Abstract:The sinuous instability wave of a planar air jet is excited by localized acoustic flow across the nozzle. Phase velocity and the growth exponent are found from synchronous hot-wire measurements made beyond the excited region, where the profile is approximately sech-squared. In the observed range of scaled radian frequency, 0.02-1.33 (the stability limit), results agree with real-frequency (spatially growing) analysis but not with complex-frequency (temporally growing) analysis. The latter predicts smaller phas… Show more
“…i v i v ac i; P VX ¼ hS w v ac Dp los i; (28) where h Á i indicates averaging over a period. The three contributions are plotted on Fig.…”
Section: Discussionmentioning
confidence: 99%
“…This eigenvalue problem can be solved numerically for more realistic velocity profile 27 including the traditional Bickley profile. Nolle 28 conducted the resolution for a family of profiles:…”
Section: B Amplification and Convection Of Perturbations Of The Jetmentioning
Based on results from the literature, a description of sound generation in a recorder is developed. Linear and non-linear analysis are performed to study the dependence of the frequency on the jet velocity. The linear analysis predicts that the frequency is a function of the jet velocity. The non-linear resolution provides information about limit cycle oscillation and hysteretic regime change thresholds. A comparison of the frequency between linear theory and experiments on a modified recorder shows good agreement except at very low jet velocities. Although the predicted threshold for the onset of the first regime shows an important deviation from experiments, the hysteresis of threshold to higher regimes is accurately estimated. Furthermore, a qualitative analysis of the influence of different parameters in the model on the sound generation and regime changes is presented.
“…i v i v ac i; P VX ¼ hS w v ac Dp los i; (28) where h Á i indicates averaging over a period. The three contributions are plotted on Fig.…”
Section: Discussionmentioning
confidence: 99%
“…This eigenvalue problem can be solved numerically for more realistic velocity profile 27 including the traditional Bickley profile. Nolle 28 conducted the resolution for a family of profiles:…”
Section: B Amplification and Convection Of Perturbations Of The Jetmentioning
Based on results from the literature, a description of sound generation in a recorder is developed. Linear and non-linear analysis are performed to study the dependence of the frequency on the jet velocity. The linear analysis predicts that the frequency is a function of the jet velocity. The non-linear resolution provides information about limit cycle oscillation and hysteretic regime change thresholds. A comparison of the frequency between linear theory and experiments on a modified recorder shows good agreement except at very low jet velocities. Although the predicted threshold for the onset of the first regime shows an important deviation from experiments, the hysteresis of threshold to higher regimes is accurately estimated. Furthermore, a qualitative analysis of the influence of different parameters in the model on the sound generation and regime changes is presented.
“…The delay τ , introduced by the duration of convection of the initial perturbation η 0 along the jet, is related both to the distance W and to the convection velocity c v of transversal perturbations on the jet: τ = W cv . Both theoretical and experimental results [27,28,29] have shown that c v is related to the jet velocity itself through: c v ≈ 0.4U j .…”
Section: Amplification and Convection Of The Perturbations Along The Jetmentioning
In this paper we exploit the method of numerical continuation combined with orthogonal collocation to determine the steady-state oscillations of a model of flute-like instruments that is formulated as a nonlinear neutral delay differential equation. The delay term in the model causes additional complications in the analysis of the behaviour of the model, in contrast to models of other wind instruments which are formulated as ordinary differential equations. Fortunately, numerical continuation provides bifurcation diagrams that show branches of stable and unstable static and periodic solutions of the model and their connections at bifurcations, thus enabling an in depth analysis of the global dynamics. Furthermore, it allows us to predict the thresholds of the different registers of the flute-like instrument and thus to explain the classical phenomenon of register change and the associated hysteresis.
“…Many of these questions can be settled only by detailed experiments such as those of Thwaites and Fletcher. The most recent studies by Nolle [29] sugupon the jet, the phase delay for propagation along the jet, and phase shift involved in the interaction of the jet flow with internal acoustic waves in the pipe. In total these must sum to 2π for the feedback loop to close.…”
Abstract:Progress made over the past decade in understanding the mechanisms of sound production in music wind instruments is reviewed. The behavior of air columns, horns, and fingerholes is now fairly well understood, and most recent interest centers on details of the sound generator -the reed in woodwinds, the lips in brass instruments, and the air jet in flute-family instruments. Not only do these generators produce the sound, but they are also largely responsible, through their nonlinearity, for controlling the harmonic content and thus the musical timbre of the instrument, the one major exception being in loud playing on brass instruments where propagation nonlinearities in the air column are also important. Despite considerable progress, there remain important and interesting questions to be answered.
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