Active sonic boom control

1996 ◽  
Vol 325 ◽  
pp. 1-28 ◽  
Author(s):  
Steven C. Crow ◽  
Gene G. Bergmeier
Keyword(s):  
Acoustic Waves ◽  
Pressure Field ◽  
Field Approximation ◽  
Simple Relation ◽  
Sonic Boom ◽  
Simulation Code ◽  
Sonic Booms ◽  
Supersonic Aircraft ◽  
Velocity Changes ◽  
Algebraic Term

A theory and simulation code are developed to study non-steady sources as means to control sonic booms of supersonic aircraft. A key result is that the source of sonic boom pressure is not confined to the length of the aircraft but occupies an extensive segment of the flight path. An aircraft in non-steady flight functions as a synthetic aperture antenna, generating complex acoustic waves with no simple relation to instantaneous volume or lift distributions.The theory applies linear acoustics to slender non-steady sources but requires no far-field approximation. The solution for pressure contains a term not seen in Whitham's theory for sonic booms of distant supersonic aircraft. The term describes a pressure field that decays algebraically behind the Mach cone and, in the case of steady flight, integrates to a ground load equal to the weight of the aircraft. The algebraic term is separate from those that describe the sonic boom.Two non-steady source phenomena are evaluated: periodic velocity changes (surge), and periodic longitudinal lift redistribution (slosh). Surge can attenuate a sonic boom and covert it into prolonged weak reverberation, but accelerations needed to produce the phenomenon seem too large for practical use. Slosh may be practical and can alter sonic booms but does not, on average, result in boom attenuation. The conclusion is that active sonic boom abatement is possible in theory but maybe not practical.

A correction to sonic boom theory

2009 ◽  
Vol 113 (1149) ◽  
pp. 739-745 ◽  
Author(s):  
T. Cain
Keyword(s):  
Ambient Temperature ◽  
Acoustic Impedance ◽  
Aircraft Design ◽  
Sonic Boom ◽  
Sonic Booms ◽  
Compression Waves ◽  
Supersonic Aircraft ◽  
Real Atmosphere ◽  
Weak Shocks ◽  
The Waves

Abstract Current sonic boom theory is based on linear midfield solutions coupled with acoustic propagation models. Approximate corrections are made within the theory to account for non-linearities, in particular for the coalescence of compression waves and the formation of weak shocks. A very large adjustment is made to account for the increasing acoustic impedance that the waves encounter as they propagate from the low density air at cruise altitude to the high density air at sea level. Typically this correction reduces the calculated over pressure levels by a factor of three. Here the method of characteristics (MOC) is used to prove that the density gradient within a hydrostatic atmosphere has no direct effect on the propagation or intensity of the wave. However gravity and ambient temperature both affect the wave propagation and the combined pressure level attenuation is not dissimilar to that previously attributed to acoustic impedance. Although the flawed acoustic theory has given reasonable predictions of measured sonic booms, the omission of gravity from the equation of motion and the inclusion of a false impedance modification, makes the model unreliable for prediction of future designs, particularly those focused on boom minimisation. As an aid to quiet supersonic aircraft design, Whitham’s theory is extended to include gravity and ambient temperature variation and shown to be in good agreement with a MOC solution for the real atmosphere.

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.

On sound energy scattered by a rigid body near a compliant surface

1995 ◽  
Vol 451 (1943) ◽  
pp. 543-552 ◽  
Keyword(s):  
Acoustic Waves ◽  
Specular Reflection ◽  
Simple Relation ◽  
Optical Theorem ◽  
Energy Calculation ◽  
Far Field ◽  
Sound Energy ◽  
Compliant Surface ◽  
Scattered Energy ◽  
Acoustic Media

A theorem is derived which generalizes the classical extinction theorem (also known as the optical theorem) to cases where a rigid scatterer of arbitrary shape is lo­cated near a large compliant surface which has quite general mechanical properties, including dissipation and wave-bearing features, and where the acoustic media on both sides of the compliant surface may have different densities and sound speeds. The theorem relates the sound energy scattered from incident planar acoustic waves to the far field pressure in the specular reflection direction and that in the transmis­sion direction, determined by the Snell’s law. From this simple relation, the scattered energy can be found almost trivially from the far field pressures in these two partic­ular directions; the energy calculation then completely avoids integration of energy flux over control surfaces.

Modeling of Temperature Dependence of Magnetization in TbFe Films — An Atomistic Spin Simulation Study

SPIN ◽  
2016 ◽  
Vol 06 (01) ◽  
pp. 1650003 ◽  
Author(s):  
Xiankai Jiao ◽  
Zongzhi Zhang ◽  
Yaowen Liu
Keyword(s):  
Spin Dynamics ◽  
Mean Field ◽  
Recovery Process ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Temperature Dependent ◽  
Simulation Code ◽  
Basic Physics ◽  
Temperature Dependent Properties ◽  
Strength Formula

