Journal Of Applied Fluid Mechanics
Volume:6 Issue: 1, Jan-Feb 2013

The generation of wave due to moving hydrofoil in steady streams close to a free surface is presented. The potential-based boundary element method is employed to the NACA4412 hydrofoil with linearized dynamic and kinematic boundary conditions on the free surface. The perturbation velocity potential is calculated using the Green formulation and Kutta condition. The numerical results of waves generated by the hydrofoil are presented and discussed at various Froude numbers and immersion depths.

This paper describes the use of Taylor dispersion analysis to study the dispersion of chiral fluid flow in a channel in the presence of the convective current bounded by rigid permeable walls. Analytical solution for velocity in the presence of a transverse magnetic field is obtained and it is computed for different values of electromagnetic parameterWem. The results reveal that the velocity increases with an increase in the electromagnetic parameter, Wem. Concentration distribution is also determined analytically in the presence of advection of concentration of chiral fluid. It is shown that the molecules of chiral fluid dispersed relative to the plane moving with the mean speed of flow with an effective dispersion coefficient, * D, called Taylor dispersion coefficient. This is numerically computed for different values of electromagnetic parameter, Wem, Paclet number Pe and Reynolds number, Re. The results shows that dispersion coefficient, * D decreases monotonically with Reynolds number, Re, Paclet number Pe, but increase with an increase in electromagnetic parameter, Wem.

In the present paper, the fully developed laminar free convective flow of a viscous incompressible and electrically conducting fluid between two concentric vertical cylinders is considered in the presence of a radial magnetic field. The induced magnetic field produced by the motion of an electrically conducting fluid is taken into account. The expressions for the temperature, velocity,induced magnetic field, induced current density, skin-friction and Nusselt number are obtained in a closed form under more general boundary conditions for the induced magnetic field. The influence of the Hartmann number and buoyancy force distribution parameter on the fluid velocity, induced magnetic field and induced current density have been analyzed by using the graphs while the values of the skin-friction, Nusselt number, induced current flux and mass flux are given in the tabular form. It is observed that the fluid velocity and induced magnetic field are rapidly decreasing with increase in the value of Hartmann number in the case when one of the cylinders is conducting compared with the case when both cylinders are non-conducting. The effect of the induced magnetic field is to increase the velocity profiles in comparison to the case of neglecting the induced magnetic field. The buoyancy force distribution parameter has tendency to increase the fluid velocity, induced magnetic field, temperature field and induced current flux.

The effects of radiation and rotation on unsteady hydromagnetic free convection flow of a viscous incompressible electrically conducting fluid past an impulsively moving infinite vertical plate with ramped temperature in a porous medium are investigated. Exact solution of momentum and energy equations, under Boussinesq approximation, is obtained in closed form by Laplace transform technique. To compare the results obtained in this case with that of isothermal plate, exact solution of the governing equations is also obtained for isothermal plate. The expressions for the primary and secondary skin frictions and Nusselt number are also derived. It is noticed that, for both ramped temperature and isothermal plates, rotation retards fluid flow in the primary flow direction whereas it accelerates fluid flow in the secondary flow direction in the boundary layer region while radiation exerts accelerating influence on the fluid flow in both the primary and secondary flow directions. For ramped temperature plate radiation reduces primary skin friction whereas it tends to increase secondary skin friction. For isothermal plate radiation has tendency to reduce secondary skin friction. Radiation tends to increase fluid temperature for both ramped temperature and isothermal plates. With the increase in time the rate of heat transfer at the plate is reduced for isothermal plate while it is increased for ramped temperature plate.

The effects of Hartmann number, porous parameter and Darcy velocity on the steady flow of a viscous incompressible slightly conducting fluid through a uniform channel bounded by porous media of finite thickness under a uniform ransverse magnetic field are considered. It is assumed that the thickness of the porous media is much smaller than the width of the flow channel as in the case of blood flow in arteries and accordingly the BJR slip boundary condition has been employed. The effects of all the above parameters on the axial velocity of the flow and the shear stress have been investigated. Finally, these results are compared with a earlier problem of MHD flow through a uniform channel covered by porous media of infinite thickness where the BJ slip boundary condition has been employed

This study focuses on fires in road tunnels in order to increase the level of security for users. This paper proposed numerical investigations carried out on a small scale tunnel model to study the fire-induced smoke control by longitudinal and longitudinal-natural ventilation systems. We studied the effect of two ventilation systems on the temperature distribution and stratification of the pollutant to estimate the effectiveness of ventilation systems. The flow is characterized by the temperature fields, temperature profiles and the Froude number. The numerical tool used is FDS (version 4.0). This numerical study requires validation with experiment and numerical results and comparison with the model developed by Kunsch J.P. to evaluate the critical velocity. However, good agreement with experimental results, it confirms the possibility of using this code in the problem.

High engine oil temperatures have detrimental effect on overall engine performance and durability. High oil temperature is a direct indication of high engine temperature and hence, the inefficient cooling system of the engine. In this paper we show how the systematic investigation of cooling system thought experiments and CFD modeling can reduce the engine oil temperature within the desirable limit. A CFD model was developed for the entire cooling system and results were validated with the experimental measurements. The CFD model and experimental measurement techniques have been described in detail. Separate experimental measurements were conducted for flow and thermal measurements and the corresponding CFD model was validated against these measurements. Various design concepts were investigated and its effects on engine heat transfer coefficients and temperatures, change in system resistances, flow rates and other parameters have been presented. A simple experimental setup was developed for optimization of the centrifugal fan. The optimized fan was then used in the CFD model. It was observed that the reduction in engine oil temperature could be achieved by systematic design changes. However, it comes at the expense of increase in system resistance.

