Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
40
5
2013
A Phase-Field Approach for Liquid-Liquid Flow Simulations
373-381
Enrico
Stalio
Dipartimento di Ingegneria "E. Ferrari", Università di Modena e Reggio Emilia, 41125 Modena, Italy
Marzio
Piller
Department of Engineering and Architecture, University of Trieste, via A. Valerio 10, 34127
Trieste (TS), Italy
A phase-field approach is presented for the numerical simulation of two-phase forced flow in channels. The difference in physical properties of the two components is handled following a quasi-incompressible approach (Lowengrub
and Truskinovsky [16]). The axisymmetric form of the Navier − Stokes and Cahn − Hilliard equations system is solved for a narrow pipe of radius R = 1 mm, where buoyancy effects are neglected. Results of three simulations for the evolution of spherical and elongated bubbles are reported.
Stability Analysis of Viscoelastic Fluid in Porous Medium
382-390
Pardeep
Kumar
Department of Mathematics, International Centre for Distance Education and Open Learning (ICDEOL), Himachal Pradesh University, Shimla-171005, India
An attempt has been made to investigate the thermal instability of Maxwellian heterogeneous viscoelastic fluid layer through porous medium. Following the linearized stability theory and normal mode analysis, the dispersion
relation is obtained. For stationary convection, the medium permeability and density distribution are found to have destabilizing effect. The dispersion relation is also analyzed numerically. Sufficient conditions for non-existence of overstability are also obtained.
On Exchange of Stabilities in Ferromagnetic Convection in a Rotating Porous Medium
391-404
Jyoti
Prakash
Department of Mathematics and Statistics, Himachal Pradesh University, Summer Hill,
Shimla-171005, India
In the present paper, first of all, it is proved that the 'principle of the exchange of stabilities' is not, in general valid, for the case of free boundaries, in ferromagnetic
convection, in porous medium in the presence of a uniform vertical magnetic field and uniform rotation about the vertical axis and then a sufficient condition is derived for the validity of this principle.
Forced Convective Heat Transfer Study of Paraffin Slurry Flowing in a Vertical Rectangular Channel
405-419
Mohamed Najib
El Boujaddaini
CETHIL UMR 5008 / INSA-UCBL-CNRS / Bat Sadi Carnot, Villeurbanne,France; Laboratoire d'Energetique , Mécanique des Fluides et Sciences des Matériaux, Faculté des Sciences / BP2121-93000,Tétouan, Maroc
Abdelaziz
Mimet
Laboratoire d'Energetique , Mécanique des Fluides et Sciences des Matériaux, Faculté des Sciences / BP 2121 -93000, Tétouan, Maroc
Philippe
Haberschill
CETHIL UMR 5008 / INSA - UCBL - CNRS / Bat Sadi Carnot, 20 Avenue Albert Einstein, 69621, Villeurbanne Cedex, France
Paraffin slurry is one kind of secondary refrigerants, which is promising to be applied into air-conditioning or latent-heat transportation systems as a thermal storage or cold carrying medium for energy saving. It is a solid-liquid two
phase mixture which has high latent heat and good fluidity. In this paper, the heat transfer characteristics of paraffin slurry were investigated in a vertical rectangular
stainless steel channel under different solid mass fractions and mass flow rates with constant wall temperature. A continuum model has been developed taking into account the energy balances of the phase change material (PCM) solid particles and the mixture as well to describe the thermal behaviour of the slurry. Local heat transfer coefficients were investigated and analyzed, and correlations of local
and average Nusselt numbers in the form of power function were summarized, the error with numerical results was within ±10 %. The good agreement between calculated and experimental results improves the validity of the mixture model used to describe the two phase flow behaviour of the stabilized paraffin slurry in the channel.
The Flow Field Induced by a Blast Wave Traversing on a Convex Curved Wall
420-428
A. O.
Muritala
Department of Mechanical Engineering, Obafemi Awolowo University Ile-Ife, Nigeria
C.
Law
School of Mechanical, Industrial and Aeronautical Engineering, University of the Witwatersrand Witwatersrand, South Africa
B. W.
Skews
School of Mechanical, Industrial and Aeronautical Engineering, University of the Witwatersrand Witwatersrand, South Africa
Olubunmi T.
Popoola
Department of Mechanical and Materials Engineering, Florida International University, Miami, Florida 33174, USA
This work studied the flow field induced by a blast wave traversing on a circular geometry. This was with a view to explaining the transient development of the complex flow structure that is formed when there is explosion that propagates a shock wave. Tests were conducted in a large scale experimental shock tube on a 200 mm diameter wall using a range of incident shock Mach numbers between 1.4 and 1.6. Schlieren optical system was set up to capture the images of interaction and the pressure history were recorded at different locations along the curvature. The results show series of lambda-shaped shocklets that later coalesced into a second shock. A shear layer evolved from the separation point and terminated by a vortex which enlarges as the diffraction process progresses. The flow later becomes unstable with two turbulent patches identified around the separation point. The present study gives information that is very useful in designing devices for the attenuation of blast waves.
