Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
37
5
2010
Drag Reduction by Polymer Additions in Once Through Systems
391-405
Ch. V.
Subbarao
Department of Chemical Engineering, MVGR College of Engineering
Late G. Mallikarjuna
Rao
University of Petroleum and Energy Studies Dehradun
P.
King
Environmental Pollution Control Engineering Laboratory, Department of Chemical Engineering, AU College of Engineering, Andhra University, Visakhapatnam, Andhra Pradesh
C. Bhaskara
Sarma
Gayatri Vidya Parishad College of Engineering Mudhurawada
V. S. R. K.
Prasad
Anil Neerukonda Institute of Technology & Sciences (ANITS)
A mathematical equation was developed, based on macroscopic balances, for efflux time during gravity draining of a Newtonian liquid from a large cylindrical tank through two-exit pipes located at the bottom of the tank, the flow in each of the pipes being turbulent. The equation was verified with the experimental data. Efflux time comparisons were also made with that of single exit pipe system both in the absence and presence of polymer additions to arrive at the minimum time required for draining contents of the storage vessel. Further, the effect of polymer additions on efflux time for two-exit pipe system was also carried out. The extent of increase in Froude number on the addition of water-soluble polymer was also established.
Hydromagnetic Mixed Convection in a Two-Sided Lid-Driven Porous Enclosure
406-423
M.
Muthtamilselvan
Department of Applied Mathematics, Bharathiar University, Coimbatore-641 402, India
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
Jinho
Lee
School of Mechanical Engineering, Yonsei University, Seoul 120-749, Korea
The effect of magnetic field on mixed convection in a two-sided lid-driven cavity filled with a fluid saturated porous medium is studied numerically. The left and right vertical walls of the cavity are insulated while the top and bottom horizontal walls are kept at constant but different temperatures. The top and bottom horizontal walls are moving on its own plane at a constant speed while vertical walls are fixed. Two cases were considered depending on the direction of moving walls. A uniform magnetic field is applied in the vertical direction normal to the moving wall. The governing equations are solved using finite-volume approach along with the SIMPLE algorithm. Numerical solutions are obtained for a wide range of parameters. It is found that Hartmann number, Richardson number, Darcy number and direction of the moving walls have strong influence on the fluid flow and heat transfer in the enclosure.
Stokes Flow of Micropolar Fluid past a Porous Sphere with Non-Zero Boundary Condition for Microrotations
424-434
Bali Ram
Gupta
Department of Mathematics, JaypeeUniversity of Engineering and Tech., Guna 473226, M. P., India.
Satya
Deo
Department of Mathematics, University of Allahabad, Allahabad-211002, India
The Stokes flow problem is considered for micropolar fluid past a porous sphere assuming the flow at distant points is uniform and parallel to the axis of symmetry. A nonhomogeneous boundary condition for the microrotation vector i. e., the microrotation on the boundary of the sphere is assumed to be proportional to the rotation rate of the velocity field on the boundary, is used. The stream functions are determined by matching the solutions of Stokes equation for flow outside the sphere with that of the Brinkman equation for the flow inside the porous sphere. The drag force experienced by a porous sphere is evaluated and its variation is studied with respect to the material parameters. Some well-known results are then deduced from the present analysis.
Transient Magnetohydrodynamic Couette Flow with Ramped Velocity
435-446
Ashok
Singh
Banaras HIndu University, Varanasi (india)
Anand
Kumar
Department of Mathematics, Faculty of Science, Bararas Hindu University, Varanasi
The transient flow of a viscous incompressible and electrically conducting fluid between two parallel plates is analyzed analytically when lower plate moves with a ramped velocity. The velocity of magnetic field, applied perpendicular to the plates is taken to be different from the velocity of lower plate. The induced magnetic field is taken to be negligible. The analytical solution is obtained by using the Laplace transform technique. The numerical results obtained for the dimensionless velocity and skin-friction coefficient are presented by graphs and tables for various values of magnetic parameter, velocity of magnetic field and time. It is found that the effect of velocity of magnetic field is to increase the velocity of fluid from upper plate to lower plate. The effect of magnetic parameter on the velocity of fluid and skin-friction at the lower plate depends upon the velocity of magnetic field.
