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The effect of gas phase velocity fluctuations on single droplet burning is investigated numerically. The main objective of
this study is to understand the effect of gas phase turbulence on nitric oxide formation in single droplet flames. Since the
interaction of gas phase velocity fluctuations with droplet burning is of sequential character, a separate investigation of
droplet momentum coupling and droplet burning is performed. Momentum coupling controls droplet relaxation against changes
of the gas phase velocity along the droplet trajectory and, thereby, determines to what extend gas phase velocity fluctuations
translate into droplet slip velocity fluctuations. This coupling effect acts as a high pass filter with a cutoff frequency
determined by the droplet Reynolds number and diameter. In the simulation of single droplet burning detailed models for chemical
reaction, diffusive species transport and evaporation are used. A significant effect of slip velocity fluctuations on the
mean values of NO formation rate is observed. The effect of slip velocity fluctuations on the mean NO formation rate is frequency
dependent. The frequency response of the droplet flame is similar to that of a low pass filter. The droplet flame time scale
characterizing the response to slip velocity fluctuations is found to correlate with chemical time scales. This time scale
is not affected by droplet diameter. 相似文献
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相对湿度对材料表面粘附力影响的研究 总被引:1,自引:0,他引:1
利用自制微摩擦及粘附力测试装置考察了在微载荷条件下,相对湿度对Si(100)材料表面粘附力的影响,分析了在大气环境中水分子的毛细作用力和范德华力对粘附力的贡献,并以BET吸附模型为基础推导出考虑湿度影响的粘附力计算公式.结果表明:在微载荷条件下,相对湿度对材料表面的粘附力影响十分显著,随着相对湿度升高粘附力增加,特别是相对湿度RH在40%~80%之间时,粘附力变化最为显著;当相对湿度RH小于20%时,范德华力大于水的毛细作用力且占主导地位;当相对湿度RH大于20%后,水分子的毛细作用力不断增加,同时范德华力因水膜的存在而降低,水的毛细作用力占主导地位. 相似文献
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The three-dimensional theoretical solution of a concentrated normal force acting on the free surface of a coated material has been deduced by applying the reflection method. It is found that all stress functions defined in the local coordinate systems with their origins placed at each mirror point can be deduced from the fundamental solution of a concentrated normal force acting on the free surface of a semi-infinite homogeneous medium. The structure of the elastic solution has been illustrated by numerical analysis. It is found that only the stress functions corresponding to the first few mirror points are influential. It is also found that the effect of material combination on the stress field shall be described by three parameters, the two Dundurs' parameters and one additional parameter. 相似文献
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We study a longitudinal constant-speed impact against the end of a linearly elastic semi-infinite thread following the curvature of a fixed solid. The analytical solution found takes into account waves multiply reflected from the contact surface and the impact point. 相似文献
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基于介观模型的多组分伪势格子Boltzmann方法,模拟了倾斜壁面浸润性梯度驱动液滴的运动过程,研究了壁面浸润性梯度、壁面倾斜角度对液滴运动过程的影响.结果表明,对于一定倾斜角度的壁面,当壁面上浸润性梯度足够大时,液滴能够克服重力的作用实现“爬坡”;液滴在运动过程中,其前进及后退接触角与当地静态接触角间存在差值;增大壁面浸润性梯度时,液滴能够获得更快的加速,并且前进及后退接触角与当地静态接触角之间的差值也随之增大;增大壁面倾斜角度时,液滴的运动受到阻碍,前进及后退接触角与当地静态接触角的差值小幅减小. 相似文献
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D. A. Gadzhiev A. M. Gaifullin 《Journal of Applied Mechanics and Technical Physics》2018,59(2):212-218
A numerical solution is found for the problem of evolution of two oppositely rotating vortices in a viscous incompressible fluid near a solid surface. The mechanism of vortex dissipation is determined. The trajectory of vortex motion is constructed. 相似文献
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实现黏附可控是解决微/纳机械产品黏附失效问题和发展先进黏附材料及新型微操作/微装配技术等的有效途径. 基于该研究背景,针对干燥不带电系统,对近年来发展的几类黏附调控方法进行了综述,从表面改形、材料改性及外场控制三方面介绍了织构、涂层/薄膜和复合材料、速度、温度、外力和磁场在黏附调控方面的研究进展,分析和总结了各类方法的黏附调控机理、关键影响因素和特点,并指出了应用领域,介绍了多手段复合调控黏附方法的最新研究成果. 最后,探讨了当前黏附调控方面存在的问题和未来可能的发展方向. 相似文献
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A. N. Cherepanov V. N. Popov O. P. Solonenko 《Journal of Applied Mechanics and Technical Physics》2006,47(1):22-26
A mathematical model is developed for nonequilibrium volume crystallization of a metallic droplet modified by mechanically
activated refractory nanoparticles upon its impact onto a solid substrate. The model takes into account the kinetics of heterogeneous
and homogeneous nucleation during melt cooling. Specific features of crystallization of a liquid metal (nickel) depending
on the concentration and size of modifying particles are examined numerically. A typical feature of the process considered
is the maximum supercooling of the melt, whose magnitude depends on the particle size and cooling intensity. Homogeneous nucleation
is almost absent. The calculated radii of droplets solidified on the substrate are in good agreement with available experimental
data.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 29–34, January–February, 2006. 相似文献
