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DIRECT NUMERICAL SIMULATION OF A LAMINAR SEPARATION BUBBLE ON A NACA-0012 AIRFOIL

Lloyd E. Jones
Aerodynamics and Flight Mechanics Research Group, School of Engineering Sciences Southampton, England

Richard D. Sandberg
Aerodynamics and Flight Mechanics Research Group, Faculty of Engineering and the Environment, University of Southampton Highfield, Southampton, SO17 1BJ, U.K.

Neil D. Sandham
Aerodynamics and Flight Mechanics Group Faculty of Engineering and the Environment, University of Southampton Southampton SO17 1BJ, UK

Abstrakt

Direct numerical simulations (DNS) of a laminar separation bubble on a NACA-0012 airfoil at Rec = 5 × 104 and incidence 5° are presented. Initially volume forcing is introduced in order to promote transition. After obtaining sufficient data from this forced case, the explicitly added disturbances are removed and the simulation run further. Upon removal of disturbances, the turbulence is observed to 'self-sustain', and does not decrease in intensity. The forced and unforced cases are then compared, in order to investigate the dependency of bubble behaviour on the addition of disturbances. The results imply that forcing may potentially be used as a control measure to improve aerodynamic performance. Finally, a simplified DNS is presented that illustrates a mechanism for the self-sustaining turbulence that is observed, with implications for separation bubble modelling.