scholarly journals Stratification effects on shoaling internal solitary waves

2021 ◽  
Vol 933 ◽  
Author(s):  
Samuel G. Hartharn-Evans ◽  
Magda Carr ◽  
Marek Stastna ◽  
Peter A. Davies
Keyword(s):  
Density Gradient ◽  
Solitary Waves ◽  
Lower Layer ◽  
Three Dimensional ◽  
Internal Solitary Waves ◽  
Wave Steepness ◽  
Topographic Slope ◽  
Upper Boundary ◽  
Good Agreement ◽  
Three Dimensional Simulations

This combined numerical/laboratory study investigates the effect of stratification form on the shoaling characteristics of internal solitary waves propagating over a smooth, linear topographic slope. Three stratification types are investigated, namely (i) thin tanh (homogeneous upper and lower layers separated by a thin pycnocline), (ii) surface stratification (linearly stratified layer overlaying a homogeneous lower layer) and (iii) broad tanh (continuous density gradient throughout the water column). It is found that the form of stratification affects the breaking type associated with the shoaling wave. In the thin tanh stratification, good agreement is seen with past studies. Waves over the shallowest slopes undergo fission. Over steeper slopes, the breaking type changes from surging, through collapsing to plunging with increasing wave steepness $A_w/L_w$ for a given topographic slope, where $A_w$ and $L_w$ are incident wave amplitude and wavelength, respectively. In the surface stratification regime, the breaking classification differs from the thin tanh stratification. Plunging dynamics is inhibited by the density gradient throughout the upper layer, instead collapsing-type breakers form for the equivalent location in parameter space in the thin tanh stratification. In the broad tanh profile regime, plunging dynamics is likewise inhibited and the near-bottom density gradient prevents the collapsing dynamics. Instead, all waves either fission or form surging breakers. As wave steepness in the broad tanh stratification increases, the bolus formed by surging exhibits evidence of Kelvin–Helmholtz instabilities on its upper boundary. In both two- and three-dimensional simulations, billow size grows with increasing wave steepness, dynamics not previously observed in the literature.

scholarly journals Stratification effects on shoaling Internal Solitary Waves

2021 ◽  
Author(s):  
Sam Hartharn-Evans ◽  
Magda Carr ◽  
Marek Stastna ◽  
Peter Davies
Keyword(s):  
Density Gradient ◽  
Solitary Waves ◽  
Numerical Experiments ◽  
Lower Layer ◽  
Internal Solitary Waves ◽  
Topographic Slope ◽  
Numerical Studies ◽  
The World ◽  
Upper Boundary ◽  
Mixing And Transport

<p>Shoaling is a key mechanism by which Internal Solitary Waves (ISWs) dissipate energy, induce mixing, and transport sediment. Past studies of shoaling ISWs in a three-layer stratification (with homogeneous upper and lower layers separated by a thin pycnocline layer) have identified a classification system where waves over the shallowest slopes undergo fission, whilst over steeper slopes, the breaking type changes from surging, through collapsing to plunging as a function of increasing internal Irribaren number (Ir) defined with the topographic slope, s, and the incident wave’s amplitude and wavelength, A<sub>w</sub> and L<sub>w </sub>respectively, as <img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.9fb46536f70067154311161/sdaolpUECMynit/12UGE&app=m&a=0&c=d84eaf790c6586a46ed8fca09040fcd7&ct=x&pn=gnp.elif&d=1" alt="" width="117" height="24">. Here, a combined numerical and laboratory study extends this prior work into new stratifications, representing the diversity of ocean structures across the world. Numerical results were able to successfully reproduce past studies in the three-layer stratification, and those in the two-layer stratification in the laboratory. Where a linear stratified layer overlays a homogeneous lower layer (two-layer stratification), it is found that plunging dynamics are inhibited by the density gradient throughout the upper layer, instead forming collapsing-type breakers. In numerical experiments, where the density gradient is continuous throughout the full water column (linear stratification), not only are the plunging dynamics inhibited, but the density gradient at the bottom boundary also prevents the formation of collapsing dynamics, instead all waves in this stratification either fission, or form surging breakers. Where the wave steepness is particularly high in the linear stratification, the upslope bolus formed by surging was unstable, and Kelvin-Helmholtz instabilities were observed on the upper boundary of the bolus, dynamics not previously observed in the literature. These results indicate the importance of using representative stratifications in laboratory and numerical studies of ISW behaviours.</p>

