UNILATERAL CONTACT PROBLEMS USING QUASI-ACTIVE SET STRATEGY

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｒｅａｒｅｏｆｔｅｎｓｏｍｅｓｔｒｕｃｔｕｒｅｓｏｒｃｏｍｐｏｎｅｎｔｓｗｈｉｃｈｃａｎｏｎｌｙｔｒａｎｓｆｅｒｏｎｅｓｐｅｃｉａｌｆｏｒｍｏｆｓｔｒｅｓｓ,ｓｕｃｈａｓｔｈｅｃａｂｌｅｗｈｉｃｈｃａｎｏｎｌｙｂｅｕｓｅｄｔｏｔｒａｎｓｆｅｒｔｈｅｔｅｎｓｉｏｎｓｔｒｅｓｓａｎｄｔｈｅｃｏｎｔａｃｔｃｏｍｐｏｎｅｎｔｗｈｉｃｈｃａｎｏｎｌｙｔｒａｎｓｆｅｒｔｈｅｐｒｅｓｓｕｒｅ.Ｉｎｇｅｎｅｒａｌ,ｓｕｃｈｐｒｏｂｌｅｍｓａｒｅｏｆｔｅｎｃａｌｌｅｄｔｈｅｕｎｉｌａｔ…     

COMPUTATION OF SUPERSONIC TURBULENT FLOWFIELD WITH TRANSVERSE INJECTION

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｍｉｘｉｎｇｆｌｏｗｆｉｅｌｄｒｅｓｕｌｔｉｎｇｆｒｏｍａｓｏｎｉｃｇａｓｅｏｕｓｉｎｊｅｃｔｉｏｎｉｎｊｅｃｔｅｄｔｒａｎｓｖｅｒｓｅｌｙｉｎｔｏａｓｕｐｅｒｓｏｎｉｃｆｒｅｅｓｔｒｅａｍｉｓｅｎｃｏｕｎｔｅｒｅｄｉｎｍａｎｙｆｉｅｌｄｓｓｕｃｈａｓｒｏｃｋｅｔｍｏｔｏｒｔｈｒｕｓｔｖｅｃｔｏｒｃｏｎｔｒｏｌｓｙｓｔｅｍｓ,ｓｕｐｅｒｓｏｎｉｃｃｏｍｂｕｓｔｉｏｎ ,ｈｉｇｈ＿ｓｐｅｅｄｆｌｉｇｈｔｖｅｈｉｃｌｅｒｅａｃｔｉｏｎｃｏｎｔｒｏｌｊｅｔｓ,ａｎｄｇａｓ＿ｔ…     

On the Bending, Vibration and Stability of Laminated Rectangular Plates with Transversely Isotropic Layers

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｔａｔｉｃｓａｎｄｄｙｎａｍｉｃｓｏｆｒｅｃｔａｎｇｕｌａｒｐｌａｔｅｓｈａｖｅａｌｗａｙｓｂｅｅｎｏｆｐａｒｔｉｃｕｌａｒｒｅｓｅａｒｃｈｉｎｔｅｒｅｓｔｉｎｓｏｌｉｄｍｅｃｈａｎｉｃｓ.Ｉｎｐａｒｔｉｃｕｌａｒ,ｔｈｅｅｍｅｒｇｅｎｃｅｏｆｎｅｗｍａｔｅｒｉａｌｓａｎｄｎｅｗｓｔｒｕｃｔｕｒｅｓｈａｓｂｒｏｕｇｈｔｏｕｔｅｎｄｌｅｓｓｖｉｔａｌｆｏｒｃｅｉｎｔｏｔｈｅｓｔｕｄｙ .Ｉｔｉｓｗｅｌｌ＿ｋｎｏｗｎｔｈａｔｔｈｅｃｌａｓｓｉｃａｌｐｌａｔｅｔｈｅｏｒｙｂ…     

On the spectral equivalence of unconventional finite elements and their conventional relatives

