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Aerodynamic Interactions between Contralateral Wings and between Wings and body of a Model Insect at Hovering and Small Speed Motions

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Chinese Journal of Aeronautics 2011年第4期24卷 396-409页

作者： LIANG bin sun Mao Ministry-of-Education Key Laboratory of Fluid Mechanics Beihang University Beijing 100191 China

In this paper, we study the aerodynamic interactions between the contralateral wings and between the body and wings of a model insect, when the insect is hovering and has various translational and rotational motions, using the method numerically solving the Navier-Stokes equations over moving overset grids. The aerodynamic interactional effects are identified by compar-ing the results of a complete model insect, the corresponding wing pair, single wing and body without the wings. Horizontal, vertical and lateral translations and roll, pitch and yaw rotations at small speeds are considered. The results indicate that for the motions considered, both the interaction between the contralateral wings and the interaction between the body and wings are weak. The changes in the forces and moments of a wing due to the contralateral wing interaction, of the wings due to the pres-ence of the body, and of the body due to the presence of the wings are generally less than 4.5%. Results show that aerodynamic forces of wings and body can be measured or computed separately in the analysis of flight stability and control of hovering in-sects.

关键词： insect aerodynamics Navier-Stokes simulation wing/wing interaction wing/body interaction

Study on vulnerability matrices of masonry buildings of mainland of China

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Earthquake Engineering and Engineering Vibration 2018年第2期17卷 251-259页

作者： sun baitao Zhang Guixin Institute of Engineering Mechanics China Earthquake AdministrationHarbin 150080China Key Laboratory of Earthquake Engineering and Engineering Vibration of China Earthquake Administration Harbin 150080China

The degree and distribution of damage to buildings subjected to earthquakes is a concern of the Chinese Government and the *** damage data indicates that seismic capacities of different types of building structures in various regions throughout mainland of China are ***,the seismic capacities of the same type of structure in different regions may *** contributions of this research are summarized as follows：1）Vulnerability matrices and earthquake damage matrices of masonry structures in mainland of China were chosen as research *** aim was to analyze the differences in seismic capacities of sample matrices and to present general rules for categorizing seismic resistance.2）Curves relating the percentage of damaged masonry structures with different seismic resistances subjected to seismic demand in different regions of seismic intensity（VI to X）have been developed.3）A method has been proposed to build vulnerability matrices of masonry *** damage ratio for masonry structures under high-intensity events such as the Ms 6.1 Panzhihua earthquake in Sichuan province on 30 August2008,was calculated to verify the applicability of this *** research offers a significant theoretical basis for predicting seismic damage and direct loss assessment of groups of buildings,as well as for earthquake disaster insurance.

关键词： seismic capacity seismic intensity seismic resistances seismic damage matrix

THE F5 ALGORITHM IN bUCHbERGER＇S STYLE

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Journal of Systems Science & Complexity 2011年第6期24卷 1218-1231页

作者： Yao sun Dingkang WANG Key Laboratory of Mathematics Mechanization Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

The famous F5 algorithm for computing Grobner basis was presented by Faugere in 2002. The original version of F5 is given in programming codes, so it is a bit difficult to understand. In this paper, the F5 algorithm is simplified as F5b in a buchberger＇s style such that it is easy to understand and implement. In order to describe F5b, we introduce F5-reduction, which keeps the signature of labeled polynomials unchanged after reduction. The equivalence between F5 and F5b is also shown. At last, some versions of the F5 algorithm are illustrated.

关键词： buchberger's style F5 algorithm Grobner basis.