In this paper, we performed spin simulations at atomistic level to study the temperature dependent properties of perpendicularly magnetized TbFe thin films. The crystallographically amorphous feature of TbFe ferrimagnetic alloys is modeled by using a lattice system with disordered site occupation of rare earth (RE) and transition metal (TM) spins. The simulated Curie temperature ([Formula: see text]) is consistent well with the mean-field approximation theory. With the increase of Tb concentration, the [Formula: see text] decreases almost linearly, whereas the magnetization compensation temperature ([Formula: see text]) increases gradually until the [Formula: see text] value is reached. The inter-sublattice exchange coupling strength [Formula: see text] between the RE and TM atoms can significantly affect [Formula: see text], but has less impact on [Formula: see text]. With the increase of Tb concentration, the TbFe sample of high [Formula: see text] exhibits a much faster increase in [Formula: see text] than the sample with low [Formula: see text]. Moreover, we have tested the simulation code to model the laser pulse induced ultrafast nonequilibrium spin dynamics. As an example, the femto-second pulse laser induced demagnetization and recovery process is clearly reproduced. These features are in a good agreement with the experiments, indicating that the simulation model can capture the basic physics in describing the high temperature dependent magnetic property as well as the ultrafast spin dynamics.

Meteorological Parameters Affecting Supersonic Transport Operations

1967 ◽  
Vol 20 (1) ◽  
pp. 53-63 ◽  
Author(s):  
Richard Scherhag ◽  
Gunter Warnecke ◽  
Werner Wehry
Keyword(s):  
Working Group ◽  
Meteorological Parameters ◽  
Sonic Boom ◽  
Atmospheric Ozone ◽  
Atmospheric Conditions ◽  
Atmospheric Parameters ◽  
Free Atmosphere ◽  
Supersonic Transport ◽  
Supersonic Aircraft ◽  
Initial Task

In 1965, following the Eastbourne Conference, the British, French and German Institutes of Navigation formed a Working Group to make a study of the environment in which the supersonic transport will operate and of its implications for the navigation of such aircraft. The Group's initial task has been one of education, largely through discussion of a series of papers submitted to it. Some of the papers considered have already been published in the Journal (Vol. 19) and a further selection is published below. Table I was contributed by Mr. G. E. Beck. The illustrations to these papers have not all been reproduced.1. Atmospheric Conditions. It will be useful to distinguish between different kinds of atmospheric influences on supersonic aircraft operations. They may be classed as follows:(a) Sporadic effects near the ground(b) Sporadic effects in the free atmosphere(c) Effects on sonic boom(d) Effects of atmospheric ozone(e) Permanently effective atmospheric parameters, such as temperature, density and wind.

Prediction of High Frequency Sonic Boom Noise Transmission Into Buildings Using a Hybrid Analytical-Ray Tracing Approach

2012 ◽  
Author(s):  
Joseph M. Corcoran ◽  
Marcel C. Remillieux ◽  
Ricardo A. Burdisso
Keyword(s):  
Ray Tracing ◽  
High Frequency ◽  
Acoustic Radiation ◽  
Low Frequency ◽  
Sonic Boom ◽  
Acoustic Transmission ◽  
Frequency Method ◽  
Low Frequencies ◽  
Sonic Booms ◽  
Acoustic Responses

As part of the effort to renew commercial supersonic flight, a predictive numerical tool to compute sonic boom transmission into buildings is under development. Due to the computational limitations of typical numerical methods used at low frequencies (e.g. Finite Element Method), it is necessary to develop a separate approach for the calculation of acoustic transmission and interior radiation at high frequencies. The high frequency approach can then later be combined with a low frequency method to obtain full frequency vibro-acoustic responses of buildings. An analytical method used for the computation of high frequency acoustic transmission through typical building partitions is presented in this paper. Each partition is taken in isolation and assumed to be infinite in dimension. Using the fact that a sonic boom generated far from the structure will approximate plane wave incidence, efficient analytical solutions for the vibration and acoustic radiation of different types of partitions are developed. This is linked to a commercial ray tracing code to compute the high frequency interior acoustic response and for auralization of transmitted sonic booms. Acoustic and vibration results of this high frequency tool are compared to experimental data for a few example cases demonstrating its efficiency and accuracy.

Sonic Boom Propagation in Urban Canyons

2012 ◽  
Author(s):  
Kimberly A. Riegel ◽  
Victor W. Sparrow
Keyword(s):  
Large City ◽  
Sound Field ◽  
Environmental Parameters ◽  
Field Work ◽  
Sonic Boom ◽  
Sonic Booms ◽  
Sound Levels ◽  
The People ◽  
Arrival Angles ◽  
The Impact

In order to make civilian supersonic flight over land possible, the resulting sonic boom must be acceptable to the people exposed. In order to determine the impact on people, determining the behavior of a sonic boom in a large city is critical. A combined ray tracing radiosity method was developed to propagate sonic booms into urban canyons. A variety of environmental parameters were changed to determine their effect on the resulting sound field. The arrival angles of the boom, the height of the canyons, the width of the canyons, and the amount of diffusion were all varied. It was shown that the resulting sound levels from most of these parameters was highly dependent on the combination of the parameters rather than a single parameter. Diffusion was the only parameter that showed a consistent trend in the amplitude of the sound field. [Work funded by NASA and the FAA’s PARTNER Center of Excellence.]

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