Weakfish sonic muscle: influence of size, temperature and season

2002 ◽  
Vol 205 (15) ◽  
pp. 2183-2188 ◽  
Author(s):  
M. A. Connaughton ◽  
M. L. Fine ◽  
M. H. Taylor
Keyword(s):  
Natural Frequency ◽  
Pulse Duration ◽  
Dominant Frequency ◽  
Forced Response ◽  
Acoustic Energy ◽  
Honest Signal ◽  
Muscle Twitch ◽  
Cross Sectional ◽  
Fish Size ◽  
Sonic Muscle

SUMMARYThe influence of temperature, size and season on the sounds produced by the sonic muscles of the weakfish Cynoscion regalis are categorized and used to formulate a hypothesis about the mechanism of sound generation by the sonic muscle and swimbladder. Sounds produced by male weakfish occur at the time and location of spawning and have been observed in courtship in captivity. Each call includes a series of 6-10 sound pulses, and each pulse expresses a damped, 2-3 cycle acoustic waveform generated by single simultaneous twitches of the bilateral sonic muscles. The sonic muscles triple in mass during the spawning season, and this hypertrophy is initiated by rising testosterone levels that trigger increases in myofibrillar and sarcoplasmic cross-sectional area of sonic muscle fibers. In response to increasing temperature, sound pressure level (SPL), dominant frequency and repetition rate increase, and pulse duration decreases. Likewise, SPL and pulse duration increase and dominant frequency decreases with fish size. Changes in acoustic parameters with fish size suggest the possibility that drumming sounds act as an `honest' signal of male fitness during courtship. These parameters also correlate with seasonally increasing sonic muscle mass. We hypothesize that sonic muscle twitch duration rather than the resonant frequency of the swimbladder determines dominant frequency. The brief (3.5 ms), rapidly decaying acoustic pulses reflect a low-Q, broadly tuned resonator, suggesting that dominant frequency is determined by the forced response of the swimbladder to sonic muscle contractions. The changing dominant frequency with temperature in fish of the same size further suggests that frequency is not determined by the natural frequency of the bladder because temperature is unlikely to affect resonance. Finally, dominant frequency correlates with pulse duration (reflecting muscle twitch duration),and the inverse of the period of the second cycle of acoustic energy approximates the recorded frequency. This paper demonstrates for the first time that the dominant frequency of a fish sound produced by a single muscle twitch is apparently determined by the velocity of the muscle twitch rather than the natural frequency of the swimbladder.

Effects of fish size and temperature on weakfish disturbance calls: implications for the mechanism of sound generation

2000 ◽  
Vol 203 (9) ◽  
pp. 1503-1512 ◽  
Author(s):  
M.A. Connaughton ◽  
M.H. Taylor ◽  
M.L. Fine
Keyword(s):  
Pulse Duration ◽  
Sound Pressure Level ◽  
Repetition Rate ◽  
Sound Pressure ◽  
Peak Frequency ◽  
Dominant Frequency ◽  
Pressure Level ◽  
Sound Pulse ◽  
Muscle Twitch ◽  
Different Temperatures

To categorize variation in disturbance calls of the weakfish Cynoscion regalis and to understand their generation, we recorded sounds produced by different-sized fish, and by similar-sized fish at different temperatures, as well as muscle electromyograms. Single, simultaneous twitches of the bilateral sonic muscles produce a single sound pulse consisting of a two- to three-cycle acoustic waveform. Typical disturbance calls at 18 degrees C consist of trains of 2–15 pulses with a sound pressure level (SPL) of 74 dB re 20 microPa at 10 cm, a peak frequency of 540 Hz, a repetition rate of 20 Hz and a pulse duration of 3.5 ms. The pulse duration suggests an incredibly short twitch time. Sound pressure level (SPL) and pulse duration increase and dominant frequency decreases in larger fish, whereas SPL, repetition rate and dominant frequency increase and pulse duration decreases with increasing temperature. The dominant frequency is inversely related to pulse duration and appears to be determined by the duration of muscle contraction. We suggest that the lower dominant frequency of larger fish is caused by a longer pulse (=longer muscle twitch) and not by the lower resonant frequency of a larger swimbladder.

