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Joël Delville 《Applied Scientific Research》1994,53(3-4):263-281
Experiments are performed in an incompressible plane turbulent mixing layer, using various hot wire rake configurations. From these experiments, the Proper Orthogonal Decomposition is applied for kernels where the space-time correlation tensor is evaluated over different spatial meshes and velocity components configurations. The resulting decompositions are then discussed in terms of characterization of the organization of the flow for various scalar or vectorial approaches of the POD. An incrtial range law is evidenced. The instantaneous contribution of the first modes of the POD to the organization of the flow is analyzed. A dynamical behavior for the organization of the flow is observed from the correlation between the first two modes contribution. 相似文献
3.
用微芯片化学反应器实现酶催化化学发光测定葡萄糖的研究 总被引:2,自引:0,他引:2
徐溢 《高等学校化学学报》2003,24(1):49-51
葡萄糖是临床化学诊断以及食品分析中重要的检测项目 ,最常用的测定方法是采用葡萄糖氧化酶(GOD)催化葡萄糖与氧分子间反应 ,生成葡萄糖酸和过氧化氢 [1] ,而对过氧化氢的检测则可采用过氧化酶 (POD)催化鲁米诺的化学发光反应进行 [2 ] .FIA对整个过程的实现是十分有效的方式 ,但由于多采用固定化酶反应器 [3~ 5] 使其在制备及分析上较复杂且费用高 .由 Manz等[6] 提出的微型全分析系统(μ- TAS)在针对不同体系的微量分析及在线监测上均具有突出的优越性 .本文使用的含微混合器的微芯片化学反应器采用μ- TAS设计思想 ,建立了化学发… 相似文献
4.
Model order reduction of the two‐dimensional Burgers equation is investigated. The mathematical formulation of POD/discrete empirical interpolation method (DEIM)‐reduced order model (ROM) is derived based on the Galerkin projection and DEIM from the existing high fidelity‐implicit finite‐difference full model. For validation, we numerically compared the POD ROM, POD/DEIM, and the full model in two cases of Re = 100 and Re = 1000, respectively. We found that the POD/DEIM ROM leads to a speed‐up of CPU time by a factor of O(10). The computational stability of POD/DEIM ROM is maintained by means of a careful selection of POD modes and the DEIM interpolation points. The solution of POD/DEIM in the case of Re = 1000 has an accuracy with error O(10?3) versus O(10?4) in the case of Re = 100 when compared with the high fidelity model. For this turbulent flow, a closure model consisting of a Tikhonov regularization is carried out in order to recover the missing information and is developed to account for the small‐scale dissipation effect of the truncated POD modes. It is shown that the computational results of this calibrated ROM exhibit considerable agreement with the high fidelity model, which implies the efficiency of the closure model used. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
5.
The variation of amplitude and transit time of the diffracted signal from the crack-tip in complex geometry components and their resulting effect on the probability of detection (POD) and probability of sizing (POS) was studied. The diffracted signal amplitude has been evaluated from the standard expressions for diffraction coefficient, spatial attenuation and the transit time from the respective mathematical models for both vertical and inclined cracks. The same parameters namely the signal amplitude and the transit time have been measured through experiments conducted on simulated test specimens. It has been observed that the analytical and experimental results compare well with each other. Based on this result the trend and shape (width of the transition zone) of the POD/POS curves can be predicted. 相似文献
6.
