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Research Papers: Fundamental Issues and Canonical Flows

Near Field Development of Planar Wakes Under the Effect of Asymmetric Initial Conditions

[+] Author and Article Information
Ladan Momayez

Department of Mechanical and
Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON K7K 7B4, Canada
e-mails: ladan.momayez@gmail.com;
ladan.momayez@rmc.ca

Marouen Dghim

Department of Mechanical and
Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON K7K 7B4, Canada;
University of Sherbrooke
Sherbrooke, QC J1K 2R1, Canada
e-mails: Marouen.Dghim@USherbrooke.ca;
marouen.dghim@rmc.ca

Mohsen Ferchichi

Associate Professor
Department of Mechanical and
Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON K7K 7B4, Canada
e-mail: mohsen.ferchichi@rmc.ca

Sylvain Graveline

Assistant Professor
Department of Mechanical and
Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON K7K 7B4, Canada
e-mail: sylvain.graveline@rmc.ca

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received September 17, 2014; final manuscript received March 17, 2015; published online May 19, 2015. Assoc. Editor: Mark F. Tachie.

J. Fluids Eng 137(9), 091201 (May 19, 2015) (8 pages) Paper No: FE-14-1518; doi: 10.1115/1.4030342 History: Received September 17, 2014

This paper reports an experimental investigation on the response of a planar wake past a flat plate to various upstream flow conditions. A tripping wire was placed on the upper side of the flat plate downstream the leading edge which resulted in asymmetric boundary layers. The near wake asymmetry was compared to their symmetrical counterpart at two different Reynolds numbers. The near wake dynamics were investigated using hotwire anemometry and flow visualizations. Self-similarity of the asymmetrical wakes was established. Asymmetry seemed to have the largest effect on the convection velocity of the large structures in the asymmetric laminar-turbulent wake.

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Figures

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Fig. 1

Experimental setup

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Fig. 2

Mean velocity profiles at x/c = 0.98 on the upper surface of the flat plate

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Fig. 3

Turbulence intensity profiles at x/c = 0.98 on the upper surface of the flat plate

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Fig. 4

Velocity field in the SL wake in self similar coordinates. (a) Mean streamwise velocity profiles and (b) normalized streamwise turbulence intensity profiles.

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Fig. 5

Streamwise variation of the normalized wake width for the different cases studied

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Fig. 6

Velocity field in the ST wake in self similar coordinates. (a) Mean streamwise velocity profiles and (b) normalized streamwise turbulence intensity profiles.

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Fig. 7

Transverse locations of + y50% (upper side) and –y50% (lower side) at each downstream position for all cases studied

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Fig. 8

Velocity field in the ALT wake in self similar coordinates. (a) Mean streamwise velocity profiles and (b) normalized streamwise turbulence intensity profiles.

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Fig. 9

Velocity field in the ATT wake in self similar coordinates. (a) Mean streamwise velocity profiles and (b) normalized streamwise turbulence intensity profiles.

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Fig. 10

Smoke flow visualization of von Kármán vortex street. (a) SL case and (b) ST case.

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Fig. 11

Smoke flow visualization of von Kármán vortex street. (a) ALT case and (b) ATT case.

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Fig. 12

Variation of the maximum streamwise fluctuations along the wake centerline

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Fig. 13

Convection velocity of the large structure in the SL and ALT wakes

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Fig. 14

Convection velocity of the large structure in the ST and ATT wakes

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Fig. 15

Spectra of the streamwise velocity fluctuations for the SL and ALT cases (spectra of the ALT case were shifted up by one decade)

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Fig. 16

Spectra of the streamwise velocity fluctuations for the ST and ATT cases (spectra of the ATT case were shifted up by one decade)

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