Meteorological Focusing of Acoustic Energy

1963 ◽  
Vol 2 (6) ◽  
pp. 24-27
Author(s):  
Richard N. Tedrick
Keyword(s):  
Acoustic Energy

scholarly journals Newly designed solid coupling medium for reducing trapped air pockets during extracorporeal shock wave lithotripsy_ a phantom study

BMC Urology ◽  
2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Chien-Sheng Wang ◽  
Ching-Chia Li ◽  
Wen-Jeng Wu ◽  
Wen-Chin Liou ◽  
Yusen Eason Lin ◽  
...  
Keyword(s):  
Shock Wave ◽  
Phantom Study ◽  
Acoustic Energy ◽  
Disintegration Rate ◽  
Measuring Device ◽  
Trapped Air ◽  
Extracorporeal Shock Wave ◽  
Air Pockets ◽  
Coupling Medium ◽  
Level 2

Abstract Introduction Air pockets between the lithotripter head and body surface are almost inevitably generated when applying a handful of gel onto the contact portion of the treatment head and that on the patient’s skin during coupling procedure. These air pockets can compromise the transmission of acoustic energy of shock wave and may significantly affect efficacy of stone disintegration. Comparing to conventional gel, this study aims to investigate efficacy of stone disintegration by using a proprietary isolation-coupling pad (“icPad”) as the coupling medium to reduce trapped air pockets during ESWL procedure. Method In this phantom study, Dornier lithotripter (Delta-2 RC, Dornier MedTech Europe GmbH Co., Germany) was used with a proprietary gel pads (icPad, Diameter = 150 mm, Thickness = 4 mm and 8 mm). The lithotripter was equipped with inline camera to observe the trapped air pockets between the contact surface of the lithotripter head. A testing and measuring device were used to observe experimental stone disintegration using icPad and semi-liquid gel. The conventional semi-liquid gel was used as control for result comparison. Results The stone disintegration rate of icPad 4 mm and 8 mm after 200 shocks of energy at level 2 were significantly higher than that of the semi-liquid gel (disintegration rate 92.3%, 85.0% vs. 45.5%, respectively, p < 0.001). The number of shocks for complete stone disintegration by icPad of 4 mm and 8 mm at the same energy level 2 were significantly lower than that of the semi-liquid gel (the number of shocks 242.0 ± 13.8, 248.7 ± 6.3 vs. 351.0 ± 54.6, respectively, p = 0.011). Furthermore, quantitative comparison of observed air pockets under Optical Coupling Control (OCC) system showed that the area of air pockets in semi-liquid group was significantly larger than that of the group using icPad (8 mm) and that of the group using icPad (8 mm) after sliding (332.7 ± 91.2 vs. 50.3 ± 31.9, 120.3 ± 21.5, respectively, p < 0.05). Conclusion The advantages of icPad includes: (1) reduced the numbers of shock wave and increased stone disintegration rate due to icPad’s superior efficacy; (2) significantly reduce trapped air pockets in ESWL coupling. Due to the study limitation, more data are needed to confirm our observations before human trials.

scholarly journals Measurement of Underwater Acoustic Energy Radiated by Single Raindrops

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2687
Author(s):  
Shu Liu ◽  
Qi Li ◽  
Dajing Shang ◽  
Rui Tang ◽  
Qingming Zhang
Keyword(s):  
Ambient Noise ◽  
Sound Pressure ◽  
Tap Water ◽  
Acoustic Energy ◽  
Underwater Sound ◽  
Underwater Noise ◽  
Energy Characteristics ◽  
Sound Energy ◽  
Dipole Radiation ◽  
Series Of Experiments

Underwater noise produced by rainfall is an important component of underwater ambient noise. For example, the existence of rainfall noise causes strong disturbances to sonar performance. The underwater noise produced by a single raindrop is the basis of rainfall noise. Therefore, it is necessary to study the associated underwater noise when drops strike the water surface. Previous research focused primarily on the sound pressure and frequency spectrum of underwater noise from single raindrops, but the study on its sound energy is insufficient. The purpose of this paper is to propose a method for predicting the acoustic energy generated by raindrops of any diameter. Here, a formula was derived to calculate the underwater sound energy radiated by single raindrops based on a dipole radiation pattern. A series of experiments were conducted to measure the underwater sound energy in a 15 m × 9 m × 6 m reverberation tank filled with tap water. The analysis of the acoustic energy characteristics and conversion efficiency from kinetic to acoustic energy helped develop the model to predict the average underwater sound energy radiated by single raindrops. Using this model, the total underwater sound energy of all raindrops during a rainfall event can be predicted based on the drop size distribution.

