Volume and Frequency-Independent Spreading of Droplets Driven by Ultrasonic Surface Vibration

Many industrial processes depend on the wetting of liquids on various surfaces. Understanding the wetting effects due to ultrasonic vibration could provide a means for changing the behavior of liquids on any surface. In previous studies, low-frequency surface vibrations have been used to alter wetting states of droplets by exciting droplet volume modes. While high-frequency (>20 kHz) surface vibration can also cause droplets to wet or spread on a surface, this effect is relatively uncharacterized. In this study, droplets of various liquids with volumes ranging from 2 to 70 µL were vibrated on hydrophobic-coated (FluoroSyl) glass substrates fixed to a piezoelectric transducer at varying amplitudes and at a range of frequencies between 21 and 42 kHz. The conditions for contact line motion were evaluated, and the change in droplet diameter under vibration was measured. Droplets of all tested liquids initially begin to spread out at a similar surface acceleration level. The results show that the increase in diameter is proportional to the maximum acceleration of the surface. Finally, liquid properties and surface roughness may also produce some secondary effects, but droplet volume and excitation frequency do not significantly change the droplet spreading behavior within the parameter range studied.

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Forced Wetting of Liquids Using Ultrasonic Surface Vibration

Volume 7: Fluids Engineering ◽

10.1115/imece2018-87832 ◽

2018 ◽

Author(s):

Matthew A. Trapuzzano ◽

Nathan B. Crane ◽

Rasim Guldiken ◽

Andrés Tejada-Martínez

Keyword(s):

Low Frequency ◽

Hydrophobic Surface ◽

Wetting Transitions ◽

High Frequencies ◽

Surface Vibration ◽

Resonance Modes ◽

Energy Inputs ◽

Surface Resonance ◽

Industry Applications ◽

Surface Vibrations

Many processes rely on wetting of liquids on surfaces. The way a liquid wets a solid depends on chemistry, geometry, and local energy inputs. Low-frequency surface vibrations can effect wetting changes prompted by droplet oscillations. High-frequency (ultrasonic) surface vibration can also cause a liquid to wet or spread out on a solid, but governing mechanisms are relatively uncharacterized. To investigate, droplets are imaged as they vibrate on a hydrophobic surface over different high frequencies (> 10 kHz). Wetting transitions occur abruptly over a range of parameters, but coincide with surface resonance modes. The wetting change is proportional to droplet volume and surface acceleration, and remains after cessation of vibration, however new droplets wet with the original contact angle. Wetting control has various industry applications, and understanding these basic phenomena will help develop a deeper understanding of how ultrasonic vibration can be utilized to tune the behavior of liquids on any surface.

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Measured Static and Rotordynamic Coefficient Results for a Rocker-Pivot, Tilting-Pad Bearing With 50 and 60% Offsets

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4004723 ◽

2012 ◽

Vol 134 (5) ◽

Cited By ~ 12

Author(s):

Chris D. Kulhanek ◽

Dara W. Childs

Keyword(s):

