Relevant bibliographies by topics / Tongue pressure measurement

Academic literature on the topic 'Tongue pressure measurement'

Author: Grafiati
Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "Tongue pressure measurement"

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Mizuhashi, Fumi, Kaoru Koide, Shuji Toya, and Tomoko Nashida. "Measurement of Oral Moisture on Oral Dryness Patients." Geriatrics 5, no. 2 (April 30, 2020): 28. http://dx.doi.org/10.3390/geriatrics5020028.

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Many elderly patients have oral dryness; thus, it is necessary to evaluate the oral moisture in a clinical setting. The aim of this study was to clarify the importance of controlling the measuring pressure of the oral moisture-checking device. The influence of the measuring pressure of the oral moisture-checking device was examined using agar under 10 measuring pressure conditions (Kruskal–Wallis test). Fifty-five oral dryness patients were examined the lingual moisture using the device with and without a tongue depressor. The tongue depressor was placed underneath the tongue to support it during the measurement. The mean value and the coefficient of variation of five measurements was evaluated (paired t-test or Wilcoxon signed-ranks test). The agar moisture values changed according to the measuring pressure (p < 0.05). The lingual moisture value with the tongue depressor was higher than that without the tongue depressor (p < 0.05). The coefficient of variation with the tongue depressor was smaller than that without the tongue depressor (p < 0.01). The results of this study indicated that the measuring pressure of oral moisture-checking device influenced the measurement value, and it is necessary to support the tongue for the measurement of lingual mucosal moisture in a uniform manner.
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Funami, Takahiro. "Tongue pressure measurement in food science." Current Opinion in Food Science 9 (June 2016): 29–33. http://dx.doi.org/10.1016/j.cofs.2016.04.003.

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Yang, Hui, Peiquan Yu, Jun Xu, Cunlie Ying, Wenbing Cao, Yingdong Wang, Zuchao Zhu, and Yikun Wei. "Experimental investigations on the performance and noise characteristics of a forward-curved fan with the stepped tongue." Measurement and Control 52, no. 9-10 (October 19, 2019): 1480–88. http://dx.doi.org/10.1177/0020294019877482.

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This work presents an experimental study to investigate the influence of step volute tongue on aerodynamic performance and aeroacoustic behavior of a forward-curved fan. The noise characteristics are analyzed and controlled based on measured acoustic pressures for various stepped tongues; meanwhile, fan performance is detected and optimized. The design parameters of the stepped tongues are presented to provide significant physical insight into increasing the static pressure as well as the efficiency of static pressure and reducing the fan noise generation. The comparison of the test results indicates that the improved static pressure and its efficiency of the HLHL model have increased by 15.67 Pa and 3.57%, respectively, by comparing with those of the baseline model. At 740 m3/h, a great correlation between different arrays of stepped tongue and the noise generation was observed. The tonal noise level of the HLHL model is a better optimization scheme because it decreases as much as 1.2 dB for the noise generation of forward-curved fan. In particular, it is found that some stepped tongues of the volute tongue achieved the goal of reducing noise generation and improving the performance of fan by experimental measurement at the same time.
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Shieh, Wann-Yun, Chin-Man Wang, Hsin-Yi Kathy Cheng, and Titilianty Ignatia Imbang. "Noninvasive Measurement of Tongue Pressure and Its Correlation with Swallowing and Respiration." Sensors 21, no. 8 (April 7, 2021): 2603. http://dx.doi.org/10.3390/s21082603.

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Tongue pressure plays a critical role in the oral and pharyngeal stages of swallowing, contributing considerably to bolus formation and manipulation as well as to safe transporting of food from the mouth to the stomach. Smooth swallowing relies not only on effective coordination of respiration and pharynx motions but also on sufficient tongue pressure. Conventional methods of measuring tongue pressure involve attaching a pressure sheet to the hard palate to monitor the force exerted by the tongue tip against the hard palate. In this study, an air bulb was inserted in the anterior oral cavity to monitor the pressure exerted by the extrinsic and intrinsic muscles of the tongue. The air bulb was integrated into a noninvasive, multisensor approach to evaluate the correlation of the tongue pressure with other swallowing responses, such as respiratory nasal flow, submental muscle movement, and thyroid cartilage excursion. An autodetection program was implemented for the automatic identification of swallowing patterns and parameters from each sensor. The experimental results indicated that the proposed method is sensitive in measuring the tongue pressure, and the tongue pressure was found to have a strong positive correlation with the submental muscle movement during swallowing.
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Utanohara, Yuri, Ryo Hayashi, Mineka Yoshikawa, Mitsuyoshi Yoshida, Kazuhiro Tsuga, and Yasumasa Akagawa. "Standard Values of Maximum Tongue Pressure Taken Using Newly Developed Disposable Tongue Pressure Measurement Device." Dysphagia 23, no. 3 (June 24, 2008): 286–90. http://dx.doi.org/10.1007/s00455-007-9142-z.

