Geir Kleivstul Pedersen

• Grue, John; Pedersen, Geir Kleivstul & Sætra, Øyvind (2022). Free Wave Effects in Meteotsunamis. Journal of Geophysical Research (JGR): Oceans. ISSN 2169-9275. 127(2). doi: 10.1029/2021JC017669. Fulltekst i vitenarkiv
• Pedersen, Geir Kleivstul (2021). Asymptotic, Convergent, and Exact Truncating Series Solutions of the Linear Shallow Water Equations for Channels with Power Law Geometry. SIAM Journal on Applied Mathematics. ISSN 0036-1399. 81(2), s. 285–303. doi: 10.1137/19M1305860. Fulltekst i vitenarkiv
• Zengaffinen, Thomas; Løvholt, Finn; Pedersen, Geir Kleivstul & Muhari, Abdul (2020). Modelling 2018 Anak Krakatoa Flank Collapse and Tsunami: Effect of Landslide Failure Mechanism and Dynamics on Tsunami Generation. Pure and Applied Geophysics (PAGEOPH). ISSN 0033-4553. 177, s. 2493–2516. doi: 10.1007/s00024-020-02489-x. Fulltekst i vitenarkiv Vis sammendrag

  The 2018 Anak Krakatoa volcano flank collapse generated a tsunami that impacted the Sunda Strait coastlines. In the absence of a tsunami early warning system, it caused several hundred fatalities. There are ongoing discussions to understand how the failure mechanism of this event affected landslide dynamics and tsunami generation. In this paper, the sensitivity to different failure scenarios on the tsunami generation is investigated through numerical modelling. To this end, the rate of mass release, the landslide volume, the material yield strength, and orientation of the landslide failure plane are varied to shed light on the failure mechanism, landslide evolution, and tsunami generation. We model the landslide dynamics using the depth-averaged viscoplastic flow model BingClaw, coupled with depth-averaged long wave and shallow water type models to simulated tsunami propagation. We are able to match fairly well the observed tsunami surface elevation amplitudes and inundation heights in selected area with the numerical simulations. However, as observed by other authors, discrepancies in simulated and observed arrival times for some of the offshore gauges are found, which raises questions related to the accuracy of the available bathymetry. For this purpose, further sensitivity studies changing the bathymetric depth near the source area are carried out. With this alteration we are also able to match better the arrival times of the waves.

• Zengaffinen, Thomas; Løvholt, Finn; Pedersen, Geir Kleivstul & Harbitz, Carl Bonnevie (2020). Effects of rotational submarine slump dynamics on tsunami genesis: new insight from idealized models and the 1929 Grand Banks event. Geological Society Special Publication. ISSN 0305-8719. doi: 10.1144/SP500-2019-201. Fulltekst i vitenarkiv Vis sammendrag

  Sediment slumps are known to have generated important tsunamis such as the 1998 Papua New Guinea (PNG) and the 1929 Grand Banks events. Tsunami modellers commonly use solid blocks with short run-out distances to simulate these slumps. While such methods have the obvious advantage of being simple to use, they offer little or no insight into physical processes that drive the events. The importance of rotational slump motion to tsunamigenic potential is demonstrated in this study by employing a viscoplastic landslide model with Herschel-Bulkley rheology. A large number of simulations for different material properties and landslide configurations are carried out to link the slump's deformation, rheology, its translational and rotational kinematics, to its tsunami-genesis. The yield strength of the slump is shown to be the primary material property that determines the tsunami-genesis. This viscoplastic model is further employed to simulate the 1929 Grand Banks tsunami using updated geological source information. The results of this case study suggest that the viscoplastic model can be used to simulate complex slump induced tsunami. The simulations of the 1929 Grand Banks event also indicate that a pure slump mechanism is more tsunamigenic than a corresponding translational landslide mechanism.

• Verschaeve, Joris C. G.; Pedersen, Geir Kleivstul & Tropea, Cameron (2018). Non-modal stability analysis of the boundary layer under solitary waves. Journal of Fluid Mechanics. ISSN 0022-1120. 836, s. 740–772. doi: 10.1017/jfm.2017.825. Fulltekst i vitenarkiv
• Jeschke, Anja; Pedersen, Geir Kleivstul; Vater, Stefan & Behrens, Jörn (2017). Depth-averaged non-hydrostatic extension for shallow water equations with quadratic vertical pressure profile: equivalence to Boussinesq-type equations. International Journal for Numerical Methods in Fluids. ISSN 0271-2091. 84(10), s. 569–583. doi: 10.1002/fld.4361.
• Birknes-Berg, 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 0801-9940. Fulltekst i vitenarkiv
• 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 0378-3839. 122, s. 75–86. doi: 10.1016/j.coastaleng.2017.01.005. Fulltekst i vitenarkiv Vis sammendrag

  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, Boussinesq-type models are often used. In this work, a general purpose Boussinesq solver, BoussClaw, is introduced for modeling non-linear 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 depth-averaged velocity and include enhanced dispersion properties. On the other hand, in the selected formulation only some non-linearity is retained in the dispersion term. In order to validate BoussClaw, numerical results are compared to analytic solutions, solutions obtained by pre-existing 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 non-breaking solitary waves and measurements of swash zone dynamics on a 5° beach. Coastal Engineering. ISSN 0378-3839. 120, s. 38–46. doi: 10.1016/j.coastaleng.2016.11.004. Fulltekst i vitenarkiv
• Pedersen, Geir Kleivstul (2016). Fully nonlinear Boussinesq equations for long wave propagation and run-up in sloping channels with parabolic cross sections. Natural Hazards. ISSN 0921-030X. 84, s. 599–619. doi: 10.1007/s11069-016-2448-0. Vis sammendrag

  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 run-up model is adapted to the fully nonlinear set. This model is tested by means of controlled residues and by a well-controlled comparison to exact analytic solutions from the literature. Then, runup of solitary waves in simple geometries is simulated and compared to a semi-analytic solution that is derived for propagation and run-up in a composite channel. The dispersive model retains the higher run-up height in a parabolic channels, as reported in the recent literature for NLSW solutions, as compared to a rectangular channel.

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