# Vortex breakdown above a delta wing with sharp leading edge

## Description of Experiment

The experiment of TU München is described in detail by Furman and Breitsamter (2009). It has been performed in a low-speed wind tunnel of closed-return type with an open test section. The following measurement techniques have been used for the considered conditions:

• Steady surface pressure taps (sampling rate of 100 Hz, averaging time of 10 s).
• Unsteady surface pressure sensors (sampling rate of 2000 Hz, sample time of 40 s).
• Stereo Particle Image Velocimetry (Stereo-PIV) to measure time-averaged velocities.
• Hot-Wire Anemometry (HWA) to measure velocity fluctuations.
• Oil-flow visualization of the surface streamlines.

## Boundary Data

The free stream is defined by the Mach number and angle of attack as specified above. The experimenters give the following indications for the uncertainty in the free stream:

• uncertainty in free stream direction less than 0.2°,
• static pressure variations along tunnel axis less than 0.4%,
• uncertainty in temporal and spatial mean velocity distribution less than 0.6%.

Furthermore, the free stream turbulence intensity is stated to be less than 0.4%.

## Measurement Errors

For the different measurement techniques employed (pressures sensors, HWA, stereo-PIV) no information on measurement uncertainties is given by the experimenters.

## Measured Data

The measured data consists of the following set:

• Steady surface pressure measurements at five chord stations (plots):
${\displaystyle {x/c_{r}=0.2}}$ (data), ${\displaystyle {0.4}}$ (data), ${\displaystyle {0.6}}$ (data), ${\displaystyle {0.8}}$ (data), and ${\displaystyle {0.95}}$ (data).
• Unsteady surface pressure measurements at four chord stations (plots):
${\displaystyle {x/c_{r}=0.4}}$ (data), ${\displaystyle {0.6}}$ (data), ${\displaystyle {0.8}}$ (data), and ${\displaystyle {0.95}}$ (data).
• Mean velocity field and fluctuating velocity field at three cross planes (README):
${\displaystyle {x/c_{r}=0.4}}$ (data), ${\displaystyle {0.6}}$ (data), and ${\displaystyle {0.8}}$ (data).

## References

1. A. Furman and Ch. Breitsamter (2008) Turbulent and unsteady flow characteristics of delta wing vortex systems, AIAA Paper 2008-0381.
2. A. Furman and Ch. Breitsamter (2009) Experimental investigations on the VFE-2 configuration at TU Munich, Germany. Chapter 21 in: Understanding and Modeling Vortical Flows to Improve the Technology Readiness Level for Military Aircraft, RTO-TR-AVT-113, NATO RTO. http://ftp.rta.nato.int/public/PubFullText/RTO/TR/RTO-TR-AVT-113/TR-AVT-113-12.pdf.

Contributed by: J.C. Kok, H. van der Ven (National Aerospace Laboratory NLR Amsterdam, The Netherlands), E. Tangermann (Airbus Defence and Space München, Germany), S. Sanchi (Computational Fluids and Structures Engineering Lausanne, Switzerland), A. Probst and K.A. Weinman (German Aerospace Center DLR Göttingen, Germany), L. Temmerman (NUMECA International Brussels, Belgium) — '