The semidiagnostic and prognostic models are used to compute the current in the Taiwan Strait with wind and hydrographic data collected during August, 1984 and September 1 ~ 6, 1988. This calculation can be divided in...The semidiagnostic and prognostic models are used to compute the current in the Taiwan Strait with wind and hydrographic data collected during August, 1984 and September 1 ~ 6, 1988. This calculation can be divided into two stages, i. e. (1 ) the adjustable stage; (2) prognostic calculation. The computed result shows tha the density and velocity fields etc. have been adjusted when t = 2. 5 d, namely the solution of semidignostic calculation is obtained,and the quasi-steady state solution have been reached after about 40 d. Comparing the results of diagncotic calculation with those of semidiagnortic and prognostic calculations indicates that they agree qualitatively. For example, they all have the following common features: (1 ) there is a persistent northward fiow with a volume transport of 0. 8 × 10 6 m3/s through the Taiwan Strait in summer; (2 ) the current near the western coas of Taiwan is stronger than that in other regiona; (3) the upweiling occurs near the Fujian coast and so on. However, there is a quantitative difference between them as follows. For example, the horizotal velocity near the westem cot of Taiwan and the upwelling speed near the Fujian aret both are underestimaed in the diagnestic calculation, because the data used in which is smoothed, and they both are intensified in the solutions of semidiagnostic and prognostic calculations. For example, the maximum velocity near the western coast of Taiwan at t = 0 d (diagnostic), 2. 5 d (semidiagnostic) and 300 d (prognostic) is 59.1, 62. 1 and 62. 0 cm/s, respectively. From the above comparison we see it is quite necessary that a semidiagnostic model be used to compute the currents when the data have been smoothed.展开更多
On the basis of a three-dimensional weakly nonliear theory of Lagrangian residual current in the Baroclinic shallow seas, a diagnostic numerical calculation of wind-driven, thermohaline and tide-induced Lagrangian res...On the basis of a three-dimensional weakly nonliear theory of Lagrangian residual current in the Baroclinic shallow seas, a diagnostic numerical calculation of wind-driven, thermohaline and tide-induced Lagrangian residual current in the Bohai Sea is made. The model involves the Richardson number in the eddy viscosity coefficient, wind, thcrmolialine and tidal effects in the focing terms. The runoff of the Huanghe River and a part of the Huanghai Warm Water coming from the Huanghai Sea through the Bohai Sea Strait is also considered. The velocity-splitting method is adopted. The wind-driven circu lation, thermohaline circulation and the tide-induced Lagrangian residual circulation are also obtained individually and analysed. The dynamics of the three main eddies in the Lagrangian mean circulation is discussed. Finally, the numerical result is partly verified with the observed data.展开更多
An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, clo...An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.展开更多
Slope excavation is one of the most crucial steps in the construction of a hydraulic project. Excavation project quality assessment and excavated volume calculation are critical in construction management. The positio...Slope excavation is one of the most crucial steps in the construction of a hydraulic project. Excavation project quality assessment and excavated volume calculation are critical in construction management. The positioning of excavation projects using traditional instruments is inefficient and may cause error. To improve the efficiency and precision of calculation and assessment, three-dimensional laser scanning technology was used for slope excavation quality assessment. An efficient data acquisition, processing, and management workflow was presented in this study. Based on the quality control indices, including the average gradient, slope toe elevation, and overbreak and underbreak,cross-sectional quality assessment and holistic quality assessment methods were proposed to assess the slope excavation quality with laserscanned data. An algorithm was also presented to calculate the excavated volume with laser-scanned data. A field application and a laboratory experiment were carried out to verify the feasibility of these methods for excavation quality assessment and excavated volume calculation. The results show that the quality assessment indices can be obtained rapidly and accurately with design parameters and scanned data, and the results of holistic quality assessment are consistent with those of cross-sectional quality assessment. In addition, the time consumption in excavation quality assessment with the laser scanning technology can be reduced by 70%e90%, as compared with the traditional method. The excavated volume calculated with the scanned data only slightly differs from measured data, demonstrating the applicability of the excavated volume calculation method presented in this study.展开更多
