CFD Simulation of Coaxial Jet Mixer Using RANS Turbulent Models

2012 ◽  
Vol 326-328 ◽  
pp. 416-421 ◽  
Author(s):  
Ku Zilati Ku Shaari ◽  
Afiq Mohd Laziz ◽  
Kerstin Heinen ◽  
Mokhtar Awang ◽  
Suriati Sufian ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Cfd Simulation ◽  
Navier Stokes ◽  
Suitable Model ◽  
Navier Stokes Equation ◽  
Rans Model ◽  
Turbulent Models ◽  
Simulation Time ◽  
Selection Of ◽  
Good Agreement

The Reynolds Averaged Navier Stokes Equation (RANS) model was used to describe the turbulent flow in a coaxial jet mixer. The effects of turbulent models on the turbulent flow is investigated to help the engineers and researchers in deciding the selection of turbulent model need to be used in order to save the simulation time and to predict the best suitable model to be used. Good agreement of the CFD prediction with the experimental data in certain locations was obtained with species transport and velocity profiled, where dependence of turbulent models and grid sizes were discussed in detail. The results show that, the need of grid study is crucial to obtain reliable results with optimum consumption of computer power. SST and Launder Gibson RSTM models give results superior to the other models, each of which has its own area of capability. Launder Gibson RSTM is good in predicting the flow with recirculation and vortices, while SST is good for the flow with less recirculation and high velocity. The overall results show that RANS model is capable in predicting the area of mixing and the velocity profile correctly in certain locations but not in reproducing the vortices structure in the pipe and nozzle.

A Verification and Validation Study of CFD Simulation of Wind-Induced Ventilation on Building with Single-Sided Opening

2014 ◽  
Vol 554 ◽  
pp. 696-700 ◽  
Author(s):  
Nur Farhana Mohamad Kasim ◽  
Sheikh Ahmad Zaki ◽  
Mohamed Sukri Mat Ali ◽  
Ahmad Faiz Mohammad ◽  
Azli Abd Razak
Keyword(s):  
Open Source Software ◽  
Natural Ventilation ◽  
Cfd Simulation ◽  
Previous Experiment ◽  
Experimental Methods ◽  
Verification And Validation ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Computational Fluid Dynamics Cfd ◽  
Model Approach

Wind-induced ventilation is widely acknowledged as one of the best approaches for inducing natural ventilation. Computational fluid dynamics (CFD) technique is gaining popularity among researchers as an alternative for experimental methods to investigate the behavior of wind-driven ventilation in building. In this present paper, Reynolds averaged Navier-Stokes equation (RANS) k-ε model approach is considered to simulate the airflow on a simplified cubic building with an opening on a single façade. Preliminary simulation using models from previous experiment indicates the reliability of OpenFOAM, the open source software that will be used in this study. The results obtained in this study will better define options for our future study which aims to explore how different buildings arrays modify the airflow inside and around a naturally ventilated building.

The Reynolds Stress in Channel Flows From a Lagrangian Treatment of the Turbulence Momentum

2019 ◽  
Author(s):  
T.-W. Lee
Keyword(s):  
Turbulent Flow ◽  
Reynolds Stress ◽  
Current Approach ◽  
Navier Stokes ◽  
Current Transport ◽  
Lagrangian Analysis ◽  
Navier Stokes Equation ◽  
Mechanistic Approach ◽  
Turbulent Momentum

Abstract We have developed a mechanistic approach for determination of the Reynolds stress, using a Lagrangian analysis of turbulent momentum. Analysis and comparison with DNS and experimental data point toward the soundness of this approach (Lee, 2018). von Karman constant, the inner layer thickness and the Reynolds stress itself are all recovered through this approach, in agreement with DNS data. In addition, the turbulent flow profiles can be calculated iteratively using the basic Reynolds-averaged Navier-Stokes equation, in conjunction with the current transport equation for the Reynolds stress. In this work, we explore these and further uses of the current approach in solving turbulent flow dynamics.

Wave-in-Deck Load on a Jacket Platform, CFD Calculations Compared With Experiments

2014 ◽  
Author(s):  
Bogdan Iwanowski ◽  
Tone Vestbøstad ◽  
Marc Lefranc
Keyword(s):  
Free Surface ◽  
Industrial Application ◽  
Computational Models ◽  
Cfd Simulation ◽  
Navier Stokes ◽  
Extreme Wave ◽  
Navier Stokes Equation ◽  
Jacket Platform ◽  
Irregular Wave ◽  
Start Up

The paper presents an industrial application of CFD for calculation of Wave-In-Deck load due to an extreme wave. Particular attention is given to flow kinematics initialization that is necessary to start up a CFD simulation. The applied CFD code, ComFLOW, is a Navier-Stokes equation solver with an improved Volume of Fluid (iVOF) method employed to displace and re-construct fluids free surface. For incoming waves high enough for a negative air-gap and therefore with Wave-In-Deck loads, a jacket platform was tested in model basin, for both regular and irregular wave cases. One of goals of these model tests was verification of CFD codes. The experimental and computational models of the structure are exactly the same. In the paper, the measured Wave-In-Deck forces are compared with CFD results.

