

Slug Catcher Multiphase CFD Modeling: Optimization and Comparison with Industrial Standards


Pages :
19


Authors :
Gianluca MONTENEGRO,
G. D’Errico,
A. Della Torre,
L. Cadei,
S. Masi,
In the oil & gas industry, the traditional procedure for slug catcher design is based on the Stokes' law. Design
equations are obtained from a 1D analysis and validated with experimental data. Therefore, this method
basically relies on simplified models and empirical correlations. For this reason, an over margin factor from
20 to 40% is usually applied. In this paper, a simplified CFD procedure for the modelling of the gasliquid
separation is presented. Steady state and transient models have been considered for single phase and
multiphase fluids, using OpenFOAM. The influence of flow model and mesh grid on results have been
evaluated as a tradeoff between solution accuracy and computational efforts, in order to assess the
applicability of these models to industry. A comparison of the industrial validation procedure with the CFD
analysis has been realized, focusing on the pros and cons of the two different approaches. A new application
solver has been constructed and programmed in order to get the most accurate results with the minimum
computational efforts. This solver is based on a completely new and innovative approach to the NavierStokes
equations for multiphase flow. New model proposed has been used for the evaluation of design for the two
slug catchers studied, in order to get a better separation and fluids management.





Turbulent Plane Impinging JetPhysical Insight and Turbulence Modeling


Pages :
1117


Authors :
M. Charmiyan,
Ahmadreza Azimian,
Laurent Keirsbulck,
E. Shirani,
Fethi Aloui,
A 3D numerical simulation using large eddy simulation (LES) method is performed for a submerged turbulent
water slot jet impinging normally on a flat plate with a nozzletoplate distance of 10 jet width and a
Reynolds number of 16000 and the results are compared with the existing experimental data. The numerical
platform is an open source CFD code based on the field operation and manipulation C++ class library for
continuum mechanics (OpenFOAM) and is used to simulate the flow and represent the mean and
instantaneous flow field characteristics. Also, simulations are performed with two different subgridscale
(SGS) models, oneequation based subgridscale model and localized dynamic smagorinsky model.
Evaluating the different subgridscale (SGS) models, a priori and a posteriori test is done. Comparison
between results obtained using the SGS models and experimental data shows that the simulation results using
localized dynamic Smagorinsky model are more compatible with the experimental data compared with those
that obtained from the kinetic energy oneequation model especially in regions close to the impingement wall
and in free jet region.





Turbulent Flows Structures Crossing Conical Diffusers: Angle Effect Analysis using PIV Technique and POD for PostProcessing


Pages :
1929


Authors :
E. Berrich Betouche,
Fethi Aloui,
D. Pierrat,
L. Gros,
Anthony COUZINET,
Jack Legrand,
In this work, we investigated experimentally the hydrodynamics of flows crossing conical diffusers. On our
previous work (Aloui et al., 2011), CFD turbulent models were validated for flows crossing the critical angle
(2=16°). Indeed, the PIV data base constructed was exploited to validate a variant of SSTRLC model.
Taking into account the conical diffuser angle effect, the apparition and the development of vortices were
observed and studied. The dynamics of the recirculation zones which may be observed at the lower and
higher parts of the singularity, has not formed the subject of numerous studies. There were no studies that
characterize the vortices at the conical diffusers in terms of size, centre positions, and vortex intensity.
Consequently, two conical diffusers were studied using the Particle Image Velocimetry technique (PIV). The
results illustrate effects of “opening angle” (2=16°) and (2=30°) on the flow structures developed in such
type of diffusers. From such opening angle of conical diffusers, the progressive angle increasing generates a
detachment of the boundary layer of the conical diffuser depending on the turbulence level. This detachment
may lead to a coherent flow structures. We applied the coherent structures criterion 2 to the recorded
velocity fields to detect and characterize the vortices at the conical diffusers. We used the Proper Orthogonal
Decomposition (POD) to filter the PIV data base constructed and to extract the most energetic modes. The
results illustrate that the turbulent flow structures can be constituted using a limited number of energetic
modes.





AeroThermal Optimization of a Heat Sink using Variable Neighbourhood Search


Pages :
3137


Authors :
PierreOlivier Jandaud,
L. Lambourg,
S. Harmand,
This paper presents a geometrical optimization of a heat sink modelled using threedimensional CFD. The
heat sink studied is circular with radial inlets and parallel fins. The parameters of the optimization are the
different spacings between the fins. The optimization process is multiobjective and uses an aggregated
objective function of both the thermal resistance and the pressure drop of the system. To perform the
optimization, a relatively new technique has been used called Variable Neighbourhood Search (VNS). The
optimization results give several interesting new geometries. In addition, the performances of VNS are
measured with two criteria: the speed of convergence and the repeatability between two optimization runs.
These performances are good compared to more traditional optimization techniques like Genetic Algorithms.





