Development of analytical models for calculating the characteristics of intense acoustic waves propagating in a stratified atmosphere

2021 ◽  
Vol 149 (4) ◽  
pp. A74-A74
Author(s):  
Vladimir A. Gusev ◽  
Denis A. Zharkov
Keyword(s):  
Acoustic Waves ◽  
Analytical Models

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.

scholarly journals Acoustic fields and microfluidic patterning around embedded micro-structures subject to surface acoustic waves

Soft Matter ◽  
2019 ◽  
Vol 15 (43) ◽  
pp. 8691-8705 ◽  
Author(s):  
David J. Collins ◽  
Richard O’Rorke ◽  
Adrian Neild ◽  
Jongyoon Han ◽  
Ye Ai
Keyword(s):  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Analytical Models ◽  
Acoustic Fields ◽  
Micro Structures ◽  
Microfluidic Patterning

Interactions between substrate waves and microchannel walls generate spatially localized periodic acoustic forces for microscale patterning activities. We develop analytical models that can be readily applied to predict this periodicity.

The vibrational response of a fluid-loaded baffled plate near a free surface

2021 ◽  
Vol 263 (2) ◽  
pp. 4502-4510
Author(s):  
Jamie Kha
Keyword(s):  
Free Surface ◽  
Flat Plate ◽  
Acoustic Waves ◽  
Numerical Models ◽  
Equations Of Motion ◽  
Analytical Models ◽  
Fluid Loading ◽  
Infinite Domain ◽  
Vibrational Response ◽  
Admissible Functions

An analytical model to predict the vibrational response of a simply supported rectangular plate embedded in an infinite baffle with an upper free surface under heavy fluid loading and excited by a point force is presented. The equations of motion of a thin plate are solved using­­­­­­ modal decomposition technique by employing admissible functions for an in-vacuo plate and by directly solving the Helmholtz equation for acoustic waves in a fluid. The vibrational response for a flat plate in an infinite baffle and unbounded domain (semi-infinite domain) using analytical formulation available in literature is initially computed. These results are then compared against present results to observe the effect of a free surface. Predictions from analytical models are validated by comparison with results obtained by numerical models. The proposed analytical approach presents a novel formulation to describe a fluid-loaded flat plate in a waveguide and an efficient method for predicting its vibrational response.

scholarly journals Measurement of Transfer Matrices and Source Terms of Premixed Flames

1999 ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Bruno Schuermans ◽  
Wolfgang Polifke ◽  
Oscar Mattson
Keyword(s):  
Gas Turbine ◽  
Transfer Matrix ◽  
Acoustic Waves ◽  
Combustion Process ◽  
The State ◽  
Acoustic Properties ◽  
Analytical Models ◽  
State Variables ◽  
Thermoacoustic Properties ◽  
Gas Turbine Burner

An experimental method to determine the thermoacoustic properties of a gas turbine combustor using a lean-premixed low emission swirl stabilized burner is presented. To model thermoacoustic oscillations, a combustion system can be described as a network of acoustic elements, representing for example fuel and air supply, burner and flame, combustor, cooling channels, suitable terminations, etc. For most of these elements, simple analytical models provide an adequate description of their thermoacoustic properties. However, the complex response of burner and flame (involving a three-dimensional flow field, recirculation zones, flow instabilities and heat release) to acoustic perturbations has — at least in a first step — to be determined by experiment. In our approach, we describe the burner as an active acoustical two-port, where the state variables pressure and velocity at the inlet and the outlet of the two port are coupled via a four element transfer matrix. This approach is similar to the “black box” theory in communication engineering. To determine all four transfer matrix coefficients, two test states, which are independent in the state vectors, have to be created. This is achieved by using acoustic excitation by loudspeakers upstream and downstream of the burner, respectively. In addition, the burner might act as an acoustic source, emitting acoustic waves due to an unsteady combustion process. The source characteristics were determined by using a third test state, which again must be independent from the two other state vectors. In application to a full size gas turbine burner, the method’s accuracy was tested in a first step without combustion and the results were compared to an analytical model for the burner’s acoustic properties. Then the method was used to determine the burner transfer matrix with combustion. An experimental swirl stabilized premixed gas-turbine burner was used for this purpose. The treatment of burners as acoustic two-ports with feedback including a source term and the experimental determination of the burner transfer matrix is novel.

