Wake/shear layer interaction for low-Reynolds-number flow over multi-element airfoil
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Time-resolved particle image velocimetry (TR-PIV) and hydrogen bubble visualization are employed to study the effects of Reynolds number on the wake/shear layer interactions over multi-element airfoil (30P30N). The Reynolds number based on the stowed chord length (Rec) ranges from 9.3 × 103 to 3.05 × 104. According to the variation of dominated flow structures, a critical Rec interval from 1.27 × 104 to 1.38 × 104 is found, which is novel for the low-Reynolds-number flow over multi-element airfoil. The slat wakes can be divided into two types by this critical interval. When Rec is smaller than this critical interval, no roll-up occurs to the shear layer of slat cusp. Görtler vortices generated by a virtual curved wall dominate the slat wake. When Rec is larger than this critical interval, roll-ups occur to the shear layer of slat cusp, which is similar to the cases at high Reynolds number (Rec ~ 106). These roll-ups and their evolution result in the co-existence of spanwise vortices and streamwise vortices in the slat wake. Different kinds of slat wake result in different kinds of wake/shear layer interactions above the main element. The flow physics behind these complex interactions, especially the novel flow structures and their evolution, is analyzed in detail to contribute to the fundamental research of wake/shear layer interactions. When Görtler vortices dominate the slat wake, they could trigger streaky structures within the leading-edge separated shear layer of the main element. When spanwise vortices and streamwise vortices co-exist in the slat wake, novel spanwise “double secondary vortices” are triggered above the main element by the spanwise vortices of slat cusp shear layer.
This work is supported by the National Natural Science Foundation of China (11761131009, 11721202).
- Carmichael B (1981) Low Reynolds number airfoil survey, vol 1. NASA Technical Report, NASA-CR- 165803Google Scholar
- Choudhari M, Lockard DP Assessment of slat noise predictions for 30P30N high-lift configuration from BANC-III workshop. In: 21st AIAA/CEAS aeroacoustics conference (2015) p 2844Google Scholar
- Choudhari MM, Yamamoto K (2012) Integrating CFD, CAA, and experiments towards benchmark datasets for airframe noise problems, NASA Conference Paper NF-1676L-14832Google Scholar
- Gaster M (1969) The structure and behaviour of laminar separation bubbles. H.M. Stationery Office, pp 1–31Google Scholar
- Haines A (1994) Scale Effects on Aircraft and Weapon Aerodynamics (Les Effets d’Echelle et l’Aerodynamique des Aeronefs et des Systemes d’Armes). DTIC DocumentGoogle Scholar
- Hansen H, Thiede P, Moens F, Rudnik R, Quest J (2004) Overview about the European high lift research programme EUROLIFT AIAA Paper 767:2004Google Scholar
- Jenkins LN, Khorrami MR, Choudhari M (2004) Characterization of unsteady flow structures near leading-edge slat: Part I. PIV measurements AIAA paper 2801:2004Google Scholar
- Ma L, Feng L, Pan C, Gao Q, Wang J (2015) Fourier mode decomposition of PIV data Science, China. Technol Sci 58:1935–1948Google Scholar
- Paschal K, Jenkins L, Yao C (2000) Unsteady slat-wake characteristics of a high-lift configuration. AIAA paper 139:2000Google Scholar
- Pascioni KA, Cattafesta LN, Choudhari MM (2014) An Experimental investigation of the 30P30N multi-element high-lift airfoil. 20th AIAA/CEAS Aeroacoustics Conference, Atlanta, Georgia, 16–20 June 2014Google Scholar
- Winslow J, Otsuka H, Govindarajan B, Chopra I (2017) Basic Understanding of airfoil characteristics at low Reynolds numbers (10 4–10 5) J Aircr 55:1–12Google Scholar