scholarly journals Comparison of Computational Fluid Dynamics Simulations and Experiments for Stratified Air-Water Flows in Pipes

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Gabriele Chinello ◽  
Anis Awal Ayati ◽  
Don McGlinchey ◽  
Gijsbert Ooms ◽  
Ruud Henkes
Keyword(s):  
Turbulence Model ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Experimental Results ◽  
Navier Stokes ◽  
Current Form ◽  
Interface Waves ◽  
Sst Turbulence Model ◽  
Gas Liquid Flow ◽  
Dynamics Simulations

Stratified gas–liquid flow is a flow regime typically encountered in multiphase pipelines. The understanding and modeling of this regime is of engineering importance especially for the oil and gas industry. In this work, simulations have been conducted for stratified air–water flow in pipes. We solved the Reynolds-averaged Navier–Stokes (RANS) equations with the volume of fluid (VOF) method. The aim of this work was to evaluate the performance of the k–ω shear stress transport (SST) turbulence model with and without damping of the turbulence at the gas–liquid interface. Simulation results were compared with some of the latest experimental results found in the literature. A comparison between the simulated velocity and kinetic energy profiles and the experimental results obtained with the particle image velocimetry (PIV) technique was conducted. The characteristics of the interfacial waves were also extracted and compared with the experiments. It is shown that a proper damping of the turbulence close to the interface is needed to obtain agreement with the experimental pressure drop and liquid hold-up. In its current form, however, RANS with the k–ω turbulence model is still not able to give an accurate prediction of the velocity profiles and of the interface waves.

scholarly journals Development of a Numerical Investigation Framework for Ground Vehicle Platooning

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 404
Author(s):  
Charles Patrick Bounds ◽  
Sudhan Rajasekar ◽  
Mesbah Uddin
Keyword(s):  
Turbulence Model ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Ground Vehicle ◽  
Simulation Methodology ◽  
Vehicle Platooning ◽  
Length Separation ◽  
Dynamics Simulations ◽  
The Impact ◽  
Far Wake

This paper presents a study on the flow dynamics involving vehicle interactions. In order to do so, this study first explores aerodynamic prediction capabilities of popular turbulence models used in computational fluid dynamics simulations involving tandem objects and thus, ultimately presents a framework for CFD simulations of ground vehicle platooning using a realistic vehicle model, DrivAer. Considering the availability of experimental data, the simulation methodology is first developed using a tandem arrangement of surface-mounted cubes which requires an understanding on the role of turbulence models and the impacts of the associated turbulence model closure coefficients on the prediction veracity. It was observed that the prediction accuracy of the SST k−ω turbulence model can be significantly improved through the use of a combination of modified values for the closure coefficients. Additionally, the initial validation studies reveal the inability of the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach to resolve the far wake, and its frailty in simulating tandem body interactions. The Improved Delayed Detached Eddy Simulations (IDDES) approach can resolve the wakes with a reasonable accuracy. The validated simulation methodology is then applied to the fastback DrivAer model at different longitudinal spacing. The results show that, as the longitudinal spacing is reduced, the trailing car’s drag is increased while the leading car’s drag is decreased which supports prior explanations of vortex impingement as the reason for drag changes. Additionally, unlike the case of platooning involving Ahmed bodies, the trailing model drag does not return to an isolated state value at a two car-length separation. However, the impact of the resolution of the far wake of a detailed DrivAer model, and its implication on the CFD characterization of vehicle interaction aerodynamics need further investigations.

scholarly journals Hydrodynamic Study of Oil Leakage in Pipeline via CFD

2014 ◽  
Vol 6 ◽  
pp. 170178 ◽  
Author(s):  
Morgana de Vasconcellos Araújo ◽  
Severino Rodrigues de Farias Neto ◽  
Antonio Gilson Barbosa de Lima ◽  
Flávia Daylane Tavares de Luna
Keyword(s):  
Oil And Gas ◽  
Three Dimensional ◽  
Oil And Gas Industry ◽  
Transient Pressure ◽  
Pipe Length ◽  
Gas Industry ◽  
Efficient Detection ◽  
Ansys Cfx ◽  
Oil Flow ◽  
Dynamics Simulations