Dynamic Stiffness ◽

Mass Matrix ◽

Excitation Frequency ◽

Quadratic Function ◽

Added Mass ◽

Damping Coefficients ◽

Stiffness Coefficients ◽

Tilting Pad ◽

Frequency Independent ◽

Direct Stiffness

Static and rotordynamic coefficients are measured for a rocker-pivot, tilting-pad journal bearing (TPJB) with 50 and 60% offset pads in a load-between-pad (LBP) configuration. The bearing uses leading-edge-groove direct lubrication and has the following characteristics: 5-pads, 101.6 mm (4.0 in) nominal diameter,0.0814 -0.0837 mm (0.0032–0.0033 in) radial bearing clearance, 0.25 to 0.27 preload, and 60.325 mm (2.375 in) axial pad length. Tests were performed on a floating bearing test rig with unit loads from 0 to 3101 kPa (450 psi) and speeds from 7 to 16 krpm. Dynamic tests were conducted over a range of frequencies (20 to 320 Hz) to obtain complex dynamic stiffness coefficients as functions of excitation frequency. For most test conditions, the real dynamic stiffness functions were well fitted with a quadratic function with respect to frequency. This curve fit allowed for the stiffness frequency dependency to be captured by including an added mass matrix [M] to a conventional [K][C] model, yielding a frequency independent [K][C][M] model. The imaginary dynamic stiffness coefficients increased linearly with frequency, producing frequency-independent direct damping coefficients. Direct stiffness coefficients were larger for the 60% offset bearing at light unit loads. At high loads, the 50% offset configuration had a larger stiffness in the loaded direction, while the unloaded direct stiffness was approximately the same for both pivot offsets. Cross-coupled stiffness coefficients were positive and significantly smaller than direct stiffness coefficients. Negative direct added-mass coefficients were obtained for both offsets, especially in the unloaded direction. Cross-coupled added-mass coefficients are generally positive and of the same sign. Direct damping coefficients were mostly independent of load and speed, showing no appreciable difference between pivot offsets. Cross-coupled damping coefficients had the same sign and were much smaller than direct coefficients. Measured static eccentricities suggested cross coupling stiffness exists for both pivot offsets, agreeing with dynamic measurements. Static stiffness measurements showed good agreement with the loaded, direct dynamic stiffness coefficients.

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Mechanisms and Mitigation of 3D Coupled Vibrations in Drilling with PDC Bits

10.2118/205904-ms ◽

2021 ◽

Author(s):

Shilin Chen ◽

Chris Propes ◽

Curtis Lanning ◽

Brad Dunbar

Keyword(s):

Torsional Oscillation ◽

Excitation Frequency ◽

Low Frequency ◽

Coupled Vibration ◽

Stick Slip ◽

Rock Interaction ◽

Bottom Hole ◽

New Type ◽

Design Characteristics ◽

Axial Resonance

Abstract In this paper we present a new type of vibration related to PDC bits in drilling and its mitigation: a vibration coupled in axial, lateral and torsional directions at a high common frequency (3D coupled vibration). The coupled frequency is as high as 400Hz. 3D coupled vibration is a new dysfunction in drilling operation. This type of vibration occurred more often than stick-slip vibration. Evidences reveal that the coupled frequency is an excitation frequency coming from the bottom hole pattern formed in bit/rock interaction. This excitation frequency and its higher order harmonics may excite axial resonance and/or torsional resonance of a BHA. The nature of 3D coupled vibration is more harmful than low frequency stick-slip vibration and high frequency torsional oscillation (HFTO). The correlation between the occurrence of 3D coupled vibration and bit design characteristics is studied. Being different from prior publications, we found the excitation frequency is dependent on bit design and the occurrence of 3D coupled vibration is correlated with bit design characteristics. New design guidlines have been proposed to reduce or to mitigate 3D coupled vibration.

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The Relationship between Vibratory Sensation and Body Surface Vibration Induced by Low-Frequency Noise

Journal of Low Frequency Noise Vibration and Active Control ◽

10.1260/026309202761019534 ◽

2002 ◽

Vol 21 (2) ◽

pp. 87-100 ◽

Cited By ~ 7

Author(s):

Yukio Takahashi ◽

Kazuo Kanada ◽

Yoshiharu Yonekawa

Keyword(s):

Body Surface ◽

Mechanical Vibration ◽

Low Frequency ◽

The Body ◽

Frequency Noise ◽

Low Frequency Noise ◽

Vibration Acceleration ◽

Surface Vibration ◽

Human Body Surface ◽

The Relationship

Human body surface vibration induced by low-frequency noise was measured at the forehead, the chest and the abdomen. At the same time, subjects rated their vibratory sensation at each of these locations. The relationship between the measured vibration on the body surface and the rated vibratory sensation was examined, revealing that the vibratory sensations perceived in the chest and abdomen correlated closely with the vibration acceleration levels of the body surface vibration. This suggested that a person exposed to low-frequency noise perceives vibration at the chest or abdomen by sensing the mechanical vibration that the noise induces in the body. At the head, on the other hand, it was found that the vibratory sensation correlated comparably with the vibration acceleration level of the body surface vibration and the sound pressure level of the noise stimulus. This finding suggested that the mechanism of perception of vibration in the head is different from that of the perception of vibratory sensation in the chest and the abdomen.

