Jet-wing Interaction Research Articles

Active control of jet-plate interaction noise for excited jets by plasma actuators

This paper examines the possibility of controlling jet-wing interaction noise by plasma actuators. The low-frequency part of the jet installation noise is considered as produced by the diffraction of instability wave packets developing in the jet shear layer. Thus, the main idea of noise control comes to the attempt to reduce the amplitude of these wave packets near the wing trailing edge. A simplified jet-plate configuration is studied experimentally for jet Mach numbers ranging from 0.4 to 0.6. To avoid additional complications related to the control of stochastic signals in the first step, the jet is excited by a loudspeaker at a frequency corresponding to Strouhal number 0.6. Acoustic forcing generates axisymmetric instability wave in the jet shear layer, which is the object of control. The control action is implemented by a high-frequency dielectric barrier discharge (HF DBD) plasma actuator with a ring-like electrode mounted inside the nozzle near the exit. It is demonstrated that installation noise can be significantly suppressed if the plasma actuator generates instability wave with the amplitude equal to that of the excited by the loudspeaker, but in antiphase to it, and vice versa, if these instability waves are in phase, installation noise increases by about 6 dB. The obtained results support the idea that low-frequency jet-wing installation noise can be controlled in a linear framework.

Jet and jet–wing noise modelling based on the CABARET MILES flow solver and the Ffowcs Williams–Hawkings method

A co-axial subsonic unheated jet with and without a swept lifting wing at free-stream conditions from a recent jet–wing TsAGI experiment is considered. For computational modelling, Monotonically Integrated Large Eddy Simulations (MILES) are conducted based on the CABARET scheme which is implemented in a modern parallel unstructured-grid compressible Navier–Stokes computational code. The computational domain of the installed configuration includes a part of the nozzle and a wing section with round flow-fences present in the experiment to preclude the downwash effects. For the isolated jet, the same size of the computational domain is applied and two grid resolutions are considered to investigate the sensitivity of the current far-field noise predictions to the computational grid. The meanflow velocity profiles predicted downstream of the nozzle are compared with the flow data available. For far-field acoustic predictions, the Ffowcs Williams-Hawkings (FW-H) integral method is used. The Ffowcs Williams-Hawkings solutions correspond to a large closed permeable control surface with multiple closing disks at the outlet side set-up in accordance with the best practice to avoid pseudo sound in the acoustic modelling. The comparison of the acoustic predictions with the far-field spectra measured in the experiment for 30° and 90° observer angles to the jet flow are presented and discussed. It is shown that the current modelling robustly captures the same relative trends of the spectra behavior as observed in the experiment: while the presence of the wing does not lead to any significant change of sound spectrum in comparison with the isolated jet for 30°, there is a [Formula: see text] sound amplification due to the jet–wing interaction at 90° angle to the jet.

Flow-induced pressure fluctuations of a moderate Reynolds number jet interacting with a tangential flat plate

The increase of air traffic volume has brought an increasing amount of issues related to carbon and NOx emissions and noise pollution. Aircraft manufacturers are concentrating their efforts to develop technologies to increase aircraft efficiency and consequently to reduce pollutant discharge and noise emission. Ultra High By-Pass Ratio engine concepts provide reduction of fuel consumption and noise emission thanks to a decrease of the jet velocity exhausting from the engine nozzles. In order to keep same thrust, mass flow and therefore section of fan/nacelle diameter should be increased to compensate velocity reduction. Such feature will lead to close-coupled architectures for engine installation under the wing. A strong jet-wing interaction resulting in a change of turbulent mixing in the aeroacoustic field as well as noise enhancement due to reflection phenomena are therefore expected. On the other hand, pressure fluctuations on the wing as well as on the fuselage represent the forcing loads, which stress panels causing vibrations. Some of these vibrations are re-emitted in the aeroacoustic field as vibration noise, some of them are transmitted in the cockpit as interior noise. In the present work, the interaction between a jet and wing or fuselage is reproduced by a flat surface tangential to an incompressible jet at different radial distances from the nozzle axis. The change in the aerodynamic field due to the presence of the rigid plate was studied by hot wire anemometric measurements, which provided a characterization of mean and fluctuating velocity fields in the jet plume. Pressure fluctuations acting on the flat plate were studied by cavity-mounted microphones which provided point-wise measurements in stream-wise and spanwise directions. Statistical description of velocity and wall pressure fields are determined in terms of Fourier-domain quantities. Scaling laws for pressure auto-spectra and coherence functions are also presented.

Theoretical Aerodynamics of Over-Wing-Blowing Configuration

Previous investigations on OWB aerodynamics2'3 have been centered on the jet entrainment effect, without properly accounting for the dynamic pressure difference in the flowfield because of the presence of the jet. The predicted lift has been found to be too low as compared with experiments, in particular, when the jet is close to the wing. In this paper, the additional lift induced by the over-wing-blowing jets is attributed to the inviscid jet-wing interaction due to the higher jet dynamic pressure and the jet flap effect. The methods used in computing the jet entrainment effect and the wing-jet interaction are summarized in the following. Existing methods for computing jet entrainment are mainly for incompressible, nonheated jets.4 To extend the methods to compressible heated jets, Kleinstein's theory for free compressible jets is revised to include the effect of external stream, with the simplicity of his theory being retained. In this extended theory, the axial velocity is given by