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ,ｗｉｔｈｔｒｅｍｅｎｄｏｕｓｄｅｖｅｌｏｐｍｅｎｔｏｆｐａｒａｌｌｅｌｃｏｍｐｕｔｅｒｓ,ｔｈｅｐｒｏｂｌｅｍｏｆｈｏｗｔｏｃｏｎｓｔｒｕｃｔｅｆｆｅｃｔｉｖｅｄｏｍａｉｎｄｅｃｏｍｐｏｓｉｔｉｏｎｐａｒａｌｌｅｌａｌｇｏｒｉｔｈｍｓｆｏｒｌｉｎｅａｒｓｙｓｔｅｍａｒｉｓｉｎｇｆｒｏｍｔｈｅｆｉｎｉｔｅｅｌｅｍｅｎｔｄｉｓｃｒｅｔｉｚａｔｉｏｎｈａｓｂｅｃｏｍｅｔｈｅｆｏｃｕｓｉｎｔｈｅｆｉｅｌｄｏｆｓｃｉｅｎｔｉｆｉｃｃｏｍｐｕｔａｔｉｏｎａｌ…     

ELECTROELASTIC FIELD FOR AN IMPERMEABLE ANTI-PLANE SHEAR CRACK IN A PIEZOELECTRIC CERAMICS PLATE

ＩｎｔｒｏｄｕｃｔｉｏｎＤｕｅｔｏｔｈｅｉｎｔｒｉｎｓｉｃｃｏｕｐｌｉｎｇｃｈａｒａｃｔｅｒｉｓｔｉｃｓｂｅｔｗｅｅｎｅｌｅｃｔｒｉｃａｎｄｅｌａｓｔｉｃｂｅｈａｖｉｏｒｓ,ｔｈａｔｉｓ,ａｐｐｌｉｅｄｍｅｃｈａｎｉｃａｌｌｏａｄｉｎｇｐｒｏｄｕｃｅｓｅｌａｓｔｉｃｄｅｆｏｒｍａｔｉｏｎ ,ａｓｗｅｌｌａｓｅｌｅｃｔｒｉｃｆｉｅｌｄ ,ａｎｄｃｏｎｖｅｒｓｅｌｙｅｌｅｃｔｒｉｃｆｉｅｌｄｃａｎｇｉｖｅｒｉｓｅｔｏｅｌａｓｔｉｃｄｅｆｏｒｍａｔｉｏｎ ,ｐｉｅｚｏｅｌｅｃｔｒｉｃｍａｔｅｒｉａｌｓｈａｖｅ…     

THE LIE SYMMETRIES AND CONSERVED QUANTITIES OF VARIABLE-MASS NONHOLONOMIC SYSTEM OF NON-CHETAEV''''S TYPE IN PHASE SPACE

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｔｕｄｙｏｆｓｙｍｍｅｔｒｙａｎｄｃｏｎｓｅｒｖｅｄｑｕａｎｔｉｔｙｏｆｍｅｃｈａｎｉｃａｌｓｙｓｔｅｍｉｓａｎｉｍｐｏｒｔａｎｔｔｏｐｉｃｉｎｍａｔｈｅｍａｔｉｃｓ,ｍｅｃｈａｎｉｃｓａｎｄｐｈｙｓｉｃｓ .ＴｈｅｍｏｄｅｒｎｔｈｅｏｒｉｅｓｏｆｓｙｍｍｅｔｒｙａｎｄｃｏｎｓｅｒｖｅｄｑｕａｎｔｉｔｙｏｆｍｅｃｈａｎｉｃａｌｓｙｓｔｅｍｉｎｃｌｕｄｅＮｏｅｔｈｅｒｓｙｍｍｅｔｒｙｔｈｅｏｒｙａｎｄＬｉｅｓｙｍｍｅｔｒｙｔｈｅｏｒｙ .Ｉｎ 1979Ｍ .Ｌｕｔｚｋｙａｎｄｏ…     

