Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
35
4
2008
The Spatial Inhomogeneity of Turbulence Over Large Relative Random Roughnesses in Open Channel Flow
299-317
10.1615/InterJFluidMechRes.v35.i4.10
Sevket
Cokgor
Istanbul Technical University, College of Civil Engineering, Department of Hydraulics, 34469, Maslak, Istanbul, Turkey
Ismail
Albayrak
Department of Engineering, University of Aberdeen, Aberdeen AB24 3UE, UK
Beyhan
Yegen
Istanbul Technical University, College of Civil Engineering, Department of Hydraulics, 34469, Maslak, Istanbul, Turkey
Turbulent boundary layers over roughness elements have considerable engineering interest in several disciplines, e. g., mechanical, aerospace, environmental and hydraulic engineering. In the work presented attention was focused on turbulence characteristics over relatively large random roughness. The measurements were obtained with three component acoustic Doppler (ADV) and two component laser Doppler (LDA) velocimeters. The turbulence statistics associated with the vertical velocity component are emphasized including mean vertical velocities, root mean square (RMS) distributions and mean vertical momentum fluxes. The process of flow rush into the hole between roughness elements is investigated. It was found that the vortices, which form in the holes between the roughnesses are key to the process. Flow visualization observations and data analysis are a sign of the vortices entrained through the hole at the downstream side and sucked out from hole through at the upstream side by the main flow.
Theoretical Study of the Forced Hydraulic Jump by Positive Step in a Triangular Channel
318-325
10.1615/InterJFluidMechRes.v35.i4.20
Mahmoud
Debabeche
Research Laboratory in Subterranean & Surface Hydraulics, Department of Hydraulic, University of Biskra, Algeria
Moussa
Lakehal
Department of Hydraulic, University of Oum El Bouaghi, Algeria
Naim
Mansri
University of Biskra, Biskra, Algeria
Bachir
Achour
Research Laboratory in Subterranean & Surface Hydraulics, Department of Hydraulics, University of Biskra, Biskra, Algeria
The sequent depths ratio of a forced hydraulic jump by positive step, evolving in a horizontal triangular channel of 90° central angle, is theoretically analyzed. A general relationship is obtained for the sequent depths ratio as function of the inflow Froude number and the relative step height. Experimental data are used to correct the theoretical obtained relationship. The positive step gets the stability of the jump, its efficiency and compactness. The relationship obtained is recommended of designing irrigation ditches.
Mixed Convection Boundary-Layer Flow Along a Vertical Stretched Surface with Uniform Surface Mass Transfer
326-339
10.1615/InterJFluidMechRes.v35.i4.30
M. A.
Hossain
COMSATS Institute of Information Technology, Department of Mathematics, Islamabad, Pakistan
Saleem
Ashgar
Department of Mathematical Sciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
R.S.R.
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
In the present study, mixed convection heat transfer behavior of a viscous and incompressible fluid in the laminar boundary layer flow over a permeable vertical continuously stretching surface is investigated. The effects of buoyancy, permeability of the surface, and the stretching speed of the surface on the flow and heat transfer characteristics are considered. By introduction of one parametric group theory, the governing equations are reduced to coupled nonsimilarity equations. Exact solutions of these equations are obtained using the Keller box method. The results are then compared with those obtained by the perturbation method for small and large values of the local transpiration parameter, ξ. The numerical results, which are obtained for the flow and heat transfer characteristics, reveal the influences of the physical parameters such as the Prandtl number, Pr, the Richardson number, Ri, and the power law index, m, for the surface velocity as well as the surface temperature.
Free Convection Flow and Heat Transfer Along a Heated Vertical Slotted Surface
340-353
10.1615/InterJFluidMechRes.v35.i4.40
M. A.
Hossain
COMSATS Institute of Information Technology, Department of Mathematics, Islamabad, Pakistan
Saleem
Ashgar
Department of Mathematical Sciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
R.S.R.
