scholarly journals Numerical modelling of disintegration of basin-scale internal waves in a tank filled with stratified water

2005 ◽  
Vol 12 (6) ◽  
pp. 955-964 ◽  
Author(s):  
N. Stashchuk ◽  
V. Vlasenko ◽  
K. Hutter
Keyword(s):  
Numerical Model ◽  
Internal Waves ◽  
Solitary Waves ◽  
Mixing Processes ◽  
Wave Regime ◽  
Stratified Lakes ◽  
Low Dissipation ◽  
Basin Scale ◽  
Shear Instabilities ◽  
Set Up

Abstract. We present the results of numerical experiments performed with the use of a fully non-linear non-hydrostatic numerical model to study the baroclinic response of a long narrow tank filled with stratified water to an initially tilted interface. Upon release, the system starts to oscillate with an eigen frequency corresponding to basin-scale baroclinic gravitational seiches. Field observations suggest that the disintegration of basin-scale internal waves into packets of solitary waves, shear instabilities, billows and spots of mixed water are important mechanisms for the transfer of energy within stratified lakes. Laboratory experiments performed by D. A. Horn, J. Imberger and G. N. Ivey (JFM, 2001) reproduced several regimes, which include damped linear waves and solitary waves. The generation of billows and shear instabilities induced by the basin-scale wave was, however, not sufficiently studied. The developed numerical model computes a variety of flows, which were not observed with the experimental set-up. In particular, the model results showed that under conditions of low dissipation, the regimes of billows and supercritical flows may transform into a solitary wave regime. The obtained results can help in the interpretation of numerous observations of mixing processes in real lakes.

scholarly journals Transformation and disintegration of strongly nonlinear internal waves by topography in stratified lakes

2002 ◽  
Vol 20 (12) ◽  
pp. 2087-2103 ◽  
Author(s):  
V. I. Vlasenko ◽  
K. Hutter
Keyword(s):  
Internal Waves ◽  
Benthic Boundary Layer ◽  
Deep Part ◽  
Variable Depth ◽  
Wave Evolution ◽  
Stratified Lakes ◽  
Short Period ◽  
Basin Scale ◽  
Wave Trains ◽  
Solitary Internal Waves

Abstract. For many lakes the nonlinear transfer of energy from basin-scale internal waves to short-period motions, such as solitary internal waves (SIW) and wave trains, their successive interaction with lake boundaries, as well as over-turning and breaking are important mechanisms for an enhanced mixing of the turbulent benthic boundary layer. In the present paper, the evolution of plane SIWs in a variable depth channel, typical of a lake of variable depth, is considered, with the basis being the Reynolds equations. The vertical fluid stratification, wave amplitudes and bottom parameters are taken close to those observed in Lake Constance, a typical mountain lake. The problem is solved numerically. Three different scenarios of a wave evolution over variable bottom topography are examined. It is found that the basic parameter controlling the mechanism of wave evolution is the ratio of the wave amplitude to the distance from the metalimnion to the bottom d. At sites with a gentle sloping bottom, where d is small, propagating (weak or strong) internal waves adjust to the local ambient conditions and preserve their form. No secondary waves or wave trains arise during wave propagation from the deep part to the shallow water. If the amplitude of the propagating waves is comparable with the distance between the metalimnion and the top of the underwater obstacle ( d ~ 1), nonlinear dispersion plays a key role. A wave approaching the bottom feature splits into a sequence of secondary waves (solitary internal waves and an attached oscillating wave tail). The energy of the SIWs above the underwater obstacle is transmitted in parts from the first baroclinic mode, to the higher modes. Most crucially, when the internal wave propagates from the deep part of a basin to the shallow boundary, a breaking event can arise. The cumulative effects of the nonlinearity lead to a steepening and overturning of the rear wave face over the inclined bottom and to the formation of a turbulent jet propagating upslope. Some time later, after the breaking event, a new stable stratification is formed at the site of wave destruction. The breaking criterion of ISWs is discussed.Key words. Oceanography: general (limnology; numerical modeling) – Oceanography: physical (internal and inertial waves)

scholarly journals Numerical Aspects of Particle-in-Cell Simulations for Plasma-Motion Modeling of Electric Thrusters

Aerospace ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 138
Author(s):  
Giuseppe Gallo ◽  
Adriano Isoldi ◽  
Dario Del Gatto ◽  
Raffaele Savino ◽  
Amedeo Capozzoli ◽  
...  
Keyword(s):  
Numerical Model ◽  
Computing Time ◽  
Computational Time ◽  
Electric Motors ◽  
Motion Modeling ◽  
Particle In Cell ◽  
Computing Platform ◽  
Hall Effect Thruster ◽  
Set Up ◽  
Pic Code

