scholarly journals Turbulent Flow Around Obstacles: Simulation and Study with Variable Roughness

2021 ◽  
Vol 39 (5) ◽  
pp. 1659-1666
Author(s):  
Sidi Mohammed Yousfi ◽  
Khaled Aliane
Keyword(s):  
Three Dimensional ◽  
Computer Code ◽  
Numerical Approach ◽  
Ansys Cfx ◽  
Sst Turbulence Model ◽  
Variable Roughness ◽  
Recirculation Zones ◽  
A New Technique ◽  
Current Lines ◽  
Volume Method

The present work aims to investigate the recirculation and incipient mixing zones in a channel flow supplied with obstacles. The main objective is to develop a new technique to control these recirculation zones by setting a variable roughness. For the purpose of varying that roughness, 4 small bars of heights 0.25H, 0.5H, 0.75H and H were placed downstream of the obstacle; H is the height of the obstacle. For this, a three-dimensional numerical approach was carried out using the ANSYS CFX computer code. In addition, the governing equations were solved using the finite volume method. The K-ω shear-stress transport (SST) turbulence model was utilized to model the turbulent stresses. In the end, we presented the time-averaged simulation results of the contours of the current lines (3D time-averaged streamlines, trace-lines), three components of the velocities: <u> (velocity u contour), <v> (velocity v contour) and <w> (velocity w contour), trace-lines, stream ribbons and mean Q-criterion iso-surface.

scholarly journals Three-dimensional numerical simulation of a turbulent flow around an obstacle

2020 ◽  
Vol 307 ◽  
pp. 01006
Author(s):  
Benahmed Lamia ◽  
Aliane Khaled ◽  
Z. Sari Hassoun
Keyword(s):  
Numerical Simulation ◽  
Velocity Field ◽  
Kinetic Energy ◽  
Three Dimensional ◽  
Governing Equations ◽  
Ansys Cfx ◽  
Recirculation Zones ◽  
Rectangular Obstacle ◽  
Volume Method ◽  
Calculation Code

In this work we study the influence of the inclined shape of the lover and downstream edge of a rectangular obstacle. We analyze the dimensions of the recirculation zones, the velocity field, the kinetic energy and the pressure. A three-dimensional study was conducted using the ansys cfx calculation code. The turbulence model k-ԑ is used to model turbulence, and the governing equations are resolved by the finite volume method.

scholarly journals Simulation and Analysis of a Turbulent Flow Around a Three-Dimensional Obstacle

2019 ◽  
Vol 13 (3) ◽  
pp. 173-180
Author(s):  
Lamia Benahmed ◽  
Khaled Aliane
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Governing Equations ◽  
Complex Behaviour ◽  
Ansys Cfx ◽  
Recirculation Zones ◽  
Volume Method ◽  
Calculation Code

Abstract The study of flow around obstacles is devised into three different positions: above the obstacle, upstream of the obstacle, and downstream of the latter. The behaviour of the fluid downstream of the obstacle is less known, and the physical and numerical modelling is being given the existence of recirculation zones with their complex behaviour. The purpose of the work presented below is to study the influence of the inclined form of the two upper peaks of a rectangular cube. A three-dimensional study was carried out using the ANSYS CFX calculation code. Turbulence models have been used to study the flow characteristics around the inclined obstacle. The time-averaged results of contours of velocity vectors <V>, cross-stream <v> and stream wise velocity <u> and streamlines were obtained by using K-ω shear -stress transport (SST), RANG K-ε and K-ε to model the turbulence, and the governing equations were solved using the finite volume method. The turbulence model K-ω SST has presented the best prediction of the flow characteristics for the obstacle among the investigated turbulence models in this work.

Brick Drying Simulations by Finite Volume Method

2018 ◽  
Vol 930 ◽  
pp. 115-119 ◽  
Author(s):  
R.S. Santos ◽  
D.P.A. Peña ◽  
D.D.S. Diniz ◽  
G.A. Costa ◽  
J.G.A. Queiroz ◽  
...  
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Ceramic Materials ◽  
Structural Ceramics ◽  
Ceramic Brick ◽  
Transient Model ◽  
Ansys Cfx ◽  
Experimental Works ◽  
Temperature Controlled ◽  
Volume Method

There are numerous studies on the application of ceramic materials, such as bricks, in the various engineering and manufacturing fields. Ceramic bricks are manufactured from humidified clay and are classified as structural ceramics. When exposed to drying the process is not precisely controlled, defects such as cracks, deformations and warping can arise, which compromise the final physical and structural properties of the product. Seeking to solve the procedure through simulations, this work presents a numerical study on a brick drying. A three-dimensional transient model is presented to predict the temperature of the holed ceramic brick and the distribution of the humidity content in a drying situation inside a temperature controlled oven, the heat transfer and mass phenomena are present. As simulations were done in the ANSYS CFX® program, which uses the Finite Volumes Method and presented satisfactory results when compared with the experimental works.

