Non-modal stability analysis of low-Re separated flow around a NACA 4415 airfoil in ground effect

He, Wei1,3; Miguel Perez, Jose2; Yu, Peng3; Li, Larry K. B.1

2019-09

10.1016/j.ast.2019.06.007

AEROSPACE SCIENCE AND TECHNOLOGY   影响因子和分区

1270-9638

1626-3219

In this numerical-theoretical study, we perform a linear non-modal stability analysis of the separated flow around a NACA 4415 airfoil over a no-slip ground at low Reynolds numbers (300 <= Re <= 500) and high angles of attack (12 degrees <= alpha <= 20 degrees). We find that: (i) the strength of the recirculation zone behind the airfoil is a key parameter controlling the absolute/convective nature of the instability in the boundary layer downstream; (ii) when Re, alpha or the ground clearance increases, the energy gain also increases, with the optimal perturbations switching from being three dimensional to two dimensional; and (iii) classical hairpin vortices, or Klebanoff modes, can be produced by three-dimensional optimal perturbations on a two-dimensional steady base flow containing a laminar separation bubble. Knowledge of the spatiotemporal features of the optimal mode could aid the design of advanced strategies for flow control. This study offers new insight into the transient growth behavior of airfoil-ground flow systems at low Re and high alpha, contributing to a better understanding of the ground-effect aerodynamics of small insects and micro aerial vehicles. (C) 2019 Elsevier Masson SAS. All rights reserved.

Transient growth Non-modal stability Ground effect Low Reynolds number

SCI ; EI

英语

通讯

Research Grants Council of Hong Kong[16235716] ; Research Grants Council of Hong Kong[26202815]

Engineering

Engineering, Aerospace

WOS:000485852600024

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

20192407046688

Airfoils ; Angle of attack ; Antennas ; Ground effect ; Laminar boundary layer ; Laminar flow ; Micro air vehicle (MAV) ; Reynolds equation ; Reynolds number ; Stability

Fluid Flow, General:631.1 ; Aerodynamics, General:651.1 ; Aircraft, General:652.1

ENGINEERING

Web of Science

1.Hong Kong Univ Sci & Technol, Clear Water Bay, Hong Kong, Peoples R China
2.Univ Politecn Madrid, Madrid, Spain
3.Southern Univ Sci & Technol, Shenzhen, Peoples R China

He, Wei,Miguel Perez, Jose,Yu, Peng,et al. Non-modal stability analysis of low-Re separated flow around a NACA 4415 airfoil in ground effect[J]. AEROSPACE SCIENCE AND TECHNOLOGY,2019,92:269-279.

He, Wei,Miguel Perez, Jose,Yu, Peng,&Li, Larry K. B..(2019).Non-modal stability analysis of low-Re separated flow around a NACA 4415 airfoil in ground effect.AEROSPACE SCIENCE AND TECHNOLOGY,92,269-279.

He, Wei,et al."Non-modal stability analysis of low-Re separated flow around a NACA 4415 airfoil in ground effect".AEROSPACE SCIENCE AND TECHNOLOGY 92(2019):269-279.