Numerical Investigation of Steady Density Currents Flowing Down an Incline Using v2¯−f Turbulence Model

2007 ◽  
Vol 129 (9) ◽  
pp. 1172-1178 ◽  
Author(s):  
Nima Khakzad ◽  
Bahar Firoozabadi ◽  
Bijan Farhanieh
Keyword(s):  
Turbulence Model ◽  
Momentum Equation ◽  
Density Currents ◽  
Governing Equations ◽  
Relaxation Equation ◽  
Elliptic Relaxation ◽  
High Reynolds ◽  
Volume Method ◽  
Dominant Parameter ◽  
Good Agreement

The governing equations of two-dimensional steady density currents are solved numerically using a finite volume method. The v2¯−f turbulence model, based on standard k−ε model, is used for the turbulence closure. In this method, all Reynolds stress equations are replaced with both a transport equation for v2¯ and an elliptic relaxation equation for f, a parameter closely related to the pressure strain redistribution term. The Simple-C procedure is used for pressure-velocity coupling. In addition, Boussinesq’s approximation is used to obtain the momentum equation. The computed height of the progressive density current is compared to the measured data in the literature, resulting in good agreement. The present results show that the flow rate is the most dominant parameter among those affecting the density currents hydrodynamics. The results also show that the v2¯−f turbulence model is able to predict and simulate the characteristics of the low Reynolds turbulent density currents successfully, although it is based on a high Reynolds number turbulence model, i.e., the standard k−ε model. The use of boundary layer convention, saying that the density current’s height is a height at which the concentration is ∼1% of the inlet concentration, seems to yield reasonable results.

scholarly journals NUMERICAL AND EXPERIMENTAL STUDY OF A FREE INCOMPRESSIBLE ISOTHERMAL TURBULENT COAXIAL JET

2010 ◽  
Vol 9 (1-2) ◽  
pp. 98 ◽  
Author(s):  
G. R. Ströher ◽  
C. A. Martins ◽  
C. R. De Andrade
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Velocity Ratio ◽  
Radial Profile ◽  
Mass Conservation ◽  
Experimental Measurements ◽  
Governing Equations ◽  
Self Similarity ◽  
Mean Velocity ◽  
Volume Method

In the present study the free incompressible isothermal turbulent coaxial jet problem is numerically solved, and compared with experimental measurements for different velocity ratio between the inner and the outer streams of the jet. The radial profile of the axial mean velocity was obtained with hot anemometry at different axial positions. Governing equations (mass conservation, momentum, turbulence model) were discretized employing the finite volume method with a segregated solver. The analysis of the experimental results showed that coaxial jet flow fields did not present self-similarity up to z/D=25, and the numerical solution using the Shih’s k ε turbulence model did not match reasonably with the experimental data, with a difference of about ± 10%.

Prediction of a Turbulent Flow in Bluff Body Stabilized Burner by Using Two Classical Models of Turbulence

2017 ◽  
Vol 32 ◽  
pp. 112-123
Author(s):  
Merouane Habib
Keyword(s):  
Turbulent Flow ◽  
Bluff Body ◽  
Diameter Ratio ◽  
Governing Equations ◽  
Quadrilateral Elements ◽  
Annular Jet ◽  
Classical Models ◽  
Resolution Scheme ◽  
Volume Method ◽  
Good Agreement

In present study, a detailed investigation of an annular jet at high diameter ratio r = 0,905 has been reported numerically. The numerical simulation was performed by making use of the commercial CFD code which discretizes the solution domain into quadrilateral elements and use a numerical finite volume method coupled with a multigrid resolution scheme. In this research the applications of k-epsilon and k-omega models for prediction of a turbulent flow in annular jet are described. The flow governing equations are solved by using a performed coupled algorithm. The results of predicted axial velocity profiles are compared with the experimental data. The computations indicated that the results predicted by k-epsilon model are in good agreement with the experiment.

scholarly journals Numerical Performance of Higher-Order Semicompact Scheme for Arbitrary Triangular Cavity Flow

