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Research Papers

Vibration Analysis of the Free-Falling Microstructure Profiler

[+] Author and Article Information
Yuhong Liu

Key Laboratory of Mechanism Theory and
Equipment Design of Ministry of Education,
School of Mechanical Engineering,
Tianjin University,
Tianjin 300072, China
e-mail: yuhong_liu@tju.edu.cn

Yanpeng Yang

School of Mechanical Engineering,
Tianjin University,
Tianjin 300072, China
e-mail: 1224874059@qq.com

Yanhui Wang

Key Laboratory of Mechanism Theory and
Equipment Design of Ministry of Education,
School of Mechanical Engineering,
Tianjin University,
Tianjin 300072, China
e-mail: yanhuiwang@tju.edu.cn

Shiquan Lan

School of Mechanical Engineering,
Tianjin University,
Tianjin 300072, China
e-mail: yxlx2010@163.com

Shuxin Wang

Key Laboratory of Mechanism Theory and
Equipment Design of Ministry of Education,
School of Mechanical Engineering,
Tianjin University,
Tianjin 300072, China
e-mail: shuxinw@tju.edu.cn

Lianhong Zhang

Key Laboratory of Mechanism Theory and
Equipment Design of Ministry of Education,
School of Mechanical Engineering,
Tianjin University,
Tianjin 300072, China
e-mail: zhanglh@tju.edu.cn

1Corresponding author.

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received October 7, 2015; final manuscript received July 28, 2016; published online September 8, 2016. Assoc. Editor: Marco Amabili.

J. Vib. Acoust 138(6), 061012 (Sep 08, 2016) (13 pages) Paper No: VIB-15-1423; doi: 10.1115/1.4034378 History: Received October 07, 2015; Revised July 28, 2016

Free-falling microstructure profiler (FFMP) is the most effective platform for measuring ocean microstructure turbulence. Vibration is the key factor of influencing the accuracy of the measurement of the shear sensor mounted on the leading end of the FFMP. In the present work, vibration behavior of an FFMP called FFMP1000 was studied through fluid–structure interaction (FSI) simulations and field trials. Vibration characteristics and mechanism of the FFMP1000 were also discussed. Results showed that motion of the FFMP was like a compound pendulum oscillation, and was caused by vortex shedding at the trailing end of the FFMP. Empirical formulas used to predict the oscillation of the FFMP were deduced based on the characteristics of motion behavior and confirmed through sea trials. The present achievement provides scientific guidance for designing optimal hydrodynamic hull shape of the FFMP. It is also useful to estimate the low end detection limit of the FFMP and to modify the turbulence kinetic energy dissipation rate during ocean observations.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Schematic of the FFMP1000 profiler

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Fig. 4

Data transmission schemes at the fluid–structure interface

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Fig. 3

Meshing schematics: (a) scheme I and (b) scheme II

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Fig. 8

Attitudes of two limit locations in half a cycle corresponding t1 and t2 in Fig. 5: (a) t1 = 26.10 s and (b) t2 = 29.15 s

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Fig. 2

Schematic of geometry of the FFMP1000, the computational domain, and the boundary conditions [25]

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Fig. 10

Vorticity contour of different cross sections in the wake at a time. xx mm means that distance between the cross section and the trailing end of the profiler is xx mm.

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Fig. 11

Curve of the transverse force versus time at Y-direction

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Fig. 12

Spectra of the vibration velocity (a) and the transverse force (b)

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Fig. 13

Flow field around the front part of the profiler

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Fig. 15

Curves of the acceleration and frequency of FIV versus moment of inertia J with Mx=140.6  N⋅m and V = 0.65 m/s

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Fig. 16

Curves of the acceleration and frequency of FIV versus free-falling speed V with Mx=140.6  N⋅m and J  = 72.6 kg·m2

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Fig. 17

Schematic of the profiler and the steel rings

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Fig. 18

Error distributions of FIV frequencies and accelerations obtained from FSI numerical method and from empirical formula

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Fig. 19

Comparison between the vibration frequencies obtained from sea trials and empirical formula

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Fig. 5

Kinetic dissipation spectra (coarse curve) and their corresponding Nasmyth spectra (smooth curve) for different depth regions of the shear signal detected by FFMP1000 profiler: (a) ε=3.0387×10−8 W/kg (kc = 65 cpm), (b) ε=1.0103×10−9 W/kg (kc = 27 cpm), (c) ε=6.0061×10−10 W/kg (kc = 23 cpm), and (d) ε=2.6558×10−10 W/kg (kc = 19 cpm). (Note: kc is the wavenumber.)

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Fig. 6

The acceleration signals obtained from the FSI calculation and sea trials [25]

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Fig. 20

Rotation of the unconstrained cylinder with the rotation axis vertical with its axis

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Fig. 21

Rotation axis corresponding to the minimum moment of inertia of the profiler

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Fig. 7

Curves of the displacement and velocity at the monitored point A in Y-direction

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Fig. 9

The wake field of the profiler in various times: (a) t = 24.5 s, (b) t = 26.1 s, (c) t = 27.6 s, and (d) t = 29.2 s

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Fig. 14

Curves of the acceleration and frequency of FIV versus restoring moment Mx with J  = 72.6 kg·m2 and V = 0.65 m/s

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