Amplitude decay and energy dissipation due to the interaction of internal solitary waves with a triangular obstacle in a two-layer fluid system: the blockage parameter

Experiments were carried out in a wave flume to examine the propagation of depression-type internal solitary waves (ISWs) over a submerged triangular-shaped obstacle. We observed the distortion and breaking of the ISW depression in a two-layer stratified fluid system as induced by the obstacle on the bottom. Physical factors, such as the amplitude of the wave, the thickness of the two layers, and the height of the submerged obstacle were utilized in our analysis of the wave–obstacle interaction. Wave breaking was determined in relation to input parameters arranged before the experimental runs. A classification scheme based on the blockage parameter ζ was proposed. The various degrees of ISW-obstacle interaction were visually classified with three schematic forms (ζ < 0.55 for a weak encounter; 0.55 < ζ < 0.7 for a moderate encounter; and 0.7 < ζ for wave breaking). Furthermore, the reflection and transmission coefficients were utilized to explore the resultant influence on changes in amplitude and energy of an ISW. The wave characteristics (e.g., amplitude-based wave reflection, energy-based reflection, amplitude-based transmission, and energy-based transmission) during the wave–obstacle interaction showed an approximately linear relation with the blockage parameter. Influenced by the submarine obstacle, the transmitted waves were found to always consist of a leading pulse (solitary wave) followed by a dispersive wave train. Moreover, due to bottom friction the energy budget of the leading pulse was reduced by a factor of at least 5% which could approach 50% in cases with strong breaking.

[1]  D. Korteweg,et al.  XLI. On the change of form of long waves advancing in a rectangular canal, and on a new type of long stationary waves , 1895 .

[2]  J. Miles,et al.  On interfacial solitary waves over slowly varying topography , 1984, Journal of Fluid Mechanics.

[3]  D. Renouard,et al.  Internal solitons on the pycnocline: generation, propagation, and shoaling and breaking over a slope , 1985, Journal of Fluid Mechanics.

[4]  K. Helfrich,et al.  On long nonlinear internal waves over slope-shelf topography , 1986, Journal of Fluid Mechanics.

[5]  K. Helfrich.  Internal solitary wave breaking and run-up on a uniform slope , 1992, Journal of Fluid Mechanics.

[6]  Frank Wessels,et al.  Interaction of Internal Waves with a Topographic Sill in a Two-Layered Fluid , 1996 .

[7]  Hervé Michallet,et al.  Experimental study of interfacial solitary waves , 1998, Journal of Fluid Mechanics.

[8]  I. Robinson,et al.  Role of surface films in ERS SAR signatures of internal waves , 1998 .

[9]  Antony K. Liu,et al.  Evolution of nonlinear internal waves in the East and South , 1998 .

[10]  S. V. Kijashko,et al.  Role of surface films in ERS SAR signatures of internal waves on the shelf: 1. Short-period internal waves , 1998 .

[11]  Antony K. Liu,et al.  A study of internal waves in the China Seas and Yellow Sea using SAR , 2000 .

[12]  Baroclinic solitary water waves in a two-layer fluid system with diffusive interface , 2001 .

[13]  K. Hutter,et al.  Generation of second mode solitary waves by the interaction of a first mode soliton with a sill , 2001 .

[14]  On the breaking of internal solitary waves at a ridge , 2002, Journal of Fluid Mechanics.

[15]  Chen-Yuan Chen.  An experimental study of stratified mixing caused by internal solitary waves in a two-layered fluid system over variable seabed topography , 2007 .

[16]  Chen-Yuan Chen,et al.  An investigation on internal solitary waves in a two-layer fluid: Propagation and reflection from steep slopes , 2007 .