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Research Papers: Fundamental Issues and Canonical Flows

# Laminarization of Internal Flows Under the Combined Effect of Strong Curvature and Rotation

[+] Author and Article Information
K. M. Guleren1

Faculty of Engineering, Mechanical Engineering Department, Cumhuriyet University, 58140 Sivas, Turkeymelihguleren@cumhuriyet.edu.tr

I. Afgan

Institute of Avionics and Aeronautical Engineering, Air University, Sector E-9, Islamabad, Pakistan

A. Turan

School of MACE, The University of Manchester, George Begg Building, Sackville Street, P.O. Box 88, Manchester M60 1 QD, UK

1

Corresponding author.

J. Fluids Eng 130(9), 091202 (Aug 12, 2008) (11 pages) doi:10.1115/1.2953298 History: Received September 10, 2007; Revised May 08, 2008; Published August 12, 2008

## Abstract

The laminarization phenomenon for the flow under the combined effect of strong curvature and rotation is discussed based on numerical predictions of large-eddy simulation (LES). Initially, the laminarization process is presented for the fully developed flow inside a spanwise rotating straight square duct. LES predictions over a wide range of rotation numbers $(Ro=0–5)$ show that the turbulent kinetic energy decreases monotonically apart from $0.2. Subsequently, a spanwise rotating $U$-duct flow is considered with $Ro=±0.2$. The interaction of curvature and Coriolis induced secondary flows enhances the turbulence for the negative rotating case, whereas this interaction ensues strong laminarization for the positive rotating case. Finally, the laminarization is presented in the impeller of a typical centrifugal compressor, rotating at a speed of $Ω=1862rpm$$(Ro=0.6)$. The resulting LES predictions are observed to be better than those of Reynolds-averaged Navier-Stokes (RANS) in the regions where turbulence is significant. However, for the regions dominated by strong laminarization, RANS results are seen to approach those of LES and experiments.

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## Figures

Figure 1

Cross sections of the computational mesh. (a) Rotating straight duct. (b) Rotating U-duct. (c) Centrifugal compressor.

Figure 2

Stationary channel flow in wall coordinates. (a) Mean velocity. (b) Mean turbulent kinetic energy. (△) DNS of Moser (49), (◻) DNS of Alveluis (50), (—) WALE model, (–⋅–⋅–) DYNKE model, and (-----) DYN model

Figure 3

Rotating channel flow results in global coordinates. (a) Mean velocity. (b) Mean turbulent kinetic energy. (◇) DNS data of Kristoffersen and Andersson (32), (—) WALE model, (–⋅–⋅–) DYNKE model, and (-----) DYN model.

Figure 4

Mean primary flow contours (top subfigures) and secondary flow distributions (bottom subfigures) for the square duct

Figure 5

Plane-averaged wall shear stress on the enclosed walls of the square duct. (PS: pressure side, SS: suction side, and LS: lateral side).

Figure 6

Volume-averaged mean turbulent kinetic energy and turbulent normal stresses for the square duct

Figure 7

Distribution of the volume-averaged mean turbulent kinetic energy for the square duct

Figure 8

Volume-averaged Reynolds stress budget terms for the square duct. ⟨u′u′⟩ (a), ⟨v′v′⟩ (b), and ⟨w′w′⟩ (c).

Figure 9

The ratio of the production to the dissipation for the square duct. Volume-averaged distribution (a). Wall-normal distribution on Z∕D=0.5 (b).

Figure 10

Contours of mean streamwise velocity ⟨U⟩∕Ub (a) and mean turbulent kinetic energy ⟨k⟩∕Ub2 (b)

Figure 11

Contours of kRo∕k0−1 for positive rotating (a) and negative rotating U-ducts (b)

Figure 12

Secondary velocity contours (⟨V⟩2+⟨W⟩2)0.5∕Ub and streamlines at the bend exit for stationary (a) positive rotating (b) and negative rotating cases (c)

Figure 13

Normalized turbulent kinetic energy distribution 100×√k∕Utip on the midspan plane for the LSCC. First column: Ω=1862rpm. Second column: Ω=0rpm.

Figure 14

Normalized turbulent kinetic energy distribution 100×k∕Utip at the meridional cross sections for the LSCC. First column: Ω=1862rpm. Second column: Ω=0rpm.

Figure 15

The pitchwise (blade-to-blade) variation of the meridional velocity near the mid span (a) and near the shroud (b)

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