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用概率型模型测量格子气的粘性系数 总被引:1,自引:0,他引:1
在Boltzmann假设下,提出一种概率型格子气模型,并通过对平面Poseuille流的模拟,用数值方式“测量”了格子气体的粘性系数。数值结果同理论上得到的解析粘性系数进行了定量比较,得到了非常符合的结果。 相似文献
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本文将物理参数直接识别法用于均匀分布系统等效离散模型的物理参数识别,数值模拟结果表明,识别得到的离散模型的动力特性较好地接近分布系统的动力特性,离散系统物理参数识别的有关结论对分布系统仍然成立,数值模拟与实验结果还表明,均匀分布系统时域响应测量点应等距离布置。 相似文献
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二维振荡叶栅非定常粘性流动数值模拟 总被引:9,自引:0,他引:9
采用显式四步Runge-Kutta格式,结合Baldwon-Lomax紊流模型求解Navier-Stokes方程,借助运动网格技术,完成了对二维振荡叶栅非定常粘性流动的数值模拟。为了加速求解过程,引入了变系数隐式残差光顺方法,取得了较好效果。数值结果与已公布的数据有很好的一致性。 相似文献
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利用NND有限差分格式,发展了一种新的完全隐式的有限体积数值方法,以求解与时间相关的N-S方程.对通过单元体界面的无粘流和粘性流通量均作隐式处理.对绕流钝锥体和不同攻角的气动辅助实验飞行器的高超声速粘性流和化学反应流获得了定常数值解.对流加热率和流场电子密度的计算值与实验数据进行了比较,符合较好,证实了本方法的精确性. 相似文献
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发展了一种研究叶轮机内动、静叶间的相互作用的新方法———扰动涡方法,它利用全三维的定常解为基础解,并由此给出非定常扰动场的初始解.为计算叶片对扰动场的响应过程,采用拉格朗日方法追踪扰动涡团的对流流动过程,用确定性涡方法来描述流体的粘性扩散过程.发展了代数湍流模型(Baldwin Lomax湍流模型)在尾迹中的应用方法,克服了其它数值方法中无法准确捕捉尾迹中心线的运动轨迹,以及计算出的边界层外的湍流涡粘性系数偏大的缺陷.利用该方法计算轴流叶轮机内由于动、静叶间的相互作用而引起的非定常流动过程,与实验的对照表明,模拟结果与实验数据吻合得相当好,从而说明本文发展的方法是可信的,为更直观地描述尾迹等非定常因素的流动及叶轮机内的掺混问题提供依据. 相似文献
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为了揭示发射装药破碎引起的膛炸现象,急需进行相应装药结构下发射装药挤压破碎数值模拟研究。以硝胺花边十九孔发射药为研究对象,基于离散单元法建立了发射装药挤压破碎模拟系统,同时进行了发射装药动态挤压破碎实验,通过数值模拟与实验获得了不同冲击载荷下的破碎发射装药和挤压应力;分别对获得的破碎发射装药进行了密闭爆发器数值模拟和实验。结果表明:模拟与实验获得的发射装药挤压应力时间历程、密闭爆发器压力时间曲线和起始动态活度比的一致性较好,实验验证了发射装药挤压破碎模拟系统的有效性及合理性。该模拟系统具有重大工程应用价值,为高能发射装药冲击破碎过程和发射装药发射安全性研究奠定了基础。 相似文献
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本文用有限差分法对直管内的湍流旋流进行了数值模拟。计算中采用Boussinesq湍流涡粘性假设的基本思想和K-ε双方程模型来求解雷诺应力各分量。为了反映旋流中湍流转输的非均匀性和各向异性特征,对雷诺应力各分量及与之相主尖的各湍流粘性系数分别进行计算。计算结果表明该模型能较好地反映直管内湍流旋流的流动结构。 相似文献
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The instantaneous squeeze-film force between a heat exchanger tube and a support plate is studied. Based on a two-dimensional rectangular plate model, a short-sleeve squeeze-film model for arbitrary tube motion is developed. The instantaneous squeeze-film force is expressed in normal and tangential directions. The normal squeeze-film force consists of four nonlinear terms, the viscous, unsteady inertia, convective inertia and centripetal inertia terms. Three nonlinear terms, the viscous, unsteady inertia and Coriolis inertia terms, make up the tangential squeeze-film force. An experimental apparatus was developed in order to evaluate the theoretical models against measurements of a finite length squeeze film. A modified model based on the experimental data is obtained where the viscous terms for both directions are multiplied by the instantaneous Reynolds number. All the inertia terms are multiplied by constant coefficients. The modified model is in good agreement with most experimental cases for unsymmetrical linear motion, approximate circular motion and elliptical motion. The form of the modified model is suitable for predicting instantaneous squeeze-film forces in the simulation of heat exchanger tube vibration. Further work using different sized components and fluid properties is required in order to finalize coefficient values. 相似文献
