CBL - Campus del Baix Llobregat

Projecte llegit

Títol: The unstable vortex-shedding regime of NACA 0012 airfoil with hysteretical stall

Estudiants que han llegit aquest projecte:

Director/a: MELLIBOVSKY ELSTEIN, FERNANDO PABLO

Departament: FIS

Títol: The unstable vortex-shedding regime of NACA 0012 airfoil with hysteretical stall

Data inici oferta: 21-07-2025     Data finalització oferta: 21-03-2026


Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
Aerodynamic hysteresis, Stall, NACA 0012, Computational Fluid Dynamics (CFD), NekRS, Vortex shedding, Edge tracking, Flow separation, Reynolds number
 
Descripció del contingut i pla d'activitats:
 
Overview (resum en anglès):
Aerodynamic hysteresis is a phenomenon in which an airfoil subjected to increasing and decreasing angles of attack reaches different aerodynamic states under identical operating conditions. This behaviour is associated with flow separation, wake dynamics and aerodynamic stall. The aim of this work is to investigate the hysteresis behaviour of a NACA 0012 airfoil at a Reynolds number of one million through numerical simulations performed with the high-order spectral-element solver NekRS.
The numerical methodology was first validated through mesh, domain and numerical-parameter sensitivity studies. Once the numerical setup was established, increasing and decreasing angle-of-attack sequences were simulated to identify the existence of multiple stable solutions. The flow was analysed using aerodynamic coefficients, skin-friction and pressure distributions, velocity and vorticity fields, frequency analysis of the lift coefficient, and an edge-tracking technique to investigate the basin boundary separating the different flow states.
The simulations reveal a hysteresis loop between an angle of attack of 16º and 20º. The two solution branches are characterised by different separation locations, wake organisations and vortex-shedding behaviour despite having the same angle of attack. The stall-onset analysis suggests that the transition is initiated by an instability developing in the wake, which propagates upstream and eventually triggers leading-edge separation. Edge tracking identifies an intermediate vortex-shedding state on the basin boundary and reveals an extreme sensitivity to the initial condition, suggesting a potentially fractal basin boundary. Finally, additional simulations demonstrate that different initial phases of the same unsteady solution may converge to different final aerodynamic states, highlighting the sensitivity of the hysteresis process to the flow history and suggesting the possible existence of multiple stable solutions.

© CBLTIC Campus del Baix Llobregat - UPC