INTEGRATED RESEARCHES OF ACOUSTICAL EXPOSURE ON GAS-DUST FLOW IN THE VORTEX-ACOUSTIC DISPERSER

2016 ◽  
Vol 2 (1) ◽  
pp. 155-161 ◽  
Author(s):  
Бойчук ◽  
Igor Boychuk ◽  
Перелыгин ◽  
Dmitriy Perelygin
Keyword(s):  
Boundary Layer ◽  
Acoustic Wave ◽  
Swirling Flow ◽  
Acoustic Effect ◽  
Dispersed Flow ◽  
Acoustic Impact ◽  
Dust Flow

The article deals with the movement of gas-dispersed flow in the chamber of vortex - acoustic dis-perser. The simulation of the acoustic impact on the course of the swirling flow. It is shown that the acoustic effect for a flow leads to its inhibition. At the same time for the flow in the boundary layer takes oscillatory. Modeling has allowed to establish the nature of the distribution of acoustic oscil-lations by using single and successive acoustic wave generators, enhances the effect of braking.

Acoustic receptivity and evolution of two-dimensional and oblique disturbances in a Blasius boundary layer

2001 ◽  
Vol 432 ◽  
pp. 69-90 ◽  
Author(s):  
RUDOLPH A. KING ◽  
KENNETH S. BREUER
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Acoustic Wave ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Surface Waviness ◽  
S Wave ◽  
Boundary Layer Instability ◽  
Blasius Boundary Layer ◽  
Tollmien Schlichting

An experimental investigation was conducted to examine acoustic receptivity and subsequent boundary-layer instability evolution for a Blasius boundary layer formed on a flat plate in the presence of two-dimensional and oblique (three-dimensional) surface waviness. The effect of the non-localized surface roughness geometry and acoustic wave amplitude on the receptivity process was explored. The surface roughness had a well-defined wavenumber spectrum with fundamental wavenumber kw. A planar downstream-travelling acoustic wave was created to temporally excite the flow near the resonance frequency of an unstable eigenmode corresponding to kts = kw. The range of acoustic forcing levels, ε, and roughness heights, Δh, examined resulted in a linear dependence of receptivity coefficients; however, the larger values of the forcing combination εΔh resulted in subsequent nonlinear development of the Tollmien–Schlichting (T–S) wave. This study provides the first experimental evidence of a marked increase in the receptivity coefficient with increasing obliqueness of the surface waviness in excellent agreement with theory. Detuning of the two-dimensional and oblique disturbances was investigated by varying the streamwise wall-roughness wavenumber αw and measuring the T–S response. For the configuration where laminar-to-turbulent breakdown occurred, the breakdown process was found to be dominated by energy at the fundamental and harmonic frequencies, indicative of K-type breakdown.

The Boundary Layer Inside a Conical Surface Due to a Swirling Flow With Throughflow

1976 ◽  
Vol 43 (4) ◽  
pp. 564-566 ◽  
Author(s):  
J. M. Fabian ◽  
G. C. Oates
Keyword(s):  
Boundary Layer ◽  
Entire Range ◽  
Close Agreement ◽  
Swirling Flow ◽  
Approximate Solutions ◽  
Conical Surface

The problem of describing the boundary layer existing inside a conical surface due to the presence of a swirling flow passing through the cone is considered. Approximate solutions based upon the Karman-Polhausen method are obtained for both the laminar and the turbulent cases. The results obtained are in close agreement with known solutions previously obtained in the limits of swirl with no throughflow and throughflow with no swirl. The present results appear to be valid over the entire range of swirl to throughflow ratios.

Acoustic wave energy absorption and distributed heat sources upon an acoustic impact on media

2016 ◽  
Vol 54 (1) ◽  
pp. 56-61 ◽  
Author(s):  
G. R. Izmailova ◽  
L. A. Kovaleva ◽  
N. M. Nasyrov
Keyword(s):  
Acoustic Wave ◽  
Energy Absorption ◽  
Wave Energy ◽  
Heat Sources ◽  
Acoustic Impact

scholarly journals Suction/Injection Effects on the Swirling Flow of a Reiner-Rivlin Fluid near a Rough Surface

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Bikash Sahoo ◽  
Sébastien Poncet ◽  
Fotini Labropulu
Keyword(s):  
Boundary Layer ◽  
Boundary Conditions ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Swirling Flow ◽  
Velocity Profiles ◽  
Partial Slip ◽  
Injection Velocity ◽  
Slip Boundary Conditions ◽  
Slip Boundary

The similarity equations for the Bödewadt flow of a non-Newtonian Reiner-Rivlin fluid, subject to uniform suction/injection, are solved numerically. The conventional no-slip boundary conditions are replaced by corresponding partial slip boundary conditions, owing to the roughness of the infinite stationary disk. The combined effects of surface slip (λ), suction/injection velocity (W), and cross-viscous parameter (L) on the momentum boundary layer are studied in detail. It is interesting to find that suction dominates the oscillations in the velocity profiles and decreases the boundary layer thickness significantly. On the other hand, injection has opposite effects on the velocity profiles and the boundary layer thickness.

