The present work studies the separated flow in a square channel with ribs on one wall by using the PIV method. In this study, the spacing between ribs is kept constant and the heights of rib are varied in order to investigate the influence of the pitch-to-height ratio, P/e on the flow structures. Depending on the various pitch ratios, the enclosure between ribs can be regarded as closed or open cavity. Results are included for mean velocity, streamlines, skin-friction coefficient, anisotropy parameter, turbulent kinetic energy production and two-point correlation. It is found that the separated shear layer in the closed cavity has strong momentum exchange with the mainstream. By contrast, the fluid contained in the open cavity is self-sustained and the outside streamlines are almost parallel to the bottom wall. Moreover, for the open cavity, the velocity fluctuations become vigorous as the flow reattaches directly on the trailing edge.

1.
Troutt
T. R.
,
Scheelke
B.
, and
Norman
T. R.
,
1984
,
Organized Structures in a Reattaching Separated Flow Field
,
J. Fluid Mechanics
,
143
, pp.
413
427
.
2.
Hasan
M. A. Z.
,
1992
,
The Flow Over a Backward Facing Step under Controlled Perturbation: Laminar Separation
.
J. Fluid Mechanics
,
238
, pp.
73
96
.
3.
Plentovich, E., Stallings, R., and Tracy, M., 1993, Experimental Cavity Pressure Measurements at Subsonic and Transonic Speeds, NACA TP 3358.
4.
Ashcroft
G.
, and
Zhang
X.
,
2005
,
Vortical Structures over Rectangular Cavities at Low Speed
,
Physics of Fluids
,
17
,
015014
015014
.
5.
Leonardi
S.
,
Orlandi
P.
,
Djenidi
L.
, and
Antonia
R. A.
,
2004
,
The Structure of Turbulent Channel Flow with Square Bars on one Wall
,
Int. J. Heat and Fluid Flow
,
25
, pp.
384
392
.
6.
Cui
J.
,
Patel
V. C.
, and
Lin
C-L
,
2003
,
Large-Eddy Simulation of Turbulent Flow in a Channel with Rib Roughness
,
Int. J. Heat and Fluid Flow
,
24
, pp.
372
388
.
7.
Nagano
Y.
,
Hattori
H.
, and
Houra
T.
,
2004
,
DNS of Velocity and Thermal Fields in Turbulent Channel Flow with Transverse-Rib Roughness
,
Int. J. Heat and Fluid Flow
,
25
, pp.
393
403
.
8.
Wang
L.
, and
Sunde´n
B.
,
2005
,
Experimental Investigation of Local Heat Transfer in a Square Duct with Continuous and Truncated Ribs
,
Experimental Heat Transfer
,
18
,
179
197
.
9.
Gao, X., 2002, Heat Transfer and Fluid Flow Investigations in Ribbed Ducts and Impinging Jets Using Liquid Crystal Thermography and PIV, Ph. D., thesis, Division of Heat Transfer, Department of Energy Sciences, Lund Institute of Technology, Lund, Sweden.
10.
Brown
G. L.
, and
Roshko
A.
,
1974
,
On Density Effects and Large Structure in Turbulent Mixing Layers
,
J. Fluid Mechanics
,
64
, pp.
775
816
.
11.
Fro¨hlich
J.
,
Mellen
C. P.
,
Rodi
W.
,
Temmerman
L.
, and
Leschziner
M. A.
,
2005
,
Highly Resolved Large-Eddy Simulation of Separated Flow in a Channel with Streamwise Periodic Constictions
,
J. Fluid Mechanics
,
526
, pp.
19
66
.
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