The Experts below are selected from a list of 95868 Experts worldwide ranked by ideXlab platform
Xikun Wang - One of the best experts on this subject based on the ideXlab platform.
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numerical study on pressure fluctuation of a multistage centrifugal Pump based on whole flow field
AIP Advances, 2019Co-Authors: Chuan Wang, Xiaoke He, Xikun Wang, Xiuli WangAbstract:Multistage centrifugal Pumps can provide high-pressure fluid flow, and is widely used in various engineering applications. However, the pressure fluctuation in the Pumps strongly affects the flow and pressure stability. To gain further insight into the pressure fluctuation of multistage centrifugal Pumps, a numerical Model of a typical multistage centrifugal Pump Model was constructed and the flow investigated systematically under different operating conditions. Changes in amplitude, frequency, and phase of pressure fluctuation in the impellers, diffusers, and Pump cavities were observed and analyzed in both time-domain and frequency-domain. The pressure fluctuations of the fluid in the impeller were found to originate from the inlet side of the outward diffuser, whereas that in the diffuser arose from the outlet side of the impeller blade. In contrast, the pressure fluctuations in the Pump cavity were initiated from the outlet side of the impeller blade and the interstage leakage of fluid. This study also conclude that the pressure fluctuations are essentially a wave with identifiable amplitude, frequency, and phase.Multistage centrifugal Pumps can provide high-pressure fluid flow, and is widely used in various engineering applications. However, the pressure fluctuation in the Pumps strongly affects the flow and pressure stability. To gain further insight into the pressure fluctuation of multistage centrifugal Pumps, a numerical Model of a typical multistage centrifugal Pump Model was constructed and the flow investigated systematically under different operating conditions. Changes in amplitude, frequency, and phase of pressure fluctuation in the impellers, diffusers, and Pump cavities were observed and analyzed in both time-domain and frequency-domain. The pressure fluctuations of the fluid in the impeller were found to originate from the inlet side of the outward diffuser, whereas that in the diffuser arose from the outlet side of the impeller blade. In contrast, the pressure fluctuations in the Pump cavity were initiated from the outlet side of the impeller blade and the interstage leakage of fluid. This study als...
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numerical study on pressure fluctuation of a multistage centrifugal Pump based on whole flow field
AIP Advances, 2019Co-Authors: Chuan Wang, Weidong Shi, Xikun Wang, Xiuli Wang, Ning QiuAbstract:Multistage centrifugal Pumps can provide high-pressure fluid flow, and is widely used in various engineering applications. However, the pressure fluctuation in the Pumps strongly affects the flow and pressure stability. To gain further insight into the pressure fluctuation of multistage centrifugal Pumps, a numerical Model of a typical multistage centrifugal Pump Model was constructed and the flow investigated systematically under different operating conditions. Changes in amplitude, frequency, and phase of pressure fluctuation in the impellers, diffusers, and Pump cavities were observed and analyzed in both time-domain and frequency-domain. The pressure fluctuations of the fluid in the impeller were found to originate from the inlet side of the outward diffuser, whereas that in the diffuser arose from the outlet side of the impeller blade. In contrast, the pressure fluctuations in the Pump cavity were initiated from the outlet side of the impeller blade and the interstage leakage of fluid. This study also conclude that the pressure fluctuations are essentially a wave with identifiable amplitude, frequency, and phase.
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validation of an axial flow blood Pump computational fluid dynamics results using particle image velocimetry
Artificial Organs, 2012Co-Authors: Leok Poh Chua, Xikun WangAbstract:A magnetically suspended axial flow blood Pump is studied experimentally in this article. The Pump casing enclosed a three-blade straightener, a two-blade impeller shrouded by a permanent magnet-embedded cylinder, and a three-blade diffuser. The internal flow fields were simulated earlier using computational fluid dynamics (CFD), and the Pump characteristic curves were determined. The simulation results showed that the internal flow field was basically streamlined, except the diffuser region. Particle image velocimetry (PIV) measurement of the 1:1 Pump Model was conducted to validate the CFD result. In order to ensure the optical access, an acrylic prototype was fabricated with the impeller driven by a servomotor instead, as the magnet is opaque. In addition to the transparent Model, the blood analog fluid with the refractive index close to that of acrylic was used to avoid refraction. According to the CFD results, the axial flow blood Pump could generate adequate pressure head at the rotating speed of 9500rpm and flow rate of 5L/min, and the same flow condition was applied during the PIV measurement. Through the comparisons, it was found that the experimental results were close to those obtained by CFD and had thus validated the CFD Model, which could complement the limitation of the measurement in assessing the more detailed flow fields of the axial flow Pump.