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An experimental investigation of electrorheological squeeze film dynamics is presented for constant applied voltage and low strain amplitude. Both broadband random and sinusoidal motion are examined to explain complex film dynamics. Spectral results indicate a primarily elastic response with slip at the plate boundaries. By examining the evolution of an effective shear modulus over time, sinusoidal results show that slip at the boundaries is due to a solvent layer which may be modelled as a separate variable thickness squeeze film. 相似文献
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A form of squeeze film apparatus was recently described in which the movement of one plate towards the other was simulated by the continuous volume generation of liquid over the plate area. The liquid exuded from a large number of holes in the lower plate surface and formed a “continous flow” version of squeeze film apparatus with no moving parts [1]. A later paper gave derivations of equations from which squeeze film load bearing capacity could be evaluated, taking into account viscous, inertial and normal stress effects in the liquid film [2].In order to find the total load in a squeeze film system, it was necessary to obtain the relationship between the first normal stress difference and shear rate for the liquid in use, using an experimental method. At high shear rates, the jet thrust method provided these data [3,4] and from them the load bearing capacity of squeeze films of hot, polymer-thickened oil were predicted [2].A more complete test of the method is possible with a highly elastic liquid because considerable load enhancement due to extra stress is present at moderate deformation rates in squeeze film systems [1,5,6,7]. Thus a 0.1 per cent aqueous polyacrylamide solution gives well-defined load enhancement and (quite independently) the jet thrust method gives the relationship between normal stress and shear rate from which predictions of load enhancement may be made. Furthermore, convergent nozzles may be used in the jet thrust apparatus [3] to measure the stress development in an elastic liquid which is being simulateneously sheared and stretched, a situation which more closely resembles the squeeze film case than that of steady shear. 相似文献
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Consideration is given to the flow of an inelastic ‘power-law’ liquid in a continuous flow squeeze film. This simulates the flow in a conventional squeeze film by continuously injecting fluid into the narrow gap between two plates through the lower plate (Oliver et al. [6]). To zero order in the usual lubrication approximation the results are identical with those for the conventional squeeze film. To first order, useful corrections to the normal force due to the effects of inertia are obtained. 相似文献
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《Fluid Dynamics Research》2007,39(8):616-631
On the basis of the Stokes micro-continuum theory together with the averaged inertia principle, the combined effects of non-Newtonian couple stresses and convective fluid inertia forces on the squeeze film motion between a long cylinder and an infinite plate are presented. A closed-form solution has been derived for squeeze film characteristics including the film pressure, the load capacity and the response time. Comparing with the Newtonian-lubricant non-inertia case, the combined effects of couple stresses and convective inertia forces provide an