Flow resistance of ice-covered streams

1984 ◽  
Vol 11 (4) ◽  
pp. 815-823 ◽  
Author(s):  
S. P. Chee ◽  
M. R. I. Haggag
Keyword(s):  
Velocity Profile ◽  
Channel Flow ◽  
Flow Resistance ◽  
Ice Cover ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Cross Sectional ◽  
Roughness Elements ◽  
Mixing Length Theory ◽  
Good Agreement

This paper deals with the underlying theory of the hydraulics of channel flow with a buoyant boundary as an ice cover. It commences by developing the velocity distribution in two-dimensional covered channel flow using the Reynolds form of the Navier–Stokes equation in conjunction with the Prandtl – Von Karman mixing length theory. Central to the theory is the division of the channel into two subsections. From the developed velocity profile, the functional relationship for the division surface is obtained. Finally, the composite roughness of the channel is derived.Experimental verification of the developed theory was conducted in laboratory flumes. Seven cross-sectional shapes were utilized. Ice covers were simulated with polyethylene plastic pellets as well as floating plywood boards with roughness elements attached to the underside. Velocity profile and composite roughness measurements made in these flumes were in good agreement with the theoretical equations. The composite roughness relationship derived from the theory is very comprehensive, as it takes into account not only the varying rugosities of the channel and its floating boundary but also the shape of the cross section. Key words: composite roughness, ice cover, flow resistance, velocity profile, buoyant boundary, covered channel.

scholarly journals CFD Simulation Study on the Performance of a Modified Ram Air Turbine (RAT) for Power Generation in Aircrafts

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 391
Author(s):  
Magedi Moh M. Saad ◽  
Sofian Mohd ◽  
Mohd Fadhli Zulkafli ◽  
Nor Afzanizam Samiran ◽  
Djamal Hissein Didane
Keyword(s):  
Fossil Fuels ◽  
Cfd Simulation ◽  
Turbulence Modeling ◽  
3D Models ◽  
Navier Stokes ◽  
Axial Distance ◽  
Navier Stokes Equation ◽  
Auxiliary Power Unit ◽  
Auxiliary Power ◽  
Air Turbine

The present paper aims to study the possibility of dispensing an auxiliary power unit (APU) in an aircraft powered by fossil fuels to reduce air pollution. It particularly seeks to evaluate the amount of power generated by the ram air turbine (RAT) using the novel counter-rotating technique while characterizing its optimum axial distance. The ram air turbine (RAT), which is already equipped in aircrafts, was enhanced to generate the amount of energy produced by the APU. The approach was implemented by a CRRAT system. Six airfoil profiles were tested based on 2D models and the best airfoil was chosen for implantation on the RAT and CRRAT systems. The performance of the conventional single-rotor RAT and CRRAT were analyzed using FLUENT software based on 3D models. The adopted numerical scheme was the Navier–Stokes equation with k–ω SST turbulence modeling. The dynamic mesh and user-defined function (UDF) were used to revolve the rotor turbine via wind. The results indicated that the FX63-137 airfoil profile showed a higher performance in terms of the lift-to-drag ratio compared to the other airfoils. The optimum axial distance between the two rotors was 0.087 m of the rotor diameter and the efficiency of the new CRRAT increased to almost 45% compared to the single-rotor RAT.

Validation of the INS3D-UP Code in the Prediction of Turbulent Flow of Liquid Propellants in a Sharp Bend

1995 ◽  
Author(s):  
M. A. R. Sharif ◽  
J. T. Haskew
Keyword(s):  
Turbulent Flow ◽  
Space Shuttle ◽  
Circular Cross Section ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Sharp Bend ◽  
Flow Problems ◽  
Fortran Code ◽  
Main Engine ◽  
Liquid Propellants

Abstract The capability of the INS3D-UP code in the prediction of turbulent flow in a sharp bend of circular cross-section has been investigated. The code, developed by the NASA Ames Research Center, is being used by the NASA Marshal Space Flight Center to analyze turbulent flow of liquid propellant in vaned pipe bends designed for use in the Space Shuttle Main Engine. The FORTRAN code is based on finite difference method and uses the concept of pseudocompressibility to solve incompressible Navier-Stokes equation. The Baldwin-Barth turbulence model is embedded in the code for turbulence computation. The flow field, at a Reynolds number of 43,000, in a sharp 90° bend has been predicted and compared with measurement. It is found that the agreement between the predicted and measured velocities is very well. The predicted pressures at the bend wall also compares reasonably well with the measurement. It is concluded that the INS3D-UP code is a good computational tool to analyze similar flow problems.