Collective oscillations in bubble clouds

2011 ◽  
Vol 680 ◽  
pp. 114-149 ◽  
Author(s):  
ZORANA ZERAVCIC ◽  
DETLEF LOHSE ◽  
WIM VAN SAARLOOS
Keyword(s):  
Frequency Response ◽  
Acoustic Field ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Viscous Damping ◽  
Edge States ◽  
Bubble Cloud ◽  
Collective Oscillations ◽  
The Individual ◽  
Bubble Oscillations

In this paper the collective oscillations of a bubble cloud in an acoustic field are theoretically analysed with concepts and techniques of condensed matter physics. More specifically, we will calculate the eigenmodes and their excitabilities, eigenfrequencies, densities of states, responses, absorption and participation ratios to better understand the collective dynamics of coupled bubbles and address the question of possible localization of acoustic energy in the bubble cloud. The radial oscillations of the individual bubbles in the acoustic field are described by coupled linearized Rayleigh–Plesset equations. We explore the effects of viscous damping, distance between bubbles, polydispersity, geometric disorder, size of the bubbles and size of the cloud. For large enough clusters, the collective response is often very different from that of a typical mode, as the frequency response of each mode is sufficiently wide that many modes are excited when the cloud is driven by ultrasound. The reason is the strong effect of viscosity on the collective mode response, which is surprising, as viscous damping effects are small for single-bubble oscillations in water. Localization of acoustic energy is only found in the case of substantial bubble size polydispersity or geometric disorder. The lack of localization for a weak disorder is traced back to the long-range 1/r interaction potential between the individual bubbles. The results of the present paper are connected to recent experimental observations of collective bubble oscillations in a two-dimensional bubble cloud, where pronounced edge states and a pronounced low-frequency response had been observed, both consistent with the present theoretical findings. Finally, an outlook to future possible experiments is given.

Towards Low-NOx Operation in a Complex Burner: Optimization of an Annular Trapped Vortex Combustor

2013 ◽  
Author(s):  
Pradip Xavier ◽  
Bruno Renou ◽  
Gilles Cabot ◽  
Mourad A. Boukhalfa ◽  
Michel Cazalens
Keyword(s):  
Acoustic Energy ◽  
Combustion Instabilities ◽  
Chemical Parameters ◽  
Hot Gas ◽  
Highly Sensitive ◽  
Stable Flame ◽  
Mass Transfers ◽  
Gas Expansion ◽  
Trapped Vortex ◽  
Original Configuration

This paper focuses on optimizing an innovative annular Lean Premixed staged burner, following the Trapped Vortex Combustor concept. The latter consists of a lean main flame stabilized by passing past a rich cavity pilot flame. Unfortunately, this configuration is highly sensitive to combustion instabilities and the flame is not well stabilized. This work consists of adjusting aerodynamic variables, chemical parameters and burner geometry to reach a “low-NOx” operation while reducing other pollutants and getting a stable flame. Results show that stability is reached when mass transfers between main and cavity zones are reduced. Then, the main bulk velocity is increased to reduce the cavity thermal expansion, due to the hot gas expansion. In addition, the cavity flow rate is reduced to prevent from penetrating and disturbing the main flow. Re-arranging injections in the cavity also avoid local unsteady equivalence ratios, which creates an unsteady heat release and combustion with pulses. Regarding NOx, a leaner main flame combined with a sufficiently rich cavity mixture creates local stoichiometric zones at the interface between the cavity and the main zone. The latter point is found to be a good anchoring mechanism. Compared with the original configuration, a stable point of operation is found: acoustic energy is reduced by an order of 100, NOx level is less than 0.4 g/kgfuel, CO is cut by 93% with no more Unburned Hydro-Carbons.

scholarly journals Noninvasive neuromodulation and thalamic mapping with low-intensity focused ultrasound