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Surface microstructures of solid materials play a significant role in various wetting and dewetting phenomena. In the present paper, the effect of micro- and nano-structures of a substrate surface on the morphology and evolution of liquid droplets and thin films is examined. The governing equations satisfied by droplets and films on a sinusoidal surface are derived by considering van der Waals force, surface tension, gravity and hydrostatic pressure. The morphologies of both liquid droplets and thin films are numerically simulated under various characteristic sizes of roughness. It is found that the droplet shapes show a significant dependence upon the characteristic sizes of substrate microstructures. A thin liquid film on a hydrophilic substrate may have a horizontal surface or replicate the substrate morphology, depending on the wavelength of roughness.The project supported by the National Natural Science Foundation of China (10525210, 10121202) and the Ministry of Education of China.The English text was polished by Keren Wang. 相似文献
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R. Sh. Gimadiev 《Mechanics of Solids》2017,52(5):564-574
The results of mathematical simulation of a solid velocity damping by a soft skeleton fabric shell filled with air on impact on a hard surface are given. The equations of motion of a falling body and of the loading dynamics of membrane shells and the reinforcement rings in the fabric shell are considered together. Themathematical model and the numerical algorithm for solving the spatial problem of the dynamics of inflation of a shell with reinforcement rings are explicitly realized by the finite difference method. The boundary conditions are posed with regard to the contact of the shell elements in compression near the ring belts. The results of numerical experiments considering the interaction of the falling body with the deformable skeleton shell are discussed. The parameters influencing the process of the body braking on impact on a surface are determined. 相似文献
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在交错网格中用MAC方法求解二维不可压N S方程 ,对圆截面液柱与固壁、液面斜撞击问题进行了数值模拟 ,得到了自由面随时间演化的图像。主要考察了 :(1)固壁和液面 ;(2 )牛顿、非牛顿流体 ;(3)碰撞入射角 ;(4 )Bingham流体近似本构式中参数q0 、K对计算结果的影响。结果表明 :液柱与液面碰撞形成的自由面更复杂。碰撞初期 ,Bingham流体和水的自由面相似 ;但碰撞后期 ,Bingham流体的自由面相对简单。对液柱与液面碰撞自由面的影响较大。本文条件下 ,当K 2 0时 ,K对自由面的影响不大 ;当q0 增大时 ,自由面变得相对简单。 相似文献
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单微吸管测量细胞切向粘附力方法的研究 总被引:1,自引:0,他引:1
本文对单微吸管测量细胞切向粘附力的方法进行简要的力学分析,结果表明该方法不失为一种简单易行的切向粘附力测量方法,有助于研究个体细胞与不同基底材料之间的粘附性能,以及不同药物、粘附分子对细胞切向粘附力的影响,扩大了微管吸吮技术的应用范围,并对单微吸管细胞切向粘附力测量方法的测量左范围进行了讨论。通过对人成骨细胞切向粘附力的测量,结果表明该方法可满足细胞生物力学实验的要求。 相似文献
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The physical mechanisms of development of hydrodynamic instability during high-velocity impact are analyzed analytically and using numerical simulation. A new mechanism of development of instability based on the assumption of the existence of initial perturbations on the surfaces of the colliding plates is proposed. The progressive displacement of the maximum of the specific surface mixed mass from the shortwave to the longwave spectrum range and the self-similarity of the variation of the interface are established. 相似文献
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K. Arakawa T. Mada H. Komatsu T. Shimizu M. Satou K. Takehara G. Etoh 《Experimental Mechanics》2009,49(4):471-477
The normal impact between a golf ball and a rigid steel target was studied to examine ball deformation and the contact force
during the impact. Using high-speed video images, the normal and tangential compression ratios of the ball were measured to
analyze the ball deformation quantitatively. In addition, the inbound and rebound ball velocities, contact time, and coefficient
of restitution were determined as basic parameters of the impact. As the inbound ball velocity increased, the maximum normal
compression ratio increased while the maximum tangential compression ratio, contact time and coefficient of restitution decreased.
The ball center displacements during the impact were measured to determine the ball center velocity and acceleration, and
the contact force was calculated by the product of the mass and acceleration. The contact force increased almost linearly
with the inbound ball velocity, and its relationship agreed well quantitatively with the results from a load-cell, and also
agreed well qualitatively with Hertz contact theory. 相似文献
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A complex numerical and experimental method is proposed for studying 3D dynamics of a bubble contacting with a surface in the presence of an acoustic field. The numerical approach is based on the boundary element method for potential flows, which is most efficient for solving the problems in a 3D formulation. The use of heterogeneous computer architectures consisting of central graphic processors and becoming more and more popular makes it possible to increase the scale of the problem and sufficiently reduce the calculation time. The mesh destabilization problems are solved using a spherical filter. To describe the contact line dynamics, a semi-empirical law of motion is used. The experimental method is based on high-speed recording and optical microscopy. An air bubble contacts with the inner surface of an experimental cell made from acrylic glass and filled with distilled water. The acoustic field in the cell generated by a disk-shaped acoustic radiator is measured using a hydrophone. The behavior of the bubble contacting with a hydrophillic surface is considered for the cases of a fixed or moving contact line. The shape and volume oscillations of the bubble are investigated. The results of numerical simulations agree qualitatively with the experimental data. 相似文献