This paper describes the transient dynamics behavior of oil flow in a pipe with the presence of one or two leaks through fluid dynamics simulations using the Ansys CFX commercial software. The pipe section is three-dimensional with a pipe length of 10 m, a pipe diameter of 20 cm, and leak diameter of 1.6 mm. The interest of this work is to evaluate the influence of the flow velocity, and the number and position of leaks on the transient pressure behavior. These new data may provide support for more efficient detection systems. Thus, this work intends to contribute to the development of tools of operations in oil and gas industry.

scholarly journals Prediction of the Propeller Performance at Different Reynolds Number Regimes with RANS

2021 ◽  
Vol 9 (10) ◽  
pp. 1115
Author(s):  
João Baltazar ◽  
Douwe Rijpkema ◽  
José Falcão de Campos
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Scale Effects ◽  
Open Water ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Transition Model ◽  
Sst Turbulence Model ◽  
Propeller Performance ◽  
Selection Of

In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 104 to 107. The k−ω SST turbulence model and the γ−R˜eθt correlation-based transition model are utilised and results compared for a conventional marine propeller. First, the selection of the turbulence inlet quantities for different flow regimes is discussed. Then, an analysis of the iterative and discretisation errors is made. This work is followed by an investigation of the predicted propeller flow at variable Reynolds numbers. Finally, the propeller scale-effects and the influence of the turbulence and transition models on the performance prediction are discussed. The variation of the flow regime showed an increase in thrust and decrease in torque for increasing Reynolds number. From the comparison between the turbulence model and the transition model, different flow solutions are obtained for the Reynolds numbers between 105 and 106, affecting the scale-effects prediction.

Study of the Dynamic and Thermal Behaviors of an Air Flow in a T-Bifurcation

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Ali Riahi ◽  
Julien Pelle ◽  
Lilia Chouchene ◽  
Souad Harmand ◽  
Sadok Ben Jabrallah
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Research Work ◽  
Internal Surface ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Flow Ratio ◽  
Sst Turbulence Model ◽  
Dynamics Simulations

This paper presents a numerical and experimental study of a turbulent flow of air in a T-bifurcation. This configuration corresponds to a stator containing radial vents oriented vertically to the rotor–stator air gap in electrical machines. Our analysis focuses on the local convective heat transfer over the internal surface of the vents under a turbulent mass flow rate. To model the cooling installation in this region, computational fluid dynamics simulations and an experiment using particle image velocimetry (PIV) are performed. The resulting flow generally produces recirculation zones in various channels. The effect of the flow ratio and diameter of the bifurcation on the dynamic and thermal behavior of the flow is also examined. In this study, we apply a numerical approach based on the k–ω shear stress transport (SST) turbulence model (using the commercial software, “comsolmultiphysics”) to numerically solve the Navier–Stokes equations and energy equation of the system under consideration. We describe the different hypotheses necessary to formulate the equations governing the problem, initial conditions, and boundary condition. The velocity in the bifurcation calculated using the simulation is compared with that obtained by the experiment and it reveals a good agreement. The effect of the branch diameter of the bifurcation and flow ratio on the heat transfer is specifically analyzed in this research work.

Development of a Numerical Based Correlation for Performance Losses due to Surface Roughness in Axial Turbines

2014 ◽  
Vol 30 (6) ◽  
pp. 631-642 ◽  
Author(s):  
S. A. Moshizi ◽  
M. H. Nakhaei ◽  
M. J. Kermani ◽  
A. Madadi
Keyword(s):  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Streamline Curvature ◽  
Sst Turbulence Model ◽  
Stator Blade ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Axial Turbines

AbstractIn the present work, a recently developed in-house 2D CFD code is used to study the effect of gas turbine stator blade roughness on various performance parameters of a two-dimensional blade cascade. The 2D CFD model is based on a high resolution flux difference splitting scheme of Roe (1981). The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the zero-equation turbulence model of Baldwin-Lomax (1978) and two-equation Shear Stress Transport (SST) turbulence model. For the smooth blade, results are compared with experimental data to validate the model. Finally, a correlation between roughness Reynolds number and loss coefficient for both turbulence models is presented and tested for three other roughness heights. The results of 2D turbine blade cascades can be used for one-dimensional models such as mean line analysis or quasi-three-dimensional models e.g. streamline curvature method.

