Research Papers: Fundamental Issues and Canonical Flows

Relaxation of Spatially Advancing Coherent Structures in a Turbulent Curved Channel Flow

[+] Author and Article Information
Koji Matsubara

e-mail: matsu@eng.niigata-u.ac.jp

Tomoya Ohishi

Department of Mechanical and Production
Niigata University,
Ikarashi 2-nocho 8050,
Nishi-ku, Niigata 950-2181, Japan

Keisuke Shida

Sorimachi Giken Co., Ltd.,
Misono 2-2-34, Nagaoka,
Niigata 940-0866, Japan

Takahiro Miura

Tonetsu Corporation,
Kakemama 2-28-25, Ichikawa,
Chiba 272-0142, Japan

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the Journal of Fluids Engineering. Manuscript received September 6, 2012; final manuscript received May 12, 2013; published online July 22, 2013. Assoc. Editor: Zhongquan Charlie Zheng.

J. Fluids Eng 135(9), 091202 (Jul 22, 2013) (9 pages) Paper No: FE-12-1433; doi: 10.1115/1.4024591 History: Received September 06, 2012; Revised May 12, 2013

A direct numerical simulation is made for the incompressible turbulent flow in the 180 deg curved channel with a long straight portion connected to its exit port. An examination is made for how the organized coherent vortex grows and decays in the curved channel: the radius ratio of 0.92, the aspect ratio of 7.2, and the succeeding straight section length of 75 times the channel half width. The 1552 × 91 × 128 ( = 18,427,136) grids are allocated to the computational domain. The frictional-velocity-based Reynolds number is kept at 150 to resolve the long domain including curved and straight regions. In contrast to that the coherent vortex grows along the concave wall, the vortex remains strong in the convex-wall side after the curvature accompanying a tail of the small-scale turbulence near the convex wall. The dissimilarity between the onset and disappearing of the coherent vortex essentially comes from the mean pressure gradient, which aids or averts the near-wall fluid oppositely between the curvature inlet and the exit. The mean flow is decelerated near the inlet of the convex wall to destabilize the flow and to trigger the onset of the coherent vortex. Contrary, the mean flow is accelerated near the exit of the convex wall to weaken the coherent vortex, and is decelerated near the exit of the concave wall to enhance the turbulence. Therefore, the turbulence enhancement and attenuation occurs oppositely between the inlet and exit of the curvature, and the coherent vortex draws a wake in the convex-side rather than the concave-side where it starts.

Copyright © 2013 by ASME
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Fig. 1

Computational domain (case 1). (a) Computational domain and coordinate system, and (b) grid mesh (grid number reduced to 1/8 in each direction for presentation).

Grahic Jump Location
Fig. 2

Mean velocity distribution (case 1). (a) Straight part, (b) ϕ = 45 deg, and (c) ϕ = 135 deg.

Grahic Jump Location
Fig. 3

Friction coefficient (case 1)

Grahic Jump Location
Fig. 4

Contour of mean streamwise velocity, U¯/Um (case 1)

Grahic Jump Location
Fig. 5

Contour of mean pressure, (P¯-Pref)/ρUm2 (case 1)

Grahic Jump Location
Fig. 6

Contour of streamwise velocity fluctuation intensity, urms/Um (case 1)

Grahic Jump Location
Fig. 7

Contour of radial velocity fluctuation intensity, υrms/Um (case 1)

Grahic Jump Location
Fig. 8

Contour of spanwise velocity fluctuation intensity, wrms/Um (case 1)

Grahic Jump Location
Fig. 9

Vectors of time-mean velocity on cross-sectional plane and contour of temperature, (⟨T⟩-TC)/(TH-TC) (case 1). (a) Straight, (b) ϕ = 15 deg, (c) ϕ = 75 deg, (d) ϕ = 135 deg, (e) ϕ = 180 deg, (f) (x−πrm)/δ = 5, (g) (x−πrm)/δ = 15, (h) (x−πrm)/δ = 35, (i) (x−πrm)/δ = 55, and (j) (x−πrm)/δ = 75.

Grahic Jump Location
Fig. 10

Contour of preintensified power spectrum for radial velocity, kzEvvz/Um2 (case 1). (a) Straight, (b) ϕ = 15 deg, (c) ϕ = 75 deg, (d) ϕ = 135 deg, (e) ϕ = 180 deg, (f) (x−πrm)/δ = 5, (g) (x−πrm)/δ = 15, (h) (x−πrm)/δ = 35, (i) (x−πrm)/δ = 55, and (j) (x−πrm)/δ = 75.

Grahic Jump Location
Fig. 11

Isosurface of preintensified power spectrum for radial velocity, kzEvvz/Um2 (case 1). (a) The bird-eye view, (b) the view from the concave-wall side, and (c) the view from the wave-length axis.

Grahic Jump Location
Fig. 12

Isosurface of second invariant for deformation tensor and radial velocity (case 1). (a) x/δ = –4 to ϕ = 30 deg, (b) ϕ = 60 deg to 120 deg, and (c) ϕ = 150 deg to (xπrm)/δ = 12.




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In