FLAPPING THIN AIRFOIL INTERACTING WITH THE GROUND

Incompressible flow through an unstaggered cascade in general, unsteady, in-phase motion is considered. By methods of thin-airfoil theory, using the assumptions of wakes trailing back at the through-flow velocity, and the Kutta condition, exact analytical expressions are derived for loading, lift and moment. As application, harmonic motion is considered for plunging, pitching, and sinusoidal gusts. Numerical values of lift and moment for these three cases are given graphically (tables are available from the authors). The results show strong analogies with isolated unsteady thin-airfoil theory. They should prove useful as simple examples of unsteady effects in cascades, and as check cases for other approximate or purely numerical analyses.

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A Physically Consistent Reduced Order Model for Plasma Aeroelastic Control on Compressor Blades

Volume 7C: Structures and Dynamics ◽

10.1115/gt2018-75080 ◽

2018 ◽

Cited By ~ 1

Author(s):

Valentina Motta ◽

Leonie Malzacher ◽

Dieter Peitsch ◽

Giuseppe Quaranta

Keyword(s):

Suction Side ◽

Reduced Order Model ◽

Plasma Actuators ◽

Pitching Moment ◽

Compressor Cascade ◽

Order Model ◽

Compressor Blades ◽

Reduced Order ◽

Thin Airfoil ◽

Pressure Suction

Plasma actuators may be successfully employed as virtual control surfaces, located at the trailing edge of blades, both on the pressure and on the suction side, to control the aeroelastic response of a compressor cascade. Actuators generate an induced flow against the direction of the freestream. As a result, actuating on the pressure side yields an increase in lift and nose down pitching moment, whereas the opposite is obtained by operating on the suction side. A properly phased alternate pressure/suction side actuation allows to reduce vibration and to delay the flutter onset. This paper presents the development of a linear frequency domain reduced order model for lift and pitching moment of the plasma-equipped cascade. Specifically, an equivalent thin airfoil model is used as a physically consistent basis for the model. Modifications in the geometry of the thin airfoil are generated to account for the effective chord and camber changes induced by the plasma actuators, as well as for the effects of the neighboring blades. The model reproduces and predicts correctly the mean and the unsteady loads, along with the aerodynamic damping on the plasma equipped cascade. The relationship between the parameters of the reduced order model with the flow physics is highlighted.

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