ON THE ASYMPTOTIC BEHAVIOR OF HOPFIELD NEURAL NETWORK WITH PERIODIC INPUTS

ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｃｅｔｈｅｓｐｅｃｉａｌｓｕｐｅｒｉｏｒｉｔｙｏｆａｒｔｉｆｉｃｉａｌｎｅｕｒａｌｎｅｔｗｏｒｋｓｔｅｃｈｎｏｌｏｇｙｉｎｖａｒｉｏｕｓｅｎｇｉｎｅｅｒｉｎｇｔｅｃｈｎｉｑｕｅｓｆｉｅｌｄｓ,ｓｕｃｈａｓｏｐｔｉｍｉｚａｔｉｏｎ ,ａｓｓｏｃｉａｔｉｖｅｍｅｍｏｒｉｅｓ,ｐａｔｔｅｒｎｒｅｃｏｇｎｉｔｉｏｎ ,ｓｉｇｎａｌｐｒｏｃｅｓｓｉｎｇａｎｄａｕｔｏｍａｔｉｃｃｏｎｔｒｏｌ,ｔｈｅｒｅｈａｓｂｅｅｎｉｎｃｒｅａｓｉｎｇｉｎｔｅｒｅｓｔｉｎｔｈｅｉｎｖｅｓｔｉｇａｔｉ…     

Dynamical Stability of Viscoelastic Column with Fractional Derivative Constitutive Relation

ＩｎｔｒｏｄｕｃｔｉｏｎＭｏｒｅａｎｄｍｏｒｅｐｒｏｂｌｅｍｓｉｎｓｃｉｅｎｃｅａｎｄｅｎｇｉｎｅｅｒｉｎｇｈａｖｅｃｏｎｃｅｒｎｅｄｔｈｅｓｔａｂｉｌｉｔｙａｎａｌｙｓｉｓｏｆｔｈｅｖｉｓｃｏｅｌａｓｔｉｃｓｔｒｕｃｔｕｒｅｓｄｕｅｔｏｔｈｅｉｒｂｒｏａｄａｐｐｌｉｃａｔｉｏｎｓ .Ｉｎ [1]ＣｅｄｅｒｂａｕｍａｎｄＭｏｎｄａｐｐｌｉｅｄｔｈｅｍｕｌｔｉｐｌｅ＿ｓｃａｌｅｓｍｅｔｈｏｄｔｏｔｒｅａｔｓｔａｂｉｌｉｔｙｏｆａｖｉｓｃｏｅｌａｓｔｉｃｃｏｌｕｍｎｕｎｄｅｒａｐｅｒｉｏｄｉｃａｘｉａｌｌ…     

A FORM INVARIANCE OF CONSTRAINED BIRKHOFFIAN SYSTEM

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｔｕｄｙｏｆｔｈｅｄｙｎａｍｉｃｓｏｆＢｉｒｋｈｏｆｆｉａｎｓｙｓｔｅｍｉｓａｎａｃｔｉｖｅｂｒａｎｃｈｉｎｔｈｅｍｏｄｅｒｎｃｌａｓｓｉｃａｌｍａｔｈｅｍａｔｉｃｓａｎｄａｍｏｄｅｒｎｄｅｖｅｌｏｐｉｎｇｄｉｒｅｃｔｉｏｎｉｎｍａｔｈｅｍａｔｉｃｐｈｙｓｉｃｓ ,ａｎｄｃａｎｂｅａｐｐｌｉｅｄｔｏｑｕａｎｔｕｍｍｅｃｈａｎｉｃｓ,ｓｔａｔｉｓｔｉｃａｌｍｅｃｈａｎｉｃｓ ,ｂｉｏｌｏｇｉｃｐｈｙｓｉｃｓ,ｍｅｃｈａｎｉｃｓｏｆｓｐａｃｅｆｌｉｇｈｔａｎｄｓｏｍｅｆｉｅ…     

Computer Simulation of Non-Newtonian Flow and Mass Transport Through Coronary Arterial Stenosis

