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1.
【Objective】In order to analyze the water quality distribution characteristics of each water quality monitoring section of Qingshui River in Ningxia, provide a basis for water quality assessment, based on three water quality section monitoring data on Qingshui River in Ningxia from 2014 to 2016. 【Method】Using the method of Principal Component Analysis to select the evaluate data and choose representative water quality indicators to issue Comprehensive Water Quality Identification Index evaluation and combined with 3 weighting methods to do further comparative analysis.【Result】The comprehensive water quality identification index show that the Ershilipu section water quality evaluation results for class II water and remained stable. The Sanying section evaluation results meet the class III water in 2014 and 2015 years, the evaluation results meet class IV water in 2016, It shows that the water quality of this section has a trend of decrease. The Quanyanshan section evaluation results for the class II water and reduced year by year, the water quality has become the trend of further good. 【Conclusion】The three section water quality evaluation using different weighting methods reached the water function zoning requirements, there were some defects in the Standard Multiple Method and the Entropy Weight Method, and the Variation Coefficient Method was more suitable than the other two weighting methods. © 2019 Office of Journal of Irrigation and Drainage, Farmland Irrigation Research Institute, Chinese Academy of Agricultural Sciences. All rights reserved.  相似文献   

2.
In order to study the influence of gas-liquid two phase flow to a centrifugal pump perfor mance and internal flow patterns, the steady three dimensional flow with different gas volume fractions is simulated by applying the Reynolds average N-S equation and mixture gas-liquid two phase flow model, and the compressibility of gas is taken into consideration in the simulation. Then we emphatically analyzed the centrifugal pump characteristic and the gas distribution law in different gas volume fractions. The computational results show that gas volume fraction has a certain influence on the performance of the centrifugal pump, and the efficiency and head of the pump are on the decline with the increase of it. Static pressure in the impeller increases in the radial direction, but the pressure gradient in the flow direction is different under the different gas volume fractions. The gas volume is distributed mainly in the ipsilateral direction of impeller back shroud in the flow channel of the volute. On the suction side of the blade inlet there is an obvious low pressure area, which causes bubbles agglutination and higher gas volume fraction. With the gas entering passage flow, gas volume fraction in the suction decreases and the pressure surface rises gradually. Higher gas volume fraction causes air blocking phenomenon in the flow passage and the discharge capacity reduces. The increase of gas volume makes the turbulent motion within the impeller more and more intense, which leads to more and more energy loss.  相似文献   

3.
[Objective]Soil moisture plays an important role in ecosystem function and hydrological processes. This paper investigated the hieratical distribution of soil moisture at different scales over a maize field.[Method] The studied site was a 50 m×50 m plot at the Experiment Station of Chinese Academy of Agricultural Sciences in Xinxiang, Henan province. We measured soil moisture in 0~100 cm soil from 36 locations at 10 m×10 m and 2 m×2 m scale, respectively.[Result]Geostatistical analysis revealed that the soil moisture was normally distributed and its confidence level at every scale was higher than that of logarithmic normal distribution. The value of the confidence level decreased as the sampling scale increased, and the difference between average soil moisture content at fine scale and moderate scale was smaller than the difference between moderate scale and large scale. In general, the confidence interval, standard deviation and coefficient of variation of the soil moisture increased with sampling scale. At large scale, the semi-variance function increased with lag distance, while at small and moderate scale, the variation function appeared to be independent of the lag distance. To achieve the same confidence level and accuracy in estimating soil moisture, the number of samples needed to be taken from the field increased with sampling scale. We also found that in estimating soil moisture, the number of samples needed to be taken depended on the required accuracy more than on the confidence level.[Conclusion]The probabilistic distribution and statistical characteristics of soil moisture in the field was scale-dependent. In estimating soil moisture, the number of sampled taken from the field needs to consider the scales to which the measured data will be applied. © The Author(s) 2019.  相似文献   

