Laser Vibrometers and Contacting Transducers, Target Rotation and Six Degree-of-Freedom Vibration: What Do We Really Measure?

Bell, John Roger; Rothberg, Steve

doi:10.1006/jsvi.2000.3053

Cited by 52 publications

(45 citation statements)

References 11 publications

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“…In our approach, we have measured the transverse displacement distribution of a solid substrate surface and across the interface of a fluid droplet due to the propagation of a surface acoustic wave ͑SAW͒ as it is being excited at 30 MHz; neither the in-plane component of the Rayleigh SAW nor the resulting capillary wave can be detected. 27 Even so, much useful information can be gathered, for instance, the interaction of the propagating acoustic wave with fluid droplets, as shown in Fig. 1.…”

Section: Resultsmentioning

confidence: 99%

Using laser Doppler vibrometry to measure capillary surface waves on fluid-fluid interfaces

Friend

Yeo

2010

Biomicrofluidics

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Capillary wave phenomena are challenging to study, especially for microfluidics where the wavelengths are short, the frequencies are high, and the frequency distribution is rarely confined to a narrow range, let alone a single frequency. Those that have been studying Faraday capillary waves generated by vertical oscillation have chosen to work at larger scales and at low frequencies as a solution to this problem, trading simplicity in measurement for issues with gravity, boundary conditions, and the fidelity of the subharmonic capillary wave motion. Laser Doppler vibrometry using a Mach-Zehnder interferometer is an attractive alternative: The interface's motion can be characterized at frequencies up to 40 MHz and displacements of as little as a few tens of picometers.

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Section: Resultsmentioning

confidence: 99%

Using laser Doppler vibrometry to measure capillary surface waves on fluid-fluid interfaces

Friend

Yeo

2010

Biomicrofluidics

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“…First, the LDV directly measures vibrational particle velocity along the laser path; this means that the fluid surface must be nearly perpendicular to the incident beam, restricting the area of the drop that we can measure to the central part to avoid substantial errors in measurement. 50 Second, the signal returned by the vibrometer will contain information from all of the laser energy to enter the detector; this includes not only the desired portion that has reflected from the fluid surface but also any light that has passed through the drop and reflected off the substrate. Shrinking the depth of field eliminates this issue; the fluid may also be colored to absorb any light passing through the surface, although the coloring agent will change the properties of the fluid and lower the intensity of reflected light.…”

Section: ■ Generating and Measuring Microscale Capillary Wavesmentioning

confidence: 99%

Microscale Capillary Wave Turbulence Excited by High Frequency Vibration

Blamey

Yeo²,

Friend

2013

Langmuir

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Low frequency (O(10 Hz−10 kHz)) vibration excitation of capillary waves has been extensively studied for nearly two centuries. Such waves appear at the excitation frequency or at rational multiples of the excitation frequency through nonlinear coupling as a result of the finite displacement of the wave, most often at one-half the excitation frequency in so-called Faraday waves and twice this frequency in superharmonic waves. Less understood, however, are the dynamics of capillary waves driven by high-frequency vibration (>O(100 kHz)) and small interface length scales, an arrangement ideal for a broad variety of applications, from nebulizers for pulmonary drug delivery to complex nanoparticle synthesis. In the few studies conducted to date, a marked departure from the predictions of classical Faraday wave theory has been shown, with the appearance of broadband capillary wave generation from 100 Hz to the excitation frequency and beyond, without a clear explanation. We show that weak wave turbulence is the dominant mechanism in the behavior of the system, as evident from wave height frequency spectra that closely follow the Rayleigh−Jeans spectral response η ≈ ω −17/12 as a consequence of a period-halving, weakly turbulent cascade that appears within a 1 mm water drop whether driven by thickness-mode or surface acoustic Rayleigh wave excitation. However, such a cascade is one-way, from low to high frequencies. The mechanism of exciting the cascade with high-frequency acoustic waves is an acoustic streaming-driven turbulent jet in the fluid bulk, driving the fundamental capillary wave resonance through the well-known coupling between bulk flow and surface waves. Unlike capillary waves, turbulent acoustic streaming can exhibit subharmonic cascades from high to low frequencies; here it appears from the excitation frequency all the way to the fundamental modes of the capillary wave at some four orders of magnitude in frequency less than the excitation frequency, enabling the capillary weakly turbulent wave cascade to form from the fundamental capillary wave upward.

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“…For surfaces generating fully developed speckle patterns (e.g. Ra 1 μm and the surface treated with retro-reflective tape), there is proven insensitivity to shaft out-of-roundness [23].…”

Section: Continuous Rotation: Experimental Arrangement For Radial Vibmentioning

confidence: 99%

“…In addition, the experimental methods must accommodate both single beam laser vibrometers, which measure all translational vibrations [23], and parallel beam laser vibrometers, which measure all angular vibrations [24].…”

Section: Introductionmentioning

confidence: 99%

Methods for the quantification of pseudo-vibration sensitivities in laser vibrometry

Martín¹,

Rothberg²

2011

Meas. Sci. Technol.

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Pseudo-vibration sensitivities in laser vibrometry are the consequence of measurement noise generated by surface motions other than that on-axis with the incident laser beam(s), such as transverse and tilt vibrations or rotation. On rougher surfaces, laser speckle is the cause but similar noise is observed in measurements from smoother surfaces. This paper's principal aim is to introduce two experimental methods for quantification, including dedicated data processing, to deliver sensitivities in three forms: a spectral map, a

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Laser Vibrometers and Contacting Transducers, Target Rotation and Six Degree-of-Freedom Vibration: What Do We Really Measure?

Cited by 52 publications

References 11 publications

Using laser Doppler vibrometry to measure capillary surface waves on fluid-fluid interfaces

Using laser Doppler vibrometry to measure capillary surface waves on fluid-fluid interfaces

Microscale Capillary Wave Turbulence Excited by High Frequency Vibration

Methods for the quantification of pseudo-vibration sensitivities in laser vibrometry

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