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Prediction of laminar-to-turbulent transition in a separated boundary layer subjected to an external acoustic forcing

Kubacki S., Rarata Z., Drózdz A., Gnatowska R., Sokolenko V., Elsner W.

Archives of Mechanics

2023

Vol. 75, nr 5

591--616

The new Reynolds-averaged Navier–Stokes (RANS)-based method has been developed for taking into account, in an approximate manner, the effect of external acoustic forcing on laminar-to-turbulent transition in a separated boundary layer. Experimental studies [33] report an increase of the turbulent shear stress within the separated boundary layer under the influence of acoustic forcing. Enhancement of flow disturbances in a reversed flow region was also reported in our experiment. Experimental findings stimulated the development of a reduced-order aero-acoustic strategy. The effect of acoustic forcing was incorporated into the modelling framework of an algebraic intermittency model. The model component was tuned based on our experimental data and validated on reference experiments. The results show the feasibility of the proposed model to simulate flow over a flat plate and the NACA0018 profile.

Electromagnetic Radiation Generated by Acoustic Excitation of Rock Samples

Yavorovich L. V., Bespalko A. A., Fedotov P. I., Baksht R. B.

Acta Geophysica

2016

Vol. 64, no. 5

1446--1461

The paper presents an experiment on acoustic excitation of electromagnetic radiation (EMR) signals in skarn, sandstone, and magnetite ore samples. For the skarn and sandstone samples, the EMR signal amplitude was observed to decrease with increasing ultimate strength. Supposedly, this effect can be explained by assuming that EMR is generated when an acoustic wave propagates through an electrical double layer. The presence of piezoelectric inclusions (e.g., quartz) in the magnetite ore enhances the analog EMR signal and its spectral components.

Acoustic excitation of isothermal and heated air jets

Bogusławski A., Żabierek D.

Turbulence : international journal

2002

Vol. 8-9

175-188

The paper presents some preliminary studies of the homogeneous and non-isothermal jet response to external acoustic forcing. The experiment shows a complexity of the flow phenomena under sound excitation. It reveals that the natural flow instabilities can be amplified by external forcing but also that flow oscillations can be entirely driven by external forcing provided that high enough forcing level is applied. An interesting shift of the jet response frequency for isothermal jet caused by external forcing was noted. Some visualisation studies of the homogeneous jet strongly forced in order to generate "side jets" were briefly discussed.