The evolution of a separated boundary layer over a model airfoil with semicircular leading-edge has been illustrated for angles of attack (α) varying from −3 deg to 10 deg, where the Reynolds number (Rec) based on chord is 1.6 × 105 and the inlet freestream turbulence (fst) being 1.2%. The features of boundary layer are described through measurements of velocity and surface pressure besides the flow visualization using a planar particle image velocimetry (PIV). Freestream perturbations are amplified because of enhanced receptivity of the separated boundary layer resulting in pockets of disturbances, which then propagate downstream attributing to random fluctuations near the reattachment. The separation and reattachment locations including the onset and end of transition are identified for changing α. The reattachment point changes from 18.8% to 47.7% of chord with the onset of separation at almost 7%, whereas the onset of transition moves upstream from 13.2% to 9% with increasing α. The bubble bursting occurs at α = 10 deg. The transition in the separated boundary layer occurs through Kelvin–Helmholtz (K–H) instability for α = 0 deg and 3 deg, whereas the K–H mechanism is bypassed for higher α with significant viscous effect.
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February 2017
Research-Article
Features of a Laminar Separated Boundary Layer Near the Leading-Edge of a Model Airfoil for Different Angles of Attack: An Experimental Study
K. Anand,
K. Anand
Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
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S. Sarkar
S. Sarkar
Professor
Mem. ASME
Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
e-mail: subra@iitk.ac.in
Mem. ASME
Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
e-mail: subra@iitk.ac.in
Search for other works by this author on:
K. Anand
Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
S. Sarkar
Professor
Mem. ASME
Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
e-mail: subra@iitk.ac.in
Mem. ASME
Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, Uttar Pradesh 208016, India
e-mail: subra@iitk.ac.in
1Present address: Department of Mechanical Engineering, SASTRA University, Thanjavur, Tamilnadu 613 401, India.
2Corresponding author.
Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received October 7, 2015; final manuscript received August 26, 2016; published online November 3, 2016. Editor: Malcolm J. Andrews.
J. Fluids Eng. Feb 2017, 139(2): 021201 (14 pages)
Published Online: November 3, 2016
Article history
Received:
October 7, 2015
Revised:
August 26, 2016
Citation
Anand, K., and Sarkar, S. (November 3, 2016). "Features of a Laminar Separated Boundary Layer Near the Leading-Edge of a Model Airfoil for Different Angles of Attack: An Experimental Study." ASME. J. Fluids Eng. February 2017; 139(2): 021201. https://doi.org/10.1115/1.4034606
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