China Renewable Energy Engineering Institute
China Renewable Energy Engineering Institute
Gao R.,Xi'an University of Architecture and Technology |
Chen S.,Xi'an University of Architecture and Technology |
Li A.,Xi'an University of Architecture and Technology |
Yang Z.,China Renewable Energy Engineering Institute |
Cong B.,Tongtai Fire and Security Co.
Building Services Engineering Research and Technology | Year: 2017
Owing to the limited installation space and duct size, coupled fittings are common in the duct systems of buildings. The coupling effect leads to changes in drag and fan energy consumption. This study investigates duct drag and flow field characteristics under coupling conditions. Experiments and numerical simulations with the Reynolds stress model are conducted. Flow field changes, flow field deformation, and drag changes in the duct are analyzed. Regardless of the coupling form, the velocity near the inner arc is fast, whereas that near the outer arc is slow. Under three different coupling connection conditions (S-shaped, L-shaped, and U-shaped), the outlet velocity gradient of the U-shaped coupling connection is the least obvious. After the fluid flows through the bend, a significant centerline velocity reduction can be observed, even greater than that in the bend. The lowest centerline velocity lies within the range of 2.5 D to 4.5 D after the bend. Coupling connection has an insignificant effect on upstream duct resistance. The resistance of single bend is less than that of the downstream bend for the coupled bend and greater than that of the upstream bend under coupling conditions. Practical application: Coupling effect is common in practical application of ventilation engineering. This effect leads to the change of fluid resistance loss of ducts and pipes. However, few researchers focus on this effect. This study finds that regardless of the coupling form, the velocity near the inner arc is fast, whereas that near the outer arc is slow. It means the guide vane should be set near inner arc. L-shaped coupling connection has the largest downstream piping resistance. The resistance of the downstream piping under S-shaped coupling is the least, thus L-shaped coupling connection should be avoided as far as possible in practical application. © The Chartered Institution of Building Services Engineers 2016.
Guo W.,North China University of Water Conservancy and Electric Power |
Guo W.,China Institute of Water Resources and Hydropower Research |
Fu Y.,China Institute of Water Resources and Hydropower Research |
Ruan B.,China Renewable Energy Engineering Institute |
And 2 more authors.
Ecological Indicators | Year: 2014
More and more nitrogen and phosphorus chemical fertilizers are applied in the upstream of the Yongding River Basin. With the aid of convertibility between emergy and value, the calculated ESI (Environmental Sustainability Index) of basin agricultural production is 0.1056, indicating that local agriculture is seriously unsustainable. According to the different combining types of nitrate and ammonium salts with soil particles, soil nitrogen losses under the influence of rainfall-runoff are quantitatively evaluated from the perspective of the nitrogen cycle. By virtue of the content of dissolved and particulate phosphorus in soil, the calculation process for soil phosphorus loss is modeled according to the field runoff volume. The total nitrogen and total phosphorus losses from soil are 96 kg hm-2 and 9 kg hm-2, respectively. The calculation result of nitrogen and phosphorus losses in the basin is certainly reasonable. Finally, the research emphasis of calculation method for reducing basin agricultural non-point source pollution is represented from management level. © 2013 Published by Elsevier Ltd.
Niu X.,Tsinghua University |
Yu J.,China Renewable Energy Engineering Institute
Procedia Engineering | Year: 2015
As a flexible Lagrangian particle method, smoothed particle hydrodynamics (SPH) can easily capture large interface deformation, breaking, merging and splashing, which is quite suitable for the simulation of water surface waves. The classic weakly compressible smoothed particle hydrodynamics (WCSPH) algorithm for incompressible fluid flow usually needs small time steps to ensure numerical stability, which makes it computational time consuming. The major reason is that the pressure is linked with the density deviation which should be zero everywhere in incompressible fluid flows. Generally, the equation of state for a weakly compressible fluid is adopted to simulate incompressible fluid. To enforce the incompressibility, the stiffness of fluid is set to be large enough to keep the density deviation less than an allowable error. That will lead to a problem that a tiny error of computed density will cause a large pressure error and further numerical instability. In order to obtain rational pressure distribution and good computational efficiency as well, a new algorithm is proposed considering that flow field is globally incompressible from the view of spatial averaged flow field and weakly compressible locally due to the computational error from the view of particles. The basic conception of the proposed modified SPH is to split the pressure into a global part and local fluctuating part. The global part of pressure or the spatial averaged pressure on the resolution of background mesh is obtained by solving the pressure Poisson equation based on the velocity divergence free condition. The local fluctuating pressure is related to the local particle density variation by solving the local pressure Poisson equation, which is applied to maintain particles' spacing in relative equilibrium. Based on this idea, formulas for the spatial averaged pressure and local fluctuating pressure are derived. The spatial averaged pressure is used as a primary estimation of the pressure gradient force and then the local fluctuating pressure is added as a correction of local density deviation. The proposed algorithm is verified by simulating the classic dam broken problem and then applied to simulate water wave breaking. A comparison of the particle configurations with previous studies at different times is shown. Good agreement between the present results and the previous results can be found. A discussion on computational efficiency is also carried out. The result shows that the proposed algorithm has better stability and can greatly reduce the computational time cost. © 2015 The Authors. Published by Elsevier Ltd.