In the finite element method,the numerical simulation of three-dimensional crack propagation is relatively rare,and it is often realized by commercial programs.In addition to the geometric complexity,the determination...In the finite element method,the numerical simulation of three-dimensional crack propagation is relatively rare,and it is often realized by commercial programs.In addition to the geometric complexity,the determination of the cracking direction constitutes a great challenge.In most cases,the local stress state provides the fundamental criterion to judge the presence of cracks and the direction of crack propagation.However,in the case of three-dimensional analysis,the coordination relationship between grid elements due to occurrence of cracks becomes a difficult problem for this method.In this paper,based on the extended finite element method,the stress-related function field is introduced into the calculation domain,and then the boundary value problem of the function is solved.Subsequently,the envelope surface of all propagation directions can be obtained at one time.At last,the possible surface can be selected as the direction of crack development.Based on the aforementioned procedure,such method greatly reduces the programming complexity of tracking the crack propagation.As a suitable method for simulating tension-induced failure,it can simulate multiple cracks simultaneously.展开更多
Three-dimensional(3D) single-layer microcoils have always been a key element for electromagnetic systems;but they lack an easy and accurate method to calculate the inductance value for their complex 3D micro-structure...Three-dimensional(3D) single-layer microcoils have always been a key element for electromagnetic systems;but they lack an easy and accurate method to calculate the inductance value for their complex 3D micro-structures. This paper employed a curve-fitting process to obtain the associated equation for the inductance value and geometric parameters based on the simulation results. The correction factors regarding helical pitch and wire diameter were reviewed,which are used for compensation in the Nagaoka formula. The simulation process numerically simulated the performance of the 3D microcoils using a FEM electro-magnetic-coupled analysis method. Comparison of the simulated inductance value and the Nagaoka formula was undertaken,which shows that the helical pitch and wire diameter contribute a main role in the calculation error. The derived formula was expressed in a concise form to precisely calculate the inductance value of 3D microsolenoids with single-layer coils.展开更多
A three-dimensional numerical tsunami model is developed to analyze the nonlinear behavior of flow around obstacles with the Marker and Cell （MAC） method based on the Navier-Stokes equations. Tnrough a comparison wi...A three-dimensional numerical tsunami model is developed to analyze the nonlinear behavior of flow around obstacles with the Marker and Cell （MAC） method based on the Navier-Stokes equations. Tnrough a comparison with experimental data for the cases of dam break and solitary wave propagation, verification of the three-dimensional numerical model is given. Numerical experiment is performed for the analysis of the nonlinear behavior of flow around obstacles and compared with experimental data. The velocity and pressure around obstacles are presented with sufficient accuracy for tstmami propagation passing through an obstacle.展开更多
In this paper, the theory of constructing optimal dynamical systems based on weighted residual presented by Wu & Sha is applied to three-dimensional Navier-Stokes equations, and the optimal dynamical system modeli...In this paper, the theory of constructing optimal dynamical systems based on weighted residual presented by Wu & Sha is applied to three-dimensional Navier-Stokes equations, and the optimal dynamical system modeling equations are derived. Then the multiscale global optimization method based on coarse graining analysis is presented, by which a set of approximate global optimal bases is directly obtained from Navier-Stokes equations and the construction of optimal dynamical systems is realized. The optimal bases show good properties, such as showing the physical properties of complex flows and the turbulent vortex structures, being intrinsic to real physical problem and dynamical systems, and having scaling symmetry in mathematics, etc.. In conclusion, using fewer terms of optimal bases will approach the exact solutions of Navier-Stokes equations, and the dynamical systems based on them show the most optimal behavior.展开更多
With the development and progress of science and technology,road and bridge design has experienced rapid development,from the initial manual drawing design to the popularity of Computer-Aided Design(CAD),and then to t...With the development and progress of science and technology,road and bridge design has experienced rapid development,from the initial manual drawing design to the popularity of Computer-Aided Design(CAD),and then to today’s digital software design era.Early designers relied on hand-drawn paper design forms which was time-consuming and error-prone.Digital support for road and bridge design not only saves the design time but the design quality has also achieved a qualitative leap.This paper engages in the application of digital technology in road and bridge design,to provide technical reference for China’s road and bridge engineering design units,to promote the popularity of Civil3D and other advanced design software in the field of engineering design and development,ultimately contributing to the sustainable development of China’s road and bridge engineering.展开更多