The present work is focused on a detailed description of an in-house, particle-in-cell code developed by the authors, whose main aim is to perform highly accurate plasma simulations on an off-the-shelf computing platform in a relatively short computational time, despite the large number of macro-particles employed in the computation. A smart strategy to set up the code is proposed, and in particular, the parallel calculation in GPU is explored as a possible solution for the reduction in computing time. An application on a Hall-effect thruster is shown to validate the PIC numerical model and to highlight the strengths of introducing highly accurate schemes for the electric field interpolation and the macroparticle trajectory integration in the time. A further application on a helicon double-layer thruster is presented, in which the particle-in-cell (PIC) code is used as a fast tool to analyze the performance of these specific electric motors.

Water movements in lakes during summer stratification; evidence from the distribution of temperature in Windermere

1952 ◽  
Vol 236 (635) ◽  
pp. 355-398 ◽  
Keyword(s):  
Internal Waves ◽  
Mathematical Form ◽  
Historical Survey ◽  
Thermo Electric ◽  
Stratified Lakes ◽  
Natural Lakes ◽  
Complicating Factors ◽  
Internal Seiches ◽  
Theoretical Analyses ◽  
Scottish Lochs

The first part of this paper is taken up with an historical survey of the relatively few observations, some detailed and some less so, of internal seiches (internal standing waves) in lakes. After a description of the thermo-electric thermometer employed, there follow details and illustrations of the evidence, from temperature observations, for such internal waves in the northern basin of Windermere. Two main phases could be distinguished: (i) motion under wind stress leading to quasi-steady states with some or all of the isotherms tilted; (ii) internal seiche motion which developed after the wind had dropped. These observations confirm the findings of Wedderburn and his collaborators on the Scottish Lochs (1907-15). The results from Windermere are presented, not because any such confirmation is necessary, but in order to secure belated recognition of the fact that Wedderburn’s ‘ temperature seiche ’ is not an isolated phenomenon, but is an everyday feature of movement in stratified lakes subject to wind action. As this movement is an important and largely unrecognized factor in lake environment, this paper is addressed mainly to limnologists. In its latter part, results of theoretical analyses of a detailed series of observations are presented in non-mathematical form. The applicability of a theory of oscillations in a basin with three layers of differing density (set out in an appendix by M. S. Longuet-Higgins) is tested by comparing theoretical and observed deflexions of selected isotherms from their equilibrium levels, resulting from internal waves after a gale. This theory also enables horizontal components of velocity and displacement to be calculated for each layer. Complicating factors in natural lakes are enumerated, and the influence of internal waves on lake biology and sedimentation is discussed.

Study Based on FLUENT of Broken Internal Waves in Different Slope Angles

2014 ◽  
Vol 638-640 ◽  
pp. 1769-1777
Author(s):  
Zi Tong Yan ◽  
Liang Qiu Cheng ◽  
Feng Yi ◽  
Tai Zhong Chen ◽  
Han Sun ◽  
...  
Keyword(s):  
Internal Waves ◽  
Solitary Waves ◽  
Wave Breaking ◽  
Slope Angle ◽  
Ecological Environment ◽  
Internal Solitary Waves ◽  
Propagation Process ◽  
Numerical Wave Flume ◽  
Wave Flume ◽  
New Methods

Internal waves will break in the process of communication, the broken will make water in upper and lower mixing, which has significant influence on the hydrodynamic and layered characteristics of density stratification of the water. In order to reveal the propagation of internal solitary waves, a 3d numerical wave flume was built. The research of the propagation of internal solitary waves in the regular topography and broken on slopes was based on FLUENT. Comparing the fragmentation degree of different slope angle and researching the energy dissipation of the wave propagation process , which are supposed to successfully match the results with the experiment results, can provide new methods and means for the further study of internal wave breaking characteristics and the improvement of ecological environment of water bodies.

scholarly journals Spatially Broad Observations of Internal Waves in the Upper Ocean at the Hawaiian Ridge

2006 ◽  
Vol 36 (6) ◽  
pp. 1085-1103 ◽  
Author(s):  
Joseph P. Martin ◽  
Daniel L. Rudnick ◽  
Robert Pinkel
Keyword(s):  
Numerical Model ◽  
Energy Density ◽  
Potential Energy ◽  
Internal Waves ◽  
Upper Ocean ◽  
Mean Square ◽  
The South ◽  
South Side ◽  
Topographic Slope ◽  
Hawaiian Ridge

