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Abstract: The quantitative prediction of bubbly flow around a maneuvering surface ship is critical in determining its hydrodynamic performance and its acoustic and optical signatures. It is a challenging multiscale problem that relies heavily on subgrid models of turbulence and air entrainment. In this manuscript we analyze this problem using a phenomenological air entrainment model that predicts the location and rate of air entrainment around a surface ship. This subgrid model was coupled with a two-fluid Reynolds averaged Navier Stokes (RaNS) bubbly flow model and used to evaluate the flow field around a naval surface ship in straight ahead and turning motions. For straight ahead motion the predicted void fraction distributions aft of the stern were compared with experiments at three different ship speeds and good agreement was found. The qualitative differences in the location of the air entrainment and the resulting bubbly flow between straight ahead and steady turning motions were discussed and compared with experimental observations at sea. To our knowledge this study presents the first quantitative numerical prediction of void fraction distributions around a full-scale surface ship, well matching the experimental measurements. [Copyright &y& Elsevier]

Abstract: A direct computation of the noise radiated by a turbulent flow in a duct obstructed by a diaphragm is performed by compressible large-eddy simulation. For the low Mach number configuration considered, a two-step hybrid method could be less expensive, but would fail at characterizing sound-flow interactions. The application of direct calculation is thus challenging but gives both the acoustic and aerodynamic fields in the same computation in order to shed light on the noise generation mechanisms. Acoustic energy is produced and dissipated in the asymmetric jet-type flow issuing from the diaphragm. A low-frequency radiation is correlated with the breakdown of the coherent jet-column structures as the plane jet reattaches the upper wall. The Kelvin–Helmholtz vortices in the shear layers of the jet constitute the primary instabilities but do not radiate sound. On the contrary, this vorticity shedding seems to dissipate waves propagating upstream by enforcing the unsteady Kutta condition. [Copyright &y& Elsevier]

Reports on the discovery that liquid-crystal displays generate sounds. Details of the findings of Jay Patel and Young Jin Kim; How the sound is generated from the motion of liquid-crystal molecules; Uncertainty of practical applications; Where the study is published; Dispute by Antal Jakli of Patel's claim that there have been no prior reports of sound generation from liquid crystals; Assertion by Patel that nothing like this has been done before.

Reports on the technique developed by scientists at Connecticut-based Yale University to test the biological samples of red blood samples as of December 1977. Details of acoustic levitation technique used for suspending liquid and quasiliquid samples in a balance between gravity and acoustical forces; Working of the technique; Need to develop tools to predict the elastic properties of the cells.