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｍｏｓｔｏｂｖｉｏｕｓｃｈａｒａｃｔｅｒｏｆａｔｈｅｒｏｓｃｌｅｒｏｓｉｓｉｓｔｈｅｌｏｃａｌｉｎｔｉｍａｌａｃｃｕｍｕｌａｔｉｏｎｏｆｌｏｗ＿ｄｅｎｓｉｔｙｌｉｐｏｐｒｏｔｅｉｎ(ＬＤＬ) ,ｔｈｅｉｎｃｒｅａｓｅｏｆｔｈｅｆｉｂｅｒａｌｔｉｓｓｕｅａｎｄｔｈｅｓｔｅｎｏｓｉｓ.Ｏｎｏｎｅｈａｎｄ ,ｉｔｉｓｆｏｕｎｄｔｈａｔｔｈｅｄｉｓｅａｓｅｏｆｔｅｎｏｃｃｕｒｓａｔｔｈｅｃｏｍｐｌｅｘｇｅｏｍｅｔｒｙｒｅｇｉｏｎ ,ｓｕｃｈａｓｂｉｆｕｒｃａｔｉｏｎｚｏｎｅ,ｃｕｒｅ…     

飞行器纵向俯仰气动特性计算研究

应用有限体积方法求解三维可压缩雷诺平均N-S方程,计算了巡航导弹外形飞行器作小振幅俯仰运动时的动态绕流流场和空气动力特性,开展了导弹绕不同转轴、以不同频率和在不同迎角范围内进行俯仰运动的非定常气动力迟滞特性研究。计算结果表明,当导弹作快速俯仰运动时,在上仰和下俯过程中的同一迎角瞬间,绕导弹流场流动明显不同,表现出明显的非定常迟滞特性。导弹的非定常气动力迟滞特性随俯仰运动频率的增大明显增强,且气动力迟滞曲线随着俯仰轴位置的变化而变化。在同一减缩频率下,导弹在不同迎角范围内作周期俯仰运动时,相同的运动相位角所对应的升力系数对迎角的导数是一致的,而不同减缩频率下升力系数对迎角的导数随运动相位角变化曲线明显不同。     

Near wake vortex dynamics of a hovering hawkmoth

Numerical investigation of vortex dynamics in near wake of a hovering hawkmoth and hovering aerodynamics is conducted to support the development of a biology-inspired dynamic flight simulator for flapping wingbased micro air vehicles. Realistic wing-body morphologies and kinematics are adopted in the numerical simulations. The computed results show 3D mechanisms of vortical flow structures in hawkmoth-like hovering. A horseshoe-shaped primary vortex is observed to wrap around each wing during the early down- and upstroke; the horseshoe-shaped vortex subsequently grows into a doughnut-shaped vortex ring with an intense jet-flow present in its core, forming a downwash. The doughnut-shaped vortex rings of the wing pair eventu- ally break up into two circular vortex rings as they propagate downstream in the wake. The aerodynamic yawing and rolling torques are canceled out due to the symmetric wing kinematics even though the aerodynamic pitching torque shows significant variation with time. On the other hand, the time- varying the aerodynamics pitching torque could make the body a longitudinal oscillation over one flapping cycle.     

UNCONDITIONAL STABLE SOLUTIONS OF THE EULER EQUATIONS FOR TWO－AND THREE－D WINGS IN ARBITRARY MOTION

ＵＮＣＯＮＤＩＴＩＯＮＡＬＳＴＡＢＬＥＳＯＬＵＴＩＯＮＳＯＦＴＨＥＥＵＬＥＲＥＱＵＡＴＩＯＮＳＦＯＲＴＷＯ－ＡＮＤＴＨＲＥＥ－ＤＷＩＮＧＳＩＮＡＲＢＩＴＲＡＲＹＭＯＴＩＯＮＧａｏＺｈｅｎｇｈｏｎｇ（高正红）（ＲｅｃｅｉｖｅｄＪａｎ．１２,１９９５,Ｃ...     