4.
The carbon fiber reinforced composite is a new type of composite material with an excellent property in strength and elastic modulus and has found extensive applications in aerospace, energy, automotive industry and so on. However, this composite has a strict requirement on processing techniques, for example, brittle damage or delamination often exists in conventional processing techniques. Abrasive water jet machining technology is a new type of green machining technique with distinct advantages such as high-energy and thermal distortion free. The use of abrasive water jet technique to process carbon fiber composite materials has become a popular trend since it can significantly improve the processing accuracy and surface quality of carbon fiber composite materials. However, there are too many parameters that affect the quality of an abrasive water jet machining. At present, few studies are carried out on the parameter optimization of such a machining process. This leads to the unstable quality of surface processing. In this paper, orthogonal design of experiment and regression analysis were employed to establish the empirical model between cutting surface roughness and machining process parameters. Then a verified model was used to optimize the machining process parameters for abrasive water jet cutting carbon fiber.  相似文献   

5.
【Objective】Soil moisture plays a critical role in many hydrological and ecological processes and understanding its spatiotemporal changes is imperative to ecosystem management and irrigation design. This paper presents and tests a method to estimate soil moisture distribution using satellite technologies.【Method】We took Guangli Irrigation District at Jiaozuo in Henan Province as our study area. The Landsat-8 and MODIS imageries from the area were used to retrieve soil moisture with the apparent thermal inertia and vegetation water supply index, respectively. Using the abundance of vegetation and soil moisture decomposed by the spectral mixture analysis as weighting factors, we retrieved the soil moisture distribution in the area using the two methods.【Result】The correlation coefficient between the measured soil moisture and the retrieved using the vegetation water supply index method and the apparent thermal inertia method was 0.47 and 0.51 respectively. We found that combining the two methods could improve the correlation coefficient between the measured and retrieved soil moisture to 0.73. 【Conclusion】Our results showed that the proposed method is reliable and can adequately estimate soil moisture in irrigation district grown with a diverse of crops. © 2019 Authors. All rights reserved.  相似文献   

6.
A finite volume, multiphase solver in the framework of OpenFOAM is used to calculate the flow field of the cavitating flow over the Clark-Y hydrofoil. This solver uses Transport Based Equation Model (TEM) to solve the liquid volume fraction, and utilizes volume of fluid (VOF) technique to predict the interface between liquid and vapor phases. The simulation is designed to study the cavitation shedding and different fluid characteristics in the cloud cavitation regime when adopting two different Large Eddy Simulation (LES) models, namely, one equation eddy viscosity (oneEqEddy) model and Smagorinsky model. It is shown that these two models can be used to study the cavitation shedding dynamics and predict the velocity profiles.  相似文献   

7.
【Objective】The aim of this study was to investigate the responses of cherry tomato to waterlogging at seedling stage, and to provide reference for waterlogging resistance cultivation of off-season cherry tomato in the tropical area.【Method】Five different varieties of cherry tomatoes were used as materials in pot culture experiment, with soil waterlogging treatment and normal moisture treatment as the control (CK). The morphological characteristics indexes of shoot and root and chlorophyll fluorescence parameters in leaves of cherry tomato were measured in different days of waterlogging. And the effects of waterlogging on morphological characteristics and chlorophyll fluorescence parameters at seedling stage of cherry tomato were analyzed.【Result】Results showed that waterlogging significantly decreased the plant height, stem diameter, leaf area, leaf number and SPAD value of cherry tomato, but had no significant effect on leaf thickness. The root diameter of cherry tomato had no significant affects, but the root volume was significantly increased in HongFei 6 and TaiwanZanMei during waterlogging. Compared with CK, the root length and root surface area of HongFei 6 increased significantly, while that of QianXi decreased significantly during waterlogging. Additionally, waterlogging increased the initial fluorescence (Fo) and non-photochemical quenching coefficient (NPQ), and significantly decreased the maximum photochemical efficiency (Fv/Fm), apparent electron transfer rate (ETR) and photochemical quenching coefficient (qP) of cherry tomato leaves, besides HongFei 6.【Conclusion】The results above indicated that during waterlogging the growth and development and chlorophyll fluorescence in leaves of cherry tomato were seriously affected, but there had different effects among five different varieties . Among five varieties of cherry tomatoes, the strongest waterlogging resistance was HongFei 6, while the weakest waterlogging resistance was QianXi. © 2019 Journal of Irrigation and Drainage. All rights reserved.  相似文献   

