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研究了光子晶体加载矩形谐振腔,针对传统光子晶体加载无法完全抑制模式竞争的问题,提出了特性阻抗和介质加载方法进行改进,完全实现了谐振腔的高次模式的单模工作,为抑制高次模式工作的谐振腔中模式竞争的问题提供了一种新方法.在此基础之上,采用解析方法以及高频仿真软件HFSS,设计了一个采用TM530高次模式工作的传统光子晶体加载的谐振腔,进一步采用了该新方法对其进行改进,并深入分析了采用这种方法抑制模式竞争的物理原因.计算结果表明,新方法能有效抑制模式竞争,实现谐振腔的高次工作模式的单模工作.
关键词:
光子晶体
谐振腔
模式竞争
特性阻抗 相似文献
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对作者所提出的无干涉条纹直接电场重构测量飞秒脉冲的振幅和相位的新方法作出进一步理论分析,并通过实验测量说明该方法的优越性.该方法克服了传统的SPIDER方法的弊病,能得到一组无干涉条纹的图像,排除传统方法必须使用傅里叶变换滤波消除干涉条纹而引进的系统误差,使得该方法能够采用较简便设备且能较准确测量飞秒脉冲强度轮廓和相位.最后给出同一条件下新方法和传统SPIDER方法分别重构的脉冲强度自相关曲线与实验测量结果的比较,以说明新方法的有效性和优越性. 相似文献
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对作者所提出的无干涉条纹直接电场重构测量飞秒脉冲的振幅和相位的新方法作出进一步理论分析,并通过实验测量说明该方法的优越性.该方法克服了传统的SPIDER方法的弊病,能得到一组无干涉条纹的图像,排除传统方法必须使用傅里叶变换滤波消除干涉条纹而引进的系统误差,使得该方法能够采用较简便设备且能较准确测量飞秒脉冲强度轮廓和相位.最后给出同一条件下新方法和传统SPIDER方法分别重构的脉冲强度自相关曲线与实验测量结果的比较,以说明新方法的有效性和优越性.
关键词:
光谱相位相干直接电场重构法
飞秒脉冲测量
超快信息光学 相似文献
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随机变量在积分球设计中的应用 总被引:3,自引:1,他引:2
本文主要介绍了随机变量在设计积分球中的应用方法,着重讨论了构造的物理模型和数学模型.通过计算机的模拟实验表明这种设计积分球的新方法能够克服传统解析方法的缺点,有一定的实用价值. 相似文献
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基于压力边界条件开展了微尺度低速流动DSMC方法的研究, 定义了两个无量纲参数作为微尺度DSMC方法下网格尺寸与时间步长的约束条件, 通过微尺度Poiseuille流进行了方法的验证与比较, 获得了网格尺寸与时间步长的一般原则。在此基础上, 对变截面的单孔和双孔模型的微通道气体流动进行DSMC模拟, 结果表明, 通道几何形状对微尺度气体流动具有显著影响, 孔口后由于通道收缩, 产生压降, 导致气流加速, 并在孔口下游拐角处发生分离; 双孔口模型的流动结构与单孔口模型相似, 且在相同压差情况下, 经双孔口后的气体流速低于经单孔口后的气体流速; 随着入口压力的增加, 经过孔口压缩后的速度越大, 分离区尺寸也越大。 相似文献
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M.A. Gallis J.R. Torczynski D.J. Rader G.A. Bird 《Journal of computational physics》2009,228(12):4532-4548
The convergence rate of a new direct simulation Monte Carlo (DSMC) method, termed “sophisticated DSMC”, is investigated for one-dimensional Fourier flow. An argon-like hard-sphere gas at 273.15 K and 266.644 Pa is confined between two parallel, fully accommodating walls 1 mm apart that have unequal temperatures. The simulations are performed using a one-dimensional implementation of the sophisticated DSMC algorithm. In harmony with previous work, the primary convergence metric studied is the ratio of the DSMC-calculated thermal conductivity to its corresponding infinite-approximation Chapman–Enskog theoretical value. As discretization errors are reduced, the sophisticated DSMC algorithm is shown to approach the theoretical values to high precision. The convergence behavior of sophisticated DSMC is compared to that of original DSMC. The convergence of the new algorithm in a three-dimensional implementation is also characterized. Implementations using transient adaptive sub-cells and virtual sub-cells are compared. The new algorithm is shown to significantly reduce the computational resources required for a DSMC simulation to achieve a particular level of accuracy, thus improving the efficiency of the method by a factor of 2. 相似文献
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The information preservation (IP) method has been successfully applied to various nonequilibrium gas flows. Comparing with the direct simulation Monte Carlo (DSMC) method, the IP method dramatically reduces the statistical scatter by preserving collective information of simulation molecules. In this paper, a multiple temperature model is proposed to extend the IP method to strongly translational nonequilibrium gas flows. The governing equations for the IP quantities have been derived from the Boltzmann equation based on an assumption that each simulation molecule represents a Gaussian distribution function with a second-order temperature tensor. According to the governing equations, the implementation of IP method is divided into three steps: molecular movement, molecular collision, and update step. With a reasonable multiple temperature collision model and the flux splitting method in the update step, the transport of IP quantities can be accurately modeled. We apply the IP method with the multiple temperature model to shear-driven Couette flow, external force-driven Poiseuille flow and thermal creep flow, respectively. In the former two cases, the separation of different temperature components is clearly observed in the transition regime, and the velocity, temperature and pressure distributions are also well captured. The thermal creep flow, resulting from the presence of temperature gradients along boundary walls, is properly simulated. All of the IP results compare well with the corresponding DSMC results, whereas the IP method uses much smaller sampling sizes than the DSMC method. This paper shows that the IP method with the multiple temperature model is an accurate and efficient tool to simulate strongly translational nonequilibrium gas flows. 相似文献
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A new discrete velocity scheme for solving the Boltzmann equation is described. Directly solving the Boltzmann equation is computationally expensive because, in addition to working in physical space, the nonlinear collision integral must also be evaluated in a velocity space. Collisions between each point in velocity space with all other points in velocity space must be considered in order to compute the collision integral most accurately, but this is expensive. The computational costs in the present method are reduced by randomly sampling a set of collision partners for each point in velocity space analogous to the Direct Simulation Monte Carlo (DSMC) method. The present method has been applied to a traveling 1D shock wave. The jump conditions across the shock wave match the Rankine–Hugoniot jump conditions. The internal shock wave structure was compared to DSMC solutions, and good agreement was found for Mach numbers ranging from 1.2 to 10. Since a coarse velocity discretization is required for efficient calculation, the effects of different velocity grid resolutions are examined. Additionally, the new scheme’s performance is compared to DSMC and it was found that upstream of the shock wave the new scheme performed nearly an order of magnitude faster than DSMC for the same upstream noise. The noise levels are comparable for the same computational effort downstream of the shock wave. 相似文献
