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Yaw-control efficiency analysis for a diamond wing configuration with outboard split flaps

  • Stefan PfnürEmail author
  • Sven Oppelt
  • Christian Breitsamter
Original Paper
  • 37 Downloads

Abstract

The yaw-control device of a low-aspect ratio flying wing with diamond-shaped wing planform is investigated. Extensive low-speed wind tunnel experiments have been carried out to obtain surface pressure data and the aerodynamic forces and moments of the configuration for six different flap deflection angles at varying angles of attack and sideslip. Complementary unsteady Reynolds-averaged Navier–Stokes simulations are performed for selected configurations. The experimental data is used to examine the validity of the numerical results. The analysis is focused on the aerodynamic coefficients and derivatives. Yaw-control effectiveness, yaw-control efficiency, crosswind landing capabilities and coupling effects are discussed. The results show sufficient yaw-control effectiveness and efficiency for a wide range of considered freestream conditions. The outboard flap exhibits a non-linear characteristic with respect to the flap deflection angle and freestream conditions. The efficiency is considerably reduced at high angles of attack due to large-scale flow separation in the wing outboard section. Non-linear coupling effects with the rolling moment become obvious for moderate to large flap deflections over the whole angle of attack polar. The numerical results show good agreement with the experimental data in the surface pressure distributions and longitudinal aerodynamic coefficients. The yawing moment is overpredicted by numerical simulations for large flap deflection angles.

Keywords

Aerodynamics Diamond wing Flying wing Stability and control Directional Stability Directional control Vortex aerodynamics Wind tunnel 

List of symbols

b

Wing span (m)

\(C_{D},C_{Y},C_{\text {L}}\)

Drag, side force and lift coefficient, \(C_{i} = \frac{i}{q_{\infty } \cdot S_{\text {ref}}}\)

\(C_{ij}\)

Aerodynamic derivative (1/rad), \({\text {d}}Ci/{\text {d}}j\)

\(C_{{mx}},C_{{mz}}\)

Rolling and yawing moment coefficient, \(C_{mi} = \frac{Mi}{q_{\infty } \cdot b/2 \cdot S_{\text {ref}}}\)

\(C_{my}\)

Pitching moment coefficient, \(C_{my} = \frac{My}{q_{\infty } \cdot l_\mu \cdot S_{\text {ref}}}\)

\(c_{\text {p}}\)

Pressure coefficient, \(c_{\text {p}} = \frac{p-p_{\infty }}{q_{\infty }}\)

\(c_{\text {r}}\)

Root chord (m)

\(c_{\text {t}}\)

Tip chord (m)

DYL

Drag, side force and lift (N)

f

Sampling rate (Hz)

\(F_x,F_y\)

Axial and lateral force in body-fixed axis system (N)

\(l_\gamma\)

Lever arm of force at outboard flap creating the yawing moment (m)

\(l_{\mu }\)

Mean aerodynamic chord (m)

Ma

Mach number

MxMyMz

Rolling, pitching and yawing moment (Nm)

p

Static pressure (N/m\(^{2}\))

q

Dynamic pressure (N/m\(^{2}\))

Re

Reynolds number

\(S_{\text {pr}}\)

Projected area (m\(^{2}\))

\(S_{\text {ref}}\)

Wing reference area (m\(^{2}\))

T

Temperature (K)

t

Time (s)

U

Velocity (m/s)

\(x_{\text {mrp}}\)

Moment reference point (m)

xyz

Cartesian coordinates (m)

\(y^+\)

Dimensionless wall distance

\(\alpha\)

Angle of attack (\(^{\circ }\))

\(\beta\)

Angle of sideslip (\(^{\circ }\))

\(\gamma _1\)

Angle between body-fixed x-axis and optimal lever arm (\(^{\circ }\))

\(\gamma _2\)

Angle between body-fixed x-axis and outboard flap force vector in body-fixed xy-plane (\(^{\circ }\))

\(\zeta\)

Outboard flap deflection angle (\(^{\circ }\))

\(\eta\)

Non-dimensional lateral coordinate, \(\eta =\frac{y}{b/2}\)

\(\varLambda\)

Wing aspect ratio

\(\lambda\)

Wing taper ratio

\(\xi\)

Midboard flap deflection angle (\(^{\circ }\))

\(\rho\)

Density (kg/m\(^{3}\))

\(\varphi\)

Wing sweep (\(^{\circ }\))

Subscripts

cw

Crosswind

HL

Hinge line

max

Maximum

meas

Measurement

le

Leading edge

L

Lower

O/F

Outboard flap

opt

Optimal

R

Right

sim

Simulation

td

Touchdown

te

Trailing edge

U

Upper

\(\infty\)

Freestram value

Notes

Acknowledgements

The support of this investigation by Airbus Defence and Space within the VitAM/VitAMInABC (Virtual Aircraft Model for the Industrial Assessment of Blended Wing Body Controllability, FKZ: 20A1504C) project is gratefully acknowledged. Furthermore, the authors thank the German Aerospace Center (DLR) for providing the DLR TAU code used for the numerical investigations. Moreover, the authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (http://www.gauss-centre.eu) for funding this project by providing computing time on the GCS Supercomputer SuperMUC at Leibniz Supercomputing Centre (LRZ, http://www.lrz.de).

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Copyright information

© Deutsches Zentrum für Luft- und Raumfahrt e.V. 2018

Authors and Affiliations

  1. 1.Chair of Aerodynamics and Fluid Mechanics, Department of Mechanical EngineeringTechnical University of MunichGarching bei MünchenGermany

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