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Nishi, Eri, Ryosuke Okuda, Katsuyuki Hiraoka, Satoshi Nagai, and Katsuhisa Rikoh. "Pressure Distribution Measurement System of Infant Tongue Sucking." IEEJ Transactions on Electronics, Information and Systems 138, no. 11 (November 1, 2018): 1327–33. http://dx.doi.org/10.1541/ieejeiss.138.1327.

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Takada, Jun-ichi, Takashi Ono, Shigeki Takahashi, Ei-ichi Honda, and Tohru Kurabayashi. "Changes in Horizontal Jaw Position and Intraoral Pressure." Angle Orthodontist 78, no. 2 (March 1, 2008): 254–61. http://dx.doi.org/10.2319/021207-69.1.

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Abstract Objective: To determine the effect of an imbalance in buccolingual pressure that may be involved in molar dental compensation in the mandible and asymmetry of the dental arch in subjects with facial asymmetry. Materials and Methods: We performed simultaneous measurement of the buccolingual pressure on the mandibular right first molar when subjects without facial asymmetry experimentally shifted the mandible laterally. Buccolingual pressures in the rest position (RP), right-shifted position (RS), and left-shifted position (LS) were compared. Moreover, T1-weighted magnetic resonance images were obtained in RP, RS, and LS. Results: Tongue pressure tended to decrease in the order LS &gt; RP &gt; RS, while cheek pressure tended to increase in the order LS &lt; RP &lt; RS. The tongue/cheek pressure ratio tended to decrease in the order LS &gt; RP &gt; RS. There were significant positive (in RS) and negative (in LS) correlations between displacement of the tongue and tongue pressure. Conclusions: This imbalance in buccolingual pressures in the laterally-shifted mandibular position may partly explain molar dental compensation in the mandible and asymmetry of the dental arch in subjects with facial asymmetry.
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Koshi, N., J. Magara, S. Sakai, T. Suzuki, T. Tsujimura, and M. Inoue. "Electromyographic analysis of hyoid muscles during tongue pressure measurement." Journal of Japanese Society of Stomatognathic Function 24, no. 1 (2017): 34–35. http://dx.doi.org/10.7144/sgf.24.34.

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Azevedo, N. D., J. C. Lima, R. M. M. M. Furlan, and A. R. Motta. "Tongue pressure measurement in children with mouth-breathing behaviour." Journal of Oral Rehabilitation 45, no. 8 (June 10, 2018): 612–17. http://dx.doi.org/10.1111/joor.12653.

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Yoshikawa, Mineka, Mitsuyoshi Yoshida, Kazuhiro Tsuga, Yasumasa Akagawa, and Michael E. Groher. "Comparison of Three Types of Tongue Pressure Measurement Devices." Dysphagia 26, no. 3 (July 11, 2010): 232–37. http://dx.doi.org/10.1007/s00455-010-9291-3.

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Dissertations / Theses on the topic "Tongue pressure measurement"

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Kennedy, Daniel Lloyd, and n/a. "Measurement of intraoral pressure during normal swallowing." University of Otago. School of Dentistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081211.160044.

