The current study presents the results of the aerodynamic noise prediction of the flow field around a NACA 0012 airfoil at a chord-based Reynolds number of 100,000 and at 8.4 degree angle of attack. An incompressible Large Eddy Simulation (LES) turbulence model is applied to obtain the instantaneous turbulent flow field. The noise prediction is performed by the Ffowcs Williams and Hawkings (FW-...

The longitudinal acoustic velocity in silica aerogel is presented as a function of the interstitial gas type and pressure. This was measured using air-coupled ultrasonic transducers configured for differential pulse transit time measurements. The results are interpreted in terms of the thermal relaxation of the acoustic pulse. The microscale temperature oscillations of the gas and solid phases ...

The present paper reports a novel manipulation method for droplets using acoustic radiation pressure and acoustic streaming. In an acoustic field, droplets deform, oscillate and move in a wide range of applied frequencies. The behavior of a droplet depends on the droplet size, acoustic field and interfacial tension between the two phases. The acoustic field is controlled by the voltage and freq...

We consider the numerical solution of the wave equation with impedance boundary conditions and start from a boundary integral formulation for its discretization. We develop the generalized convolution quadrature (gCQ) to solve the arising acoustic retarded potential integral equation for this impedance problem. For the special case of scattering from a spherical object, we derive representation...

A computational approach is proposed to extract the acoustic sources generated by low Mach number flow past a circular cylinder and to predict the associated far-field acoustic pressure. The transient hydrodynamic flow field is calculated using an incompressible computational fluid dynamics (CFD) solver. The acoustic sources are extracted from the hydrodynamic flow field based on the linearised...

Japanese Industrial Standard (JIS) Z 2342 was revised significantly in 2002. The original standard was enacted in 1991 with the title, "Method for acoustic emission testing of pressure vessels during pressure test". The title was also changed, based on NDIS2412 “Acoustic Emission Testing of Spherical Pressure Vessel Made of High Tensile Strength Steel and Classification of Test Results”, which ...

A sound wave traveling in air causes oscillations in pressure above or below the ambient atmospheric pressure. In acoustic theory, a sound source is mainly characterized by its amplitude and frequency (f). The acoustic incident pressure field (p̃) at an observation point, x, due to a point source located at xs is given by Equation 1 where, ω = 2πf , c0 is the speed of sound and S̃ represents the ...

Changes in swimbladder morphology in an Atlantic herring Clupea harengus with pressure were examined by magnetic resonance imaging of a dead fish in a purpose-built pressure chamber. Swimbladder volume changed with pressure according to Boyle's Law, but compression in the lateral aspect was greater than in the dorsal aspect. This uneven compression has a reduced effect on acoustic backscatterin...