Liquid Film Thickness: Study and Influence over Aqueous Foam Flow


Pages :
3948


Authors :
Rogelio Chovet,
Fethi Aloui,
Nowdays, we face important energy challenges. These ones are making scientist all over the world reconsider
the way they look into problem and find innovative solutions to improve industrial processes efficiency. One
of many original ideas is the use of “notregular” fluids over regular applications. Aqueous Foam Flow
present several unusual rheological properties when put inside a horizontal channel: low density,
viscoelastoplastic behaviour, and high wall shear stress. These ones give this type of fluid interesting
capacities and uses: Assisted oil extraction, heat exchange, lubrication. In this study we undertake the causes
of these interesting properties, which are directly related to the liquid sliplayer located between the flowing
bubbles and the walls. For different velocities (2 cm/s, 4 cm/s and 6 cm/s) and void fractions (from 55% to
85%) we will study the influence of the liquid film thickness over the wall shear stress, using innovative
measurement techniques: conductimetry and polarographic methods. An interesting relationship is seen
between the limit diffusion current, required to accurately utilize the polarographic method, the wall shear
stress and the liquid film thickness. The bubbles passage over the walls generates an oscillation of the
sliplayer thickness which directly affects the polarographic results. However, as we increase the foams
velocity this influence diminish and the wall shear stress calculations are more accurate.





Numerical and Experimental Study on the Effects of Taylor Number on the Wavelength of the CouetteTaylor Flow


Pages :
4957


Authors :
mostafa monfared,
E. Shirani,
Fethi Aloui,
M. R. Salimpour,
In the present study, the hydrodynamic behaviours of the Couette Taylor flow in different flow regimes were
investigated, experimentally and numerically.In this research, the effects of Taylor number on wavelength of
the flow, which are two important hydrodynamic charactristics of the Couette Taylor flow, are investigated
both experimentally and numerically in order to study the stability of the flow and formation of vortices. In
addition, the velocity and pressure variation of the the flow between two cylinders were considered and
compared for different Taylor numbers to understand the behaviuor of the flow.





Use of the PIV and Electrochemical Techniques to Experimentally Characterize the CouetteTaylorPoiseuille Flow Instabilities


Pages :
5968


Authors :
Wafik ABASSI,
Fethi Aloui,
S.B Nasrallah,
Jack Legrand,
The TaylorCouette problem is a fundamental model in bifurcation theory and hydrodynamic stability. The
inner cylinder rotation generates a flow pattern known by a transition to turbulence through a sequence of
successive hydrodynamic instabilities. The effect of an imposed axial flow on the instabilities evolution is
studied. An experimental device was designed to study this effect. It consists of two concentric cylinders with
the inner one rotating and the outer one fixed, and a pressure driven axial flow can be superimposed in the
annulus. In addition, various motion of the inner cylinder can also be imposed (oscillation, gradual or abrupt
disturbance).The objectives are to investigate the effect of the superposition of an axial flow on the stability
of the flow and its influence on the vortex behavior and hence on the wall shear stress. The resulting structure
of the flow then depends on the initial flow regime, due to the rotation of the inner cylinder and the velocity
of the axial flow. Consequently, two dimensionless parameters are defined to characterize the flows: the
Taylor number and the Reynolds number of the axial flow. Experimental PIV measurements are devoted to
characterize the TaylorCouette flow dynamics with imposed axial flow and then synchronized with
electrochemical measurements to study the vortexwall interaction.





