Scattering of plane longitudinal elastic wave by a large convex rigid object with a statistically corrugated surface. II. Far field solution

1974 ◽  
Vol 15 (7) ◽  
pp. 950-953 ◽  
Author(s):  
W. Fan ◽  
Y. M. Chen
Keyword(s):  
Elastic Wave ◽  
Far Field ◽  
Rigid Object ◽  
Corrugated Surface ◽  
Field Solution ◽  
Longitudinal Elastic Wave

A Hypothesized Mechanistic Model of Longitudinal Wall Motion at the Common Carotid Artery

2019 ◽  
Author(s):  
Zhili Hao ◽  
Leryn Reynolds ◽  
John M. Herre
Keyword(s):  
Carotid Artery ◽  
Elastic Wave ◽  
Common Carotid Artery ◽  
Wall Motion ◽  
Mechanistic Model ◽  
External Source ◽  
Arterial Tree ◽  
Longitudinal Elastic Wave ◽  
Longitudinal Wall ◽  
The Common

Abstract In light of recently recognized independent clinical values of longitudinal wall motion ux(t) at the common carotid artery (CCA) and the struggle on appropriate arterial indices for interpreting ux(t), this paper hypothesizes a mechanistic model of ux(t) and explores clear implications of the antegrade amplitude ux0-ante and retrograde amplitude ux0-retro of ux(t) in systole to the cardiovascular (CV) system. By examining findings on ux(t) and other relevant findings through the lens of the engineering essence of ux(t), a mechanistic model of ux(t) is hypothesized: the left ventricle (LV) base rotation is the excitation source for initiating the longitudinal elastic wave propagating along the arterial tree; wall shear stress at an artery serves as a local external source for supplying energy to the longitudinal elastic wave; and longitudinal elasticity at the arterial wall dictates the wave propagation velocity. Integrating the mechanistic model with findings on ux(t) gives rise to interpretation of ux0-ante and ux0-retro for their clear implications: longitudinal elasticity Exx at the common carotid artery (CCA) is estimated from ux0-ante, and ux0-retro is an inverse indicator of the maximum base rotation of the LV and a positive indicator of longitudinal elasticity at the ascending aorta (AA). For the first time, this model reveals the mechanisms underlying those statistical-based findings on ux(t).

SEISMIC VELOCITY STUDY OF SYNTHETIC CORES

Geophysics ◽  
1957 ◽  
Vol 22 (4) ◽  
pp. 813-820 ◽  
Author(s):  
William O. Murphy ◽  
Joseph W. Berg ◽  
Kenneth L. Cook
Keyword(s):  
Elastic Wave ◽  
Elastic Waves ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Seismic Velocity ◽  
Pore Filling ◽  
The Core ◽  
Wave Velocities ◽  
Longitudinal Elastic Wave ◽  
Alcohol Benzene

The velocity of a longitudinal elastic wave through rock at room temperature and at atmospheric pressure depends upon the nature of the rock frame, the porosity of the rock, and the nature of the pore‐filling fluid. In the present investigation longitudinal elastic wave velocities were measured for sixty synthetic cores. The rock frame consisted of sorted quartz sand grains and cement, the percentage of cement varying from ten to fifty percent. The core porosities varied from 8.8 percent to 22 percent. The velocities were measured for dry air‐filled cores and for cores saturated with various liquids. These pore‐filling liquids were distilled water, ethyl alcohol, benzene, carbon tetrachloride, and chloroform. The measured velocities ranged from 2,360 feet per second to 14,710 feet per second. The wave velocity in liquid‐filled cores of 10 percent porosity was approximately twice the velocity for cores of 20 percent porosity, the same type of cement being used in both instances. For any given core, flooded with fluids of wave velocities ranging from 3,000 to 5,000 feet per second, the maximum observed variation in core velocity was around 20 percent. The experimental data fitted the empirical linear equation [Formula: see text] where [Formula: see text] of longitudinal elastic waves passing through the flooded core; [Formula: see text] of longitudinal elastic waves in passing through the saturating fluid. The constant k depends upon the porosity of the rock and the type of cement used. The constant, C, depends upon the nature of the rock frame.