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaofeng Wang ◽  
Dongyang Shi
Keyword(s):  
Reynolds Numbers ◽  
Higher Order ◽  
Curvilinear Coordinates ◽  
Navier Stokes ◽  
Governing Equations ◽  
Arbitrary Geometry ◽  
Present Scheme ◽  
Numerical Performance ◽  
High Reynolds ◽  
Good Agreement

An efficient fourth-order semicompact finite difference scheme has been developed to solve steady incompressible Navier-Stokes (N-S) equations in stream function and vorticity formulation in a triangular cavity of arbitrary geometry. The governing equations are transformed into curvilinear coordinates by a simple linear transformation to handle the nonregular geometry of the problem. The main feature of the new higher-order semicompact scheme is that it can calculate a triangle flow with arbitrary shape for high Reynolds numbers. It is found that the solutions obtained with the present scheme are in good agreement with the analytical results or with the existing results depending on the availability.

Numerical Simulation of Turbid-Density Current Using v2 – f Turbulence Model

2005 ◽  
Author(s):  
A. Mehdizadeh ◽  
B. Firoozabadi ◽  
B. Farhanieh
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Isotropic Turbulence ◽  
Turbidity Current ◽  
Solid Particles ◽  
Density Currents ◽  
Complex Flow ◽  
Fall Velocity ◽  
High Reynolds ◽  
Near Wall

The deposition behavior of fine sediment is an important phenomenon, and yet unclear to engineers concerned about reservoir sedimentation. An elliptic relaxation turbulence model (v2 – f model) has been used to simulate the motion of turbid density currents laden whit fine solid particles. During the last few years, the v2 – f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v2 – f model to be superior to other RANS methods in many fluid flows where complex flow features are present. Due to low Reynolds number turbulence of turbidity current, (its critical Reynolds no. is about 1000), the κ - ε model, which was standardized for high Reynolds number and isotropic turbulence flow, cannot simulate the anisotropy and non-homogenous behavior near wall. In this study, turbidity current with uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with experimental data sets. Moreover, results have been compared with the standard κ - ε turbulent model. Results show that the κ - ε model has the poor result on this current. In addition, results show that the coarse particles settle down rapidly and make the higher deposition rate. The deposition of particles and the effects of their fall velocity on concentration distribution, height of body, and entrainment coefficient are also investigated.

Laminar Free Convection in Inclined Enclosures Filled With a Fluid Saturated Porous Medium

Volume 1 ◽  
2004 ◽  
Author(s):  
Edimilson J. Braga ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Porous Medium ◽  
Saturated Porous Medium ◽  
Governing Equations ◽  
Flow And Heat Transfer ◽  
Different Temperatures ◽  
Laminar Natural Convection ◽  
Fluid Saturated Porous Medium ◽  
Volume Method ◽  
Generalized Coordinate ◽  
Good Agreement

Detailed numerical computations for steady-state laminar natural convection within in oblique cavities totally filled with a fluid saturated porous medium is numerically analyzed using the finite volume method in a generalized coordinate system. The inclined walls are maintained at constant but different temperatures, while the horizontal walls are kept insulated. Governing equations are written in terms of primitive variables and are recast into a general form. Flow and heat transfer characteristics, (streamlines, isotherms and average Nusselt number), are investigated for Rayleigh number ranging from 103 to 104 and inclined angles ranging from 0° to 45°. In general, present results show good agreement with previous works. Analyses of important environmental and engineering flows can benefit from the derivations herein and, ultimately, it is expected that additional research on this new subject be stimulated by the work here presented.

scholarly journals Natural convection in a square inclined enclosure with vee-corrugated sidewalls subjected to constant flux heating from below

2011 ◽  
Vol 16 (2) ◽  
pp. 152-169 ◽  
Author(s):  
Salam Hadi Hussain ◽  
Ahmed Kadhim Hussein ◽  
Mahmoud Moustafa Mahdi
Keyword(s):  
Natural Convection ◽  
Inclination Angle ◽  
Bottom Wall ◽  
Dimensionless Temperature ◽  
Governing Equations ◽  
Fluid Properties ◽  
Inclined Enclosure ◽  
Volume Method ◽  
Heating From Below ◽  
Good Agreement

