Acoustic Enhancement of the Rate of Heat Transfer Over a Flat Plate-An Experimental Investigation

1997 ◽  
Vol 119 (4) ◽  
pp. 257-264 ◽  
Author(s):  
J. M. Preston ◽  
W. S. Johnson
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Resonant Frequency ◽  
Flat Plate ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Air Flow ◽  
Copper Plate ◽  
Pressure Level ◽  
Sound Waves

Increasing the rate of heat transfer can improve product quality and lower energy cost for many energy systems. Pulsating fluid flow has been used to increase the rate of heat transfer in some situations. Specifically, sound waves below the audible limit, termed infrasound, have been used to increase the rate of heat transfer from small-diameter wire rods. This study examined the effects of infrasound on the rate of heat transfer from a flat plate. A standing sound wave is formed in the neck of a Helmholtz resonator and may be enhanced by producing sound waves at the resonant frequency at or near the neck of the resonator. In this study, a standing wave of infrasound was produced in a rectangular channel by two loudspeakers driven sinusoidally by a function generator at the resonant frequency of the system. The top of the channel was formed by a copper plate maintained at a constant temperature. Thermocouples placed along the centerline of the channel measured the temperature of the air inside the channel and heat flux gages mounted on the inside surface of the copper plate were used to measure the local rate of heat transfer from the plate to the air inside the channel. Air flow inside the channel was produced by a centrifugal blower and varied by an inlet damper. The use of infrasound increased the rate of heat transfer by approximately an order of magnitude when compared to natural convection. Infrasonic enhancement of the rate of heat transfer over a two-dimensional region in forced convection was more effective in the laminar flow regime, for Reynolds numbers based on the hydraulic diameter between zero and 10,000. Typically for laminar flow, infrasound increased the rate of heat transfer up to five times the rate of heat transfer without infrasound. For turbulent air flow, however, the increase of the rate of heat transfer was almost negligible. The effect of infrasound on the rate of heat transfer was shown to depend on the air velocity inside the channel, the hydraulic diameter of the channel, and the sound pressure level inside the channel. The temperature of the copper plate over the limited range tested did not significantly affect the heat transfer coefficient. The speakers used were limited to a maximum sound pressure level of 121 dB, while infrasonic generators are capable of producing sound pressure levels over 170 dB.

Interaction between Strong Sound Waves and Cloud Droplets: Theoretical Analysis

2021 ◽  
Author(s):  
Ying-Hui Jia ◽  
Fang-Fang Li ◽  
Kun Fang ◽  
Guang-Qian Wang ◽  
Jun Qiu
Keyword(s):  
Sound Wave ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sound Field ◽  
Pressure Level ◽  
Velocity Variation ◽  
Time Range ◽  
Sound Waves ◽  
Cloud Droplets ◽  
Acoustic Frequency

AbstractRecently strong sound wave was proposed to enhance precipitation. The theoretical basis of this proposal has not been effectively studied either experimentally or theoretically. Based on the microscopic parameters of atmospheric cloud physics, this paper solved the complex nonlinear differential equation to show the movement characteristics of cloud droplets under the action of sound waves. The motion process of individual cloud droplet in a cloud layer in the acoustic field is discussed as well as the relative motion between two cloud droplets. The effects of different particle sizes and sound field characteristics on particle motion and collision are studied to analyze the dynamic effects of thunder-level sound waves on cloud droplets. The amplitude of velocity variation has positive correlation with Sound Pressure Level (SPL) and negative correlation with the frequency of the surrounding sound field. Under the action of low-frequency sound waves with sufficient intensity, individual cloud droplets could be forced to oscillate significantly. The droplet smaller than 40μm can be easily driven by sound waves of 50 Hz and 123.4 dB. The calculation of the collision process of two droplets reveals that the disorder of motion for polydisperse droplets is intensified, resulting in the broadening of the collision time range and spatial range. When the acoustic frequency is less than 100Hz (@ 123.4dB) or the Sound Pressure Level (SPL) is greater than 117.4dB (@ 50Hz), the sound wave can affect the collision of cloud droplets significantly. This study provides theoretical perspective of acoustic effect to the microphysics of atmospheric clouds.

Evaluating the Influence of Targeted Air Flow on Sound Pressure Level and Closed Quotient

2021 ◽  
pp. 1-6
Author(s):  
Michael J. Hammer
Keyword(s):  
Fundamental Frequency ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Air Flow ◽  
Vocal Folds ◽  
Pressure Level ◽  
Air Pressure ◽  
Steady Increase ◽  
Closed Quotient ◽  
Considerable Range

