Numerical calculation of Reynolds stresses in a square duct with secondary flow

1974 ◽  
Vol 7 (3) ◽  
pp. 151-161 ◽  
Author(s):  
D. Naot ◽  
A. Savit ◽  
M. Wolfshtin
Keyword(s):  
Numerical Calculation ◽  
Secondary Flow ◽  
Reynolds Stresses ◽  
Square Duct

Turbulence Intensity Distribution for Flow Along a Streamwise External Corner

2002 ◽  
Author(s):  
Khalid A. M. Moinuddin ◽  
Peter N. Joubert ◽  
Min S. Chong
Keyword(s):  
Secondary Flow ◽  
Turbulence Intensity ◽  
Leading Edge ◽  
Two Dimensional ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
General Behaviour ◽  
Flow Measurements ◽  
Square Duct ◽  
Normal Distance

This work continues the studies of Moinuddin et al. [1], where experiments were performed on a streamwise external corner. The streamwise development of turbulent boundary layer over an external corner (chine) is influenced by secondary flow which is driven three-dimensionally. The direct effect of this secondary flow is to increase the drag force. Here secondary flow, which is known as Prandtl’s second kind, is induced by inequality of Reynolds stresses around the corner. This flow is expected to exhibit symmetry about the corner bisector. Moinuddin et al. [2,3] have established the symmetry of this flow based upon mean flow measurements. Normal wire measurements for the streamwise turbulence intensity profiles u′2+, measured at about Reθ 5700 and 4.7 m from the model leading edge, are presented in this paper. Mean flow measurements show excellent agreement between Pitot tube and normal wire measurements. Comparisons are made for u′2+, profiles at equal spanwise distance, from the corner, on both surfaces. The profiles agree quite well having nominal deviation depending on spanwise and normal distance from the corner. Isointensity contours also depict symmetrical turbulence distribution. It is also revealed that far from the corner, turbulence profiles agree well with the standard two-dimensional turbulence profile. The measurements agrees with the general behaviour expected from this kind of flow as reported by Xu & Pollard [4] from their LES calculation of flow in an annular square duct.

A Numerical Study on the Generation Mechanism of Turbulence-Driven Secondary Flow in a Square Duct

1993 ◽  
Vol 115 (1) ◽  
pp. 172-175 ◽  
Author(s):  
Hyon Kook Myong
Keyword(s):  
Secondary Flow ◽  
Numerical Study ◽  
Reynolds Shear Stress ◽  
Secondary Flows ◽  
Generation Mechanism ◽  
Streamwise Vorticity ◽  
Reynolds Stresses ◽  
Cross Sectional ◽  
Square Duct ◽  
Vorticity Transport

The generation mechanism of turbulence-driven secondary flows in a square duct is numerically investigated in the present study by using an anisotropic low-Reynolds-number k–ε turbulence model. Special attention is directed to the distributions of turbulence quantities, which are responsible for the secondary flow generation, such as the anisotropy of normal Reynolds stresses and the secondary Reynolds shear stress acting on the cross-sectional plane. The vorticity transport process is also discussed in detail, based on the numerical evaluation of the individual terms which appear in the streamwise vorticity transport equation.

scholarly journals Reynolds number dependence of mean flow structure in square duct turbulence

2010 ◽  
Vol 644 ◽  
pp. 107-122 ◽  
Author(s):  
ALFREDO PINELLI ◽  
MARKUS UHLMANN ◽  
ATSUSHI SEKIMOTO ◽  
GENTA KAWAHARA
Keyword(s):  
Reynolds Number ◽  
Secondary Flow ◽  
Buffer Layer ◽  
Turbulent Flows ◽  
Reynolds Numbers ◽  
The Other ◽  
Streamwise Vorticity ◽  
Square Duct ◽  
Layer Structures ◽  
The Mean

We have performed direct numerical simulations of turbulent flows in a square duct considering a range of Reynolds numbers spanning from a marginal state up to fully developed turbulent states at low Reynolds numbers. The main motivation stems from the relatively poor knowledge about the basic physical mechanisms that are responsible for one of the most outstanding features of this class of turbulent flows: Prandtl's secondary motion of the second kind. In particular, the focus is upon the role of flow structures in its generation and characterization when increasing the Reynolds number. We present a two-fold scenario. On the one hand, buffer layer structures determine the distribution of mean streamwise vorticity. On the other hand, the shape and the quantitative character of the mean secondary flow, defined through the mean cross-stream function, are influenced by motions taking place at larger scales. It is shown that high velocity streaks are preferentially located in the corner region (e.g. less than 50 wall units apart from a sidewall), flanked by low velocity ones. These locations are determined by the positioning of quasi-streamwise vortices with a preferential sign of rotation in agreement with the above described velocity streaks' positions. This preferential arrangement of the classical buffer layer structures determines the pattern of the mean streamwise vorticity that approaches the corners with increasing Reynolds number. On the other hand, the centre of the mean secondary flow, defined as the position of the extrema of the mean cross-stream function (computed using the mean streamwise vorticity), remains at a constant location departing from the mean streamwise vorticity field for larger Reynolds numbers, i.e. it scales in outer units. This paper also presents a detailed validation of the numerical technique including a comparison of the numerical results with data obtained from a companion experiment.

