Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2011, 27 (3)   Published: 18 June 2011
On resolution to Wu's conjecture on Cauchy function’s exterior singularities
Th.Y. Wu
This is a series of studies on Wu's conjecture and on its resolution to be presented herein. Both are devoted to expound all the comprehensive properties of Cauchy's function $f (z)$ $ (z=x+{\rm i}y)$ and its integral $J[f (z)]\equiv (2\pi {\rm i})^{-1}\doint_C f (t)(t-z)^{-1}{\rm d}t $ taken along the unit circle as contour $C$, inside which (the open domain ${\cal D^+}) f (z)$ is regular but has singularities distributed in open domain ${\cal D^-}$ outside $C$. Resolution is given to the inver...
Research Papers
Numerical simulations of compressible mixing layers with a discontinuous Galerkin method
X.T. Shi J. Chen W.T. Bi C.W. Shu Z.S. She
Discontinuous Galerkin (DG) method is known to have several advantages for flow simulations, in particular, in flexible accuracy management and adaptability to mesh refinement. In the present work, the DG method is developed for numerical simulations of both temporally and spatially developing mixing layers. For the temporally developing mixing layer, both the instantaneous flow field and time evolution of momentum thickness agree very well with the previous results. Shocklets are observed at hi...
Shear flow induced vibrations of long slender cylinders with a wake oscillator model
F. Ge W. Lu L. Wang Y.S. Hong
A time domain model is presented to study the vibrations of long slender cylinders placed in shear flow. Long slender cylinders such as risers and tension legs are widely used in the field of ocean engineering. They are subjected to vortex-induced vibrations (VIV) when placed within a transverse incident flow. A three dimensional model coupled with wake oscillators is formulated to describe the response of the slender cylinder in cross-flow and in-line directions. The wake oscillators are distri...
Comparisons and applications of numerical simulation methods for predicting aerodynamic heating around complex configurations
J.L. Luo H.L. Kang J. Li W.Y. Dai
Numerical simulation methods of aerodynamic heating were compared by considering the influence of numerical schemes and turbulence models, and attempting to investigate the applicability of numerical simulation methods on predicting heat flux in engineering applications. For some typical cases provided with detailed experimental data, four spatial schemes and four turbulence models were adopted to calculate surface heat flux. By analyzing and comparing, some influencing regularities of numerical...
Video-based measurement and data analysis of traffic flow on urban expressways
X.Q. Zheng Z. Wu M.M. Guo Z.X. Lin Y.Y. Zhang
A new video-based measurement is proposed to collect and investigate traffic flow parameters. The output of the measurement is velocity-headway distance data pairs. Because density can be directly acquired by the reciprocal of headway distance, the data pairs have the advantage of better simultaneity than those from common detectors. By now, over 33000 pairs of data have been collected from two road sections in the cities of Shanghai and Zhengzhou. Through analyzing the video files recording tra...
Exact solution for the unsteady flow of a semi-infinite micropolar fluid
H.H. Sherief M.S. Faltas E. A.Ashmawy
The unsteady motion of an incompressible micropolar fluid filling a half-space bounded by a horizontal infinite plate that started to move suddenly is considered. Laplace transform techniques are used. The solution in the Laplace transform domain is obtained by using a direct approach. The inverse Laplace transforms are obtained in an exact manner using the complex inversion formula of the transform together with contour integration techniques. The solution in the case of classical viscous fluid...
Steady thermocapillary-buoyant convection in a shallow annular pool. Part 1: Single layer fluid
Y.R. Li S.C. Wang C.M. Wu
This paper examines the steady thermocapillary-buoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios, which is defined as the ratio of the layer thickness to the gap width. The flow domain is divided into the core region away from the cylinder walls and two end regions near each cylinder wall. Asymptotic solutions are obtained...
Penny-shaped interfacial crack between dissimilar magnetoelectroelastic layers
Y.S. Li Z.H. Xu W.J. Feng
A penny-shaped interfacial crack between dissimilar magnetoelectroelastic layers subjected to magnetoelectromechanical loads is investigated, where the magnetoelectrically impermeable crack surface condition is adopted. By using Hankel transform technique, the mixed boundary value problem is firstly reduced to a system of singular integral equations, which are further reduced to a system of algebraic equations. The field intensity factors and energy release rate are finally derived. Numerical re...
