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91.
92.
M. Turkyilmazoglu 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2008,59(4):676-701
In this study a theoretical approach is pursued to investigate the effects of suction and blowing on the structure of the
lower branch neutral stability modes of three-dimensional small disturbances imposed on the incompressible von Karman’s boundary
layer flow induced by a rotating-disk. Particular interest is placed upon the short-wavelength, non-linear and nonstationary
crossflow vortex modes developing within the presence of suction/blowing at sufficiently high Reynolds numbers with reasonably
small scaled frequencies. Following closely the asymptotic framework introduced in [1], the role of suction on the non-linear
disturbances of the lower branch described first in [2] for the stationary modes only, is extended in order to obtain an understanding
of the behavior of non-stationary perturbations. The analysis using the rational asymptotic technique based on the triple-deck
theory enables us to derive initially an eigenrelation which describes the evolution of linear modes. The asymptotic linear
modes calculated at high Reynolds number limit are found to be destabilizing as far as the non-parallelism accounted by the
approach is concerned, and they compare fairly well with the numerical results generated directly by solving the linearized
system with the usual parallel flow approximation. An amplitude equation is derived next to account for the effects of non-linearity.
Even though the form of this equation is the same as that of found in [2] for no suction, it is under the strong influence
of suction and blowing. This amplitude equation is shown to be adjusted by a balance between viscous and Coriolis forces,
and it describes the evolution of not only the stationary but also the non-stationary modes for both suction and injection
applied at the disk surface. A close investigation of the amplitude equation shows that the non-linearity is highly destabilizing
for both positive and negative frequency waves, though finite amplitude growth of a disturbance having positive frequency
close to the neutral location is more effective at destabilization of the flow under consideration. Finally, a smaller initial
amplitude of a disturbance is found to be sufficient for the non-linear amplification of the modes in the case of suction,
whereas a larger amplitude is required if injection is active on the surface of the disk. 相似文献
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考虑非饱和土基质吸力作用的土石坝渗流分析 总被引:1,自引:0,他引:1
传统的渗流分析主要考虑饱和区而忽略非饱和区内的渗流,本文首先对影响非饱和土渗流特性的重要物理量基质吸力进行了分析,阐述了其形成机理并推出其理论计算公式,然后在考虑基质吸力的作用下,基于饱和.非饱和渗流计算原理,采用有限元法考虑了渗流场非饱和区的影响,并以各向同性均质坝和心墙土石坝为算例,进行了计算分析。算例表明,由于基质吸力产生的虹吸作用,使得浸润线上部的非饱和区内也存在着连续的水流,否定了传统分析中浸润线是最上部流线的假设,通过分析这种水流的特点,定性的得出其对土石坝渗流稳定性的影响,对土石坝渗流分析具有一定的指导意义。 相似文献
96.
陶明德 《应用数学和力学(英文版)》1987,8(9):847-852
In this paper, a nonlinear partial differential equation governing a change of shoreline is derived, its solution is expanded as an asymptotic series in a small parameter. Then the Green function is obtained by means of Fourier transform and the solution is expressed using the Green function. The results obtained show that Delta growth is asymmetrical due to sand input from river and longshore current. It tries to explain asymmetrical growth of the Delta of the Changjiang River. 相似文献
97.
低雷诺数下附面层组合抽吸方案对压气机特性影响的研究 总被引:1,自引:0,他引:1
为了分析附面层抽吸流动控制对低雷诺数下压气机特性的影响,本文采用数值方法模拟了低雷诺数下附面层组合抽吸方案对NASA Rotor 37跨音速压气机性能和稳定性的影响特点及作用机理。通过在该压气机转子叶片吸力面和机匣上分别设计附面层抽吸槽,探讨了组合抽吸方案对低雷诺数下(H=20km)压气机性能和稳定性的影响。结果表明:采用组合抽吸方案后,压气机峰值效率提高约1.3%;压气机最大增压比提高约2.5%;压气机转子的近失速点流量减小约14.6%。进一步分析作用机理发现,组合抽吸槽有效抑制了附面层径向涡向叶顶的运动和聚集,使叶顶附面层分离区减少约70%从而有效改善了压气机的流场特性。 相似文献
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In this article, we consider the effects of double diffusion on magnetohydrodynamics (MHD) Carreau fluid flow through a porous medium along a stretching sheet. Variable thermal conductivity and suction/injection parameter effects are also taken into the consideration. Similarity transformations are utilized to transform the equations governing the Carreau fluid flow model to dimensionless non-linear ordinary differential equations. Maple software is utilized for the numerical solution. These solutions are then presented through graphs. The velocity, concentration, temperature profile, skin friction coefficient, and the Nusselt and Sherwood numbers under the impact of different parameters are studied. The fluid flow is analyzed for both suction and injection cases. From the analysis carried out, it is observed that the velocity profile reduces by increasing the porosity parameter while it enhances both the temperature and concentration profile. The temperature field enhances with increasing the variable thermal conductivity and the Nusselt number exhibits opposite behavior. 相似文献