8.
【Objective】In order to obtain the irrigation infiltration recharge coefficient in the lower reaches of Aksu river and improve the numerical simulation accuracy of groundwater in the study area,the influencing factors of the irrigation infiltration recharge coefficient in this area were analyzed. 【Method】In this paper,field sampling and indoor irrigation experiments were carried out by selecting representative points under different irrigation schemes,vadose zone thickness and soil structure in the lower Aksu area,and numerical simulation of vadose zone flow was carried out in combination with Hydrus-1d. Hydrus-1d model was used to calculate irrigation inflow under this soil structure by changing irrigation schemes and vadose zone thickness. Change of seepage recharge coefficient. On the basis of the calculation results of the model,the relationship between irrigation schedule,aeration zone thickness and irrigation infiltration recharge coefficient is analyzed firstly,and then the main factors affecting irrigation infiltration recharge coefficient in soil structure are analyzed with the method of model calculation and mathematical statistics. 【Result】The results showed that the irrigation infiltration recharge coefficient ranged from 0.320 to 0.474 under drip irrigation and from 0.408 to 0.561 under border irrigation. The irrigation infiltration recharge coefficient varied under different irrigation schemes,while the irrigation infiltration recharge coefficient decreased with the increase of aeration zone thickness. The main factors affecting irrigation infiltration recharge are soil permeability coefficient,soil bulk density and initial soil water content. 【Conclusion】According to indoor experiment combined with numerical model to calculate the irrigation infiltration coefficient under different irrigation system range, it is concluded that the influence factors of irrigation infiltration coefficient of irrigation system, the thickness of the vadose zone and reflects soil permeability coefficient of soil structure, soil quality and soil initial moisture content, volume for the downstream area irrigation infiltration coefficient selection in arid areas and provides the theory basis for further research. © 2019 Journal of Irrigation and Drainage. All rights reserved.  相似文献   

9.
In the industrial process of producing the strong phosphoric acid (SPA), clarification of the solution is essential to the ultimate product. However, the large viscosity of sediment and the induced interface interaction result in difficulties when the SPA is clarified. CFD numerical methodology is applied to simulate internal flow field and performance of the low speed scraper based on Mixture solid liquid two phase flow model. Sediment deposition is generated by loading solid particles at the bottom of clarifying vessel. The moving mesh and RNG k-ε model are used to simulate the rotational turbulent flow in clarifying tank. Variables studied, amongst others, are the scraper rotation speed and the mounting height, which can affect the solid suspension height. Features of flow field and solid volume fraction distribution in computational domain are presented and analyzed. The numerical reports of the scraper torque and velocities of inlet and outlet filed are obtained. It seems the torque value of rotational axis and particle suspending height augment with an increasing rotating speed. Meanwhile, a high revolving speed is good for the deposition discharge. The particle fraction distribution in meridional surface and horizontal surface at fixed rotation speed are analyzed to determine the corresponding optimal installation height. The simulating results reflect the flow field is marginally stirred by the scraper and proper working parameters are obtained, in which case the comprehensive properties of the scraper and the clarifying tank are superior.  相似文献   

10.
Numerical studies on transient heat transfer characteristics of air-array-jet impingement with a small jet-to-plate distance and a large temperature difference between nozzles and plate were presented.The dimensionless jet-to-plate distance(H/D)was 0.2,and non-dimensional nozzle-to-nozzle spacing(S/D)was 3,4,5 and 6,respectively.It is found that the quenching time is shortened at a constant total mass flow at air jet inlet m·(m·=218.21 kg/h),and the heat transfer uniformity is deterio-rated as S/D increases.However,the adding reversed-flow nozzles can shorten the quenching time of the glass plate considerably with a modest change in the heat transfer uniformity.The results at variable m·are the same as those at a fixed m·.Furthermore,the parity and arrangement of nozzles are also discussed,It is found that an odd number of nozzles is more beneficial for transient heat transfer.Based on these results,an appropriate proposal for ultra-thin glass tempering process is presented.  相似文献   

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