GRAPHIC ABSTRACT

GRAPHIC ABSTRACT
Acta Mechanica Sinica, Volume 30, Number 5, October 2014
THEME ARTICLES ON “ORBITS AROUND ASTEROID”
Low-thrust trajectory optimization in a full ephemeris model
Xing-Shan Cai · Yang Chen · Jun-Feng Li
This paper presents a method to solve the fuel-optimal problem of low-thrust trajectory
with complicated constraints in a full ephemeris model, which introduces the various
perturbations, including a third body’s gravity, the nonspherical perturbation and the
solar radiation pressure in a dynamic equation. This paper also builds two types of
equivalent inner constraints to direct the spacecraft fly through the sphere of influence
of planet in order to get GA.
Acta Mechanica Sinica 30, 615–627 (2014)
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Time-optimal rendezvous transfer trajectory for restricted cone-angle
range solar sails
Jing He · Sheng-Ping Gong · Fang-Hua Jiang · Jun-Feng Li
In this paper, the time-optimal rendezvous is designed over a restricted range of cone
angles, with the indirect method. Relevant numerical examples are provided to compare
with the case of an unrestricted cone-angle range, and the effects of different maximum
restricted cone angles are discussed. The results indicate that (1) for the condition of a
restricted cone-angle range the transfer time is longer than that for the unrestricted case Acta Mechanica Sinica 30, 628–635 (2014)
and (2) the optimal transfer time increases with the decrease of the maximum restricted
cone angle.
FLUID MECHANICS
Dynamics of low-speed streak evolution and interaction in laminar boundary layer
Si-Chao Deng · Chong Pan · Jin-Jun Wang
The regeneration process of the spanwisely-aligned low-speed streaks is studied experimentally. As is shown by cross-sectional distribution of U/U∞ in Fig. a, the laminar
boundary layer is characterized by two low-speed streaks induced by streamwise vorticity though lift-up effect at x = 300 mm. Two new-born speed deficit structures occur on
the flank side of the primary streaks at x = 900 mm (shown in Fig. b). Far downstream,
the velocity field is characterized by four low-speed streaks. In this sense, the disturbance can propagate along the spanwise direction and the streak reproduction process
plays a key role in turbulence self-sustaining process.
Acta Mechanica Sinica 30, 636–645 (2014)
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Transient simulation of a pump-turbine with misaligned guide vanes during turbine model start-up
Ye-Xiang Xiao · Ruo-Fu Xiao
Experimental analyses of a model pump-turbine S-curve characteristics and its improvement by Misaligned Guide Vanes were then extended to a prototype pump-turbine
through 3-D transient flow simulations. The unsteady RANS equations with the SST
turbulence model were used to model the transient flow with and without MGV during turbine mode start-up. The use of MGV can eliminate the S-curve characteristics,
and can significantly increase the pressure pulse amplitude and the runner radial forces.
The hydraulic reason is the MGV dramatically changed the flow patterns, destroyed the
symmetry of the flow distribution inside the guide vane and runner.
Acta Mechanica Sinica 30, 646–655 (2014)
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On the horizontal distribution of algal-bloom in Chaohu Lake and its formation process
Yuan-Ying Chen · Qing-Quan Liu
The formation of algae horizontal distribution in Chaohu Lake is dependent on a twotime scale process. At the longer time scale, i.e., during the bloom season, the primary
distribution of biomass is determined by nutrient loading transported by the prevailing
wind induced current; and at the shorter time scale, i.e., on the day when bloom occurs,
the distribution of algae is adjusted by the wind of the day and algae reaches the places
Acta Mechanica Sinica 30, 656–666 (2014)
where blooms actually occur.
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Fully nonlinear modeling of radiated waves generated by floating flared
structures
Bin-Zhen Zhou · De-Zhi Ning · Bin Teng · Ming Zhao
A three-dimensional fully nonlinear numerical model for a structure in forced motion
has been developed with a higher-order boundary element method. Numerical experiments are carried out to simulate the heave motions of a submerged sphere in infinite
depth, the heave and pitch motions of a truncated flared cylinder in finite depth. The
difference among fully nonlinear, body-nonlinear and linear results is analyzed. It is
found that the nonlinearity due to free surface and body surface influences the numerical results of the radiated waves and forces significantly.
Acta Mechanica Sinica 30, 667–680 (2014)
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An experimental research on surface oscillation
thermocapillary convection in open cylindrical annuli
of
buoyant-
Li Zhang · Li Duan · Qi Kang
An experiment is carried out on the surface oscillation of buoyant-thermocapillary
convection in an open cylindrical annulus. When the radial temperature difference
∆T reaches a critical value ∆T c , a regular oscillation appears and soon disappears on
the open surface, which varies when the liquid layer’s thickness h and temperature
difference ∆T are varied. With growth of ∆T , dominant frequency of the visible
oscillation will grow too but is found within certain frequencies. Driving forces,
buoyance and thermocapillarity, are responsible for this phenomanon and the “balance” Acta Mechanica Sinica 30, 681–686 (2014)
point is considered to exist when h is between 4.5–5.0 mm. Surface oscillation region
is also found restricted within a narrow gap when Bo is smaller than 3.7.
SOLID MECHANICS
Artificial boundary conditions for Euler–Bernoulli beam equation
Shao-Qiang Tang · Eduard G. Karpov
In a semi-discretized Euler-Bernoulli beam equation, the non-nearest neighboring interaction and large span of temporal scales for wave propagations pose challenges to the
effectiveness and stability for artificial boundary treatments. With the discrete equation
regarded as an atomic lattice with a three-atom potential, two accurate artificial boundary conditions are first derived here. Reflection coefficient and numerical tests illustrate
the capability of the proposed methods. In particular, the time history treatment gives
an exact boundary condition, yet with sensitivity to numerical implementations. The
ALEX (ALmost EXact) boundary condition is numerically more effective.
