Numerical Analysis of Transition in Laminar Flow around a Pithing Airfoil

Articles in Press

Document Type : Original Article

Authors

• Hossein Ansarian ¹
• َAlireza Davari ²

¹ Malek Ashtar University of Technology, Tehran

² Department of Engineering, Science and Research Branch, Islamic Azad University, Tehran

10.22067/jacsm.2024.87292.1246

Abstract

The dynamic response of a natural laminar flow airfoil undergoing harmonic small-amplitude pitching oscillations is investigated using Large-eddy simulations with a chord-based Reynolds number of Re = 750;000. Throughout the pitch cycles, large changes in the transition point are seen as well as trailing-edge separation. This leads to a nonlinear response of the aerodynamic forces. Although the nature of the flow is highly nonlinear, the development of the boundary layer over the airfoil surface can be modeled using a simple phase-lag concept which suggests a quasi-steady evolution of the boundary layer. Based on this phase-lag assumption, a simple new empirical model is developed which agrees very well with the measured experimental data. With the aid of this model, the primary source of non-linearities in the unsteady aerodynamic forces is identified to be the quasi-steady term, which can be evaluated from the static airfoil characteristics. The strength of this remains unchanged with the variation of reduced frequency, but the harmonic term's strength, which models the unsteady effects, increases with increasing frequency.

Keywords

• laminar flow
• large eddy simulation
• pitching oscillation
• unsteady response

Main Subjects

• Aerodynamics

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