scholarly journals Selection of quasi-stationary states in the Navier–Stokes equation on the torus

Nonlinearity ◽  
2018 ◽  
Vol 32 (1) ◽  
pp. 209-237 ◽  
Author(s):  
Margaret Beck ◽  
Eric Cooper ◽  
Konstantinos Spiliopoulos
Keyword(s):  
Stokes Equation ◽  
Navier Stokes ◽  
Stationary States ◽  
Navier Stokes Equation ◽  
Selection Of

A Transient CFD Simulation of the Flow in a Test Rig of an Aeroengine Bearing Chamber

2014 ◽  
Author(s):  
Akinola A. Adeniyi ◽  
Hervé P. Morvan ◽  
Kathy A. Simmons
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Film Formation ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Oil Film ◽  
Sheared Flow ◽  
Fine Mesh ◽  
Computational Overhead ◽  
Formation Pattern

In this paper, we present results for the application of an Eulerian-Lagrangian technique to the transient simulation of an oil film formation on the walls of an aeroengine bearing chamber. The flow of oil in an aeroengine bearing chamber consists of high speed oil droplets interacting with the bearing structures and flowing oil film. The situation in the chamber is highly rotational and consisting of sheared flow of air over oil. The bearing chamber may also be located in the vicinity of the combustion chamber. The oil provides lubrication and cooling of the hot structures. Modelling the flow in the bearing chamber is therefore complex. The Volume of Fluid (VoF) technique offers a potential platform to model droplet-film interaction; however, it requires fine mesh details to capture the flow to the droplet level. Such detailed resolution would not be practical for the complete chamber geometry because of the prohibitively expensive computational overhead requirements. A Lagrangian formulation is therefore proposed to represent the droplets as source terms in the Navier-Stokes equation while the film is represented using VoF. This effectively reduces the need to resolve the droplets explicitly. The predicted film formation pattern compares with experimental results.

Preliminary Imaging of Red Blood Cells in Turbulent Flow

2012 ◽  
Author(s):  
Mostafa Shakeri ◽  
Iman Khodarahmi ◽  
M. Keith Sharp
Keyword(s):  
Turbulent Flow ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Imaging System ◽  
Navier Stokes ◽  
Viscous Stress ◽  
Damage Potential ◽  
Navier Stokes Equation ◽  
Considerable Uncertainty ◽  
Mathematical Construct

Considerable uncertainty exists about how momentum and energy are transferred to cells in turbulent flow, which has been shown to cause six times more damage to red blood cells (RBC’s) than laminar flow with the same mean wall shear stress [Kameneva, et al. 2004]. Though it is a purely mathematical construct to yield closure of the time-averaged Navier-Stokes equation for a continuum fluid, which is not valid at the scale of the cell, Reynolds stress has been used as an empirical indicator for damage potential [Sallam & Hwang 1984]. Other scales, including local viscous stress [Jones 1995], flow of plasma around inertia cells [Quinlan & Dooley 2007], shear within eddies [Quinlan & Dooley 2007] and shear between rigid cells within an eddy [Antiga & Steinman 2009], have been forwarded. To provide data to validate these models, an imaging system was assembled to directly observe RBC’s in turbulent flow under a microscope.

scholarly journals Permeability Properties of Jointed Rock with Periodic Partially Filled Fractures

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Fei Ye ◽  
Jun-Chao Duan ◽  
Wen-Xi Fu ◽  
Xing-Yu Yuan
Keyword(s):  
Rock Mass ◽  
Analytic Solution ◽  
Jointed Rock ◽  
Navier Stokes ◽  
Rock Fractures ◽  
Rock Matrix ◽  
Clear Fluid ◽  
Navier Stokes Equation ◽  
Seepage Characteristics ◽  
Good Agreement

Rock fractures always influence the hydrological properties of a rock mass. To investigate the seepage characteristics of a rock mass with partly filled fractures, a mathematical model is established. In this model, the clear fluid in fractures is governed by the Navier-Stokes equation, and the fluid both in the porous medium and rock matrix are subjected to the Brinkman-Extended Darcy equation. The analytic solution of an equivalent permeability coefficient for a rock mass with partly filled fractures is solved, and it could be reduced to some special known results. Comparisons with experimental data show good agreement, thus verifying the validity of the present computations.

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