Propulsive performance of plunging airfoils in biplane configuration

Abstract

Biplane configuration of pure plunging airfoils is investigated in terms of vortex dynamics both experimentally and numerically by utilizing particle image velocimetry and unstructured finite volume solver of incompressible unsteady Navier–Stokes equations. Experiments are carried out to disclose the vortex shedding and interaction mechanisms for various values of frequency and amplitude of the plunging motion. For the non-dimensional plunge amplitude with respect to the chord of airfoil h = 0.2, the effect of the reduced circular frequency based on chord length and the free stream velocity k = 1 and 10 are considered, whereas for h = 0.3, k = 2, 4, 8, and 10 cases are examined. Influence of the plunge amplitude is studied for h = 0.25 at k = 2.5 and for h = 0.0875, 0.15, and 0.3 at k = 4. Numerical simulations are performed to investigate the effect of phase difference on vortex structures and propulsive characteristics, such as thrust and Froude efficiency. Two cases having the highest thrust and efficiency values k = 2.5, h = 0.25, and k = 4, h = 0.15 value couples are selected for the phase angle of [Formula: see text], and [Formula: see text]. Opposed plunge, [Formula: see text], was found as the most efficient amongst all phase angles that were investigated, where [Formula: see text] is beneficial in lift production. Additionally, three-dimensional simulations indicate no significant three dimensionalities for the parameters used herein.

Classification of vortex patterns of oscillating foils in side-by-side configurations

“…For smaller St and Re, single foils tend to show superior performance, whereas parallel foils outperform them for greater values of St and Re. For out-of-phase oscillations, previous studies agree that parallel foils produce considerably larger thrust at the cost of enhanced power requirement, which results in the nearly similar efficiency (Dewey et al 2014;Huera-Huarte 2018;Gungor & Hemmati 2021;Yucel et al 2022). Dewey et al (2014) qualitatively examined vortex patterns of in-phase, mid-phase and out-of-phase pitching foils in side-by-side configurations for a fixed separation distance and Strouhal number.…”

“…There is a consensus in the literature that parallel foils exhibit reduced thrust generation and power requirement compared with a single foil for in-phase oscillations (Dewey et al. 2014; Huera-Huarte 2018; Gungor & Hemmati 2021; Yucel, Sahin & Unal 2022). However, Dewey et al.…”

“…(2014) and Huera-Huarte (2018) estimated improved efficiency for parallel foils, whereas Yucel et al. (2022) found that the efficiency of a single foil was greater. Gungor & Hemmati (2021) conducted a comprehensive analysis and revealed that and had a strong impact on the efficiency of the system.…”

“…There is a consensus in the literature that parallel foils exhibit reduced thrust generation and power requirement compared with a single foil for in-phase oscillations (Dewey et al 2014;Huera-Huarte 2018;Gungor & Hemmati 2021;Yucel, Sahin & Unal 2022). However, Dewey et al (2014) and Huera-Huarte (2018) estimated improved efficiency for parallel foils, whereas Yucel et al (2022) found that the efficiency of a single foil was greater. Gungor & Hemmati (2021) conducted a comprehensive analysis and revealed that St and Re had a strong impact on the efficiency of the system.…”