Effect of wing mass in free flight of a two-dimensional symmetric flapping wing–body model. (11th August 2017)

• Record Type: Journal Article
• Authors: Suzuki, Kosuke; Aoki, Takaaki; Yoshino, Masato
• Is Part Of: Fluid dynamics research. Volume 49:Number 5(2017:Oct.)
• Publication Date: 2017-08-11
• Subjects: flapping flight -- wing mass -- lattice Boltzmann method -- immersed boundary method; Fluid dynamics -- Periodicals; 620.106
• DOI: 10.1088/1873-7005/aa7a9a
• Languages: English
• ISSNs: 0169-5983

Abstract

Abstract: The effect of wing mass in the free flight of a flapping wing is investigated by numerical simulations based on an immersed boundary–lattice Boltzmann method. We consider a model consisting of two-dimensional symmetric flapping wings with uniform mass density connected by a body represented as a point mass. We simulate free flights of the two-dimensional symmetric flapping wing with various mass ratios of the wings to the body. In free flights without gravity, it is found that the time-averaged lift force becomes smaller as the mass ratio increases, since with a large mass ratio the body experiences a large vertical oscillation in one period and consequently the wing-tip speed relatively decreases. We define the effective Reynolds number Re eff taking the body motion into consideration and investigate the critical value of Re eff over which the symmetry breaking of flows occurs. As a result, it is found that the critical value is Re eff ≃ 70 independently of the mass ratio. In free flights with gravity, the time-averaged lift force becomes smaller as the mass ratio increases in the same way as free flights without gravity. In addition, the unstable rotational motion around the body is suppressed as the mass ratio increases, since with a large mass ratio the vortices shedding from the wing tip are small and easily decay.