Scattering and Generation of Acoustic Energy by a Premix Swirl Burner

2007 ◽  
Author(s):  
Alexander Gentemann ◽  
Wolfgang Polifke
Keyword(s):  
Experimental Data ◽  
Acoustic Waves ◽  
Narrow Range ◽  
Scattering Matrix ◽  
Acoustic Energy ◽  
Analytical Models ◽  
Design Strategies ◽  
Swirl Burner ◽  
Burner Design ◽  
Acoustic Stability

The scattering and generation of acoustic energy by a premix swirl burner is scrutinized. The analysis is formulated in terms of the scattering matrix of the burner, determined by a combination of computational fluid dynamics and system identification as well as experiment supplemented with simple analytical models for flame frequency response and burner transfer matrix. Remarkably, it is found that in a narrow range of frequencies, incoming acoustic waves are amplified strongly by the unsteady heat release, i.e. acoustic energy is generated. Although the computational and experimental data were obtained for one specific swirl burner design, further analysis suggests that such behavior should be common for many burner designs. Consequences for thermo-acoustic stability as well as burner and combustor design strategies are discussed.

LES-Based Scattering Matrix Method for Low-Order Acoustic Network Models

2017 ◽  
Author(s):  
Changjin Yoon ◽  
Owen Graham ◽  
Fei Han ◽  
Kwanwoo Kim ◽  
Katsuo Maxted ◽  
...  
Keyword(s):  
Experimental Data ◽  
Phase Angle ◽  
Traveling Wave ◽  
Matrix Method ◽  
Scattering Matrix ◽  
Acoustic Energy ◽  
Upstream Region ◽  
Downstream Region ◽  
Scattering Matrices ◽  
Scattering Matrix Method

The identification of scattering matrix method is conducted using high fidelity Large Eddy Simulations. From a series of LES results, the scattering matrices of a plain orifice and a lean premixed nozzle are evaluated and compared with the corresponding experimental data. It is confirmed that LES simulations are capable of predicting the acoustic scattering matrix, with some limitations. The magnitude of the scattering matrices imply that the acoustic energy transfer across the orifice and mixer agree fairly well with that of the scattering matrices from the experimental data. Moreover, the phase angle of transmission/reflection elements for the traveling wave in the upstream region consistently follows the experimental trends. The phase angle of transmission/reflection elements for traveling waves in the downstream region, however, shows a significant discrepancy with the experimental measurements. For the direct use of the LES-based scattering matrix method, the accuracy of determination of the phase angle of reflection/transmission of the traveling wave in the downstream region needs further study.

scholarly journals Experimental demonstration of negative refraction with 3D locally resonant acoustic metafluids

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Benoit Tallon ◽  
Artem Kovalenko ◽  
Olivier Poncelet ◽  
Christophe Aristégui ◽  
Olivier Mondain-Monval ◽  
...  
Keyword(s):  
Experimental Data ◽  
Yield Stress ◽  
Multiple Scattering ◽  
Silicone Rubber ◽  
Acoustic Waves ◽  
Scattering Theory ◽  
Negative Refraction ◽  
Volume Fraction ◽  
Experimental Demonstration ◽  
Acoustic Beam

AbstractNegative refraction of acoustic waves is demonstrated through underwater experiments conducted at ultrasonic frequencies on a 3D locally resonant acoustic metafluid made of soft porous silicone-rubber micro-beads suspended in a yield-stress fluid. By measuring the refracted angle of the acoustic beam transmitted through this metafluid shaped as a prism, we determine the acoustic index to water according to Snell’s law. These experimental data are then compared with an excellent agreement to calculations performed in the framework of Multiple Scattering Theory showing that the emergence of negative refraction depends on the volume fraction $$\Phi$$ Φ of the resonant micro-beads. For diluted metafluid ($$\Phi =3\%$$ Φ = 3 % ), only positive refraction occurs whereas negative refraction is demonstrated over a broad frequency band with concentrated metafluid ($$\Phi =17\%$$ Φ = 17 % ).

scholarly journals Automated Insertion of Objects Into an Acoustic Robotic Gripper

Proceedings ◽  
2020 ◽  
Vol 64 (1) ◽  
pp. 40
Author(s):  
Marc Röthlisberger ◽  
Marcel Schuck ◽  
Laurenz Kulmer ◽  
Johann W. Kolar
Keyword(s):  
Acoustic Field ◽  
Acoustic Waves ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Acoustic Power ◽  
Industrial Applications ◽  
High Density ◽  
Analytical Models ◽  
Acoustic Levitation ◽  
Mechanical Contact