The studies concerning the wake transition regime of the flow around a circular cylinder have drawn much attention in these years. Many experiments have been conducted for this problem but no accurate three-dimensiona...The studies concerning the wake transition regime of the flow around a circular cylinder have drawn much attention in these years. Many experiments have been conducted for this problem but no accurate three-dimensional numerical simulations have hitherto been made. In this paper, a parallel procedure was developed to solve the three-dimensional Navier-Stokes equations on an SGI Origin3900 machine. Two different parallel strategies on this application were analyzed about their efficiency. It is found that the critical Reynolds number is 195, and the wake flow below this Reynolds number is purely two-dimensional one, while the Reynolds number goes beyond this critical point, the wake flow becomes unstable under three-dimensional small disturbances. The transition regime involves two modes of small-scale three-dimensional instability (modes A and B), depending on the regime of Reynolds number (Re). It is also found that the two different modes A and B exhibit different physical features of the flow. And many other important questions were addressed in this paper.展开更多
The flow around two tandem circular cylinders was studied by a three-dimensional numerical simulation of the Navier-Stokes equations at Re=220 . The improved virtual boundary method was applied to model the no-slip bo...The flow around two tandem circular cylinders was studied by a three-dimensional numerical simulation of the Navier-Stokes equations at Re=220 . The improved virtual boundary method was applied to model the no-slip boundary condition of the cylinders. The results show that as the spac ing ratio L/D≥4 , the three dimensionality occurs in the wake. When L/D≤3.5 the wake keeps a two-dimensional state at the Reynolds number Re=220 . The critical spacing for the appearance of three-dimensional instability obtained is at the range 3.5〈 L/D 〈 4, similar to the critical spacing found in two-dimensional case. Two sources of instability from upstream and downstream cylinder generate a complicat ed vortex structures in the wake, investigated by streamlines topology analysis in the streamwise plane. Many other interesting problems were also addressed in this paper.展开更多
Centrifugal compressors with parallel-wall and contracting wall vaneless diffuser are designed by using centrifugal compressor computer-aided integrated design system. The internal flow fields of the compressor are ca...Centrifugal compressors with parallel-wall and contracting wall vaneless diffuser are designed by using centrifugal compressor computer-aided integrated design system. The internal flow fields of the compressor are calculated by solving three-dimensional Navier-Stokes equation. Four aspects are investigated and calculation results show that the total efficiencies and total pressure ratios of the compressor with contracting wall vandess diffuser is higher than that of the compressor with parallel-wall. The jet and wake don＇t mix rapidly inside vandess diffuser. The outlet blade lean angle doesn＇t affect the compressor performance. The greater the mass flow rate through impeller, the more uneven the velocity distribution at impeller outlet is.展开更多
To improve the combustion chamber shape that can decrease the directed injection （DI） diesel emission, the theories of DI diesel spray, combustion and pollutant formation model are analysed and implemented based on ...To improve the combustion chamber shape that can decrease the directed injection （DI） diesel emission, the theories of DI diesel spray, combustion and pollutant formation model are analysed and implemented based on the CFD code FIRE. Results show that the chamber with contracting orifice can get stronger squish swirl intensity. The results of the verification studies show a good accordance with the measurements and reveal that the individual processes of spray, evolution, combustion and pollutant formation are well captured in FIRE. Finally, based on the analyzing and comparing of the calculation results of different chambers, a combustion chamber of contracting orifice geometry with lower emission is proposed.展开更多
Based on the multilevel model, numerical calculations of tidal current affected by the M-2 tide in the Tokyo Bay have been carried out. The results of calculation are compared with the data observed in the Tokyo Bay a...Based on the multilevel model, numerical calculations of tidal current affected by the M-2 tide in the Tokyo Bay have been carried out. The results of calculation are compared with the data observed in the Tokyo Bay and the result calculated by an approximate formula as the Tokyo Bay is regarded as a rectangular bay, and good agreement is found. It is proved that the mathematical model and the calculation method are correct and useable.展开更多
This paper investigates unsteady incompressible flow over cavities. Previous research in incompressible cavity-flow has included flow inside and past a 2-dimensional cavity, and flow inside a 3-dimensional cavity, dri...This paper investigates unsteady incompressible flow over cavities. Previous research in incompressible cavity-flow has included flow inside and past a 2-dimensional cavity, and flow inside a 3-dimensional cavity, driven by a moving lid. The present research is focused on incompressible flow past a 3-dimensional open shallow cavity. This involves the complex interaction between the external flow and the re-circulating flow within the cavity. In particular, computation was performed on a 3-dimensional shallow rectangular cavity with a laminar boundary layer at the cavity and a Reynolds number of 5,000 and 10,000, respectively. A CFD approach, based on the unsteady Navier-Stokes equations for 3-dimensional incompressible flow, was used in the study. Typical results of the computation are presented. These results reveal the highly unsteady and complex vortical structures at high Reynolds numbers.展开更多
