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Numerical analysis of a projecting wall type oscillating water column(PW-OWC)wave energy converter in regular waves

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Journal of Hydrodynamics 2024年第3期36卷 479-491页

作者： lei tan Ruiyuan Chang Tomoki Ikoma Department of Oceanic Architecture and Engineering College of Science and TechnologyNihon UniversityChibaJapan

Oscillating water column(OWC)based wave energy absorption devices are classic which have been widely used for harnessing ocean wave *** paper presents a numerical study on a projecting wall(PW)type OWC wave energy converter in regular *** computational fluid dynamics(CFD)modelling of a stationary floating PW-OWC model in a three-dimensional wave flume is achieved by the software *** analyses are carried out based on CFD simulations and the linear potential flow solutions with modifications to account for turbine-induced *** present numerical solutions are validated against our previous experimental *** is found that both the CFD and modified linear potential flow predictions are in reasonably good agreements with the experimental data in the first order results of OWC and air pressure *** the nonlinear responses are included in the result,the modified linear potential flow solution is found to slightly under-estimate the wave energy conversion performance at long *** the airflows above and below the chamber orifice,the CFD results suggest that they are almost unidirectional,oscillating in not only the base frequency but also subharmonic and ultraharmonic *** evolution of the OWC responses during an entire period and the phase analysis based on CFD simulations are *** phase results provide the crucial evidence to the reasonability of the physics-based modification of the potential flow model in modelling of *** present results and analysis are expected to be beneficial to the understanding on the physical mechanism of OWCs and the design of phase control strategies.

关键词： Computational fluid dynamics(CFD)simulation hydrodynamic analysis oscillating water column(OWC)damping orifice airflow phase difference

Effects of Meridional Flow Passage Shape on Hydraulic Performance of Mixed-flow Pump Impellers

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Chinese Journal of Mechanical Engineering 2013年第3期26卷 469-475页

作者： BING Hao CAO Shuliang tan lei ZHU Baoshan State Key Laboratory of Hydroscience and Engineering Tsinghua University State Key Laboratory of Tribology Tsinghua University

During the process of designing the mixed-flow pump impeller, the meridional flow passage shape directly affects the obtained meridional flow field, which then has an influence on the three-dimensional impeller shape. However, the meridional flow passage shape is too complicated to be described by a simple formula for now. Therefore, reasonable parameter selection for the meridional flow passage is essential to the investigation. In order to explore the effects of the meridional flow passage shape on the impeller design and the hydraulic performance of the mixed-flow pump, the hub and shroud radius ratio (HSRR) of impeller and the outlet diffusion angle (ODA) of outlet zone are selected as the meridional flow passage parameters. 25 mixed-flow pump impellers, with specific speed of 496 under the design condition, are designed with various parameter combinations. Among these impellers, one with HSRR of 1.94 and ODA of 90° is selected to carry out the model test and the obtained experimental results are used to verify accuracies of the head and the hydraulic efficiency predicted by numerical simulation. Based on SIMPLE algorithm and standard k-ε two-equation turbulence model, the three-dimensional steady incompressible Reynolds averaged Navier-Stokes equations are solved and the effects of different parameters on hydraulic performance of mixed-flow pump impellers are analyzed. The analysis results demonstrate that there are optimal values of HSRR and ODA available, so the hydraulic performance and the internal flow of mixed-flow pumps can be improved by selecting appropriate values for the meridional flow passage parameters. The research on these two parameters, HSRR and ODA, has further illustrated influences of the meridional flow passage shape on the hydraulic performance of the mixed-flow pump, and is beneficial to improving the design of the mixed-flow pump impeller.

关键词： mixed-flow pump meridional flow passage numerical simulation hydraulic performance

A dynamic solution for predicting resonant frequency of piston mode fluid oscillation in moonpools/narrow gaps

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Journal of Hydrodynamics 2020年第1期32卷 54-69页

作者： lei tan Lin Lu Guo-qiang tang Liang Cheng State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China International Joint Laboratory on Offshore Oil and Gas Engineering Dalian University of TechnologyDalian 116024China School of Engineering The University of Western AustraliaPerthAustralia

The objective of this study is to develop a simple tool for predicting the resonant frequency of the piston mode wave oscillation in a moonpool or a narrow gap between twin floating *** on the dynamic analysis and the domain-decomposition,a linear harmonic oscillator model for the fluid oscillation in a confined space is formulated,which immediately leads to an explicit dynamic solution for the resonant *** the model,it is assumed that the water depth is equal to or greater than a critical value dependent on the ratio of the draft to the breadth of the floating *** predicted resonant frequencies are compared with the numerical results of the linear potential model and the viscous fluid model,the semi-analytical potential solutions and the experimental *** agreements are observed for a wide range of geometric parameters of the moonpool and the narrow gap of either sharp or round edge *** present dynamic method is also applied to predict the resonant frequency of the piston mode oscillation in the gap between a floating body and a vertical wall with a reasonable success.