等速上仰翼型动态失速现象研究

翼型大迎角绕流的静态失速将造成升力突降和气动性能急剧恶化，但利用非定常运动所产生 的动态失速效应，可以大大地延缓气流分离和失速现象的发生. 采用Rogers发 展的双时间步Roe格式，求解拟压缩性修正不可压N-S方程. 数值模拟了低雷诺数 ($Re=4.8 \times 10^{4}$)条件下NACA0015翼型作等速上仰($\alpha =0^{\circ} \sim 60^{\circ}$)的动态失速过程，同Walker的试验结果比 较，验证了计算结果的正确性. 研究了该过程中主涡、二次涡和三次涡的发展，升 力系数随攻角变化，以及不同上仰速度对动态失速效应所造成的影响.     

基于流形切空间插值的折叠翼参数化气动弹性建模

变体飞行器的气动弹性力学建模是当前先进飞行器设计的研究热点和难点. 然而传统的气动弹性动力学建模方法对于具有结构参变特性的变体飞行器气动弹性力学研究存在建模效率低、计算复杂等问题. 本研究提出了一种基于流形切空间插值的可折叠式变体机翼参数化气动弹性建模方法. 首先, 该方法建立若干个典型折叠角下的折叠翼结构有限元模型, 通过流形切空间插值方法建立折叠翼参数化结构动力学模型. 其次, 采用偶极子网格法得到参数化非定常气动力模型, 进而建立气动和结构相互耦合的折叠翼参数化气动弹性模型. 为了验证该参数化建模方法在折叠翼气动弹性分析中的准确性, 本文以一小展弦比折叠翼为研究对象, 从折叠翼自由振动时的参变模态特性、颤振边界预测两方面进行了算例验证, 并与直接计算方法进行了对比, 进一步验证了参数化气动弹性模型的有效性. 研究结果表明, 该参数化气动弹性模型对上述两类问题的计算精度与直接计算方法一致, 并且有着计算效率更高的优势.      

Numerical simulation of flapping‐wing insect hovering flight at unsteady flow

A computational fluid dynamics (CFD) analysis was conducted to study the unsteady aerodynamics of a virtual flying bumblebee during hovering flight. The integrated geometry of bumblebee was established to define the shape of a three‐dimensional virtual bumblebee model with beating its wings, accurately mimicking the three‐dimensional movements of wings during hovering flight. The kinematics data of wings documented from the measurement to the bumblebee in normal hovering flight aided by the high‐speed video. The Navier–Stokes equations are solved numerically. The solution provides the flow and pressure fields, from which the aerodynamic forces and vorticity wake structure are obtained. Insights into the unsteady aerodynamic force generation process are gained from the force and flow‐structure information. The CFD analysis has established an overall understanding of the viscous and unsteady flow around the virtual flying bumblebee and of the time course of instantaneous force production, which reveals that hovering flight is dominated by the unsteady aerodynamics of both the instantaneous dynamics and also the past history of the wing. A coherent leading‐edge vortex with axial flow and the attached wingtip vortex and trailing edge vortex were detected. The leading edge vortex, wing tip vortex and trailing edge vortex, which caused by the pressure difference between the upper and the lower surface of wings. The axial flow, which include the spanwise flow and chordwise flow, is derived from the spanwise pressure gradient and chordwise pressure gradient, will stabilize the vortex and gives it a characteristic spiral conical shape. Copyright © 2006 John Wiley & Sons, Ltd.     