Heat Transfer in Reacting Cooling Films: Influence and Validation of Combustion Modeling in Numerical Simulations

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Stephanie Pohl ◽  
Gabriele Frank ◽  
Michael Pfitzner
Keyword(s):  
Turbulence Model ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Reacting Flows ◽  
Experimental Results ◽  
Navier Stokes ◽  
Combustion Model ◽  
Ansys Fluent ◽  
Combustion Modeling ◽  
Compact Design

The demand for increased performance and lower weight of gas turbines gives rise to higher fuel-to-air ratios and a more compact design of the combustion chamber, thereby increasing the potential of fuel escaping unburnt from the combustor. Chemical reactions are likely to occur when the coolant air, used to protect the turbine blades, interacts with the unreacted fuel. Within this work, Reynolds-averaged Navier–Stokes (RANS) simulations of reacting cooling films exposed to high temperature fuel-rich exhaust gases are performed using the commercial computational fluid dynamics (CFD) code ansys fluent and validated against experimental results obtained at the Air Force Research Laboratory in Ohio. The results underline that the choice of the turbulence model has a significant impact on the evolution of the flow field and the mixing effectiveness. The flamelet as well as the equilibrium combustion model is able to predict an adequate distance of the reaction zone normal to the wall. Its thickness, however, is still much smaller and its onset too far upstream as compared to the experimental results. According to the present analysis, the flamelet combustion model applied along with k–ω shear stress transport (SST) or k–ε turbulence model turned out to be an appropriate choice in order to model near wall reacting flows with reasonable prospect of success.

RANS Modelling of Wake Induced Transition With the Dynamic Intermittency Concept

2006 ◽  
Author(s):  
Koen Lodefier ◽  
Erik Dick
Keyword(s):  
Turbulence Model ◽  
Free Stream ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Suction Side ◽  
Navier Stokes ◽  
Transition Model ◽  
Navier Stokes Equations ◽  
Free Stream Turbulence ◽  
Sst Turbulence Model

A transition model for describing wake-induced transition is presented based on the SST turbulence model by Menter and two dynamic equations for intermittency: one for near-wall intermittency and one for free-stream intermittency. In the Navier-Stokes equations, the total intermittency factor, which is the sum of the two, multiplies the turbulent viscosity computed by the turbulence model. The quality of the transition model is illustrated on the T106A test cascade for different levels of inlet free-stream turbulence intensity. The unsteady results are presented in space-time diagrams of shape factor, wall shear stress, momentum thickness and intermittency on the suction side. Results show the capability of the model to capture the physics of unsteady transition. Inevitable shortcomings are also revealed.

Inertial impedance of coalescence during collision of liquid drops

2019 ◽  
Vol 876 ◽  
pp. 449-480 ◽  
Author(s):  
Krishnaraj Sambath ◽  
Vishrut Garg ◽  
Sumeet S. Thete ◽  
Hariprasad J. Subramani ◽  
Osman A. Basaran
Keyword(s):  
Free Boundary ◽  
Boundary Problem ◽  
Free Boundary Problem ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Industrial Applications ◽  
Navier Stokes ◽  
Gas Industry ◽  
Liquid Drops ◽  
Drainage Time