Rafe M Brown - One of the best experts on this subject based on the ideXlab platform.
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the comparative biogeography of philippine geckos challenges predictions from a paradigm of climate driven vicariant diversification across an island archipelago
Evolution, 2019Co-Authors: Jamie R Oaks, Cameron D Siler, Rafe M BrownAbstract:A primary goal of biogeography is to understand how large-scale environmental processes, like climate change, affect diversification. One often-invoked but seldom tested process is the "species-Pump" Model, in which repeated bouts of cospeciation are driven by oscillating climate-induced habitat connectivity cycles. For example, over the past three million years, the landscape of the Philippine Islands has repeatedly coalesced and fragmented due to sea-level changes associated with glacial cycles. This repeated climate-driven vicariance has been proposed as a Model of speciation across evolutionary lineages codistributed throughout the islands. This Model predicts speciation times that are temporally clustered around the times when interglacial rises in sea level fragmented the islands. To test this prediction, we collected comparative genomic data from 16 pairs of insular gecko populations. We analyze these data in a full-likelihood, Bayesian Model-choice framework to test for shared divergence times among the pairs. Our results provide support against the species-Pump Model prediction in favor of an alternative interpretation, namely that each pair of gecko populations diverged independently. These results suggest the repeated bouts of climate-driven landscape fragmentation have not been an important mechanism of speciation for gekkonid lizards across the Philippine Archipelago.
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the comparative biogeography of philippine geckos challenges predictions from a paradigm of climate driven vicariant diversification across an island archipelago
bioRxiv, 2019Co-Authors: Jamie R Oaks, Cameron D Siler, Rafe M BrownAbstract:Abstract A primary goal of biogeography is to understand how large-scale environmental processes, like climate change, affect diversification One often-invoked but seldom tested process is the “species-Pump” Model, in which repeated bouts of co-speciation are driven by oscillating climate-induced habitat connectivity cycles. For example, over the past three million years, the landscape of the Philippine Islands has repeatedly coalesced and fragmented due to sea-level changes associated with glacial cycles. This repeated climate-driven vicariance has been proposed as a Model of speciation across evolutionary lineages codistributed throughout the islands. This Model predicts speciation times that are temporally clustered around the times when interglacial rises in sea level fragmented the islands. To test this prediction, we collected comparative genomic data from 16 pairs of insular gecko populations. We analyze these data in a full-likelihood, Bayesian Model-choice framework to test for shared divergence times among the pairs. Our results provide support against the species-Pump Model prediction in favor of an alternative interpretation, namely that each pair of gecko populations diverged independently. These results suggest the repeated bouts of climate-driven landscape fragmentation has not been an important mechanism of speciation for gekkonid lizards on the Philippine Islands.
Gunter Rockendorf - One of the best experts on this subject based on the ideXlab platform.
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investigations and Model validation of a ground coupled heat Pump for the combination with solar collectors
Applied Thermal Engineering, 2014Co-Authors: Peter Parisch, Oliver Mercker, Jonas Warmuth, Rainer Tepe, Erik Bertram, Gunter RockendorfAbstract:Abstract The operation of ground-coupled heat Pumps in combination with solar collectors requires comprising knowledge of the heat Pump behavior under non-standard conditions. Especially higher temperatures and varying flow rates in comparison to non-solar systems have to be taken into account. Furthermore the dynamic behavior becomes more important. At ISFH, steady-state and dynamic tests of a typical brine/water heat Pump have been carried out in order to analyze its behavior under varying operation conditions. It has been shown, that rising source temperatures do only significantly increase the coefficient of performance (COP), if the source temperature is below 10–20 °C, depending on the temperature lift between source and sink. The flow rate, which has been varied both on the source and the sink side, only showed a minor influence on the exergetic efficiency. Additionally a heat Pump Model for TRNSYS has been validated under non-standard conditions. The results are assessed by means of TRNSYS simulations.
