Please wait a minute...
All
Member of CSTAM
 
 
Dynamics>>More
Table of Content
20 August 2020, Volume 42 Issue 4
For Selected: Toggle Thumbnails
    Review
    2020, 42(4):  397-404.  doi:10.6052/0459-1879-19-482
    Abstract ( 46 )   HTML( 49 )   PDF (14106KB) ( 49 )  
    The concept of the supersonic biplane was proposed by Adolf Busemann, a German aerodynamist, in 1935. In recent years, the supersonic biplane has re-attracted the aeronautical scientist's interest in order to meet the needs of supersonic transport's low sonic boom and low supersonic cruise drag. In this paper, the working mechanism of the typical supersonic biplane is summarized. The basic problems faced by the application of the supersonic biplane, such as non-design point characteristics and three-dimensional problems, are introduced. Finally, the key problems and the application prospects of the supersonic biplane in the future are prospected.
    Applied Research
    DROP FORMATION FROM A CAPILLARY TUBE IN THE PRESENCE OF SURFACTANT1)
    CHEN Yazhou, ZHOU Zhiqiang, PENG Jie
    2020, 42(4):  405-412.  doi:10.6052/0459-1879-19-484
    Abstract ( 39 )   HTML( 43 )   PDF (590KB) ( 43 )  
    In this study, the growth of an incompressible Newtonian drop from a vertical circular capillary tube in the presence of surfactant is analyzed. The flow is assumed to be axisymmetric and can be reduced to a spatially one-dimensional system by using the Taylor expansion and the lubrication approximation. The finite difference method combined with a coordinate transform is adopted for the numerical simulation. The results show that the existence of the surfactant will promote the breakup process of the drop, and prolong the limit length. Furthermore, the surfactant concentration has a more critical influence on the interface shapes than the surfactant activity.
    2020, 42(4):  413-417.  doi:10.6052/0459-1879-19-483
    Abstract ( 34 )   HTML( 20 )   PDF (349KB) ( 20 )  
    This paper presents a simple method to estimate and optimize the maximum launch capability of low Earth orbit (LEO) with different launch modes and trajectories, combined with trajectory optimization. The numerical calculation is carried out for the CZ-7 rocket, to analyze the specific effect and the characteristics of the optimal launch trajectory when launching with the cross-feed technology. The results show that the maximum launch capability of the LEO can be increased by 3 t (about 20%) and the maximum axial acceleration during the launch can be reduced by nearly 50% if for the CZ-7, the propellant cross-feed technology is applied in the launching process. With the help of the propellant cross-feed technology, the launch capability of such lift launch vehicle can be greatly improved.
    2020, 42(4):  418-423.  doi:10.6052/0459-1879-20-009
    Abstract ( 32 )   PDF (312KB) ( 26 )  
    The freeplay of the control surfaces is a cause of the structural nonlinearity, which will easily lead to the limit cycle flutter. According to the design requirements, considering the center freeplay of the control surface, rational function approximations of the unsteady aerodynamics in the frequency-domain are constructed based on the Minimum-State Approximation Formula, with the nonlinear stiffness caused by the center freeplay being described by the subsection function. Then the nonlinear response characteristics and the behaviors of the limit cycle flutter due to the freeplay on the control surface are studied. Results show that due to the influence of the central freeplay in the nonlinear system, the limit cycle oscillation is produced below the linear flutter speed, and the limit cycle amplitude increases with the increase of the flight speed or the center gap.
    2020, 42(4):  424-429.  doi:10.6052/0459-1879-20-034
    Abstract ( 23 )   HTML( 28 )   PDF (7510KB) ( 28 )  
    The inhaled nanoparticles (NPs) are first met by the biological barrier inside the alveolus known as the lung surfactant (LS). They can reach deep into the lung and interfere with the biophysical properties of the lung components. The interaction mechanisms of the gold nanoparticles (AuNPs) with the LS monolayer and the consequences of the interactions on the lung function are not well understood. Coarse-grained molecular dynamics simulations are carried out to study the interaction between the AuNPs and the LS monolayers at the nanoscale. It is observed that the presence of the AuNPs deforms the monolayer structure, changes the biophysical properties of the LS monolayer, and the results also indicate that the AuNPs with different shapes have different effects on the LS monolayer. These findings could help to identify the possible consequence of the airborne NPs inhalation.
