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Jianyun Chen - One of the best experts on this subject based on the ideXlab platform.
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sensitive analysis of water levels and Air Intakes on natural frequency of ap1000 nuclear island building considering fsi effects
Annals of Nuclear Energy, 2015Co-Authors: Chunfeng Zhao, Jianyun Chen, Xiaoyan YangAbstract:AP1000 is an advanced generation III+ nuclear power plant which utilizes a series of passive safety features. The main component of AP1000 is nuclear island which consists of containment vessel, shield building and auxiliary building. Water storage tank and Air intake are two of the most important components of nuclear island for cooling down the containment vessel when an accident happens. The fluid–structure interaction effects and the locations of Air Intakes may affect the vibration characteristics of the nuclear island. In a previous paper, the influence of water level and elevation of Air Intakes on dynamic characteristics of shield building was studied. A more detailed model of AP1000 nuclear island including auxiliary and internal structures should be built and analyzed to obtain more reliable results due to the complex shape and arrangement of AP1000. The purpose of this paper is to investigate the influence of various water levels and different locations of Air Intakes on natural frequency of the overall nuclear island of AP1000 by modal analysis considering fluid–structure interaction effects. The results of finite element analysis indicate that the first two natural frequencies decrease as the water levels increase while the 3rd and the 4th frequencies are almost constant, and the elevation of Air intake has an insignificant impact on the natural frequencies of the nuclear island building. In addition, the height ratios of h1/H and h2/H also influence the vibration characteristics of nuclear island building. The variation of stiffness as location of Air intake is very small compared to the integral rigidity of the overall nuclear island.
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dynamic analysis of ap1000 shield building for various elevations and shapes of Air Intakes considering fsi effects subjected to seismic loading
Progress in Nuclear Energy, 2014Co-Authors: Chunfeng Zhao, Jianyun ChenAbstract:Abstract The shield building of AP1000 was designed to protect the steel containment vessel of nuclear power plants. When an accident releases mass energy to containment, natural circulation of Air outside containment cools steel containment vessel by Air intake and water drains by gravity to enhance cooling with evaporation. However, the Air intake in the original design located around the upper corner of shield building may not be the optimal position of shield building. In the previous study, the influence of various elevations and shapes of Air intake on natural frequency considering fluid-structure effects under different water levels has been performed. In the present study, three elevations and two shapes (rectangle and circle) of Air Intakes with 71.3, 64.75 and 58.21 m are established and expressed as location I, II and III, respectively. The influences of various elevations and shapes of Air intake on the structural response and stress distribution of shield building considering fluid-structure effects under seismic loading are also performed to identify the optimal design for stress analysis to improve the passive cooling system for AP1000 and CAP1400 (in China) in the future. The results of structural analyses indicated that the von Mises stress of both rectangular and circular Air Intakes at the lower location were greater than that of the higher location, and the stress for circular Air intake was less than that of rectangular Air intake under seismic loading. In addition, the simulation result also indicated that an optimal elevation of Air intake should be implemented around the location II of shield building with circular shape, and the original design of Air intake located around the upper corner of shield building may not be the optimal arrangement.
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dynamic characteristics of ap1000 shield building for various water levels and Air Intakes considering fluid structure interaction
Progress in Nuclear Energy, 2014Co-Authors: Chunfeng Zhao, Jianyun ChenAbstract:Abstract The shield building of AP1000 was designed to protect the steel containment vessel of nuclear power plants. When the reactor is shutdown, the gravity drain water tank mounted above the shield building sprays water, and the intake of ambient Air cools down the temperature of containment vessel through buoyancy driven circulation. However, original design of AP1000 by Westinghouse electric company, Air Intakes located around the corner of the shield building may not be the optimal arrangements. A systematic and progressive modal analysis should be carried out to characterize the dynamic behavior of shield building, considering fluid-structure interaction under different water levels. The influences of elevations and shapes of Air Intakes on the natural frequencies of shield building are also presented in this paper to improve the optimal parametric design of the AP1000 and CAP1400 (in China) by using appropriate passive Air intake in the future. An important conclusion is that the natural frequency increases as the water level decreasing, and elevation of Air intake also affects the frequency for various shapes of Air Intakes. In addition, it has been observed that the shape of Air intake took a slight influence on the change of natural frequency, the circular Air Intakes made the structure more flexible than that of rectangular Air intake. It is also important to note that elevation and shape of Air intake may have a significant influence on stress distribution of the structure. Therefore, it is necessary to study the influence of the stress distribution for various shapes and elevations of Air intake for various water levels in the future.
Chunfeng Zhao - One of the best experts on this subject based on the ideXlab platform.