Internal gravity waves generated by oscillations of a sphere

1987 ◽  
Vol 183 ◽  
pp. 439-450 ◽  
Author(s):  
J. C. Appleby ◽  
D. G. Crighton
Keyword(s):  
Gravity Waves ◽  
Separation Of Variables ◽  
Near Field ◽  
Wave Structure ◽  
Internal Gravity Waves ◽  
Spherical Body ◽  
The Body ◽  
Wave Radiation ◽  
Far Field ◽  
Field Solution

We consider the radiation of internal gravity waves from a spherical body oscillating vertically in a stratified incompressible fluid. A near-field solution (under the Boussinesq approximation) is obtained by separation of variables in an elliptic problem, followed by analytic continuation to the frequencies ω < N of internal wave radiation. Matched expansions are used to relate this solution to a far-field solution in which non-Boussinesq terms are retained. In the outer near field there are parallel conical wavefronts between characteristic cones tangent to the body, but with a wavelength found to be shorter than that for oscillations of a circular cylinder. It is also found that there are caustic pressure singularities above and below the body where the characteristics intersect. Far from the source, non-Boussinesq effects cause a diffraction of energy out of the cones. The far-field wave-fronts are hyperboloidal, with horizontal axes. The case of horizontal oscillations of the sphere is also examined and is shown to give rise to the same basic wave structure.The related problem of a pulsating sphere is then considered, and it is concluded that certain features of the wave pattern, including the caustic singularities near the source, are common to a more general class of oscillating sources.

scholarly journals Longitudinal elastic wave control by pre-deforming semi-linear materials

2017 ◽  
Vol 142 (3) ◽  
pp. 1229-1235 ◽  
Author(s):  
Dengke Guo ◽  
Yi Chen ◽  
Zheng Chang ◽  
Gengkai Hu
Keyword(s):  
Elastic Wave ◽  
Longitudinal Elastic Wave ◽  
Wave Control

The DSP Design and Implementation of a Directional Audio System through N-Order Approximate Square Root Method

2013 ◽  
Vol 416-417 ◽  
pp. 1147-1151
Author(s):  
Yong Chun Xu ◽  
Zhe Liu ◽  
Jin Yu Guan
Keyword(s):  
Basic Principle ◽  
Floating Point ◽  
Far Field ◽  
Square Root ◽  
Practical Test ◽  
Design And Implementation ◽  
Field Solution ◽  
And Performance ◽  
Square Root Method ◽  
Audio System

The signal preprocessing methods in a directional audio system are almost based on Berkatay far-field solution. In this paper, the basic principle and performance of square root method are analyzed, and also a directional audio system based on floating-point DSP is designed with the 4-order approximate square root method. Through theory simulation and practical test, the effect is proven to be satisfactory.

scholarly journals REEF3D Wave Generation Interface for Commercial CFD Codes

2019 ◽  
Author(s):  
Csaba Pakozdi ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Elin Marita Hermundstad
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Wave Theory ◽  
Far Field ◽  
New Approach ◽  
Field Solution ◽  
Cfd Models ◽  
Numerical Wave ◽  
The One ◽  
General Interface

Abstract In recent years CFD developments have shown a trend to combine RANS CFD simulation with other methods such as wave theories or velocity potential based numerical wave tanks, in order to reduce to computation costs. This is however not a new approach, and there exists a large amount of literature about domain decomposition techniques describing a two way coupling between the RANS CFD models and other methods. One can also observe an increasing popularity in the use of a less sophisticated technique where different fluid solvers are combined with one-way coupling. In these methods a predefined solution is provided in the far-field (ignoring the structure), while a three-dimensional (3D) CFD simulation is applied in a limited zone near the structure. The predefined solution is used to specify the background far-field solution. The governing equations are extended by the addition of a source term. The published solutions use wave theory or a numerical wave tank where the predefined solution is calculated parallel to the RANS solver. In this way it is possible to reduce the interpolation inaccuracy and the amount of transferred data to the CFD simulation. The disadvantage of this technique is that the far field solver has to be prepared in order to run in parallel with the CFD solver. Due to the one way coupling it is possible to predefine this information in tables before the CFD simulation. This technique makes it possible to define a general interface between difference solvers without modifying existing codes. This paper presents such a technique where the predefined solution is stored into files. An interpolation function delivers all data to the far-field solution for the CFD simulation. The paper analyses the necessary accuracy of the interpolation and the costs of the input/output operation of the CFD simulation through several verification cases.

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