scholarly journals Computation of turbulent flow in a square duct: aspects of the secondary flow and its origin

1994 ◽  
Vol 23 (1) ◽  
pp. 157-176 ◽  
Author(s):  
F.M. Wang ◽  
Y.T. Chew ◽  
B.C. Khoo ◽  
K.S. Yeo
Keyword(s):  
Turbulent Flow ◽  
Secondary Flow ◽  
Square Duct

514 Turbulence Structures and Secondary Flow in a Square Duct

2008 ◽  
Vol 2008.83 (0) ◽  
pp. _5-21_
Author(s):  
Genta KAWAHARA ◽  
Atsushi SEKIMOTO ◽  
Markus UHLMANN ◽  
Alfredo PINELLI
Keyword(s):  
Secondary Flow ◽  
Square Duct ◽  
Turbulence Structures

The Torsion Effect on Fully Developed Laminar Flow in Helical Square Ducts

1993 ◽  
Vol 115 (2) ◽  
pp. 292-301 ◽  
Author(s):  
Wen-Hwa Chen ◽  
Ray Jan
Keyword(s):  
Laminar Flow ◽  
Secondary Flow ◽  
Friction Factor ◽  
Stokes Equations ◽  
Axial Flow ◽  
Outer Wall ◽  
Square Duct ◽  
Torsion Effect ◽  
Inclined Angle ◽  
Curvature And Torsion

The continuity equation and Navier-Stokes equations derived from a non-orthogonal helical coordinate system are solved by the Galerkin finite-element method in an attempt to study the torsion effect on the fully developed laminar flow in the helical square duct. Since high-order terms of curvature and torsion are considered, the approach is also applicable to the problems with finite curvature and torsion. The interaction effects of curvature, torsion, and the inclined angle of the cross section on the secondary flow, axial velocity, and friction factor in the helical square duct are presented. The results show that the torsion has more pronounced effect on the secondary flow rather than the axial flow. In addition, unlike the flow in the toroidal square duct, Dean’s instability of the secondary flow, which occurs near the outer wall in the helical square duct, can be avoided due to the effects of torsion and/or inclined angle. In such cases, a decrease of the friction factor is observed. However, as the pressure gradient decreases to a small value, the friction factor for the toroidal square duct is also applicable to the helical square duct.

Turbulence Modeling of Axial Flow in a Bare Rod Bundle

1979 ◽  
Vol 101 (4) ◽  
pp. 628-634 ◽  
Author(s):  
J. G. Bartzis ◽  
N. E. Todreas
Keyword(s):  
Secondary Flow ◽  
Turbulent Flows ◽  
Axial Velocity ◽  
Nuclear Reactor ◽  
Turbulence Modeling ◽  
Three Dimensional ◽  
Axial Flow ◽  
Reynolds Stresses ◽  
Rod Bundle ◽  
Aspect Ratios

Temperature distribution within the rod bundle of a nuclear reactor is of major importance in nuclear reactor design. However temperature information presupposes knowledge of the hydrodynamic behavior of the coolant which is the most difficult part of the problem due to the complexity of the turbulence phenomena. In the present work a two equation turbulence model—a strong candidate for analyzing actual three dimensional turbulent flows—has been used to predict fully developed flow of infinite bare rod bundle of various aspect ratios (P/D). The model has been modified to take into account anisotropic effects of eddy viscosity. Secondary flow calculations have been also performed although the model seems to be too rough to predict the secondary flow correctly. Heat transfer calculations have been performed to confirm the importance of anisotropic viscosity in temperature predictions. Experimental measurements of the distribution of axial velocity, turbulent axial velocity, turbulent kinetic energy and radial Reynolds stresses were performed in the developing and fully developed regions. A two channel Laser Doppler Anemometer working in the reference mode with forward scattering was used to perform the measurements in a simulated interior subchannel of a triangular rod array with P/D = 1.124. Comparisons between the analytical results and the results of this experiment as well as other experimental data in rod bundle arrays available in the literature are presented. The predictions are in good agreement with the results for high Reynolds numbers.

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