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Projecte llegit

Títol: Active flow control on cambered airfoils at ultralow Reynolds using synthetic jets

Estudiants que han llegit aquest projecte:

Director/a: MELLIBOVSKY ELSTEIN, FERNANDO PABLO

Departament: FIS

Títol: Active flow control on cambered airfoils at ultralow Reynolds using synthetic jets

Data inici oferta: 06-02-2017     Data finalització oferta: 06-10-2017


Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
Active flow control, Pulsating/Sweeping jet, Direct Navier Stokes, Airfoil.
 
Descripció del contingut i pla d'activitats:
Boundary layer separation results in poor aerodynamic performance of wings at high angles of attack. Active flow control aims at delaying (or even suppressing) separation. This can be achieved by employing periodic perturbation with pulsating jets generated with fluidic oscillators. This project will analyse the effects of synthetic jets on the aerodynamic performance of cambered airfoils at the ultralow Reynolds number regime.

The work plan will consist of the following activities

1) Literature review on boundary layer separation, airfoil performances at ultra low Reynolds number and active flow control with synthetic jets.

2) Choice of a Reynolds regime and angle of attack with well documented uncontrolled performances. Meshing, spectral-elements computation setup and convergence analysis for domain and mesh optimisation.

3) 2D airfoil baseline simulation for collection of vortex-shedding statistics.

4) Parametric analyisis of 2D synthetic jet actuation varying jet location, frequency and amplitude.

5) 3D baseline simulation for performance assessment.

6) Implementation of the 2D optimal control strategy on the 3D configuration.

7) Conclusions.
 
Overview (resum en anglès):

Active flow control methods have been widely studied for more than a decade in order to improve the airfoil's efficiency. This study is focused on fluidic actuation (the addition or subtraction of momentum to/from the boundary layer by blowing and/or sucking fluid). A synthetic jet is a very particular type of fluidic actuation that involves periodic blowing and suction with zero-net-mass-flow over a the full period. Its success as an active flow control device has been extensively reported by several authors. As it can be seen synthetic jet technology provides good results on boundary layer reattachment and therefore, an improvement on the airfoil's efficiency. What is more, is a generic system that can be widespread on multiple types of airfoils such as unmanned aerial vehicles and conventional airplanes airfoils. The effectiveness of control in mitigating boundary separation depends on a number of parameters related both to the flow itself and the control input such as: frequency and amplitude of the excitation, the excitation shape, exit diameter and cavity shape. Since the synthetic jet system has several degrees of freedom and the flux is unpredictable, multiple simulations have to be done in order to assess the best configuration to achieve the maximum airfoil’s efficiency. The well-known excitation of the synthetic jet is the zero-net-mass-flow that combines both expulsion and suction periodically. In this study, we also evaluate other types of excitations that imply more or less energy into the system that is characterized with the momentum coefficient. The goal is to assess thoroughly this existent trade-off between the aerodynamics performance and the momentum coefficient. And finally, extract deep conclusions and assess the best synthetic jet configuration where the aerodynamics performances are improved with a low momentum coefficient.. To extract suitably conclusions we pass through a thorough and intricate process that starts with the adapted and generic discretized surface for the synthetic jet that we use to solve the Navier-Stokes equations, then the appropriate conversions to simulate with spectral element framework Nektar++ and finally the detailed extraction of results. Moreover, we adopt to this study a practical approach with an unmanned aerial vehicle (UAV Skywalker x6) airfoil’s photogrammetry that we use to simulate.

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