Numerical Study on the Flow Characteristics of the Francis Turbine With Various Blade Profiles

2013 ◽  
Author(s):  
J.-H. Jeon ◽  
S.-S. Byeon ◽  
Y.-J. Kim
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Ansys Cfx ◽  
Commercial Code ◽  
Sst Turbulence Model

The Francis turbine is a kind of reaction turbines, which means that the potential energy of water converted to rotational kinetic energy. In this study, the flow characteristics have been investigated numerically in a Francis turbine on the 15 MW hydropower generation with various blade profiles (NACA 65 and NACA 16 series) and discharge angles (14°, 15°, 17°, and 18°), using the commercial code, ANSYS CFX. The k-ω SST turbulence model is employed in the Reynolds averaged Navier-Stokes equations. The computing domain includes the spiral casing, guide vanes, and draft tube, which are discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The results showed that the change of blade profiles and discharge angles significantly influenced the performance of the Francis turbine.

scholarly journals Prediction of Unsteady Natural Convection within a Square Cavity Containing an Obstacle at High Rayleigh Number Value

2015 ◽  
Vol 55 ◽  
pp. 19-26
Author(s):  
Basma Souayeh ◽  
Nader Ben Cheikh ◽  
Brahim Ben Beya ◽  
Taieb Lili
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Stokes Equations ◽  
Computer Code ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Convection Flow ◽  
Square Cavity ◽  
Navier Stokes Equations ◽  
Volume Method

The present work deals with the prediction of a natural convection flow in a square cavity, partially heated by an obstacle placed at the bottom wall. The two transverse walls and the top wall of the cavity are supposed to be cold, the remaining walls are kept insulated. The main parameter of numerical investigations is the Rayleigh number (engine convection) varying from 103 to 105. When Ra is fixed at 107, the flow and thermal fields bifurcate and undergoes an unsteady behavior at critical positions. Flow patterns corresponding to the unsteady state are presented and analyzed in the current study. The simulations were conducted using a numerical approach based on the finite volume method and the projection method, which are implemented in a computer code in order to solve the Navier-Stokes equations.

Three-Dimensional Finite-Volume Method for Incompressible Flows With Complex Boundaries

1992 ◽  
Vol 114 (4) ◽  
pp. 496-503 ◽  
Author(s):  
S. Majumdar ◽  
W. Rodi ◽  
J. Zhu
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Incompressible Flows ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Simple Algorithm ◽  
Computer Code ◽  
Laminar Flows ◽  
Vector Computers ◽  
Volume Method

A finite-volume method is presented for calculating incompressible 3-D flows with curved irregular boundaries. The method employs structured nonorthogonal grids, cell-centered variable arrangement, and Cartesian velocity components. A special interpolation procedure for evaluating the mass fluxes at the cell-faces is used to avoid the nonphysical oscillation of flow variables usually encountered with the cell-centered arrangement. The SIMPLE algorithm is used to handle the pressure-velocity coupling. A recently proposed low diffusive and bounded scheme is introduced to approximate the convection terms in the transport equations. The computer code and the relevant data structure are so organized that most of the code except the implicit linear solver used is fully vectorizable so as to exploit the potential of modern vector computers. The capabilities of the numerical procedure are demonstrated by application to a few internal and external three-dimensional laminar flows. In all cases the CPU-time on a grid with typically 28,000 grid nodes was below half a minute.

Validation of Three-Dimensional Simulation of Flow through Hypersonic Air-breathing Engine

2015 ◽  
Vol 65 (4) ◽  
pp. 272 ◽  
Author(s):  
Thangadurai Murugan ◽  
Sudipta De ◽  
V. Thiagarajan
Keyword(s):  
Separation Bubble ◽  
Three Dimensional ◽  
Symmetry Plane ◽  
Internal Flow ◽  
Air Breathing ◽  
Shock Interactions ◽  
Ansys Cfx ◽  
Compression Region ◽  
Sst Turbulence Model ◽  
Dimensional Simulation