Scavenging Process Analysis in a 2Stroke Engine by CFD Approach for a Parametric 0D Model Development


Pages :
6980


Authors :
S. Cagin,
N. Bourabaa,
E. Delacourt,
Céline Morin,
X. Fischer,
D. Coutellier,
B. Carré,
S. Loumé,
This paper presents a method to improve cylinder design of 2stroke autoignition engine based on a CFD
(Computational Fluid Dynamics) study of internal flows in the chamber and an unsteady global 0D
parametric approach. In 2stroke engine, scavenging process plays an important role regarding engine
efficiency and pollutant emissions. Several geometrical and environmental parameters (like piston velocity
and inlet/outlet thermofluid conditions) impact the scavenging process and most of them vary when the
engine is running. To improve the scavenging process, an analytical model (integrating design parameter
variations) is developed and will be implemented in 0D global model. CFD simulations are used to establish
the analytical scavenging model. The CFD model includes species transportation, piston motion (remeshing),
turbulent effectsbut it does not take into account the combustion process or the aerodynamics in the cylinder
before the beginning of scavenging. After defining the influent parameters on the scavenging, multiple
simulations with varying values of parameters were run and a data base was created. The data base will be
used to develop a reduced model of the scavenging process which will be integrated in a global 0D model of
the engine. Through a reference case, the incylinder flow is analyzed and the evolution of velocity, pressure,
species and turbulent kinetic energy fields during scavenging are discussed. After a statistical treatment, the
results of simulations highlight two main significant parameters: the advance of intake opening and the angle
of the intake duct. The decoupling of these two parameters is particularly suitable for the optimization of
engines.





On the Influence of Lowpower Laser Source on the Evaporation of Single Droplets: Experimental and Numerical Approaches


Pages :
8187


Authors :
MH Sadafi,
S. González Ruiz,
M. R. Vetrano,
J. van Beeck,
I. Jahn,
J.M. Buchlin,
K. Hooman,
This work investigates the influence of laser power on an evaporating single droplet made from an H2O and
NaCl mixture. Heat and mass transfer of a single droplet with the presence of a lowpower laser source (as
HeNe laser) is studied both numerically and experimentally in this article. A new model is presented to
simulate water droplet evaporation. The model is robust enough to be applied for various initial
concentrations and conditions of the droplet, ambient conditions, and dissolved media properties. Moreover,
laser energy is taken into consideration as a source term which is a function of the wave length of the source
beam and refractive index of the droplet. Considering the involved parameters, the model is implemented in a
MATLAB code and validated using experimental data obtained in this study on top of those already available
in the literature. Experimental data were collected for droplets with an initial radius of 500μm at room
temperature for three initial concentrations of 3%, 5%, and 10% (by mass) of NaCl in water as well as pure
water droplet to provide a comprehensive validation dataset. It is shown that lowpower laser source
significantly increases the evaporation rate (2.7 to 5.64 for 0% and 10% initial concentration of salt,
respectively) which must be taken into consideration while using laser based measurement techniques.





Reconstruction of Incylinder Temperature, Equivalence Ratio and NOx Distribution Fields using Proper Orthogonal Decomposition Technique


Pages :
8995


Authors :
H. Akbari,
A. SalavatiZadeh,
A. Javaheri,
Vahid Esfahanian,
S. V. Ghavami,
H. Ghomashi,
The present study aims to reduce the computational cost of incylinder phenomena simulation under the light
of employing Proper Orthogonal Decomposition (POD) technique. The equivalence ratio as the main
identifier for soot formation tendency along with temperature and nitrogen oxide fields, are studied inside a
gasfuelled engine. The required correlation matrix is built based on ten snapshots obtained from the results
of engine threedimensional simulation, which are verified based on experimental data. The AVLFIRE
v.2013 software is used to carry out the three dimensional simulations. The flow field at 3250 rpm is then
estimated by POD coefficients and subsequent curve fittings. To validate the reduced order results, this
condition is simulated by the software. For instance, temperature and equivalence ratio fields at top dead
center and 5 degree after top dead center are compared. The relevance index for equivalence ratio indicates
about 96% consistency between reduced order and 3D simulation results. On the other hand, this index is
found to be about 99% at both crank angels for temperature, which proves a more coherent structure in the
temperature field than that of equivalence ratio. Meanwhile, the analysis of 3D simulation results by POD
demonstrates a more coherent structure for the incylinder flow regime at top dead center. This consistency is
obtained in spite of computation time of POD being approximately 1% of 3D simulation time.





Numerical and Experimental Investigation into the Jet and Dispersion of CO R2 R from Pressurized Transportation Pipelines


Pages :
97106


Authors :
Chuanlong Xu,
X. Zhang,
Z. Ding,
S. Wang,
In carbon capture and storage system, the captured COR2 from energy production processes is compressed to high pressures, transported to a storage site, and then injected into a suitable geologic formation. The leakages from high pressure transportation pipelines would pose hazard to the environment and people. In this paper, a laboratory scale rig for simulating COR2 pipeline leakage is built, and a twodimensional model is further developed to study the complex behavior of the jet and dispersion of COR2 from the rig at continuous leakage flowrate. In view of the phasechange heat transfer of COR2, a multiphase flow model is used to simulate the jet and dispersion of COR2 gasliquid twophase flow. The Euler/Lagrange model and particle stochastic trajectory model are applied to describing the development process of the jet and dispersion of COR2. The computational fluid dynamics software Fluent is employed to calculate the flow field. To prove the validity of the numerical models, an infrared thermography is used to record the temperature field near the leakage orifice during experiments.





