scholarly journals Acoustic wave propagation through solar granulation: Validity of effective-medium theories, coda waves

2020 ◽  
Vol 643 ◽  
pp. A168
Author(s):  
P.-L. Poulier ◽  
D. Fournier ◽  
L. Gizon ◽  
T. L. Duvall
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Wave Field ◽  
Multiple Scattering ◽  
Acoustic Waves ◽  
Wave Speed ◽  
Coda Waves ◽  
Acoustic Wave Propagation ◽  
Solar Granulation ◽  
Effective Wave

Context. The frequencies, lifetimes, and eigenfunctions of solar acoustic waves are affected by turbulent convection, which is random in space and in time. Since the correlation time of solar granulation and the periods of acoustic waves (∼5 min) are similar, the medium in which the waves propagate cannot a priori be assumed to be time independent. Aims. We compare various effective-medium solutions with numerical solutions in order to identify the approximations that can be used in helioseismology. For the sake of simplicity, the medium is one dimensional. Methods. We consider the Keller approximation, the second-order Born approximation, and spatial homogenization to obtain theoretical values for the effective wave speed and attenuation (averaged over the realizations of the medium). Numerically, we computed the first and second statistical moments of the wave field over many thousands of realizations of the medium (finite-amplitude sound-speed perturbations are limited to a 30 Mm band and have a zero mean). Results. The effective wave speed is reduced for both the theories and the simulations. The attenuation of the coherent wave field and the wave speed are best described by the Keller theory. The numerical simulations reveal the presence of coda waves, trailing the ballistic wave packet. These late arrival waves are due to multiple scattering and are easily seen in the second moment of the wave field. Conclusions. We find that the effective wave speed can be calculated, numerically and theoretically, using a single snapshot of the random medium (frozen medium); however, the attenuation is underestimated in the frozen medium compared to the time-dependent medium. Multiple scattering cannot be ignored when modeling acoustic wave propagation through solar granulation.

Experiments on Damping of Acoustic Waves in Water-Filled Pipes

2006 ◽  
Author(s):  
Vijay Chatoorgoon ◽  
Qizhao Li
Keyword(s):  
Experimental Study ◽  
Wave Propagation ◽  
Acoustic Wave ◽  
Turbulent Flow ◽  
Acoustic Waves ◽  
Model Comparison ◽  
System Response ◽  
Acoustic Wave Propagation ◽  
The Third ◽  
Zero Flow

A simple, fundamental experimental study was conducted to better understand acoustic wave propagation is fluid-filled pipes. Three experiments were undertaken: the first with zero flow and a closed outlet end, the second with turbulent flow and an open outlet end and the third with zero flow and an open outlet end. The intent was to obtain data for model comparison and to determine the effect of turbulent flow on the system response. New insights are obtained and reported.

Acoustic Wave Propagation in the Sun: Implications for Wave Field and Time-Distance Helioseismology

2003 ◽  
Vol 582 (2) ◽  
pp. L121-L124 ◽  
Author(s):  
C. H. Tong ◽  
M. J. Thompson ◽  
M. R. Warner ◽  
S. P. Rajaguru ◽  
C. C. Pain
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Wave Field ◽  
The Sun ◽  
Acoustic Wave Propagation ◽  
Time Distance

EXPERIENCE ON ACOUSTIC WAVE PROPAGATION IN ROCK SALT IN THE FREQUENCY RANGE 1-100 kHz AND CONCLUSIONS WITH RESPECT TO THE FEASIBILITY OF A ROCK SALT DOME AS NEUTRINO DETECTOR

2006 ◽  
Vol 21 (supp01) ◽  
pp. 30-34 ◽  
Author(s):  
GERD MANTHEI ◽  
JÜRGEN EISENBLÄTTER ◽  
THOMAS SPIES
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Rock Salt ◽  
Acoustic Waves ◽  
Wave Attenuation ◽  
High Energy ◽  
Neutrino Detector ◽  
Frequency Range ◽  
Acoustic Wave Propagation

Rock salt is a promising material for the detection of acoustic waves generated by interactions of high energy neutrinos. The economical feasibility of an acoustic neutrino detector strongly depends on the spacing between the acoustic sensors. In this paper we report on our experience on acoustic wave propagation and wave attenuation in rock salt in the frequency range of 1 to 100 kHz and some conclusions with respect to the usefulness of rock salt as a neutrino detector. The experience bases on long-term acoustic emission measurements in a salt mine.

Velocity-Log Interpretation: The Effect of Rock Bulk Compressibility

1961 ◽  
Vol 1 (04) ◽  
pp. 235-248 ◽  
Author(s):  
J. Geertsma
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Wave Velocity ◽  
Acoustic Waves ◽  
Carbonate Rocks ◽  
Empirical Relationship ◽  
Biot Theory ◽  
Porous Rocks ◽  
Acoustic Wave Propagation ◽  
Log Interpretation

