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排序方式: 共有316条查询结果,搜索用时 296 毫秒
1.
We consider the isothermal flow through a cylindrical flat chamber, a model of some particular heat exchanger, for which LDV measurements and a numerical simulation have been performed. Experimental results show the establishment of an important vortex zone, the secondary flow extending all along the chamber radius. This observation leads to an expected significant increase of the fluid mixing. Results issued from the numerical simulation appear to be in close agreement with experimental data. Nevertheless, the k–ε model used here must be improved to obtain a better approach near the vortex centre. To cite this article: S. Petitot et al., C. R. Mecanique 330 (2002) 593–599. 相似文献
2.
This paper presents an application in the automotive industry where a combination of electronic speckle-pattern interferometry and laser doppler velocimetry were used at a critical stage in the design process of an internal combustion engine. Combined deformation and surface relief measurements were used to study the phase and amplitude of deformation of a vibrating engine. The relief data was combined with the interferometer geometry and used to geometrically correct the deformation data, in an effort to improve accuracy. The measurements allowed rapid identification and quantification of design weaknesses, particularly those causing undesirable resonances. This led to a significant reduction in the design time and lowering of costs, when compared with existing design optimisation methods. 相似文献
3.
M.A.C. Potenza M.D. Alaimo D. Pescini D. Magatti F. Ferri M. Giglio 《Optics and Lasers in Engineering》2006,44(7):722
We show that the time evolution of near-field scattering speckles, originated by a fluid suspension of particles, provides information about the velocity field in the fluid. This information can be extracted from a statistical analysis of speckle fields taken at different times, either by measuring their cross-correlation function or by recovering the power spectrum corresponding to the difference between the two speckle fields. Experimental data are in accordance to the expected behaviors. The results are independent of the scatterer's size, allowing one to exploit the technique also with sub-wavelength tracking particles. 相似文献
4.
The necessity of odor sensing has been increasing from environmental and health standpoints. Here, we propose the novel concept of a small device which can select odor molecules based on electrostatic spraying. For high selectivity of the target gas or odor, we conducted computational fluid dynamics coupled with an electrostatic field, as well as measurements by particle image velocimetry and anemometry. The computational model successfully reproduced characteristic features of ionic wind. Different trajectories of charged particles were computationally obtained owing to their electrical mobility. The results imply that different materials might be separated by the arrangement of the collecting electrode. 相似文献
5.
Investigating microfluidic flow profiles is of interest in the microfluidics field for the determination of various characteristics of a lab-on-a-chip system. Microparticle tracking velocimetry uses computational methods upon recording video footage of microfluidic flow to ultimately visualize motion within a microfluidic system across all frames of a video. Current methods are computationally expensive or require extensive instrumentation. A computational method suited to microparticle tracking applications is the robust Kanade–Lucas–Tomasi (KLT) feature-tracking algorithm. This work explores a microparticle tracking velocimetry program using the KLT feature-tracking algorithm. The developed program is demonstrated using pressure-driven and EOF and compared with the respective mathematical fluid flow models. An electrostatics analysis of EOF conditions is performed in the development of the mathematical using a Poisson's Equation solver. This analysis is used to quantify the zeta potential of the electroosmotic system. Overall, the KLT feature-tracking algorithm presented in this work proved to be highly reliable and computationally efficient for investigations of pressure-driven and EOF in a microfluidic system. 相似文献
6.
The investigation of the bidirectional coupling between a fluid flow and a structure motion is a growing branch of research in science and industry. Applications of the so-called fluid–structure interactions (FSI) are widespread. To improve coupled numerical FSI simulations, generic experimental benchmark studies of the fluid and the structure are necessary. In this work, the coupling of a vortex-induced periodic deformation of a flexible structure mounted behind a rigid cylinder and a fully turbulent water flow performed at a Reynolds number of Re=30 470 is experimentally investigated with a planar particle image velocimetry (PIV) and a volumetric three-component velocimetry (V3V) system. To determine the structure displacements a multiple-point laser triangulation sensor is used. The three-dimensional fluid velocity results show shedding vortices behind the structure, which reaches the second swiveling mode with a frequency of about 11.2 Hz corresponding to a Strouhal number of St=0.177. Providing phase-averaged flow and structure measurements precise experimental data for coupled computational fluid dynamics (CFD) and computational structure dynamics (CSD) validations are available for this new benchmark case denoted FSI-PfS-2a. The test case possesses four main advantages: (i) the geometry is rather simple; (ii) kinematically, the rotation of the front cylinder is avoided; (iii) the boundary conditions are well defined; (iv) nevertheless, the resulting flow features and structure displacements are challenging from the computational point of view. In addition to the flow field and displacement data a PIV-based force calculation method is used to estimate the lift and drag coefficients of the moving structure. 相似文献
7.
Stick-slip flow of high density polyethylene in a transparent slit die investigated by laser Doppler velocimetry 总被引:1,自引:0,他引:1
The oscillating flow instability of a molten linear high-density polyethylene is carefully studied using a single screw extruder equipped with a transparent slit die. Experiments are performed using laser Doppler velocimetry in order to obtain the local velocities field across the entire die width. At low flow rate, the extrusion is stable and steady state velocity profiles are obtained. During the instability, the velocity oscillates between two steady state limits, suggesting a periodic stick-slip transition mechanism. At high flow rate, the flow is mainly characterized by a pronounced wall slip. We show that wall slip occurs all along the die land. An investigation of the slip flow conditions shows that wall slip is not homogeneous in a cross section of the slit die, and that pure plug flow occurs only for very high flow rates. A numerical computation of the profile assuming wall slip boundary conditions is done to obtain the true local wall slip velocity. It confirms that slip velocities are of the same order of magnitude as those measured with a capillary rheometer. 相似文献
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10.
Ming Qian Zhonghua Shen Jian Lu Xiaowu Ni Qiang Li Yimin Xuan 《Optics and Lasers in Engineering》2008,46(6):461-468
Our recent work revealed that speckles can be formed when nanofluids containing a proper volume fraction of nanoparticles are illuminated by a monochromatic laser beam [Qian M, Liu J, Yan M-S, Shen Z-H, Lu J, Ni XW, et al. Investigation on utilizing laser speckle velocimetry to measure the velocities of nanoparticles in nanofluids. Opt Express 2006; 14: 7559–66]. In this paper, two different physical models are established to figure out the speckle-formation mechanism. The photon–nanoparticle-collision model emphasizes the random collisions between photons and nanoparticles, and Monte Carlo method is used to simulate how the incident photons move in the vessel containing nanofluids. However, in the electric-dipole model, each illuminated nanoparticle becomes an electric dipole and sends out scattering lights, and the coherent addition of the scattering lights from nanoparticles is numerically calculated. Finally, from the numerical results, the speckle-formation mechanism is figured out. 相似文献