Effects of external flow on compositional and particle gravity currents

Hallworth, Mark A.; Hogg, Andrew J.; Huppert, Herbert E.

doi:10.1017/s0022112097008409

Cited by 77 publications

(106 citation statements)

References 31 publications

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“…The model is based on the work of Huppert and Simpson (1980), Dade and Huppert (1996), and Hallworth et al (1998). It is suited for describing the propagation of turbulent currents, in which inertial effects dominate over viscous forces and particle-particle interactions.…”

Section: Simplified Pdc Invasion Modelmentioning

confidence: 99%

The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy)

et al. 2017

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This study presents a new method for producing long-term hazard maps for pyroclastic density currents (PDC) originating at Campi Flegrei caldera. Such method is based on a doubly stochastic approach and is able to combine the uncertainty assessments on the spatial location of the volcanic vent, the size of the flow and the expected time of such an event. The results are obtained by using a Monte Carlo approach and adopting a simplified invasion model based on the box model integral approximation. Temporal assessments are modeled through a Cox-type process including self-excitement effects, based on the eruptive record of the last 15 kyr. Mean and percentile maps of PDC invasion probability are produced, exploring their sensitivity to some sources of uncertainty and to the effects of the dependence between PDC scales and the caldera sector where they originated. Conditional maps representative of PDC originating inside limited zones of the caldera, or of PDC with a limited range of scales are also produced. Finally, the effect of assuming different time windows for the hazard estimates is explored, also including the potential occurrence of a sequence of multiple events. Assuming that the last eruption of Monte Nuovo (A.D. 1538) marked the beginning of a new epoch of activity similar to the previous ones, results of the statistical analysis indicate a mean probability of PDC invasion above 5% in the next 50 years on almost the entire caldera (with a probability peak of ∼25% in the central part of the caldera). In contrast, probability values reduce by a factor of about 3 if the entire eruptive record is considered over the last 15 kyr, i.e., including both eruptive epochs and quiescent periods.

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Section: Simplified Pdc Invasion Modelmentioning

confidence: 99%

The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy)

et al. 2017

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“…This is beneficial for capturing the important flow features. This model has been used extensively in understanding turbidity current flow characteristics (Harris et al, 2001;Hogg, 2006), including the effects of modelling polydisperse suspensions (Harris et al, 2002;Garcia, 1994) and the effects of external flow (Hallworth et al, 1998). The model used in this paper is based upon the single layer shallow water model of Bonnecaze et al (1993).…”

Section: Modelmentioning

confidence: 99%

Application of the adjoint approach to optimise the initial conditions of a turbidity current with the AdjointTurbidity 1.0 model

Parkinson¹,

Funke²,

Piggott³

et al. 2017

Geosci. Model Dev.

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Abstract. Turbidity currents are one of the main drivers of sediment transport from the continental shelf to the deep ocean. The resulting sediment deposits can reach hundreds of kilometres into the ocean. Computer models that simulate turbidity currents and the resulting sediment deposit can help us to understand their general behaviour. However, in order to recreate real-world scenarios, the challenge is to find the turbidity current parameters that reproduce the observations of sediment deposits. This paper demonstrates a solution to the inverse sediment transportation problem: for a known sedimentary deposit, the developed model reconstructs details about the turbidity current that produced the deposit. The reconstruction is constrained here by a shallow water sediment-laden density current model, which is discretised by the finite-element method and an adaptive time-stepping scheme. The model is differentiated using the adjoint approach, and an efficient gradientbased optimisation method is applied to identify the turbidity parameters which minimise the misfit between the modelled and the observed field sediment deposits. The capabilities of this approach are demonstrated using measurements taken in the Miocene Marnoso-arenacea Formation (Italy). We find that whilst the model cannot match the deposit exactly due to limitations in the physical processes simulated, it provides valuable insights into the depositional processes and represents a significant advance in our toolset for interpreting turbidity current deposits.

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“…One of the key features of turbidity currents is the lobe-and-cleft structures located at the head of the current. There has been an intensive effort to study those structures, with many experimental investigations, 3,7,[12][13][14][15] theoretical approaches, 16,17 and more recently with numerical investigations based on Direct Numerical Simulations (DNS). [18][19][20][21][22][23][24] Experiments 3,7,12 investigating a) s.laizet@imperial.ac.uk lobe-and-cleft patterns have typically imaged the gravity current from below, allowing the growth, merging, and bifurcation of the structures to be tracked.…”

Section: Introductionmentioning

confidence: 99%

High-fidelity simulations of the lobe-and-cleft structures and the deposition map in particle-driven gravity currents

et al. 2015

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The evolution of a mono-disperse gravity current in the lock-exchange configuration is investigated by means of direct numerical simulations for various Reynolds numbers and settling velocities for the deposition. We limit our investigations to gravity currents over a flat bed in which density differences are small enough for the Boussinesq approximation to be valid. The concentration of particles is described in an Eulerian fashion by using a transport equation combined with the incompressible Navier-Stokes equations. The most interesting results can be summarized as follows: (i) the settling velocity is affecting the streamwise vortices at the head of the current with a substantial reduction of their size when the settling velocity is increased; (ii) when the Reynolds number is increased the lobe-and-cleft structures are merging more frequently and earlier in time, suggesting a strong Reynolds number dependence for the spatio-temporal evolution of the head of the current; (iii) the temporal imprint of the lobe-and-cleft structures can be recovered from the deposition map, suggesting that the deposition pattern is defined purely and exclusively by the structures at the front of the current.

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Effects of external flow on compositional and particle gravity currents

Cited by 77 publications

References 31 publications

The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy)

The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy)

Application of the adjoint approach to optimise the initial conditions of a turbidity current with the AdjointTurbidity 1.0 model

High-fidelity simulations of the lobe-and-cleft structures and the deposition map in particle-driven gravity currents

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