Investigations of Flow Phenomena Over a Flat Plate and NACA0012 Airfoil at High Angles of Attack
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RESEARCH PAPER
Investigations of Flow Phenomena Over a Flat Plate and NACA0012 Airfoil at High Angles of Attack Shailesh Kr Jha1 · Uddipta Gautam1 · Pramod Pawar1 · S. Narayanan1 · L. A. Kumaraswamidhas1,2 Received: 31 October 2018 / Accepted: 30 August 2019 © Shiraz University 2019
Abstract In the present study, the flow and aerodynamic features of a sharp trailing edged flat plate airfoil are systematically compared with NACA0012 airfoil. The studies are conducted for three different Reynolds numbers 1.89 × 105, 2.83 × 105 and 3.78 × 105 and angles of attack 20°, 25° and 30°. The present study shows that the occurrence of vortex shedding phenomena for the flat plate is substantially different from NACA0012 airfoil. Further, the re-attachment location of the shed vortices is closer to the trailing edge for the flat plate, whereas for NACA0012 airfoil it occurs at a certain distance upstream of the trailing edge. The NACA0012 airfoil generates higher lift coefficients at a higher Reynolds numbers of 2.83 × 105 and 3.78 × 105, whereas for the flat plate it occurs at a lower Reynolds number of 1.89 × 105. The spectra of lift coefficient reveal that the amplitude of the primary shedding frequency dominates for the flat plate and NACA0012 airfoil at lower and higher Reynolds numbers of 1.89 × 105 and 3.78 × 105, respectively, while it becomes almost same for an intermediate Reynolds number of 2.83 × 105. The present study reveals that the drag coefficient at high Reynolds number (3.78 × 105) is directly proportional to the initial merging point of the two shed vortices for both the flat plate and NACA0012 airfoil. Keywords NACA0012 airfoil · Flat plate · Sharp trailing edge · Lift/drag coefficients List of Symbols c Chord length of the foil (m) cd Coefficient of drag cl Coefficient of lift cp Coefficient of pressure f Frequency (Hz) p Pressure (Pascal) Re Reynolds number (ρUc/µ) St Strouhal number (fc/U) U Free stream velocity (m/s) α Angle of attack (AOA) (°)
* S. Narayanan [email protected]; [email protected] 1
Department of Mechanical Engineering, Indian Institute of Technology (ISM), Dhanbad, Jharkhand 826004, India
Department of Mining Machinery Engineering, Indian Institute of Technology (ISM), Dhanbad 826004, India
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1 Introduction The airfoils find immense applications in marine engineering, aircrafts wings, fans, wind turbines blades, propellers, UAV (unmanned aerial vehicle), MAV (micro aerial vehicle), etc. and are highly demanding field of study in the present time. The aerodynamic performance of the foil can be easily augmented by simply changing its profile according to the application. It comprises consideration of lift/drag characteristics, shedding phenomena, stall characteristics, etc. The flow past foils at high angles of attack include several complex phenomena such as vortex formation and shedding, flow separation and lift/drag fluctuations in post-stall conditions. Researchers have been investigating the above-mentioned phenomena for the last several decades in fla
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