WITHDRAWN: NUMERICAL STUDY OF GENERATION OF STEADY STREAMWISE STREAKS IN DUCT FLOW

2018 ◽  
Author(s):  
Z. Tigrine ◽  
A. Bouabdallah ◽  
F. Mokhtari
Keyword(s):  
Numerical Study ◽  
Duct Flow ◽  
Streamwise Streaks

End-Wall Secondary Flow Control Using Engineered Residual Surface Structure

2016 ◽  
Author(s):  
X. Miao ◽  
Q. Zhang ◽  
C. Atkin ◽  
Z. Sun
Keyword(s):  
Flow Control ◽  
Surface Structure ◽  
Secondary Flow ◽  
End Milling ◽  
Numerical Study ◽  
Small Scale ◽  
Duct Flow ◽  
Design Guideline ◽  
Residual Structure ◽  
End Wall

Residual surface roughness is often introduced in the manufacture process with ball-end or fillet-end milling. Instead of paying extra cost to remove these small-scale residual surface structures, there is a potential usage of them as flow control device. This numerical study therefore explores the ability of engineered surface structure in controlling the endwall secondary flow in turbomachinery. The CFD method is validated against the existing experimental data obtained for a 90 degree turning duct flow with a single rib fence placed on the end-wall. The working principle of the engineered surface structure is revealed through detailed analysis on the flow produced by multiple small fences and grooves mimicking the residual surface. The results consistently show that addition of engineered residual structure on flow surface can effectively reduce the magnitude of stream-wise vorticity associated with secondary flow and alleviate its lift-off motion. In the end, a general working mechanism and design guideline for optimizing the residual structure are summarized.

Leakage effects in laminar duct flow: a numerical study

1992 ◽  
Vol 49 (1) ◽  
pp. 117-134
Author(s):  
Helge I. Andersson ◽  
Knut L. Tiseth
Keyword(s):  
Numerical Study ◽  
Duct Flow

scholarly journals Experimental and computational investigation for three dimensional duct flow with modified arrangement ribs turbulators

2020 ◽  
pp. 93-93
Author(s):  
Khudheyer Mushatet ◽  
Sarah Nashee
Keyword(s):  
Friction Factor ◽  
Numerical Study ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Duct Flow ◽  
Computational Investigation ◽  
Performance Factor ◽  
Pitch Ratio ◽  
Overall Performance ◽  
Good Agreement

A combined numerical and experimental study is conducted to test the heat transfer enhancement and friction factor characteristics for a rectangular duct fitted with three cases of ribs turbulators: continuous ribs (CR), intermittent-continuous-intermittent ribs (ICIR) and intermittent ribs (IR). Experiments are conducted within a turbulent flow for Reynolds numbers values varied from 10000 to 35000, pitch ratio (p/e) equal to 5 and height ratio (e/H) of 0.33. The numerical study carried out using ANSYS FlUENT17.2. The turbulence is modeled by using k-? model. The results showed that the case of intermittent ribs provide the highest over performance factor while the continuous ribs indicate less overall performance factor among the considered cases. In addition, the results show that the highest values of the friction factor are marked from the case of intermittent ribs (IR) and then the case of intermittent-continuous-intermittent ribs (ICIR) followed by continuous rib case (CR). The continuous rib case showed the lowest friction factor. The experimental results showed a good agreement with the computational results.

scholarly journals CONJUGATE MIXED CONVECTION IN AIR-COOLED HEAT SINKS USING A NON-BOUSSINESQ APPROACH

2003 ◽  
Vol 2 (1) ◽  
Author(s):  
C. R. DeAndrade ◽  
A. V. Pantaleão ◽  
E. L. Zaparoli
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Numerical Study ◽  
Mathematical Formulation ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Heat Sinks ◽  
Thermal Conductivity Ratio ◽  
Analysis Tool ◽  
Duct Flow

This work reports a numerical study of the mixed convection in finned duct flow that occurs in heat sinks devices. The laminar flow is considered fully developed and the convection-conduction coupling is treated by a conjugated approach. The mathematical formulation of this problem is constituted by the mass, momentum and energy equations. The partial differential equations system is solved by the Galerkin finite element method, adopting a pressure Poisson equation to establish the pressure-velocity coupling and to obtain a mass conserving flow. The results using the classical Boussinesq approximation (density varies linearly with the temperature in the buoyancy-term) are compared with the non-Boussinesq approach (density variation in all terms of the governing equations) showing that both the heat transfer and friction factor are affected by the new considerations. The duct aspect ratio and the solid to fluid thermal conductivity ratio influences on the heat transfer rate are also analyzed. This analysis tool was also shown appropriate for the optimization of electronic components air-cooled heat sinks.

A numerical study of particle wall-deposition in a turbulent square duct flow

2006 ◽  
Vol 170 (1) ◽  
pp. 12-25 ◽  
Author(s):  
C.M. Winkler ◽  
Sarma L. Rani ◽  
S.P. Vanka
Keyword(s):  
Numerical Study ◽  
Duct Flow ◽  
Square Duct ◽  
Wall Deposition

scholarly journals Numerical study of magnetohydrodynamic duct flow at high Reynolds and Hartmann numbers

2012 ◽  
Vol 704 ◽  
pp. 421-446 ◽  
Author(s):  
Dmitry Krasnov ◽  
Oleg Zikanov ◽  
Thomas Boeck
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Numerical Study ◽  
Transverse Magnetic ◽  
Field Analysis ◽  
Small Scale ◽  
Duct Flow ◽  
Mean Velocity ◽  
Magnetic Field Analysis ◽  
The Magnetic Field

AbstractHigh-resolution direct numerical simulations are conducted to analyse turbulent states of the flow of an electrically conducting fluid in a duct of square cross-section with electrically insulating walls and imposed transverse magnetic field. The Reynolds number of the flow is $1{0}^{5} $ and the Hartmann number varies from $0$ to $400$. It is found that there is a broad range of Hartmann numbers in which the flow is neither laminar nor fully turbulent, but has laminar core, Hartmann boundary layers and turbulent zones near the walls parallel to the magnetic field. Analysis of turbulent fluctuations shows that each zone consists of two layers: the boundary layer near the wall characterized by small-scale turbulence and the outer layer dominated by large-scale vortical structures strongly elongated in the direction of the magnetic field. We also find a peculiar scaling of the mean velocity, according to which the reciprocal von Kármán coefficient grows nearly linearly with the distance to the wall.

A Numerical Study of Laminar 90-Degree Bend Duct Flow With Different Discretization Schemes

1991 ◽  
Vol 113 (4) ◽  
pp. 563-568 ◽  
Author(s):  
R. W. Yeo ◽  
P. E. Wood ◽  
A. N. Hrymak
Keyword(s):  
Numerical Study ◽  
Higher Order ◽  
Staggered Grid ◽  
Grid Refinement ◽  
Duct Flow ◽  
Governing Equations ◽  
Square Duct ◽  
Flow Problems ◽  
Discretization Schemes ◽  
Curvilinear Coordinate

Three different discretization schemes were used to study the flow in a 90-degree bend square duct. The numerical method consists of a general curvilinear coordinate formulation of the governing equations and a non-staggered grid for the variables. A stable method of implementing the higher-order schemes is proposed. The second-order upwinding and QUICK schemes give results which compare more favourably with the experimental data than the first-order upwinding method. In 3-D flow problems, the grid-refinement is severely limited by the amount of computer storage and the use of higher-order upwinding schemes provides a better alternative in obtaining accurate flow predictions.

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