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Research Papers: Flows in Complex Systems

# Effect of a Triangular Rib on a Flat Plate Boundary Layer

[+] Author and Article Information

Turbulence and Energy Laboratory,
Centre for Engineering Innovation,
University of Windsor,
401 Sunset Avenue,

P. Henshaw

Turbulence and Energy Laboratory,
Centre for Engineering Innovation,
University of Windsor,
401 Sunset Avenue,
e-mail: henshaw@uwindsor.ca

D. S.-K. Ting

Mem. ASME
Turbulence and Energy Laboratory,
Centre for Engineering Innovation,
University of Windsor,
401 Sunset Avenue,
e-mail: dting@uwindsor.ca

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 26, 2015; final manuscript received July 23, 2015; published online August 21, 2015. Assoc. Editor: D. Keith Walters.

J. Fluids Eng 138(1), 011101 (Aug 21, 2015) (11 pages) Paper No: FE-15-1129; doi: 10.1115/1.4031161 History: Received February 26, 2015; Revised July 23, 2015

## Abstract

The flow structure downstream of a triangular rib over a thin plate placed in a wind tunnel was experimentally investigated using a boundary layer hotwire anemometer. Flow and boundary layer characteristics, such as thickness, shape, and turbulence parameters, were studied at different freestream velocities and streamwise locations corresponding to ReX of 1.7 $×$ 104–2.8 $×$ 105 for plates without and with a leading edge rib. It was found that the boundary layer of the flow over a ribbed wall was 3–3.5 times thicker and had higher turbulence intensity and smaller turbulence length scales compared to its smooth wall counterpart.

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## Figures

Fig. 1

Rib mounted flat plate schematic

Fig. 2

Test section side view

Fig. 3

Velocity profiles for smooth and ribbed wall at (a) U = 4 m/s, (b) U = 6.8 m/s, and (c) U = 9 m/s

Fig. 4

Flow over a (a) square-ribbed surface [14] and (b) wedge-ribbed surface [3]

Fig. 5

Liu et al. [14] velocity profile over a square-ribbed surface

Fig. 6

Normalized velocity profiles inside the boundary layer at U = 9 m/s for the (a) smooth and (b) ribbed wall

Fig. 7

Turbulent boundary layer normalized velocity profile of DeGraaff and Eaton [32]

Fig. 8

Wake parameter at U = 9 m/s

Fig. 9

Turbulence intensity profiles for smooth and ribbed wall at (a) U = 4 m/s, (b) U = 6.8 m/s, and (c) U = 9 m/s

Fig. 10

Wall-normal location of maximum streamwise Tu: (a) present study at U = 9 m/s and (b) Liu et al. [14]

Fig. 11

FFT of velocity fluctuation signal at Y/H = 1

Fig. 12

Autocorrelation coefficient for ribbed wall at X/H = 20, Y/H = 2.2, and U = 9 m/s, the dashed line shows the parabola fitted curve to the first five points of R(τ)

Fig. 13

Ribbed wall integral length scale at U = 9 m/s

Fig. 14

Ribbed wall integral length scale at (a) U = 4 m/s, (b) U = 6.8 m/s, and (c) U = 9 m/s

Fig. 15

Taylor microscale in the boundary layer at U = 9 m/s

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