Dynamic Forced Response of a Rotor-Hybrid Gas Bearing System Due to Intermittent Shocks

2009 ◽  
Author(s):  
Luis San Andre´s ◽  
Keun Ryu
Keyword(s):  
Natural Frequency ◽  
Fuel Efficiency ◽  
Forced Response ◽  
System Level ◽  
Jet Engines ◽  
Test Rig ◽  
Gas Bearings ◽  
Business Jet ◽  
Gas Bearing ◽  
Bearing System

Gas bearings in microturbomachinery (MTM) offer significant system level benefits, such as improved fuel efficiency, reduction in weight and number of components, extending life cycle and maintenance intervals, and reducing NOX emissions with a lower CO2 footprint. Emerging opportunities for gas bearings applications range from automotive turbochargers to engines for business jet aircraft, for example. Gas bearings, because of the inherently low gas viscosity, have low damping relative to oil-lubricated bearings and are prone to wear during rotor start-up and shut down procedures. The lack of damping brings concerns about rotor-gas bearing system robustness and endurance to tolerate shock induced loads, sudden while landing in jet engines, or intermittent in vehicles while moving across a rough terrain, for example. The paper demonstrates the reliability of a hybrid gas bearing system from rotor vibration measurements induced by sporadic shock loads acting on the base of a test rig and while the rotor is coasting down from a top speed of 60 krpm (1000 Hz). In the tests, (1) an electromagnetic pusher delivers impacts to the rig base, or (2) the whole rig is manually tilted and dropped. The test rig consists of a rigid rotor, 0.825 kg and 28.6 mm in diameter, supported on two flexure pivot tilting pad type, hybrid gas bearings, each with four pads and 60% pivot offset and 0.6 mm feeding holes. The bearings are supplied with feed pressures of 2.36, 3.72, and 5.08 bar (ab). Intermittent shocks, up to 30 g pk-pk and exciting a broad frequency range to 400 Hz, produce a remarkable momentary increase of the overall rotor response amplitude, up to 50 μm (pk-pk). The shocks readily excite the fundamental natural frequency of the rotor-bearing system (150–200 Hz), and on occasion the natural frequency (40 Hz) of the whole test rig. For operation at rotor speeds above the system critical speed, the rotor synchronous response is isolated; with transient motions induced by a shock, subsynchronous in whirl frequency, quickly disappearing. Full recovery takes place in ∼0.10 second. The measurements demonstrate that the hybrid gas bearings have enough damping to rapidly attenuate rotor transient motions and to dissipate the energy induced from intermittent shocks. Note that the shocks acted while the rotor traversed its critical speeds. The reliability of engineered gas bearings to forced transient events is no longer in question.

scholarly journals Nonlinear Resonance Responses of Electromechanical Integrated Magnetic Gear System

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Xiu-hong Hao ◽  
Hong-qian Zhu ◽  
Deng Pan
Keyword(s):  
Natural Frequency ◽  
Magnetic Force ◽  
Nonlinear Differential Equations ◽  
Nonlinear Resonance ◽  
Magnetic Coupling ◽  
Dominant Frequency ◽  
Electromechanical Integrated ◽  
Coupling Stiffness ◽  
Magnetic Gear ◽  
Stiffness And Damping

Nonlinear differential equations for an electromechanical integrated magnetic gear (EIMG) system are developed by considering the nonlinearity in the magnetic force of the system components. Expressions for the main resonances and superharmonic resonances are obtained for output wave frequencies close to the natural frequency and half the natural frequency of the derived EIMG system. The response laws are discussed in detail. The magnetic coupling stiffness among the components is found to exhibit distinct nonlinearity, leading to strong main resonances and superharmonic resonances. Smaller values of the magnetic coupling stiffness and damping result in larger response amplitudes and transient responses that slowly decay to zero. When the main resonances and superharmonic resonances occur, the dominant frequency of the response is the natural frequency of the derived EIMG system, and the amplitudes of different components of the resonance display large differences.

