Numerical Investigation of Turbulent Models in the Development and Establishment of Turbulent Flows With Flow Conditioners

2010 ◽  
Author(s):  
Boualem Laribi ◽  
Pierre Wauters ◽  
Abdelkader Youcefi
Keyword(s):  
Numerical Investigation ◽  
Turbulent Flows ◽  
Turbulence Models ◽  
Equation System ◽  
International Standards ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Flow Meters ◽  
Numerical Experimentation ◽  
Turbulent Models

The accuracy in measuring flow of fluids such as gas and oil has a great importance for the Algerian economy. The flows of fluids in non-standard conditions, presence of disturbances, in which there are flow meters in pipes, make a very important error. International standards ISO 5167 and AGA3 stipulate that the meter is installed in a fully developed flow. This article describes a numerical investigation of development and establishment of flows in the presence of a double bend 90° in perpendicular planes as a perturbation. The software used was code Fluent where different turbulence models are tested to better simulate and view the effectiveness of models in the description of the flow of fluid compared to flow behaviour cited in the standards and the experimental results. The numerical experimentation is done with air in a pipe of 100mm diameter at a Reynolds number 105. The numerical analysis is based on solving Navier-Stokes equation system with several turbulent models, k-ε, k-ω, RSM and its variants.

scholarly journals GLOBAL EXISTENCE RESULTS FOR THE ANISOTROPIC BOUSSINESQ SYSTEM IN DIMENSION TWO

2011 ◽  
Vol 21 (03) ◽  
pp. 421-457 ◽  
Author(s):  
RAPHAËL DANCHIN ◽  
MARIUS PAICU
Keyword(s):  
Global Existence ◽  
Turbulent Flows ◽  
Vertical Direction ◽  
Boussinesq System ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Incompressible Euler Equation ◽  
Navier Stokes Equation ◽  
Transport Diffusion ◽  
Anisotropic Viscosity

Models with a vanishing anisotropic viscosity in the vertical direction are of relevance for the study of turbulent flows in geophysics. This motivates us to study the two-dimensional Boussinesq system with horizontal viscosity in only one equation. In this paper, we focus on the global existence issue for possibly large initial data. We first examine the case where the Navier–Stokes equation with no vertical viscosity is coupled with a transport equation. Second, we consider a coupling between the classical two-dimensional incompressible Euler equation and a transport–diffusion equation with diffusion in the horizontal direction only. For both systems, we construct global weak solutions à la Leray and strong unique solutions for more regular data. Our results rest on the fact that the diffusion acts perpendicularly to the buoyancy force.

Computational Investigation of Different Turbulent Models When Predicting Airflow in an Enclosure

2008 ◽  
Author(s):  
Xi Wang ◽  
Hassan Naji ◽  
Ahmed Mezrhab
Keyword(s):  
Numerical Investigation ◽  
Turbulence Models ◽  
Turbulent Stress ◽  
Computational Investigation ◽  
Isothermal Case ◽  
The Mean ◽  
Turbulent Models ◽  
Rsm Model ◽  
Cold Case ◽  
Good Agreement

In the present study, a numerical investigation is carried out for an isothermal case, a hot case and a cold case with FLUENT code. Three turbulence models are considered: the k-ε realisable model, the RNG k-ε model and the RSM linear model. The obtained results are compared to experiments and show generally a good agreement for the mean velocities and temperatures, but less satisfactory for the turbulent stress. The performance of the RSM model is remarkable. Even if none of the models is able to give the exact experimental pattern on the map of turbulence, the RSM model seems able to predict such configuration.

scholarly journals Turbulence through the Spyglass of Bilocal Kinetics

Entropy ◽  
2018 ◽  
Vol 20 (7) ◽  
pp. 539 ◽  
Author(s):  
Gregor Chliamovitch ◽  
Yann Thorimbert
Keyword(s):  
Turbulent Flows ◽  
Kinetic Scheme ◽  
Navier Stokes ◽  
Pressure Tensor ◽  
Kinetic Description ◽  
Balance Equations ◽  
Coupling Term ◽  
Navier Stokes Equation ◽  
Local Character ◽  
Non Local

In two recent papers we introduced a generalization of Boltzmann’s assumption of molecular chaos based on a criterion of maximum entropy, which allowed setting up a bilocal version of Boltzmann’s kinetic equation. The present paper aims to investigate how the essentially non-local character of turbulent flows can be addressed through this bilocal kinetic description, instead of the more standard approach through the local Euler/Navier–Stokes equation. Balance equations appropriate to this kinetic scheme are derived and closed so as to provide bilocal hydrodynamical equations at the non-viscous order. These equations essentially consist of two copies of the usual local equations, but coupled through a bilocal pressure tensor. Interestingly, our formalism automatically produces a closed transport equation for this coupling term.

