Emneord:
Mekanikk,
Fluidmekanikk
Publikasjoner

Verschaeve, Joris C. G.; Pedersen, Geir Kleivstul & Tropea, Cameron (2018). Nonmodal stability analysis of the boundary layer under solitary waves. Journal of Fluid Mechanics.
ISSN 00221120.
836, s 740 772 . doi:
10.1017/jfm.2017.825
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BirknesBerg, Jørn & Pedersen, Geir Kleivstul (2017). The “Chain of Markers” code applied to large scale problems; solitary waves, sloshing and a plunging wave. Research report in mechanics.
ISSN 08019940.
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Jeschke, Anja; Pedersen, Geir Kleivstul; Vater, Stefan & Behrens, Jörn (2017). Depthaveraged nonhydrostatic extension for shallow water equations with quadratic vertical pressure profile: equivalence to Boussinesqtype equations. International Journal for Numerical Methods in Fluids.
ISSN 02712091.
84(10), s 569 583 . doi:
10.1002/fld.4361

Kim, Jihwan; Pedersen, Geir Kleivstul; Løvholt, Finn & LeVeque, Randall J. (2017). A Boussinesq type extension of the GeoClaw model  a study of wave breaking phenomena applying dispersive long wave models. Coastal Engineering.
ISSN 03783839.
122, s 75 86 . doi:
10.1016/j.coastaleng.2017.01.005
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The nonlinear shallow water model is widely used in the study of tsunami propagation, but an increasing number of studies are dedicated to the dispersion dynamics of tsunamis. If the wave dispersion becomes important, Boussinesqtype models are often used. In this work, a general purpose Boussinesq solver, BoussClaw, is introduced for modeling nonlinear dispersive tsunami propagation, taking into account inundation. The BoussClaw model is an extension of the GeoClaw tsunami model. It employs a hybrid of finite volume and finite difference methods to solve Boussinesq equations from the literature, which are based on the depthaveraged velocity and include enhanced dispersion properties. On the other hand, in the selected formulation only some nonlinearity is retained in the dispersion term. In order to validate BoussClaw, numerical results are compared to analytic solutions, solutions obtained by preexisting models, and laboratory experiments. Even though the equations of BoussClaw are not fully nonlinear they perform far better than standard Boussinesq equations with only linear dispersion terms. Furthermore, the wave steepening and breaking are carefully scrutinized, and we demonstrate that the point of wave breaking may be wrongly identified in many of the commonly used Boussinesq models.

Smith, Lisa; Jensen, Atle & Pedersen, Geir Kleivstul (2017). Investigation of breaking and nonbreaking solitary waves and measurements of swash zone dynamics on a 5° beach. Coastal Engineering.
ISSN 03783839.
120, s 38 46 . doi:
10.1016/j.coastaleng.2016.11.004
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Løvholt, Finn; Pedersen, Geir Kleivstul & Harbitz, Carl Bonnevie (2016). TsunamiGenesis Due to Retrogressive Landslides on an Inclined Seabed, In Geoffrey Lamarche; Joshu Mountjoy; Suzanne Bull & Tom Hubble (ed.),
Submarine Mass Movements and their Consequences: 7th International Symposium.
Springer Publishing Company.
ISBN 9783319209791.
57.
s 569
 578
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Clayrich landslides commonly involve retrogressive mass and momentum release mechanisms. Motivated by the retrogressive behaviour of major landslides offshore Norway, previous studies have demonstrated substantial effects of the release rate on the generation of the tsunami. However, the few existing models are limited to overly idealized conditions. In the present study, we explore further the wave generation due to a continuous retrogressive landslide model, quantifying the effects of the wave model, landslide configuration, and the continental slope. In the present examples, we find that the landslides involve large accelerations that may be crucial for tsunamigenesis. Tsunami footprints due to individual short blocks comprising the landslide are smeared out by dispersion. Keeping landslide material properties constant, we investigate mobilised landslide mass and maximum tsunami crest elevations for three different slopes: 1°, 1.5°, and 2° respectively. In the present examples, the smaller volume landslides are stronger tsunami generators than the larger ones because they are situated in shallower water, thereby clearly demonstrating the importance of the water depth on the tsunami generation.

