Acta Mechanica Sinica
     Acta Mechanica Sinica
  Acta Mechanica Sinica--2012, 28 (1)   Published: 25 February 2012
Special papers on biomechanics
Recent advances in theoretical models of respiratory mechanics Hot!
Bo Huo, Rui-Rong Fu

As an important branch of biomedical engineering, respiratory mechanics helps to understand the physiology of the respiratory system and provides fundamental data for developing such clinical technologies as ventilators. To solve different clinical problems, researchers have developed numerous models at various scales that describe biological and mechanical properties of the respiratory system. During the past decade, benefiting from the continuous accumulation of clinical data and the dramat...

Characteristics of compressible flow of supercritical kerosene
Feng-Quan Zhong, Xue-Jun Fan, JingWang, Gong Yu, Jian-Guo Li
In this paper, compressible flow of aviation kerosene at supercritical conditions has been studied both numerically and experimentally. The thermophysical properties of supercritical kerosene are calculated using a 10-species surrogate based on the principle of extended corresponding states (ECS). Isentropic acceleration of supercritical kerosene to subsonic and supersonic speeds has been analyzed numerically. It has been found that the isentropic relationships of supercritical kerosene are sign...
Unsteady aerodynamics modeling for flight dynamics application
Qing Wang, Kai-Feng He, Wei-Qi Qian, Tian-Jiao Zhang, Yan-Qing Cheng, Kai-Yuan Wu
In view of engineering application, it is practicable to decompose the aerodynamics into three components: the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due to unsteady separated and vortical flow. The first and the second components can be presented in conventional forms, while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration, the mathematical models...
The axisymmetric long-wave interfacial stability of core-annular flow of power-law fluid with surfactant
Xue-Wei Sun, Jie Peng, Ke-Qin Zhu
The long wave stability of core-annular flow of power-law fluids with an axial pressure gradient is investigated at low Reynolds number. The interface between the two fluids is populated with an insoluble surfactant. The analytic solution for the growth rate of perturbation is obtained with long wave approximation. We are mainly concerned with the effects of shear-thinning/thickening property and interfacial surfactant on the flow stability. The results show that the influence of shear-thinning/...
Boundary layer flow over a moving surface in a nanofluid with suction or injection
Norfifah Bachok, Anuar Ishak, Ioan Pop
An analysis is performed to study the heat transfer characteristics of steady two-dimensional boundary layer flow past a moving permeable flat plate in a nanofluid. The effects of uniform suction and injection on the flow field and heat transfer characteristics are numerically studied by using an implicit finite difference method. It is found that dual solutions exist when the plate and the free stream move in the opposite directions. The results indicate that suction delays the boundary layer s...
Natural convection flow of a couple stress fluid between two vertical parallel plates with Hall and ion-slip effects
D. Srinivasacharya, K. Kaladhar
The Hall and ion-slip effects on fully developed electrically conducting couple stress fluid flow between vertical parallel plates in the presence of a temperature dependent heat source are investigated. The governing non-linear partial differential equations are transformed into a system of ordinary differential equations using similarity transformations. The resulting equations are then solved using the homotopy analysis method (HAM). The effects of the magnetic parameter, Hall parameter, ion-...
A boundary element method for the simulation of non-spherical bubbles and their interactions near a free surface
Zhang-Rui Li, Lei Sun, Zhi Zong, Jing Dong
The basic principle and numerical technique for simulating two three-dimensional bubbles near a free surface are studied in detail by using boundary element method. The singularities of influence coefficient matrix are eliminated using coordinate transformation and so-called 4π rule. The solid angle for the open surface is treated in direct method based on its definition. Several kinds of configurations for the bubbles and free surface have been investigated. The pressure contours du...
Numerical study on three-dimensional flow field of continuously rotating detonation in a toroidal chamber
Xu-Dong Zhang, Bao-Chun Fan, Ming-Yue Gui, Zhen-Hua Pan, Gang Dong
Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive...
Flame quenching process in cavity based on model scramjet combustor
Yu Pan, Jing Lei, Jian-Han Liang, Wei-Dong Liu, Zhen-Guo Wang
The flame quenching process in combustors was observed by high speed camera and Schlieren system, at the inflow conditions of Ma = 2.64, T0 = 1483K, P0 = 1.65MPa, T = 724K and P = 76.3kPa. Changing process of the flame and shock structure in the combustor was clearly observed. The results revealed that the precombustion shock disappeared accompanied with the process in which the flame was blown out and withdrawed from the mainflo...
