Abstract
This study demonstrates an active flow control for deflecting a direction of wake vortex structures behind a NACA0012 airfoil using an active morphing flap. Two-dimensional direct numerical simulations are performed for flows at the chord Reynolds number of 10,000, and the vortex pattern in the controlled and noncontrolled wakes as well as the effect of an actuation frequency on the control ability are rigorously investigated. It is found that there is an optimum actuation-frequency regime at around F + = 2.00 which is normalized by the chord length and freestream velocity. The wake vortex pattern of the well-controlled case is classified as the 2P wake pattern according to the Williamson’s categorization [1] [2], where the forced oscillation frequency corresponds to the natural vortex shedding frequency without control. The present classification of wake vortex patterns and finding of the optimum frequency regime in the wake deflection control can lead to a more robust design suitable for vortex-induced-vibration (VIV) related engineering systems.
Highlights
When a body is placed in the vortex-dominated flows such as wakes of cylinders or airfoils at a nonzero angle of attack (AoA), the body experiences a fluctuating lift force and vibrates due to the unsteady vortex motion interacting with the body itself, which is known as a vortex-induced vibration (VIV) and regarded as an important problem ranging from a design of civil engineering structures to a flutter constraint of aircraft wing designs [3] [4] [5] [6]
The results show that the targeted low-AoA (5 deg) flow condition can be accurately computed; the 3D simulation corresponds to the 2D simulation results, which indicates that the present flow is mostly dominated by 2D flow motion and the 2D simulation is sufficient to capture the flow physics
The present vortex pair is so-called the “P” mode (Figure 3(b) in [1]), which is fed into the downstream direction and forms the wake structure aligned in the freestream direction (AoA = 5 deg.)
Summary
When a body is placed in the vortex-dominated flows such as wakes of cylinders or airfoils at a nonzero angle of attack (AoA), the body experiences a fluctuating lift force and vibrates due to the unsteady vortex motion interacting with the body itself, which is known as a vortex-induced vibration (VIV) and regarded as an important problem ranging from a design of civil engineering structures to a flutter constraint of aircraft wing designs [3] [4] [5] [6]. The prediction of VIV and lock-in phenomena has been of practical interests and extensively studied, e.g., so called the Griffin plot [8] [9] for predicting maximum structural displacement and the other semi-empirical wake oscillator models [4] [5] [10]. These models have been kept improved [11] [12] and effectively used in the engineering design to avoid destruction of the system due to excessive VIV phenomena. It is expected that another new technology can be incorporated with those VIV prediction models so that a more robust engineering design is established for avoiding a VIV-related destruction
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