Pedersen, Geir Kleivstul (2016). Fully nonlinear Boussinesq equations for long wave propagation and runup in sloping channels with parabolic cross sections. Natural Hazards.
ISSN 0921030X.
84, s 599 619 . doi:
10.1007/s1106901624480
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A general framework for derivation of long wave equations in narrow channels, and their transformation to Lagrangian coordinates is briefly established. Then, fully nonlinear Boussinesq equations are derived for channels of parabolic cross sections. The simplified version with normal nonlinearity is compared with corresponding models from the literature, and propagation properties are discussed. A Lagrangian runup model is adapted to the fully nonlinear set. This model is tested by means of controlled residues and by a wellcontrolled comparison to exact analytic solutions from the literature. Then, runup of solitary waves in simple geometries is simulated and compared to a semianalytic solution that is derived for propagation and runup in a composite channel. The dispersive model retains the higher runup height in a parabolic channels, as reported in the recent literature for NLSW solutions, as compared to a rectangular channel.

Løvholt, Finn; Glimsdal, Sylfest; Lynett, P. & Pedersen, Geir Kleivstul (2015). Simulating tsunami propagation in fjords with longwave models. Natural hazards and earth system sciences.
ISSN 15618633.
15(3), s 657 669 . doi:
10.5194/nhess156572015
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Tsunamis induced by rock slides constitute a severe hazard towards coastal fjord communities. Fjords are narrow and rugged with steep slopes, and modeling the shortfrequency and highamplitude tsunamis in this environment is demanding. In the present paper, our ability (and the lack thereof) to simulate tsunami propagation and runup in fjords for typical wave characteristics of rockslideinduced waves is demonstrated. The starting point is a 1 : 500 scale model of the topography and bathymetry of the southern part of Storfjorden fjord system in western Norway. Using measured wave data from the scale model as input to numerical simulations, we find that the leading wave is moderately influenced by nonlinearity and dispersion. For the trailing waves, dispersion and dissipation from the alongshore inundation on the traveling wave become more important. The tsunami inundation was simulated at the two locations of Hellesylt and Geiranger, providing a good match with the measurements in the former location. In Geiranger, the most demanding case of the two, discrepancies are larger. The discrepancies may be explained by a combinations of factors, such as the accumulated errors in the wave propagation along large stretches of the fjord, the coarse grid resolution needed to ensure model stability, and scale effects in the laboratory experiments.

Løvholt, Finn; Pedersen, Geir Kleivstul; Harbitz, Carl Bonnevie; Glimsdal, Sylfest & Kim, Jihwan (2015). On the characteristics of landslide tsunamis. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.
ISSN 1364503X.
373(2053) . doi:
10.1098/rsta.2014.0376
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This review presents modelling techniques and processes that govern landslide tsunami generation, with emphasis on tsunamis induced by fully submerged landslides. The analysis focuses on a set of representative examples in simplified geometries demonstrating the main kinematic landslide parameters influencing initial tsunami amplitudes and wavelengths. Scaling relations from laboratory experiments for subaerial landslide tsunamis are also briefly reviewed. It is found that the landslide acceleration determines the initial tsunami elevation for translational landslides, while the landslide velocity is more important for impulsive events such as rapid slumps and subaerial landslides. Retrogressive effects stretch the tsunami, and in certain cases produce enlarged amplitudes due to positive interference. In an example involving a deformable landslide, it is found that the landslide deformation has only a weak influence on tsunamigenesis. However, more research is needed to determine how landslide flow processes that involve strong deformation and long runout determine tsunami generation.
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Publisert 13. nov. 2010 14:05
 Sist endret 6. nov. 2018 11:53