Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
35
5
2008
Effect of Labyrinth Cavities on Cavitation Reduction in a Conical Valve
395-416
S. P.
Asok
Department of Mechanical Engineering, Mepco Schlenk Engineering College (MSEC), Sivakasi, India
K.
Sankaranarayanasamy
Department of Mechanical Engineering, National Institute of Technology, Tiruchirapalli, India
Thirumalachari
Sundararajan
Thermodynamics and Combustion Engineering
Laboratory Department of Mechanical Engineering
Indian Institute of Technology Madras, Chennai – 600036, India
R.
Manivannan
Department of Mechanical Engineering, Mepco Schlenk Engineering College (MSEC), Sivakasi, India
High-intensity cavitation occurring in water flow past a valve causes vibration, noise, fatigue, and erosion of the valve and the associated piping. This paper aims to reduce cavitation through a design modification on the tapering body of a conical valve. The flow and cavitation characteristics of two different 1 in sized hydraulic conical valves have been investigated. The first one is a conventional conical valve (CCV). The newly designed second valve has labyrinth cavities on the conical valve body and hence is named the labyrinth conical valve (LCV). Computational fluid dynamics (CFD) simulations identified LCV to cavitate less than CCV. To validate the CFD predictions, different experiments were conducted. The predicted mass flow rates were found to be in close agreement with the experimental results. The bubble flow patterns of the valves were indistinguishable in visual observation. Hence, a detailed digital image processing (DIP) analysis was invoked. It showed that the cavitating flow through a LCV possessed both less bubble pixel count and bubble image entropy attributable to low cavitation. Further endorsement was obtained through a bacterial testing method using the interesting fact that cavitation can disinfect water. This test indicated that the number of E. coli bacterial colonies in the water handled by a LCV is larger compared to that of a CCV, thus confirming that the LCV is a low-cavitation valve.
Non-Newtonian Power Law Fluid Flow and Heat Transfer in a Porous Medium Over a Nonisothermal Stretching Sheet
417-433
P. S.
Datti
School of Mathematics, TIFR Centre, Indian Institute of Science Campus, Bangalore, India
K. V.
Prasad
Department of Mathematics, Central College Campus, Bangalore University, Bangalore, India
In this paper, we present a numerical solution for heat transfer in the flow of a non-Newtonian power law fluid immersed in a saturated porous medium over a nonisothermal stretching sheet in the presence of internal heat generation/absorption. Thermal conductivity is assumed to vary as a linear function of temperature. Similarity transformations are used to convert highly nonlinear partial differential equations into ordinary differential equations. The resulting coupled nonlinear ordinary differential equations are solved numerically by the efficient Keller box method for two different cases, namely, a surface with prescribed surface temperature and surface with prescribed wall heat flux. The important findings of our study are that the effect of the power law index is to decrease the horizontal velocity boundary layer thickness and thermal boundary layer thickness. The effect of the porous parameter is to reduce the horizontal boundary layer thickness and increase the thermal boundary layer thickness.
Unsteady Free Convection in a Fluid Past a Vertical Plate Immersed in a Porous Medium
434-444
Mohamed F.
El-Amin
Mathematics Department, Aswan Faculty of Science, South Valley University, Aswan, 81258; King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
Rama Subba Reddy
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
In this work we examine the problem of unsteady free convection from a vertical flat plate to a fluid-saturated porous medium. The flow field is modeled by Darcy−Brinkman−Forchheimer model. Boundary layer and Boussinesq approximations have been incorporated. Numerical calculations are carried out for the various parameters entering into the problem using the finite difference method. It is found that as time approaches infinity, the values of friction factor and heat transfer coefficient approach the steady-state values.
Boundary Layer Natural Convection in a Fluid Saturated Porous Medium Using Finite Element Method
445-458
Mohamed F.
El-Amin
Mathematics Department, Aswan Faculty of Science, South Valley University, Aswan, 81258; King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
Ibrahim
Abbas
Mathematics Department, Sohag Faculty of Science, South Valley University, Sohag
Rama Subba Reddy
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
The present paper considers a numerical study of the non-Darcy natural convection over a vertical flat plate in a fluid-saturated porous medium. Forchheimer extension is considered in the flow equations. The nondimensional governing equations are solved by the finite element method. The resulting nonlinear integral equations are linearized and solved using the Newton−Raphson iteration. The finite element implementations are prepared by using the MATLAB® software packages. Numerical results for the details of the stream function, velocity, and temperature contours and profiles, as well as heat transfer rate in terms of Nusselt number, which are shown on graphs, have been presented.
Non-Darcy Mixed Convection Flow of Non-Newtonian Fluids on a Vertical Surface in a Saturated Porous Medium
459-474
Mahesh
Kumari
Department of Mathematics, Indian Institute of Science, Bangalore 560 012, India
S.
Jayanthi
Department of Mathematics, Indian Institute of Science, Bangalore 560012, India
A non-Darcy mixed convection flow along a vertical plate in a non-Newtonian fluid-saturated porous medium is investigated. A single mixed convection parameter has been used that covers the entire regime of mixed convection from pure forced to pure free convection limits. The dimensionless equations governing the flow are solved numerically. Numerical results for the velocity, temperature, and heat transfer at the wall are presented for various values of the parameters, namely, the Ergun number, Rayleigh number, or Peclet number, viscosity index, mixed convection parameter, and the temperature variation parameter. Results for free and mixed convection flows are compared with the existing results.
Dispersion in Oscillatory Couette Flow with Absorbing Boundaries
475-492
B. S.
Mazumder
Fluvial Mechanics Laboratory Physics and Applied Mathematics Unit Indian Statistical Institute Kolkata - 700108, India
Suvadip
Paul
Physics & Applied Mathematics Unit, Indian Statistical Institute Calcutta, India
This paper presents the longitudinal dispersion of passive contaminant released in an incompressible viscous fluid flowing between two infinite parallel plates, where the contaminant undergoes irreversible heterogeneous reaction with the boundary walls. The flow is driven by the oscillation of the upper plate in its own plane with a constant velocity as well as by an imposed constant pressure gradient. This type of flow may be termed unsteady generalized Couette flow. A finite difference implicit scheme has been adopted to solve the unsteady convection-diffusion equation for all time periods based on the Aris method of moments. The influence of applied constant pressure gradient, oscillation of the upper plate, and the absorption parameter at both walls on dispersion is discussed. The dispersion coefficients are obtained for three different flow situations: plane and generalized Couette flow, unsteady generalized Couette flow, and for comparison, the combined effect of steady and unsteady Couette flows, separately. The most striking result is that unlike the case of parallel flow under periodic pressure gradient, the double-frequency period in the dispersion phenomena does not vanish, even for the high frequency of upper-plate oscillation for the case of unsteady generalized Couette flow. The axial distributions of mean concentration are determined from the first four central moments using Hermite polynomial representation for the periodic flow with or without nonzero mean flow.