共查询到20条相似文献,搜索用时 15 毫秒
1.
In this Letter, we present the homotopy perturbation method (shortly HPM) for obtaining the numerical solution of the RLW equation. We obtain the exact and numerical solutions of the Regularized Long Wave (RLW) equation for certain initial condition. The initial approximation can be freely chosen with possible unknown constants which can be determined by imposing the boundary and initial conditions. Comparison of the results with those of other methods have led us to significant consequences. The numerical solutions are compared with the known analytical solutions. 相似文献
2.
3.
4.
He's homotopy perturbation method is used to calculate higher-order approximate periodic solutions of a nonlinear oscillator with discontinuity for which the elastic force term is proportional to sgn(x). We find He's homotopy perturbation method works very well for the whole range of initial amplitudes, and the excellent agreement of the approximate frequencies and periodic solutions with the exact ones has been demonstrated and discussed. Only one iteration leads to high accuracy of the solutions with a maximal relative error for the approximate period of less than 1.56% for all values of oscillation amplitude, while this relative error is 0.30% for the second iteration and as low as 0.057% when the third-order approximation is considered. Comparison of the result obtained using this method with those obtained by different harmonic balance methods reveals that He's homotopy perturbation method is very effective and convenient. 相似文献
5.
A study was made to evaluate the electrothermal efficiency of a DC arc plasma torch and temperature and thermal conductivity
of plasma jet in the torch. The torch was operated at power levels from 4 to 20 kW in non-transferred arc mode. The effect
of nitrogen in combination with argon as plasma gas on the above properties was investigated. Calculations were made from
experimental data. The electrothermal efficiency increased significantly with increase in nitrogen content. The plasma jet
temperature and thermal conductivity exhibited a decrease with increase in nitrogen content. The experiment was done at different
total gas flow rates. The results are explained on the basis of dissociation energy of nitrogen molecules and plasma jet energy
loss to the cathode, anode and the walls of the torch 相似文献
6.
Application of Homotopy Analysis Method for Solving Systems of Volterra Integral Equations 下载免费PDF全文
In this paper, we prove the convergence of homotopy analysis method (HAM).
We also apply the homotopy analysis method to obtain approximate
analytical solutions of systems of the second kind Volterra integral equations.
The HAM solutions contain an auxiliary parameter
which provides a convenient way of controlling the convergence region
of series solutions. It is shown that the solutions obtained by the
homotopy-perturbation method (HPM) are only special cases of the HAM
solutions. Several examples are given to illustrate
the efficiency and implementation of the method. 相似文献
7.
In this paper, the effects of variable thermal conductivity and radiation on the flow and heat transfer of an electrically conducting micropolar fluid over a continuously stretching surface with varying temperature in the presence of a magnetic field are considered. The surface temperature is assumed to vary as a power-law temperature. The governing conservation equations of mass, momentum, angular momentum and energy are converted into a system of non-linear ordinary differential equations by means of similarity transformation. The resulting system of coupled non-linear ordinary differential equations is solved numerically. The numerical results show that the thermal boundary thickness increases as the thermal conductivity parameter S increases, while it decreases as the radiation parameter F increases. Also, it was found that the Nusselt number increases as F increases and decreases as S increases. 相似文献
8.
利用水热法生成了形状规则、粒径均匀的球形ZnO纳米颗粒, 并超声分散于水中, 制备得到稳定的水基ZnO纳米流体. 实验测量水基ZnO纳米流体在体积分数和温度变化时的电导率, 并测试室温下水基ZnO纳米流体在不同体积分数下的热导率. 实验结果表明, ZnO纳米颗粒的添加较大地提高了基液(纯水)的热导率和电导率, 水基ZnO纳米流体的电导率随纳米颗粒体积分数增加呈非线性增加关系, 而电导率随温度变化呈现出拟线性关系; 纳米流体的热导率与纳米颗粒体积分数增加呈近似线性增加关系. 本文在经典Maxwell热导模型和布朗动力学理论的基础上, 同时考虑了吸附层、团聚体和布朗运动等因素对热导率的影响, 提出了热导率修正模型.将修正模型预测值与实验值对比, 结果表明修正模型可以较为准确地计算出纳米流体的热导率.
关键词:
水热法
电导率
热导率
热导模型 相似文献
9.
10.
11.
An attempt has been made to minimize the sources of error involved in the transient probe method for thermal conductivity
determination. Two sensors (thermocouples) are mounted parallel to the needle probe at known distances. This modification
makes it a device for simultaneous conductivity and diffusivity determination. Thermal conductivity and diffusivity for glycerine,
dune sand and mustard seed are determined by this method. Results obtained are compared with those obtained by a calibrated
transient probe for conductivity and by a parallel wire method for diffusivity. Analysis of the results prove it to be a better
instrument over the traditional ones. The technique can also be used as a direct reading device for conductivity and diffusivity
measurements. 相似文献
12.
13.
14.