Aerodynamic Investigation of a Wind Turbine using CFD and Modified BEM Methods


Pages :
107111


Authors :
M. Tahani,
M. Moradi,
In this study aerodynamics analysis of full scaled Vestas V47 wind turbine is carried out by the use of modified blade element momentum (BEM) theory and computational fluid dynamics (CFD). In order to determine accurate results BEM theory is programmed by considering drag coefficient, Glauert correction and Prandtle tip loss factor. CFD simulation is determined employing kw sst turbulence model and periodic boundary condition. The investigation outcomes are compared with each other. To validate CFD and BEM results, the only available data is real field measurement that is done by Vestas Company and power is compared with these data. Finally, according to the accuracy of results and computational cost, it is obtained that BEM is more applicable in engineering estimations.





Experimental Study of Heat and Mass Transfer for Liquid Film Evaporation along a Vertical Plate Covered With a Porous Layer


Pages :
113120


Authors :
Amine TERZI,
Sadok Ben Jabrallah,
S. Harmand,
In this paper, we realized an Experimental study of heat and mass transfer for liquid evaporation along a vertical plate covered with a porous layer. To develop this study, an experimental dispositive was realized. To highlight the effect of the addition of a porous layer on the phenomenon of evaporation, we first study the case of the flow of a liquid film on an aluminium plate. Then we covered the same plate by a porous layer. We could measure the temperature along the plate and the evaporated flow using the test bed. From these measurements we note that temperatures are higher with the presence of the porous medium which affect positively on the evaporated flow. In addition, various dimensionless numbers were analyzed as the sensible and latent local Nusselt number, solving the energy equation by inverse method. We note that the latent Nusselt number is more important than the sensible Nusselt Number. Then the flow dissipated by evaporation is greater than that used by the film to increase its temperature. We also note that the calculated values of the latent and sensible Nusselt number are greater in the presence of the porous medium that proves that the addition of the porous layer improves heat and mass exchange.





Experimental and Numerical Investigations of the Characterisation of Reflected Overpressures around a Complex Structure


Pages :
121129


Authors :
Ludovic BLANC,
JeanLuc Hanus,
Mame WilliamLouis,
Benjamin LEROUX,
In explosionstructure interaction problems, an accurate prediction of blast loading remains a hard challenge. The reflected overpressures around a complex structure, such as a building with an apse and an atrium are almost always unpredictable so that experiments and numerical simulations may be the only possibilities to evaluate the threat of an industrial explosion. Well instrumented blast experimental studies are first carried out at small scale on a rigid specimen with a variable incidence angle. The main objective is to observe and quantify the regular and irregular reflections and the diffractions of a blast wave on a real structure. In parallel, numerical simulations are performed with a homemade eulerian CFD code. The comparison with experimental results permits to discuss the capabilities and limitations of numerical blast predictions.





Experimental Investigations of the Spherical TaylorCouette Flow


Pages :
131137


Authors :
Mohamed MAHLOUL,
A. Mahamdia,
M. Kristiawan,
Transition to turbulence of a viscous incompressible fluid flow between two concentric spheres with the inner one rotating and the outer stationary was investigated experimentally. The flow modes were studied using the flow visualization and electrochemical technique. Different flow states were obtained for the gap/radius ratio 0.107 in function of the Taylor number in the interval (22  1500) and aspect ratio (17  21). Observed states were classified into: Taylor Vortex Flow (TVF), Spiral Mode (SM), Spiral Mode Wavy Mode (SM+WM), Spiral Wavy Mode (SWM), Wavy Mode (WM) and Chaos. The variations of the flow patterns were reflected by the wall velocity gradient, its fluctuation and spectral analysis. Fast Fourier transform applied on the time series of the wall velocity gradient allowed for the analysis and identification of the fundamental frequencies and their evolutions associated with each flow state.