Xiaosong Zhang - One of the best experts on this subject based on the ideXlab platform.
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long term coupled simulation for ground source heat Pump and underground heat exchangers
Energy and Buildings, 2015Co-Authors: Kefeng Dong, Jinyong Wang, Xiaosong ZhangAbstract:Abstract A long-term dynamic coupling Model based on variable heat line source Model, one-dimensional heat transfer Model and a steady-state heat Pump Model was built in this paper to simulate the performance of ground source heat Pump (GSHP) system and soil temperature variation around the underground heat exchangers (UHEs). The Model describes the real-time interaction between the performance of heat Pump system and soil temperature variation in the long term. Simulation agreed well with the measured data. The soil temperature variation and heat Pump system performance in 15 years in Changzhou was simulated. The results showed that the soil temperature will increase by 2.56–3.00 °C after 15 years, and cooling water inlet temperature will be 36 °C after 9 years, therefore the coefficient of performance (COP) of GSHP will decrease in summer, while increase in winter. It also prove that the temperature of the soil around borehole will rise with the operation of GSHP in the middle and downstream of Yangtze River, the more drilling hole amount the more obvious trend.
Leok Poh Chua - One of the best experts on this subject based on the ideXlab platform.
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validation of an axial flow blood Pump computational fluid dynamics results using particle image velocimetry
Artificial Organs, 2012Co-Authors: Leok Poh Chua, Xikun WangAbstract:A magnetically suspended axial flow blood Pump is studied experimentally in this article. The Pump casing enclosed a three-blade straightener, a two-blade impeller shrouded by a permanent magnet-embedded cylinder, and a three-blade diffuser. The internal flow fields were simulated earlier using computational fluid dynamics (CFD), and the Pump characteristic curves were determined. The simulation results showed that the internal flow field was basically streamlined, except the diffuser region. Particle image velocimetry (PIV) measurement of the 1:1 Pump Model was conducted to validate the CFD result. In order to ensure the optical access, an acrylic prototype was fabricated with the impeller driven by a servomotor instead, as the magnet is opaque. In addition to the transparent Model, the blood analog fluid with the refractive index close to that of acrylic was used to avoid refraction. According to the CFD results, the axial flow blood Pump could generate adequate pressure head at the rotating speed of 9500rpm and flow rate of 5L/min, and the same flow condition was applied during the PIV measurement. Through the comparisons, it was found that the experimental results were close to those obtained by CFD and had thus validated the CFD Model, which could complement the limitation of the measurement in assessing the more detailed flow fields of the axial flow Pump.
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the flow patterns within the impeller passages of a centrifugal blood Pump Model
Medical Engineering & Physics, 2000Co-Authors: W K Chan, Leok Poh ChuaAbstract:Abstract The effects of impeller geometry on the performance of a centrifugal blood Pump Model [the MSCBP design of Akamatsu and Tsukiya (The Seventh Asian Congress of Fluid Mechanics (1997), 7–10) at a 1:1 scale] have been investigated both experimentally and computationally. Four impeller designs were tested for Pump hydraulic performance at the operating point (i.e. 2000 rpm), using blood analog as the working fluid. Each impeller has seven blades with different configurations including the radial straight blade and backward swept blade designs. The results show that both designs can achieve a stable head of about 100 mm Hg at the operating point. Subsequent investigations involved the visualization of the relative flow field within the impeller passages via the image de-rotation system coupled with a 2.5 W argon ion laser. Flow structures in all sectors of each impeller were examined and discussed. To further quantify the possible effects of blade geometry to thrombus formation and hemolysis, computational fluid dynamics (CFD) was used to simulate a simplified two-dimensional blade-to-blade flow analysis so as to estimate the shear stress levels. The results indicate that the stress levels found within the blade passages are generally below the threshold level of 150 N/m 2 for extensive erythrocyte damage to occur. There are some localized regions near the leading edge of the blades where the stress levels are 60% above the threshold level. However, given such a short residence time for the fluid particles to go through these high shear stress regions, their effects appear to be insignificant.