传统高分子聚合物是良好的电绝缘体和热绝缘体.高分子聚合物具备质量轻、耐腐蚀、可加工、可穿戴、电绝缘、低成本等优异特性.高分子聚合物被广泛应用于各种器件.由于高分子材料的热导率比较低(0.1—0.5 W·m-1·K-1),热管理(散热)面临严峻的挑战.理论及实验工作表明,先进高分子材料可以具有比传统传热材料(金属和陶瓷)更高热导率. Fermi-Pasta-Ulam (FPU)理论结果发现低维度原子链具有非常高的热导率.广泛使用的聚乙烯热绝缘体可以被转变为热导体:拉伸聚乙烯纳米纤维的热导率大约为104 W·m-1·K-1,拉伸的聚乙烯薄膜热导率大约为62 W·m-1·K-1.首先,本文通过理论和实验结果总结导热高分子材料的传热机理研究进展,并讨论了导热高分子聚合物的制备策略;然后,讨论了在传热机制及宏量制备方面,高分子聚合物研究领域所面临的新挑战;最后,对导热高分子的热管理应用前景进行了展望.例如,导热高分子聚合物在耐腐蚀散热片、低成本太阳能热水收集器、可穿... 相似文献
15.
16.
Application of homotopy perturbation method to the RLW and generalized modified Boussinesq equations
In this Letter, He's homotopy perturbation method (HPM) is implemented for finding the solitary-wave solutions of the regularized long-wave (RLW) and generalized modified Boussinesq (GMB) equations. We obtain numerical solutions of these equations for the initial conditions. We will show that the convergence of the HPM is faster than those obtained by the Adomian decomposition method (ADM). The obtained solutions, in comparison with the exact solutions admit a remarkable accuracy. A clear conclusion can be drawn from the numerical results that the HPM provides highly accurate numerical solutions for nonlinear differential equations. 相似文献
17.
Hrishikesh E. Patel T. Sundararajan T. Pradeep A. Dasgupta N. Dasgupta Sarit K. Das 《Pramana》2005,65(5):863-869
Increase in the specific surface area as well as Brownian motion are supposed to be the most significant reasons for the anomalous
enhancement in thermal conductivity of nanofluids. This work presents a semi-empirical approach for the same by emphasizing
the above two effects through micro-convection. A new way of modeling thermal conductivity of nanofluids has been explored
which is found to agree excellently with a wide range of experimental data obtained by the present authors as well as the
data published in literature 相似文献
18.
19.
Thermal mode spectroscopy (TMS) has been recently proposed for accurately measuring thermal diffusivity of solids from a temperature decay rate of a specific thermal mode selected by three-dimensional (anti)nodal information [Phys. Rev. Lett., 117, 195901 (2016)]. In this paper, we find out the following advantages of TMS by use of perturbation analyses. First, TMS is applicable to the measurement of high-thermal diffusivity with a small-size specimen. Second, it is less affected by thermally resistive films on a specimen in the sense that the resistance at the interface does not affect the first-order correction of thermal diffusivity. Third, it can perform doubly accurate measurement of the thermal diffusivity specified at a thermal equilibrium state even if the diffusivity depends on temperature in the sense that the measurement can be performed within tiny temperature difference from the given state and that the decay rate of the slowest decaying mode is not affected by the dependence. 相似文献
20.
A thermal conductivity model for nanofluids including effect of the temperature-dependent interfacial layer 总被引:1,自引:0,他引:1
Chatcharin Sitprasert Pramote Dechaumphai Varangrat Juntasaro 《Journal of nanoparticle research》2009,11(6):1465-1476
The interfacial layer of nanoparticles has been recently shown to have an effect on the thermal conductivity of nanofluids.
There is, however, still no thermal conductivity model that includes the effects of temperature and nanoparticle size variations
on the thickness and consequently on the thermal conductivity of the interfacial layer. In the present work, the stationary
model developed by Leong et al. (J Nanopart Res 8:245–254, 2006) is initially modified to include the thermal dispersion effect due to the Brownian motion of nanoparticles. This model is
called the ‘Leong et al.’s dynamic model’. However, the Leong et al.’s dynamic model over-predicts the thermal conductivity of nanofluids in the case of the flowing
fluid. This suggests that the enhancement in the thermal conductivity of the flowing nanofluids due to the increase in temperature
does not come from the thermal dispersion effect. It is more likely that the enhancement in heat transfer of the flowing nanofluids
comes from the temperature-dependent interfacial layer effect. Therefore, the Leong et al.’s stationary model is again modified
to include the effect of temperature variation on the thermal conductivity of the interfacial layer for different sizes of
nanoparticles. This present model is then evaluated and compared with the other thermal conductivity models for the turbulent convective heat transfer in nanofluids
along a uniformly heated tube. The results show that the present model is more general than the other models in the sense
that it can predict both the temperature and the volume fraction dependence of the thermal conductivity of nanofluids for
both non-flowing and flowing fluids. Also, it is found to be more accurate than the other models due to the inclusion of the
effect of the temperature-dependent interfacial layer. In conclusion, the present model can accurately predict the changes
in thermal conductivity of nanofluids due to the changes in volume fraction and temperature for various nanoparticle sizes. 相似文献