An analytic approach to theoretical modeling of highly unsteady viscous flow excited by wing flapping in small insects

Numerous studies on the aerodynamics of insect wing flapping were carried out on different approaches of flight investigations, model experiments, and numerical simulations, but the theoretical modeling remains to be explored. In the present paper, an analytic approach is presented to model the flow interactions of wing flapping in air for small insects with the surrounding flow fields being highly unsteady and highly viscous. The model of wing flapping is a 2-D flat plate, which makes plunging and pitching oscillations as well as quick rotations reversing its positions of leading and trailing edges, respectively, during stroke reversals. It contains three simplified aerodynamic assumptions: (i) unsteady potential flow; (ii) discrete vortices shed from both leading and trailing edges of the wing; (iii) Kutta conditions applied at both edges. Then the problem is reduced to the solution of the unsteady Laplace equation, by using distributed singularities, i.e., sources/sinks, and vortices in the field. To validate the present physical model and analytic method proposed via benchmark examples, two elemental motions in wing flapping and a case of whole flapping cycles are analyzed, and the predicted results agree well with available experimental and numerical data. This verifies that the present analytical approach may give qualitatively correct and quantitatively reasonable results. Furthermore, the total fluid-dynamic force in the present method can be decomposed into three parts: one due to the added inertial (or mass) effect, the other and the third due to the induction of vortices shed from the leading-and the trailing-edge and their images respectively, and this helps to reveal the flow control mechanisms in insect wing flapping. The project supported by the National Natural Science Foundation of China (10072066) and the Chinese Academy of Sciences (KJCX-SW-LO4, KJCX2-SW-L2)     

NUMERICAL SIMULATION STUDY ON DYNAMIC RESPONSE UNDER RUDDER CONTROL

针对超声速机动飞行器舵面操纵动态响应问题,开展了相应的算法研究,建立了适用于模拟舵面与弹体相对运动及弹体气动力动态响应的非定常计算方法和局部动态网格变形技术. 以方形弹超声速绕流为例,验证了所提出的定常和非定常计算方法. 对方形弹舵面操纵的3种基本过程(脉冲、阶跃和谐波) 进行了数值模拟,获得了舵面操纵下导弹的俯仰运动对操纵的响应过程. 研究结果表明,快速的舵面操纵过程,甚至会导致导弹的俯仰运动失稳.     

An investigation into the effects of unsteady parameters on the aerodynamics of a low Reynolds number pitching airfoil

The growing applications of low Reynolds number (LRN) operating vehicles impose the need for accurate LRN flow solutions. These applications usually involve complex unsteady phenomena, which depend on the kinematics of the vehicle such as pitching, plunging, and flapping of a wing. The objective of the present study is to address the issues related to LRN aerodynamics of a harmonically pitching NACA0012 airfoil. To this end, the influence of unsteady parameters, namely, amplitude of oscillation, d, reduced frequency, k, and Reynolds number, Re, on the aerodynamic performance of the model is investigated. Computational fluid dynamics (CFD) is utilized to solve Navier–Stokes (N–S) equations discretized based on the Finite Volume Method (FVM). The resulting instantaneous lift coefficients are compared with analytical data from Theodorsen’s method. The simulation results reveal that d, k, and Re are of great importance in the aerodynamic performance of the system, as they affect the maximum lift coefficients, hysteresis loops, strength, and number of the generated vortices within the harmonic motion, and the extent of the so-called figure-of-eight phenomenon region. Thus, achieving the optimum lift coefficients demands a careful selection of these parameters.     

基于传递函数法的带多个外挂机翼颤振分析

基于带外挂机翼结构和气动特点，使用带有半解析半数值特性的传递函数方法进行处理．首先，通过机翼的运动微分方程、二元机翼非定常气动力Therdorson 模型、结合外挂挂载处的内力平衡与位移状态条件，得到了三维的带多个外挂大展弦比机翼的颤振微分方程．进而，使用传递函数方法，先将颤振计算方程整理成为状态空间方程形式，结合求解复特征值的方法，完成了带多个外挂大展弦比机翼的动气动弹性稳定性分析．对比已有文献的计算结果以及通过有限元方法进行的仿真结果，证实了文章所提计算方法的准确性和高效性，结合传递函数方法的优势，进一步将文章方法拓展到机翼的固有频率和发散速度求解．文章结尾，分析了外挂数量、外挂质量、转动惯量及位置分布等变量对带多个外挂大展弦比机翼的动气动弹性稳定性的影响．