Dynamic flight stability of a hovering model insect:lateral motion

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Acta Mechanica Sinica 2010年第2期26卷 175-190页

作者： Yanlai Zhang Mao sun Ministry-of-Education Key Laboratory of Fluid Mechanics Institute of Fluid Mechanics Beihang University 100191 Beijing China

The lateral dynamic flight stability of a hovering model insect （dronefly） was studied using the method of computational fluid dynamics to compute the stability derivatives and the techniques of eigenvalue and eigenvector analysis for solving the equations of motion. The main results are as following. （i） Three natural modes of motion were identified： one unstable slow divergence mode （mode 1）, one stable slow oscillatory mode （mode 2）, and one stable fast subsidence mode （mode 3）. Modes 1 and 2 mainly consist of a rotation about the horizontal longitudinal axis （x-axis） and a side translation; mode 3 mainly consists of a rotation about the x-axis and a rotation about the vertical axis. （ii） Approximate analytical expressions of the eigenvalues are derived, which give physical insight into the genesis of the natural modes of motion. （iii） For the unstable divergence mode, td, the time for initial disturbances to double, is about 9 times the wingbeat period （the longitudinal motion of the model insect was shown to be also unstable and td of the longitudinal unstable mode is about 14 times the wingbeat period）. Thus, although the flight is not dynamically stable, the instability does not grow very fast and the insect has enough time to control its wing motion to suppress the disturbances.

关键词： Insect Dynamic flight stability Hovering ·Lateral motion Natural modes of motion

Wing kinematics measurement and aerodynamics of free-flight maneuvers in drone-flies

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Acta Mechanica Sinica 2010年第3期26卷 371-382页

作者： Yanlai Zhang Mao sun Ministry-of-Education Key Laboratory of Fluid Mechanics Institute of Fluid Mechanics Beihang University 100191 Beijing China

The time courses of wing and body kinematics of two free-flying drone-flies, as they performed saccades, were measured using 3D high-speed video, and the morpho- logical parameters of the wings and body of the insects were also measured. The measured wing kinematics was used in a Navier-Stokes solver to compute the aerodynamic forces and moments acting on the insects. The main results are as following. （1） The turn is mainly a 90° change of heading. It is made in about 10 wingbeats （about 55 ms）. It is of interest to note that the number of wingbeats taken to make the turn is approximately the same as and the turning time is only a little different from that of fruitflies measured recently by the same approach, even if the weight of the droneflies is more than 100 times larger than that of the fruitflies. The long axis of body is about 40° from the horizontal during the maneuver. （2） Although the body rotation is mainly about a vertical axis, a relatively large moment around the yaw axis （axis perpendicular to the long axis of body）, called as yaw moment, is mainly needed for the turn, because moment of inertial of the body about the yaw axis is much larger than that about the long axis. （3） The yaw moment is mainly pro- duced by changes in wing angles of attack： in a right turn, for example, the dronefly lets its right wing to have a rather large angle of attack in the downstroke （generally larger than 50°） and a small one in the upstroke to start the turn, and lets its left wing to do so to stop the turn, unlike the fruitflies who generate the yaw moment mainly by changes in the stroke plane and stroke amplitude.

关键词： Drone-fly - Maneuver Wing kinematicsmeasurement Aerodynamics Navier-Stokes simulation

A computational study of the wing-wing and wing-body interactions of a model insect

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Acta Mechanica Sinica 2009年第4期25卷 421-431页

作者： Xin Yu Mao sun Institute of Applied Physics and Computational Mathematics Beihang University 100191 Beijing China Institute of Fluid Mechanics Beihang University 100191 Beijing China

The aerodynamic interaction between the contralateral wings and between the body and wings of a model insect are studied, by using the method of numerically solving the Navier-Stokes equations over moving overset grids, under typical hovering and forward flight conditions. both the interaction between the contralateral wings and the interaction between the body and wings are very weak, e.g. at hovering, changes in aerodynamic forces of a wing due to the present of the other wing are less than 3% and changes in aerodynamic forces of the wings due to presence of the body are less than 2%. The reason for this is as following. During each down- or up-stroke, a wing produces a vortex ring, which induces a relatively large jet-like flow inside the ring but very small flow outside the ring. The vortex rings of the left and right wings are on the two sides of the body. Thus one wing is outside vortex ring of the other wing and the body is outside the vortex rings of the left and right wings, resulting in the weak interactions.