Two-dimensional steady natural convective flow in a square inclined enclosure with vertical vee-corrugated sidewalls and horizontal top and bottom surfaces has been numerically studied. A discrete heat flux strip of 24% of the total length is flush-mounted on the bottom wall, while the other non-heated parts of the bottom wall and the top wall are considered adiabatic. The two vee-corrugated sidewalls are maintained at constant cold temperature. Grashof number is varied from 103 to 106, corrugation frequency is varied from 0.5 to 2.0, corrugation amplitude has been fixed at 10% of the enclosure height and the enclosure inclination angle is varied to 0◦, 10◦, 20◦ and 30◦ respectively. The enclosure is filled with air (Pr = 0.71). The flow has been assumed to be steady and laminar. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The solution has been obtained using the governing equations written in terms of dimensionless variables. The dimensionless governing equations are solved using finite volume method. Results are presented in the form of streamline and isotherm plots. The results of the present work show that the natural convection phenomenon is greatly affected by increasing the enclosure inclination angle. The variation in the average Nusselt number at the bottom wall, where the heat source exists and the maximum dimensionless temperature are also presented. The results are compared and found to be in a good agreement with other published results.

Numerical Simulations of Flow Around Wall-Mounted Square and Trapezoidal Structures at High Reynolds Numbers

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Martin Andersen ◽  
Guang Yin ◽  
Muk Chen Ong
Keyword(s):  
Turbulence Model ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Freestream Velocity ◽  
High Reynolds Numbers ◽  
Sst Turbulence Model ◽  
Layer Flow ◽  
High Reynolds ◽  
Two Sides ◽  
Good Agreement

Abstract In the present study, flow around symmetric trapezoidal wall-mounted structures with different slope angles of the two sides subjected to a boundary layer flow at Reynolds numbers of 1.19 × 105 and 1 × 106 (based on the height of the structures and the freestream velocity) is investigated using two-dimensional (2D) Reynolds-averaged Navier–Stokes (RANS) equations combined with the k − ω shear stress transport (SST) turbulence model. It is found that the drag coefficient of the wall-mounted square structures using the k − ω SST turbulence model is in good agreement with the available published experimental data. The effects of slope angles of the two sides on the hydrodynamic quantities and the flow fields around the structures have been investigated.

Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

2003 ◽  
Vol 3 (1-2) ◽  
pp. 201-207
Author(s):  
H. Nagaoka ◽  
T. Nakano ◽  
D. Akimoto
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Turbulence Model ◽  
Uptake Rate ◽  
Oscillatory Flow ◽  
Substrate Uptake ◽  
Flow Conditions ◽  
Mass Transfer Mechanism ◽  
Substrate Uptake Rate ◽  
Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

scholarly journals The Influence of Different Types of Nanofluid on Thermal and Fluid Flow Performance of Liquid Cold Plate

2018 ◽  
Vol 7 (4.35) ◽  
pp. 148 ◽  
Author(s):  
Nur Irmawati Om ◽  
Rozli Zulkifli ◽  
P. Gunnasegaran
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Steady State ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Cold Plate ◽  
Governing Equations ◽  
Flow And Heat Transfer ◽  
Different Types ◽  
Volume Method

The influence of utilizing different nanofluids types on the liquid cold plate (LCP) is numerically investigated. The thermal and fluid flow performance of LCP is examined by using pure ethylene glycol (EG), Al2O3-EG and CuO-EG. The volume fraction of the nanoparticle for both nanofluid is 2%. The finite volume method (FVM) has been used to solved 3-D steady state, laminar flow and heat transfer governing equations. The presented results indicate that Al2O3-EG able to provide the lowest surface temperature of the heater block followed by CuO-EG and EG, respectively. It is also found that the pressure drop and friction factor are higher for Al2O3-EG and CuO-EG compared to the pure EG.

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