Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
41
4
2014
Experimental Characterization of the Velocity Field in Turbulent Oxy-Flame of a Coaxial Burner
283-295
10.1615/InterJFluidMechRes.v41.i4.10
Z.
Riahi
Centre de Recherches et des Technologies de l'Energie Borj Cedria Hammam-Lif, Tunisie
Mohamed Ali
Mergheni
CORIA UMR 6614 CNRS - Université et INSA de Rouen, France; (LESTE) Ecole Nationale d'Ingenieurs de Monastir; Ecole Superieure des Sciences et Technologie de Hammam Sousse, Sousse, Tunisie
S.
Yon
CORIA UMR 6614 CNRS - Université et INSA de Rouen Rouen, France
J. C.
Sautet
CORIA UMR 6614 CNRS - Université et INSA de Rouen, Avenue de l'Université, BP 12, 76801 Saint Etienne du Rouvray, Cedex, France
Gilles
Godard
CORIA UMR 6614 CNRS - Université et INSA de Rouen Rouen, France
C.
Gobin
CORIA UMR 6614 CNRS - Université et INSA de Rouen Rouen, France
Sassi Ben
Nasrallah
Laboratoire d'Études des Systèmes Thermiques et Énergétiques, Ecole Nationale d'Ingénieurs
de Monastir, Monastir 5019 Tunisie
Most industrial applications consuming a much primary energy, such fuel and gas, used different technologies of burners. The thermal efficiency and polluting
emissions depends on the burner nozzle, on the fuel type and oxidant type (air or pure oxygen). This article is interested by the dynamic study in a coaxial burner consisting by two coaxial circular jets: a central jet to inject natural gas and the annular jet for pure oxygen injection. The aim of this work is the experimental study of two free coaxial jets with flame disposed in ambient air
and to have the effect of varying equivalence ratio on the flow structure. This study carried in three configurations; two configurations made in lean combustion mode (Φ = 0.65, Φ = 0.8) and the stoichiometric configuration (Φ = 1).
The variation in the amount of oxygen in the combustion reaction affects on the longitudinal velocity, on the transversal velocity and on the turbulent fluctuation.
These parameters are very important and affect directly on the flame structure. The reduction of equivalence ratio leads to increased of longitudinal and transverse
velocity and promotes the fluctuation in interaction zone between natural gas and oxygen. At the stoichiometric reaction, the turbulent intensity represents
a maximum in the mixing zone. This maximum increases when the height above the burner increases.
Kinematics of Horseshoe Vortex in a Scour Hole around Two Eccentric Triangular Piers
296-317
10.1615/InterJFluidMechRes.v41.i4.20
SUBHASISH
DAS
Jadavpur University
Sudipta
Ghosh
School of Water Resources Engineering, Jadavpur University, Kolkata, West Bengal, India
Asis
Mazumdar
School of Water Resources Engineering, Jadavpur University, Kolkata 700032, India
Flow pattern at single pier has been extensively studied by many investigators, but very little work is available on turbulent flow pattern around piers placed in close proximity. The work explained in this research is concerned with experimental study of the horseshoe vortex flow pattern and characteristics in a local equilibrium scour around a set of two equilateral triangular piers (sides facing the approaching flow) placed in longitudinal direction to the flow with an eccentricity (transverse distance). The eccentricity and longitudinal spacing (spacing along
the flow) between two piers were kept constant. Instantaneous three-dimensional velocities were determined by using an acoustic Doppler velocimeter. The contours
and distributions of the time-averaged velocity components, turbulence intensities and turbulence kinetic energy are illustrated at different azimuthal planes:
0, 45, −45, 90 and −90°. Velocity vectors presented from time-averaged velocity fields are used to show further flow features. The vorticity and circulation of the horseshoe vortex are computed by using forward difference technique of computational hydrodynamics and Stokes theorem, respectively. The pier arrangement and the interference between the horseshoe vortex of the rear pier and wake vortex of the front pier play a significant role in the creation and formation of the greater scour depth at the eccentric rear piers. Due to the existence of bluff body,
the pressure drag becomes much higher than the skin friction drag. This phenomenon was examined during this testing. Vortex strength of the eccentric rear pier was observed always higher in the inline front pier.
Application of Computational Fluid Dynamics for Two-Phase Gas − Newtonian Liquid Flow through U-Bend
318-336
10.1615/InterJFluidMechRes.v41.i4.30
Tarun Kanti
Bandyopadhyay
Department of Chemical Engineering, NIT Agartala, Jirania, Agartala, Tripura West, 799046,
India
Sudip Kumar
Das
Butler University
Experimental investigation has been carried out in order to study the air-water flow through four different U-bends. The internal diameter of the tubes and the bends was 0.01905 m, radius of curvature (mm) is 0.06 ≤ Rb ≤ 0.20, water flow rate Ql · 10−4(m3/s) is 2.000 to 4.65 and air flow rate is Qg · 10−5(m3/s) is 5.936 to 56.1189. Numerical modeling is carried using Fluent 6.3 software to find its applicability. The CFD simulations are carried out using mixture k−ε model for air-water flow through different U-bends. We are using k−ε model as the water flow through the bend is in turbulent condition. The simulated results predicts the flow structure, cell Reynolds number, static pressure, shear stress, shear strain, turbulent kinetic energy, turbulent intensity, dissipation losses, vorticity, helicity and volume fraction for two-phases. The CFD results show the very good agreement with the experimental values.
