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Technical Brief

Characteristics of Turbulent Flows Over Forward Facing Steps in Adverse Pressure Gradients Based on Two-Point Analyses

[+] Author and Article Information
Hassan Iftekhar, Martin Agelin-Chaab

Faculty of Engineering and Applied Science,
Department of Automotive, Mechanical and
Manufacturing Engineering,
University of Ontario Institute of Technology,
2000 Simcoe Street North,
Oshawa, ON L1H 7K4, Canada

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received September 5, 2016; final manuscript received April 2, 2017; published online July 21, 2017. Assoc. Editor: Mark F. Tachie.

J. Fluids Eng 139(11), 114501 (Jul 21, 2017) (6 pages) Paper No: FE-16-1578; doi: 10.1115/1.4036666 History: Received September 05, 2016; Revised April 02, 2017

This study reports the results of turbulent flows forward facing steps (FFS) in pressure gradients using a particle image velocimetry (PIV) technique to obtain data up to 68 step heights downstream. The contours of two-point velocity correlations indicate that regardless of the pressure gradients, the physical size of the coherent structures characterized by the autocorrelations grows as the flow develops downstream along the step. Additionally, adverse pressure gradient (APG) elevates the size of the autocorrelations.

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References

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Figures

Grahic Jump Location
Fig. 1

Schematic of (a) the mean flow features over a forward facing step and (b) a sectional side view of the test section and approximate locations of the measurement plane

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Fig. 2

Profiles of streamwise mean velocities U/Um at selected locations, where Um is the local maximum velocity. All symbols are as in (a).

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Fig. 3

Isocontour plots of streamwise autocorrelation function (Ruu) at x = 5h for APG-0 ((a), (c), and (e)) and APG-4 ((b), (d), and (f)). Note that lengths are normalized using the step height (h) and denoted by the superscript (*).

Grahic Jump Location
Fig. 4

Isocontour plots of streamwise autocorrelation function (Ruu) at x = 61h for APG-0 ((a), (c), and (e)) and APG-4 ((b), (d), and (f)). Note that lengths are normalized using the step height (h) and denoted by the superscript (*).

Grahic Jump Location
Fig. 5

Streamwise size, Lxuu* ((a) and (b)) and wall-normal size Lyuu* ((c) and (d)) of the streamwise autocorrelation function Ruu at selected locations for APG-0 ((a) and (c)) and APG-4 ((b) and (d)). Note that lengths are normalized using the step height (h) and denoted by the superscript (*). Also, the legend for APG-4 is not displayed but is the same as that for APG-0.

Grahic Jump Location
Fig. 6

Streamwise size, Lxvv* ((a) and (b)) and wall-normal size Lyvv* ((c) and (d)) of the wall-normal autocorrelation function Rvv at selected locations for APG-0 ((a) and (c)) and APG-4 ((b) and (d)). Note that lengths are normalized using the step height (h) and denoted by the superscript (*). Also, the legend for APG-4 is not displayed but is the same as that for APG-0.

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