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URN etd-1008112-092815
Author Je-Cheng Kuo
Author's Email Address No Public.
Statistics This thesis had been viewed 5348 times. Download 342 times.
Department IAMPUT
Year 2012
Semester 1
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Turbulent flows induced by the interaction of continuous internal waves and a sloping bottom
Date of Defense 2012-10-01
Page Count 111
Keyword
  • continuous internal waves
  • Empirical Mode Decomposition
  • breaking waves
  • turbulence
  • energy dissipation rate
  • Abstract Internal waves occur in the interface between two layers of fluids with density
    stratification. In order to better understand the characteristics of continuous internal
    waves, a series of experiments were conducted in a laboratory tank. The upper and
    lower layers are fresh water of 15 cm thick and salt water of 30 cm thick, respectively.
    The periods of internal waves are 2.5, 5.5 and 6.6 sec. A micro-ADV is used to
    measure velocity profiles. Wave profiles at the density interface and the free surface
    are monitored respectively by an ultrasonic and capacitance wave gauges. Our results
    indicate that particle velocities (u and w) above and below the density interface have
    opposite directions. The speed is peaked near the density interface and it becomes
    weaker further away from the interface. Empirical Mode Decomposition is used to
    remove noise from the observed particle velocities, and the period is consistent with
    those derived from the interface elevations. The observed particle velocities also
    compare favorably with the theoretical results.
    When internal waves propagate without the interference of a sloping bottom, the
    turbulence induced is rather insignificant. The turbulence is more significant only near
    the density interface. With the existence of a sloping bottom, the internal waves
    gradually shoal and deform, the crest becomes sharp and steep, finally the waves
    become unstable, break and overturn. In this study the effect of bottom slope and the
    steepness of internal waves on the reflectivity of incoming waves are investigated.
    The reflectivity is smaller with gentler slope, and it increases and reaches a constant
    value with steeper slopes. The observed energy dissipation rateεis higher near the
    slope. Three methods were used to estimate the energy dissipation rate and shear
    stress; namely, the inertial dissipation, the TKE and auto-correlation method. Theε
    estimated from the auto-correlation method is larger than that from the other two
    methods, but their trend is similar. The energy dissipation rate is found to increase
    with a gentler sloping bottom.
    Advisory Committee
  • Guan-Yu Chen - chair
  • I-Huan Lee - co-chair
  • Chih-Min Hsieh - co-chair
  • Ruo-Shan Tseng - advisor
  • Files
  • etd-1008112-092815.pdf
  • indicate access worldwide
    Date of Submission 2012-10-08

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