Objective: The purpose of this study was to investigate the impact of intensity modulated radiotherapy (IMRT) on surface doses for brain, abdomen and pelvis deep located tumors treated with 6 MV photon and to evaluate...Objective: The purpose of this study was to investigate the impact of intensity modulated radiotherapy (IMRT) on surface doses for brain, abdomen and pelvis deep located tumors treated with 6 MV photon and to evaluate the skin dose calculation accuracy of the XIO 4.04 treatment planning system. Methods: More investigations for the influences of IMRT on skin doses would increase its applications for many treatment sites. Measuring skin doses in real treatment situations would reduce the uncertainty of skin dose prediction. In this work a pediatric human phantom was covered by a layer of 1 mm bolus at three treatment sites and thermoluminescent dosimeter (TLD) chips were inserted into the bolus at each treatment site before CT scan. Two different treatment plans [three-dimensional conformal radiation therapy (3DCRT) and IMRT] for each treatment sites were performed on XIO 4.04 treatment planning system using superposition algorism. Results: The results showed that the surface doses for 3DCRT were higher than the surface doses in IMRT by 1.6%, 2.5% and 3.2% for brain, abdomen and pelvis sites respectively. There was good agreement between measured and calculated surface doses, where the calculated surface dose was 15.5% for brain tumor calculated with 3DCRT whereas the measured surface dose was 12.1%. For abdomen site the calculated surface dose for IMRT treatment plan was 16.5% whereas the measured surface dose was 12.6%. Conclusion: The skin dose in IMRT for deep seated tumors is lower than that in 3DCRT which is another advantage for the IMRT. The TLD readings showed that the difference between the calculated and measured point dose is negligible. The superposition calculation algorism of the XIO 4.04 treatment planning system modeled the superficial dose well.展开更多
This study introduces an innovative screening approach to evaluate advanced oxidation processes (AOPs) as a preliminary diagnostic tool for degrading emerging contaminants (EC). It includes the design, prototyping, an...This study introduces an innovative screening approach to evaluate advanced oxidation processes (AOPs) as a preliminary diagnostic tool for degrading emerging contaminants (EC). It includes the design, prototyping, and cost-benefit analysis of circular photochemical reactors with flat and spiral internal geometries. Three-dimensional (3D) printing was used for reactor prototyping, providing flexibility and economy, and this stage was assisted by the hydrodynamic analysis of the prototypes based on residence time distribution (RTD) and macromixing models. The research evaluates the degradation of a model contaminant of emerging concern, fluoxetine (FLX) hydrochloride, using the solar/persulfate (PS) process in two water matrices (i.e., ultrapure water and sewage treatment plant effluent) to optimize reactor performance. The study also proposes primary theoretical pathways for fluoxetine degradation involving hydroxyl and sulfate radicals, as well as predicting the toxicity of the parent compound and its primary metabolites using quantitative structure-activity relationship (QSAR) models. The spiral reactor exhibits improved hydrodynamic behavior, closely resembling continuous stirred and plug flow reactors in series. Despite a slightly lower specific degradation rate in real wastewater, the solar/PS process remains effective for both matrices. By-products generated via the sulfate radical pathway are expected to be less toxic than those formed by hydroxyl radicals (HO·) attack.展开更多
Based on the method deriving dissipative compact linear schemes ( DCS), novel high-order dissipative weighted compact nonlinear schemes (DWCNS) are developed. By Fourier analysis, the dissipative and dispersive featur...Based on the method deriving dissipative compact linear schemes ( DCS), novel high-order dissipative weighted compact nonlinear schemes (DWCNS) are developed. By Fourier analysis, the dissipative and dispersive features of DWCNS are discussed. In view of the modified wave number, the DWCNS are equivalent to the fifth-order upwind biased explicit schemes in smooth regions and the interpolations at cell-edges dominate the accuracy of DWCNS. Boundary and near boundary schemes are developed and the asymptotic stabilities of DWCNS on both uniform and stretching grids are analyzed. The multi-dimensional implementations for Euler and Navier-Stokes equations are discussed. Several numerical inviscid and viscous results are given which show the good performances of the DWCNS for discontinuities capturing, high accuracy for boundary layer resolutions, good convergent rates (the root-mean-square of residuals approaching machine zero for solutions with strong shocks) and especially the damping effect on the spurious oscillations which were found in the solutions obtained by TVD and ENO schemes.展开更多
The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe（3 DAP） and first-principles calculation. The cluster analysis based on the maximum...The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe（3 DAP） and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni（Co-Ti） interactions than Co-Ti（Fe-Ti） interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition.展开更多