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sensitive analysis of water levels and Air Intakes on natural frequency of ap1000 nuclear island building considering fsi effects
Annals of Nuclear Energy, 2015Co-Authors: Chunfeng Zhao, Jianyun Chen, Xiaoyan YangAbstract:AP1000 is an advanced generation III+ nuclear power plant which utilizes a series of passive safety features. The main component of AP1000 is nuclear island which consists of containment vessel, shield building and auxiliary building. Water storage tank and Air intake are two of the most important components of nuclear island for cooling down the containment vessel when an accident happens. The fluid–structure interaction effects and the locations of Air Intakes may affect the vibration characteristics of the nuclear island. In a previous paper, the influence of water level and elevation of Air Intakes on dynamic characteristics of shield building was studied. A more detailed model of AP1000 nuclear island including auxiliary and internal structures should be built and analyzed to obtain more reliable results due to the complex shape and arrangement of AP1000. The purpose of this paper is to investigate the influence of various water levels and different locations of Air Intakes on natural frequency of the overall nuclear island of AP1000 by modal analysis considering fluid–structure interaction effects. The results of finite element analysis indicate that the first two natural frequencies decrease as the water levels increase while the 3rd and the 4th frequencies are almost constant, and the elevation of Air intake has an insignificant impact on the natural frequencies of the nuclear island building. In addition, the height ratios of h1/H and h2/H also influence the vibration characteristics of nuclear island building. The variation of stiffness as location of Air intake is very small compared to the integral rigidity of the overall nuclear island.
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dynamic analysis of ap1000 shield building for various elevations and shapes of Air Intakes considering fsi effects subjected to seismic loading
Progress in Nuclear Energy, 2014Co-Authors: Chunfeng Zhao, Jianyun ChenAbstract:Abstract The shield building of AP1000 was designed to protect the steel containment vessel of nuclear power plants. When an accident releases mass energy to containment, natural circulation of Air outside containment cools steel containment vessel by Air intake and water drains by gravity to enhance cooling with evaporation. However, the Air intake in the original design located around the upper corner of shield building may not be the optimal position of shield building. In the previous study, the influence of various elevations and shapes of Air intake on natural frequency considering fluid-structure effects under different water levels has been performed. In the present study, three elevations and two shapes (rectangle and circle) of Air Intakes with 71.3, 64.75 and 58.21 m are established and expressed as location I, II and III, respectively. The influences of various elevations and shapes of Air intake on the structural response and stress distribution of shield building considering fluid-structure effects under seismic loading are also performed to identify the optimal design for stress analysis to improve the passive cooling system for AP1000 and CAP1400 (in China) in the future. The results of structural analyses indicated that the von Mises stress of both rectangular and circular Air Intakes at the lower location were greater than that of the higher location, and the stress for circular Air intake was less than that of rectangular Air intake under seismic loading. In addition, the simulation result also indicated that an optimal elevation of Air intake should be implemented around the location II of shield building with circular shape, and the original design of Air intake located around the upper corner of shield building may not be the optimal arrangement.
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dynamic characteristics of ap1000 shield building for various water levels and Air Intakes considering fluid structure interaction
Progress in Nuclear Energy, 2014Co-Authors: Chunfeng Zhao, Jianyun ChenAbstract:Abstract The shield building of AP1000 was designed to protect the steel containment vessel of nuclear power plants. When the reactor is shutdown, the gravity drain water tank mounted above the shield building sprays water, and the intake of ambient Air cools down the temperature of containment vessel through buoyancy driven circulation. However, original design of AP1000 by Westinghouse electric company, Air Intakes located around the corner of the shield building may not be the optimal arrangements. A systematic and progressive modal analysis should be carried out to characterize the dynamic behavior of shield building, considering fluid-structure interaction under different water levels. The influences of elevations and shapes of Air Intakes on the natural frequencies of shield building are also presented in this paper to improve the optimal parametric design of the AP1000 and CAP1400 (in China) by using appropriate passive Air intake in the future. An important conclusion is that the natural frequency increases as the water level decreasing, and elevation of Air intake also affects the frequency for various shapes of Air Intakes. In addition, it has been observed that the shape of Air intake took a slight influence on the change of natural frequency, the circular Air Intakes made the structure more flexible than that of rectangular Air intake. It is also important to note that elevation and shape of Air intake may have a significant influence on stress distribution of the structure. Therefore, it is necessary to study the influence of the stress distribution for various shapes and elevations of Air intake for various water levels in the future.
Lefieux Julien - One of the best experts on this subject based on the ideXlab platform.
