1,018 research outputs found
The GeoClaw software for depth-averaged flows with adaptive refinement
Many geophysical flow or wave propagation problems can be modeled with
two-dimensional depth-averaged equations, of which the shallow water equations
are the simplest example. We describe the GeoClaw software that has been
designed to solve problems of this nature, consisting of open source Fortran
programs together with Python tools for the user interface and flow
visualization. This software uses high-resolution shock-capturing finite volume
methods on logically rectangular grids, including latitude--longitude grids on
the sphere. Dry states are handled automatically to model inundation. The code
incorporates adaptive mesh refinement to allow the efficient solution of
large-scale geophysical problems. Examples are given illustrating its use for
modeling tsunamis, dam break problems, and storm surge. Documentation and
download information is available at www.clawpack.org/geoclawComment: 18 pages, 11 figures, Animations and source code for some examples at
http://www.clawpack.org/links/awr10 Significantly modified from original
posting to incorporate suggestions of referee
Experiments and analyses of upstream-advancing solitary waves generated by moving disturbances
In this joint theoretical, numerical and experimental study, we investigate the phenomenon of forced generation of nonlinear waves by disturbances moving steadily with a transcritical velocity through a layer of shallow water. The plane motion considered here is modelled by the generalized Boussinesq equations and the forced Korteweg-de Vries (fKdV) equation, both of which admit two types of forcing agencies in the form of an external surface pressure and a bottom topography. Numerical results are obtained using both theoretical models for the two types of forcings. These results illustrate that within a transcritical speed range, a succession of solitary waves are generated, periodically and indefinitely, to form a procession advancing upstream of the disturbance, while a train of weakly nonlinear and weakly dispersive waves develops downstream of an ever elongating stretch of a uniformly depressed water surface immediately behind the disturbance. This is a beautiful
example showing that the response of a dynamic system to steady forcing need not asymptotically tend to a steady state, but can be conspicuously periodic, after an impulsive start, when the system is being forced at resonance.
A series of laboratory experiments was conducted with a cambered bottom topography impulsively started from rest to a constant transcritical velocity U, the corresponding depth Froude number F = U/(gh[sub]0)^1/2 (g being the gravitational constant and h[sub]0 the original uniform water depth) being nearly the critical value of unity. For the two types of forcing, the generalized Boussinesq model indicates that the surface pressure can be more effective in generating the precursor solitary waves than the submerged topography of the same normalized spatial distribution. However, according to the fKdV model, these two types of forcing are entirely equivalent. Besides these and some other rather refined differences, a broad agreement is found between theory and experiment, both in respect of the amplitudes and phases of the waves generated, when the speed is nearly critical (0.9 F > 0.2, finally disappear at F ~= 0.2. In the other direction, as the Froude number is increased beyond F ~= 1.2, the precursor soliton phenomenon was found also to evanesce as no finite-amplitude solitary waves can outrun, nor can any two-dimensional waves continue to follow, the rapidly moving disturbance. In this supercritical range and for asymptotically large times, all the effects remain only
local to the disturbance. Thus, the criterion of the fascinating phenomenon of the generation of precursor solitons is ascertained
On the contribution of the horizontal sea-bed displacements into the tsunami generation process
The main reason for the generation of tsunamis is the deformation of the
bottom of the ocean caused by an underwater earthquake. Usually, only the
vertical bottom motion is taken into account while the horizontal co-seismic
displacements are neglected in the absence of landslides. In the present study
we propose a methodology based on the well-known Okada solution to reconstruct
in more details all components of the bottom coseismic displacements. Then, the
sea-bed motion is coupled with a three-dimensional weakly nonlinear water wave
solver which allows us to simulate a tsunami wave generation. We pay special
attention to the evolution of kinetic and potential energies of the resulting
wave while the contribution of the horizontal displacements into wave energy
balance is also quantified. Such contribution of horizontal displacements to
the tsunami generation has not been discussed before, and it is different from
the existing approaches. The methods proposed in this study are illustrated on
the July 17, 2006 Java tsunami and some more recent events.Comment: 30 pages; 14 figures. Accepted to Ocean Modelling. Other authors
papers can be downloaded at http://www.lama.univ-savoie.fr/~dutykh
Uncovering a Paleotsunami Triggered by Mass-Movement in an Alpine Lake
Mass movements and delta collapses are significant sources of tsunamis in
lacustrine environments, impacting human societies enormously. Palaeotsunamis
play an essential role in understanding historical events and their
consequences along with their return periods. Here, we focus on a palaeo event
that occurred during the Younger Dryas to Early Holocene climatic transition,
ca., 12,000 years ago in the Lake Aiguebelette (NW Alps, France). Based on
highresolution seismic and bathymetric surveys and sedimentological,
geochemical, and magnetic analyses, a seismically induced large mass transport
deposit with an initial volume of 767172 m3 was identified, dated and mapped.
To investigate whether this underwater mass transport produced a palaeotsunami
in the Lake Aiguebelette, this research combines sedimentary records and
numerical models. Numerical simulations of tsunamis are performed using a
viscoplastic landslide model for tsunami source generation and two-dimensional
depth-averaged nonlinear shallow water equations for tsunami wave propagation
and inundation modelling. Our simulations conclude that this sublacustrine
landslide produced a tsunami wave with a maximum amplitude of approximately 2 m
and run-up heights of up to 3.6 m. The modelled sediment thickness resulting
from this mass transport corroborates well with the event deposits mapped in
the lake. Based on our results, we suggest that this sublacustrine mass
transport generated a significant tsunami wave that has not been reported
previously to the best of our knowledge.Comment: Advances in Hydroinformatics, O. Delestre (Polytech Nice Sophia --
University C{\^o}te d'Azur, France), Nov 2023, Chatou, Franc
Tsunami And Storm Surge Modeling In Bay Of Bengal [GC220.4.B43 C442 2007 f rb].
Kemusnahan yang disebabkan oleh Andaman tsunami pada 26
Disember 2004 merupakan masalah utama komuniti di seluruh dunia. Pelbagai usaha telah diambil untuk mengurangkan impak yang disebabkan oleh tsunami yang mungkin berlaku pada masa hadapan.
Destruction due to 26 December 2004 Andaman tsunami has become a major concern to the communities around the world. Several efforts have been undertaken to minimize the potential impacts of future tsunamis
Modeling Issues in Asteroid-Generated Tsunamis
This report studies tsunamis caused by asteroids, both those that arise from atmospheric blast waves moving across the water surface from airburst asteroids, and those that arise when the asteroid reaches the water and forms a crater. We perform numerical experiments that compare simulations using depth-averaged models (shallow water and several forms of Boussinesq) with linearized Euler (acoustics plus gravity) and ALE hydrocode simulations. We find that neither of the depth-averaged models do a good job of initiating the tsunami, but in some cases can be used to propagate a solution generated by a higher-fidelity method. A list of our conclusions and recommendations for further study is given in Section 5
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