-arid Faria Catchment, in the West Bank, Palestine. Under current conditions, the supply-demand gap is increasing due to the increasing water demands of a growing population with hydrologically limited and uncertain supplies. By 2015, the gap is estimated to reach 4.5 × 106 m3. This study used the process-oriented and physically-based TRAIN-ZIN model to evaluate two different rainwater harvesting techniques during two rainfall events. The analysis shows that there is a theoretical potential for harvesting an additional 4 × 106 m3 of surface water over the entire catchment. Thus, it is essential to manage the potential available surface water supplies in the catchment to save water for dry periods when the supply-demand gap is comparatively high. Then a valuable contribution to bridging the supply-demand gap can be made Water Science and Engineering. 2010 3(2): 132-143.

System dynamics model of Suzhou water resources carrying capacity and its application

Li CHENG — 2010-06-30

Li CHENG A model of Suzhou water resources carrying capacity (WRCC) was set up using the method of system dynamics (SD). In the model, three different water resources utilization programs were adopted: (1) continuity of existing water utilization, (2) water conservation/saving, and (3) water exploitation. The dynamic variation of the Suzhou WRCC was simulated with the supply-decided principle for the time period of 2001 to 2030, and the results were characterized based on socio-economic factors. The corresponding Suzhou WRCC values for several target years were calculated by the model. Based on these results, proper ways to improve the Suzhou WRCC are proposed. The model also produced an optimized plan, which can provide a scientific basis for the sustainable utilization of Suzhou water resources and for the coordinated development of the society, economy, and water resources. Water Science and Engineering. 2010 3(2): 144-155.

An Improved PSO Algorithm Based on Chaos Theory and Used in Design Flood Hydrograph

Si-fang DONG, Zeng-chuan DONG, Jun-jian MA, Kang-ning CHEN — 2010-06-30

Si-fang DONG, Zeng-chuan DONG, Jun-jian MA, Kang-ning CHEN Abstract: The deficiency of basic Particle Swarm Optimization（PSO） lie in the ubiquitous prematurity and the incapability in seeking the global optimal solution while optimizing complex high dimensional functions. To over come such deficiencies, COSPSO algorithm was established by introducing the chaos optimization mechanism and global particle stagnation-disturbed strategy. In the improved algorithm, the chaotic movement was adopted in particle’s initial movement locus to replace the former stochastic movement and chaos factor was used to lead particle’s flying. When the global particle stayed in, disturbing strategy was used to keep the particle from stagnation. Five benchmark optimizations were introduced to test COSPSO and proved COSPSO could remarkably improve the efficiency in optimizing complex functions. Finally, the application of the COSPSO in calculating the design flood hydrograph gave a good result. Water Science and Engineering. 2010 3(2): 156-165.

Storm surge variational assimilation model

Shi-li HUANG, Jian XU, De-guan WANG, Dong-yan LU — 2010-06-30

Shi-li HUANG, Jian XU, De-guan WANG, Dong-yan LU To eliminate errors caused by uncertainty of parameters and further improve capability of storm surge forecasting, the variational data assimilation method is applied to the storm surge model based on unstructured grid with high spatial resolution. The method can effectively improve the forecasting accuracy of storm surge induced by typhoon through controlling wind drag force coefficient parameter. The model is first theoretically validated with synthetic data. Then, the real storm surge process induced by the TC 0515 typhoon is forecasted by the variational data assimilation model, and results show the feasibility of practical application. Water Science and Engineering. 2010 3(2): 166-173.

Analytical study on water hammer pressure in pressurized conduits with a throttled surge chamber for slow closure

Yong-liang ZHANG, Ming-fei MIAO, Ji-ming MA — 2010-06-30

Yong-liang ZHANG, Ming-fei MIAO, Ji-ming MA This paper presents an analytical investigation of water hammer in a hydraulic pressurized pipe system with a throttled surge chamber located at the junction between a tunnel and a penstock, and a valve positioned at the downstream end of the penstock. Analytical formulas of maximum water hammer pressures at the downstream end of the tunnel and the valve were derived for a system subjected to linear and slow valve closure. The analytical results were then compared with numerical ones obtained using the method of characteristics. There is agreement between them. The formulas can be applied to estimating water hammer pressure at the valve and transmission of water hammer pressure through the surge chamber at the junction for a hydraulic pipe system with a surge chamber. Water Science and Engineering. 2010 3(2): 174-189.

Theoretical and numerical study of hydraulic characteristics of orifice energy dissipator

Ning HE, Zhen-xing ZHAO — 2010-06-30

Ning HE, Zhen-xing ZHAO Different factors affecting the efficiency of the orifice energy dissipator were investigated based on a series of theoretical analyses and numerical simulations. The main factors investigated by dimension analysis were identified, including the Reynolds number (Re), the ratio of the orifice diameter to the inner diameter of the pipe ( ), and the ratio of distances between orifices to the inner diameter of the pipe ( ). Then, numerical simulations were conducted with a two-equation turbulence model. The calculation results show the following: Hydraulic characteristics change dramatically as flow passes through the orifice, with abruptly increasing velocity and turbulent energy, and decreasing pressure. The turbulent energy appears to be low in the middle and high near the pipe wall. For the energy dissipation setup with only one orifice, when Re is smaller than 105, the orifice energy dissipation coefficient K increases rapidly with the increase of Re. When Re is larger than 105, K gradually stabilizes. As increases, K and the length of the recirculation region L1 show similar variation patterns, which inversely vary with . The function curves can be approximated as straight lines. For the energy dissipation model with two orifices, because of different incoming flows at different orifices, the energy dissipation coefficient of the second orifice (K2) is smaller than that of the first. If is less than 5, the K value of the model, depending on the variation of K2, increases with the spacing between two orifices L , and an orifice cannot fulfill its energy dissipation function. If is greater than 5, K2 tends to be steady; thus, the K value of the model gradually stabilizes. Then, the flow fully develops, and L has almost no impact on the value of K. Water Science and Engineering. 2010 3(2): 190-199.

