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Head-on collision of internal waves with trapped cores
Maderich, Vladimir,Jung, Kyung Tae,Terletska, Kateryna,Kim, Kyeong Ok Copernicus GmbH 2017 Nonlinear processes in geophysics Vol.24 No.4
<P><p><strong>Abstract.</strong> The dynamics and energetics of a head-on collision of internal solitary waves (ISWs) with trapped cores propagating in a thin pycnocline were studied numerically within the framework of the Navier-Stokes equations for a stratified fluid. The peculiarity of this collision is that it involves trapped masses of a fluid. The interaction of ISWs differs for three classes of ISWs: (i) weakly non-linear waves without trapped cores, (ii) stable strongly non-linear waves with trapped cores, and (iii) shear unstable strongly non-linear waves. The wave phase shift of the colliding waves with equal amplitude grows as the amplitudes increase for colliding waves of classes (i) and (ii) and remains almost constant for those of class (iii). The excess of the maximum run-up amplitude, normalized by the amplitude of the waves, over the sum of the amplitudes of the equal colliding waves increases almost linearly with increasing amplitude of the interacting waves belonging to classes (i) and (ii); however, it decreases somewhat for those of class (iii). The colliding waves of class (ii) lose fluid trapped by the wave cores when amplitudes normalized by the thickness of the pycnocline are in the range of approximately between 1 and 1.75. The interacting stable waves of higher amplitude capture cores and carry trapped fluid in opposite directions with little mass loss. The collision of locally shear unstable waves of class (iii) is accompanied by the development of instability. The dependence of loss of energy on the wave amplitude is not monotonic. Initially, the energy loss due to the interaction increases as the wave amplitude increases. Then, the energy losses reach a maximum due to the loss of potential energy of the cores upon collision and then start to decrease. With further amplitude growth, collision is accompanied by the development of instability and an increase in the loss of energy. The collision process is modified for waves of different amplitudes because of the exchange of trapped fluid between colliding waves due to the conservation of momentum.</p> </P>
Frontal collision of internal solitary waves of first mode
Terletska, K.,Jung, K.T.,Maderich, V.,Kim, K.O. Elsevier 2018 Wave motion Vol.77 No.-
<P><B>Abstract</B></P> <P>The dynamics and energetics of a frontal collision of internal solitary waves (ISW) of first mode in a fluid with two homogeneous layers separated by a thin interfacial layer are studied numerically within the framework of the Navier–Stokes equations for stratified fluid. It was shown that the head-on collision of internal solitary waves of small and moderate amplitude results in a small phase shift and in the generation of dispersive wave train travelling behind the transmitted solitary wave. The phase shift grows as amplitudes of the interacting waves increase. The maximum run-up amplitude during the wave collision reaches a value larger than the sum of the amplitudes of the incident solitary waves. The excess of the maximum run-up amplitude over the sum of the amplitudes of the colliding waves grows with the increasing amplitude of interacting waves of small and moderate amplitudes whereas it decreases for colliding waves of large amplitude. Unlike the waves of small and moderate amplitudes collision of ISWs of large amplitude was accompanied by shear instability and the formation of Kelvin–Helmholtz (KH) vortices in the interface layer, however, subsequently waves again become stable. The loss of energy due to the KH instability does not exceed 5%–6%. An interaction of large amplitude ISW with even small amplitude ISW can trigger instability of larger wave and development of KH billows in larger wave. When smaller wave amplitude increases the wave interaction was accompanied by KH instability of both waves.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Frontal collision of internal solitary waves is studied numerically. </LI> <LI> Collision results in a wave phase shift growing with wave amplitude. </LI> <LI> Nonlinear components of runup for waves of small and large amplitudes differs. </LI> <LI> Collision of waves of large amplitude leads to the shear instability. </LI> <LI> Collision of small and large amplitude waves triggers the shear instability. </LI> </UL> </P>
The marine <i>kd</i> and water/sediment interaction problem
Periá,ñ,ez, R.,Brovchenko, I.,Jung, K.T.,Kim, K.O.,Maderich, V. Elsevier 2018 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.192 No.-
<P><B>Abstract</B></P> <P>The behavior of marine distribution coefficients is analyzed with the help of numerical experiments and analytical solutions of equations describing kinetic models for uptake/release of radionuclides. The difficulties in measuring true k<SUB>d</SUB> in a marine environment perturbed by an external radionuclide source are highlighted. Differences between suspended matter and bed sediment k<SUB>d</SUB> are analyzed. The performances of different kinetic models (1-step/2step; single-layer/multi-layer) are studied in model/model and model/experiment comparisons. Implications for the use of models to assess radioactive contamination after an emergency are given; as well as recommendations when k<SUB>d</SUB> data are compiled in order to create a useful database.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Equilibrium in radionuclide partition between water and sediment seldom found in the sea. </LI> <LI> Differences between suspended matter and bed sediment kd highlighted. </LI> <LI> One step and two step kinetic models performances compared. </LI> <LI> Single layer and multi-layer models compared. </LI> <LI> Formulation to deal with changes in salinity and pH provided. </LI> </UL> </P>
Periá,ñ,ez, R.,Bezhenar, R.,Brovchenko, I.,Jung, K.T.,Kamidara, Y.,Kim, K.O.,Kobayashi, T.,Liptak, L.,Maderich, V.,Min, B.I.,Suh, K.S. Elsevier Applied Science Publishers 2019 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.198 No.-
<P><B>Abstract</B></P> <P>A number of marine radionuclide dispersion models (both Eulerian and Lagrangian) were applied to simulate <SUP>137</SUP>Cs releases from Fukushima Daiichi nuclear power plant accident in 2011 over the Pacific at oceanic scale. Simulations extended over two years and both direct releases into the ocean and deposition of atmospheric releases on the ocean surface were considered. Dispersion models included an embedded biological uptake model (BUM). Three types of BUMs were used: equilibrium, dynamic and allometric. Model results were compared with <SUP>137</SUP>Cs measurements in water (surface, intermediate and deep layers), sediment and biota (zooplankton, non-piscivorous and piscivorous fish). A reasonable agreement in model/model and model/data comparisons was obtained.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Marine dispersion models applied to Fukushima releases in the Pacific Ocean. </LI> <LI> Biological uptake model included within physical dispersion models. </LI> <LI> Model results compared with measurements in water, sediments and biota. </LI> <LI> Generally good agreement in model/model and model/data comparisons. </LI> </UL> </P>