Final Report Summary - FLOVIST (Flow visualization inspired aero-acoustics with time-resolved Tomographic Particle Image Velocimetry)
The research team of the FLOVIST project is investigating new methods to visualize the production of acoustic noise by airflows around aircraft. Making use of the concept of medical tomography applied to laser visualization of airflows, the group is now able to determine the velocity field around three-dimensional models in wind tunnels. The team is concentrating on the development of techniques based on the use of high-speed lasers and fast CMOS cameras in order to achieve a 3D time-resolved, or 4D, description of the flow. By doing this it will be possible to unveil the complex process of sound production by turbulent flow interactions with wings and at the exhaust of jet engines.
The research conducted so far has shown that it is now possible to determine the instantaneous hydrodynamic pressure field from a measurement conducted with high-speed Particle Image Velocimetry (PIV). This enables in turn the study of unsteady flow-structure interactions for instance as flutter and acoustics noise generation.
The first experiments performed in the flow around an airfoil immersed in the wake of a circular obstacle (e.g. engine rotor-stator interaction) has shown that PIV can be used to predict the noise emitted by vortices interacting with an aerodynamic object. At the same time, the technique enables a better understanding of the behavior of such vortices.
A more ambitious objective of the project is the direct determination of the acoustic pressure field from time-resolved tomographic PIV measurements. At the aerodynamics laboratories of Delft University of Technology a jet tomography facility (JTF) has been realized where the experiments yield state-of-the-art 4D visualizations of the velocity field that can be used as input for theoretical models (acoustic analogies) to predict the sound generation and emission.
The team has been able to visualize the sound source activity and further experiments are being conducted into an anechoic room to compare the predictions obtained with PIV and the direct measurements by microphones and pressure transducers.
There is large interest in this area of research, as demonstrated by the many groups worldwide that turned their attention towards this new three-dimensional measurement technique. Since the introduction of Tomographic PIV in 2006 by the TU Delft team forming now FLOVIST, more than 100 research papers have been published, a European FP7 project led by the FLOVIST PI (Advanced Flow Diagnostics for Aeronautical research - AFDAR) has started activities in late 2010 to try to apply these technologies for applied aeronautical research.
The FLOVIST project has attracted much attention of the scientific community with its wide results spanning from theory of digital image processing and laser optics applied to 3D velocity measurements, to vortex dynamics and turbulence. The team members participated in several international conferences also delivering a number of keynote and invites talks. Several peer-reviewed articles and book chapters were compiled and published.
There were also unexpected outcomes: the techniques developed by the FLOVIST team have turned out very useful in the study of the European launcher ARIANE V. The European Space Agency ESA commissioned the experimental study of the unsteady flow around the first stage main engine, which was performed for the first time with high-speed PIV in an industrial wind tunnel.
The research conducted so far has shown that it is now possible to determine the instantaneous hydrodynamic pressure field from a measurement conducted with high-speed Particle Image Velocimetry (PIV). This enables in turn the study of unsteady flow-structure interactions for instance as flutter and acoustics noise generation.
The first experiments performed in the flow around an airfoil immersed in the wake of a circular obstacle (e.g. engine rotor-stator interaction) has shown that PIV can be used to predict the noise emitted by vortices interacting with an aerodynamic object. At the same time, the technique enables a better understanding of the behavior of such vortices.
A more ambitious objective of the project is the direct determination of the acoustic pressure field from time-resolved tomographic PIV measurements. At the aerodynamics laboratories of Delft University of Technology a jet tomography facility (JTF) has been realized where the experiments yield state-of-the-art 4D visualizations of the velocity field that can be used as input for theoretical models (acoustic analogies) to predict the sound generation and emission.
The team has been able to visualize the sound source activity and further experiments are being conducted into an anechoic room to compare the predictions obtained with PIV and the direct measurements by microphones and pressure transducers.
There is large interest in this area of research, as demonstrated by the many groups worldwide that turned their attention towards this new three-dimensional measurement technique. Since the introduction of Tomographic PIV in 2006 by the TU Delft team forming now FLOVIST, more than 100 research papers have been published, a European FP7 project led by the FLOVIST PI (Advanced Flow Diagnostics for Aeronautical research - AFDAR) has started activities in late 2010 to try to apply these technologies for applied aeronautical research.
The FLOVIST project has attracted much attention of the scientific community with its wide results spanning from theory of digital image processing and laser optics applied to 3D velocity measurements, to vortex dynamics and turbulence. The team members participated in several international conferences also delivering a number of keynote and invites talks. Several peer-reviewed articles and book chapters were compiled and published.
There were also unexpected outcomes: the techniques developed by the FLOVIST team have turned out very useful in the study of the European launcher ARIANE V. The European Space Agency ESA commissioned the experimental study of the unsteady flow around the first stage main engine, which was performed for the first time with high-speed PIV in an industrial wind tunnel.