Acoustic Field of a Pulsed Circular Piston

Freedman, A.

doi:10.1006/jsvi.1994.1080

Cited by 8 publications

(8 citation statements)

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“…In the replica pulse method [20], the diffraction effects for a plane piston are explained intuitively as the result of the edge wave. The edge wave emanates from the abrupt change in surface velocity at the aperture edge and can be avoided by apodizing the aperture.…”

Section: A Transmit Apodization Functionmentioning

confidence: 99%

A new method for estimation of velocity vectors

Jensen¹,

Munk²

1998

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

407

345

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The paper describes a new method for determining the velocity vector of a remotely sensed object using either sound or electromagnetic radiation. The movement of the object is determined from a field with spatial oscillations in both the axial direction of the transducer and in one or two directions transverse to the axial direction. By using a number of pulse emissions, the inter-pulse movement can be estimated and the velocity found from the estimated movement and the time between pulses. The method is based on the principle of using transverse spatial modulation for making the received signal influenced by transverse motion. Such a transverse modulation can be generated by using apodization on individual transducer array elements together with a special focusing scheme. A method for making such a field is presented along with a suitable two-dimensional velocity estimator. An implementation usable in medical ultrasound is described, and simulated results are presented. Simulation results for a flow of 1 m/s in a tube rotated in the image plane at specific angles (0, 15, 35, 55, 75, and 90 degrees) are made and characterized by the estimated mean value, estimated angle, and the standard deviation in the lateral and longitudinal direction. The average performance of the estimates for all angles is: mean velocity 0.99 m/s, longitudinal S.D. 0.015 m/s, and lateral S.D. 0.196 m/s. For flow parallel to the transducer the results are: mean velocity 0.95 m/s, angle 0.10, longitudinal S.D. 0.020 m/s, and lateral S.D. 0.172 m/s.

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Section: A Transmit Apodization Functionmentioning

confidence: 99%

A new method for estimation of velocity vectors

Jensen¹,

Munk²

1998

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

407

345

View full text Add to dashboard Cite

show abstract

“…In the first animation (Online resource 1), containing the pressure field evolution for the largest spot diameter (6.5 mm, flat top) the structure of the transient field can be observed best. In the beginning, it resembles the field of a pulsed circular flat piston [15], consisting of two linearly superimposable contributions: (i) the central planar compressional wave (here, the wavefront is slightly curved to match the curvature of the cornea), propagating inside the cylindrical volume representing the geometrical shadow of the source at the surface and propagating away from the source, and (ii) the so-called edge wave, emanating from the rim of the circular (piston) source in a hemi-toroidal fashion. The outer part of the edge wave has the same polarity (here positive pressure, compression) as the central wave, while the inner portion has the opposite polarity (here negative pressure, rarefaction), consistent with the simplified theory [15].…”

Section: Resultsmentioning

confidence: 99%

Pressure wave focusing effects following laser medical procedures in human eyes

et al. 2020

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“…Again the exact solution cannot be obtained; hence, we cannot make a quantitative evaluation of the results and the qualitative evaluation will demonstrate the correctitude of our results. The proposed approach is solved using the Navier-Stokes equations, where the wall boundary conditions and piston source characteristics for wall-embedded pistons, Equations (15)- (16), and the outflow boundary conditions are handled using the PML and acoustic radiation conditions of Tam and Webb [23], Equations (16) and (18). Next, we study the interference of the waves of three sources when the source is characterized by low frequency (ka = 2) and high frequency (ka = 8).…”

Section: Array Of Baffled Pistonsmentioning

confidence: 99%

“…Wave generation from a vibrating circular piston is a classical acoustic problem, and has been investigated by, among others, Freedmann [18], Lele and Hamilton [19], Cleveland et al [20], Williams [21], Blackstock [22], and Cheong and Lee [12].…”

Section: Introductionmentioning

confidence: 99%

A finite volume‐based high‐order, Cartesian cut‐cell method for wave propagation

Popescu

Vedder

Shyy

2008

Numerical Methods in Fluids

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SUMMARYComputational aeroacoustics requires numerical techniques capable of yielding low artificial dispersion and dissipation to preserve the amplitude and the frequency characteristics of the physical processes. Furthermore, for engineering applications, the techniques need to handle irregular geometries associated with realistic configurations. We address these issues by developing an optimized prefactored compact finite volume (OPC-fv) scheme along with a Cartesian cut-cell technique. The OPC-fv scheme seeks to minimize numerical dispersion and dissipation while satisfying the conservation laws. The cut-cell approach treats irregularly shaped boundaries using divide-and-merge procedures for the Cartesian cells while maintaining a desirable level of accuracy. We assess these techniques using several canonical test problems, involving different levels of physical and geometric complexities. Richardson extrapolation is an effective tool for evaluating solutions of no high gradients or discontinuities, and is used to evaluate the performance of the solution technique. It is demonstrated that while the cut-cell method has a modest effect on the order of accuracy, it is a robust method. The combined OPC-fv scheme and the Cartesian cut-cell technique offer good accuracy as well as geometric flexibility.

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Acoustic Field of a Pulsed Circular Piston

Cited by 8 publications

References 0 publications

A new method for estimation of velocity vectors

A new method for estimation of velocity vectors

Pressure wave focusing effects following laser medical procedures in human eyes

A finite volume‐based high‐order, Cartesian cut‐cell method for wave propagation

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