关键词： Resonant frequency piston mode resonance moonpool narrow gap dynamic model

Demonstration of the approximation of eliminating atomic excited populations in an atom-cavity system

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Chinese Physics B 2012年第2期21卷 272-277页

作者： Zhang Yu-Qing Huang Gang tan lei Institute of Theoretical Physics Lanzhou UniversityLanzhou 730070China Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Lanzhou UniversityLanzhou 730000China

Using the master equation approach to a V-type three-level atom inside a high-finesse single-mode cavity in the strong coupling condition, we demonstrate the approximation of eliminating populations of atomic excited states, which is widely used in the field of the atom cavity systems [Hechenblaikner G, Gangl M, Horak P and Ritsch H 1998 Phys. Rev. A 58 3030]; Liu L W, tan T and Xu Y 2008 J. Mod. Opt. 56 968; Cho J, Angelakis D G and Bose S 2008 Phys. Rev. A 78 062338. This is reflected in the deviation of the population 5, of which the value is 10^-3 - 10^-2. We further find the deviation of the dipole force and demonstrate that the deviation of atomic population will not notably affect the dipole force of the atom in the strong coupling condition. A relevant experimental case is also presented.

关键词： V-type three-level atom high finesse optical cavity dipole force strong coupling condition

Prediction method of impeller performance and analysis of loss mechanism for mixed-flow pump

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Science China(Technological Sciences) 2012年第7期55卷 1988-1998页

作者： BING Hao tan lei CAO ShuLiang LU Li State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China Hydraulic Machinery Department China Institute of Water Resources and Hydropower ResearchBeijing 100038China

A loss model for the mixed-flow pump impellers was developed by summarizing a variety of loss calculation formulas *** internal flow field of the impeller was obtained by employing the iterative calculation for S 1 and S 2 stream surfaces to solve the continuity and motion equations of *** on the calculation method of the flow field and the loss model,it is achieved to predict the impeller performance of the mixed-flow pump and the performance curves of a mixed-flow pump model with adjustable *** with the test data,the loss model of the mixed-flow pump based on the iterative calculation can predict the impeller performance quickly and accurately,which has a high value on the engineering *** on the test verification,curves of various kinds of losses varied for the flow rate were analyzed under different blade *** addition,the mechanisms of various kinds of losses inside the mixed-flow pump impeller were discussed in-depth.

关键词： mixed-flow pump loss modeling iterative calculation performance prediction loss mechanism

Influence of axial distance on pre-whirl regulation by the inlet guide vanes for a centrifugal pump

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Science China(Technological Sciences) 2012年第4期55卷 1037-1043页

作者： tan lei CAO ShuLiang WANG YuMing ZHU BaoShan State Key Laboratory ofTribology Tsinghua UniversityBeijing 100084China State Key Laboratory of Hydrosc-ience and Engineering Tsinghua UniversityBeijing 100084China

The valuation of the hydraulic performance of a centrifugal pump with pre-whirl regulation of the inlet guide vanes was studied experimentally by varying the pre-whirl angle from -60° to 60° with distances between the inlet guide vanes and the impeller inlet of 280 mm, 380 mm and 460 mm. The efficiency-flow curves and the characteristic curves were obtained for the pump for various operation conditions. The experiment results demonstrated that the pre-whirl regulation widened the high efficiency zone and improved the hydraulic performance for off-design conditions with the proper pre-whirl angle. The axial distance between the inlet guide vanes and the impeller inlet influenced the pre-whirl regulation effect of the inlet guide vanes with the best pre-whirl regulation effect obtained for an axial distance of 380 mm. These results showed that an appropriate axial distance between the inlet guide vanes and the impeller inlet can improve the fluid flow at the impeller entrance with pre-whirl regulation for centrifugal pumps.