    FREE VIBRATION ANALYSIS OF CARBON NANOTUBES BASED ON THE MESHLESS METHOD1)
    LI Lin, SHI Feng, XIANG Song, ZHAO Weiping, WANG Yanbing
    2020, 42(4):  430-434.  doi:10.6052/0459-1879-20-014
    Abstract ( 30 )   PDF (410KB) ( 27 )  
    Free vibration of carbon nanotubes is analyzed by the meshless method. Several numerical examples are used to verify the convergence of the present method. The natural frequencies of the carbon nanotubes of different length-to-diameter ratios are calculated and compared with the available results in published literature. The results show that the present method enjoys a high accuracy, and the meshless method based on the thin-plate spline radial basis function can successfully be used to analyze the free vibration of carbon nanotubes.
    2020, 42(4):  435-441.  doi:10.6052/0459-1879-20-101
    Abstract ( 26 )   PDF (2698KB) ( 25 )  
    In order to obtain the impact mechanical properties of coal containing gas, the mechanical properties of coal samples with adsorption gas pressures of 0 MPa, 2 MPa, 4 MPa and 6 MPa are determined by the uniaxial compression test method. The results show that the compressive strength, the elastic modulus and the impact energy index of coal samples decrease linearly and the peak strain increases linearly with the increase of the adsorbed gas pressure. With the increase of the adsorbed gas pressure, the failure type of the coal body changes from brittleness to ductility, and the portion of the separation failure portion is enhanced. The adsorbed gas accelerates the process of instability and failure of the coal body, and makes the coal and rock gas dynamic disaster change from the rock burst dominated type to the coal and gas outburst dominated type.
    2020, 42(4):  442-446.  doi:10.6052/0459-1879-20-022
    Abstract ( 45 )   PDF (412KB) ( 43 )  
    A dynamic model and the related equations for a loaded shoulder-pole during walking are established. Three frequencies are involved, i.e. the vibration frequency of the load simplified as a pendulum, the walking frequency and the vertical vibrant frequency of the loaded shoulder-pole. Numerical calculation results indicate that in order to make the walking comfortable, the above three frequencies should be coordinated. When the walking frequency is 70%,$\sim$80% of the vertical vibrant frequency of the loaded shoulder-pole, the vertical additional dynamic reaction force on the shoulder is about 30% of the weight of the load and is in the same direction with the vertical moment of the shoulder. When the vibration frequency of the load simplified as a pendulum is 25%,$\sim$30% of the walking frequency, the swing of the loads and the horizontal additional dynamic reaction force on the shoulder are relatively small.
    WIND TUNNEL TEST AND STABILITY STUDY OF ICED QUAD BUNDLE CONDUCTOR1)
    MIN Guangyun, LIU Xiaohui, Yan Bo, SUN Ceshi, CAI Mengqi
    2020, 42(4):  447-454.  doi:10.6052/0459-1879-20-006
    Abstract ( 29 )   PDF (1477KB) ( 27 )  
    The aerodynamic coefficients of the iced quad bundle conductor and a single conductor are obtained under four different conditions through wind tunnel test. The equivalent aerodynamic coefficients of the central axis of the quad bundle conductor are obtained by the equivalent method and compared with those of a single conductor under the same conditions. Based on the Den Hartog's galloping mechanism and the Nigol's torsional mechanism, the stable and unstable regions of the equivalent coefficients of the iced quad bundle conductor are determined. The results of this paper can be used in the research of the galloping and the simulation of the galloping of the iced conductor.