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.

scholarly journals Measurement of Transfer Matrices and Source Terms of Premixed Flames

2002 ◽  
Vol 124 (2) ◽  
pp. 239-247 ◽  
Author(s):  
C. O. Paschereit ◽  
B. Schuermans ◽  
W. Polifke ◽  
O. Mattson
Keyword(s):  
Gas Turbine ◽  
Transfer Matrix ◽  
Acoustic Waves ◽  
Combustion Process ◽  
The State ◽  
Acoustic Properties ◽  
Analytical Models ◽  
State Variables ◽  
Thermoacoustic Properties ◽  
Gas Turbine Burner

An experimental method to determine the thermoacoustic properties of a gas turbine combustor using a lean-premixed low emission swirl stabilized burner is presented. To model thermoacoustic oscillations, a combustion system can be described as a network of acoustic elements, representing for example fuel and air supply, burner and flame, combustor, cooling channels, suitable terminations, etc. For most of these elements, simple analytical models provide an adequate description of their thermoacoustic properties. However, the complex response of burner and flame (involving a three-dimensional flow field, recirculation zones, flow instabilities, and heat release) to acoustic perturbations has—at least in a first step—to be determined by experiment. In our approach, we describe the burner as an active acoustical two-port, where the state variables pressure and velocity at the inlet and the outlet of the two port are coupled via a four element transfer matrix. This approach is similar to the “black box” theory in communication engineering. To determine all four transfer matrix coefficients, two test states, which are independent in the state vectors, have to be created. This is achieved by using acoustic excitation by loudspeakers upstream and downstream of the burner, respectively. In addition, the burner might act as an acoustic source, emitting acoustic waves due to an unsteady combustion process. The source characteristics were determined by using a third test state, which again must be independent from the two other state vectors. In application to a full size gas turbine burner, the method’s accuracy was tested in a first step without combustion and the results were compared to an analytical model for the burner’s acoustic properties. Then the method was used to determine the burner transfer matrix with combustion. An experimental swirl stabilized premixed gas turbine burner was used for this purpose. The treatment of burners as acoustic two-ports with feedback including a source term and the experimental determination of the burner transfer matrix is novel.

scholarly journals Contactless Picking of Objects Using an Acoustic Gripper

Actuators ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 70
Author(s):  
Marc Röthlisberger ◽  
Marcel Schuck ◽  
Laurenz Kulmer ◽  
Johann W. Kolar
Keyword(s):  
Acoustic Waves ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Acoustic Power ◽  
Analytical Models ◽  
Acoustic Levitation ◽  
Medium Density ◽  
Mechanical Contact ◽  
Industrial Use ◽  
Reflective Surfaces

Acoustic levitation forces can be used to manipulate small objects and liquids without mechanical contact or contamination. This work presents analytical models based on which concepts for the controlled insertion of objects into the acoustic field are developed. This is essential for the use of acoustic levitators as contactless robotic grippers. Three prototypes of such grippers are implemented and used to experimentally verify the lifting of objects into an acoustic pressure field. Lifting of high-density objects (ρ > 7 g/cm3) from acoustically transparent surfaces is demonstrated using a double-sided acoustic gripper that generates standing acoustic waves with dynamically adjustable acoustic power. A combination of multiple acoustic traps is used to lift lower density objects (ρ≤0.25g/cm3) from acoustically reflective surfaces using a single-sided arrangement. Furthermore, a method that uses standing acoustic waves and thin reflectors to lift medium-density objects (ρ≤1g/cm3) from acoustically reflective surfaces is presented. The provided results open up new possibilities for using acoustic levitation in robotic grippers, which has the potential to be applied in a variety of industrial use cases.

Characterization of RF Sputtered ZnO Piezoelectric Films Using Transmission Electron Microscope

1975 ◽  
Vol 33 ◽  
pp. 86-87
Author(s):  
Kemining W. Yeh ◽  
Richard S. Muller ◽  
Wei-Kuo Wu ◽  
Jack Washburn
Keyword(s):  
Integrated Circuit ◽  
Acoustic Waves ◽  
New Technology ◽  
Surface Acoustic Waves ◽  
Electromechanical Properties ◽  
Leading Role ◽  
Saw Devices ◽  
Transmission Electron ◽  
High Degree

Considerable and continuing interest has been shown in the thin film transducer fabrication for surface acoustic waves (SAW) in the past few years. Due to the high degree of miniaturization, compatibility with silicon integrated circuit technology, simplicity and ease of design, this new technology has played an important role in the design of new devices for communications and signal processing. Among the commonly used piezoelectric thin films, ZnO generally yields superior electromechanical properties and is expected to play a leading role in the development of SAW devices.

Attenuation of surface acoustic waves by quantum dots

1998 ◽  
Vol 77 (5) ◽  
pp. 1195-1202
Author(s):  
Andreas Knabchen Yehoshua, B. Levinson, Ora
Keyword(s):  
Quantum Dots ◽  
Acoustic Waves ◽  
Surface Acoustic Waves
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