increase in the film pressure, the load capacity and the response time. In addition, the quantitative effects of couple stresses and convective inertia forces are more pronounced for cylinder–plate system operating at a larger couple stress parameter and film Reynolds number, as well as a smaller squeeze film height. To guide the use of the present study, a numerical example is also illustrated for engineers when considering both the effects of non-Newtonian couple stresses and fluid convective inertia forces. 相似文献
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轻敲模式下探针从远离到间歇性接触样品表面,是一个连续的能量耗散过程.针对该连续过程的能量耗散机理研究仅零星存在于各个文献之中,对于连续过程中各个阶段的能量耗散机理也没有一个系统的解释和实验验证.本文提出了新的位移激励下原子力显微镜探针-样品系统简化模型并得到了一维振子系统等效阻尼的计算方法,并通过该方法计算了探针在远离样品表面时的空气黏性阻尼和靠近样品时的空气压膜阻尼,分析了探针从远离样品到间歇性接触样品表面这一过程中的环境耗散机理变化,得到了原子力显微镜系统理论品质因数与探针工作位置的关系曲线;在此基础上设计了轻敲模式下的微悬臂梁扫频实验,得到了系统实验品质因数与探针工作位置的关系曲线,进而验证了理论模型的准确性. 本文通过对轻敲模式下AFM环境耗散机理进行理论分析和实验验证,希望可以对轻敲模式下AFM动力学特性及其阻尼作用机理有更近一步的认识,同时对微纳米机电系统 (MEMS/NEMS) 能量耗散机理的研究提供理论参考和实验方法. 相似文献
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轻敲模式下 AFM 动力学模型及能量耗散机理研究 总被引:1,自引:0,他引:1
轻敲模式下探针从远离到间歇性接触样品表面,是一个连续的能量耗散过程.针对该连续过程的能量耗散机理研究仅零星存在于各个文献之中,对于连续过程中各个阶段的能量耗散机理也没有一个系统的解释和实验验证.本文提出了新的位移激励下原子力显微镜探针-样品系统简化模型并得到了一维振子系统等效阻尼的计算方法,并通过该方法计算了探针在远离样品表面时的空气黏性阻尼和靠近样品时的空气压膜阻尼,分析了探针从远离样品到间歇性接触样品表面这一过程中的环境耗散机理变化,得到了原子力显微镜系统理论品质因数与探针工作位置的关系曲线;在此基础上设计了轻敲模式下的微悬臂梁扫频实验,得到了系统实验品质因数与探针工作位置的关系曲线,进而验证了理论模型的准确性. 本文通过对轻敲模式下AFM环境耗散机理进行理论分析和实验验证,希望可以对轻敲模式下AFM动力学特性及其阻尼作用机理有更近一步的认识,同时对微纳米机电系统 (MEMS/NEMS) 能量耗散机理的研究提供理论参考和实验方法. 相似文献
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《Journal of Fluids and Structures》2001,15(1):151-169
Using three approximation methods, nonlinear models have been derived for short and long cylindrical squeeze films with arbitrary inner cylinder motions. Elliptical and parabolic velocity profiles are employed in the derivation in order to determine the effects of the choice of velocity profile. The only differences in the final squeeze film equations, due to the three approximation methods and the two velocity profiles, are in the four constant coefficients. Each term in the squeeze film equations is a nonlinear function of cylinder position. Comparing the present nonlinear expressions with existing models for short cylindrical squeeze films shows that the force terms are either exactly the same or have the same trends with instantaneous eccentricity values. For long cylindrical squeeze films, the present expressions have some force terms which are essentially the same as in other studies, while other force terms show variations with position which are very different from a previously published study. 相似文献
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This article presents a theoretical, numerical and experimental study of resonant structures undergoing very large amplitude vibrations. The purpose of this work is to validate a model for the damping due to the action of the air on a structure’s single-mode response in the steady-state. Experiments are performed on cantilever beams and beam assemblies of various sizes, from centimetric to micrometric, under harmonic base excitation. Dimensionless linear and nonlinear modal damping coefficients are simultaneously identified by means of frequency-domain identification techniques. These measurements demonstrate the pertinence of the presented model. 相似文献