Acoustic levitation forces can be used to manipulate small objects and liquid without mechanical contact or contamination. To use acoustic levitation for contactless robotic grippers, automated insertion of objects into the acoustic pressure field is necessary. This work presents analytical models based on which concepts for the controlled insertion of objects are developed. Two prototypes of acoustic grippers are implemented and used to experimentally verify the lifting of objects into the acoustic field. Using standing acoustic waves and by dynamically adjusting the acoustic power, the lifting of high-density objects (>7 g/cm3) from acoustically transparent surfaces is demonstrated. Moreover, a combination of different acoustic traps is used to lift lower-density objects from acoustically reflective surfaces. The provided results open up new possibilities for the implementation of acoustic levitation in robotic grippers, which have the potential to be used in a variety of industrial applications.

Laser-Induced Acoustic Waves for Measurement and Imaging

2000 ◽  
Author(s):  
Wen Li ◽  
Ronald A. Roy ◽  
Robin O. Cleveland ◽  
Lawrence J. Berg ◽  
Charles A. DiMarzio
Keyword(s):  
Acoustic Waves ◽  
Peak Power ◽  
Laser Light ◽  
Short Pulse ◽  
Laser Wavelength ◽  
Acoustic Imaging ◽  
Acoustic Energy ◽  
High Peak Power ◽  
First Case ◽  
Very High

Abstract A short pulse of laser light can act as a source of acoustic energy for acoustic imaging. Although there are a number of mechanisms by which the light pulse may generate sound, all require a pulse of high peak power density and short duration. In this work, we address examples where the material is highly absorbing at the laser wavelength, and the sound is generated near the surface. In these cases, there exist two different mechanisms which can convert the light to sound. The first is heating followed by expansion, and the second is generation of a plasma in the air above the surface. In the first case, sound generation occurs in the medium of interest and the energy efficiency can be very high, in the sense that no reflection losses occur. We present two applications from our own research.

Laser-Based Ultrasound Interrogation of Surface and Sub-Surface Features in Advanced Manufacturing Materials

2021 ◽  
Author(s):  
Kathryn Jinae Harke ◽  
Nicholas Calta ◽  
Joseph Tringe ◽  
David Stobbe
Keyword(s):  
Acoustic Waves ◽  
Surface Defects ◽  
Surface Acoustic Waves ◽  
Acoustic Energy ◽  
Advanced Manufacturing ◽  
Powder Bed ◽  
Surface Features ◽  
Performance Targets ◽  
All Optical ◽  
X Ray Computed

Abstract Structures formed by advanced manufacturing methods increasingly require nondestructive characterization to enable efficient fabrication and to ensure performance targets are met. This is especially important for aerospace, military, and high precision applications. Surface acoustic waves (SAW) generated by laser-based ultrasound can detect surface and sub-surface defects relevant for a broad range of AM processes, including laser powder bed fusion (LPBF). In particular, an all-optical SAW generation and detection configuration can effectively interrogate laser melt lines. Here we report on scattered acoustic energy from melt lines, voids, and surface features. Sub-surface voids are also characterized using X-ray Computed Tomography (CT). High resolution CT results are presented and compared with SAW measurements. Finite difference simulations inform experimental measurements and analysis.

Small Horizontal Axis Wind Turbine: Analytical Blade Design and Comparison With RANS-Prediction and First Experimental Data

2013 ◽  
Author(s):  
Tom Gerhard ◽  
Michael Sturm ◽  
Thomas H. Carolus
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Wind Turbine ◽  
Horizontal Axis ◽  
Analytical Models ◽  
Power Coefficient ◽  
Analysis Tool ◽  
Computational Domain ◽  
Horizontal Axis Wind Turbine ◽  
Data Set