In this research, pool boiling heat transfer coefficient values were experimentally measured up to heat flux 115kW.m-2. Experiments were carried out for pool boiling of pure liquids, including of Formic acid, Propanol, 2-butanol on a horizontal smoothed cylinder, at atmospheric pressure. Applicability of the existing well-known and most common used correlations is comparatively discussed, with the present experimental data. The major predictions (over and/or under) were observed in some parameter range by the existing correlations. In this investigation the correlations of Stephan Abdelsalam, Boyko-Kruzhilin and Mostinski, have been compared with experimental data.

We employ numerical simulations to investigate the breakup of droplets in micro- and nanoscale T junctions, which are used to produce small droplets from a large droplet. For this purpose a Volume f Fluid (VOF) based method is used and for verifying the reliability of the numerical outcomes, the results are compared with the available experimental and analytical results. Our results reveal that breakup time and breakup length of the droplets play important roles in handling these systems optimally. Our results also indicate that for nanoscale Tjunctions by increasing the capillary number the performance increases while for the micro-scale systems there is a specific capillary number for which the system is in its optimum condition.

The thermosolutal convection in Walters’ (Model B'') elastico-viscous rotating fluid permeated with suspended particles (fine dust) and variable gravity field in porous medium in hydromagnetics is considered. By applying normal mode analysis method, the dispersion relation has been derived and solved numerically. It is observed that the rotation, magnetic field, gravity field, suspended particles and viscoelasticity introduce oscillatory modes. For stationary convection, Walters’ (Model B'') elastico-viscous fluid behave like an ordinary Newtonian fluid and it is observed that rotation and stable solute gradient has stabilizing effects and suspended particles are found to have destabilizing effect on the system, whereas the medium permeability has stabilizing or destabilizing effect on the system under certain conditions. The magnetic field has destabilizing effect in the absence of rotation, whereas in the presence of rotation, magnetic field has stabilizing or destabilizing effect under certain conditions. The effect of rotation, suspended particles, magnetic field, stable solute gradient and medium permeability has also been shown graphically. AMS subject classifications are 76A10, 76E07, 76E25 and 76S05.

This paper examined the hydro magnetic boundary layer flow with heat and mass transfer over a vertical plate in the presence of magnetic field with Soret and Dufour effects, chemical reaction and a convective heat exchange at the surface with the surrounding has been studied. The similarity solution is used to transform the system of partial differential equations and an efficient numerical technique is implemented to solve the reduced system by using the Runge-Kutta fourth order method with shooting technique. A comparison study with the previous results shows a very good agreement. The results are presented graphically and the conclusion is drawn that the flow field and other quantities of physical interest are significantly influenced by these parameters.

A mathematical model is presented for a two-dimensional, steady, incompressible electrically conducting, laminar free convection boundary layer flow of a continuously moving vertical porous plate in a chemically reactive and porous medium in the presence of a transverse magnetic field. The basic equations governing the flow are in the form of partial differential equations and have been reduced to a set of non-linear ordinary differential equations by applying suitable similarity transformations. The problem is tackled numerically using shooting techniques with the forth order Runga-Kutta method. Pertinent results with respect to embedded parameters are displayed graphically for the velocity,temperature and concentration profiles and were discussed quantitatively.

An aeroelastic metamodel was designed and implemented for prediction of flutter speed and frequency of swept rectangular wings based on experimental data and artificial neural networks (ANN). The ANN is a supervised multilayer perceptron that was trained based on an experimental data set involves flutter characteristics of various cantilever rectangular wing models. Some data were not learned to ANN and were maintained as test cases. The activation functions were tangent hyperbolic and linear function in the hidden and output layers respectively. For learning process, the normalized form of the inputs and outputs were given to the ANN. The ANN learned the relation between the inputs and outputs and was trained for predicting output parameters. It is observed that ANN results are in good agreement with experimental data as well as results of an aeroelasticity code developed using an analytical aerodynamic model. So this ANN can be used for quick prediction of flutter characteristics of swept rectangular wings and also for the study of the effects of various parameters on flutter characteristics of swept rectangular cantilevered wings.

In this paper we present a mathematical analysis for the magneto hydrodynamic (MHD) axi-symmetric stagnation-point flow and heat transfer over a shrinking sheet which shrinks axi-symmetrically in its own plane. The governing partial differential equations along with the boundary conditions are first cast into a dimensionless form and then these equations are solved numerically by shooting technique. Thermal conductivity is assumed to vary linearly with the temperature. Temperature profiles are obtained for two different types of heating process namely (i) the sheet with prescribed surface temperature (PST) and (ii) the sheet with prescribed surface heat flux (PHF). The effects of various physical parameters on the flow and heat transfer characteristics are presented graphically and discussed.

Computational Fluid Dynamics (CFD) analysis for the flow of non-Newtonian and gas-non-Newtonian liquid through elbows is presented. The commercial software Fluent 6.3 has been used for the simulation. Laminar non-Newtonian pseudoplastic power law model has been used for the simulation of non-Newtonian liquid flow through elbows. For twophase flow Elurian-Elurian approach has been used for simulation. The CFD analysis have been tested from our previously published experimental results, Bandyopadhyay and Das (2007), Bandyopadhyay et al. (2000).

Bingham fluid flow through a tapered tube with permeable wall studied. The flow takes place due to pressure gradient, and the porous medium is homogeneous with permeability k. The flow surrounded by the porous medium is governed by the Bingham model, and the flow in the porous medium is governed by the Darcy’s law. The velocity distribution, the volume rate of flow and its fractional increase are obtained. The results are deduced and discussed through graphs.