Wang J.-T.,Tsinghua University |
Jin A.-Y.,Tsinghua University |
Du X.-L.,Beijing University of Technology |
Wu M.-X.,Tsinghua University |
Wu M.-X.,China Renewable Energy Engineering Institute
Soil Dynamics and Earthquake Engineering | Year: 2016
In current engineering practice, artificial earthquake accelerograms are widely used in the seismic design of new dams. This study aims to investigate the seismic response and damage sensitivity of arch dams to artificial ground motions. A total of 32 accelerograms are artificially synthesized based on the design acceleration response spectrum. The nonlinear dynamic response of the Dagangshan Dam, an arch dam in Southwest China, to these artificial accelerograms is investigated. Dynamic response, including displacement and joint opening, and damage distribution are statistically analyzed. Results show that the seismic response and damage to a dam may significantly scatter for various accelerograms, even if the artificial accelerograms have the same response spectra, peak ground accelerations, velocities, and displacements. © 2016 Elsevier Ltd.
Wang L.,Xi'an University of Technology |
Chen Z.,China Institute of Water Resources and Hydropower Research |
Wang N.,China Institute of Water Resources and Hydropower Research |
Sun P.,China Institute of Water Resources and Hydropower Research |
And 3 more authors.
Engineering Geology | Year: 2016
Evaluation of breach flood of landslide or artificial dams is usually performed by combining the hydraulic modeling of the breach flow and geotechnical analysis of the breach channel stability. This paper is a continuation of the previous work, which mainly focused on the hydraulic aspects of a dam breach flood. Efforts have been made to improve the related slope stability analysis approach that traditionally adopts a simple wedge failure mode. The improvements includes a vertical cut at the slope toe due to soil erosion, an approach to determine the critical slip surface, the effective and total stress methods dealing with different dam materials, and a procedure to model the stepped failures of the breach bank due to continuous toe cutting. Using VBA programming, an Excel spreadsheet entitled DBS-IWHR has been developed to perform the stability analysis. This spreadsheet has been incorporated into another spreadsheet entitled DB-IWHR for the calculation of the flood hydrograph. The developed model has been tested by back analysis of the Yigong landslide dam breached at the Tibetan Plateau in China in 2000 with a flood peak of 94,013 m3/s. The calculated results of the final breach base level and the peak discharge are in good agreement with the field data. Further, the results are shown to be insensitive to the variations in the geotechnical parameters used in the model. © 2016 Elsevier B.V.
Weng B.,China Institute of Water Resources and Hydropower Research |
Zhang P.,China Renewable Energy Engineering Institute |
Li S.,Hebei University of Engineering
Arabian Journal of Geosciences | Year: 2015
With the increasing impact of climate change and anthropogenic activities, drought happens in more areas with higher frequency. In this paper, we calculate the return period and the drought risk in China based on the monthly PDSI, the Palmer Drought Severity Index, data over 188 stations from 1901 to 2010. We use the theory of runs to identify the drought duration and severity. We adopt the kernel density estimation to obtain the marginal distribution function, and the Gumbel Copula function to obtain the joint distribution function. The results show that the return period of the joint distribution for the drought duration and severity can be regarded as the extreme condition of the return period of the marginal distribution for the single factor such as the drought duration or drought severity. Under the same drought severity, the return period of the joint distribution is increasing with the prolonging of the drought duration, and it approaches to the return period of the marginal distribution of the drought severity. Under the extreme drought situation, Haihe River Basin, Huaihe River Basin, Songliao River basin, and rivers in the northwest China have a higher drought risk in future 50 years. The drought risk value in China is increasing with the prolonging of predicting time. © 2015 Saudi Society for Geosciences
Chen A.,China Institute of Water Resources and Hydropower Research |
Sui X.,China Institute of Water Resources and Hydropower Research |
Wang D.,China Institute of Water Resources and Hydropower Research |
Liao W.,Beijing Institute of Water |
And 2 more authors.
Ecological Engineering | Year: 2016
Wetlands are important habitats on biodiversity protection. In this study, the relationship between wetland and avifauna changes in the Yellow River Delta Wetland was studied. Remote sensing and geographic information system provided an advanced platform for the research. After the avifauna survey was performed from 2012 to 2013, the birds' variation and driving factors were analyzed. The results showed that the flow into the wetland increased continuously from 2000, and the increased of artificial wetland prevented the wetland degradation, although at the same time the total wetland area decreased. Medium grassland, tidal flat and pond are the three main landscapes which are beneficial for the habitation of birds. The migrating numbers of red-crowned crane increased significantly from 2005, and the overwintering numbers increased from 2009. The study results show that the key land use types for protecting endangered species of birds are medium grassland, tidal flat and pond landscapes. Wetland changes are sensitive to the birds and significantly affected by the flow. We suggest that the artificial wetland project should enhance the three land use type area to ensure the wetland restoration. © 2015 Elsevier B.V.