关键词： Insect Aerodynamics Wing/winginteraction Wing/body interaction

Control for going from hovering to small speed flight of a model insect

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Acta Mechanica Sinica 2009年第3期25卷 295-302页

作者： Jianghao Wu Mao sun School of Transportation Science and Engineering Beihang University 100191 Beijing China Institute of Fluid Mechanics Beihang University 100191 Beijing China

The longitudinal steady-state control for going from hovering to small speed flight of a model insect is studied, using the method of computational fluid dynamics to compute the aerodynamic derivatives and the techniques based on the linear theories of stability and control for determining the non-zero equilibrium points. Morphological and certain kinematical data of droneflies are used for the model insect. A change in the mean stroke angle （δФ） results in a horizontal forward or backward flight; a change in the stroke amplitude （δФ） or a equal change in the down- and upstroke angles of attack （δα1） results in a vertical climb or decent; a proper combination of δФ and δФ controls （or δФ and δα1 controls） can give a flight of any （small） speed in any desired direction.

关键词： Insect. Flight control Hovering ,Small speed flight

Damage characteristics and seismic capacity of buildings during Nepal M_s 8.1 earthquake

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Earthquake Engineering and Engineering Vibration 2015年第3期14卷 571-578页

作者： sun baitao Yan Peilei Institute of Engineering Mechanics China Earthquake Administration Key Laboratory of Earthquake Engineering and Engineering Vibration China Earthquake Administration

The extensive damage to buildings caused by the Nepal Ms8.1 earthquake has attracted much attention by the international *** preliminary scientific investigations on the different affected areas inNepal,the construction and damage characteristics of five different types of buildings commonly existing in Nepal were discussed and the reasons of their disaster performance were *** of buildings investigated include reinforced concrete(RC) frame structures,rubble structures,brick-wood structures,raw soil structures,and brick-wood structures of historic *** addition,the weak links of the seismic design were pointed out,which was very important for the post-earthquake reconstruction and recovery,and gave a preliminary explanations for the damage experienced.

关键词： Nepal earthquake seismic damage of building seismi

blindness-free beam scanning antenna with array of array architecture: principle,design,and experiment

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Science China(Information Sciences) 2024年第3期67卷 209-224页

作者： Jianxu sun Yujian CHENG School of Electronic Science and Engineering University of Electronic Science and Technology of China

This paper presents a 66–76-GHz sparsely-excited phased array antenna with the array of array(Ao A) architecture for eliminating the blindness and suppressing the grating lobe when scanning. For the array antennas printed on the thick dielectric layers with high relative permittivity, scanning blindness appears and seriously impacts the radiation performance. To address this issue, the Ao A topology is developed first. It finds that the scanning blindness appears due to the coupling of the radiating Floquet modes to the non-radiating surface wave(SW) modes. Therefore, the array is divided into two types of domino *** inner-phase distributions are introduced into the domino subarrays to break the one-to-one relationship between the Floquet mode and the SW mode. Then, the blindness inside ±60° scanning volume is eliminated by the aperiodic subarrays. Meanwhile, the aperiodic inner-phase distributions enhance the aperiodicity of the array and contribute to suppressing the grating lobe when scanning. Next, the meta-surface-based dipole with the shorted post is chosen as the unit cell for the proposed aperiodic array. based on these methods,the array achieves the wide-scanning performance of ±60° in the E-plane and ±30° in the H-plane, without the blindness and the grating lobe. Finally, the 16×16 array is built and simulated with the dimension of32 mm × 32 mm. At the highest operating frequency, the simulated gains are 28.42, 25.17, and 24.01 d bi when scanning to the broadside, 50° in the E-plane, and 30° in the H-plane, respectively. Compared to the ideal gain, it shows that the simulated radiation efficiency is about 84.13%, 62.08%, and 35.23% when scanning to the broadside, 50° in the E-plane, and 30° in the H-plane, respectively. The worst transmission coefficient, i.e., the worst isolation, is-11.97 d b between the central element and its two adjacent elements in the E-plane. The array prototypes are fabricated, and the experiments are carried out to ver

关键词： 6G communication systems phased array AoA aperiodic subarray wideband wide-scanning surface-wave scanning blindness grating lobe

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