This paper presents a parallel Newton-Krylov-Schwarz method for the numerical simulation of unsteady flows at high Reynolds number around a high-speed train under crosswind.With a realistic train geometry,a realistic ...This paper presents a parallel Newton-Krylov-Schwarz method for the numerical simulation of unsteady flows at high Reynolds number around a high-speed train under crosswind.With a realistic train geometry,a realistic Reynolds number,and a realistic wind speed,this is a very challenging computational problem.Because of the limited parallel scalability,commercial CFD software is not suitable for supercomputers with a large number of processors.We develop a Newton-KrylovSchwarz based fully implicit method,and the corresponding parallel software,for the 3D unsteady incompressible Navier-Stokes equations discretized with a stabilized finite element method on very fine unstructured meshes.We test the algorithm and software for flows passing a train modeled after China’s high-speed train CRH380B,and we also compare our results with results obtained from commercial CFD software.Our algorithm shows very good parallel scalability on a supercomputer with over one thousand processors.展开更多
文摘The semidiagnostic and prognostic models are used to compute the current in the Taiwan Strait with wind and hydrographic data collected during August, 1984 and September 1 ~ 6, 1988. This calculation can be divided into two stages, i. e. (1 ) the adjustable stage; (2) prognostic calculation. The computed result shows tha the density and velocity fields etc. have been adjusted when t = 2. 5 d, namely the solution of semidignostic calculation is obtained,and the quasi-steady state solution have been reached after about 40 d. Comparing the results of diagncotic calculation with those of semidiagnortic and prognostic calculations indicates that they agree qualitatively. For example, they all have the following common features: (1 ) there is a persistent northward fiow with a volume transport of 0. 8 × 10 6 m3/s through the Taiwan Strait in summer; (2 ) the current near the western coas of Taiwan is stronger than that in other regiona; (3) the upweiling occurs near the Fujian coast and so on. However, there is a quantitative difference between them as follows. For example, the horizotal velocity near the westem cot of Taiwan and the upwelling speed near the Fujian aret both are underestimaed in the diagnestic calculation, because the data used in which is smoothed, and they both are intensified in the solutions of semidiagnostic and prognostic calculations. For example, the maximum velocity near the western coast of Taiwan at t = 0 d (diagnostic), 2. 5 d (semidiagnostic) and 300 d (prognostic) is 59.1, 62. 1 and 62. 0 cm/s, respectively. From the above comparison we see it is quite necessary that a semidiagnostic model be used to compute the currents when the data have been smoothed.
基金Project supported by the National Natural Science Foundation of China
文摘On the basis of a three-dimensional weakly nonliear theory of Lagrangian residual current in the Baroclinic shallow seas, a diagnostic numerical calculation of wind-driven, thermohaline and tide-induced Lagrangian residual current in the Bohai Sea is made. The model involves the Richardson number in the eddy viscosity coefficient, wind, thcrmolialine and tidal effects in the focing terms. The runoff of the Huanghe River and a part of the Huanghai Warm Water coming from the Huanghai Sea through the Bohai Sea Strait is also considered. The velocity-splitting method is adopted. The wind-driven circu lation, thermohaline circulation and the tide-induced Lagrangian residual circulation are also obtained individually and analysed. The dynamics of the three main eddies in the Lagrangian mean circulation is discussed. Finally, the numerical result is partly verified with the observed data.
基金Project(51274250)supported by the National Natural Science Foundation of ChinaProject(2012BAK09B02-05)supported by the National Key Technology R&D Program during the 12th Five-year Plan of China
文摘An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.
基金supported by the National Natural Science Foundation of China(Grant No.51379109)
文摘Slope excavation is one of the most crucial steps in the construction of a hydraulic project. Excavation project quality assessment and excavated volume calculation are critical in construction management. The positioning of excavation projects using traditional instruments is inefficient and may cause error. To improve the efficiency and precision of calculation and assessment, three-dimensional laser scanning technology was used for slope excavation quality assessment. An efficient data acquisition, processing, and management workflow was presented in this study. Based on the quality control indices, including the average gradient, slope toe elevation, and overbreak and underbreak,cross-sectional quality assessment and holistic quality assessment methods were proposed to assess the slope excavation quality with laserscanned data. An algorithm was also presented to calculate the excavated volume with laser-scanned data. A field application and a laboratory experiment were carried out to verify the feasibility of these methods for excavation quality assessment and excavated volume calculation. The results show that the quality assessment indices can be obtained rapidly and accurately with design parameters and scanned data, and the results of holistic quality assessment are consistent with those of cross-sectional quality assessment. In addition, the time consumption in excavation quality assessment with the laser scanning technology can be reduced by 70%e90%, as compared with the traditional method. The excavated volume calculated with the scanned data only slightly differs from measured data, demonstrating the applicability of the excavated volume calculation method presented in this study.
