Simulation des grandes échelles du processus de décrochage par éclatement de bulbe de décollement laminaire

Abstract : High fidelity numerical simulation is used to study the transitory flow involved during the staIl ofan airfoil at high angle of attack. The nearly DNS resolution in the Laminar Separation Bubbleprovides the required accuracy to reproduce this complex flow that still represents a challenge forboth experimentation and modeling. The numerical procedure is comprehensively validated withparticular attention to the LSB region. The sensitivity of the LSB to an external disturbance ismonitored on the airfoil and is favorably compared with a recent study on flat plate in the literature.The destabilization of the LSB during staIl is reproduced with a small variation of the angle ofattack through the critical angle. The LSB bursting, typical of a static leading edge staIl, is thusreproduced. A comprehensive study of the unsteady events during the transitory flow is performedby means of a high frequency sampling of spanwise and short time averaged data base. Ofparticular interest is the 3D deformation of the flow captured by using a large spanwisecomputational domain (one chord length). The influence of the motion dynamic is then explored.The transitory is significantly affected by a high angular amplitude motion. The shear-Iayer in theLSB undergoes a roll-up which is found to be responsible for the formation of the Leading EdgeVortex, typical of a dynamic staIl configuration. An empirical criterion for the prediction of burstingis then assessed using the statistical data base. Results are found to surprisingly match the incipientof staIl in both static and dynamicaJ conditions.
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Nicolas Alferez. Simulation des grandes échelles du processus de décrochage par éclatement de bulbe de décollement laminaire. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2014. Français. ⟨NNT : 2014ESMA0004⟩. ⟨tel-01011273⟩

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