Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
33
4
2006
Pressure Drop in Laminar and Turbulent Flows in Circular Pipe with Baffles − An Experimental and Analytical Study
303-319
Mushtak
Al-Atabi
Mechanical Engineering Department, University of Sheffield, Sheffield S1 3JD, UK
S. B.
Chin
Mechanical Engineering Department, University of Sheffield, Sheffield S1 3JD, UK
Xiao Yu
Luo
Department of Mathematics, University of Glasgow, Glasgow, UK
Sulaiman
Al-Zuhair
School of Chemical Engineering, Faculty of Engineering, The University of Nottingham Malaysia Campus, Semenyih, Malaysia
Flow in a circular pipe fitted with segmental baffles may be treated as a shell-without-tube system. Its pressure drop has been calculated by adapting the Kern correlation [1] for pressure drop in the shell side of shell-and-tube heat exchangers. The Kern correlation is essentially based on the Hagen − Poiseuille equation for laminar flow, but flow visualization results presented here show that enhanced mixing and turbulence-like flow may be present at Reynolds numbers (based on the pipe diameter) as low as 50. A mathematical model, accounting for the effects of geometry of the baffle configurations, has been developed to predict the pressure drop in circular pipe fitted with segmental baffles. The model was solved algebraically for flow in pipe with three baffle arrangements and the results were validated by experimental data. The pressure drops thus calculated showed better agreement with experimental results than those predicted by the modified Kern model for Reynolds number in the range of 50 − 600.
Three-Dimensional Free Convection Flow and Heat Transfer Past a Vertical Channel
320-333
Mrinmoy
Guria
Department of Applied Mathematics with Oceanology and Computer Programming, Vidyasagar University, Midnapore - 721102, West Bengal, India
Rabindra N.
Jana
Department of Applied Mathematics, Vidyasagar University, Midnapore-721 102, West Bengal, India
An analysis is made on the three dimensional flow of viscous incompressible fluid past a vertical channel in the presence of a uniform injection on the right plate and the left plate to a periodic suction velocity distribution. The velocity and temperature field have been derived using perturbation technique. It is found that the primary velocity increases near the left plate and decreases near the right plate with increase in Reynolds number while it increases with increase in Grashof number. It is seen that the shear stress due to main flow increases with increase in either Grashof number or Reynolds number but decreases with increase in Prandtl number. Also the magnitude of the shear stress due to cross flow increases with increase in Reynolds number. It is seen that the temperature profile decreases with increase in either Prandtl number or Reynolds number. The rate of heat transfer in terms of Nusselt number has also been studied.
Effect of Successive Suction on the Near-Wall Turbulence Structure
334-344
Olanrewaju
Oyewola
Discipline of Mechanical Engineering, The University of Newcastle NSW, 2308, Australia
The effects of successive suction on the near-wall turbulence structure have been examined in a wall bounded boundary layer through the measurements of turbulent quantities, production and diffusion terms of the turbulent kinetic energy equation. The result indicates that double suction shows a better alteration of the near-wall turbulent structures than a single suction. Turbulent kinetic energy production is significantly reduced and the effect is enhanced by double suction downstream of the second strip. There is a gain of turbulent kinetic energy by diffusion in the near-wall region for both cases of suction relative to those of zero-suction.
Double Diffusive Convection of Water in a Rectangular Partitioned Enclosure with Temperature Dependent Species Diffusivity
345-361
Sivanandam
Sivasankaran
Department of Mathematics, King Abdulaziz University, Jeddah 21589, Kingdom of Saudi Arabia
Prem Kumar
Kandaswamy
UGC-DRS Center for Fluid Dynamics, Department of Mathematics, Bharathiar University, Coimbatore-641046, Tamil Nadu, India; Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
The double diffusive convection of cold water around its density maximum in a rectangular partitioned enclosure with isothermal side walls and insulated top and bottom is studied numerically. A thin partition is attached to the hot wall. The species diffusivity of the fluid is assumed to vary linearly with temperature. The two-dimensional flow equations expressed by stream function-vorticity formulation along with the energy and concentration equations are solved by finite difference scheme. The effects of position and height of the partition, and variable species diffusivity are analyzed for various Grashof numbers. The heat and mass transfer characteristics are analyzed using the streamlines, isotherms and isomasslines. It has been found that adding partition on the hot wall reduces the heat transfer. Also found that the density inversion of the water has a great influence on the natural convection. We concluded that placing partition at the middle of the hot wall has marked effect on flow pattern and heat transfer in the enclosure.