Abstract The density and current structure at the Hawaiian Ridge was observed using SeaSoar and Doppler sonar during a survey extending from Oahu to Brooks Banks. Across- and along-ridge changes in internal wave statistics in the upper ocean within 200 km of the ridge are investigated. Internal waves with trough-to-crest amplitude as large as 60 m and horizontal wavelength of about 50 km are observed repeatedly in across-ridge sections of potential density. Within 150 km of the ridge, kinetic and potential energy density exceed open-ocean values with maxima about 10 times Garrett–Munk levels. In the Kauai Channel (KC), the kinetic energy density is largest along an M2 internal tide ray. The ray originates at the northern edge of the ridge peak at a large across-ridge change in topographic slope and terminates at the ocean surface about 30–40 km south of the ridge peak. Kinetic and potential energy density are larger on the south side of the ridge at KC, the side with larger topographic slope. Energy density is also larger on the south side of the ridge at KC in numerical model results and on the side of steeper topographic slope in analytical model results. Along the ridge, the largest observed values of mean-square shear and mean-square slope of isopycnal depth are collocated with the largest energy density in numerical model results. Mean-square shear and mean-square slope increase with decreasing bottom depth and with increasing M2 barotropic tidal forcing.

scholarly journals Oxycline oscillations induced by internal waves in deep Lake Iseo

2018 ◽  
Author(s):  
Giulia Valerio ◽  
Marco Pilotti ◽  
Maximilian Peter Lau ◽  
Michael Hupfer
Keyword(s):  
Internal Waves ◽  
Water Layer ◽  
Sediment Surface ◽  
Chemical Gradient ◽  
Deep Lakes ◽  
Deep Lake ◽  
Deep Waters ◽  
Basin Scale ◽  
First Time

Abstract. Lake Iseo is undergoing a dramatic de-oxygenation of the hypolimnion, representing an emblematic example among the deep lakes of the prealpine area that are, to a different extent, suffering from reduced deep water mixing. In the anoxic deep waters, the release and accumulation of reduced substances and phosphorus from the sediments is a major concern. Since the hydrodynamics of this lake was shown to be dominated by internal waves, in this study we investigate for the first time the role of these oscillatory motions on the vertical fluctuations of the oxycline, currently situated at a depth of around 95 m, where a permanent chemocline inhibits deep mixing by convection. Temperature and dissolved oxygen data measured at moored stations show large and periodic oscillations of the oxycline, with amplitude up to 20 m and periods ranging from 1 to 4 days. A deep dynamics characterized by larger amplitudes at lower frequencies is shown to be favoured by the excitation of second vertical modes in strongly thermally stratified periods and of first vertical modes in weakly thermally stratified periods, when the deep chemical gradient can support baroclinicity anyhow. These basin-scale internal waves cause in the water layer between 85 and 105 m depth a fluctuation of the oxygen concentration between 0 and 3 mg L−1 that, due to the bathymetry of the lake, changes the redox condition at the sediment surface. This forcing, involving about 3 % of the lake's sediment area, can have major implications for the biogeochemical processes at the sediment water interface and for the internal matter cycle.

Numerical Simulation of Wave Interaction With a Pair of Fixed Large Tandem Cylinders Subjected to Regular, Non-Breaking Waves

2021 ◽  
Author(s):  
M. Mohseni ◽  
C. Guedes Soares
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
Circular Cross Section ◽  
Wave Interaction ◽  
Breaking Waves ◽  
Wave Loading ◽  
Two Phase ◽  
Wave Regime ◽  
Wave Amplification ◽  
Vof Model

Abstract The wave interaction with cylinders placed in proximity results in significant modification of the wave field, wave-induced processes, and wave loading. The evaluation of such a complex wave regime and accurate assessment of the wave loading requires an efficient and accurate numerical model. Concerning the wave scattering types identified by Swan et al. (2015) and lateral progressive edge waves, this paper presents the application of a two-phase Computational Fluid Dynamics (CFD) model to carry out a detailed investigation of nonlinear wave field surrounding a pair of columns placed in the tandem arrangement in the direction of wave propagation and corresponding harmonics. The numerical analysis is conducted using the Unsteady Reynolds-Averaged Navier-Stokes/VOF model based on the OpenFOAM framework combined with the olaFlow toolbox for wave generation/absorption. For the simulations, the truncated cylinders are assumed vertical and surface piercing with a circular cross-section subjected to regular, non-breaking fifth-order Stokes waves propagating with moderate steepness in deep water. Primarily, the numerical model is validated with experimental data provided by ITTC (OEC)[1] for a single cylinder. Future, the given simulations are conducted for different centre-to-centre distances between the tandem large cylinders. The results show the evolution of a strong wave diffraction pattern and consequently high wave amplification harmonics around cylinders are apparent.

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