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91.
In this paper, the effects of Prandtl number on the steady magneto-convection around a centrally located adiabatic body inside
a square enclosure are numerically investigated. Two-dimensional nonlinear governing equations are discretized using the control
volume method and hybrid scheme. The equations are solved using SIMPLER algorithm. The results are displayed in the form of
streamlines and isotherms when the Rayleigh number varies between 103 and 106, the Hartmann number changes between 0 and 100 and the Prandtl number ranges between 0.005 and 0.1. The ratio of the buoyancy
force to the Lorentz force (Ra/Ha
2) is introduced as an index to compare the contribution of natural convection and magnetic field strength on heat transfer.
The results obtained from numerical modeling show that the Prandtl number has not considerable effect on heat transfer at
low Rayleigh numbers. The effect of magnetic field strength on convection is increased by increasing Prandtl number. The effect
of Prandtl number on the average Nusselt number in the presence of a magnetic field is less than the case without a magnetic
field. 相似文献
92.
Transport in Porous Media - Image-based simulations at pore scale provide direct insight into the impact of the microstructure on flow and transport processes in porous media. Diffusion is an... 相似文献
93.
94.
Saeid Rahimi‐Razin Vahid Haddadi‐Asl Mehdi Salami‐Kalajahi Farid Behboodi‐Sadabad Hossein Roghani‐Mamaqani 《国际化学动力学杂志》2012,44(8):555-569
A new approach was developed to functionalize multiwalled carbon nanotubes (MWCNTs) with a polymerizable methyl methacrylate (MMA) groups, and the structure of functionalized MWCNTs were characterized by FTIR, Raman, XPS, and TEM. Using the strategy of “grafting through,” poly(methyl methacrylate) (PMMA) chains were grafted onto the surface of MWCNTs during the in situ synthesis of MWCNT/PMMA nanocomposites over reversible addition‐fragmentation chain transfer (RAFT) polymerization. Kinetics of RAFT‐mediated polymerization of MMA in the presence of MMA‐grafted MWCNTs was studied by using gas chromatography and gel permeation chromatography. To further study, attached polymers were detached and their molecular characteristics were compared to freely formed chains. Results of kinetic studies showed that the utilized commercial chain transfer agent strictly reduced the rate of polymerization as well as relatively controlled molecular weights and narrow molecular weight distributions of free chains. MWCNTs showed a radical activity, retarding the polymerization and reducing the rate of reaction. The effect of MWCNTs concentrations on molecular weights and polydispersity indexes (PDI) was different at the surface and in the bulk. The molecular weights of free chains increased, and the PDI was decreased with increasing MWCNTs. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 555–569, 2012 相似文献
95.
Mohammad Solimannejad Farshideh Hasanvand Jamshidi Saeid Amani 《Structural chemistry》2011,22(1):193-199
Ab initio calculations at MP2/6-311++G(d,p) computational level were used to analyze the interaction between a molecule of
the hydroperoxyl radical with 1 up to 4 molecules of ammonia. Three minima were found for 1:2 and 1:4 complexes of HOO and
NH3. Two complexes were located as minima on the potential energy surface of 1:3 complexes. Red shifts of the OH stretching frequency
upon complex formation in the range between 560 and 1,116 cm−1 are predicted. Cooperative effect in terms of stabilization energy is calculated for the studied clusters. The cooperative
effect is increased with the increasing size of studied clusters. The Quantum Theory Atoms in Molecules (QTAIM) theory was
also applied to explain the nature of the complexes. 相似文献
96.
97.
Saeid Sadeghnejad Mohsen Masihi Akbar Shojaei Mahmoudreza Pishvaie Peter R. King 《Transport in Porous Media》2012,92(2):357-372
The connectivity of high conductivity pathways in geological formations depend on the spatial distribution of geological heterogeneities
that may appear on various length scales. Appropriate modeling of this is crucial within in hydrology and petroleum systems.
The approach taken in this study is to use percolation theory to quantify the connectivity, hydraulic conductivity, and breakthrough
time behavior between an injector and a producer within such systems. In particular, a three-dimensional overlapping sandbody
model is considered which assumes that the geological formation can be split into either conductive flow units (i.e., good
sands) or non-conductive units (i.e., poor sands). The results are the master curves for the formation connectivity as well
as the hydraulic conductivity and breakthrough time. The percolation approach is then validated against Burgan offshore reservoir
dataset which reveal good matches when compared with the results obtained from computationally expensive conventional methods. 相似文献
98.
99.
Mohammad Ebrahim Torki Mohammad Taghi Kazemi Junuthula N. Reddy Hassan Haddadpoud Saeid Mahmoudkhani 《Journal of sound and vibration》2014
In this paper, flutter of functionally graded material (FGM) cylindrical shells under distributed axial follower forces is addressed. The first-order shear deformation theory is used to model the shell, and the material properties are assumed to be graded in the thickness direction according to a power law distribution using the properties of two base material phases. The solution is obtained by using the extended Galerkin's method, which accounts for the natural boundary conditions that are not satisfied by the assumed displacement functions. The effect of changing the concentrated (Beck's) follower force into the uniform (Leipholz's) and linear (Hauger's) distributed follower loads on the critical circumferential mode number and the minimum flutter load is investigated. As expected, the flutter load increases as the follower force changes from the so-called Beck's load into the so-called Leipholz's and Hauger's loadings. The increased flutter load was calculated for homogeneous shell with different mechanical properties, and it was found that the difference in elasticity moduli bears the most significant effect on the flutter load increase in short, thick shells. Also, for an FGM shell, the increase in the flutter load was calculated directly, and it was found that it can be derived from the simple power law when the corresponding increase for the two base phases are known. 相似文献
100.
Quantum calculations at the MP2/cc-pVTZ have been used to examine 1:1 and 1:2 complexes between O2NX (X = Cl, Br) with HCN and HNC moieties. The interaction of the lone pair of the HCN(HNC) with the σ-hole and π-hole of O2NX molecules and hydrogen bonding between lone pairs of X and O of O2NX with H of HCN and HNC have been considered in 1:1 complexes. The 1:1 complexes can easily be differentiated using the stretching frequency of the N–X bond. Thus, those complexes with σ-hole and H···O2NX interactions show a blue shift of the N-X bond stretching while a red shift is observed in the complexes along the π-hole and H···XNO2 interactions. In the 1:2 complexes, the cooperative and diminutive energetic effects have been analyzed using the many-body interaction energies. The nature of the interactions has been characterized with the Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) methodologies. Stabilization energies of 1:1 and 1:2 complexes including the variation of the zero-point vibrational energy (ΔZPVE) are in the range 3–9 kJ mol?1 and 21–40 kJ mol?1, respectively. 相似文献