2018 ◽  
Vol 128 (3) ◽  
pp. 875-884 ◽  
Author(s):  
Robert F. Dallapiazza ◽  
Kelsie F. Timbie ◽  
Stephen Holmberg ◽  
Jeremy Gatesman ◽  
M. Beatriz Lopes ◽  
...  
Keyword(s):  
Focused Ultrasound ◽  
Thalamic Nucleus ◽  
Acoustic Energy ◽  
Similar Degree ◽  
Thalamic Nuclei ◽  
Low Intensity ◽  
Tissue Heating ◽  
The Central Nervous System ◽  
Selective Mapping ◽  
Noninvasive Neuromodulation

OBJECTIVEUltrasound can be precisely focused through the intact human skull to target deep regions of the brain for stereotactic ablations. Acoustic energy at much lower intensities is capable of both exciting and inhibiting neural tissues without causing tissue heating or damage. The objective of this study was to demonstrate the effects of low-intensity focused ultrasound (LIFU) for neuromodulation and selective mapping in the thalamus of a large-brain animal.METHODSTen Yorkshire swine (Sus scrofa domesticus) were used in this study. In the first neuromodulation experiment, the lemniscal sensory thalamus was stereotactically targeted with LIFU, and somatosensory evoked potentials (SSEPs) were monitored. In a second mapping experiment, the ventromedial and ventroposterolateral sensory thalamic nuclei were alternately targeted with LIFU, while both trigeminal and tibial evoked SSEPs were recorded. Temperature at the acoustic focus was assessed using MR thermography. At the end of the experiments, all tissues were assessed histologically for damage.RESULTSLIFU targeted to the ventroposterolateral thalamic nucleus suppressed SSEP amplitude to 71.6% ± 11.4% (mean ± SD) compared with baseline recordings. Second, we found a similar degree of inhibition with a high spatial resolution (∼ 2 mm) since adjacent thalamic nuclei could be selectively inhibited. The ventromedial thalamic nucleus could be inhibited without affecting the ventrolateral nucleus. During MR thermography imaging, there was no observed tissue heating during LIFU sonications and no histological evidence of tissue damage.CONCLUSIONSThese results suggest that LIFU can be safely used to modulate neuronal circuits in the central nervous system and that noninvasive brain mapping with focused ultrasound may be feasible in humans.

Acoustic Radiation From Thick Laminated Cylindrical Shells With Sparse Cross Stiffeners

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Xiongtao Cao ◽  
Chao Ma ◽  
Hongxing Hua
Keyword(s):  
Cylindrical Shell ◽  
Radial Displacement ◽  
Acoustic Radiation ◽  
Periodic Structures ◽  
Cylindrical Shells ◽  
Acoustic Power ◽  
Acoustic Energy ◽  
Parallel Plates ◽  
Wavenumber Domain ◽  
Laminated Cylindrical Shells

A general method for predicting acoustic radiation from multiple periodic structures is presented and a numerical solution is proposed to find the radial displacement of thick laminated cylindrical shells with sparse cross stiffeners in the wavenumber domain. Although this method aims at the sound radiation from a single stiffened cylindrical shell, it can be easily adapted to analyze the vibrational and sound characteristics of two concentric cylindrical shells or two parallel plates with complicated periodic stiffeners, such as submarine and ship hulls. The sparse cross stiffeners are composed of two sets of parallel rings and one set of longitudinal stringers. The acoustic power of large cylindrical shells above the ring frequency is derived in the wavenumber domain on the basis of the fact that sound power is focused on the acoustic ellipse. It transpires that a great many band gaps of wave propagation in the helical wave spectra of the radial displacement for stiffened cylindrical shells are generated by the rings and stringers. The acoustic power and input power of stiffened antisymmetric laminated cylindrical shells are computed and compared. The acoustic energy conversion efficiency of the cylindrical shells is less than 10%. The axial and circumferential point forces can also produce distinct acoustic power. The radial displacement patterns of the antisymmetric cylindrical shell with fluid loadings are illustrated in the space domain. This study would help to better understand the main mechanism of acoustic radiation from stiffened laminated composite shells, which has not been adequately addressed in its companion paper (Cao et al., 2012, “Acoustic Radiation From Shear Deformable Stiffened Laminated Cylindrical Shells,” J. Sound Vib., 331(3), pp. 651-670).

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