Static Stress Redesign of Structures by Large Admissible Perturbations

2003 ◽  
Vol 127 (2) ◽  
pp. 122-129 ◽  
Author(s):  
Michael M. Bernitsas ◽  
Bhineka M. Kristanto
Keyword(s):  
Cross Section ◽  
Forced Response ◽  
Static Stress ◽  
Neutral Axis ◽  
Perturbation Equation ◽  
Cross Sectional ◽  
Structure Changes ◽  
Large Admissible Perturbations ◽  
The Cross ◽  
Outer Fiber

The LargeE Admissible Perturbation (LEAP) methodology is developed further to solve static stress redesign problems. The static stress general perturbation equation, which expresses the unknown nodal stresses of the objective structure in terms of the baseline structure stresses, is derived first. This equation depends on the redesign variables for each element or group of elements; namely, the cross-sectional area and moment of inertia, and the distance between the neutral axis and the outer fiber of the cross section. This equation preserves the shape of the cross section in the redesign process. LEAP enables the designer to redesign a structure to achieve specifications on modal properties, static displacements, forced response amplitudes, and static stresses. LEAP is implemented in code RESTRUCT which post-processes the FEA results of the baseline structure. Changes on the order of 100% in the above performance particulars and in redesign variables can be achieved without repetitive finite element (FE) analyses. Several numerical applications on a simple cantilever beam and an offshore tower are used to verify the LEAP algorithm for stress redesign.

scholarly journals Pengujian Alat Pemanen Energi Akustik Berbasis Loudspeaker Dengan Sumber Kebisingan Acak Dari Mesin Kendaraan Bermotor

2019 ◽  
Vol 4 ◽  
pp. 152
Author(s):  
Untung Adi Santosa ◽  
Ikhsan Setiawan ◽  
B.S. Utomo
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Random Noise ◽  
Electrical Power ◽  
Dominant Frequency ◽  
Pressure Level ◽  
Acoustic Energy ◽  
Noise Sources ◽  
Quarter Wavelength ◽  
The Impact

<p class="AbstractEnglish"><strong>Abstract: </strong>This paper reports the test results of a loudspeaker-based acoustic energy harvester with acoustic random noise sources from a motorcycle. The harvester consists of a quarter wavelength resonator and a subwoofer type loudspeaker with a nominal diameter of 6 inches. The motorcycle used in this experiment is 135 cc Bajaj Pulsar motorsport with modified exhaust from the GBS-Motosport Jakarta. The motor engine is operated at 3000 rpm, resulting in noise with a fluctuating Sound Pressure Level (SPL) in the range of (90-93) dB. Six variations of resonator lengths are used, those are 21 cm, 31 cm, 58 cm, 85 cm, 112 cm, and 139 cm. In this test, data of dominant frequency, SPL, and output rms voltage were taken for 15 minutes. The rms voltage is measured at 100 Ω load resistor. The results show that the 112 cm resonator produces the highest average rms electrical power, that is (0.21 ± 0.01) mW, which is obtained at frequency that fluctuates within (95-120) Hz. In addition, with random sound sources, SPL and its dominant frequency fluctuate greatly, so it will greatly affect the generated electric power. Further research is needed to enhance the output electrical power and anticipate the impact of frequency fluctuation which exists in random noise sources.</p><p class="AbstractEnglish"><strong>Abstrak: </strong>Paper ini memaparkan hasil pengujian alat pemanen energi akustik berbasis <em>loudspeaker </em>dengan sumber kebisingan acak dari mesin kendaraan bermotor. Alat pemanen energi akustik ini terdiri dari resonator seperempat panjang gelombang dan <em>loudspeaker</em> jenis <em>subwoofer</em> dengan diameter nominal 6 inci. Sumber kebisingan yang digunakan adalah motor Bajaj Pulsar 135 cc dengan knalpot modifikasi dari GBS-Motosport Jakarta. Mesin motor dioperasikan pada laju putaran tetap 3000 rpm, sehingga menghasilkan kebisingan dengan <em>SPL</em> (<em>sound pressure level</em>) yang berfluktuasi dalam interval (90-93) dB. Digunakan enam variasi panjang resonator, yaitu 21 cm, 31 cm, 58 cm, 85 cm, 112 cm, dan 139 cm. Dalam pengujian ini, data frekuensi dominan kebisingan, <em>SPL</em> kebisingan, dan tegangan keluaran alat pemanen energi akustik diambil selama 15 menit. Tegangan <em>rms</em> keluaran diukur pada resistor beban 100 Ω. Hasil eksperimen menunjukkan bahwa resonator dengan panjang 112 cm menghasilkan daya listrik <em>rms</em> rata-rata tertinggi yaitu sebesar (0,21 ± 0,01) mW, diperoleh pada frekuensi yang berfluktuasi antara 95 Hz sampai 120 Hz. Selain itu, hasil eksperimen ini menunjukkan bahwa dengan sumber bunyi acak, <em>SPL</em> kebisingan dan frekuensi dominannya sangat berfluktuasi, sehingga akan sangat berpengaruh terhadap daya listrik yang dihasilkan. Penelitian lebih lanjut diperlukan untuk meningkatkan daya listrik keluaran dan mengantisipasi dampak fluktuasi frekuensi sumber kebisingan acak.</p>

