Calculation of Fully-Developed Turbulent Flow in Rectangular Ducts With Nonuniform Wall Roughness

1997 ◽  
Vol 119 (3) ◽  
pp. 550-558 ◽  
Author(s):  
M. Naimi ◽  
F. B. Gessner
Keyword(s):  
Reynolds Stress ◽  
Turbulence Models ◽  
Equation Model ◽  
Mean Velocity ◽  
Fully Developed Flow ◽  
Square Duct ◽  
Fully Developed Turbulent Flow ◽  
Flow Situation ◽  
Velocity Turbulence ◽  
Transport Type

The predictive capabilities of four transport-type turbulence models are analyzed by comparing predictions with experimental data for fully-developed flow in (1) a rectangular duct with a step change in roughness on one wall (Case 1), and (2) a square duct with one rib-roughened wall (Case 2). The models include the Demuren-Rodi (DR) k-ε model, the Sugiyama et al. (S) k-ε model, the Launder-Li (LL) Reynolds stress transport equation model, and the differential stress (DS) model proposed recently by the authors. For the first flow situation (Case 1), the results show that the DS model yields improved agreement between predicted and measured primary and secondary mean velocity distributions in comparison to the DR and LL models. For the second flow situation (Case 2), the DS model is superior to the DR and S models for predicting experimentally observed mean velocity, turbulence kinetic energy, and Reynolds stress anisotropy behavior, especially in the vicinity of a corner formed by the juncture of adjacent smooth and rough walls. The results are analyzed in order to explain why the DR model leads to the formation of a spurious secondary flow cell near this corner that is not present in the experimental flow.

Numerical Study of the Turbulent Flow Around a Square Cylinder Near a Wall

2002 ◽  
Author(s):  
Emmanuel Guilmineau ◽  
Patrick Queutey
Keyword(s):  
Reynolds Stress ◽  
Numerical Study ◽  
Turbulence Models ◽  
Equation Model ◽  
Stream Velocity ◽  
Periodic Case ◽  
Square Cylinder ◽  
Mean Velocity ◽  
The One ◽  
Adjacent Wall

Calculations are reported for the flow around a two-dimensional, square cylinder at Re = 22,000 (based on the prism side dimension, D, and the free-stream velocity) placed at various distances from an adjacent wall. The nominal boundary layer thickness is 1.5D. Experiments have indicated that unsteady vortex shedding is suppressed when the wall is relatively close to the cylinder. The turbulent fluctuations are simulated with three turbulence models: the one-equation model of Spalart & Allmaras (1992), the two-equations SST K–ω model (Menter, 1993) and a Reynolds stress Rij–ω closures (Deng & Visonneau, 1999). The paper consists in comparing simulation and experimental results for configurations S/D = 1 (periodic case) and S/D = 0.25 (stationary case). Predicted and measured distributions of the mean velocity, Reynolds stress tensor and surface pressures are compared. Although the agreement is very good in general, observed discrepancies are discussed.

scholarly journals Simulation of Rotating Channel Flow With Heat Transfer: Evaluation of Closure Models

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Alan S. Hsieh ◽  
Sedat Biringen ◽  
Alec Kucala
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Stress ◽  
Channel Flow ◽  
Turbulence Models ◽  
Turbulent Channel Flow ◽  
Turbulent Heat ◽  
Stress Distributions ◽  
Mean Velocity ◽  
Closure Models

A direct numerical simulation (DNS) of spanwise-rotating turbulent channel flow was conducted for four rotation numbers: Rob=0, 0.2, 0.5, and 0.9 at a Reynolds number of 8000 based on laminar centerline mean velocity and Prandtl number 0.71. The results obtained from these DNS simulations were utilized to evaluate several turbulence closure models for momentum and heat transfer transport in rotating turbulent channel flow. Four nonlinear eddy viscosity turbulence models were tested and among these, explicit algebraic Reynolds stress models (EARSM) obtained the Reynolds stress distributions in best agreement with DNS data for rotational flows. The modeled pressure–strain functions of EARSM were shown to have strong influence on the Reynolds stress distributions near the wall. Turbulent heat flux distributions obtained from two explicit algebraic heat flux models (EAHFM) consistently displayed increasing disagreement with DNS data with increasing rotation rate.

scholarly journals The Development of the Mean Flow and Turbulence Structure in an Annular S-Shaped Duct

1994 ◽  
Author(s):  
K. M. Britchford ◽  
J. F. Carrotte ◽  
S. J. Stevens ◽  
J. J. McGuirk
Keyword(s):  
Reynolds Stress ◽  
Laser Doppler Anemometry ◽  
Reynolds Shear Stress ◽  
Turbulence Models ◽  
Test Facility ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Mean Velocity ◽  
Curvature Effects ◽  
The Mean

This paper describes an investigation of the mean and fluctuating flow field within an annular S-shaped duct which is representative of that used to connect the compressor spools of aircraft gas turbine engines. Data was obtained from a fully annular test facility using a 3-component Laser Doppler Anemometry (LDA) system. The measurements indicate that development of the flow within the duct is complex and significantly influenced by the combined effects of streamwise pressure gradients and flow curvature. In addition CFD predictions of the flow, using both the k-ε and Reynolds stress transport equation turbulence models, are compared with the experimental data. Whereas curvature effects are not described properly by the k-ε model, such effects are captured more accurately by the Reynolds stress model leading to a better prediction of the Reynolds shear stress distribution. This, in turn, leads to a more accurate prediction of the mean velocity profiles, as reflected by the boundary layer shape parameters, particularly in the critical regions of the duct where flow separation is most likely to occur.