Acta Mechanica Sinica 30, 687–692 (2014)
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Dislocation stability in three-phase nanocomposites with imperfect interface
Ying-Xin Zhao · You-Wen Liu · Qi-Hong Fang
The elastic behavior of a screw dislocation in nanoscale coating with imperfect interface is studied in the three-phase composite cylinder model. The interface between inner nanoinhomogeneity and intermediate coating is assumed as perfectly bonded. The
bonding between intermediate coating and outer matrix is considered to be imperfect
with the assumption that interface imperfection is uniform, and a linear spring model
is adopted to describe the weakness of imperfect interface. The explicit expression for
image force acting on dislocation is obtained by means of a complex variable method.
The analytic results indicate that inner interface effect and outer interface imperfection,
simultaneously taken into account, would influence greatly image force, equilibrium
position and stability of dislocation, and various critical parameters that would change Acta Mechanica Sinica 30, 693–702 (2014)
dislocation stability. The weaker interface is a very strong trap for glide dislocation and,
thus, a more effective barrier for slip transmission.
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Propagation behavior of elastic waves in one-dimensional piezoelectric/piezomagnetic phononic crystal with line defects
Y. Pang · F.-Y. Jiao · J.-X. Liu
When a piezoelectric/piezoelectric or piezomagnetic/piezomagnetic defect layer being
inserted in a one-dimensional piezoelectric/piezomagnetic phononic crystal (PC), defect modes may appear in the gaps of the perfect PC. The defect modes are dependent
on the volume fraction, material properties and the location of the defect layers.
Acta Mechanica Sinica 30, 703–713 (2014)
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Theoretical analysis of the sound absorption characteristics of periodically
stiffened micro-perforated plates
Hai-An Zhou · Xiao-Ming Wang · Yu-Lin Mei
Semi-analytical methods to estimate the vibro-acoustic responses and sound absorption
characteristics of different kinds of periodically stiffened plates of micro-perforated are
presented. Numerical results indicate that the absorption performance of the periodically stiffened plates is effectively enhanced by constructing them with micro-holes,
and the perforation of the plate plays an important role in the absorption coefficient. It
is found that the absorption coefficient of the micro-perforated stiffened plate is little
affected by its flexural vibration effect in the air, but is significantly influenced in the Acta Mechanica Sinica 30, 714–726 (2014)
water fluid.
DYNAMICS, VIBRATION, AND CONTROL
Stability and oscillations in a slow-fast flexible joint system with transformation delay
Shan-Ying Jiang · Jian Xu · Yao Yan
A link-rotor structure connected by a flexible joint is modeled to be a slow-fast delayed
system when moment of inertia of the lightweight link is far less than that of the heavy
rotor. The mechanisms of the regular periodic oscillation, as well as relaxation oscillation and bursting oscillation are illustrated according to the theory of geometric singular
perturbation.
Acta Mechanica Sinica 30, 727–738 (2014)
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iv
Dynamics of a prey-predator system under Poisson white noise excitation
Shan-Shan Pan · Wei-Qiu Zhu
In the present paper, the pulse-type version of stochastic LV model, in which the effect
of a random natural environment has been modeled as Poisson white noise, is investigated by using the stochastic averaging method. The averaged generalized Ito stochastic differential equation and Fokker-Planck-Kolmogorov (FPK) equation are derived for
prey-predator ecosystem driven by Poisson white noise. Approximate stationary solution for the averaged generalized FPK equation is obtained by using the perturbation
method. The effect of prey self-competition parameter ε2 s on ecosystem behavior is
evaluated. The analytical result is confirmed by corresponding Monte Carlo (MC) sim- Acta Mechanica Sinica 30, 739–745 (2014)
ulation.
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Coupled lateral-torsional-axial vibrations of a helical gear-rotor-bearing
system
Chao-Feng Li · Shi-Hua Zhou · Jie Liu · Bang-Chun Wen
The paper presented a model for a type of angular contact ball bearing (Fig.1a) system by taking into account the lateral effect, torsional and axial vibration. A lumpedparameter nonlinear dynamic model, as shown in Fig. 1b, is established. Dynamics of
this system was investigated. The results show that the vibration amplitudes have obvious fluctuation, and the frequency multiplication and random frequency components
become increasingly obvious with changing rotational speed and eccentricity. Axial vi- Acta Mechanica Sinica 30, 746–761 (2014)
bration of the HGRBS also has some fluctuations. The bearing has self-variable stiffness
frequency, which should be avoided in engineering design stage.
BIO-MECHANICS
Biomechanical and dynamic mechanism of locust take-off
Dian-Sheng Chen · Jun-Mao Yin · Ke-Wei Chen · Zhen Li
This paper explores the bionic dynamics model of locust jumping by using high-speed
video and force analysis and applies hybrid rigid-flexible mechanisms to bionic locust
hopping and studies its dynamics with emphasis laid on the relationship between force
and jumping performance. The hybrid rigid-flexible model is introduced in the analysis
of locust mechanism to address the principles of dynamics that govern locust joints
and mechanisms during energy storage and take-off. The dynamic response of the
biomimetic mechanism is studied by considering the flexibility according to the locust
jumping dynamics mechanism. A multi-rigid-body dynamics model of locust jumping
is established and analyzed based on Lagrange method; elastic knee and tarsus mechanisms that were proposed in previous works are analyzed alongside the original bionic
Acta Mechanica Sinica 30, 762–774 (2014)
joint configurations and their machinery principles.
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