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Aim: The aim of this research was to measure functional intraoral pressures using a newly developed method; specifically, three areas were examined. Firstly, this new approach to measurement allowed the equilibrium theory of tooth position to be re-addressed. Secondly, it allowed investigation the patterns of pressure change in the palatal midline during water swallowing. Lastly, this approach allowed a preliminary investigation of the affect of the viscosity of the food ingested on the pressures generated in the mouth. Methods: The participants were 6 healthy volunteers (4 males, 2 females) recruited from the post-graduate students at the University of Otago, School of Dentistry. The age range was 25 to 35 years. All had full permanent dentitions, Angle Class I occlusions (normal) with acceptable overbite and overjet relationship, and none of them had a history of previous orthodontic treatment. For each of the subjects a cast chrome-cobalt baseplate was constructed to house 8 miniature strain gauge pressure transducers (Precision Measurement Co. Michigan). The location of the sensors were standardised as follows: Three sensors were paired on the buccal and lingual surfaces of the central, canine and first molar. Two palatal vault sensors were placed in the midline of the palate, one at level of the distal of the first premolar, and the second slightly anterior to the junction of the hard and soft palate. Simultaneous recordings were taken during a set of tasks including water swallows, saliva swallows and food ingestion. Results: The results showed that swallowing was a highly complex wellcoordinated event, and that each individual had their own unique signature pattern of swallowing, characterised by pressure changes of high frequency, in excess of �1000 kPa/s. Conclusions: The analysis of the pressure acting on the teeth showed that although the pattern and magnitude of pressure generated varied among the group, the observation of waveforms would suggest a tendency for no inherent balance between the buccal and the palatal pressures on the teeth during swallowing for any of the individuals tested. This investigation of the pressure in the midline revealed an aspect previously not fully explored; these experiments showed that there were large and persistent negative pressures generated during swallowing, that preceded the positive pressures and which appear important in bolus propulsion The patterns of swallowing and the magnitudes of pressure generated, changed with the different consistency of the various substances ingested. There was a general trend for increased pressures during swallowing of substrates that are more viscous; water showed the lowest pressures, followed by saliva and finally jelly. Keywords: Tongue pressure, Intraoral pressures, Tongue dynamics, Swallowing.
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Shin, Pei Hsun, and 辛沛勳. "Non-invasive Tongue Pressure Measurement for Swallowing Function Assessment." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/98005888112368591959.

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Van, Rooyen Sonia. "Immittance in infant 0–12 months: Measurements using a 1000 Hz probe tone." Diss., 2006. http://hdl.handle.net/2263/29106.

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Rapid implementation of universal newborn hearing screening programs has exposed a need for a reliable test of middle ear function for timely identification of middle ear pathology and for differentiation between true sensorineural and conductive hearing losses. Use of higher probe tone frequencies for the assessment of immitance measures have proven to be more reliable and accurate in identifying MEE in infants. However a lack of classification-guidelines and age specific normative data exists. This study investigated the characteristics and normative values of high frequency tympanometric and acoustic reflex results for infants (n = 936 ears). Participants were 510 infants (262 male, 248 female) aged 0 – 12 months (mean age = 12.8 weeks) recruited from primary health care and immunization clinics in a South African community. A three-part procedure was performed on each test ear: 1) OAEs were recorded and pass results served as control variable for normal middle ear functioning; 2) 1000 Hz probe tone admittance, susceptance and conductance tympanograms were recorded and analysed in terms of shape, tympanometric peak pressure and maximum (peak) admittance; 3) 1000 Hz probe tone acoustic reflexes, measured with a 1000 Hz ipsilateral stimulus, were recorded and thresholds determined. Significant associations were observed between tympanogram shape, and OAE pass or fail results. 93% of ears with an OAE pass result displayed peaked tympanograms, while 79% of ears with absent OAE’s displayed flat tympanograms. Single peaked tympanograms were recorded in 782 ears (84%), double peaked tympanograms in 41 (4%) ears and flat sloping tympanograms in 112 (12%) ears. Admittance (Ya) tympanograms for the total sample displayed a mean admittance value of 2.9 mmho, with a standard deviation of 1.1 mmho. The 90th percent range was determined at 1.5 mmho (5th percentile) to 4.9 mmho (95th percentile). Mean tympanometric peak pressure in Ya tympanograms was 0.1 daPa, with a standard deviation of 61 daPa. The 90th percent range was -110 daPa to 90 daPa for the 5th and 95th percentiles respectively. Gender specific norms indicated a higher admittance for male ears. Age specific norms indicate a gradual increase in admittance indicating the need for age specific normative classification systems. Ipsilateral 1000 Hz stimuli acoustic reflex measurement proved successful with a 1000 Hz probe tone and present reflexes were recorded in 84% of ears tested. Significant association between acoustic reflex presence, OAE pass and peaked tympanogram results were observed. The normative tympanometric values derived from the cohort may serve as a guide for identification of middle ear effusion in neonates. High frequency tympanometry in combination with acoustic reflexes proves a useful measure for verifying middle ear functioning in young infants.
Dissertation (M (Communication Pathology))--University of Pretoria, 2007.
Speech-Language Pathology and Audiology
M (Communication Pathology)
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Book chapters on the topic "Tongue pressure measurement"

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Niikawa, Takuya, R. Kawachi, K. Minato, and Y. Takada. "Measurements of pressure distribution by the tongue of infants on an artificial nipple." In IFMBE Proceedings, 1149–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-89208-3_275.