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Experimental Research about the Application of ER Elastomer in the Shock Absorber

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.641-642.371 ◽

2013 ◽

Vol 641-642 ◽

pp. 371-376 ◽

Cited By ~ 7

Author(s):

Shi Sha Zhu ◽

Xue Peng Qian ◽

Hao He ◽

Quan Fu Zhang

Keyword(s):

Electric Field ◽

External Electric Field ◽

Shock Absorber ◽

Hybrid Control ◽

Excitation Frequency ◽

Low Frequency ◽

Structural Vibration ◽

Shear Mode ◽

Response Performance ◽

Better Than

When the Electrorheological elastomer (ERE) is embedded into intelligence structure system, the structure damping and stiffness of the system can be changed quickly and reversibly under an external electric field. Thus, the application of the Electrorheological elastomer in the active and passive hybrid control of structural vibration has already attracted people's wide attention. In this paper, three types of ER elastomer were prepared based on barium titanate, starch, then the microstructure of ER elastomer was observed and the mechanical properties were analyzed; a shear mode ERE shock absorber was designed, the vibration response performance of which was experimentally evaluated under various excitation frequency with or without the applied field. The experimental results showed that the damping and stiffness of the shock absorber could be modified with a changing external electric field, whose macro-features was that the damping coefficient increased with the increase of the electric field, and the damping effect in the high frequency was better than in the low frequency.

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Nonlinear Combination Resonances in Cantilever Composite Plates

Volume 3A: 15th Biennial Conference on Mechanical Vibration and Noise — Vibration of Nonlinear, Random, and Time-Varying Systems ◽

10.1115/detc1995-0294 ◽

1995 ◽

Author(s):

Kyoyul Oh ◽

Ali H. Nayfeh

Keyword(s):

Natural Frequencies ◽

Excitation Frequency ◽

Power Spectra ◽

Low Frequency ◽

Composite Plates ◽

High Amplitude ◽

Mode Shapes ◽

Laser Vibrometer ◽

Combination Resonance ◽

Response Curves

Abstract We experimentally investigated nonlinear combination resonances in a graphite-epoxy cantilever plate having the configuration (–75/75/75/ – 75/75/ – 75)s. As a first step, we compared the natural frequencies and mode shapes obtained from the finite-element and experimental modal analyses. The largest difference in the obtained frequencies was 2.6%. Then, we transversely excited the plate and obtained force-response and frequency-response curves, which were used to characterize the plate dynamics. We acquired time-domain data for specific input conditions using an A/D card and used them to generate time traces, power spectra, pseudo-state portraits, and Poincaré maps. The data were obtained with an accelerometer monitoring the excitation and a laser vibrometer monitoring the plate response. We observed the external combination resonance Ω≈12(ω2+ω5) and the internal combination resonance Ω≈ω8≈12(ω2+ω13), where the ωi are the natural frequencies of the plate and Ω is the excitation frequency. The results show that a low-amplitude high-frequency excitation can produce a high-amplitude low-frequency motion.

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Low-Frequency Vibration Sensor with a Sub-nm Sensitivity Using a Bidomain Lithium Niobate Crystal

Sensors ◽

10.3390/s19030614 ◽

2019 ◽

Vol 19 (3) ◽

pp. 614 ◽

Cited By ~ 8

Author(s):

Ilya Kubasov ◽

Aleksandr Kislyuk ◽

Andrei Turutin ◽

Alexander Bykov ◽

Dmitry Kiselev ◽

...

Keyword(s):

Lithium Niobate ◽

Excitation Frequency ◽

Low Frequency ◽

Vibration Sensor ◽

Gravitational Acceleration ◽

Frequency Sensor ◽

Linear Behavior ◽

Low Frequency Vibration ◽

Acceleration Amplitude ◽

Vibrational Excitations

We present a low-frequency sensor for the detection of vibrations, with a sub-nm amplitude, based on a cantilever made of a single-crystalline lithium niobate (LiNbO3) plate, with a bidomain ferroelectric structure. The sensitivity of the sensor-to-sinusoidal vibrational excitations was measured in terms of displacement as well as of acceleration amplitude. We show a linear behavior of the response, with the vibrational displacement amplitude in the entire studied frequency range up to 150 Hz. The sensitivity of the developed sensor varies from minimum values of 20 μV/nm and 7 V/g (where g = 9.81 m/s2 is the gravitational acceleration), at a frequency of 23 Hz, to peak values of 92.5 mV/nm and 2443 V/g, at the mechanical resonance of the cantilever at 97.25 Hz. The smallest detectable vibration depended on the excitation frequency and varied from 100 nm, at 7 Hz, to 0.1 nm, at frequencies above 38 Hz. Sensors using bidomain lithium niobate single crystals, as sensitive elements, are promising for the detection of ultra-weak low-frequency vibrations in a wide temperature range and in harsh environments.