Vortex rings impinging on walls: axisymmetric and three-dimensional simulations

1993 ◽  
Vol 256 ◽  
pp. 615-646 ◽  
Author(s):  
Paolo Orlandi ◽  
Roberto Verzicco
Keyword(s):  
Numerical Simulations ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Vortex Rings ◽  
Compression Phase ◽  
Vortex Pairing ◽  
The Impact ◽  
Good Agreement ◽  
Three Dimensional Simulations

Accurate numerical simulations of vortex rings impinging on flat boundaries revealed the same features observed in experiments. The results for the impact with a free-slip wall compared very well with previous numerical simulations that used spectral methods, and were also in qualitative agreement with experiments. The present simulation is mainly devoted to studying the more realistic case of rings interacting with a no-slip wall, experimentally studied by Walker et al. (1987). All the Reynolds numbers studied showed a very good agreement between experiments and simulations, and, at Rev > 1000 the ejection of a new ring from the wall was seen. Axisymmetric simulations demonstrated that vortex pairing is the physical mechanism producing the ejection of the new ring. Three-dimensional simulations were also performed to investigate the effects of azimuthal instabilities. These simulations have confirmed that high-wavenumber instabilities originate in the compression phase of the secondary ring within the primary one. The large instability of the secondary ring has been explained by analysis of the rate-of-strain tensor and vorticity alignment. The differences between passive scalars and the vorticity field have been also investigated.

Numerical Investigation on Unstable Oscillations of Two Circular Cylinders in Tandem Arrangement

2003 ◽  
Author(s):  
Yoshiaki Itoh ◽  
Ryutaro Himeno
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Numerical Investigation ◽  
Difference Method ◽  
Three Dimensional ◽  
Circular Cylinders ◽  
Damping Force ◽  
Negative Damping ◽  
Good Agreement ◽  
Three Dimensional Simulations

Three-dimensional simulations of incompressible and viscous flow around tandem circular cylinders at Re = 20000 in unstable oscillations can be carried out by means of finite difference method without any turbulence model. The numerical response behaviors are in good agreement with the previous experimental ones. The mechanism of negative damping force in vortex-induced oscillations and wake-galloping is investigated.

Three dimensional simulation on the generation and propagation of internal tides and solitary waves northeast of Taiwan Island

2021 ◽  
Author(s):  
Wenjia Min ◽  
Zhenhua Xu ◽  
Qun Li ◽  
Peiwen Zhang ◽  
Baoshu Yin
Keyword(s):  
Continental Slope ◽  
Solitary Waves ◽  
Okinawa Trough ◽  
Satellite Image ◽  
Three Dimensional ◽  
Internal Tides ◽  
Internal Solitary Waves ◽  
Strong Mixing ◽  
Dimensional Simulation ◽  
Shelf Region

<p>The slope area northeast of Taiwan was known as a hotspot for internal tides and internal solitary waves (ISWs), while their specific sources and generation mechanism of ISWs remain unclear. We investigate the generation and evolution processes of internal tides and ISWs with realistic configuration based on the high resolution non-hydrostatic numerical simulations. The ISWs northeastern Taiwan show a complex pattern according to the satellite image and our numerical results. ISWs propagate to various direction, and both shoreward and seaward propagating ISWs are generated on the continental slope. The ISWs observed on the continental slope-shelf region northeastern Taiwan can be generated by two ways. One is the local tide-topography interaction, and the other is the disintegration of remote internal tides generated over the I-Lan Ridge. The generated internal tides propagate northward to the Okinawa Trough, and can reach the continental slope-shelf region. During the propagation of the internal tides, the internal tides start to steepen and internal solitary waves are formed about 80 km north of I-Lan Ridge. The amplitude of the generated internal solitary waves is about 30 m. Furthermore, the Kuroshio is important to modulate the propagation and evolution of internal tides and ISWs, especially to the complexity of the ISW spatial pattern. We revealed most of the generated internal wave energy is dissipated locally over the double-canyon region, and strong mixing occur over the canyons.</p>

Experimental Study of Wave Loading by Internal Solitary Waves on a Semi-Submersible Platform

