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The coupled streamfuction–temperature equations governing the Darcian flow and convection process in a fluid-saturated porous enclosure with an isothermal sinusoidal bottom sun face, has been numerically analyzed using a finite element method (FEM). No restrictions have been imposed on the geometrical non-linearity arising from the parameters like wave amplitude (a), number of waves per unit length (N), wave phase (Φ), aspect ratio (A) and also on the flow driving parameter Rayleigh number (Ra). The numerical simulations for varying values of Ra bring about interesting flow features, like the transformation of a unicellular flow to a multicellular flow. Both with increasing amplitude and increasing number of waves per unit length, owing to the shift in the separation and reattachment points, a row–column pattern of multicellular flow transforms to a simple row of multicellular flow. A cycle of n celluar and n+1 cellular flows, with the flow in adjacent cells in the opposite direction, periodically manifest with phase varying between 0 and 360°. The global heat transfer into the system has been found to decrease with increasing amplitude and increasing number of waves per unit length. Only marginal changes in the global heat flux are observed, either with increasing Ra or varying Φ. Effectively, sinusoidal bottom surface undulations of the isothermal wall of a porous enclosure reduces the heat transfer into the system. © 1998 John Wiley & Sons, Ltd. 相似文献
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We consider the combined effect of the magnetic field and heat transfer inside a square cavity containing a hybrid nanofluid(Cu-Al_2O_3-water). The upper and bottom walls of the cavity have a wavy shape. The temperature of the vertical walls is lower,the third part in the middle of the bottom wall is kept at a constant higher temperature,and the remaining parts of the bottom wall and the upper wall are thermally insulated.The magnetic field is applied under the angle γ, an opposite clockwise direction. For the numerical simulation, the finite element technique is employed. The ranges of the characteristics are as follows: the Rayleigh number(10~3≤Ra≤10~5), the Hartmann number(0≤Ha≤100), the nanoparticle hybrid concentration(?_(Al_2O_3),?_(Cu) = 0, 0.025, 0.05),the magnetic field orientation(0≤γ≤2π), and the Prandtl number P_r, the amplitude of wavy cavity A, and the number of waviness n are fixed at P_r = 7, A = 0.1, and n = 3, respectively. The comparison with a reported finding in the open literature is done,and the data are observed to be in very good agreement. The effects of the governing parameters on the energy transport and fluid flow parameters are studied. The results prove that the increment of the magnetic influence determines the decrease of the energy transference because the conduction motion dominates the fluid movement. When the Rayleigh number is raised, the Nusselt number is increased, too. For moderate Rayleigh numbers, the maximum ratio of the heat transfer takes place for the hybrid nanofluid and then the Cu-nanofluid, followed by the Al_2O_3-nanofluid. The nature of motion and energy transport parameters has been scrutinized. 相似文献
75.
非定常流函数涡量方程的一种数值解法的研究 总被引:16,自引:0,他引:16
对非定常流函数涡量方程的数值求解方法进行了改进,其中流函数一阶导数即速度项采用四阶精度的Hermitian公式,对流项由一般二阶精度的中心差分提高到四阶精度离散差分,包含温度方程在内的离散方程组采用ADI迭代方法求得定常解.以无内热体及有一内热体的封闭方腔内自然对流为例,进行了不同瑞利数(Ra)条件下的数值研究.结果表明,该方法推导简单,求解精度高且计算稳定,适用于封闭腔内高瑞利数复杂混合对流的数值模拟. 相似文献
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文内参考IEC61347-2-13的C7章中所定义的外壳发热限制试验的要求,阐述了试验的背景及过程,仪器的选择,以及实施的办法,并举例说明了实验结果及数据分析。 相似文献
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音箱与功放的黄金组合 总被引:1,自引:1,他引:0
从工程实践出发,介绍了音箱与功放的几组搭配方案。分析了各种方案音箱与功放的匹配特性,并阐明了与传统搭配方案相比,各组合方案的优势及其适用场合。 相似文献
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R. J. Goldstein H. D. Chiang V. Srinivasan A. S. Fleischer 《Heat and Mass Transfer》2005,41(11):991-998
An electrochemical technique is used to study local mass transfer coefficients on surfaces of inclined enclosures over the range 1.1×104 < RaH < 1.4×1010 for a nominal Schmidt number of 2280. Scaling with gcos instead of g in the Rayleigh number correlates the data well at low angles of inclination; however, as either the aspect ratio or the angle of inclination increase, the longitudinal density stratification causes the data to deviate from a power law scaling.
相似文献
R. J. GoldsteinEmail: Phone: +1-612-6255552Fax: +1-612-6253434 |
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