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N. BanichukJ. Jeronen P. NeittaanmäkiT. Tuovinen 《Journal of Fluids and Structures》2011,27(7):986-1005
The out-of-plane dynamic response of a moving plate, travelling between two rollers at a constant velocity, is studied, taking into account the mutual interaction between the vibrating plate and the surrounding, axially flowing ideal fluid. Transverse displacement of the plate (assumed cylindrical) is described by an integro-differential equation that includes a local inertia term, Coriolis and centrifugal forces, the aerodynamic reaction of the external medium, the vertical projection of membrane tension, the bending resistance, and external perturbation forces. In the two-dimensional model thus set up, the aerodynamic reaction is found analytically as a functional of the cylindrical displacement, using the techniques of complex analysis. The resulting integro-differential problem is discretized in space with the Fourier-Galerkin method, and integrated in time with the diagonalization method. Examples are computed with physical parameters corresponding to air and some paper materials. The effects of the surrounding fluid on the critical velocity and first natural frequency are investigated, for stationary air, for an air mass moving with the plate, and for some arbitrary axial fluid velocities. The obtained results are applicable for both an ideal membrane and a plate with nonzero bending rigidity. 相似文献
23.
Leon Kaganovskiy 《International Journal of Non》2011,46(1):9-13
In this article, we use a hierarchical panel method for representing vortex sheet surface motion in 3D flow to investigate the oblique collision of two vortex rings. The particles representing the sheet are advected by a regularized Biot-Savart integral with smoothed Rosenhead-Moore kernel. The particle velocities are evaluated by an adaptive treecode algorithm based on Taylor expansions in Cartesian coordinates. The method allowed us to consider late stages of a vortex rings collision, producing a funnel region. Vorticity iso-surfaces evolution is also investigated. 相似文献
24.
We consider closed manifolds that admit a metric locally isometric to a product of symmetric planes. For such manifolds, we prove that the Euler characteristic is an obstruction to the existence of flat structures, confirming an old conjecture proved by Milnor in dimension 2. In particular, the Chern conjecture follows in these cases. The proof goes via a new sharp Milnor–Wood inequality for Riemannian manifolds that are locally a product of hyperbolic planes. Furthermore, we analyze the possible flat vector bundles over such manifolds. Over closed Hilbert–Blumenthal modular varieties, we show that there are finitely many flat structures with nonzero Euler number and none of them corresponds to the tangent bundle. Some of the main results were announced in [M. Bucher, T. Gelander, Milnor–Wood inequalities for manifolds locally isometric to a product of hyperbolic planes, C. R. Acad. Sci. Paris Ser. I 346 (2008) 661–666]. 相似文献
25.
M. Kodu M. AintsT. Avarmaa V. DenksE. Feldbach R. JaanisoM. Kirm A. MaaroosJ. Raud 《Applied Surface Science》2011,257(12):5328-5331
Hydrogen doped MgO films were grown by pulsed laser deposition method. Gaseous hydrogen stored in cavities of milky MgO single crystal targets provided doping in film deposition process. Clear MgO targets without hydrogen were used in the preparation of reference films. The influence of hydrogen doping on firing voltage (FV) of gas discharge and its AC frequency dependence was investigated. According to thermoluminescence experiments, the films grown from milky targets contained two kinds of electron traps with the activation energies of 0.051 and 0.31 eV, while latter traps were absent in reference samples. The 0.31 eV trap was assigned to the hydride ion H− occupying an oxygen vacancy site in MgO crystal structure. Using standard gas mixture (Ne-10% Xe), FVs of hydrogen doped sample showed considerable frequency dependence and were up to 55 V lower in comparison to the reference sample. The FVs of reference sample were shifted 14-28 V to higher values when N2 gas was added to the mixture. The N2 addition lowered the FVs of hydrogen doped sample up to 38 V and almost eliminated the FV frequency dependence. 相似文献
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27.
The 2-dimensional BF theory is both a gauge theory and a topological Poisson σ-model corresponding to a linear Poisson bracket. In [3], Torossian discovered a connection which governs correlation functions of the BF theory with sources for the B-field. This connection is flat, and it is a close relative of the KZ connection in the WZW model. In this Letter, we show that flatness of the Torossian connection follows from (properly regularized) quantum equations of motion of the BF theory. 相似文献
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29.
回转体局部空泡绕流的非线性分析 总被引:12,自引:1,他引:12
基于面元法, 通过在回转体和空泡壁面放置源汇,对回转体定长局部空泡的绕流问题进行了分析和讨论,并提出了求解回转体局部空泡绕流“正问题”的方法。计算结果表明:所给出的方法具有快速收敛的特征,第1次迭代和最终收敛时空泡壁面切向速度的误差不超过5%;随着回转体面元总数N的增加,局部空泡的空泡数σ趋于稳定;通过比较可知,该方法得到的理论估算值与实测值的一致性较好。 相似文献
30.
The paper studies the stress-strain state of a deep cylindrical panel weakened by a hole and subjected to a tensile load at
the outer boundary. A variational difference method is used. A numerical analysis is carried out for an orthotropic panel
with low shear stiffness
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 73–78, May 2006. 相似文献