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Thomas, Gregory S., and Myrvin H. Ellestad. "Blood Pressure Measurements during Exercise Testing." In Ellestad's Stress Testing, edited by Gregory S. Thomas, L. Samuel Wann, and Myrvin H. Ellestad, 107–34. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190225483.003.0006.

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``The chapter Blood Pressure Measurement During Exercise reviews the 3 methods of sphygmomanometry to measure blood pressure and normal and abnormal blood pressure responses to exercise. Mercury, aneroid, and oscillometric assessment of Korotkoff sounds provide accurate measurement. Periodic calibration is important for aneroid and oscillometric devices. With verification, automated oscillometric measurements during exercise can be accurate. The normal blood pressure response to exercise testing is an incremental increase in systolic blood pressure with minimal change in diastolic blood pressure. Exercise induced hypotension, particularly early in exercise, is predictive of severe coronary artery disease (CAD). Its occurrence at peak exercise at a high level of exertion may occur in normal individuals secondary to exhaustion. An exaggerated systolic response to exercise is modestly predictive of future hypertension. A slow decrease is systolic blood pressure during recovery is suggestive of CAD, likely secondary to less vagal tone, analogous to a slow decrease in heart rate during recovery.
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Conference papers on the topic "Tongue pressure measurement"

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Lu, Cheng-Huan, Muhammad Omar Shaikh, Hsiu-Yueh Liu, and Cheng Hsin Chuang. "Piezoresistive tactile sensor with tongue pressure measurement capability for dysphagia assessment." In 2020 IEEE International Conference on Consumer Electronics - Taiwan (ICCE-Taiwan). IEEE, 2020. http://dx.doi.org/10.1109/icce-taiwan49838.2020.9258318.

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Matsumura, Masafumi, Takuya Niikawa, Taku Torii, Hitoshi Yamasaki, Hisanaga Hara, Takashi Tachimura, and Takeshi Wada. "Measurement of palatolingual contact pressure and tongue force using a force-sensor-mounted palatal plate." In 6th International Conference on Spoken Language Processing (ICSLP 2000). ISCA: ISCA, 2000. http://dx.doi.org/10.21437/icslp.2000-678.

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Zhao, Binjuan, Shouqi Yuan, Zhongfu Huang, and Duohua Hou. "Investigation of Multiphase Unsteady Flow in a Double-Channel Pump by CFD Simulation and PIV Measurement." In ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fedsm2012-72139.

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The multiphase unsteady flow fields in a double-channel pump have been investigated both numerically and experimentally for the design condition and also off-design conditions. Three-dimensional, unsteady Reynolds-averaged Navier–Stokes equations are solved on high-quality unstructured tetrahedral mesh with the shear stress transport turbulence model by using the CFD code Fluent 6.4. Furthermore, PIV measurements are successfully conducted in the impeller, in order to capture the complex flow with abundant measurement data and to validate the CFD results. The main conclusions include: 1) The velocity field changes according to the blade orientation. When the impeller channel is near to the outlet of volute, the velocity distribution is relatively regular than when the impeller channel is far from the outlet of volute. 2) At the tongue of the volute, the fluid discharged from the impeller mixes with the re-circulating fluid in the volute, which contributes a lot to the impeller-volute interaction. 3) The pressure vibration in the volute is very obvious, pressure fluctuation on monitors far from the volute outlet is more obvious than those near to the volute outlet, and becomes stronger as drawing near the tongue. 4) The sand volume fraction distribution is extremely inhomogeneous in both impeller and volute. Particles mainly flow along the pressure surface and hub of the impeller; Particles mainly accumulate in the region near to the exit of volute, and the largest sand volume fraction is observed at the tongue. 5) Particle diameter has great influence on the particle distribution, and particles tend to accumulate on the pressure surface of the balde with the increase of particle diameter. 6) The total pressure difference of the pump declines with the increase of inlet sandy volume fraction or particle diameter. 7) PIV measurement results correspond well with the CFD simulation results, which in turn gives a good validation of the simulation accuracy. This work offers a good data set to develop the comprehension of the unsteady multiphase flow in the double-channel pump.
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Yao, Zhifeng, Fujun Wang, Ruofu Xiao, Chenglian He, and Zhuqing Liu. "Experimental Investigation of Relationship Between Pressure Fluctuations and Vibrations for a Double Suction Centrifugal Pump." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-06014.