2019 ◽  
Author(s):  
Jingjing Zhang ◽  
Ke Chen ◽  
Yunxiang You ◽  
Xinshu Zhang
Keyword(s):  
Solitary Waves ◽  
Lower Layer ◽  
Internal Solitary Waves ◽  
Wave Forces ◽  
Wave Loads ◽  
Wave Loading ◽  
Layer Depth ◽  
Fluid System ◽  
Layer Thickness Ratio ◽  
Three Degree Of Freedom

Abstract The experimental measurements presented here describe the major features of the loads exerted by internal solitary waves (ISWs) on columns and caissons of a semi-submersible platform in a two-layer fluid system. Particular attention is paid on the forces acted on the platform under different layer thickness ratio. By use of the dynamometer for forces of three degree of freedom (DOF), the wave forces exerted by the ISWs on the columns and caissons of the model are measured quantificationally, so the variations of forces with ISW’s amplitude and upper layer depth are derived. Comparisons are made between the experimental results and calculations based on the modified Morison equation and pressure integral method. The calculated results are well consistent with the measurements, so the method is capable of providing satisfactory predictions on the forces. Besides, the results show that the wave height has a considerable influence on the wave loads produced by the ISWs, and the forces varies with the different locations of the interface between the upper and lower layer.

scholarly journals Computational Modeling of Protective Clothing

2003 ◽  
Vol os-12 (3) ◽  
pp. 1558925003os-12
Author(s):  
James J. Barry ◽  
Principal Engineer ◽  
Roger W. Hill
Keyword(s):  
Emergency Response ◽  
Protective Clothing ◽  
Three Dimensional ◽  
Convective Transport ◽  
Variable Properties ◽  
Computational Fluid Dynamics Cfd ◽  
Garment Design ◽  
Protective Garment ◽  
Good Agreement ◽  
Three Dimensional Simulations

Models based on computational fluid dynamics (CFD) have been developed to predict the performance of chemical and steam/fire protective clothing. The software computes the diffusive and convective transport of heat and gases/vapors; capillary transport of liquids; vapor and liquid sorption phenomena and phase change; and the variable properties of the various clothing layers. It can also model the effects of sweating and humidity transport to help assess the thermal stress imposed on the wearer of the clothing. Specialized geometry/grid representations of clothed humans have been created for performing two- and three-dimensional simulations. Comparisons with experimental data show good agreement in predicting the effects of fiber swell due to transients in humidity, and the models have been used to predict the sensitivity of clothing performance to material properties such as permeability under varying environmental conditions. Applications of the models include analysis of chemical protective garment design for military and emergency response personnel, comparisons of thermally protective materials for steam or fire protection, and evaluation of clothing test data.

scholarly journals Estimate of energy loss from internal solitary waves breaking on slopes

2021 ◽  
Author(s):  
Kateryna Terletska ◽  
Vladimir Maderich ◽  
Tatiana Talipova
Keyword(s):  
Energy Loss ◽  
Solitary Waves ◽  
Wave Breaking ◽  
Numerical Experiments ◽  
Wave Amplitude ◽  
Three Dimensional ◽  
Bottom Layer ◽  
Internal Solitary Waves ◽  
Weakly Nonlinear ◽  
Shelf Slope

Abstract. Internal solitary waves (ISW) emerge in the ocean and seas in different forms and break on the shelf zones in a variety of ways. Their breaking on slopes can produce intensive mixing that produces such process as biological productivity and sediment transport. Mechanisms of ISW of depression interaction with the slopes related to breaking and changing polarity as they shoal. We assume that parameters that described the process of interaction of ISW in a two-layer fluid with the idealised shelf-slope are: the non-dimensional wave amplitude α (wave amplitude normalized on the upper layer thickness), the ratio of the height of the bottom layer on the shelf to the incident wave amplitude β and angle γ. Based on three-dimensional αβγ classification diagram with four types of interaction with the slopes it was discussed: (1) ISW propagates over slope without changing polarity and wave breaking; (2) ISW changes polarity over slope without breaking; (3) ISW breaks over slope without changing polarity; (4) ISW both breaks and change polarity over the slope. Relations between the parameters α,β,γ for each regime were obtained using the empirical condition for wave breaking and weakly nonlinear theory for the criterion of changing the polarity of the wave. In the present paper the α,β,γ diagram was validated for idealised real scale topography configurations. Results of the numerical experiments that were carried out in the present paper and results of field and laboratory experiments from other papers are in good agreement with proposed classification and estimations. Based on 85 numerical experiments ISWs energy loss during interaction with slope topography with 0.5° < γ < 90° was estimated. Hot spots zones of high levels of energy loss were shown for idealized configuration that mimics continental shelf at Lufeng Region SCS.