State-of-the-art wind turbine performance prediction is mainly based on semi-analytical models, incorporating blade element momentum (BEM) analysis and empirical models. Full numerical simulation methods can yield the performance of a wind turbine without empirical assumptions. Inherent difficulties are the large computational domain required to capture all effects of the unbounded ambient flow field and the fact that the boundary layer on the blade may be transitional. A modified turbine design method in terms of the velocity triangles, Euler’s turbine equation and BEM is developed. Lift and drag coefficients are obtained from XFOIL, an open source 2D design and analysis tool for subcritical airfoils. A 3 m diameter horizontal axis wind turbine rotor was designed and manufactured. The flow field is predicted by means of a Reynolds-averaged Navier-Stokes simulation. Two turbulence models were utilized: (i) a standard k-ω-SST model, (ii) a laminar/turbulent transition model. The manufactured turbine is placed on the rooftop of the University of Siegen. Three wind anemometers and wind direction sensors are arranged around the turbine. The torque is derived from electric power and the rotational speed via a calibrated grid-connected generator. The agreement between the analytically and CFD-predicted kinematic quantities up- and downstream of the rotor disc is quite satisfactory. However, the blade section drag to lift ratio and hence the power coefficient vary with the turbulence model chosen. Moreover, the experimentally determined power coefficient is considerably lower as predicted by all methods. However, this conclusion is somewhat preliminary since the existing experimental data set needs to be extended.

scholarly journals Моделирование проводимости Капицы через шероховатые интерфейсы между твердыми телами

2021 ◽  
Vol 63 (7) ◽  
pp. 982
Author(s):  
Б. Лю ◽  
В.И. Хвесюк ◽  
А.А. Баринов
Keyword(s):  
Experimental Data ◽  
Theoretical Prediction ◽  
Transmission Coefficient ◽  
Wide Temperature Range ◽  
Acoustic Waves ◽  
Theoretical Method ◽  
Interface Roughness ◽  
Kapitza Conductance ◽  
Acoustic Mismatch ◽  
The Difference

In this work, we have formulated and solved the problem of determining the Kapitza conductance across the interface between two solids, taking into account the interface roughness. We use a modified acoustic mismatch model (AMM). The difference from the classic model is that the dispersion properties of acoustic waves are considered. A significant advantage of this model is that the theoretical prediction agrees well with experimental data over a wide temperature range: from 30K to more than 300K. Finally, a theoretical method with the statistical distribution of roughness profiles is used to determine the energy transmission coefficient across the interface.

scholarly journals Approximate Analytical Models of Shock-Wave Structure at Steady Mach Reflection

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 305
Author(s):  
Mikhail V. Chernyshov ◽  
Karina E. Savelova ◽  
Anna S. Kapralova
Keyword(s):  
Experimental Data ◽  
Shock Wave ◽  
Comparative Analysis ◽  
Analytical Model ◽  
Mach Reflection ◽  
Supersonic Jet ◽  
Wave Structure ◽  
Analytical Models ◽  
Analytical Prediction ◽  
Shock Wave Structure

In this study, we obtain the comparative analysis of methods of quick approximate analytical prediction of Mach shock height in planar steady supersonic flows (for example, in supersonic jet flow and in narrowing channel between two wedges), that are developed since the 1980s and being actively modernized now. A new analytical model based on flow averaging downstream curved Mach shock is proposed, which seems more accurate than preceding models, comparing with numerical and experimental data.

scholarly journals Using Bayesian Model Selection to Advise Neutron Reflectometry Analysis from Langmuir-Blodgett Monolayers

2019 ◽  
Author(s):  
Andrew McCluskey ◽  
Tom Arnold ◽  
Joshaniel F. K. Cooper ◽  
Tim Snow
Keyword(s):  
Experimental Data ◽  
Soft Matter ◽  
General Framework ◽  
Neutron Reflectometry ◽  
Analytical Models ◽  
Colloid Interface ◽  
X Ray ◽  
Langmuir Blodgett ◽  
Generic Framework

The analysis of neutron and X-ray reflectometry data is important for the study of interfacial soft matter structures. However, there is still substantial discussion regarding the analytical models<br>that should be used to rationalise relflectometry data. In this work, we outline a robust and generic framework for the determination of the evidence for a particular model given experimental data, by<br>applying Bayesian logic. We apply this framework to the study of Langmuir-Blodgett monolayers by considering three possible analytical models from a recently published investigation [Campbell et al., J. Colloid Interface Sci, 2018, 531, 98]. From this, we can determine which model has the most evidence given the experimental data, and show the effect that different isotopic contrasts of neutron reflectometry will have on this. We believe that this general framework could become an important component of neutron and X-ray reflectometry data analysis, and hope others more regularly consider the relative evidence for their analytical models.<br>

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