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Double-suction centrifugal pumps are widely employed in large-scale pumping stations, which generally run in the conditions of large discharge with huge energy consumption. Pressure fluctuation caused by internal flow due to tongue-impeller interaction is the primary source of pump vibration. In this paper, pressure fluctuations and vibrations signals on volute casing wall were experimentally obtained at five flow rates ranging from 59% to 121% of nominal flow rate. Time and frequency domains of the signals were mainly analyzed by using statistical and fast Fourier transform methods. The results show that rotational frequency, blade passing frequency and their harmonic frequencies of pressure fluctuations as well as vibrations are clearly identified. The magnitude at blade passing frequency has close relationship with the measurement location related to the volute tongue, and becomes larger when the flow rate deviates from the nominal flow rate. The magnitudes at blade passing frequency can increase by 70% and 151% at high flow rate over that at the nominal flow rate for pressure fluctuations and vibrations, respectively. While the magnitude of vibration at rotational frequency keeps nearly constant at partial flow rate, and decreases at high flow rate.
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Yang, Weili, Peter Grant, and James Hitt. "A Numerical Study of Volute Design in Centrifugal Compressor." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/pid-25600.

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Abstract Our principle goal of this study is to develop a CFD based analysis procedure that could be used to analyze the geometric tradeoffs in scroll geometry when space is limited. In the study, a full centrifugal compressor stage at four different operating points from near surge to near choke is analyzed using Computational Fluid Dynamics (CFD) and laboratory measurement. The study concentrates on scroll performance and its interaction with a vaneless diffuser and impeller. The numerical results show good agreement with test data in scroll circumferential pressure distribution at different ΛAR, total pressure loss coefficient, and pressure distortion at the tongue. The CFD analysis also predicts a reasonable choke point of the stage. The numerical results provide overall flow field in the scroll and diffuser at different operating points. From examining the flow fields, one can have a much better understanding of rather complicated flow behavior such as jet-wake mixing, and choke. One can examine total pressure loss in detail to provide crucial direction for scroll design improvement in areas such as volute tongue, volute cross-section geometry and exit conical diffuser.
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Younsi, M., F. Bakir, S. Kouidri, and R. Rey. "Influence of Design Parameters on the Unsteady Flow in a Centrifugal Fan." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37609.

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The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental study has been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these fans. The effects on the unsteady flow behavior related to irregular blade spacing, blade number and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using Computational Fluid Dynamics tools (CFD) based on Unsteady Reynolds Averaged Navier Stokes approach (URANS). The sliding mesh technique has been applied at the interfaces between the rotating and stationary zones in order to model the blades’ motion relative to the volute casing. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations (pressure and velocity fluctuations acquired upon the surfaces of the rotating blades) have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H). Using this model, the acoustic pressure has been computed at the fan exit duct. The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 [1] standard. In addition to this, pressure microphones have been flush-mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL) measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found.
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Sardini, E., M. Serpelloni, and S. Pandini. "Analysis of tongue pressure sensor for biomedical applications." In 2014 IEEE International Symposium on Medical Measurements and Applications (MeMeA). IEEE, 2014. http://dx.doi.org/10.1109/memea.2014.6860031.

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Keller, Jens, Jorge Parrondo, Eduardo Blanco, Raúl Barrio, and Carlos Suárez. "Influence of Pump-Circuit Coupling on Acoustic Waves in Pipelines and Pump Velocity Fields." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97958.