scholarly journals Source site of internal solitary waves in the northern South China of westward shoaling thermocline

2017 ◽  
Author(s):  
Gang Wang ◽  
Yuanling Zhang ◽  
Chang Zhao ◽  
Dejun Dai ◽  
Min Zhang ◽  
...  
Keyword(s):  
Solitary Waves ◽  
South China ◽  
General Circulation ◽  
Northern South China Sea ◽  
Three Dimensional ◽  
Circulation Model ◽  
Internal Solitary Waves ◽  
Generation Process ◽  
The West ◽  
Source Site

Abstract. This study use a three dimensional general circulation model, MITgcm with non-hydrostatic option, to study the source site of internal solitary waves (ISWs) observed in the northern South China Sea. Simulation reveals that besides Luzon Strait, ISWs in the northern SCS are also generated around Dongsha Islands and near the continental shelf break. It is one of the reasons that there are more wave package to the west of 120° E in SAR images, and even more to the west of 118° E. The generation process and propagation feature of ISWs in these source sites are described.

scholarly journals 3D DEM simulations of monotonic interface behaviour between cohesionless sand and rigid wall of different roughness

2020 ◽  
Author(s):  
A. Grabowski ◽  
M. Nitka ◽  
J. Tejchman
Keyword(s):  
Normal Stress ◽  
Three Dimensional ◽  
Rigid Wall ◽  
Interface Roughness ◽  
Wall Friction ◽  
Dem Simulations ◽  
New Perspective ◽  
Interface Behaviour ◽  
Good Agreement ◽  
Three Dimensional Simulations

Abstract The paper deals with three-dimensional simulations of a monotonic quasi-static interface behaviour between cohesionless sand and a rigid wall of different roughness during wall friction tests in a parallelly guided direct shear test under constant normal stress. Numerical modelling was carried out by the discrete element method (DEM) using spheres with contact moments to approximately capture a non-uniform particle shape. The varying wall surface topography was simulated by a regular mesh of triangular grooves (asperities) along the wall with a different height, distance and inclination. The calculations were carried out with different initial void ratios of sand and vertical normal stress. The focus was to quantify the effect of wall roughness on the evolution of mobilized wall friction and shear localization, also to specify the ratios between slip and rotation and between shear stress/force and couple stress/moment in the sand at the wall. DEM simulations were generally in good agreement with reported experimental results for similar interface roughness. The findings presented in this paper offer a new perspective on the understanding of the wall friction phenomenon in granular bodies.

scholarly journals Mix experiments using a two-dimensional convergent shock-tube

2003 ◽  
Vol 21 (3) ◽  
pp. 403-409 ◽  
Author(s):  
D.A. HOLDER ◽  
A.V. SMITH ◽  
C.J. BARTON ◽  
D.L. YOUNGS
Keyword(s):  
Shock Tube ◽  
Turbulent Mixing ◽  
Three Dimensional ◽  
Gas Mixture ◽  
Mixing Process ◽  
Dense Gas ◽  
Atomic Weapons ◽  
Air Void ◽  
Good Agreement ◽  
Three Dimensional Simulations

This article reports the first Richtmyer–Meshkov instability experiments using an improved version of the Atomic Weapons Establishment convergent shock tube. These investigate the shock-induced turbulent mixing across the interfaces of an air/dense gas/air region. Multipoint ignition of a detonatable gas mixture produces a cylindrically convergent shock that travels into a test cell containing the dense gas region. The mixing process is imaged with shadowgraphy. Sample results are presented from an unperturbed experiment and one with a notch perturbation imposed on one of the dense gas interfaces. The unperturbed experiment shows the mixing across the dense gas boundaries and the motion of the bulk dense gas region. Imposition of the notch perturbation produces a mushroom-shaped air void penetrating the dense gas region. Three-dimensional simulations performed using the AWE TURMOIL3D code are presented and compared with the sample experimental results. A very good agreement is demonstrated. Conducting these first turbulent mixing experiments has highlighted a number of areas for future development of the convergent shock-tube facility; these are also presented.

Sign in / Sign up

Export Citation Format

Share Document