Thermal-Acoustic Wave Generation and Propagation Using Suspended Carbon Nanotube Thin Film in Fluidic Environments

2016 ◽  
Vol 83 (9) ◽  
Author(s):  
P. Jia ◽  
C. W. Lim
Keyword(s):  
Thin Film ◽  
Carbon Nanotube ◽  
Acoustic Wave ◽  
Power Input ◽  
Multiwall Carbon Nanotube ◽  
Analytical Prediction ◽  
Acoustic Effect ◽  
Field Solution ◽  
Analytical Approximations ◽  
Wave Response

A simplified analytical pressure solution for thermal-acoustic wave response generated by using suspended multiwall carbon nanotube (MWCNT) thin film in different fluidic environments is developed. The solution consists of two independent portions: the near-field solution and the far-field solution. The electricity power input is a key element to control the thermal-acoustic wave pressure level. The dependence of the solution on axial distance from the source origin is investigated for different fluidic environments. Comparison between analytical solutions and published experimental results is presented, and excellent agreement is reported. A number of numerical examples for different parameters are studied for various liquids and gases including air, argon, water, and ethanol. Accurate analytical approximations for the thermal-acoustic wave response, and amplitude functions for different temperatures in fluids of varying densities are proposed here. The relation of Rayleigh distance and critical frequency has been determined in order to enhance and optimize the thermal-acoustic effect and wave behavior in fluids. These two parameters can be modified by suitable choices of the size of thin film, the properties of surrounding media, etc. The thermal-acoustic generation properties including the electric power input, frequency, and the suspended MWCNT thin film size significantly affect the acoustic pressure performance. It is concluded here that this extended analytical work not only agrees better with experiment but also offers more convincing analytical prediction for the generation and propagation of thermal-acoustic wave in different fluids.

Performance and stability of the double absorbing boundary method for acoustic-wave propagation

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. T59-T72 ◽  
Author(s):  
Toby Potter ◽  
Jeffrey Shragge ◽  
David Lumley
Keyword(s):  
Boundary Layer ◽  
Wave Equation ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Spectral Response ◽  
Domain Boundary ◽  
Grid Point ◽  
High Order ◽  
Computational Domain ◽  
Absorbing Boundary

The double absorbing boundary (DAB) is a novel extension to the family of high-order absorbing boundary condition operators. It uses auxiliary variables in a boundary layer to set up cancellation waves that suppress wavefield energy at the computational-domain boundary. In contrast to the perfectly matched layer (PML), the DAB makes no assumptions about the incoming wavefield and can be implemented with a boundary layer as thin as three computational grid-point cells. Our implementation incorporates the DAB into the boundary cell layer of high-order finite-difference (FD) techniques, thus avoiding the need to specify a padding region within the computational domain. We tested the DAB by propagating acoustic waves through homogeneous and heterogeneous 3D earth models. Measurements of the spectral response of energy reflected from the DAB indicate that it reflects approximately 10–15 dB less energy for heterogeneous models than a convolutional PML of the same computational memory complexity. The same measurements also indicate that a DAB boundary layer implemented with second-order FD operators couples well with higher-order FD operators in the computational domain. Long-term stability tests find that the DAB and CPML methods are stable for the acoustic-wave equation. The DAB has promise as a robust and memory-efficient absorbing boundary for 3D seismic imaging and inversion applications as well as other wave-equation applications in applied physics.

scholarly journals Flow in the exit of open pipes during acoustic resonance

1980 ◽  
Vol 99 (2) ◽  
pp. 293-319 ◽  
Author(s):  
J. H. M. Disselhorst ◽  
L. Van Wijngaarden
Keyword(s):  
Boundary Layer ◽  
Mathematical Model ◽  
Boundary Condition ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Acoustic Radiation ◽  
Acoustic Resonance ◽  
The Other ◽  
Open Tube ◽  
Theoretical Predictions

The flow near the mouth of an open tube is examined, experimentally and theoretically, under conditions in which resonant acoustic waves are excited in the tube at the other end. If the edge of the tube is round, separation does not occur at high Strouhal numbers, which enables us to verify theoretical predictions for dissipation in the boundary layer and for acoustic radiation. Observation with the aid of schlieren pictures shows that in the case of a sharp edge vortices are formed during inflow. The vortices are shed from the pipe during outflow. Based on these observations a mathematical model is developed for the generation and shedding of vorticity. The main result of the analysis is a boundary condition for the pressure in the wave, to be applied near the mouth. The pressure amplitudes in the acoustic wave measured under resonance are compared with theoretical predictions made with the aid of the boundary condition obtained in the paper.

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