Numerical Simulation of Turbulent Flows in Ribbed Pipes

2005 ◽  
Author(s):  
Sowjanya Vijiapurapu ◽  
Jie Cui
Keyword(s):  
Turbulent Flows ◽  
Turbulence Models ◽  
Numerical Data ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Friction Resistance ◽  
Circular Pipes ◽  
Computational Fluid Dynamics Cfd ◽  
Stress Models ◽  
Type Intermediate

The Reynolds averaged Navier-Stokes (RANS) equations were solved along with three turbulence models, namely κ-ε, κ-ω, and Reynolds stress models (RSM), to study the fully developed turbulent flows in circular pipes roughened by repeated square ribs. The spacing between the ribs was varied to form three representative types of surface roughness; d–type, intermediate, and k–type. Solutions of these flows at two Reynolds numbers were obtained using the commercial computational fluid dynamics (CFD) software Fluent. The numerical results were validated against experimental measurements and other numerical data published in literature. Extensive investigation of effects of rib spacing and Reynolds number on the pressure and friction resistance, flow and turbulence distribution was presented. The performance of three turbulence models was also compared and discussed.

Multigrid Computation of Incompressible Flows Using Two-Equation Turbulence Models: Part II—Applications

1997 ◽  
Vol 119 (4) ◽  
pp. 900-905 ◽  
Author(s):  
X. Zheng ◽  
C. Liao ◽  
C. Liu ◽  
C. H. Sung ◽  
T. T. Huang
Keyword(s):  
Turbulent Flows ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Grid Algorithm ◽  
High Reynolds

In this paper, computational results are presented for three-dimensional high-Reynolds number turbulent flows over a simplified submarine model. The simulation is based on the solution of Reynolds-Averaged Navier-Stokes equations and two-equation turbulence models by using a preconditioned time-stepping approach. A multiblock method, in which the block loop is placed in the inner cycle of a multi-grid algorithm, is used to obtain versatility and efficiency. It was found that the calculated body drag, lift, side force coefficients and moments at various angles of attack or angles of drift are in excellent agreement with experimental data. Fast convergence has been achieved for all the cases with large angles of attack and with modest drift angles.

Prediction of Propeller Tip Vortex Using OpenFOAM

2017 ◽  
Author(s):  
Md Ashim Ali ◽  
Heather Peng ◽  
Wei Qiu ◽  
Rickard Bensow
Keyword(s):  
Vortex Core ◽  
Eddy Viscosity ◽  
Vortex Flow ◽  
Unstructured Grid ◽  
Turbulence Models ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Taylor Model ◽  
Navier Stokes Equation ◽  
Thrust And Torque

It is important to predict the propeller tip vortex flow and its effect on hull vibration and noise. In our previous work, the tip vortex flow of the David Taylor Model Basin (DTMB) 5168 propeller model has been studied based on the Reynolds Averaged Navier-Stokes equation (RANS) solution using various eddy viscosity and Reynolds Stress turbulence models. A set of structural grids were used, however, large Jacobian values of the structural grids around the propeller tip region led to the convergence problem and inaccurate solutions. In the present work, the numerical prediction of the same propeller model was improved by using a steady-state RANS solver simpleFoam in OpenFOAM with locally refined unstructured grid along the tip vortex trajectory. The computed thrust and torque coefficients and the velocity components across the vortex core are compared with experimental data and results in the previous studies. Improvement in the prediction of velocity components across the tip vortex core were achieved.

Numerical Investigation on the Second Stator Boundary Layer Under Clocking Effects: Comparison of v2f and LCL-Model

2008 ◽  
Author(s):  
Axel Heidecke ◽  
Bernd Stoffel
Keyword(s):  
Boundary Layer ◽  
Numerical Investigation ◽  
Separation Bubble ◽  
Measurement Data ◽  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Navier Stokes ◽  
Layer Transition ◽  
Numerical Work ◽  
Boundary Layer Development

This paper presents the results of a numerical investigation of a 1.5-stage low pressure turbine. The main focus of the numerical work was the prediction of the stator-2 boundary layer development under the influence of the stator stator clocking. The turbine profile used for the examination is a so called high-lift-profile and was designed for a laminar-turbulent transition over a steady separation bubble. The boundary conditions were defined by the 1.5-stage test turbine located at our laboratory, where also the measurement data was derived from. The calculations were conducted with a two-dimensional Navier-Stokes solver using a finite volume discretisation scheme. The higher level turbulence models v′2-f and the LCL-turbulence model, which are capable to predict boundary layer transition were compared with measurement data at midspan.

