Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
33
5
2006
Experiments for the Discharge Capacity of the Siphon Spillway Having the Creager-Ofitserov Profile
395-406
Larbi
Houichi
Department of Hydraulics, University of Batna, Algeria, Research Laboratory in Applied Hydraulics (LA.R.HY.A)
Ghassan
Ibrahim
Department of Water Engineering, University of Al-Baath, Homs, Syria
Bachir
Achour
Research Laboratory in Subterranean & Surface Hydraulics, Department of Hydraulics, University of Biskra, Biskra, Algeria
One type of spillways for dams in physical models is deliberately tested. It is a siphon spillway having the Creager-Ofitserov profile, studied in four alternative models with various configurations based on variation of the cross section. The study highlighted a clear distinction for not and almost complete prime areas for low head and complete prime areas for the remainder of the values of the head applied to the level upstream. It is to be announced that the coefficients of discharge of the siphons models increase very quickly while going from the first to the fourth model, for this purpose the optimal cross section corresponding to the maximum coefficient of discharge was fixed. The variation at the same time of the coefficient of discharge, the ratio of the head on vertical dimension at the crown of the siphon and the Froude number were formulated. At the particular case of priming, this formulation deduces a new relationship making possible to envisage the Froude number for a known coefficient of discharge.
An Experimental Investigation of High Blockage Vortex Shedding for Perturbed Flow
407-420
T. S.
Khan
Faculty of Mechanical Engineering, Ghulam Ishaq Khan Institute of Engineering Sciences & Technology, Topi, District Swabi, N.W.F.P. Pakistan
M. P.
Mughal
Faculty of Mechanical Engineering, Ghulam Ishaq Khan Institute of Engineering Sciences & Technology, Topi, District Swabi, N.W.F.P. Pakistan
The combined effects of a free stream velocity pulsation of controlled frequencies and a high blockage ratio on the vortex shedding from bluff cylindrical bodies have been studied. This study includes signal quality behind the bluffs, power spectral density, signal to noise ratio, amplitude variation of velocity profile, and Strouhal-Reynolds number correlation. The Reynolds number based on the bluff's characteristic dimension, d is kept in the range 1000−6000. Two circular bluffs of dimensions 20 and 32.1 mm and a triangular cylinder of width 15 mm were used and positioned vertically in the test section. The effect of moderate frequency amplitude, up to 15 Hz, of free stream velocity perturbation on Strouhal number is almost insignificant for low blockage ratios but for higher blockage ratios the Strouhal number dropped by up to 10 % around Re ≈ 3000. The velocity amplitude decreased with increasing downstream distance from the bluff bodies. The blockage ratio did not have a significant effect on the SNR as the peak value remained in the range 40−50 dB. However, the Strouhal number increased with increasing tunnel blockage ratio.
Effect of Magnetic Field and Rotation on Thermal Convection in Walters B' Viscoelastic Fluid
421-429
Pardeep
Kumar
Department of Mathematics, International Centre for Distance Education and Open Learning (ICDEOL), Himachal Pradesh University, Shimla-171005, India
Roshan
Lal
Department of Mathematics, ICDEOL, Himachal Pradesh University, Shimla-171005, India
The thermal convection in Walters B’ viscoelastic fluid is considered in the presence of a uniform vertical magnetic field and uniform rotation. For the case of stationary convection, Walters B’ viscoelastic fluid behaves like a Newtonian fluid. It is found that rotation has a stabilizing effect, whereas the magnetic field has both stabilizing and destabilizing effects. Graphs have been plotted by giving numerical values to the parameters, depicting the stability characteristics. The rotation, magnetic field, and viscoelasticity are found to introduce oscillatory modes in the system that were nonexistent in their absence.
Stability Properties of a Boundary Layer Flow Past a Continuously Moving Wall in a Streaming Flow
430-444
Eunice W.
Mureithi
Department of Mathematics and Applied Mathematics, University of Pretoria, Pretoria 0002, South Africa
Boundary layer flow over a wall moving with velocity Uw(x) = Ucxn and in a moving stream with velocity Ue(x) = U∞xn is considered. The wall is also subjected to fluid suction/injection. Self-similar boundary layer equations are derived. The existence of dual solutions in some parameter regions has been shown both analytically and numerically. There are critical values of the parameter λ = U∞/(Uc + U∞) beyond which no physically realistic solutions are realized. The occurrence of points of inflection in the velocity profiles is observed with increase in both fluid injection and λ. Linearized stability analysis of the boundary layer flow is carried out. The governing Orr-Sommerfeld equation is solved using the Chebyshev spectral collocation method. Results show the destabilizing effect of both the fluid injection and λ to both the viscous mode resulting from solving the Orr-Somerfeld equation and the inviscid Rayleigh waves. The Rayleigh inviscid modes are unstable in only some define wave-number regimes, restabilization occurring at some higher wave-numbers. The flow is most unstable when the wall moves reversely to the free-stream.
Effect of Particle Size Distribution on Rheological Properties of Fly Ash Slurries at High Concentrations
445-457
Abhai Kumar
Verma
Kamla Nehru Institute of Technology; Civil Engineering Department, Bundelkhand Institute of Engineering and Technology, Jhansi, (UP), India
Sidh
Singh
Indian Institute of Technology Delhi
V.
Seshadri
Department of Applied Mechanics, IIT Delhi Hauz Khas, New Delhi, India
The rheological behavior of fly ash slurry at any concentration has a marked dependence on particle size distribution. Five groups of fly ash samples having different particle size distribution are prepared by wet sieving to simulate the fly ash collected from different fields of electrostatic precipitator hoppers. Six suspensions of different solid concentrations (by weight) are prepared from each sample to study the effect of solid concentration on the rheological parameters. The study shows that the fly ash slurries above a solid concentration of 40 % by weight are non-Newtonian and that the experimental data fit a simple Bingham plastic model. It further shows that the rheological parameters increase monoton-ically with the solid concentration and have higher values for finer particulate suspensions.
Sound Generation by a Limited Region of Disturbed Flow in a Rigid Channel of Circular Cross-Section. Particular Cases
458-472
A. O.
Borisyuk
Institute of Hydromechanics of the National Academy of Sciences of Ukraine, Zhelyabov Str., 8/4, 03680, Kyiv-180, MSP, Ukraine
Particular cases of the theory of noise generation by a limited region of disturbed flow in an infinite straight rigid channel of circular cross-section, which has been developed earlier, are considered. In these cases the situations are studied when the contributions made either by volume quadrupoles or surface dipoles dominate in generated acoustic field. Those flows and shapes of the channel local geometrical inhomogeneities are of interest, that results in large or small eddies distributed uniformly in the disturbed flow region behind the inhomogeneity. The corresponding simplified expressions for the acoustic power generated are obtained in the considered cases, and their estimates are carried out for the characteristic scales in the disturbed flow region.
A Cavitational Regime of a Sonocapillary Effect
473-487
E. Yu.
Rozina
Odessa State Academy of Cold, Ukraine
The parameters of a sonocapillary liquid flow are investigated. The processes under the capillary cut end were registered by means of a high-speed photography. It is shown that the cavitation under the capillary cut end behaves as a collective process. So, a translation (drift) of the whole cluster of cavities to the capillary channel, but not a closure dynamics of each individual cavity, is the most probable cause of sonocapillary liquid flow. It is shown that the localized cavitation concentrates the acoustic energy, and the directed translation of the cavitations provides this energy transforming into that of the capillary liquid flow.