Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
38
5
2011
Effect of Step Geometry on the Performance of the Airlift Pump
387-408
Pedram
Hanafizadeh
Center of Excellence in Design and Optimization of Energy Systems, School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
A.
Karimi
Multiphase Flow Research Group, Centre of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Mohammad Hassan
Saidi
Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif
University of Technology, P.O. Box 11155-9567, Tehran, Iran
Airlift pumps are devices which are widely used in industrial applications. Parameters such as diameter of the pipe, tapering angle of the upriser pipe, submergence ratio, the gas flow rate, bubble diameter, and inlet gas pressure affect the performance of this type of pumps. In this research, the performances of airlift pumps with a vertical upriser length of 914 mm and initial diameters of 6 and 8 mm and various heights for steps, range 0.2 to 0.9 m, in submergence ratio of 0.6 are investigated numerically. The results show the improvement in the performance of step airlift pump (SALP) in comparison with ordinary type (OALP). Considering the effect of height of steps and secondary pipe diameter, can be shown that in constant gas flow rate there exist specific height and secondary diameter for step which can optimize the performance of the pump. The numerical results were compared with the existing experimental data, showing a reasonable agreement. The results have indicated that step airlift pump has higher efficiency than the pump with constant pipe diameter.
A Numerical Study of Circular Journal Bearings Running under Turbulent Regime
409-423
Alireza Arab
Solghar
Department of Mechanical Engineering, School of Engineering, Vali-e-Asr University Rafsanjan, Iran
S. A. Gandjalikhan
Nassab
Mechanical Engineering Department, School of Engineering, Shahid Bahonar University of
Kerman, Kerman, Iran
The classical theory of hydrodynamic lubrication assumes that the flow regime is laminar and the inertia forces in the fluid film are negligible. For large bearings using low kinematic viscosity lubricant or for high speed, the inertia forces could be important and non laminar flow occurs. In the present thermo-hydrodynamic analysis of axial grooved journal bearings with finite length, the Navier-Stokes equations, turbulent kinetic energy and its dissipation rate equations are solved along with the energy equation in the lubricant flow and the heat conduction equation of bush and shaft to obtain the steady state characteristics. The turbulent flow inside the Journal bearing is modelled using the AKN low-Re k−ε turbulence model. The problem is formulated mathematically and solved numerically using the computational fluid dynamics (CFD) approach with appropriate boundary conditions. In order to investigate the influence of main parameters on the steady state performance characteristics of journal bearings for a variety of simulated operating conditions, different values of eccentricity, radial clearance and shaft rotation speed are considered. The numerical results are compared with existing measurements and also with other theoretical solutions, good agreements are attained.
Explicit Solutions for Steady Three-Dimensional Problem of Condensation Film on Inclined Rotating Disk
424-436
Hamed
Shahmohamadi
University of California, Los Angeles
Mohammad Mehdi
Rashidi
Tongji University
The similarity transform for the steady three-dimensional problem of condensation film on an inclined rotating disk gives a system of nonlinear ordinary differential equations which is analytically solved by applying a newly developed method namely the variational iteration method (VIM). The velocity and temperature profiles are shown and the influence of Prandtl number on the heat transfer and Nusselt number is discussed in detail. The validity of our solutions is verified by the numerical results.
A Study on Bed Expansion of Group A/B Particles in Presence of an Acoustic Filed
437-443
Akash M.
Langde
Department of Mechanical Engineering, Anjuman College of Engineering, Nagpur, Maharashtra, India
Md.
Shakebuddin
Department of Mechanical Engineering, Anjuman College of Engineering and Technology, Nagpur (MH), India
R. L.
Sonolikar
Laxminarayan Institute of Technology, Nagpur, Maharashtra, India
D. J.
Tidke
G.H. Raisoni College of Engineering, Nagpur, Maharashtra, India
According to research performed for nearly fifty years, the fluidization of fine powders is complex. The difficulty of putting these powders in suspension in the fluidizing gas is related to the cohesive structure and, in particular, to the physical forces between the primary particles. The basic aim of this research work was to improve the quality of fluidization of Marble powder (dp = 90 μ;m) by applying external source in terms of acoustic field. Also, effect of acoustic field on minimum fluidization velocity (Umf ) has been found out at resonant frequency. The value of Umf at 145 dB and 120 Hz is found to be 0.72 cm/s which was very less compared to Umf 0 at without sound intensity i.e., 1.6 cm/s. It was also noted that bed expansion (H) is marginally improved compared to without application acoustic field.
Consequences of Indeterminate Form of Volume of Floating Balloons in Water
444-449
Ajay
Sharma
Fundamental Physics Society
It is observed in critical analysis of completely submerged floating balloons in water, that under some feasible conditions, the volume of fluid filled in balloon takes indeterminate form i. e., 0/0 in equations based upon Archimedes principle. These equations became feasible 1935 years after enunciation of the principle in 1685, when Newton defined g in The Principia. If in this case definition of the principle is generalized i. e., upthrust is proportional to the weight of fluid displaced, then results are consistent. Thus, co-efficient of proportionality comes in picture, which accounts for shape of body, viscosity of medium, magnitude of medium etc. Stokes law takes in account the shape of body and viscosity of medium, and is experimentally confirmed, hence generalized form of the principle is justified, however in narrow range. Furthermore some specific experiments have been suggested to confirm effect of coefficient of proportionality. Such specific studies do not mean any comment or conclusion of the established status of the principle.
The Necessary Condition for the Onset of Stationary Convection in Couple-Stress Fluid
450-457
Ajaib S.
Banyal
Department of Mathematics, Govt. College Nadaun, Dist. Hamirpur, (HP) India 177033
The thermal instability of a couple-stress fluid heated from below is investigated. Following the linearized stability theory and normal mode analysis, the paper mathematically establishes that the onset of instability at marginal state, cannot manifest itself as stationary convection, if the thermal Rayleigh number R and the couple-stress parameter F, satisfy the inequality
R≤ (27π4)/4{1+(3π2/2)F},
the result which also clearly mathematically established the stabilizing character of the couple-stress.
Mathematical Modeling of a Secondary Clarifier with Cone-Shaped Bottom
458-478
N.
Stepova
Institute of Hydromechanics of National Academy of Sciences of Ukraine Zhelyabov St., 8/4, Kyiv-180 MSP, 03680, Ukraine
Yu. I.
Kalugin
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
A 1D mathematical model for a secondary clarifier with cone-shaped bottom and its numerical solution via the Cauchy−Euler method are presented in the paper. The model includes, among other parameters, the relationship between the velocity of hydraulic flux and clarifier cross-sectional area. A computer code to calculate suspended solids profiles in the clarifier in different time moments is developed along with a computer code for the visualization of obtained data. Some examples to illustrate the model possibilities are presented. The state of the art of secondary clarifier modeling is given in the paper. Different expressions to estimate the activated sludge settling velocity are studied, for settling velocity is an integral part of every clarifier model.