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A Study on the Leakage and Rotordynamic Performance of a Long Labyrinth Seal Under Mainly Air Conditions

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4045257 ◽

2019 ◽

Vol 141 (12) ◽

Cited By ~ 2

Author(s):

Min Zhang ◽

Dara W. Childs

Keyword(s):

Silicone Oil ◽

Dynamic Stiffness ◽

Excitation Frequency ◽

Labyrinth Seal ◽

System Stability ◽

Test Fluid ◽

Liquid Volume ◽

Frequency Dependent ◽

Frequency Independent ◽

The Impact

Abstract This paper investigates the impact of liquid presence in air on the leakage and rotordynamic coefficients of a long (length-to-diameter ratio L/D = 0.747) teeth-on-stator labyrinth seal. The test fluid is a mixture of air and silicone oil (PSF-5cSt). Tests are carried out at inlet pressure Pi = 62.1 bars, three pressure ratios from 0.21 to 0.46, three speeds from 10 to 20 krpm, and six inlet liquid volume fractions (LVFs) from 0% to 15%. Complex dynamic-stiffness coefficients Hij are measured. The real parts of Hij are too frequency dependent to be fitted by frequency-independent stiffness and virtual-mass coefficients. Therefore, this paper presents frequency-dependent direct stiffness KΩ and cross-coupled stiffness kΩ. The imaginary parts of Hij produce frequency-independent direct damping C. Test results show that, under both pure- and mainly air conditions, the leakage mass flowrate m˙ of the test seal steadily increases as inlet LVF increases. KΩ is negative under all test conditions, and the magnitude of KΩ increases as inlet LVF increases, leading to a larger negative centering force on the associated compressor rotor. Under pure-air conditions, kΩ is a small negative value. Injecting oil into the air increases kΩ slightly and make the magnitude of kΩ closer to zero. Under mainly air conditions, increasing inlet LVF from 2% to 15% has little impact on kΩ. C normally increases as inlet LVF increases. The value of the effective damping Ceff = C − kΩ/Ω near 0.5ω is of significant interest to the system stability since an unstable centrifugal compressor may precess at approximately 0.5ω. Ω denotes the excitation frequency. The oil presence in the air has little impact on the value of Ceff near 0.5ω. Also, the liquid presence does not change the insensitiveness of m˙, KΩ, kΩ, C, and Ceff to change in ω; i.e., under both pure- and mainly air conditions, changes in ω has little impact on m˙, KΩ, kΩ, C, and Ceff.

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NONLINEAR LOW FREQUENCY WATER WAVES IN A CYLINDRICAL SHELL

Modern Physics Letters B ◽

10.1142/s0217984905010049 ◽

2005 ◽

Vol 19 (28n29) ◽

pp. 1615-1618 ◽

Cited By ~ 4

Author(s):

H. W. PENG ◽

D. J. WANG ◽

C. B. LEE

Keyword(s):

High Frequency ◽

Water Waves ◽

Water Wave ◽

Excitation Frequency ◽

Low Frequency ◽

Viscous Effect ◽

First Approximation ◽

Quantitative Results ◽

High Frequency Excitation ◽

Frequency Excitation

The experiment was carried out to study the low frequency surface waves due to the horizontal high frequency excitation. The feature of the phenomenon was that the big amplitude axisymmetric surface wave frequency was typically about 1/50 of the excitation frequency. The viscous effect of water was neglected as a first approximation in the earlier papers on this subject. In contrast, we found the viscosity was important to achieve the low frequency water wave with the cooperation of hundreds of "finger" waves. Photographs were taken with stroboscopic lighting and thereafter relevant quantitative results were obtained based on the measurements with Polytec Scanning Vibrometer PSV 400.

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