Shock tube study of n-decane ignition at low pressures
Xiao-Fei Nie, Ping Li, Chang-Hua Zhang, Wei Xie, Cong-Shan Li, Xiang-Yuan Li
Ignition delay times for n-decane/O2/Ar mixtures were measured behind reflected shock waves using endwall pressure and CH* emission measurements in a heated shock tube. The initial postshock conditions cover pressures of 0.09-0.26MPa, temperatures of 1227-1536 K, and oxygen mole fractions of 3.9%-20.7% with an equivalence ratio of 1.0. The correlation formula of ignition delay dependence on pressure, temperature, and oxygen mole fraction was obtained. The current data are i...
Axisymmetric compressive buckling of multi-walled carbon nanotubes under different boundary conditions
Cheng-Qi Sun, Kai-Xin Liu, You-Shi Hong
The paper studies the axisymmetric compressive buckling behavior of multi-walled carbon nanotubes (MWNTs) under different boundary conditions based on continuum mechanics model. A buckling condition is derived for determining the critical buckling load and associated buckling mode of MWNTs, and numerical results are worked out for MWNTs with different aspect ratios under fixed and simply supported boundary conditions. It is shown that the critical buckling load of MWNTs is insensitive to boundar...
C1 natural element method for strain gradient linear elasticity and its application to microstructures
Zhi-Feng Nie, Shen-Jie Zhou, Ru-Jun Han, Lin-Jing Xiao, KaiWang
C1 natural element method (C1 NEM) is applied to strain gradient linear elasticity, and size effects on microstructures are analyzed. The shape functions in C1 NEM are built upon the natural neighbor interpolation (NNI), with interpolation realized to nodal function and nodal gradient values, so that the essential boundary conditions (EBCs) can be imposed directly in a Galerkin scheme for partial differential equations (PDEs). In the pr...
Nonlinearity analysis of piezoelectric micromachined ultrasonic transducers based on couple stress theory
Xin Kang, Fu-Jun Yang, Xiao-Yuan He
This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer (PMUT) actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is e...
Fatigue reliability based on residual strength model with hybrid uncertain parameters
Jun Wang, Zhi-Ping Qiu
The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model. By solving the non-probabilistic setbased reliability problem and analyzing the reliability with randomness, the fatigue reliability with hybrid parameters can be obtained. The presented hybrid model can adequately consider all uncertainties affecting the fatigue reliability with hybrid uncertain parameters. A comparison among the presented hybrid model, non-probabili...
Assessment of structural damage using natural frequency changes
Shu-Qing Wang, Hua-Jun Li
The present paper develops a new method for damage localization and severity estimation based on the employment of modal strain energy. This method is able to determine the damage locations and estimate their severities, requiring only the information about the changes of a few lower natural frequencies. First, a damage quantification method is formulated and iterative approach is adopted for determining the damage extent. Then a damage localization algorithm is proposed, in which a damage indic...
Hybrid graded element model for transient heat conduction in functionally graded materials
Lei-Lei Cao, Qing-Hua Qin, Ning Zhao
This paper presents a hybrid graded element model for the transient heat conduction problem in functionally graded materials (FGMs). First, a Laplace transform approach is used to handle the time variable. Then, a fundamental solution in Laplace space for FGMs is constructed. Next, a hybrid graded element is formulated based on the obtained fundamental solution and a frame field. As a result, the graded properties of FGMs are naturally reflected by using the fundamental solution to interpolate t...
A new method of quality improvement for quadrilateral mesh based on small polygon reconnection
Jian-Fei Liu, Shu-Li Sun, Yong-Qiang Chen
In this paper, a new method of topological cleanup for quadrilateral mesh is presented. The method first selects a patch of mesh around an irregular node. It then seeks the best connection of the selected patch according to its irregular valence using a new topological operation: small polygon reconnection (SPR). By replacing the original patch with an optimal one that has less irregular valence, mesh quality can be improved. Three applications based on the proposed approach are enumerated: (1) ...
Ultrasonic beam steering using Neumann boundary condition in multiplysics
Zhao-Guo Qiu, Bin Wu, Cun-Fu He
The traditional one-dimensional ultrasonic beam steering has time delay and is thus a complicated problem. A numerical model of ultrasonic beam steering using Neumann boundary condition in multiplysics is presented in the present paper. This model is based on the discrete wave number method that has been proved theoretically to satisfy the continuous conditions. The propagating angle of novel model is a function of the distance instead of the time domain. The propagating wave fronts at desired a...