Non‐intrusive reduced‐order modeling for multiphase porous media flows using Smolyak sparse grids 下载免费PDF全文
Dunhui Xiao Zhi Lin Fangxin Fang Christopher C. Pain Ionel M. Navon Pablo Salinas Ann Muggeridge 《国际流体数值方法杂志》2017,83(2):205-219
In this article, we describe a non‐intrusive reduction method for porous media multiphase flows using Smolyak sparse grids. This is the first attempt at applying such an non‐intrusive reduced‐order modelling (NIROM) based on Smolyak sparse grids to porous media multiphase flows. The advantage of this NIROM for porous media multiphase flows resides in that its non‐intrusiveness, which means it does not require modifications to the source code of full model. Another novelty is that it uses Smolyak sparse grids to construct a set of hypersurfaces representing the reduced‐porous media multiphase problem. This NIROM is implemented under the framework of an unstructured mesh control volume finite element multiphase model. Numerical examples show that the NIROM accuracy relative to the high‐fidelity model is maintained, whilst the computational cost is reduced by several orders of magnitude. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
In this paper, the cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating flow in a Venturi reactor are investigated experimentally under different cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale cavitation flow structure, is applied to investigate the choked cavitating flow dynamics. The POD results show that two mechanisms, re-entrant jet flow mechanism and shock wave mechanism, govern the shedding and collapse of cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various cavitation regions induced by the choked cavitating flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for cavitation applications such as water treatment. 相似文献
8.
ZHOU ShanShi HU XiaoGong WU Bin LIU Li QU WeiJing GUO Rui HE Feng CAO YueLing Wu XiaoLi ZHU LingFeng SHI Xin & TAN HongLi Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai China Graduate University of Chinese Academy of Sciences Beijing Beijing Global Information Application Development Center Beijing 《中国科学:物理学 力学 天文学(英文版)》2011,(6)
Aiming at regional services,the space segment of COMPASS (Phase I) satellite navigation system is a constellation of Geostationary Earth Orbit (GEO),Inclined Geostationary Earth Orbit (IGSO) and Medium Earth Orbit (MEO) satellites.Precise orbit determination (POD) for the satellites is limited by the geographic distribution of regional tracking stations.Independent time synchronization (TS) system is developed to supplement the regional tracking network,and satellite clock errors and orbit data may be obtai... 相似文献
9.
10.
The baseline and forced flow around a bluff body with semi-elliptical D-shape was investigated by solving the 2D Navier–Stokes
equations at low Reynolds numbers. A D-shape rather than the canonic circular-cylinder was selected due to the fixed separation
points in the latter, enabling to study a pure wake rather than boundary-layer control. The correlation between Strouhal and
Reynolds numbers, the mean drag, the lift and drag oscillations vs. the Reynolds number and wake structure were investigated
and compared to experimental and numerical data. Effects of open-loop forcing, resulting from the influence of zero-mass-flux
actuators located at the fixed separation points, were studied at a Reynolds number of 150. Fluidic rather than body motion
or volume forcing was selected due to applicability considerations. The motivation for the study was to quantify the changes
in the flow field features, as captured by Proper Orthogonal Decomposition (POD) analysis, due to open-loop forcing, inside
and outside the “lock-in” regime. This is done in order to evaluate the suitability of low-order-models based on POD modes
of this changing flow field, for future feed-back flow control studies. The evolution of the natural and the excited vortices
in the Kármán wake were also investigated. The formation and convection regions of the vortex evolution were documented. It
was found that the forcing causes an earlier detachment of the vortices from the boundary-layers, but does not affect their
circulation or convection speeds. The results of the POD analysis of the near-wake flow show that the influence of the bluff
body shape (“D”-shaped versus circular cylinder) on the baseline POD wake modes is small. It was found that the eigenfunctions
(mode-shapes) of the POD velocity modes are less sensitive to slot excitation than the vorticity modes. As a result of the
open-loop excitation, two types of mode-shape-change were observed: a mode can be exchanged with a lower-energy mode or shifted
to a low energy level. In the latter case, the most energetic mode becomes the “actuator” mode. The evolution of one-slot
excitation on still fluid (“Synthetic jet”) was studied and compared to published data and to “actuator” modes with external
flow present. Based on the current findings, it is hypothesized that the cross-flow velocity POD modes are suitable for feedback
control of wake flow using periodic excitation, due to their low sensitivity to the excitation as compared to the streamwise
velocity or vorticity modes. 相似文献