基金Project(2017YFC0404802)supported by the National Key R&D Program of ChinaProjects(U1965206,51979143)supported by the National Natural Science Foundation of China。
文摘In the finite element method,the numerical simulation of three-dimensional crack propagation is relatively rare,and it is often realized by commercial programs.In addition to the geometric complexity,the determination of the cracking direction constitutes a great challenge.In most cases,the local stress state provides the fundamental criterion to judge the presence of cracks and the direction of crack propagation.However,in the case of three-dimensional analysis,the coordination relationship between grid elements due to occurrence of cracks becomes a difficult problem for this method.In this paper,based on the extended finite element method,the stress-related function field is introduced into the calculation domain,and then the boundary value problem of the function is solved.Subsequently,the envelope surface of all propagation directions can be obtained at one time.At last,the possible surface can be selected as the direction of crack development.Based on the aforementioned procedure,such method greatly reduces the programming complexity of tracking the crack propagation.As a suitable method for simulating tension-induced failure,it can simulate multiple cracks simultaneously.
基金supported by the National Science Foundation of China under the Grant No.61176113 and 51335008the Special-funded program on national key scientific instruments and equipment development of China under the Grant No.2012YQ12004706the Program for Changjiang Scholars and Innovative Research Team in University(IRT1033)。
文摘Three-dimensional(3D) single-layer microcoils have always been a key element for electromagnetic systems;but they lack an easy and accurate method to calculate the inductance value for their complex 3D micro-structures. This paper employed a curve-fitting process to obtain the associated equation for the inductance value and geometric parameters based on the simulation results. The correction factors regarding helical pitch and wire diameter were reviewed,which are used for compensation in the Nagaoka formula. The simulation process numerically simulated the performance of the 3D microcoils using a FEM electro-magnetic-coupled analysis method. Comparison of the simulated inductance value and the Nagaoka formula was undertaken,which shows that the helical pitch and wire diameter contribute a main role in the calculation error. The derived formula was expressed in a concise form to precisely calculate the inductance value of 3D microsolenoids with single-layer coils.
文摘A three-dimensional numerical tsunami model is developed to analyze the nonlinear behavior of flow around obstacles with the Marker and Cell （MAC） method based on the Navier-Stokes equations. Tnrough a comparison with experimental data for the cases of dam break and solitary wave propagation, verification of the three-dimensional numerical model is given. Numerical experiment is performed for the analysis of the nonlinear behavior of flow around obstacles and compared with experimental data. The velocity and pressure around obstacles are presented with sufficient accuracy for tstmami propagation passing through an obstacle.
基金supported by the National Natural Science Foundation of China(Grant Nos.11372068 and 11572350)the National Basic Research Program of China(Grant No.2014CB744104)
文摘In this paper, the theory of constructing optimal dynamical systems based on weighted residual presented by Wu & Sha is applied to three-dimensional Navier-Stokes equations, and the optimal dynamical system modeling equations are derived. Then the multiscale global optimization method based on coarse graining analysis is presented, by which a set of approximate global optimal bases is directly obtained from Navier-Stokes equations and the construction of optimal dynamical systems is realized. The optimal bases show good properties, such as showing the physical properties of complex flows and the turbulent vortex structures, being intrinsic to real physical problem and dynamical systems, and having scaling symmetry in mathematics, etc.. In conclusion, using fewer terms of optimal bases will approach the exact solutions of Navier-Stokes equations, and the dynamical systems based on them show the most optimal behavior.
文摘With the development and progress of science and technology,road and bridge design has experienced rapid development,from the initial manual drawing design to the popularity of Computer-Aided Design(CAD),and then to today’s digital software design era.Early designers relied on hand-drawn paper design forms which was time-consuming and error-prone.Digital support for road and bridge design not only saves the design time but the design quality has also achieved a qualitative leap.This paper engages in the application of digital technology in road and bridge design,to provide technical reference for China’s road and bridge engineering design units,to promote the popularity of Civil3D and other advanced design software in the field of engineering design and development,ultimately contributing to the sustainable development of China’s road and bridge engineering.
文摘The studies concerning the wake transition regime of the flow around a circular cylinder have drawn much attention in these years. Many experiments have been conducted for this problem but no accurate three-dimensional numerical simulations have hitherto been made. In this paper, a parallel procedure was developed to solve the three-dimensional Navier-Stokes equations on an SGI Origin3900 machine. Two different parallel strategies on this application were analyzed about their efficiency. It is found that the critical Reynolds number is 195, and the wake flow below this Reynolds number is purely two-dimensional one, while the Reynolds number goes beyond this critical point, the wake flow becomes unstable under three-dimensional small disturbances. The transition regime involves two modes of small-scale three-dimensional instability (modes A and B), depending on the regime of Reynolds number (Re). It is also found that the two different modes A and B exhibit different physical features of the flow. And many other important questions were addressed in this paper.