Experimental and Numerical Investigation of Turbulent High Reynolds Number Flows in a Square Duct With 90-Degree Streamwise Curvature: Part 1 — Experiment

2003 ◽  
Author(s):  
Faustin Ondore
Keyword(s):  
Turbulent Flows ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Flow Visualisation ◽  
Square Duct ◽  
Plane Flow ◽  
Convex Wall ◽  
The Mean ◽  
Stress Models

This study was aimed at obtaining a better understanding of turbulent flows in a square duct with a 90° bend, using both experimental and numerical techniques. Turbulent flows that are subjected to streamwise curvature occur in numerical engineering applications. These flows are known to experience extra rates of strain in the plane of mean shear in comparison to plane flows. Hence the gross parameters, such as the mean flow velocities, turbulence intensities and Reynolds stresses are altered dramatically from the plane flow characteristics. The flows examined are specified by the free-stream entry velocities of 12.3 m/s and 20.4 m/s measured at 1.01 duct height upstream of the bend entry plane. These velocities correspond to Reynolds numbers 3.56 × 105 and 6.43 × 105 respectively. The duct has a cross-section of 0.457 × 0.457 m 2 and the mean radius of curvature to duct height ratio is 1:21. Airflow from a wind tunnel passes through an upstream tangent of 1.31 duct height before entering the bend. The flow then exits the bend into a 7.0 duct height downstream tangent before discharging into the atmosphere. The experimental part involved hot-wire measurements. Flow visualisation was performed by smoke in a region close to the convex wall at the bend exit to confirm the numerical prediction of recirculating flow in that area. The numerical part of the investigation was based on the solution of the governing differential equations for turbulent flows in conjunction with a number of turbulence models. The discretisation of the equations was achieved using a finite-volume technique and different discretisation schemes. The main turbulence model used for the study was the Reynolds Stress Model, but the comparisons of the results were also made with those from the standard κ-ε and the RNG-κ-ε turbulence models. The boundary conditions for these simulations were obtained as part of the experimental investigations. Numerical calculations with the Reynolds stress models show a separated flow near the convex wall starting at the bend exit, which was confirmed by experiment using flow visualisation by smoke. The Reynolds stress models are observed to be superior in comparison with the standard κ-ε and the RNG-κ-ε turbulence models in terms of accuracy. Further conclusions from this work can be summarised as: 1. The proper numerical resolution of this type of flow is dependent on the turbulence model formulations as well as numerical procedures. The results highlight the limitations of the generality of turbulence models when used to model more intricate features of complex flows. 2. The need for more accurate experimental techniques in support of improvement of turbulence models is thus underlined.

A Calculation Method for Developing Turbulent Flow in Rectangular Ducts of Arbitrary Aspect Ratio

1995 ◽  
Vol 117 (2) ◽  
pp. 249-258 ◽  
Author(s):  
M. Naimi ◽  
F. B. Gessner
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Transport Equation ◽  
Reynolds Stress ◽  
Equation Model ◽  
Strain Component ◽  
Square Duct ◽  
Damping Function ◽  
Strain Behavior ◽  
Proposed Model

This paper describes a full Reynolds stress transport equation model for predicting developing turbulent flow in rectangular ducts. The pressure-strain component of the model is based on a modified form of the Launder, Reece and Rodi pressure-strain model and the use of a linear wall damping function. Predictions based on this model are compared with predictions referred to high Reynolds number and low Reynolds number k–ε transport equation models and with experimental data taken in square and rectangular ducts. The results indicate that the proposed model yields improved predictions of primary flow development and Reynolds stress behavior in a square duct. The proposed model also yields Reynolds stress anisotropy and secondary flow levels that are compatible and agree well with experiment, without recourse to a quadratic damping function to model near-wall pressure-strain behavior.

Characteristics of the wake behind a cascade of airfoils

1973 ◽  
Vol 61 (4) ◽  
pp. 707-730 ◽  
Author(s):  
R. Raj ◽  
B. Lakshminarayana
Keyword(s):  
Experimental Investigation ◽  
Decay Rate ◽  
Flat Plate ◽  
Reynolds Stress ◽  
Turbulence Intensity ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Velocity Defect ◽  
Velocity Turbulence ◽  
Far Wake

An analytical and experimental investigation of the near and far wake characteristics of a cascade of airfoils is reported in this paper. The measurement of mean velocity, turbulence intensity and Reynolds stress across the wake at several distances downstream of the cascade indicates that the wake is asymmetrical and this asymmetry is maintained even up to 3/4 chord length. Experiments carried out at three incidences reveal that the decay of the wake defect is strongly dependent on the downstream variation of the wake edge velocity. For a cascade, the decay rate of the wake defect is found to be slower than that of a flat plate, cylinder or symmetrical airfoil (at zero incidence). The level of turbulence and Reynolds stresses are found to be high and some comments are made regarding self-preservation and structure of the flow. Semi-theoretical expressions are given for the wake profile, and decay of the velocity defect, turbulence intensity and Reynolds stress.

