Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
41
3
2014
Numerical Investigation of Symmetrical Supersonic Inlet with Boundary Layer Suction
185-193
10.1615/InterJFluidMechRes.v41.i3.10
Ali Momeny
Sarmazdeh
Department of Mechanical Engineering, Iran University of Science and Technology Tehran, Iran
Mojtaba
Tahani
Faculty of New Sciences and Technologies, Tehran University, Tehran, Iran
Mohsen Motahari
Nezhad
Department of Mechanical Engineering, Iran University of Science and Technology Tehran, Iran
In this study, an input stream of symmetrical supersonic inlet with boundary layer suction has been investigated by using of two-dimensional full Navier−Stokes equations. The analysis has been performed for three various Mach numbers. The main purpose of this study is reduction of adverse pressure gradient for performance improvement of supersonic air-intake. At this paper, the upper leading edge has been considered round because the sharp leading edge cannot withstand the high thermal loading in supersonic flow. The results show that the high pressure gradient across the crossing shock waves has been minimized by the use of boundary layer suction. So, the input mass flow rate to air-intake has been increased. Viscose and non-viscose Turbulent flow analysis has been done by McCormack explicit method. Modeling of turbulent flow has been done with Wilcox k-ω two equations model. The results have been compared with the prestigious experimental papers at the end.
Analysis of Supercritical Flow In Suddenly Expanding Channel
194-220
10.1615/InterJFluidMechRes.v41.i3.20
Sumit
Gandhi
Jaypee University of Engineering & Technology, Guna India
The experimental analysis is carried out to study the variation of flow characteristics namely sequent depth ratio (Y2 / Y1), Relative height of jump (hj / Y1), relative energy loss (EL / E1), Efficiency (E2 / E1), Relative length of jump (Lj / Y1) and relative length of roller (Lr / Y1) of the hydraulic jump for suddenly expanding channel for different B1 / B2 (expansion) ratio. Dimension of baffle blocks and end sill are also considered as the third variable. Explanations of the variation of these characteristics with approach Froude number is presented based on experiments. Empirical models are presented using Buckinham's π-theorem; these models are tested, validated and compared with other authors result. Modifications in energy dissipation as a result of application of appurtenances are obtained showing usefulness to its dimensions.
A 3D Lattice Boltzmann Method for Simulation of Fluid Flow in Porous Media
221-237
10.1615/InterJFluidMechRes.v41.i3.30
Ahmad Reza
Rahmati
Department of Mechanical Engineering, University of Kashan, Kashan, Iran
Mehrdad Naderi
Beni
Department of Mechanical Engineering Faculty of Engineering, University of Kashan Kashan, Iran
In the present work, a three-dimensional lattice Boltzmann method (LBM) is applied to simulate fluid flow in porous media. The influence of porous media is considered by introducing the porosity to the equilibrium distribution function. The velocity field in the system solved by adding The Brinkman and Forcheimer's terms (the linear and nonlinear drag forces term) to the lattice Boltzmann formulation. Investigations were performed with different Darcy number to exemaine the influence of porosity on the fluid flow in three-dimensional lid-driven cavity. The obtained results indicate that the lattice Boltzmann method is capable to simulate fluid flow in porous media.
Numerical Investigations of Oscillatory Motions of a Rotating Viscoelastic Nanofluid Layer in Natural Convection
238-259
10.1615/InterJFluidMechRes.v41.i3.40
Veena
Sharma
Himachal Pradesh University Shimla-171 005
Anuradha
Chowdhary
Department of Mathematics & Statistics H.P.University, Shimla, India
Renu
Kumari
Department of Mathematics & Statistics H.P.University, Shimla, India
The present work aims at studying the oscillatory motions of a rotating viscoelastic nanofluid layer contained between two free boundaries in natural convection. The Oldroyd-B model is utilized to describe the rheological behaviour of a viscoelastic fluid. The model used for nanofluid combines the effect of Brownian motion along with thermophoresis. Using linear stability analysis, the main focus is on the stationary and oscillatory convection for idealized boundary conditions. The explicit expressions of convective thresholds in terms of the control parameters of the system are obtained. The effects of the Deborah number, retardation parameter, concentration Rayleigh number, Prandtl number, Taylor number and Lewis number on the stability of the system have been investigated. Results indicate that there was competition among the processes of thermophoresis, Brownian diffusion, angular velocity and viscoelasticity which cause oscillatory rather than stationary convection to occur. Oscillatory instability is possible with both bottom- and top-heavy nanoparticle distributions. Regimes of stationary and oscillatory convection for various parameters have been derived numerically and discussed in detail.
Rigid Bodies without Boundary-Layer Separation
260-281
10.1615/InterJFluidMechRes.v41.i3.50
Igor G.
Nesteruk
Institute of Hydromechanics of National Academy of Sciences of Ukraine 8/4, Zhelyabov St., 03680, Kyiv-180, MSP, Ukraine
Shapes with a special pressure distribution can prevent boundary-layer separation and as a result can allow both reduction of drag and noise without any active flow-control methods. Examples of such axisymmetric and 2D shapes with favourable pressure gradients both up- and downstream of the maximum thickness point have been calculated with the use of a linearized approach as well as by exact solutions of the Euler equations for steady flows of an ideal fluid. The zone of positive pressure gradient can be diminished to just 0.3 % of the total body length. It is shown that similar shapes with negative pressure gradients can be obtained for sub- and supersonic flows of compressible fluid. Wind-tunnel tests with axisymmetric bodies have shown that separation can be avoided on some of these shapes.