Numerical Study of Lobe Shape on Performance of Forced Mixing Exhaust
429-445
Xie
Yi
The State Key Laboratory of Mechanical Transmission, School of Mechanical Engineering, Chongqing University Chongqing, China
Gao
Xin
School of Mechanical Engineering, Chongqing University Chongqing, China
Ruan
Deng-Fang
School of Mechanical Engineering, Chongqing University Chongqing, China
Geometric models of lobed mixer nozzle with different lobe shapes are created. The Reynolds Averaged Naviers−Stokes (RANS) equations with standard k-ε turbulence model are selected as controlling equations to simulate the corresponding flow field, and they are discretized by the Arbitrary Lagrange Euler method. The simulation results are compared with the splitter mixer nozzle, and the comparison outcomes indicate that lobed mixer can not only greatly increase the mixing between the core and fan flow, but also reduce the noise of exhaust. Besides, although energy loss of lobed mixer is bigger than splitter mixer, the difference of total pressure recovery coefficient and thrust coefficient between lobed mixer nozzle and splitter mixer nozzle is small. Among different lobe shape models, the straight cut and elliptical cut at the lobe exit can enhance the mixing, and their energy loss is slightly bigger than the corresponding model without cut. When the guide lines of lobed mixer is modified, thermal mixing efficiency declines, but the total pressure recovery coefficient increases. In addition, as lobe shape changes, although thrust coefficient varies, the difference between maximum and minimum thrust coefficient is less than 1 %. As for the overall sound pressure level, near the region of jet core, it gradually declines, as thermal mixing efficiency increases; at the cross section of nozzle exit, it varies little as lobe shape changes.
Mathematical Analysis of Newly Designed Ferrofluid Lubricated Double Porous Layered Axially Undefined Journal Bearing with Anisotropic Permeability, Slip Velocity and Squeeze Velocity
446-454
Rajesh C.
Shah
Department of Applied Mathematics, Faculty of Technology and Engineering, The M. S. University of Baroda Vadodara - 390 001, Gujarat State, India
Dilip B.
Patel
Department of Mathematics, Sankalchand Patel College of Engineering Visnagar - 384 315, Gujarat State, India
The aim of this paper is to analyze theoretically the performance of newly designed double porous layered axially undefined journal bearing lubricated with ferrofluid considering combined effects of anisotropic permeability of the double layered porous facing, slip velocity at the interface of the porous matrix and film region, and squeeze velocity. Ferrofluid [1] is used because it generates body force µ0 (M · ∇)H in the presence of magnetic field H; µ0, M are free space permeability and magnetization vector respectively. Porous layer is because of having self lubricating property of the bearing. Expressions are obtained for dimensionless pressure and load carrying capacity for this newly designed journal bearing. The values of dimensionless load capacity are computed using ferrofluid as lubricant and compared it with the values which are obtained using conventional lubricant (that is, without using ferrofluid). From the results, we say that with using ferrofluid as lubricant, the dimensionless load capacity increase up to 206.86 %. Thus, with the use of ferrofluid as lubricant, it is found that the bearing performance is much better than that of a conventionally lubricated bearing.
Electrohydrodynamic Kelvin − Helmholtz Instability of Cylindrical Interface through Porous Media
455-467
Neeraj
Dhiman
Department of Mathematics Graphic Era University Dehradun, Uttarakhand, India
Mukesh
Awasthi
Babasaheb Bhimrao Ambedkar University, Lucknow
M. P.
Singh
KLDAV (PG) College, Roorkee Haridwar, Uttarakhand, India
The effect of saturated porous bed structure on the linear analysis of Kelvin− Helmholtz instability of cylindrical interface has been carried out, using viscous potential flow theory. The fluids are subjected to be uniform electric field which is acting in the axial direction. The fluids are considered to be viscous and incompressible with different kinematic viscosities. In viscous potential flow theory, viscosity enters through normal stress balance and tangential stresses are not considered. A dispersion relation that accounts for the axisymmetric waves has been obtained and stability criterion has been given in terms of relative velocity. Various graphs have been drawn to show the effect of various physical parameters such as porosity and permeability of medium, viscosity ratio, upper fluid fraction on the stability of the system. It is observed that axial electric field has stabilizing effect while porous media has destabilizing effect on the stability of the system.