Experimental Investigation of Tunnel Discharge Ability by Using Drag Reduction Techniques

Ying-kui WANG, Chun-bo JIANG — 2010-06-30

Ying-kui WANG, Chun-bo JIANG The experiments in an open flume model and in the spillway tunnel models were carried out by using drag reduction technique. The drag reduction experiments in open channel model adopted two techniques: polymer addition and coating. The drag reduction effect of polyacrylamide (PAM) solution and the dimethyl silicone oil coating were studied by the flume model experiments, and the results were satisfied. Then the experiments were carried out in the model of a Hydropower station, which is the second largest dam in China. In order to reduce the resistance, the spillway tunnel models were coated inside with the dimethyl silicone oil. It is the first time that applying the drag reduction technique in the large hydraulic model. The experimental results show that the coating technique can effectively increase the ability of flood discharge. The outlet velocity and the jet trajectory distance were also increased, which is beneficial to the energy dissipation of the spillway tunnel. Water Science and Engineering. 2010 3(2): 200-207.

Numerical simulation of flow past circular duct

Ze-gao YIN, Xian-wei Cao, Hong-da SHI, Jian MA — 2010-06-30

Ze-gao YIN, Xian-wei Cao, Hong-da SHI, Jian MA On the basis of Fluent software, Renormalization Group (RNG)k-ε turbulent model and Volume of Fluid (VOF) method are employed to simulate the flow past circular duct to obtain and analyze the hydraulic parameters. According to various upper and bottom gap-ratios, the force on duct is calculated. Firstly, when bottom gap-ratio is 0, drag force coefficient, lift force coefficient and composite force reach the maximum respectively and azimuth reaches the minimum. Secondly, with the increase of bottom gap-ratio from 0 to 1, drag force coefficient and composite force decrease sharply, lift force coefficient decreases a little, but azimuth increases dramatically. Thirdly, with the continuous increase of bottom gap-ratio from 1, drag force coefficient, lift force coefficient, composite force and azimuth vary little. So, bottom gap-ratio is the key factor influencing the force on circular duct. When bottom gap-ratio is less than 1, upper gap-ratio has the remarkable influence on the circular duct force. When bottom gap-ratio is greater than 1, the varation of upper gap-ratio has a little influence on the circular duct force. Water Science and Engineering. 2010 3(2): 208-216.

Roughness coefficient and its uncertainty in a gravel-bed river

Ji-Sung KIM, Chan-Joo LEE, Won KIM, Yong-Jeon KIM — 2010-06-30

Ji-Sung KIM, Chan-Joo LEE, Won KIM, Yong-Jeon KIM Manning's roughness coefficient is estimated for a gravel-bed river reach by field measurement on water level and discharge and applicability of various methods used for estimation of roughness coefficient is evaluated. Results show that roughness coefficient tends to decrease with increasing discharge and relative depth, and over a certain range it appears to become constant. Comparison of roughness coefficients by field measurement with ones estimated by several previous methods shows that though they give approximate roughness coefficient values for relatively large discharge, there seem to be rather high uncertainty due to difference of resultant values. For this, uncertainties related to roughness coefficient are analyzed in terms of change in computed variables. In average, a +20% uncertainty in roughness coefficient causes a 7% increase in water level and an 8% decrease in velocity, but they may be about a 15% increase and as much decrease for a certain cross-section in the study reach. Finally, validity of roughness coefficient estimation based on field measurement is examined. A 10% error in discharge measurement may lead to over 10% uncertainty in roughness coefficient estimation, but corresponding uncertainty in computed water depth and velocity is reduced to approximately 5%. Conversely, necessity for roughness coefficient estimation by field measurement may be confirmed. Water Science and Engineering. 2010 3(2): 217-232.

Tensile reliability analysis for gravity dam foundation surface based on FEM and response surface method

Tong-chun LI, Dan-dan LI, Zhi-qiang WANG — 2010-06-30

Tong-chun LI, Dan-dan LI, Zhi-qiang WANG In the paper, the limit state equation of tensile reliability of foundation base of gravity dam is established. The possible crack length is set as action effect and the allowance crack length is set as resistance in this limit state. The nonlinear FEM is applied to obtain the crack length of foundation base of gravity dam, and linear response surface method based on the orthogonal test design method is used to calculate the reliability,which offered an reasonable and simple analysis method to calculate the reliability on serviceability limit state .The LongTan RCC gravity dam is taken as an example.The orthogonal test, which includes 9 factors and 2 levels, is adopted . The tensile reliability is calculated and design point are also given. The analyses results showed that this method is reasonable. Water Science and Engineering. 2010 3(2): 233-240.