基金Project supported by the National Natural Science Foundation of China(Grant No :10272094)
文摘The flow around two tandem circular cylinders was studied by a three-dimensional numerical simulation of the Navier-Stokes equations at Re=220 . The improved virtual boundary method was applied to model the no-slip boundary condition of the cylinders. The results show that as the spac ing ratio L/D≥4 , the three dimensionality occurs in the wake. When L/D≤3.5 the wake keeps a two-dimensional state at the Reynolds number Re=220 . The critical spacing for the appearance of three-dimensional instability obtained is at the range 3.5〈 L/D 〈 4, similar to the critical spacing found in two-dimensional case. Two sources of instability from upstream and downstream cylinder generate a complicat ed vortex structures in the wake, investigated by streamlines topology analysis in the streamwise plane. Many other interesting problems were also addressed in this paper.
文摘Centrifugal compressors with parallel-wall and contracting wall vaneless diffuser are designed by using centrifugal compressor computer-aided integrated design system. The internal flow fields of the compressor are calculated by solving three-dimensional Navier-Stokes equation. Four aspects are investigated and calculation results show that the total efficiencies and total pressure ratios of the compressor with contracting wall vandess diffuser is higher than that of the compressor with parallel-wall. The jet and wake don＇t mix rapidly inside vandess diffuser. The outlet blade lean angle doesn＇t affect the compressor performance. The greater the mass flow rate through impeller, the more uneven the velocity distribution at impeller outlet is.
文摘To improve the combustion chamber shape that can decrease the directed injection （DI） diesel emission, the theories of DI diesel spray, combustion and pollutant formation model are analysed and implemented based on the CFD code FIRE. Results show that the chamber with contracting orifice can get stronger squish swirl intensity. The results of the verification studies show a good accordance with the measurements and reveal that the individual processes of spray, evolution, combustion and pollutant formation are well captured in FIRE. Finally, based on the analyzing and comparing of the calculation results of different chambers, a combustion chamber of contracting orifice geometry with lower emission is proposed.
文摘Based on the multilevel model, numerical calculations of tidal current affected by the M-2 tide in the Tokyo Bay have been carried out. The results of calculation are compared with the data observed in the Tokyo Bay and the result calculated by an approximate formula as the Tokyo Bay is regarded as a rectangular bay, and good agreement is found. It is proved that the mathematical model and the calculation method are correct and useable.
文摘This paper investigates unsteady incompressible flow over cavities. Previous research in incompressible cavity-flow has included flow inside and past a 2-dimensional cavity, and flow inside a 3-dimensional cavity, driven by a moving lid. The present research is focused on incompressible flow past a 3-dimensional open shallow cavity. This involves the complex interaction between the external flow and the re-circulating flow within the cavity. In particular, computation was performed on a 3-dimensional shallow rectangular cavity with a laminar boundary layer at the cavity and a Reynolds number of 5,000 and 10,000, respectively. A CFD approach, based on the unsteady Navier-Stokes equations for 3-dimensional incompressible flow, was used in the study. Typical results of the computation are presented. These results reveal the highly unsteady and complex vortical structures at high Reynolds numbers.
文摘Objective: The purpose of this study was to investigate the impact of intensity modulated radiotherapy (IMRT) on surface doses for brain, abdomen and pelvis deep located tumors treated with 6 MV photon and to evaluate the skin dose calculation accuracy of the XIO 4.04 treatment planning system. Methods: More investigations for the influences of IMRT on skin doses would increase its applications for many treatment sites. Measuring skin doses in real treatment situations would reduce the uncertainty of skin dose prediction. In this work a pediatric human phantom was covered by a layer of 1 mm bolus at three treatment sites and thermoluminescent dosimeter (TLD) chips were inserted into the bolus at each treatment site before CT scan. Two different treatment plans [three-dimensional conformal radiation therapy (3DCRT) and IMRT] for each treatment sites were performed on XIO 4.04 treatment planning system using superposition algorism. Results: The results showed that the surface doses for 3DCRT were higher than the surface doses in IMRT by 1.6%, 2.5% and 3.2% for brain, abdomen and pelvis sites respectively. There was good agreement between measured and calculated surface doses, where the calculated surface dose was 15.5% for brain tumor calculated with 3DCRT whereas the measured surface dose was 12.1%. For abdomen site the calculated surface dose for IMRT treatment plan was 16.5% whereas the measured surface dose was 12.6%. Conclusion: The skin dose in IMRT for deep seated tumors is lower than that in 3DCRT which is another advantage for the IMRT. The TLD readings showed that the difference between the calculated and measured point dose is negligible. The superposition calculation algorism of the XIO 4.04 treatment planning system modeled the superficial dose well.