Purpose Measures of estimated subglottal air pressure and translaryngeal air flow enable the researcher or clinician to noninvasively assess aerodynamic features related to respiratory and phonatory function. Our goal was to examine the unique relationship between air flow with sound pressure level (SPL) during syllable production while attempting to hold fundamental frequency and subglottal air pressure relatively constant. Method We completed two studies. Study 1: During syllable production, resultant sound pressure level was measured under conditions of constant fundamental frequency and estimated subglottal air pressure while systematically varying translaryngeal air flow. Study 2: During syllable production, resultant sound pressure level and closed quotient (using laryngeal stroboscopy) were measured under conditions of constant fundamental frequency and estimated subglottal air pressure while systematically varying translaryngeal air flow. Results Study 1: Findings suggest a steady increase in sound pressure level with increases in air flow between 25 cc/s and 150 cc/s. Interestingly, relatively stable mean sound pressure level was maintained over a considerable range of air flow values between 225 and 450 cc/s, suggesting that air flow could be further increased without a marked loss of sound pressure level. Study 2: Findings suggest a systematic increase in mean sound pressure level as supraglottic activity subsided and as the closed quotient decreased from 0.80 to 0.58. Interestingly, sound pressure level was relatively stable as the closed quotient decreased from 0.58 to 0.35. Conclusions Our findings suggest that sound pressure level can be maintained over a considerable range of increasing translaryngeal air flow values and over a considerable range of decreasing closed quotient values. These results provide motivation for investigating the interaction between air flow, glottal closure, and sound pressure level among other measures of phonatory function, with important clinical implications for therapeutic approaches that emphasize increases in air flow and focus on reducing contact between the vocal folds.

Comparison of Sound Pressure Level of Conventional and Modified Mufflers by using CFD Analysis

2021 ◽  
Vol 8 (01) ◽  
pp. 63-67
Author(s):  
Zahoor Ullah ◽  
◽  
Hassan Ahmed ◽  
Kareem Akhtar ◽  
◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Combustion Engine ◽  
Pressure Level ◽  
Destructive Interference ◽  
Cfd Analysis ◽  
Sound Waves ◽  
Reflected Waves ◽  
Engine Cylinder ◽  
Real Challenge

The reduction of noise emitted from the exhaust of internal combustion engine is a real challenge for all automotive industries. Mufflers are designed to reflect sound waves produced by the engine in such a way to cancel the effect of each other by destructive interference between the incoming waves from engine cylinder and reflected waves from the muffler of the 2 stroke motorbike engine. Numerical simulation is carried out to study the sound pressure level (SPL) and flow variable like velocity and pressure of conventional and proposed modified reactive muffler.

A Calibration Procedure for the Assessment of Thresholds above 8000 Hz

1982 ◽  
Vol 25 (4) ◽  
pp. 618-623 ◽  
Author(s):  
Patricia G. Stelmacttowicz ◽  
Michael P. Gorga ◽  
John K. Cullen
Keyword(s):  
Frequency Response ◽  
Flat Plate ◽  
Tympanic Membrane ◽  
Sound Pressure Level ◽  
Potential Application ◽  
Sound Pressure ◽  
Calibration Procedure ◽  
Pressure Level ◽  
Frequency Dependent ◽  
Tympanic Membranes

A technique is described to estimate the sound pressure level developed by a broad frequency response transducer at the tympanic membrane. Real-ear probe tube measurements near the tympanic membranes of 10 subjects were used to obtain frequency-dependent correction values for a custom-designed flat-plate coupler. These latter measures can be used tot routine calibration of the transducer. Audiometric thresholds from 250 to 16000 Hz were obtained on 14 children (5–18 years).Threshold estimates were found to be comparable to previouslv reported values. Potential application and limitations of this technique are discussed.

Investigation on collision-coalescence of droplets under the synergistic effect of charge and sound waves: orthogonal design optimization

2021 ◽  
Author(s):  
Fuyou He ◽  
li jiawei_hust ◽  
Chuan Li ◽  
Pengyu Wang ◽  
Zutao Wang ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Orthogonal Design ◽  
Pressure Level ◽  
Collision Probability ◽  
Droplet Growth ◽  
Sound Waves ◽  
Growth Ratio ◽  
Acoustic Frequency ◽  
The Impact

Abstract As an efficient approach to improve the visibility, defogging technology is essential for the operation of ports and airports. This paper proposes a new and hybrid defogging technology, i.e. electric–acoustic defogging method. Specifically, the droplets are charged by corona discharge, which is beneficial to overcome the hydrodynamic interaction force to improve the droplet collision efficiency. Meanwhile, sound waves (especially acoustic turbulence) promote the relative movement of droplets to increase the collision probability. In this study, the effects of acoustic frequency ( f ), sound pressure level (SPL), and voltage (V) on the droplet growth ratio were studied by orthogonal design analysis. The results of difference analysis and multi-factor variance analysis show that frequency and sound pressure level are the dominant factors that affect the collision of droplets, and the effect of voltage is relatively weak. And f = 400 Hz, SPL = 132 dB, and V = -7.2 kV are the optimal parameters in our experiment. In addition, we further studied the impact of single factor on droplet growth ratio. The results show that there is an optimal frequency of 400 Hz. That is, the impact of frequency is non-linear. The droplet growth ratio increases with sound pressure level and voltage level. The new technology proposed in this paper can provide a new approach for defogging in open space.