The fluid dynamics of the collision and coalescence of liquid drops has intrigued scientists and engineers for more than a century owing to its ubiquitousness in nature, e.g. raindrop coalescence, and industrial applications, e.g. breaking of emulsions in the oil and gas industry. The complexity of the underlying dynamics, which includes occurrence of hydrodynamic singularities, has required study of the problem at different scales – macroscopic, mesoscopic and molecular – using stochastic and deterministic methods. In this work, a multi-scale, deterministic method is adopted to simulate the approach, collision, and eventual coalescence of two drops where the drops as well as the ambient fluid are incompressible, Newtonian fluids. The free boundary problem governing the dynamics consists of the Navier–Stokes system and associated initial and boundary conditions that have been augmented to account for the effects of disjoining pressure as the separation between the drops becomes of the order of a few hundred nanometres. This free boundary problem is solved by a Galerkin finite element-based algorithm. The interplay of inertial, viscous, capillary and van der Waals forces on the coalescence dynamics is investigated. It is shown that, in certain situations, because of inertia two drops that are driven together can first bounce before ultimately coalescing. This bounce delays coalescence and can result in the computed value of the film drainage time departing significantly from that predicted from existing scaling theories.

Time-Domain Simulation of Riser VIV in Sheared Current

2007 ◽  
Author(s):  
Kevin Huang ◽  
Hamn-Ching Chen ◽  
Chia-Rong Chen
Keyword(s):  
Time Domain ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Critical Parameters ◽  
Navier Stokes ◽  
Outer Diameter ◽  
Gas Industry ◽  
Decomposition Approach ◽  
Tension Distribution ◽  
Uniform Current

Riser vortex-induced vibrations (VIV) have attracted significant attentions in recent years in offshore oil and gas industry. There is an increasing interest in using computational fluid dynamics (CFD) approach for deepwater riser VIV time-domain simulations. Our previous study has demonstrated that the long riser (L/D = 1400) VIV response in uniform current can be predicted with reasonable accuracy by time domain simulations with Chimera over-set data grid technique. This paper is to further that study and investigate the riser VIV in sheared current profiles. The riser studied in this paper is a long marine riser with constant tension distribution. Its prototype has an outer diameter (OD) of 0.027m and a mass ratio of 1.6. The fluid domain is discretised using approximately one million elements. A linearly sheared current is imposed in perpendicular to the riser, and the flow field is calculated using an unsteady Reynolds-Averaged Navier-Stokes (RANS) numerical method in conjunction with a Chimera domain decomposition approach with overset grids. The critical parameters including riser VIV root-mean-square (rms) a/D, vorticity, drag and lift coefficients are processed, and compared to those of uniform current and experimental data. The simulation results show that the riser VIV under sheared current behaves differently from uniform current. It is also shown that the presented CFD approach provides reasonable results and is suitable for long riser VIV evaluation in deepwater and complex current conditions.

Turbulence Modeling of Forced Convection Heat Transfer in Two-Dimensional Ribbed Channels

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
E. Elsaadawy ◽  
H. Mortazavi ◽  
M. S. Hamed
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Turbulence Model ◽  
Turbulence Modeling ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Experimental Results ◽  
Electronic Systems ◽  
Sst Turbulence Model ◽  
Stress Models

Although the problem of 2D ribbed channels has been studied heavily in the literature as a benchmark or basic case for cooling of electronic packing, there is still a contradiction in the literature about the suitable turbulence model that should be used in such a problem. The accuracy of the computational predictions of heat transfer rates depends mostly on the choice of the proper turbulence model that is capable of capturing the physics of the problem, and on the corresponding wall treatment. The main objective of this work is to identify the proper turbulence model to be used in thermal analysis of electronic systems. A number of available turbulence models, namely, the standard k-ε, the renormalization group k-ε, the shear stress transport (SST), the k-ω, and the Reynolds stress models, have been investigated. The selection of the most appropriate turbulence model has been based upon comparisons with both direct numerical simulations (DNSs) and experimental results of other works. Based on such comparisons, the SST turbulence model has been found to produce results in very good agreement with the DNS and experimental results and hence it is recommended as an appropriate turbulence model for thermal analysis of electronic packaging.

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