Rolf Henke

Investigation on Turbulence Structures in the Wake of a Generic Rocket Configuration

A generic, blunt-based rocket model has been investigated experimentally in a subsonic wind tunnel at Ma ∞ = 0.2 and Re = 4.1 ×106 m − 1. Planar and stereoscopic Particle Image Velocimetry (PIV) provided statistical turbulence information on the unsteady wake flow with high spatial resolution. Multiple perpendicular regions of interest (ROI) were combined to generate three-dimensional views. Distinct flow patterns emerged that can be interpreted as a rotationally symmetric extension to the wake flow of two-dimensional blunt bodies. In addition, measurements using Constant Temperature Anemometry (CTA) confirmed the turbulence levels and provided time-resolved data. A characteristic dynamic mode at a Strouhal number of St D = 0.21 was revealed. A cluster of multiple, high-fidelity pressure transducers were mounted in the base plane of the model. The analysis of pressure fluctuations verified the dynamic mode and showed its spatial coherence along several circumferential positions.

Active Manipulation of a Rectangular Wing Vortex Wake with Oscillating Ailerons and Winglet-Integrated Rudders

This paper presents results of experimental investigations regarding the vortex wake of a rectangular wing with winglets in a water towing tank. The model comprises ailerons and additional rudders, which are integrated into the winglets. The ailerons and the rudders are able to oscillate around a static deflection to excite inherent short-wavelength instabilities in the vortex system. The Particle Image Velocimetry method is used to investigate the vortex wake up to about 40 spans behind the model. The results show that, depending on the preselected aileron and rudder deflections, an oscillation of correctly chosen frequency leads to a faster decay of the vortex wake in comparison to the statical case.

Influencing Aircraft Wing Vortices

Results presented here were obtained within a project which was part of the Collaborative Research Centre SFB 401 “Flow Modulation and Fluid-Structure Interaction at Airplane Wings” funding from the Deutsche Forschungsgemeinschaft (DFG). The goal of this project was to gain better understanding of aircraft wake vortices in order to investigate possibilities to mitigate the hazard posed by these to following aircraft. To this end wind tunnel testing was undertaken in which the vortex wakes of various wings were measured using hot wire anemometry. It was shown that in the near field, the rolling moment induced on a following aircraft can be significantly reduced by introducing additional turbulence into the wake. Another focus point was the investigation into excitation of short wave instability mechanisms in the vortex wake and their effects in the far field. For these purposes experiments with various models and oscillating control surfaces were conducted in water towing tanks in which the vortex wakes were measured using particle image velocimetry. The results show that for an appropriate multi-vortex system, inherent instabilities can be excited leading to a more rapid vortex decay within the first 30 span lengths behind the model. The effects of these mechanisms further out in the far field are, however, minimal.

Vortex Sheets of Aircraft in Takeoff and Landing

In the present paper the development of vortex wake starting from the vortex sheet at the trailing edge of a transport aircraft wing up to the far field over 60 spans downstream is investigated. Different configurations of a half model were investigated in wind and water tunnels as well as in a towing tank by hot-wire anemometry and particle image velocimetry. In addition to an understanding of the development of the wake, means for the attenuation of the impact on following aircraft were investigated. A fin was installed on the suction side of the wing to investigate the impact on the vortex system downstream. The possibility of exploiting short-wave cooperative instabilities to accelerate vortex decay were investigated as well. This included active excitation of instabilities via ailerons oscillated in antiphase.