Acoustic interferometer

About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.

Local and selective detection of acoustic waves at the surface of a material

Abstract: A method for detecting selectively elastic waves at the surface of a solid is described. This method is based on the propagation of transversal waves in a tapered rod. The probe is composed of a shear wave transducer coupled to a focusing tip. Selective detection of acoustic waves at the surface of materials is experimentally demonstrated. Conical and parabolic tips are compared. The sensitivity of the probe as well as the local perturbation induced by the contact is investigated with an optical heterodyne interferometer.

Theoretical and experimental investigation of acoustic streaming in a porous material.

Abstract: An experimental and theoretical investigation of the influence of high-frequency acoustic waves on the flow of a liquid through a porous material has been made. Particular attention was paid to the phenomenon of acoustic streaming of the liquid in the porous material due to the damping of the acoustic waves. The experiments were performed on Berea sandstone cores. Two acoustic horns were used with frequencies of 20 and 40 kHz, and with maximum power output of 2 and 0.7 kW, respectively. A high external pressure was applied in order to avoid cavitation. A microphone was used to measure the damping of the waves in the porous material and also temperature and pressure measurements in the flowing liquid inside the cores were carried out. To model the acoustic streaming effect Darcy's law was extended with a source term representing the momentum transfer from the acoustic waves to the liquid. The model predictions for the pressure distribution inside the core under acoustic streaming conditions are in reasonable agreement with the experimental data.

Ultrasonic absorption properties of methyl cyanide + water mixtures

Abstract: Ultrasonic absorption properties have been determined for water + methyl cyanide mixtures at 273, 298 and 308 K and over the frequency range 1.5-230 MHz using a travelling pulse technique, and qualitatively examined at 298 K over the range 200–1 500 kHz using a reverberation apparatus. Sound velocities in these mixtures have been measured at 273, 298 and 308 K and at 2 MHz using an acoustic interferometer. The variation of ultrasonic absorption with frequency (1.5-230 MHz) is analyzed in two ways; (i) assuming that there are two discrete relaxation frequencies, and (ii) using an expression which follows from a treatment by Romanov and Solovyev of concentration fluctuations. The latter analysis has the advantage that it identifies those mixtures where the volume, Gibbs function and enthalpy control the magnitude of the sound absorption. The analysis provides interaction lengths lm and diffusion coefficients, D, for methyl cyanide + water mixtures.

Development of SAW thermocycler for small liquid droplets

Abstract: In this paper, we present a liquid-droplet-heating system using a surface acoustic wave (SAW) device. When liquid is placed on a Rayleigh-SAW-propagating surface, a longitudinal wave is radiated into the liquid. If the SAW amplitude increases, the liquid shows nonlinear dynamics, such as vibrating, streaming, small droplet flying, and atomizing. This phenomenon is well known as SAW streaming. The liquid temperature is measured during the longitudinal wave radiation and found to increase. First, the mechanism of liquid heating phenomenon is discussed. Second, the fundamental properties of the liquid temperature are measured by varying the applied voltage, duty factor, and liquid viscosity. The liquid temperature is found to be proportional to the duty factor and the square of the applied voltage. Therefore, the liquid temperature can be controlled by these applied signals. Also, by using highly viscous solutions, the liquid temperature is increased to more than 100 ˚C. Finally, the possibility of periodic temperature control is tested by varying the duty factor. The obtained results strongly suggest that an efficient thermal cycler is realized. A novel application of the SAW device is proposed on the basis of SAW streaming.