Modeling oxidation damage of continuous fiber reinforced ceramic matrix composites
C.P. Yang G.Q. Jiao B. Wang
For fiber reinforced ceramic matrix composites (CMCs), oxidation of the constituents is a very important damage type for high temperature applications. During the oxidizing process, the pyrolytic carbon interphase gradually recesses from the crack site in the axial direction of the fiber into the interior of the material. Carbon fiber usually presents notch-like or local neck-shrink oxidation phenomenon, causing strength degradation. But, the reason for SiC fiber degradation is the flaw growth m...
Effects of thermophoresis particle deposition and of the thermal conductivity in a porous plate with dissipative heat and mass transfer
Joaquin Zueco O.A. Bég L.M. López-Ochoa
Network simulation method (NSM) is used to solve the laminar heat and mass transfer of an electrically-conducting, heat generating/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule heating problem. The governing partial differential equations are non-dimensionalized and transformed into a system of nonlinear ordinary differential similarity equations, in a single independent variable, $\eta $. The resulting coupled, nonlinear equations are solved under app...
Test analysis of detection of damage to a complicated spatial model structure
L.H. Xu Z.X. Li J.R. Qian
A two-stage damage detection approach is proposed and experimentally demonstrated on a complicated spatial model structure with a limited number of measurements. In the experiment, five known damage patterns, including 3 brace damage cases and 2 joint damage cases, were simulated by removing braces and weakening beam--column connections in the structure. The limited acceleration response data generated by hammer impact were used for system identification, and modal parameters were extracted by u...
Development of X-FEM methodology and study on mixed-mode crack propagation
Z. Zhuang B.B. Cheng
The extended finite element method (X-FEM) is a novel numerical methodology with a great potential for using in multi-scale computation and multi-phase coupling problems. The algorithm is discussed and a program is developed based on X-FEM for simulating mixed-mode crack propagation. The maximum circumferential stress criterion and interaction integral are deduced. Some numerical results are compared with the experimental data to prove the capability and efficiency of the algorithm and the progr...
Bi-variable damage model for fatigue life prediction of metal components
M. Zhang Q.C. Meng X. Zhang W.P. Hu
Based on the theory of continuum damage mechanics, a bi-variable damage mechanics model is developed, which, according to thermodynamics, is accessible to derivation of damage driving force, damage evolution equation and damage evolution criteria. Furthermore, damage evolution equations of time rate are established by the generalized Drucker's postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations, and the fatigue life prediction met...
Approximate and numerical analysis of nonlinear forced vibration of axially moving viscoelastic beams
H. Ding L.Q. Chen
Steady-state periodical response is investigated for an axially moving viscoelastic beam with hybrid supports via approximate analysis with numerical confirmation. It is assumed that the excitation is spatially uniform and temporally harmonic. The transverse motion of axially moving beams is governed by a nonlinear partial-differential equation and a nonlinear integro-partial-differential equation. The material time derivative is used in the viscoelastic constitutive relation. The method of mult...
Stabilization of coordinated motion for underwater vehicles
F. Wu Z.Y. Geng
This paper presents a coordinating and stabilizing control law for a group of underwater vehicles with unstable dynamics. The coordinating law is derived from a potential that only depends on the relative configuration of the underwater vehicles. Being coordinated, the group behaves like one mechanical system with symmetry, and we focus on stabilizing a family of coordinated motions, called relative equilibria. The stabilizing law is derived using energy shaping to stabilize the relative equilib...
Size effect on the static behavior of electrostatically actuated micobeams
L. Yin Q. Qian L. Wang
We present a new analytical model for electrostatically actuated microbeams to explore the size effect by using the modified couple stress theory and the minimum total potential energy principle. A material length scale parameter is introduced to represent the size-dependent characteristics of microbeams. This model also accounts for the nonlinearities associated with the mid-plane stretching force and the electrostatical force. Numerical analysis for microbeams with clamped-clamped and cantilev...
Powell dynamic identification of displacement parameters of indeterminate thin-walled curve box based on FCSE theory
J. Zhang C.W. Zhou J.S. Zhuo
The FCSE controlling equation of pinned thin-walled curve box was derived and the indeterminate problem of continuous thin-walled curve box with diaphragm was solved based on flexibility theory. With Bayesian statistical theory, dynamic Bayesian error function of displacement parameters of indeterminate curve box was founded. The corresponding formulas of dynamic Bayesian expectation and variance were deduced. Combined with one-dimensional Fibonacci automatic search scheme of optimal step size, ...
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