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Etude DNS de la transition déclenchée par rugosité dans les écoulements hypersoniques
HAL CCSD, 2021Co-Authors: Lefieux JulienAbstract:Understanding and predicting the effect of roughness on the laminar-turbulent transition in hypersonic boundary-layers will help the design of hypersonic flight vehicles. For this type of vehicle, it is often necessary to be able to trip the transition to turbulence upstream of Air Intakes. This thesis consists in studying the roughness-induced transition mechanisms in hypersonic flows. Direct numerical simulations have been performed using the Chimera method to identify the roughnessinduced transition mechanisms on a wedge-like forebody at Mach 6 and unit Reynolds number Re = 11 million (/m). Reasonable agreement with the experiments performed in the BAM6QT Quiet Tunnel at Purdue University was obtained in terms of wall heat flux and wall pressure fluctuations. First, an isolated roughness was considered. The presence of the roughness in the span-inhomogeneous base flow leads to the formation of a crossflow-like vortex. Highfrequency secondary instabilities of the stationary crossflow vortex are observed in the wake and are found to be responsible for the breakdown to turbulence. Spatial linear modal instability analysis of this flow has been performed at selected streamwise locations. The linear stability approach was found to give accurate predictions in terms of mode shapes, most amplified disturbance frequencies and growth rate as it only underpredicts the N-factor of the most unstable mode by 10% compared to the direct numerical simulations.Cette étude s'inscrit dans le cadre des études et recherches sur de futurs véhicules hypersoniques à propulsion aérobie. Pour ce type de véhicule, il est souvent nécessAire de déclencher la transition laminAire-turbulent en amont des prises d'Air, au moyen de rugosité. Le travail de cette thèse consiste donc à étudier finement les mécanismes de transition déclenchée par rugosité dans les écoulements hypersoniques. Des simulations numériques directes ont été réalisées avec la méthode Chimère afin d'identifier les mécanismes de transition déclenchée par rugosité sur un avant-corps générique à Mach 7 et un nombre de Reynolds de Re = 11 million (/m). Un accord raisonnable a été obtenu avec les résultats des tests effectués dans la soufflerie silencieuse BAM6QT de l'Université de Purdue, en terme de flux de chaleur et de fluctuations de pression à la paroi. Une rugosité isolée a été considérée. La présence de la rugosité dans l'écoulement de base nonhomogène en envergure génère un tourbillon de type crossflow. A haute fréquence, des instabilités secondAires du tourbillon de crossflow stationnAire sont observées dans le sillage de la rugosité et sont considérées comme responsable de la transition. Des calculs de stabilité linéAire bi-locale ont été effectués à différentes positions axiales. L'approche de stabilité linéAire s'est révélée précise pour la prévision des modes propres, des fréquences les plus amplifiées et du taux d'amplification des instabilités
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Etude DNS de la transition déclenchée par rugosité à Mach 6
'American Institute of Aeronautics and Astronautics (AIAA)', 2019Co-Authors: Lefieux Julien, Garnier Eric, Sandham, Neil D.Abstract:International audienceIn hypersonic flows, it is useful to be able to trip the transition to turbulence upstream of Air Intakes for example. In the present work, direct numerical simulations have been performed of the flow past an isolated roughness element at Mach 6. First, the capability of two solvers to compute laminar and transitional flow involving freestream disturbances was demonstrated. A series of simulations was then carried out without acoustic perturbation of the freestream. The Reynolds number was increased from 14,000, to 28,000 and then to 40,000. The first two cases remain laminar within the computational domain, whereas the last case undergoes a self-sustained transition to turbulence. A response to a perturbation impulse shows the presence of a varicose mode at the intermediate Reynolds number and a sinuous mode at the largest Reynolds number.Dans les écoulements hypersoniques, il est nécessAire de pouvoir déclencher la transition vers la turbulence en amont des prises d'Air par exemple. Dans cette étude, des simulations numériques directes de l'écoulement autour d'une rugosité isolée à Mach 6 ont été réalisées Dans un premier temps la capacité de deux solveurs à prédire l'écoulement laminAire ainsi que transitionnel impliquant des perturbations acoustiques a été démontrée. Une série de simulations a ensuite été réalisée à Mach 6 avec perturbations acoustiques. Le nombre de Reynolds a été augmenté de 14,000 à 28,000 puis à 40,000. Les deux premiers cas demeurent laminAires, alors que le dernier cas expérience une transition auto-entretenue vers la turbulence.Une étude de la réponse à une perturbation impulsionnelle montre la présence d'une instabilité variqueuse au nombre de Reynolds intermédiAire, et une instabilité sinueuse au plus fort nombre de Reynolds
Zheming Tong - One of the best experts on this subject based on the ideXlab platform.