Transient Boundary Layer in Stagnation-Point Flow of a Micropolar Fluid Over a Stretching Sheet
362-378
Mahesh
Kumari
Department of Mathematics, Indian Institute of Science, Bangalore 560 012, India
D.
Cimpean
Department of Mathematics, Technical University of Cluj, Cluj, Romania
Ioan
Pop
Department of Applied Mathematics, Babes-Bolyai University, 400084 Cluj-Napoca, Romania
An analysis of the transient two-dimensional stagnation-point flow of a micropolar fluid past a stretching sheet in its own plane has been made in the present paper. The unsteadiness in the flow field has been introduced by the sudden change in the surface velocity. The stretching velocity is assumed to vary linearly with the distance from the stagnation-point. Two equal and opposite forces are applied along the x-axis so that the wall is stretched, keeping the origin fixed in a micropolar fluid. The transformed boundary layer equations are solved numerically for some values of the involved parameters using a very efficient numerical scheme known as Keller-box method. The computations have been carried out from the initial steady-state flow to the final steady-state flow. The velocity and micropolar profiles along with the skin friction coefficient at the sheet are analyzed and discussed in detail. When the surface velocity is suddenly raised or is suddenly reduced, it is found that the skin friction vanishes in a small time interval after the start of the impulsive motion, but it does not imply flow separation.
Experimental Study of the Wall Pressure Fluctuations in Elastic Pipe Behind a Local Axisymmetric Narrowing
379-389
A. O.
Borisyuk
Institute of Hydromechanics of the National Academy of Sciences of Ukraine, Zhelyabov Str., 8/4, 03680, Kyiv-180, MSP, Ukraine
Wall pressure fluctuations pt in an elastic pipe behind a local axisymmetric narrowing are studied. Sharp increase in the pressure pt in a finite region immediately downstream the narrowing and the presence of a pronounced pressure maximum upstream the point of jet re-attachment were found. The study of the wall pressure power spectrum, P(f), has revealed the low-frequency maximums in it. The maximums were found to be determined by the appropriate large-scale eddy structures in the regions of separated and reattached flow, and their frequencies were close to the characteristic frequencies of the eddies formation. A comparative analysis of the data for rigid-walled and elastic pipes shows that the wall elasticity causes the changes in the flow structure and the corresponding redistribution of the flow energy among the vortices. This results in the increase of the wall pressure amplitude and the level of the wall pressure power spectrum, P(f), at low frequencies, as well as appearance of new frequency components in this domain.
Features of a Wavetrain Emitted at High-Voltage Electric Discharge in Water
390-393
A. I.
Vovchenko
Institute of Pulse Processes and Technologies of National Academy of Sciences of Ukraine, Mykolayiv, Ukraine
V. V.
Shamko
Institute of Pulse Processes and Technologies of National Academy of Sciences of Ukraine, Mykolayiv, Ukraine
A. M.
Shyshov
Institute of Pulse Processes and Technologies of National Academy of Sciences of Ukraine, Mykolayiv, Ukraine
A possibility to redistribute the intensities of the first and second compression waves emitted by underwater high-voltage electrical discharge by variation of the input mode of electric energy in the discharge filament is proved experimentally. It is shown that the high-voltage electrical discharge as an acoustic emitter of the explosive type should be placed between the explosions of chemical condensed matters and gaseous mixtures.