Numerical Investigation of Mechanical Tabs Effect on a Turbulent Free Circular Jet
337-352
10.1615/InterJFluidMechRes.v41.i4.40
Mohammed
Boulenouar
Laboratory of Sciences and Maritime Engineering, University of Sciences and Technology–Mohamed Boudiaf–Oran BP 1505 El M'Naouer, Algeria
Omar
Imine
Laboratory of Aeronautical Systems and Propulsion, University of Sciences and Technology–Mohamed Boudiaf–Oran BP 1505 El M’Naouer, Algeria
Noureddine
Boualem
Composite Structures and Innovative Materials Laboratory (LSCMI), Mechanical Engineering Faculty University of Science and Technology Oran Mohamed Boudiaf Oran, Algeria
Tayeb
Yahiaoui
Laboratoire d'Aéronautique et Systèmes Propulsifs, Départment de Génie Mécanique,
Université des Sciences et de la Technologie d'Oran Mohamed Boudiaf, USTO-MB, Oran,
Algérie
Numerical simulation of low Reynolds turbulent free jet issuing from circular nozzles with and without tabs, using the Shear Stress Transport (SST) k−ω
model has been carried out. First, the numerical model validation has been performed by comparing computed results with Particle Image Velocimetry (PIV) measurements for the circular nozzle without tabs. The obtained results show
reasonable agreement, principally for parameters such as centerline longitudinal velocity, longitudinal fluctuating velocity, and volumetric flow rate. Secondly, the
tested numerical model has been applied for tabbed jet and results were compared with those of the circular jet without tabs. It is showed that the turbulent jet flow is modified by the presence of tabs. Also, it is found that the circular jet with tabs has better mixing performance compared to the circular jet without tabs. With these results, the tested numerical model can be considered as an efficient and
costless mean for optimizing circular nozzle geometry for Heating Ventilation Air Conditioning (HVAC) applications.
Analytical and Numerical Investigations of Physical Dimensions of Natural Convection Flow on a Vertical Heated Plate
353-367
10.1615/InterJFluidMechRes.v41.i4.50
Ali S.
Alzwayi
Systems, Power & Energy Research Division, School of Engineering, University of Glasgow,Glasgow, G12 8QQ, UK
Manosh
Paul
University of Glasgow
The analytical and numerical results of a natural convection boundary layer flow on a vertical heated plate are presented. We specifically look at the effects of heat flux and plate temperatures on the development of a physical boundary layer along its heated surface. The plate temperature and heat flux examined are 9 ≤ T(°C) ≤ 100 and 50 ≤ qP ≤ 553 (W/m2) respectively. The results show that the variation in plate temperature has a significant effect on transition and the difference between the temperature of the air and the plate has even more effect on the transition particularly when TP ≤ 60°C. The transition on the constant heat-flux plate is less affected by air temperature and mostly depends on the quantity of heat flux. A Realizable k−ε turbulent model with an enhanced wall function is employed in a numerical simulation, and important results, including
the distribution of maximum velocity, and kinetic energy and its production along the heated plate, are examined for a selection of air temperatures. The results indicate that the production of kinetic energy reaches its peak at the transition stage, and both the velocity and turbulent kinetic energy increase sharply at the turbulent flow regime. Analytical and numerical results are compared with those of various relevant experimental studies and found to be in good agreement with them.
Combined Effects of Piezo-Viscosity and Couple Stress Fluids on Squeeze Film between Circular Plates
368-378
10.1615/InterJFluidMechRes.v41.i4.60
Udaya Pratap
Singh
Rajkiya Engineering College, Sonbhadra, Uttar Pradesh
In high pressure fluid flows applications such as fluid film lubrication, microfluidics and geophysics, the piezo-viscous effect i. e., viscosity-pressure dependence plays an important role. In the present theoretical investigation,
the combined effects of piezo-viscous dependency and non-Newtonian couple stresses on the performance of circular plate squeeze film bearings have been investigated
using Stokes Micro-continuum theory of couple stress fluids together with the exponential variation of viscosity with pressure. Analytic solution for film pressure is obtained using small perturbation analysis. The numerical results
for pressure and load capacity with different values of viscosity-pressure parameter are calculated and compared with iso-viscous couple stress and Newtonian lubricants. Due to piezo-viscous effect, enhanced pressure, increased load capacity and longer response time is observed in the analysis.