关键词： centrifugal pump inlet guide vanes axial distance pre-whirl regulation

Improvement in the Performance of the Polylactic Acid Composites by Using Deep Eutectic Solvent Treated Pulp Fiber

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Journal of Renewable Materials 2021年第11期9卷 1897-1911页

作者： lei tan Liangxian Liu Chaodong Liu Weihong Wang Key Laboratory of Bio-Based Material Science and Technology(Ministry of Education) Material Science and Engineering CollegeNortheast Forestry UniversityHarbin150040China

As the most favorable alternative to petroleum-based polymers,polylactic acid(PLA)which is the most promising degradable polymer has attracted increasing ***,the addition of cellulose to improve its strength often results in a reduction in its *** this work,microscale cellulose is first prepared from pulp fibers by using a deep eutectic solvent,and then is used as the reinforcement of PLA.A microcrystalline cellulose(MCC)/PLA sheet with uniform texture is obtained by the solution mixing,melt blending,hot-pressing and cold-pressing *** effects of MCC on the crystallization,thermal stability and mechanical properties of the PLA matrix were *** the addition of 1%cellulose fiber,the tensile strength of MCC/PLA composite sheet increased by 27%,and the elongation at break did not shown an evident *** strength enhancement mechanism was elucidated using scanning electron microscopy,differential scanning calorimetry,and dynamic thermomechanical *** energy dissipation during the deformation process and the compatibility of AMCC and rougher surface of MCC play important role in the strength ***,UV spectroscopy showed that the composite material absorbed some ultraviolet *** results show that the combined use of a deep eutectic solvent and solution mixing is an effective approach for improving the strength of PLA while maintaining its toughness.

关键词： Polylactic acid microcrystalline cellulose deep eutectic solvent mechanical properties

Influence of Blade Wrap Angle on Centrifugal Pump Performance by Numerical and Experimental Study

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Chinese Journal of Mechanical Engineering 2014年第1期27卷 171-177页

作者： tan lei ZHU Baoshan CAO Shuliang BING Hao WANG Yuming State Key Laboratory of Hydroscience and Engineering Tsinghua University State Key Laboratory of Tribology Tsinghua University

The existing research on improving the hydraulic performance of centrifugal pumps mainly focuses on the design method and the parameter optimization. The traditional design method for centrifugal impellers relies more on experience of engineers that typically only satisfies the continuity equation of the fluid. In this study, on the basis of the direct and inverse iteration design method which simultaneously solves the continuity and motion equations of the fluid and shapes the blade geometry by controlling the wrap angle, three centrifugal pump impellers are designed by altering blade wrap angles while keeping other parameters constant. The three-dimensional flow fields in three centrifugal pumps are numerically simulated, and the simulation results illustrate that the blade with larger wrap angle has more powerful control ability on the flow pattern in impeller. The three pumps have nearly the same pressure distributions at the small flow rate, but the pressure gradient increase in the pump with the largest wrap angle is smoother than the other two pumps at the design and large flow rates. The pump head and efficiency are also influenced by the blade wrap angle. The highest head and efficiency are also observed for the largest angle. An experiment rig is designed and built to test the performance of the pump with the largest wrap angle. The test results show that the wide space of its efficiency area and the stability of its operation ensure the excellent performance of the design method and verify the numerical analysis. The analysis on influence of the blade wrap angle for centrifugal pump performance in this paper can be beneficial to the optimization design of the centrifugal pump.

关键词： blade wrap angle centrifugal pump performance numerical simulation experiment

Comparison study on the annealing behaviors of dispersion strengthened copper alloys with different nanoparticles

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Rare Metals 2007年第5期26卷 456-462页

作者： GUO Mingxing WANG Mingpu lei Ruoshan tan Wang JIN Peng School of Materials Science and Engineering Central South University Changsha 410083 China

The hardness measurement,optical microscopy （OM）,and transmission electron microscopy （TEM） microstructure observation on the annealing behaviors of Cu-Al2O3 （2.25 vol.% and 0.54 vol.% Al2O3） and Cu-0.52vol.%Nb alloys were carried out. The results show that with the increase of annealing temperature,the hardness of Cu-Al2O3 alloys decreases slowly. No change of the fiber structure formed by cold rolling in the Cu-2.25vol.%Al2O3 alloy is observed even after annealing at 900℃and the higher dislocation density can still be observed by TEM. Less combination of fiber formed by cold rolling and subgrains are observed in the Cu-0.54vol.%Al2O3 alloy annealed at 900℃. With the increase of annealing temperature,the hardness of the Cu-0.52vol.%Nb alloy exhibits a general decreasing trend,and its falling rate is higher than that of the Cu-Al2O3 alloys,indicating that its ability of resistance to softening at elevated temperature is weaker than that of the Cu-Al2O3 alloys. However,when annealed at a temperature of 300-400℃,probably owing to the precipitation strengthening of niobium,the hardness of the Cu-0.52vol.%Nb alloy arises slightly. The fibers formed by cold rolling be-come un-clear and un-straight and have less combination,and considerably more subgrains are observed by TEM.

关键词： high-temperature properties hardness measurement Cu-Al2O3 alloy Cu-Nb alloy dispersion strengthening cold working annealing