基金supports of the São Paulo Research Foundation(FAPESP)(Grant Nos.2018/21271-6,2019/24158-9 and 2022/13583-3)the Goiás Research Foundation(FAPEG)(Grant No.GSP2019011000037)the National Council for Scientific and Technological Development—Brazil(CNPq)(Grant Nos.311230/2020-2 and 309154/2023-5).
文摘This study introduces an innovative screening approach to evaluate advanced oxidation processes (AOPs) as a preliminary diagnostic tool for degrading emerging contaminants (EC). It includes the design, prototyping, and cost-benefit analysis of circular photochemical reactors with flat and spiral internal geometries. Three-dimensional (3D) printing was used for reactor prototyping, providing flexibility and economy, and this stage was assisted by the hydrodynamic analysis of the prototypes based on residence time distribution (RTD) and macromixing models. The research evaluates the degradation of a model contaminant of emerging concern, fluoxetine (FLX) hydrochloride, using the solar/persulfate (PS) process in two water matrices (i.e., ultrapure water and sewage treatment plant effluent) to optimize reactor performance. The study also proposes primary theoretical pathways for fluoxetine degradation involving hydroxyl and sulfate radicals, as well as predicting the toxicity of the parent compound and its primary metabolites using quantitative structure-activity relationship (QSAR) models. The spiral reactor exhibits improved hydrodynamic behavior, closely resembling continuous stirred and plug flow reactors in series. Despite a slightly lower specific degradation rate in real wastewater, the solar/PS process remains effective for both matrices. By-products generated via the sulfate radical pathway are expected to be less toxic than those formed by hydroxyl radicals (HO·) attack.
基金This work was supported by the project of Basic Research on Frontier Problems in Fluid and Aerodynamics China and the National Natural Science Foundation of China (Grant No.19772072) .
文摘Based on the method deriving dissipative compact linear schemes ( DCS), novel high-order dissipative weighted compact nonlinear schemes (DWCNS) are developed. By Fourier analysis, the dissipative and dispersive features of DWCNS are discussed. In view of the modified wave number, the DWCNS are equivalent to the fifth-order upwind biased explicit schemes in smooth regions and the interpolations at cell-edges dominate the accuracy of DWCNS. Boundary and near boundary schemes are developed and the asymptotic stabilities of DWCNS on both uniform and stretching grids are analyzed. The multi-dimensional implementations for Euler and Navier-Stokes equations are discussed. Several numerical inviscid and viscous results are given which show the good performances of the DWCNS for discontinuities capturing, high accuracy for boundary layer resolutions, good convergent rates (the root-mean-square of residuals approaching machine zero for solutions with strong shocks) and especially the damping effect on the spurious oscillations which were found in the solutions obtained by TVD and ENO schemes.
基金sponsored by Youth Innovation Promotion Association of Chinese Academy of Sciences (2017233)National Natural Science Foundation of C hina (No. 51472249)+2 种基金Innovation Project of Institute of Metal Research (2015-ZD04)National Natural Science Foundation of China Research Fund for International Young Scientists (No. 51750110515)the Special Program for Applied Research on Super Computation of the NSFCGuangdong Joint Fund (second phase) under Grant No. U1501501
文摘The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe（3 DAP） and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni（Co-Ti） interactions than Co-Ti（Fe-Ti） interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition.
基金supported in part by the Knowledge Innovation Program of the Chinese Academy of Sciences under KJCX2-EW-L01the International Cooperation Project of Guangdong province under 2011B050400037.
文摘This paper presents a parallel Newton-Krylov-Schwarz method for the numerical simulation of unsteady flows at high Reynolds number around a high-speed train under crosswind.With a realistic train geometry,a realistic Reynolds number,and a realistic wind speed,this is a very challenging computational problem.Because of the limited parallel scalability,commercial CFD software is not suitable for supercomputers with a large number of processors.We develop a Newton-KrylovSchwarz based fully implicit method,and the corresponding parallel software,for the 3D unsteady incompressible Navier-Stokes equations discretized with a stabilized finite element method on very fine unstructured meshes.We test the algorithm and software for flows passing a train modeled after China’s high-speed train CRH380B,and we also compare our results with results obtained from commercial CFD software.Our algorithm shows very good parallel scalability on a supercomputer with over one thousand processors.
