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81.
Esad Tombarević & Igor Vu&scaron anović 《advances in applied mathematics and mechanics.》2011,3(3):354-369
Phase change in ice-water systems in the geometry of horizontal
cylindrical annulus with constant inner wall temperature and adiabatic
outer wall is modeled with an enthalpy-based mixture model. Solidification
and melting phenomena under different temperature conditions are
analyzed through a sequence of numerical calculations. In the case of freezing
of water, the importance of convection and conduction as well as the influence
of cold pipe temperature on time for the complete solidification is examined.
As for the case of melting of ice, the influence of the inner pipe wall
temperature on the shape of the ice-water interface, the flow and temperature
fields in the liquid, the heat transfer coefficients and the rate of melting
are analyzed. The results of numerical calculations point to good qualitative
agreement with the available experimental and other numerical results. 相似文献
82.
Antje Brucks 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(1):33-47
Experimental results are presented on natural convection in a spherical shell of inner and outer radii r
1 = 14 mm and r
2 = 35 mm, with the inner sphere cooled and the outer sphere heated. The fluids filling the shell are two different silicon
oils having Prandtl numbers 39 and 233. Both spheres are fixed together and can be rotated. In the studied regime, both Coriolis
and centrifugal forces become significant. For sufficiently small Rayleigh numbers the resulting flow pattern is axisymmetric
and steady, consisting of a plume descending from the south pole of the inner sphere, and returning in the equatorial regions.
For greater Rayleigh numbers the flow becomes non-axisymmetric, with azimuthal modes m = 2 to 4 arising. We map out the critical Rayleigh number for the onset of these different modes, and consider how they vary
with increasingly rapid overall rotation. Detailed flow measurements are done by converting a standard 2D particle image velocimetry
system into a scanning quasi-3D PIV system. 相似文献
83.
电子直线加速器束流动力学的三维理论和计算 总被引:2,自引:0,他引:2
本文提出了电子直线加速器束流动力学计算的三维理论。将注入的脉冲束流划分为等电荷的环,追踪这些环在三维几何空间的运动,并在六维相空间内讨论束流的性能,给出束流在(r,p_r),(rθ,p_θ),(z,p_Z)三个相平面上的图象以及均方根发射度的数值。本文还介绍了应用三维理论的实例计算结果,并对影响径向发射度的因素作了讨论。 相似文献
84.
The experiments show that the travelling waves strongly vacillate with time due to the topographic forcing. Otherwise in the experiments with the same imposed external conditions but without topography, the baroclinic waves would travel regularly with almost no vacillation. It was found that a prominent feature in the flow with the topographic forcing is large-scale wave vacillation with a period of 127 annulus rotations, which is equivalent to approximately 26 days in the Earth's atmosphere. The experiments also show that the role of topography is to modulate the unstable baroclinic waves both in space and in time.In the second part of this paper, a series of comparative experiments is introduced to study the influences of heat sources and topography on the large-scale baroclinic background flows defined as the flow patterns determined by Ω, the angular velocity of the annulus rotation and △T, the radial temperature difference between the inner and outer walls of the annulus. The flow patterns depend 相似文献
85.
86.
The paper deals with the existence, multiplicity and nonexistence of positive radial solutions for the elliptic system div(|?|p –2?) + λki (|x |) fi (u1, …,un) = 0, p > 1, R1 < |x | < R2, ui (x) = 0, on |x | = R1 and R2, i = 1, …, n, x ∈ ?N , where ki and fi, i = 1, …, n, are continuous and nonnegative functions. Let u = (u1, …, un), φ (t) = |t |p –2t, fi0 = lim‖ u ‖→0((fi ( u ))/(φ (‖ u ‖))), fi∞= lim‖ u ‖→∞((fi ( u ))/(φ (‖ u ‖))), i = 1, …, n, f = (f1, …, fn), f 0 = ∑n i =1 fi 0 and f ∞ = ∑n i =1 fi ∞. We prove that either f 0 = 0 and f ∞ = ∞ (superlinear), or f 0 = ∞and f ∞ = 0 (sublinear), guarantee existence for all λ > 0. In addition, if fi ( u ) > 0 for ‖ u ‖ > 0, i = 1, …, n, then either f 0 = f ∞ = 0, or f 0 = f ∞ = ∞, guarantee multiplicity for sufficiently large, or small λ, respectively. On the other hand, either f0 and f∞ > 0, or f0 and f∞ < ∞ imply nonexistence for sufficiently large, or small λ, respectively. Furthermore, all the results are valid for Dirichlet/Neumann boundary conditions. We shall use fixed point theorems in a cone. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
87.
K.R. Rajagopal 《International Journal of Non》2011,46(9):1167-1176
Using a special model that belongs to a new class of elastic bodies wherein the Cauchy-Green stretch is given in terms of the Cauchy stress and its invariants, within the context of the spherical inflation of a spherical annulus, we show that interesting phenomena like the development of “stress boundary layers” manifest themselves. We consider two cases of boundary value problems, one in which there is a cavity in a sphere and the other in which there is a rigid spherical inclusion in a sphere. We show that in the case of a rigid inclusion, it is possible for a pronounced “stress boundary” layer to develop, in that the values of the stresses within this boundary layer that is adjacent to a spherical inclusion are much larger than external to it. We also show that in the case of both the cavity and a rigid inclusion, the stress concentration is an order of magnitude higher than the increase in the deformation gradient, that is, the stress and the stretch do not scale in a similar manner. While the stress adjacent to a rigid inclusion can be 2500 times the applied radial stress, the maximum stretch, which occurs at the rigid inclusion is about 10. While the variation in the stresses are linear in thin walled annular regions, we find that in thick walled annular regions, the variation of the stresses is non-linear. 相似文献
88.
针对斜井中顶替流体密度差及套管偏心引起的顶替界面突进两相流体掺混严重的问题,考虑斜井密度差引起的驱动力沿周向角和半径的变化,建立了斜井偏心环空稳定顶替界面形状模型,利用该模型分析了密度差对顶替界面形状的影响,得到了不同井斜角及套管偏心条件下顶替流体的最优密度差及变化规律:斜井中顶替界面突进的位置及程度取决于套管偏心与密度差的相对作用,存在合理的密度差使得顶替界面长度最短;最优顶替流体密度差随套管偏心度的增加而增大,随井斜角的增大而减小;固井顶替时在满足压稳防漏的条件下直井所选用的密度差越大越好,水平井所选用的密度差应相对最小。 相似文献
89.
Lucien Guillou 《Transactions of the American Mathematical Society》2008,360(4):2191-2204
Let be a homeomorphism of the open annulus isotopic to the identity and let be a lift of to the universal cover without fixed point. Then we show that admits a Brouwer line which is a lift of a properly imbedded line joining one end to the other in the annulus or admits a free essential simple closed curve.
90.
Jian Deng 《Mathematical Methods in the Applied Sciences》2012,35(13):1594-1600
In this paper, we study a nonlinear elliptic problem in an annulus domain. For which, the nonexistence of nontrivial solutions has been obtained by some authors in star‐shaped domain. Although we note that it may admit non‐trivial solutions if the domain is non‐star shaped. With the use of a variational method, we establish the existence of positive radial solutions in an annulus domain. On the basis of this, we also extend this result to the periodic problem of the corresponding degenerate parabolic problem. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献