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Hydraulic piping systems are sensitive to excessive acoustic emissions which can give rise to vibrations or to failure of mechanical elements due to fatigue. Common excitation sources are centrifugal pumps due to the periodic interaction of the impeller with the volute tongue. They radiate pressure fluctuations into the connected circuit at the blade-passing frequency which are reflected in the circuit. The aim of the present investigation was the experimental characterization of the perturbations induced in a piping network as a function of the acoustic impedance of the circuit using fast-response pressure transducers. Three transducers were placed along the discharge pipe to decompose the pressure signal into the radiated and reflected acoustic wave, with amplitude and phase. The speed of sound in the water pipelines was determined experimentally. Results of impedance at the pump tongue were compared with a theoretical approach, using a Transfer Matrix Analysis, where each pipe element is represented by a 2×2-matrix, relating the acoustic pressure and velocity fluctuations at the two ports. Attenuation was considered by using complex wavenumbers. The acoustic impedance was changed by using different rotation speeds and by using a cavity which works as a harmonic oscillator whose resonance frequency can be changed. The results presented for different operating points show the influence of changing impedance on the pressure perturbations due to pump-circuit acoustic coupling. The pump was built with a transparent impeller and volute to conduct Particle Image Velocimetry (PIV) measurements in a plane perpendicular to the pump rotation axis. Phase-averaged velocity fields were obtained at different blade positions in the zone around the tongue. Vorticity fields were derived from it and turbulence is shown by representing in-plane turbulent kinetic energy (TKE). Strong vorticity and turbulence occurred in the volute channel behind the blade and near the tongue tip.
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Dong, R., S. Chu, and J. Katz. "Effect of Modification to Tongue and Impeller Geometry on Unsteady Flow, Pressure Fluctuations and Noise in a Centrifugal Pump." In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-034.

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Particle Image Velocimetry (PIV), pressure and noise measurements are used to study the effect of modifications to tongue and impeller geometries on the flow structure and resulting noise in a centrifugal pump. It is demonstrated that the primary sources of noise are associated with interactions of the non-uniform outflux from the impeller (jet/wake phenomenon) with the tongue. Consequently, significant reduction of noise is achieved by increasing the gap between the tongue and the impeller up to about 20% of the impeller radius. Further increase in the gap affects the performance adversely with minimal impact on the noise level. When the gap is narrow, the primary sources of noise are impingement of the wake on the tip of the tongue, and tongue oscillations when the pressure difference across it is high. At about 20% gap, the entire wake and its associated vorticity trains miss the tongue, and the only (quite weak) effect of nonuniform outflux is the impingement of the jet on the tongue. An attempt is also made to reduce the non-uniformity in outflux from the impeller by inserting short vanes between the blades. They cause reduction in the size of the original wakes, but generate an additional jet/wake phenomenon of their own. Both wakes are weak to a level that their impacts on local pressure fluctuations and noise are insignificant. The only remaining major contributor to noise is tongue oscillations. This effect is shown to be dependent on the stiffness of the tongue.
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Karamanis, N., R. F. Martinez-Botas, and C. C. Su. "Mixed Flow Turbines: Inlet and Exit Flow Under Steady and Pulsating Conditions." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0470.

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The performance and detailed flow characteristics of a high pressure ratio mixed flow turbine has been investigated under steady and pulsating flow conditions. The rotor has been designed to have a nominal constant incidence (based on free vortex flow in the volute) and it is for use in an automotive high speed diesel turbocharger. The results indicated a departure from the quasi-steady analysis commonly used in turbocharger turbine design. The pulsations from the engine have been followed through the inlet pipe and around the volute; the pulse has been shown to propagate close to the speed of sound and not according to the bulk flow velocity as stated by some researchers. The flow entering and exiting the blades has been quantified by a laser Doppler velocimetry system. The measurements were performed at a plane 3.0 mm ahead of the rotor leading edge and 9.5 mm behind the rotor trailing edge. The turbine test conditions corresponded to the peak efficiency point at 29,400 and 41,300 rpm. The results were resolved in a blade-to-blade sense to examine in greater detail the nature of the flow at turbocharger representative conditions. A correlation between the combined effects of incidence and exit flow angle with the isentropic efficiency has been shown. The unsteady flow characteristics have been investigated at two flow pulse frequencies, corresponding to internal combustion engine speeds of 1600 and 2400 rpm. Four measurement planes have been investigated: one in the pipe feeding the volute, two in the volute (40° and 130° downstream of the tongue) and one at the exit of the turbine. The pulse propagation at these planes has been investigated; the effect of the different planes on the evaluation of the unsteady isentropic efficiency is shown to be significant. Overall, the unsteady performance efficiency results indicated a significant departure from the corresponding steady performance, in accordance with the inlet and exit flow measurements.
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