Numerical Simulation of MHD Turbulent Flow in a Rectangular Channel with Three-Surface-Coated Multi Layers
447-457
Mitsuhiro
Aoyagi
Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Japan
Hidetoshi
Hashizume
Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Japan
Kazuhisa
Yuki
Department of Mechanical Engineering, Tokyo University of Science, Yamaguchi, 1-1-1 Digakudo-ri, Sanyo-onoda, Yamaguchi, 756-0884 Japan; and Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aramaki-Aoba 01, Aoba-ku, Sendai, 980-8579, Japan
Satoshi
Ito
Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University
Takeo
Muroga
National Institute for Fusion Science 322-6 Oroshi, Toki,Gifu, Japan, 509-5292
A rectangular channel with three-surface-coated multi layers has been proposed to reduce the MHD pressure drop in the liquid metal blanket system. In this study, the turbulent flow and pressure drop characteristics are investigated with changing the orientation of the magnetic field by numerical simulation, where a k−ε model containing the effects of the magnetic field is employed. The simulation is conducted under the conditions; the Reynolds number of 4494 and the Hartmann number of 20.9 or 52.2. The inclination of the magnetic field (θ) is changed from 0° to 90°. At an inclination of θ = 45°, turbulence viscosity becomes the highest due to the velocity distributions with more turbulence kinetic energy production. The pressure drop increases when θ is larger than 30° by the electromagnetic force, especially in the case of higher Hartmann number.
Effect of Particle Separation and Sand Erosion in a Hydraulic Turbine
459-469
Bhola
Thapa
Department of Mechanical Engineering, Kathmandu University, Kathmandu, Nepal
Sand erosion is one of the major operational problems of hydropower plants in the Himalayan Rivers. Size is the main factor responsible for particle transport and erosion. For the particles flowing in the curved path or swirl flow, centrifugal force is caused by tangential component of absolute velocity while drag force is caused by absolute velocity. The equilibrium of these two forces gives critical diameter of the particle which will be rotating in the orbit. Such critical diameter is a function of the drag coefficient, specific gravity of the particle, radius at which the particle is moving and ratio of particle velocity in peripheral direction to the absolute velocity of water. Particles larger than the critical diameter move away from the center of the flow path and thus hit the wall whereas but smaller particles flow along with the water. The swirl flow test rig was designed and developed at Norwegian University of Science and Technology to study the effect of particle separation. This test rig simulates the flow in between guide vane outlet and runner inlet of Francis turbine. The flow of particle in the swirl flow was observed by naked eye and high speed video camera. The value of coefficient of drag from this experiment was found to be in between 0.1 -0.2 and compared well with literature data against particle Reynolds number. In the full opening position, the guide vanes can be fixed from 10 to 40° which creates strong swirl. For the turbine of radius 1m at inlet, sand particles of diameter larger than 2 mm will stay rotating in swirl flow damaging guide vanes positioned around 10°. At higher Reynolds number and drag coefficient 0.1, even small particles of 1 mm size will stay rotating and hitting the guide vane wall. The experimental setup helps to develop operational guidelines for Francis turbine operating with large sand particles. If the particle size in the water is larger than the critical particle size, the turbine should not be operated at low guide vane opening. The experimental observation reveals that smaller turbines are more prone to sand erosion.
Research Strategy for Active Flow Control Based on Distributed Thermal Fields
470-489
Nina F.
Yurchenko
Institute of Hydromechanics of National Academy of Sciences of Ukraine, 8/4, Zhelyabov St.,
Kyiv, 03057, Ukraine
The concept is offered for flow control which is based on purposeful modification of fluid motion space scales near a surface. It is proven using the developed approach of imposed spanwise-regular thermal fields (temperature boundary condition) causing a boundary-layer response in a form of srtreamwise vortices of a given scale. Such flow structure modification is shown to result in the improvement of aerodynamic performance of a test model under conditions of correct correlation between basic flow and control parameters.