Investigation of the load reduction potential of two trailing edge flap controls using CFD

Abstract

In this work, a 2D aero-servo-elastic model of an airfoil section with 3 degrees of freedom (DOF) based on the 2D CFD solver EllipSys2D to calculate the aerodynamic forces is utilized to calculate the load reduction potential of an airfoil equipped with an adaptive trailing edge fl ap (ATEF) and subjected to a turbulent infl ow signal.The employed airfoil model corresponds to a successfully tested prototype airfoil where piezoelectric actuators were used for the fl apping. In the present investigation two possible control methods for the fl ap are compared in their ability to reduce the fl uctuating normal forces on the airfoil due to a 4 s turbulent infl ow signal and the best location of the measurement point for the respective control input is determined. While Control 1 uses the measurements of a Pitot tube mounted in front of the leading edge (LE) as input, Control 2 uses the pressure difference between the pressure and suction side of the airfoil measured at a certain chord position.Control 1 achieves its maximum load reduction of R Std(F y ) = 76.7% for the shortest Pitot tube of the test, i.e. a Pitot tube with a length of 0.05% of the chord length. Control 2 shows the highest load reduction of R Std(F y ) = 77.7% when the pressure difference is measured at a chord position of approximately 15%.

Aerodynamic response of an airfoil section undergoing pitch motion and trailing edge flap deflection: a comparison of simulation methods

“…24 A comparison of EllipSys 2D results against measurements performed on the National Renewable Energy Laboratory Phase-VI rotor for harmonic pitching motion is reported by Sørensen and Schreck 25 The motion of the airfoil is simulated by moving the computational grid and accounting for the additional fluxes that are generated as the grid cells vertices are displaced. The flap deflection is modeled through a grid morphing routine, 11 where the position of the grid points for an arbitrary flap deflection are determined by linear interpolation of the two meshes generated with the flap at maximum upwards and downwards deflection (˙5 ı in this study); the additional fluxes caused by the displacement of the cell vertices are also accounted for.…”

“…The paper considers three state-of-the-art methods to simulate the integral aerodynamic forces and moment coefficients of a 2D airfoil section undergoing pitching motion and trailing edge flap deflections. The methods are, in decreasing order of computational requirements: EllipSys 2D, the Reynolds-averaged Navier-Stokes (RANS) solver developed at DTU Wind Energy; 11 the National Technical University of Athens (NTUA) viscous-inviscid interaction method; 18 ATEFlap, a dynamic stall engineering model. 19 The aim is to characterize the unsteady aerodynamic response of the airfoil to changes in the AOA or the flap deflection and to compare the responses simulated by the three methods.…”

An Experimental Study of Mini-Tabs for Aerodynamic Load Control

“…These load cases are typically the most extreme, dictating the size of the structure and thus weight, even though they are rare occurences. Current actuation strategies, such as flaps and ailerons, aim to mitigate these loads at the fluid-structure interface however they are extremely limited in their frequency response due to their large inertia even though evidence 1,2 suggests that high frequency is key to an actuator's ability to effectively mitigate aerodynamic loads. Current and incoming legislation through ACARE Vision 2020 dictates that aircraft emissions must be reduced, applying pressure to reduce actuator and airframe structural weight in the coming years.…”

Self‐induced vibrations of a DU96‐W‐180 airfoil in stall

“…The EllipSys add‐on for 2D structural elastically mounted airfoil computations was developed by Heinz . The structural model was coupled with both 2D and 3D CFD computations.…”