A Study on Noise in Synchronous Belt Drives: Experimental and Theoretical Analysis of Impact Sound

2000 ◽  
Author(s):  
Weiming Zhang ◽  
Tomio Koyama
Keyword(s):  
Theoretical Analysis ◽  
Natural Frequency ◽  
Sound Source ◽  
Transverse Vibration ◽  
Sound Field ◽  
Acoustic Energy ◽  
Generation Mechanism ◽  
Belt Drives ◽  
Fundamental Natural Frequency ◽  
The Impact

Abstract There are two kinds of noise in synchronous belt drives. One is steady sound caused by transverse vibration of belt, and another is impact sound radiating from meshing point of belt and pulley. Recently, it has been reported that the impact sound is due to the sound occurring in an air pipe built up between pulley groove and belt because the frequency of impact sound coincides with the fundamental natural frequency of an open ended pipe whose length equals width of the belt. However, this conclusion is obtained experimentally, there has no theoretical analysis provided. In this study, an analysis of the impact sound is provided to prove its generation mechanism and discuss factors that influence the level of sound theoretically. Sound field in an open ended pipe subjected to an impulsive sound source is analyzed. Comparison between experimental and analytical results is carried out. It is concluded that the level of impact sound is in proportion to the width of belt, and the acoustic energy of impact sound is in proportion to the cube of the width of belt.

Development of State of the Art Dynamic Stress Prediction Methodology for Steam Turbines

2011 ◽  
Author(s):  
Tie Chen ◽  
John Rogerson ◽  
Fang Yang ◽  
Gurnam Singh ◽  
Phil Hemsley
Keyword(s):  
Frequency Shift ◽  
Natural Frequency ◽  
Coupling Effect ◽  
Computing Time ◽  
Turbine Blades ◽  
Nonlinear Damping ◽  
Forced Response ◽  
Explicit Method ◽  
Friction Forces ◽  
Peak Response

To predict the dynamic stresses due to forced response of steam turbine blades, a commercial FE solver ABAQUS has been linked with an in-house CFD solver TF3D-VIB, in the time domain in both one-way and two-way coupling. Both methods have been applied to analyse a freestanding subsonic turbine stage excited by upstream flow perturbations. Over a frequency range the peak responses are very similar, but the peak response of two-way coupling is shifted to a lower frequency, due to the aerodynamic coupling effect of fluid-structure interaction. That means a speed / frequency sweep is necessary to search for the peak response in two-way coupling. However, in one-way coupling, the frequency shift can be derived from the vibration induced modal force, and only one calculation is needed to predict the response over a range of frequency ratio using the classic single degree-of-freedom equation. One calculation using two-way coupling typically takes seven times more computing time than one-way coupling. The total computing time for two-way coupling to define the response characteristic is therefore much higher; more calculations are needed and each calculation takes much longer. Thus a one-way coupling method including the frequency shift correction is much more practical and suitable for blade design iterations. The blade forced response is also limited by damping. In the case of low damping such as material only damping, this can be well represented in the harmonic ABAQUS calculation. However, high values of nonlinear damping can be deliberately introduced by managing the friction forces at blade root attachment. The nonlinear damping can be simulated directly by ABAQUS/Explicit method, convergence criteria often lead to excessive runtimes. Therefore a simple mass/spring model has been developed, which applies an exciting force to a system comprising two masses and springs to represent the blade and the root respectively and includes modelling of both the stick and slip forces of the root due to friction. Both the masses and their spring stiffness are chosen to produce either the sticking natural frequency (with infinite friction) or sliding natural frequency (zero friction). Using the simple two-mass model, the significant nonlinear response pattern is demonstrated. The resulting pattern has been verified against the ABAQUS/Explicit method. This allows the blade forced response prediction from the one way coupling to be further corrected to account for the nonlinear friction damping effect.