Statistical Model of a Self-Similar Turbulent Plane Shear Layer

1998 ◽  
Vol 120 (2) ◽  
pp. 263-273 ◽  
Author(s):  
Zuu-Chang Hong ◽  
Ming-Hua Chen
Keyword(s):  
Shear Layer ◽  
Moment Method ◽  
Turbulence Models ◽  
Equation Model ◽  
Turbulence Energy ◽  
Turbulence Structure ◽  
Mean Velocity ◽  
Plane Shear ◽  
Self Similar ◽  
Turbulent Plane

A turbulence probability density function (pdf) equation model is employed to solve a self-similar turbulent plane shear layer. The proper similarity variable was introduced into the problem of interest to reduce the pdf equation into a spatially one-dimensional equation, which is still three dimensional in velocity space. Then the approximate moment method is employed to solve this simplified pdf equation. By the solutions of this equation, the various one-point mean quantities are immediatelly available. Agreement of the calculated mean velocity, turbulent energy and Reynolds stress with the available experimental data is generally satisfactory indicating that the pdf equation model and the moment method can quantitatively describe the statistics of free turbulence. Additionally, the balance of turbulence energy was calculated and discussed subsequently. It shows that the pdf methods are of more potential in revealing turbulence structure than conventional turbulence models.

Turbulence in Small Air Jets at Exit Velocities Up to 705 Feet per Second

1957 ◽  
Vol 24 (3) ◽  
pp. 349-354
Author(s):  
L. W. Lassiter
Keyword(s):  
Turbulence Intensity ◽  
Broad Band ◽  
Axial Distance ◽  
Intensity Scale ◽  
Mean Velocity ◽  
Fully Developed Flow ◽  
Velocity Increase ◽  
The Core ◽  
Air Jets ◽  
Velocity Turbulence

Abstract Turbulence intensity, scale, and spectrum measurements were made on model jets of 1 in. and 2-in. diam at various mean velocities. The indications are that only in the fully developed flow is turbulence intensity invariant with mean velocity; intensity in the core, in the turbulent annulus, and in the transition region decreases in varying degrees with mean velocity increase. Longitudinal and radial scales of turbulence were found to increase in the annulus in proportion to about the square root of axial distance, and longitudinal scale is about 65 per cent greater than radial scale. Both radial and longitudinal scales seem to be essentially constant with mean velocity. Turbulence spectra were found to consist of a sharply peaked band of frequencies in the core, degenerating to a slightly peaked broad band at points in the mixing regions.

scholarly journals A Comparison Between Measurements and Turbulence Models in a Turbine Cascade Passage

1988 ◽  
Author(s):  
Pietro Zunino ◽  
Marina Ubaldi ◽  
Antonio Satta ◽  
Enrico Peisino
Keyword(s):  
Turbulence Models ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Rotor Blades ◽  
Turbine Cascade ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Closure Models ◽  
Experimental Values ◽  
Velocity Turbulence

Detailed measurements of mean velocity, turbulence intensity and Reynolds stresses have been performed in the passage of a cascade of turbine rotor blades. By using the experimental values of the mean velocity, the turbulence quantities are computed with three different turbulence closure models. The results are analysed and compared with the experimental data. The capability of the closure models to describe the turbulence development associated with secondary flows in a turbine cascade is discussed.

Turbulent flow in a rectangular duct

1976 ◽  
Vol 78 (2) ◽  
pp. 289-315 ◽  
Author(s):  
A. Melling ◽  
J. H. Whitelaw
Keyword(s):  
Turbulent Flow ◽  
Turbulence Models ◽  
Laser Doppler Anemometer ◽  
Laser Doppler ◽  
Rectangular Duct ◽  
Reynolds Stresses ◽  
Mean Velocity ◽  
Fully Developed Flow ◽  
Developing Flow ◽  
Better Than

A detailed experimental study of developing turbulent flow in a rectangular duct was made using a laser-Doppler anemometer. The purposes of the work were to obtain data of value to fluid mechanicists, particularly those interested in the development and testing of mathematical turbulence models, and to evaluate the performance of the anemometer. For the first purpose, contours of axial mean velocity and turbulence intensity were measured in the developing flow, and all three mean velocity components and five of the six Reynolds stresses were obtained in the nearly fully developed flow.The symmetry of the present flow appears to be better than that of previous measurements and the range of measurements is more extensive. In addition, the laser-Doppler anemometer has the potential advantage, particularly in the measurement of secondary velocities, of avoiding probe interference.

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