Acoustic simulation

An in vitro investigation into the bactericidal effects of a dental ultrasonic descaler on bacterial biofilms using Actinobacillus actinomycctcmcomitans and Porphyromonas gin-givalis has been reported [49]. Suspensions of the bacteria were subjected to the vibrations of a Cavitron PI insert for 2.5 and 5.0 min in an acoustically-simulated model substrate. A 60 % kill rate was achieved at a temperature of around 50 °C which constituted an alternative treatment for bacterial biofilms. This study suggested that a similar approach could be used in the clean-up of a range of biofQms considered to be the cause of a range of environmental hazards. 

These assembly models can be used to perform analysis to assess if the components can be assembled and fit together as well as for simulating the dynamics of the product. For example, finite element analysis (FEA) can also be performed on the components and assemblies to assess their strength alternatively, e.g., acoustic simulation or flow simulations are possible. 

Nowadays it is possible to design acoustic environment and room acoustic simulations using various programs, as such CATT Acoustic, Izofonik, Androl-noise 1.0. 

We used the concept of sound velocity dispersion for explanation of the shift of pulse energy spectrum maximum, transmitted through the medium, and correlation of the shift value with function of medium heterogeneity. This approach gives the possibility of mathematical simulation of the influence of both medium parameters and ultrasonic field parameters on the nature of acoustic waves propagation in a given medium. 

A similar acoustic technique was applied by Pickles and Bittleston (1983) to investigate blast produced by an elongated, or cigar-shaped, cloud. The cloud was modeled as an ellipsoid with an aspect ratio of 10. The explosion was simulated by a continuous distribution of volume sources along the main axis with a strength proportional to the local cross-sectional area of the ellipsoid. The blast produced by such a vapor cloud explosion was shown to be highly directional along the main axis. 

Piping and filter systems designed by acoustical principles, using a simulation technique on an analog computer. 

In Fig. 1.1, the parameter space for transient and stable cavitation bubbles is shown in R0 (ambient bubble radius) - pa (acoustic amplitude) plane [15]. The ambient bubble radius is defined as the bubble radius when an acoustic wave (ultrasound) is absent. The acoustic amplitude is defined as the pressure amplitude of an acoustic wave (ultrasound). Here, transient and stable cavitation bubbles are defined by their shape stability. This is the result of numerical simulations of bubble pulsations. Above the thickest line, bubbles are those of transient cavitation. Below the thickest line, bubbles are those of stable cavitation. Near the left upper side, there is a region for bubbles of high-energy stable cavitation designated by Stable (strong nf0) . In the brackets, the type of acoustic cavitation noise is indicated. The acoustic cavitation noise is defined as acoustic emissions from... 

Fig. 1.1 The regions for transient cavitation bubbles and stable cavitation bubbles when they are defined by the shape stability of bubbles in the parameter space of ambient bubble radius (R0) and the acoustic amplitude (p ). The ultrasonic frequency is 515 kHz. The thickest line is the border between the region for stable cavitation bubbles and that for transient ones. The type of bubble pulsation has been indicated by the frequency spectrum of acoustic cavitation noise such as nf0 (periodic pulsation with the acoustic period), nfo/2 (doubled acoustic period), nf0/4 (quadrupled acoustic period), and chaotic (non-periodic pulsation). Any transient cavitation bubbles result in the broad-band noise due to the temporal fluctuation in the number of bubbles. Reprinted from Ultrasonics Sonochemistry, vol. 17, K.Yasui, T.Tuziuti, J. Lee, T.Kozuka, A.Towata, and Y. Iida, Numerical simulations of acoustic cavitation noise with the temporal fluctuation in the number of bubbles, pp. 460-472, Copyright (2010), with permission from Elsevier...

Hatanaka et al. [50], Didenko and Suslick [51], and Koda et al. [52] reported the experiment of chemical reactions in a single-bubble system called single-bubble sonochemistry. Didenko and Suslick [51] reported that the amount of OH radicals produced by a single bubble per acoustic cycle was about 10s 106 molecules at 52 kHz and 1.3 1.55 bar in ultrasonic frequency and pressure amplitude, respectively. The result of a numerical simulation shown in Fig. 1.4 [43] is under the condition of the experiment of Didenko and Suslick [51]. The amount of OH... 

Yasui K, Tuziuti T, Lee J, Kozuka T, Towata A, Iida Y (2010) Numerical simulations of acoustic cavitation noise with the temporal fluctuation in the number of bubbles. Ultrason Sonochem 17 460-472... 

Bnlk wave devices have different tolerances and recently Capelle, Zarka and co-workers have studied bulk waves in qnartz resonators and used stroboscopy to identify unwanted modes associated with defects. They have also performed tine section topography in stroboscopic mode to identify if the interaction between a dislocation and the acoustic wave could be described by simple linear piezoelectric theory. Using simulation of the section topographs to analyse the data, they conclnded that a non-Unear interaction was present near to the dislocation line, linear theory working satisfactorily in the region far from the defect. Etch channels appeared to have more inflnence on the acoustic wave than individnal dislocations. 

The geometry of the ramjet system simulated is shown in Fig. 7.1, which consists of a cylindrical inlet connected to a central dump combustor that has an exhaust nozzle. This specific geometry was chosen because extensive studies have been made in the past of the interaction between acoustics, vorticity dynamics, and chemical energy release in this system [17-20]. These earlier gas-phase flow studies are very helpful in interpreting the current multiphase flow simulations. 

Based on the initial studies of unforced flows described above, inflow was selectively perturbed to investigate if the amount of particle dispersion and the location of enhanced dispersion within the combustor can be shifted as desired. Calculations were performed in which an acoustic perturbation was imposed from the back wall of the combustor with an amplitude of 0.5% of the initial chamber pressure and a frequency of 1380 Hz, 690 Hz, or 145 Hz, the characteristic frequencies of the system under study. The vortex-shedding frequency was 1380 Hz, the first-merging frequency was 690 Hz, and 145 Hz was the quarter-wave mode of the inlet. In addition, simulations were also performed with forcing at a frequency unrelated to the system, 1000 Hz. The particle size chosen for these simulations was 15 pm in diameter (St = 0.97), since this size particles were found to be optimally dispersed in the unforced flow case. All other parameters remain unchanged from the unforced case discussed above. 

Kailasanath, K., J.H. Gardner, J. P. Boris, and E. S. Oran. 1987. Numerical simulations of acoustic-vortex interactions in a central-dump ramjet combustor. J. Propulsion Power 3 525-33. 

Amidoxime-Functionalized Coatings for Surface Acoustic Wave Detection of Simulant Vapors... 

This paper has discussed algorithms for rendering reverberation in real-time. A straightforward method for simulating room acoustics is to sample a room impulse response and render the reverberation using convolution. Synthetic impulse responses can be created using auralization techniques. The availability of efficient, zero delay convolution algorithms make this a viable method for real-time room simulation. The drawback of this method is the lack of parameterized control over perceptually salient characteristics of the reverberation. This can be a problem when we attempt to use these systems in interactive virtual environments. 

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