Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2013, 29 (5)   Published: 25 October 2013
Wavy structures in compressible mixing layers
Jun Chen, Xiao-Tian Shi, Tie-Jin Wang, Zhen-Su She

Semi-periodic structures namely inclined wavy structures (IWS) are experimentally observed in compressible mixing layers at two convective Mach numbers (Mc = 0.11 and 0.47). Flow structures are visualized by the laserinduced planar laser Mie scattering (PLMS) technique. Two methods are developed to investigate the spatial distribution and geometry of IWS: (1) the dominant mode extraction (DME) method, to extract the dominant modes of IWS from the streamwise gray-level fluc...

Investigation of scale effect for the computation of turbulent flow around a circular cylinder
Lin Lin, Yan-Ying Wang

In order to investigate the scale effect of turbulent flow around a circular cylinder, two similarity numbers (criteria) based on turbulent kinetic and dissipation rates associated with the fluctuation characteristics of turbulence wake are deduced by analyzing the Reynolds averaged Navier- Stokes equations (RANS). The RNG k-ε models and finite volume method are used to solve the governing equations and the second-order implicit time and upwind space discretization a...

The effect of the couple stress parameter and Prandtl number on the transient natural convection flow over a vertical cylinder
H. P. Rani, G. Janardhana Reddy, Chang Nyung Kim

An analysis is performed to study transient free convective boundary layer flow of a couple stress fluid over a vertical cylinder, in the absence of body couples. The solution of the time-dependent non-linear and coupled governing equations is carried out with the aid of an unconditionally stable Crank-Nicolson type of numerical scheme. Numerical results for the steady-state velocity, temperature as well as the time histories of the skin-friction coefficient and Nusselt number are presented g...

Spark-generated bubble collapse near or inside a circular aperture and the ensuing vortex ring and droplet formation
Abdolrahman Dadvand, Mazyar Dawoodian, Boo Cheong Khoo, Reza Esmaily

This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillating near an aperture the initial free surface of the water was set at the bottom surface of the plate. The effects of aperture size and bubblefree surface distance on the bubble behavior as well as on the ensuing droplet dynamics are investigated. It was found that the direction o...

Unsteady heat and mass transfer in MHD flow over an oscillatory stretching surface with Soret and Dufour effects
Lian-Cun Zheng, Xin Jin, Xin-Xin Zhang, Jun-Hong Zhang

In this paper, we study the unsteady coupled heat and mass transfer of two-dimensional MHD fluid over a moving oscillatory stretching surface with Soret and Dufour effects. Viscous dissipation effects are adopted in the energy equation. A uniform magnetic field is applied vertically to the flow direction. The governing equations are reduced to non-linear coupled partial differential equations and solved by means of homotopy analysis method (HAM). The effects of some physical parameters such a...

Rate effect and coupled evolution of atomic motions and potential landscapes
Pan Xiao, Jun Wang, Rong Yang, Fu-Jiu Ke, Meng-Fen Xia, Yi-Long Bai

Since rate effect of materials plays a key role in impact engineering, the microscopic mechanism of rate effect is investigated at molecular level in this paper. The results show that rate effect on the strength of atomic system is closely related to the coupled evolution of atomic motions and potential landscapes. Accordingly, it becomes possible to develop a new algorithm of molecular simulation, which could properly and efficiently demonstrate strain rate effect under a wide range of loadi...

Research papers
A micromechanical model for effective conductivity in granular electrode structures
Julia Ott, Benjamin Völker, Yixiang Gan, Robert M. McMeeking, Marc Kamlah

Optimization of composition and microstructure is important to enhance performance of solid oxide fuel cells (SOFC) and lithium-ion batteries (LIB). For this, the porous electrode structures of both SOFC and LIB are modeled as a binary mixture of electronic and ionic conducting particles to estimate effective transport properties. Particle packings of 10 000 spherical, binary sized and randomly positioned particles are created numerically and densified considering the different manufacturing ...

Study on spline wavelet finite-element method in multi-scale analysis for foundation
Qiang Xu, Jian-Yun Chen, Jing Li, Gang Xu, Hong-Yuan Yue

A new finite element method (FEM) of B-spline wavelet on the interval (BSWI) is proposed. Through analyzing the scaling functions of BSWI in one dimension, the basic formula for 2D FEM of BSWI is deduced. The 2D FEM of 7 nodes and 10 nodes are constructed based on the basic formula. Using these proposed elements, the multiscale numerical model for foundation subjected to harmonic periodic load, the foundation model excited by external and internal dynamic load are studied. The results show th...

A new integration algorithm for finite deformation of thermo-elasto-viscoplastic single crystals
Dan Zhao, Yi-Guo Zhu, Ping Hu, Wan-Xi Zhang

An algorithmfor integrating the constitutive equations in thermal framework is presented, in which the plastic deformation gradient is chosen as the integration variable. Compared with the classic algorithm, a key feature of this new approach is that it can describe the finite deformation of crystals under thermal conditions. The obtained plastic deformation gradient contains not only plastic deformation but also thermal effects. The governing equation for the plastic deformation gradient is ...

Dynamic response to a moving load of a Timoshenko beam resting on a nonlinear viscoelastic foundation
Yan Yang, Hu Ding, Li-Qun Chen

The present paper investigates the dynamic response of finite Timoshenko beams resting on a sixparameter foundation subjected to a moving load. It is for the first time that the Galerkin method and its convergence are studied for the response of a Timoshenko beam supported by a nonlinear foundation. The nonlinear Pasternak foundation is assumed to be cubic. Therefore, the effects of the shear deformable beams and the shear deformation of foundations are considered at the same time. The Galerk...

Geometric nonlinear formulation for thermal-rigid-flexible coupling system
Wei Fan, Jin-Yang Liu

This paper develops geometric nonlinear hybrid formulation for flexible multibody system with large deformation considering thermal effect. Different from the conventional formulation, the heat flux is the function of the rotational angle and the elastic deformation, therefore, the coupling among the temperature, the large overall motion and the elastic deformation should be taken into account. Firstly, based on nonlinear strain-displacement relationship, variational dynamic equations and hea...

Dynamics of cantilever plates and its hybrid vibration control
Bo Ni, Chao Hu

Applying Lagrange-Germain's theory of elastic thin plates and Hamiltonian formulation, the dynamics of cantilever plates and the problem of its vibration control are studied, and a general solution is finally given. Based on Hamiltonian and Lagrangian density function, we can obtain the flexural wave equation of the plate and the relationship between the transverse and the longitudinal eigenvalues. Based on eigenfunction expansion, dispersion equations of propagation mode of cantilever plates...

Attitude control of a rigid spacecraft with one variable-speed control moment gyro
Hai-Chao Gui, Lei Jin, Shi-Jie Xu

Nonlinear controllability and attitude stabilization are studied for the underactuated nonholonomic dynamics of a rigid spacecraft with one variable-speed control moment gyro (VSCMG), which supplies only two internal torques. Nonlinear controllability theory is used to show that the dynamics are locally controllable from the equilibrium point and thus can be asymptotically stabilized to the equilibrium point via time-invariant piecewise continuous feedback laws or time-periodic continuous fee...

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