Shi G.H.,University of Chinese Academy of Sciences |
Shi G.H.,China Renewable Energy Engineering Institute |
Shi G.H.,Yangtze River Scientific Research Institute
Science China Technological Sciences | Year: 2015
Contacts between two general blocks are the fundamental problem for discontinuous analysis. There are different contact points in different block positions, and there may have infinite contact point pairs in the same block position. In this paper, a new concept of an entrance block for solving the contacts between two general blocks is introduced. The boundary of an entrance block is a contact cover system. Contact covers may consist of contact vectors, edges, angles or polygons. Each contact cover defines a contact point and all closed-contact points define the movements, rotations and deformations of all blocks as in real cases. Given a reference point, the concept of entrance block simplifies the contact computation in the following ways. (1) The shortest distance between two blocks can be computed by the shortest distance between the reference point and the surface of the entrance block. (2) As the reference point outside the entrance block moves onto the surface of entrance block, the first entrance takes place. This first entrance point on the entrance block surface defines the contact points and related contact locations. (3) If the reference point is already inside the entrance block, it will exit the entrance block along the shortest path. The corresponding shortest exit point on the entrance block surface defines the contact points and related contact locations. All blocks and angles here are defined by inequality equations. Algebraic operations on blocks and angles are described here. Since the blocks and angles are point sets with infinite points, the geometric computations are difficult, and therefore the geometric computations are performed by related algebraic operations. © 2015, Science China Press and Springer-Verlag Berlin Heidelberg.
Wang Y.,Basin Water |
Wang Y.,China Institute of Water Resources and Hydropower Research |
Ren A.,China Renewable Energy Engineering Institute |
Wang Y.,Chinese Academy of Geological Sciences |
And 3 more authors.
Canadian Geotechnical Journal | Year: 2016
This paper presents the observed findings and laboratory test results of an anchor exhumed from Manwan Hydropower Station, China, that was installed 20 years ago. The prestressed cables are 25.6 m long with a working load of 1000 kN. It consists of eight strands, and each strand consists of seven wires. The anchor was installed using the “single protection” technique (i.e., the steel strands without greased sheath and were backfilled directly with cement mortar). The anchor was unearthed by excavating a 1.5 m × 1.7 m tunnel. Visual inspection shows that the steel strands in the free and fixed lengths are basically stainless except for a few places where the grout failed to cover the anchor completely, thereby allowing direct contact of the strands with air. The magnitude of rebound of the tendon during the advancement of the tunnel face was simultaneously measured indicating a gradual release of bonding force, which was up to 62% of the prestressed load. This shows that the existence of the bonding force is provided by the bonding between the strand and the grout, while this bonding does not exist in the “double protection” system. The results of the mechanical test confirm that the tensile strengths in all the 33 steel wires exceed the requirement as specified by a current Chinese Standard. The concentrations of various chemicals also satisfy the requirements as specified by the China State Bureau of Quality Technical Supervision. The results of the X-ray diffraction test show that the stains taken from the surface of the strand are composed of FeO and FeOOH, both being oxide products of iron. This shows that exposure of the material to air is an important condition to initiate corrosion. By following the ASTM International G1-03 test procedure, the average corrosion rate is found to be between 3 × 10−4 and 6 × 10−4 mm/year. This investigation generally supports the use of unprotected steel strands in rock anchor. © 2016, National Research Council of Canada. All rights reserved.
Zhang X.,China Renewable Energy Engineering Institute |
Chen S.-H.,Hubei Engineering University
Yantu Lixue/Rock and Soil Mechanics | Year: 2015
Prestressed anchor technics is a primary measure to reinforce rock masses in geotechnical engineering. It plays an important role in mobilizing the self-bearing capacity of the rock masses and improving the strength and self-stability of the rock masses. Because of the complexity and diversity of anchoring engineering, anchoring mechanism has not been well understood, and the design theory and related computational method are insufficient for engineering applications. Two important problems remain to be addressed, which are related to the existing analytical solutions of the stress transfer along the anchored section of the prestressed anchor cable. Firstly the stress variation along the anchored section of prestressed anchor cable has not been well characterized,and secondly the stress singularity at the endpoint has not been considered in the existing analytical solutions. Through the analysis of applicability and limitation of the previous analytical solutions, it is shown that the stress distribution along the anchored section can be divided into three stages: elastic stage, plastic stage and failure stage. The stress distributions are different in different stages. Within this context, an expression is developed for calculating the transferred load in the above three stages. The shear stress and axial force distributions along the anchored section are determined. For a practical case, the critical anchorage length is determined by the proposed equation, and the result is compared to those of other methods, showing the validity and capability of the proposed procedure. ©, 2015, Academia Sinica. All right reserved.