Experimental and numerical investigations of unsteady aerodynamic derivatives for a generic lambda wing UCAV configuration

Abstract

Experimental and numerical investigations have been conducted to analyze the unsteady aerodynamic and flight mechanical behavior of a 53° flying wing configuration representing a generic unmanned combat air vehicle (UCAV). The considered vehicle is named SACCON/DLR-F17 and the here presented results have been collected within an internal project of the German Aerospace Center in collaboration with the NATO task group AVT-201 on “Extended Assessment of Reliable Stability & Control Prediction Methods for NATO Air Vehicles”. Both projects have the aim to conduct studies of an integrated approach to predict the stability and control characteristics for a generic UCAV configuration based on both experimental and numerical investigations. Systematic investigations have been performed to determine the dynamic derivatives for the longitudinal and lateral motion. A comparison between data of experimental wind tunnel investigations and numerical simulations under real flight conditions is given. In wind tunnel tests, performed in the DNW-NWB wind tunnel, the SACCON configuration was studied at a reduced scale of 1:8 and a Mach number of M = 0.15. Forced oscillation motions were performed during these tests to calculate the dynamic derivatives from force and moment data. For the numerical calculations, the same reduced frequencies were applied with the full-scale configuration under real flight conditions using the RANS method DLR-TAU. The planform aerodynamics is governed by complex non-linear flow phenomena due to leading edge vortex flow separation at moderate to high angles of attack. Based on the numerical results, an interpretation of the complex vortex flow is given to understand the unsteady flow phenomena for a variety of roll, pitch, and yawing motions.

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Abbreviations

b :

Span (m)

c ref :

Reference length (m)

f :

Oscillation frequency (Hz)

p :

Roll rate (°/s)

q :

Pitch rate (°/s)

r :

Yaw rate (°/s)

s :

Half span (m)

U :

Free stream velocity (m/s)

\(\alpha\) :

Angle of attack (°)

\(\dot{\alpha }\) :

Angular velocity of angle of attack (°/s)

\(\beta\) :

Angle of sideslip (°)

\(\dot{\beta }\) :

Angular velocity of angle of sideslip (°/s)

\(\omega\) :

Angular velocity (°/s)

\(\omega^{*}\) :

Reduced frequency (−) 2πf cref/U longitudinal motion 2πf s/U lateral motion

\(\varPhi\) :

Roll angle (°)

\(\Delta \varPhi\) :

Amplitude rolling oscillation

\(\varPsi\) :

Pitch angle (°)

\(\Delta \varPsi\) :

Amplitude pitching oscillation

Χ :

Yaw angle (°)

ΔΧ :

Amplitude yawing oscillation

C L :

Lift coefficient

C l :

Rolling moment coefficient

C m :

Pitching moment coefficient

C n :

Yawing moment coefficient

C Y :

Side force coefficient

\(C_{Lq} + C_{{L\dot{\alpha }}}\) :

Lift due to pitch motion

\(C_{mq} + C_{{m\dot{\alpha }}}\) :

Pitch damping derivative

C lp :

Roll damping derivative

C np :

Yaw moment due to roll motion

C Yp :

Side force due to roll motion

\(C_{lr} - C_{{l\dot{\beta }}}\) :

Roll moment due to yaw motion

\(C_{nr} - C_{{n\dot{\beta }}}\) :

Yaw damping derivative

\(C_{Yr} - C_{{Y\dot{\beta }}}\) :

Side force due to yaw motion

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Correspondence to Kerstin C. Huber.

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Appendix

Appendix

See Tables 1, 2, 3 and Figs. 6, 7, 8, 9, 10, 11, 12, 13

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Zimper, D., Huber, K.C. Experimental and numerical investigations of unsteady aerodynamic derivatives for a generic lambda wing UCAV configuration. CEAS Aeronaut J 11, 475–485 (2020). https://doi.org/10.1007/s13272-019-00426-w

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Keywords

  • UCAV
  • Vortex
  • CFD
  • Experiment
  • Dynamic derivatives