Abstract Tbe relationsbip between porosity and the speed of propagation of acoustic waves in fluid-saturated porous rocks as measured by the Sonic log and by ultrasonic techniques is analyzed. Biot's continuum theory is used to explain the difference in acoustic wave propagation between a dry and a liquid-saturated porous material. The porosity is a variable in this theory. However, the acoustic wave propagation in the dry rock depends too on porosity, and this dependence is not predicted by the theory. Frequently in dry sandstones, a nearly linear relationsbip between reciprocal acoustic wave velocity and porosity is observed in the low-porosity range. The physics behind this behavior is outlined. An empirical relationship of the form, 1/V ~ A + B ø, applies accordingly for many porous dry rocks, provided the porosity is the only variable. The presence of a liquid in the pores changes the value of B, and this change is found to be in agreement with the Biot theory. The time-average relation introduced some years ago results in an equation of the same type 1/V = ø/Vf + (1 - ø)/Vr - but is not based on a sound physical picture. Still, this relation sometimes predicts approximately correct A and B values. Carbonate rocks with their complicated pore structures sometimes show a different relationship between wave velocity and porosity, unfavorable for log interpretation. Examples are presented. The simultaneous presence of calcite, dolomite and anhydrite, with their different grain densities and matrix compressibilities, complicates acoustic-log interpretation in carbonate rocks still further. Other complicating effects of acoustic-log interpretation are discussed. They are related to the influence of shale streaks and natural fractures on the average wave velocity observed by the logging tool and to the effect of adsorption phenomena on wave propagation in unstressed rocks particularly in sandstones.

scholarly journals Study of Absorption Loss Effects on Acoustic Wave Propagation in Shallow Water Using Different Empirical Models

2018 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Yasin Yousif Al-Alaboosi ◽  
Jenan Abdulkhalq Al-Aboosi
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Underwater Acoustic Communication ◽  
Ocean Water ◽  
Absorption Loss ◽  
Acoustic Wave Propagation ◽  
Underwater Acoustic ◽  
The Comparative Study ◽  
Target Locating

<p><span lang="EN-US">Efficient underwater acoustic communication and target locating systems require detailed study of acoustic wave propagation in the sea. Many investigators have studied the absorption of acoustic waves in ocean water and formulated empirical equations such as Thorp’s formula, Schulkin and Marsh model and Fisher and Simmons formula. The Fisher and Simmons formula found the effect associated with the relaxation of boric acid on absorption and provided a more detailed form of absorption coefficient which varies with frequency. However, no simulation model has made for the underwater acoustic propagation using these models. This paper reports the comparative study of acoustic wave absorption carried out by means of modeling in MATLAB. The results of simulation have been evaluated using measured data collected at Desaru beach on the eastern shore of Johor in Malaysia. The model has been used to determine sound absorption for given values of depth (D), salinity (S), temperature (T), pH, and acoustic wave transmitter frequency (f). From the results a suitable range, depth and frequency can be found to obtain best propagation link with low absorption loss.</span></p>

Study on the Influence of Roughness on the Detection for Mechanical Characteristics of the Machined Surface by Surface Acoustic Wave Dispersion Theory

2016 ◽  
Vol 693 ◽  
pp. 1447-1452
Author(s):  
Jing Lei Xu ◽  
Bin Lin ◽  
Ya Xu Wei
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Acoustic Waves ◽  
Mechanical Characteristics ◽  
Fractal Theory ◽  
Surface Acoustic Waves ◽  
Wave Dispersion ◽  
Acoustic Wave Propagation ◽  
Machined Surface

The surface acoustic wave (SAW) technique is a precise and nondestructive method to detect the mechanical characteristics of the precision-machined surface. The paper is concerned with the effect of the roughness of the machined surface on the dispersion of surface acoustic waves propagating in the precision-machined surface which indicates mechanical characteristics of the machined surface. The finite element method (FEM) is employed by establishing a series of models with different roughness Ra value to analyze influences from different roughness Ra value on surface acoustic wave dispersion. The models are established by applying a combined method based on fractal theory and wavelet analysis. The simulation results showed that the roughness of machined surface will cause the dispersion of surface acoustic wave propagation, the effect varies with the different roughness Ra values. A critical Ra value influencing on the surface acoustic wave propagation exists. Accordingly, that the factor of roughness should be considered in advance or not, the situation can be determined through studying and determining the critical roughness Ra value above mentioned. Consequently, the study has the important meaning regarding the detection for mechanical characteristics of the machined surface.

scholarly journals The Sensitive Element of Acoustic Sensor on Circular Polarized Waves: From Theoretical Considerations towards Perspective Rotation Rate Sensors Design

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 32
Author(s):  
Michail Shevelko ◽  
Andrey Lutovinov ◽  
Aleksandr Peregudov ◽  
Ekaterina Popkova ◽  
Yasemin Durukan ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Rotation Rate ◽  
Acoustic Waves ◽  
Experimental Studies ◽  
Bulk Acoustic Wave ◽  
Acoustic Wave Propagation ◽  
Direct Excitation ◽  
Numerical Predictions ◽  
Polarized Waves

In this paper, the perspectives of using the features of acoustic wave propagation to design rotation rate sensors (RRS) are discussed. The possibility of developing the solid-state sensitive elements (SE) of RRS on acoustic waves of circular polarization is shown. The theoretical basis of bulk acoustic wave propagation under rotation is given. The direct excitation of circularly polarized acoustic wave (CPAW) is considered, the design of the CPAW emitting transducer is offered. The results of experimental studies that indicated the circular nature of the particle motions in the radiated wave are discussed. The principally new concept of the RRS SE design on CPAW, being able to operate under high vibration and acceleration, is proposed. The experimental results revealed a high correlation with theoretical and numerical predictions and confirmed RRS on CPAW operability.

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