Numerical Studies on Heat Transfer over a Flat Plate with Triangular Rib-Groove Geometry at Laminar Flow Conditions

2017 ◽  
Vol 374 ◽  
pp. 121-130 ◽  
Author(s):  
T.S. Ravikumar ◽  
Sivamani Seralathan ◽  
Venkatesan Hariram ◽  
Hemanth Kumar Guntamadugu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Flat Plate ◽  
Flow Velocity ◽  
Air Flow ◽  
Heated Plate ◽  
Flow Conditions ◽  
Air Flow Velocity ◽  
Laminar Flow Conditions

In this present study, periodically positioned triangular shaped ribs having a round top corner at the bottom with groove positioned on the top side of the plate is analyzed at laminar flow conditions. The numerical results obtained for the heated plate with rib-groove geometry are compared with that of the flat plate kept under similar conditions. At lower air flow velocity, the Nusselt number of the flat plate improved from 400 to 1407 with the provision of triangular ribs-groove arrangement in it. Similarly, it improved from 850 to 6420 at higher air flow velocity with triangular ribs-groove arrangement. Higher Nusselt number values leads to a higher heat transfer coefficient values. Therefore, the triangular ribs-groove geometry gives an enhanced rate of heat transfer with minimum pressure drop. The study shows that irrespective of geometry, the rate of heat transfer is relying on fluid (air in this present case) flow velocity over heated plate, fluid flow contact with the heated plate and surface area of the heated plate.

scholarly journals Study on acoustic source characteristics of distributed optical fiber acoustic wave monitoring buried natural gas pipeline leakage

2021 ◽  
Vol 252 ◽  
pp. 03043
Author(s):  
Chun Wang ◽  
Zan Wang ◽  
Jia Zhang ◽  
Kelong Yang
Keyword(s):  
Natural Gas ◽  
Acoustic Wave ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Gas Pipeline ◽  
Sound Waves ◽  
Natural Gas Pipeline ◽  
Distributed Optical Fiber

In order to study the leakage of buried natural gas pipeline caused serious environmental pollution and human casualties, the acoustic propagation characteristics of buried natural gas pipeline leakage monitored by distributed optical fiber were studied. At present, the research on the leakage of buried pipeline mainly focuses on the propagation of sound waves along the pipe wall, while the study on the propagation of sound waves in the soil is still lacking. The acoustic attenuation of acoustic wave propagation in soil by the size of leakage hole and leakage pressure is studied, and the evolution process of acoustic wave in soil is revealed. The conclusion is that the acoustic source of buried natural gas pipeline leakage belongs to broadband noise, and the acoustic energy of leakage is prominent in the low frequency band of 15kHz. The lower frequency, the higher sound pressure level. The oscillation of the sound pressure level attenuates with the increase of frequency. Fiber optic monitoring of buried natural gas pipeline leakage early warning provides theoretical support for the conclusion. The sound pressure level in low frequency band is of great significance for buried pipeline leakage monitoring.

Contributions of Voice and Nonverbal Communication to Perceived Masculinity–Femininity for Cisgender and Transgender Communicators

2020 ◽  
Vol 63 (4) ◽  
pp. 931-947
Author(s):  
Teresa L. D. Hardy ◽  
Carol A. Boliek ◽  
Daniel Aalto ◽  
Justin Lewicke ◽  
Kristopher Wells ◽  
...  
Keyword(s):  
Fundamental Frequency ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Vocal Tract ◽  
Presentation Mode ◽  
Pressure Level ◽  
Presentation Modes ◽  
Audiovisual Stimuli ◽  
Vocal Tract Resonance ◽  
Point Light

Purpose The purpose of this study was twofold: (a) to identify a set of communication-based predictors (including both acoustic and gestural variables) of masculinity–femininity ratings and (b) to explore differences in ratings between audio and audiovisual presentation modes for transgender and cisgender communicators. Method The voices and gestures of a group of cisgender men and women ( n = 10 of each) and transgender women ( n = 20) communicators were recorded while they recounted the story of a cartoon using acoustic and motion capture recording systems. A total of 17 acoustic and gestural variables were measured from these recordings. A group of observers ( n = 20) rated each communicator's masculinity–femininity based on 30- to 45-s samples of the cartoon description presented in three modes: audio, visual, and audio visual. Visual and audiovisual stimuli contained point light displays standardized for size. Ratings were made using a direct magnitude estimation scale without modulus. Communication-based predictors of masculinity–femininity ratings were identified using multiple regression, and analysis of variance was used to determine the effect of presentation mode on perceptual ratings. Results Fundamental frequency, average vowel formant, and sound pressure level were identified as significant predictors of masculinity–femininity ratings for these communicators. Communicators were rated significantly more feminine in the audio than the audiovisual mode and unreliably in the visual-only mode. Conclusions Both study purposes were met. Results support continued emphasis on fundamental frequency and vocal tract resonance in voice and communication modification training with transgender individuals and provide evidence for the potential benefit of modifying sound pressure level, especially when a masculine presentation is desired.

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