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
In the present paper, the free convection flow of a viscous incompressible fluid past a uniformly heated vertical slotted surface has been investigated numerically. The equations governing the flow and heat transfer are reduced to local nonsimilarity equations, treating ξ = λx/Grx1/4, where Grx is the local Grashof number) as a local slip variable. The transformed boundary layer equations are solved numerically using an implicit finite difference method for values of ξ in the interval [0, ∞). Asymptotic solutions are also obtained for both smaller and larger values of ξ, for the local skin friction, and local rate of heat transfer, and are found to be in excellent agreement with those obtained by the finite difference solutions for all ξ. From the present analysis, it is observed that an increase in ξ leads to increase the skin friction as well as heat transfer at the surface, which then leads to its asymptotic value that corresponds to the problem of natural convection along a nonisothermal vertical surface for a fluid of any Prandtl number.
Primary Liquid Breakup in a Pressure-Swirl Atomizer
354-364
10.1615/InterJFluidMechRes.v35.i4.50
Abhijit
Kushari
Department of Aerospace Engineering, IIT Kanpur, Kanpur-208 016, Uttar Pradesh, India
P.
Barman
Indian Institute of Technology, Department of Aerospace Engineering, Kanpur, India
In the present study, an attempt has been made to investigate the primary at-omization process of a simplex pressure-swirl atomizer and the effect of various forces on conical liquid sheet disintegration. This paper describes the effect of liquid flow Reynolds number on the liquid jet breakup length and the spray cone angle. This study also examines qualitatively the effect of destructive and consolidating forces on the liquid sheet break up and concludes that the ratio of kinetic energy causing spray breakup and consolidating energy plays a critical role in the transformation of the tulip shaped liquid bulb at low Reynolds number into a fully developed hollow cone spray structure at high Reynolds number. With the increase in the kinetic energy, i. e., the inertial forces, the consolidating influence becomes weaker and weaker causing early breakup of the jet.
Numerical Solution to the MHD Flow of Micropolar Fluid Between Parallel Porous Plates
365-373
10.1615/InterJFluidMechRes.v35.i4.60
Darbhasayanam
Srinivasacharya
Department of Mathematics, National Institute of Technology, Warangal, Telangana, 506004,
India
Mekonnen
Shiferaw
Arba Minch University, Department of Mathematics, Arba Minch, Ethiopia
The steady flow of an incompressible and electrically conducting micropolar fluid flow through a parallel porous plates is studied. A constant pressure gradient is assumed along the direction of the fluid and the flow is subjected to a uniform magnetic field perpendicular to the flow direction. The governing equations are reduced to nonlinear coupled ordinary differential equations using similarity transformations. The resulting equations are then solved numerically by quasilinearization technique. The profiles of velocity and microrotation components are presented for different micropolar fluid parameters and magnetic parameter. The skin friction at the plates has also been calculated.
Effect of Polymer Additives on the Dynamics of a Fluid for Once Through System
374-393
10.1615/InterJFluidMechRes.v35.i4.70
Chirravuri
Subbarao
Department of Chemical Engineering, MVGR College of Engineering, Chintalavalasa,
Vizianagaram-535005, Andhra Pradesh
P.
King
Environmental Pollution Control Engineering Laboratory, Department of Chemical Engineering, AU College of Engineering, Andhra University, Visakhapatnam, Andhra Pradesh
V. S. R. K.
Prasad
Anil Neerukonda Institute of Technology & Sciences (ANITS)
A mathematical equation for efflux time for slow draining of a Newtonian liquid from a large cylindrical tank through an exit pipe located at the bottom of tank when the flow in the pipe line is turbulent is developed based on macroscopic balances. The equation is fine tuned with the experimental data and an empirical equation for friction factor is developed. The efflux time equation so developed will be of use in arriving at the minimum time required for draining the tank. When the flow is partly laminar and partly turbulent, gravity driven and once through (as is the case in the above), the effect of addition of water soluble Polyacrylamide polymer on drag reduction is expressed in terms of % reduction in efflux time. Based on the efflux time, an empirical equation for friction factor is developed. The concentration of polymer which gives maximum drag reduction is also established.