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We report on third order optical nonlinear experimental characterization using Z-scan method through focal shift measurements of a converging lens. The sample is fixed in front of a lens and is illuminated by a collimated beam. The shift of the geometrical focus in the nonlinear regime using input Gaussian beams is related to the nonlinear induced dephasing owing to a simple linear relation. Numerical calculations based on the Helmholtz wave equation are performed. Good agreement is obtained between experimental and theoretical results. 相似文献
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Almost all evaluations of convection schemes reported in the literature are conducted using simple problems on uniform orthogonal grids; thus, having limited contribution when solving industrial computational fluid dynamics (CFD), where the grids are usually non‐orthogonal with distortions. Herein, several convection schemes are assessed in uniform and distorted non‐orthogonal grids with emphasis on industrial applications. Linear and nonlinear (TVD) convection schemes are assessed on analytical benchmarks in both uniform and distorted grids. To evaluate the performance of the schemes, four error metrics are used: dissipation, phase and L1 errors, and the schemes' effective order of accuracy. Qualitative and quantitative deterioration of these error metrics as a function of the grid distortion metrics are investigated, and rigorous verifications are performed. Recommendations for effective use of the convection schemes based on the range of grid aspect ratio (AR), expansion ratio (ER) and skewness (Q) are included. A ship hydrodynamics case is studied, involving a Reynolds averaged Navier–Stokes simulation of a bare‐hull KVLCC2 tanker using linear and nonlinear convection schemes coupled with isotropic and anisotropic Reynolds‐stress (ARS) turbulence models using CFDShip‐Iowa v4. Predictions of local velocities and turbulent quantities from the midships to the nominal wake plane are compared with experimental fluid dynamics (EFD), and rigorous verification and validation analyses for integral forces and moments are performed for 0° and 12° drift angles. Best predictions are observed when coupling a second‐order TVD scheme with the anisotropic turbulence model. Further improvements are observed in terms of prediction of the vortical structures for 30° drift when using TVD2S‐ARS coupled with DES. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Shuzhen Fan Qingpu Wang Shutao Li Shuanghong Ding Fufang Su 《Optics Communications》2006,266(2):620-626
A method of more precise determination of the focal length of equivalent thermal lens (TL) is presented in this paper. The method is based on the diffraction theory of aberrations. By numerically calculating the optical path difference (OPD) distribution and the Strehl ratio, the focal lengths for “top-hat” pumping and Gaussian pumping are obtained and the equations for the focal lengths are presented by curve fitting. Also the equations for average pump radii are presented. The experiment on a fiber-coupled LD pumped Nd:YAG laser is carried out. The experimental results verify the validity of the method. 相似文献
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对于一般情形,给出焦点量和鞍点量计算与约化的Maple算法,从而统一了焦点量和鞍点量的计算,并给出细焦点与细鞍点的变换,利用变换推导了焦点量和鞍点量的关系. 相似文献
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The problem of heat transfer in the wall region of a turbulent boundary layer has been investigated. The resonant triad in
the theory of hydrodynamic stability was used to obtain the velocity field induced by the coherent structures in the wall
region of the turbulent boundary layer, while the small scale turbulence was represented by a simple model. By such a new
approach of modeling, the 3-D temperature field is calculated, the mean temperature profile in the wall region and the Nusselt
number characterizing the heat flux, which was found to be in good agreement with the experimental observations are obtained.
The instantaneous temperature field had streaky structures, thus offering a mechanism for their generation found in numerical
simulations.
Project supported by the National Natural Science Foundation of China (Grant No. 19132011). 相似文献
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本文建立了用顶空气相色谱法测定反应堆冷却水中微量氢的方法,在气液体积比为1:2,平衡温度为60℃,平衡时间为40min的气液相平衡条件下H2的检测下限为0.02mL/LH2O2。对于H2浓度高于0.1mL/LH2O的冷却水水样,相对标准偏差小于5.0%,适用于反应堆水样的分析。 相似文献
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