<p>The flow path of a conceptual hypersonic air-breathing scramjet engine integrated with the vehicle (without combustion) has been simulated numerically using ANSYS CFX software with the SST turbulence model. The computations were performed for the free stream Mach number of 6 and angle-of-attack of 5°. A strong separation bubble was observed on the bodyside wall in the internal compression region where the reflected cowl shock impinges on body which in turn increases the static pressure substantially. The external-internal flow field of the hypersonic mixed compression intake, shock-boundary layer interactions, and the shock-shock interactions present in the internal compression region have qualitatively been obtained and analysed. The variation of centreline pressure along the bodyside wall close to the symmetry plane obtained from numerical simulation centreline has been compared with the experimentally measured data. It has been observed that the computed wall pressure matches fairly well with the measured values in the external ramp compression region, internal compression region and in the combustion chamber. The flow patterns and the pressure variations near the middle wall and the fuel injecting strut locations have also been analysed.</p><p><strong>Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 272-278, DOI: http://dx.doi.org/10.14429/dsj.65.6979</strong></p>

A New Way to Form Three-Dimensional Microstructures by Electrochemical Etching of Silicon

2000 ◽  
Vol 638 ◽  
Author(s):  
P. Kleimann ◽  
J. Linnros ◽  
R. Juhasz
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Electrochemical Etching ◽  
Three Dimensional ◽  
Periodic Pattern ◽  
Free Standing ◽  
Vertical Walls ◽  
A New Technique ◽  
Etching Parameters ◽  
Current Lines

AbstractA new technique of bulk micromachining using anodic etching of (100)-oriented n-type silicon is presented. For particular conditions the transition regime between porous silicon formation and electropolishing enables the formation of high aspect ratio microtips which correspond to inverted macropore structures. This unusual property can be explained by the distortion of current lines near the basis of formed structures. The distortion, which prevents the tip dissolution, is due to the electrical field in the space charge region at the silicon-electrolyte interface. The same property can be used to form three-dimensional microstructures. The position and shape of the structures can be defined by forming steps of a few microns depth, prior tothe electrochemical etching. Then the etching parameters (HF concentration, light intensity, etching current density) are adjusted in order to electropolish the sample except where vertical walls are needed. This enables to form microstructures without a periodic pattern. The feasibility of this technique is demonstrated by forming 100μm wide pores, free-standing beams as well as high aspect ratio micro-needles and micro-tubes.

Numerical Investigation of the Roll Decay of a Container Ship Moving With Forward Speed in Calm Water

2019 ◽  
Author(s):  
Adrian Lungu
Keyword(s):  
Fluid Motion ◽  
Three Dimensional ◽  
Time History ◽  
Numerical Approach ◽  
Container Ship ◽  
Angle Variation ◽  
Sst Model ◽  
Calm Water ◽  
History Of ◽  
Volume Method

Abstract In the present paper the roll damping decay is investigated for the KRISO Container Ship in various working conditions. For this purpose flow is simulated by solving numerically the unsteady three dimensional equations of fluid motion in which closure to the turbulence is achieved through the DES-SST model. The governing equations are solved by using the finite volume method and the free surface elevation is determined by using a VOF technique. Comparisons with the experimental data are provided to validate the numerical approach in terms of the time history of the roll angle variation for different roll motions and ship speeds.

scholarly journals Numerical Simulation of Free Convection in a Partially Heated Three-Dimensional Enclosure Filled with Ionanofluid ([C4mim][NTf2]-Cu)

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Said Bouchta ◽  
M’barek Feddaoui ◽  
Abdellatif Dayf
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Free Convection ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Three Dimensional ◽  
Particle Volume ◽  
Simplec Algorithm ◽  
Current Lines ◽  
Volume Method

A numerical analysis was performed to study free convection in a stationary laminar regime in a partially heated cube filled with ionanofluid. To numerically solve the dimensionless equations, we applied the finite volume method using the SIMPLEC algorithm for pressure correction. All walls are adiabatic, except for the left and right side walls which are partially heated differently. At the end of this simulation, several results are given in the form of current lines, isotherms, and variations in the Nusselt number. These results are obtained by analyzing the effect of a set of factors such as Rayleigh number, particle volume fraction, cold and source position on the dynamic and thermal fields, and heat transfer. It has been shown that the percentage of nanoparticles and high Rayleigh numbers significantly increase heat transfer by ionanofluid. Two comparisons have been made, between ionic fluid and ionanofluid at isotherms and streamlines, and between nanofluid and ionanofluid at Nusselt number, which show the advantage of using ionanofluid in heat transfer.

Sign in / Sign up

Export Citation Format

Share Document