3D contaminant migration model with consolidation dependent transport coefficients
Lu Huang, Cheng-Gang Zhao, Yan Liu, Guo-Qing Cai
Soil consolidation would induce variations of its transport coefficients such as hydraulic conductivity and diffusion coefficient. This paper presents a study of the influence of barrier consolidation on transport coefficients, and a 3D transport model based on mixture theory is proposed for describing the liners that involve circular defects in the geomembrane. The elastoplastic ALPHA model is revised by using the spatially mobilized plane (SMP) criterion for simulating the deformation of the s...
On the limitations of linear beams for the problems of moving mass-beam interaction using a meshfree method
Keivan Kiani, Ali Nikkhoo
This paper deals with the capabilities of linear and nonlinear beam theories in predicting the dynamic response of an elastically supported thin beam traversed by a moving mass. To this end, the discrete equations of motion are developed based on Lagrange's equations via reproducing kernel particle method (RKPM). For a particular case of a simply supported beam, Galerkin method is also employed to verify the results obtained by RKPM, and a reasonably good agreement is achieved. Variations of the...
Investigation on the choice of boundary conditions and shape functions for flexible multi-body system
Ke-Qi Pan, Jin-Yang Liu
The objective of this investigation is to examine the correctness and efficiency of the choice of boundary conditions when using assumed mode approach to simulate flexible multi-body systems. The displacement field due to deformation is approximated by the Rayleigh-Ritz assumed modes in floating frame of reference (FFR) formulation. The deformations obtained by the absolute nodal coordinate (ANC) formulation which are transformed by two sets of reference coordinates are introduced as a criterion...
Nonlinear dynamic response of beam and its application in nanomechanical resonator
Yin Zhang, Yun Liu, Kevin D. Murphy
Nonlinear dynamic response of nanomechanical resonator is of very important characteristics in its application. Two categories of the tension-dominant and curvaturedominant nonlinearities are analyzed. The dynamic nonlinearity of four beam structures of nanomechanical resonator is quantitatively studied via a dimensional analysis approach. The dimensional analysis shows that for the nanomechanical resonator of tension-dominant nonlinearity, its dynamic nonlinearity decreases monotonically with i...
A study on wrinkling characteristics and dynamic mechanical behavior of membrane
Yun-Liang Li, Ming-Yu Lu, Hui-Feng Tan, Yi-Qiu Tan
An eigenvalue method considering the membrane vibration of wrinkling out-of-plane deformation is introduced, and the stress distributing rule in membrane wrinkled area is analyzed. A dynamic analytical model of rectangular shear wrinkled membrane and its numerical analysis approach are also developed. Results indicate that the stress in wrinkled area is not uniform, i.e. it is larger in wrinkling wave peaks along wrinkles and two ends of wrinkle in vertical direction. Vibration modes of wrinkled...
Displaced orbits generated by solar sails for the hyperbolic and degenerated cases
Ming Xu, Shi-Jie Xu
Displaced non-Keplerian orbits above planetary bodies can be achieved by orientating the solar sail normal to the sun line. The dynamical systems techniques are employed to analyze the nonlinear dynamics of a displaced orbit and different topologies of equilibria are yielded from the basic configurations of Hill's region, which have a saddlenode bifurcation point at the degenerated case. The solar sail near hyperbolic or degenerated equilibrium is quite unstable. Therefore, a controller preservi...
Lateral dynamic flight stability of hovering insects: theory vs. numerical simulation
Yan-Lai Zhang, Jiang-Hao Wu, Mao Sun
In the present paper, the lateral dynamic flight stability properties of two hovering model insects are predicted by an approximate theory based on the averaged model, and computed by numerical simulation that solves the complete equations of motion coupled with the Navier-Stokes equations. Comparison between the theoretical and simulational results provides a test to the validity of the assumptions made in the theory. One of the insects is a model dronefly which has relatively high wingbeat fre...
Biomechanical evaluation of heel elevation on load transfer—experimental measurement and finite element analysis
Yan Luximon, Ameersing Luximon, Jia Yu, Ming Zhang
In spite of ill-effects of high heel shoes, they are widely used for women. Hence, it is essential to understand the load transfer biomechanics in order to design better fit and comfortable shoes. In this study, both experimental measurement and finite element analysis were used to evaluate the biomechanical effects of heel height on foot load transfer. A controlled experiment was conducted using custom-designed platforms. Under different weight-bearing conditions, peak plantar pressure, contact...
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