Effects of Mesh-Induced Upstream Turbulence on Flip-Flop Flow Inside Diamond-Shaped Cylinder Bundles

Volume 3 ◽  
2004 ◽  
Author(s):  
Shinzaburo Umeda ◽  
Wen-Jei Yang
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Power Spectra ◽  
Dominant Frequency ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Flow Measurements ◽  
Flip Flop ◽  
Flow Cross Section ◽  
Flow Cross

An experimental study is conducted to investigate effects of mesh-induced upstream turbulence on flip-flop flow inside diamond-shaped cylinder bundles. In order to quantitatively treat flip-flop flow induced by the self-excited oscillation of vortices, flow measurements by means of two-dimensional particle image velocimetry (PIV) and two-dimensional laser Doppler velocimetry (LDV) are employed. Flow cross-sectional area and flow rate are varied to change the Reynolds number in the bundles. A turbulence mesh is installed a very short distance upstream from the inlet of the test section. The LDV is employed to measure velocity changes in the flip-flop flow, while power spectra representing its oscillating characteristics are determined from LDV data. The dominant frequency is observed special features are disclosed in the relationship between the Reynolds number and the Strouhal number representing the dimensionless dominant frequency in all power spectra of the flip-flop flow. It is disclosed that both the flow cross section and the upstream turbulence are related to the generation of flip-flop flow in complex manner, and that the effects of the turbulence differ depending upon the flow cross section.

Vibration localization for a rotating mistuning bladed disk with the Coriolis effect by a state-space decoupling method

2017 ◽  
Vol 233 (3) ◽  
pp. 1011-1020 ◽  
Author(s):  
Xuanen Kan ◽  
Zili Xu
Keyword(s):  
State Space ◽  
Natural Frequency ◽  
Coriolis Force ◽  
High Speed ◽  
Forced Response ◽  
Coriolis Effect ◽  
Decoupling Method ◽  
Resonant Amplitude ◽  
Bladed Disk ◽  
Localization Factor

Slight deviations of blades due to manufacturing tolerances can cause mistuning of bladed disk leading to localized vibration, which can accelerate fatigue. Moreover, the rotating blades are subjected to the Coriolis effect and the influence of the Coriolis force on the natural frequencies of high-speed rotational bladed disks such as those of an aero-engine become more apparent. In this paper, the effect of Coriolis force on the forced response localization of a mistuned bladed disk are investigated, for conditions where the natural frequency located in the first and second modal families of the bladed disk. Mistuning is introduced by varying the Young’s modulus of each blade. Due to the asymmetric Coriolis matrix, it is not possible to directly decouple the system. A state-space decoupling method is developed to decouple the system to effectively calculate the forced response of bladed disk with the consideration of the Coriolis effect. The results show that response localization factor is increased by 13.09% considering the Coriolis force compared to the system without considering the Coriolis effect, in the case of where the first modal family is considered. In addition, the response localization factor with the consideration of the Coriolis force is decreased by 30.85% compared to the system without considering the Coriolis force, when the second modal family is considered. It indicates that the forced response localization with the consideration of the Coriolis effect will be changed obviously with the rotational speed increasing, when the concerning natural frequency is located in the first and second modal families. Furthermore, the effect of Coriolis force causes changes in the resonant frequencies and resonant amplitude, but does not introduce additional resonant peaks for the case of the mistuned bladed disk.

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