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A multiscale hybrid method for coupling the direct simulation Monte Carlo (DSMC) method to the nonequilibrium molecular dynamics (NEMD) method is introduced. The method addresses Knudsen layer type gas flows within a few mean free paths of an interface or about an object with dimensions of the order of a few mean free paths. It employs the NEMD method to resolve nanoscale phenomena closest to the interface along with coupled DSMC simulation of the remainder of the Knudsen layer. The hybrid DSMC/NEMD method is a particle based algorithm without a buffer zone. It incorporates a new, modified generalized soft sphere (MGSS) molecular collision model to improve the poor computational efficiency of the traditional generalized soft sphere GSS model and to achieve DSMC compatibility with Lennard-Jones NEMD molecular interactions. An equilibrium gas, a Fourier thermal flow, and an oscillatory Couette flow, are simulated to validate the method. The method shows good agreement with Maxwell–Boltzmann theory for the equilibrium system, Chapman–Enskog theory for Fourier flow, and pure DSMC simulations for oscillatory Couette flow. Speedup in CPU time of the hybrid solver is benchmarked against a pure NEMD solver baseline for different system sizes and solver domain partitions. Finally, the hybrid method is applied to investigate interaction of argon gas with solid surface molecules in a parametric study of the influence of wetting effects and solid molecular mass on energy transfer and thermal accommodation coefficients. It is determined that wetting effect strength and solid molecular mass have a significant impact on the energy transfer between gas and solid phases and thermal accommodation coefficient. 相似文献
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The direct simulation Monte Carlo (DSMC) method for population balance modeling is capable of retaining the history of each simulation particle and is thus able to deal with multivariate properties in a simple and straightforward manner. As opposed to conventional DSMC approaches that track equally weighted simulation particles, a differentially weighted Monte Carlo method is extended to simulate two-component coagulation processes and is thereby able to simulate the micromixing of the components. A new feature of the method for this bivariate population balance modeling is that it is possible to specify how the simulation particles are distributed over the compositional axis. This allows us to obtain information about particles in those regions of the size and composition distribution functions where the non-weighted MC methods place insufficient simulation particles to obtain an inaccurate solution. The new feature results in lower statistical noise for simulating two-component coagulation, which is validated by using two-component coagulation cases for which analytical solutions exist (a discrete process with sum kernel for initial monodisperse populations and a process with constant kernel for initial polydisperse populations). 相似文献
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Ye. A. Bondar A. A. Shevyrin Y. S. Chen A. N. Shumakova A. V. Kashkovsky M. S. Ivanov 《Thermophysics and Aeromechanics》2013,20(5):553-564
A novel approach to modeling high-temperature nonequilibrium dissociation in air at a level of molecular collisions is proposed. Information on the energy dependence of the specific reaction cross sections, which is necessary for such modeling, is determined numerically from available macroscopic information on the dependence of the reaction rate constant on translational and vibrational temperatures. The results of Direct Simulation Monte Carlo (DSMC) computations show that the proposed model yields a correct reaction rate in vibrational-translational nonequilibrium. The use of the new model in DSMC computations of high-altitude aerothermodynamics results in obtaining a noticeably different flow structure and a higher heat flux, as compared to that predicted by standard DSMC models (such as the total collision energy model). 相似文献
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Before a hybrid scheme can be developed combining the direct simulation Monte Carlo (DSMC) method and a Navier–Stokes (NS) representation, one must have access to compatible kinetic-split fluxes from the NS portion of the hybrid scheme. The kinetic theory basis is given for the development of the required fluxes from the Chapman–Enskog velocity distribution function for a simple gas; and these are then extended to a polyatomic gas by use of the Eucken approximation. The derived fluxes are then used to implement boundary conditions at solid surfaces that are based on concepts associated with kinetic theory and the DSMC method. This approach is shown to lead to temperature slip and velocity slip as a natural outcome of the new formulation, a requirement for use in the near-continuum regime where DSMC and NS must be joined. Several different flows, for which solid boundaries are not present, are computed using the derived fluxes, together with a second-order finite-volume scheme, and the results are shown to agree well with several established numerical schemes for the NS equations. 相似文献