Forced Convection in a Cylinder Filled with Porous Medium, including Viscous Dissipation Effects


Pages :
139145


Authors :
Boutheina ZALLAMA,
L. Zili Ghedira,
S.B Nasrallah,
In this work, a numerical study of forced convection of an incompressible fluid through a cylinder filled with a porous medium is carried out by taking into account the heat due to viscous dissipation. Dimensionless equations of the problem are solved numerically. The energy transport bidimensional model is based on the local nonthermal equilibrium assumption with consideration of viscous dissipation effects. The influence of various parameters like Darcy number, Reynolds number, Forchhheimer coefficient and Eckert number on temperature fields is investigated and examined throughout this paper. It is found that all these parameters have significant influence on thermal performance of the packed bed within certain conditions.





Experimental Investigations on Oscillatory CouetteTaylor Flow Wall Shear Stress Behavior using Electrochemical Technique: Low Modulation Effect


Pages :
147154


Authors :
E. Berrich Betouche,
Fethi Aloui,
Jack Legrand,
In the simplest and original case of study of the Taylor–Couette TC problems, the ﬂuid is contained between a ﬁxed outer cylinder and a concentric inner cylinder which rotates at constant angular velocity. Much of the works done has been concerned on steady rotating cylinder(s) i.e. rotating cylinders with constant velocity and the various transitions that take place as the cylinder(s) velocity (ies) is (are) steadily increased. On this work, we concentrated our attention in the case in which the inner cylinder velocity is not constant, but oscillates harmonically (in time) clockwise and counterclockwise while the outer cylinder is maintained fixed. Our aim is to attempt to answer the question if the modulation makes the flow more or less stable with respect to the vortices apparition than in the steady case and if there are any reversing or non reversing flows apparition. If the modulation amplitude is large enough to destabilize the circular Couette ﬂow, two classes of axisymmetric Taylor vortex ﬂow are possible: reversing Taylor Vortex Flow (RTVF) and NonReversing Taylor Vortex Flow (NRTVF). Our work presents an experimental investigation of the effect of oscillatory CouetteTaylor flow on the instantaneous and local mass transfer and wall shear rates evolutions, i.e. the impact of vortices at wall; and the detection of any RTVF and/or NRTVF apparition. The vortices may manifest themselves by the presence of timeoscillations of mass transfer and wall shear rates; this generally corresponds to an instability apparition even for steady rotating cylinder. On laminar CT flow, the timeevolution of wall shear rate is linear. It can be presented as a linear function of the angular velocity. For a mean Taylor number corresponding to a laminar Couette flow, a modulation frequency F = 0.1 Hz and an amplitude respectively β = 0.53 andβ = 1.08 are sufficient to destabilize the laminar CT flow, Taylor vortices appear. Comparing to a steady rotational velocity case, oscillatory flow accelerates the instability apparition, i.e. the mean critical Taylor number corresponds to the transition is smaller than that of the steady rotational case. The vortices direction can be deduced from the sign of the instantaneous wall shear rate time evolution.





Effect of Dispersed Nanoparticles on Thermophysical Properties of Nanofluid and Heat Transfer Coefficients


Pages :
165171


Authors :
H. Afshar,
M Shams,
Mojtaba Moosavi naeinian,
Goodarz Ahmadi,
In this investigation, effects of dispersed Cu nanoparticles in water on heat transfer coefficients are studied using EulerianLagranigian approach. Nanoparticles disperse in the fluid due to drag, weight and Brownian forces acting on them. A new particle search algorithm is used to trace the particles in every time step. Thermal coupling between dispersed and carrier phases is done and also thermal and momentum interaction between particles and solid walls are taken onto account to obtain velocity and temperature fields. The specific heat of nanofluid is obtained using conventional models. The results show that regarding thermophysical properties of particles and base fluid, and also other conditions like mass flow rate and particle size, degradation or intensification of heat transfer coefficients can occur.





Numerical Investigation of NonNewtonian Blood Effect on Acoustic Streaming


Pages :
173176


Authors :
R. Aayani,
Azadeh Shahidian,
M. Ghassemi,
Acoustic streaming, as an important phenomenon, is used in a wide variety of applications such as drug delivery and the removal of plaque in the vein surfaces. The purpose of the current paper is to investigate the effect of blood, as a nonNewtonian fluid, on acoustic streaming. The governing nonlinear differential equations, mass, momentum, and state equations for nonstationary fluid using secondorder perturbation theory, are coupled and solved. An in house computational fluid dynamics (CFD) code based on the finite element method is utilized. Results show that viscosity is highly dependent on shear stresses, about 60%. In addition viscosity affects the acoustic streaming velocity field.