A Methodology for Simulating Compressible Turbulent Flows

2005 ◽  
Vol 73 (3) ◽  
pp. 405-412 ◽  
Author(s):  
Hermann F. Fasel ◽  
Dominic A. von Terzi ◽  
Richard D. Sandberg
Keyword(s):  
Turbulent Flows ◽  
Compressible Flows ◽  
Bluff Body ◽  
Turbulence Modeling ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Fine Grid ◽  
Local Flow

A flow simulation Methodology (FSM) is presented for computing the time-dependent behavior of complex compressible turbulent flows. The development of FSM was initiated in close collaboration with C. Speziale (then at Boston University). The objective of FSM is to provide the proper amount of turbulence modeling for the unresolved scales while directly computing the largest scales. The strategy is implemented by using state-of-the-art turbulence models (as developed for Reynolds averaged Navier-Stokes (RANS)) and scaling of the model terms with a “contribution function.” The contribution function is dependent on the local and instantaneous “physical” resolution in the computation. This physical resolution is determined during the actual simulation by comparing the size of the smallest relevant scales to the local grid size used in the computation. The contribution function is designed such that it provides no modeling if the computation is locally well resolved so that it approaches direct numerical simulations (DNS) in the fine-grid limit and such that it provides modeling of all scales in the coarse-grid limit and thus approaches a RANS calculation. In between these resolution limits, the contribution function adjusts the necessary modeling for the unresolved scales while the larger (resolved) scales are computed as in large eddy simulation (LES). However, FSM is distinctly different from LES in that it allows for a consistent transition between RANS, LES, and DNS within the same simulation depending on the local flow behavior and “physical” resolution. As a consequence, FSM should require considerably fewer grid points for a given calculation than would be necessary for a LES. This conjecture is substantiated by employing FSM to calculate the flow over a backward-facing step and a plane wake behind a bluff body, both at low Mach number, and supersonic axisymmetric wakes. These examples were chosen such that they expose, on the one hand, the inherent difficulties of simulating (physically) complex flows, and, on the other hand, demonstrate the potential of the FSM approach for simulations of turbulent compressible flows for complex geometries.

Determining modes and fractal dimension of turbulent flows

1985 ◽  
Vol 150 ◽  
pp. 427-440 ◽  
Author(s):  
P. Constantin ◽  
C. Foias ◽  
O. P. Manley ◽  
R. Temam
Keyword(s):  
Fractal Dimension ◽  
Turbulent Flows ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Approximate Solutions ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Rigorous Results ◽  
Navier Stokes Equations

Research on the abstract properties of the Navier–Stokes equations in three dimensions has cast a new light on the time-asymptotic approximate solutions of those equations. Here heuristic arguments, based on the rigorous results of that research, are used to show the intimate relationship between the sufficient number of degrees of freedom describing fluid flow and the bound on the fractal dimension of the Navier–Stokes attractor. In particular it is demonstrated how the conventional estimate of the number of degrees of freedom, based on purely physical and dimensional arguments, can be obtained from the properties of the Navier–Stokes equation. Also the Reynolds-number dependence of the sufficient number of degrees of freedom and of the dimension of the attractor in function space is elucidated.

The Influence of Different Turbulence Models on the FlowField Characteristics of an Aerospike Nozzle

2011 ◽  
Vol 110-116 ◽  
pp. 437-443
Author(s):  
S. Noori ◽  
A. Shahrokhi
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Turbulence Models ◽  
State Density ◽  
Navier Stokes ◽  
Field Equations ◽  
Solution Convergence ◽  
Turbulent Models ◽  
Aerospike Nozzle

To improve the calculation of the flow properties of an aerospike nozzle, different turbulent models are studied in this research. The primary shape of the nozzle and the plug is determined through utilizing an approximate method. The flow field is then simulated using Navier-Stokes equations for compressible flow. The computational methodology utilizes steady state density-based formulation and a finite volume cell centered scheme to discretize the flow field equations. To accelerate the solution convergence, the flow field is divided into several zones. Each zone is facilitated with proper unstructured grid and appropriate initial conditions are implemented to each zone. The accuracy and the robustness of wall function based turbulence models i.e. standard and RNG k-ε models are compared with those of Spalart-Allmaras (S-A) and k-ω turbulence models.

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