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microenvironmental Air quality impact of a commercial scale biomass heating system
Environmental Pollution, 2017Co-Authors: Zheming Tong, Bo Yang, Philip K Hopke, Max K ZhangAbstract:Abstract Initiatives to displace petroleum and climate change mitigation have driven a recent increase in space heating with biomass combustion. However, there is ample evidence that biomass combustion emits significant quantities of health damaging pollutants. We investigated the near-source micro-environmental Air quality impact of a biomass-fueled combined heat and power system equipped with an electrostatic precipitator (ESP) in Syracuse, NY. Two rooftop sampling stations with PM 2.5 and CO 2 analyzers were established in such that one could capture the plume while the other one served as the background for comparison depending on the wind direction. Four sonic anemometers were deployed around the stack to quantify spatially and temporally resolved local wind patterns. Fuel-based emission factors were derived based on near-source measurement. The Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG) model was then applied to simulate the spatial variations of primary PM 2.5 without ESP. Our analysis shows that the absence of ESP could lead to an almost 7 times increase in near-source primary PM 2.5 concentrations with a maximum concentration above 100 μg m −3 at the building rooftop. The above-ground “hotspots” would pose potential health risks to building occupants since particles could penetrate indoors via infiltration, natural ventilation, and fresh Air Intakes on the rooftop of multiple buildings. Our results demonstrated the importance of emission control for biomass combustion systems in urban area, and the need to take above-ground pollutant “hotspots” into account when permitting distributed generation. The effects of ambient wind speed and stack temperature, the suitability of Airport meteorological data on micro-environmental Air quality were explored, and the implications on mitigating near-source Air pollution were discussed.
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quantifying the impact of traffic related Air pollution on the indoor Air quality of a naturally ventilated building
Environment International, 2016Co-Authors: Zheming Tong, Yujiao Chen, Ali Malkawi, Gary Adamkiewicz, John D SpenglerAbstract:Improper natural ventilation practices may deteriorate indoor Air quality when in close proximity to roadways, although the intention is often to reduce energy consumption. In this study, we employed a CFD-based Air quality model to quantify the impact of traffic-related Air pollution on the indoor Air quality of a naturally ventilated building. Our study found that the building envelope restricts dispersion and dilution of particulate matter. The indoor concentration in the baseline condition located 10m away from the roadway is roughly 16-21% greater than that at the edge of the roadway. The indoor flow recirculation creates a well-mixed zone with little variation in fine particle concentration (i.e., 253nm). For ultrafine particles (<100nm), a noticeable decrease in particle concentrations indoors with increasing distance from the road is observed due to Brownian and turbulent diffusion. In addition, the indoor concentration strongly depends on the distance between the roadway and building, particle size, wind condition, and window size and location. A break-even point is observed at D'~2.1 (normalized distance from the roadway by the width of the road). The indoor particle concentration is greater than that at the highway where D'<2.1, and vice versa. For new building planning, the distance from the roadway and the ambient wind condition need to be considered at the early design stage whereas the size and location of the window openings, the interior layout, and the placement of fresh Air Intakes are important to the indoor Air quality of existing buildings adjacent to roadways.
John D Spengler - One of the best experts on this subject based on the ideXlab platform.
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quantifying the impact of traffic related Air pollution on the indoor Air quality of a naturally ventilated building
Environment International, 2016Co-Authors: Zheming Tong, Yujiao Chen, Ali Malkawi, Gary Adamkiewicz, John D SpenglerAbstract:Improper natural ventilation practices may deteriorate indoor Air quality when in close proximity to roadways, although the intention is often to reduce energy consumption. In this study, we employed a CFD-based Air quality model to quantify the impact of traffic-related Air pollution on the indoor Air quality of a naturally ventilated building. Our study found that the building envelope restricts dispersion and dilution of particulate matter. The indoor concentration in the baseline condition located 10m away from the roadway is roughly 16-21% greater than that at the edge of the roadway. The indoor flow recirculation creates a well-mixed zone with little variation in fine particle concentration (i.e., 253nm). For ultrafine particles (<100nm), a noticeable decrease in particle concentrations indoors with increasing distance from the road is observed due to Brownian and turbulent diffusion. In addition, the indoor concentration strongly depends on the distance between the roadway and building, particle size, wind condition, and window size and location. A break-even point is observed at D'~2.1 (normalized distance from the roadway by the width of the road). The indoor particle concentration is greater than that at the highway where D'<2.1, and vice versa. For new building planning, the distance from the roadway and the ambient wind condition need to be considered at the early design stage whereas the size and location of the window openings, the interior layout, and the placement of fresh Air Intakes are important to the indoor Air quality of existing buildings adjacent to roadways.