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Projecte llegit

Títol: Application of Active Flow Control on airfoils at ultralow Reynolds numbers

Estudiants que han llegit aquest projecte:

Director/a: MELLIBOVSKY ELSTEIN, FERNANDO PABLO

Departament: FIS

Títol: Application of Active Flow Control on airfoils at ultralow Reynolds numbers

Data inici oferta: 28-02-2019     Data finalització oferta: 31-10-2019


Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
active flow control, airfoil, aerodynamics, numerical
 
Descripció del contingut i pla d'activitats:
Previous research has shown that momentum injection to the boundary layer in the form of a periodic excitation can prevent or retard flow detachment as well as reattach an already separated flow. Two main techniques have been studied, sweeping jets that are based on steady and unsteady blowing and zero-net-mass-flux actuators called synthetic jets. Both types of fluidic actuators have provided interesting results in terms of lift enhancement but the high velocities induced near the wall results also in large skin-friction drag increase.

In this study we start from ongoing research with the aim of optimising and thus improving the aerodynamic efficiency of this type of fluidic actuation. First we will assess the dependence of skin-friction drag on the various parameters that determine the actuator momentum coefficient in order to isolate the most important factors. Then we will try different configurations and shapes of fluidic actuators, in particular synthetic jets and sweeping jets, with the objective of reducing momentum coefficient as well as total and viscous drag while keeping lift enhancement. Finally a 3D study will be performed in order to verify the effectiveness of these actuations in a realistic environment.

The work plan is as follows:

0) Information and documentation research on AFC actuations.
1) Theoretical base and assumptions of the study.
2) Geometry and 2D mesh generation for different fluidic actuators.
3) Simulation and analysis of different sweeping jets and synthetic jets configurations.
4) Extrapolation of best results into a 3D environment.
 
Overview (resum en anglès):

In a previous research Active Flow Control techniques, such as sweeping jets, applied in an ultra-low Reynolds regime (Re=1000) were found effective to reattach an already separated flow achieving lift enhancements but also inducing a large skin-friction drag increase due to the high velocities near the airfoil surface. In this study, firstly the current actuator configurations have been analyzed with the objective of determining the most important factors involved in the increase of the viscous drag. Then, several hypothesis have been done with the aim of reducing this drag penalty while keeping the lift enhancement. The decision taken in this sense has been to apply geometrical modifications to the the actuators using two control parameters, the jet width and the jet angle in which the fluid is injected. Moreover these modifications have been applied to three different actuation types; blowing, suction and synthetic jets. The simulations have been carried in a 2D NACA0012 airfoil in which a remeshing has been done in order to apply the commented modifications. The obtained results show variations depending on in which actuation type are applied. The jet angle modification has obtained interesting results for the blowing jet, since an angle that maximizes the lift coefficient has been found. The jet width has also obtained an optimum value for a specific momentum coefficient, that moreover is suitable for the three actuations. In conclusion, it has been proved that that besides the momentum coefficient and the jet location the geometrical parameters of the actuator have also a considerable impact on the overall efficiency of the actuation.

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