scholarly journals WAVE GENERATION DUE TO DEBRIS FLOW INTO A SMALL AREA OF WATER

2020 ◽  
pp. 19
Author(s):  
Tetsuya Kakinoki ◽  
Gozo Tsujimoto ◽  
Tokuzo Hosoyamada ◽  
Daiki Sakai ◽  
Kohji Uno
Keyword(s):  
Debris Flow ◽  
Shallow Water Equations ◽  
Small Area ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Heavy Rain ◽  
Wave Generation ◽  
Hydraulic Characteristics ◽  
Coastal Structures ◽  
Slope Collapse

It is known that the tsunami is generated by the debris flow due to slope collapse into the sea. The huge waves may cause damage to coastal structures and residents. Because of heavy rain in northern parts of Kyushu Island, Japan, in July 2017, many reservoirs were damaged and were destroyed. It has been reported that the huge waves may have been caused by debris flow due to the heavy rain. Many laboratory experiments and numerical simulations of the landslide-generated tsunami into the sea have been carried out to clarify the process of wave generation. However, there are a few studies of wave generation by debris flow into a small area of water such as a reservoir. In this study, model experiments of debris flow were conducted in a two-dimensional flume and numerical models based on the depth-averaged shallow water equations have been per-formed in order to clarify the hydraulic characteristics of the waves.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/r6r72KtkvL4

scholarly journals FLOW CHARACTERISTICS IN SWASH OF TRANSIENT LONG WAVES

2018 ◽  
pp. 50
Author(s):  
Nimish Pujara ◽  
Philip L.-F. Liu
Keyword(s):  
Shallow Water Equations ◽  
Numerical Models ◽  
Flow Characteristics ◽  
Coastal Flooding ◽  
Coastal Structures ◽  
Transient Wave ◽  
Fluid Forces ◽  
Averaged Equations ◽  
Fundamental Understanding ◽  
Wave Forms

The flow of water on a beach is of fundamental importance in coastal engineering. It controls the sediment transport and hence beach morphology. It also affects coastal structures through forces imparted on them and coastal flooding when beach overtopping occurs. The most common approach to numerically model this flow is to use depth-averaged equations (also known as shallow water equations). However, there is a lack of fundamental understanding of the flow produced by different transient wave forms. A better understanding would lead to better validation of numerical models. It would also allow engineers to more easily evaluate fluid forces on coastal structures and the risks of beach overtopping without the need to carry out expensive numerical simulations.

scholarly journals SUBMARINE MASS FAILURE: WAVE GENERATION BY GRANULAR SLIDES

2018 ◽  
pp. 47
Author(s):  
Frederic M. Evers ◽  
Helge Fuchs ◽  
David Vetsch ◽  
Robert M. Boes
Keyword(s):  
Laboratory Experiments ◽  
Numerical Models ◽  
Experimental Studies ◽  
Wave Generation ◽  
Data Set ◽  
Ongoing Research ◽  
Tsunami Waves ◽  
Potential Source ◽  
Submarine Mass Failure ◽  
Insight Into

Submarine mass failures (SMF) are a potential source of hazardous tsunamis. While the link between seismic events and the magnitude of tsunami waves has been extensively studied and corresponding approaches are included in numerical tsunami warning models, the basic implementation of SMF generated waves is subject to ongoing research. In this context, laboratory experiments are essential for the validation of numerical schemes. Most experimental studies apply rigid slide models whereas only few include granular slides (e.g. Watts 1997, Ataie-Ashtiani & Najafi-Jilani 2008, Grilli et al. 2017). The objective of this study is to gain a better insight into the hydraulic processes related to wave generation by submarine granular slides based on experiments as well as establishing a comprehensive data set for the validation of numerical models.

scholarly journals Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 14
Author(s):  
Gianluca Zitti ◽  
Nico Novelli ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Laboratory Experiments ◽  
Numerical Models ◽  
Offshore Structures ◽  
Fish Farm ◽  
Maximum Displacement ◽  
Drag Forces ◽  
Real Size ◽  
Lift And Drag ◽  
Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

Numerical Investigation of Wave Period Influence on Long Wave Run-Up on Slope With Rigid Vegetation

2016 ◽  
Author(s):  
Jun Tang ◽  
Yongming Shen
Keyword(s):  
Shallow Water Equations ◽  
Water Wave ◽  
Wave Period ◽  
Coastal Vegetation ◽  
Coastal Structures ◽  
Rigid Vegetation ◽  
Comparison With Experiment ◽  
Long Wave ◽  
Nonlinear Shallow Water Equations ◽  
Run Up

Coastal vegetation can not only provide shade to coastal structures but also reduce wave run-up. Study of long water wave climb on vegetation beach is fundamental to understanding that how wave run-up may be reduced by planted vegetation along coastline. The present study investigates wave period influence on long wave run-up on a partially-vegetated plane slope via numerical simulation. The numerical model is based on an implementation of Morison’s formulation for rigid structures induced inertia and drag stresses in the nonlinear shallow water equations. The numerical scheme is validated by comparison with experiment results. The model is then applied to investigate long wave with diverse periods propagating and run-up on a partially-vegetated 1:20 plane slope, and the sensitivity of run-up to wave period is investigated based on the numerical results.

Deposition Prediction of Debris Flow Alluvial Fan Based on Experimental Study

2012 ◽  
Vol 518-523 ◽  
pp. 4819-4822
Author(s):  
Jin Feng Liu ◽  
Shun Yang ◽  
Guo Qiang Ou
Keyword(s):  
Experimental Study ◽  
Debris Flow ◽  
Statistical Method ◽  
Laboratory Experiments ◽  
Empirical Models ◽  
Alluvial Fan ◽  
Disaster Prevention ◽  
Average Accuracy ◽  
Hazardous Area ◽  
Debris Flow Disaster

The deposition prediction of debris flow hazardous area is very important for organizing and implementing debris flow disaster prevention and reduction. This paper selected the data base from laboratory experiments and applied the multiple regression statistical method to establish a series of empirical calculation models for delimiting the debris flow hazardous areas on the alluvial fan. The empirical models for predicting the maximum deposition length (Lc), the maximum deposition width (Bmax) and the maximum deposition thichness (Z0) under the condition of different debris flow volumes (V), densities (rm) and slopes of accumulation area (θd) were establised. And the verification results indicated that the established models can predict the debris flow hazards area with the average accuracy of 86%.

scholarly journals Propagation Characteristics of Debris Flows Considering Entrainment Effect

2018 ◽  
Vol 7 (3.34) ◽  
pp. 122
Author(s):  
Seokil Jeong ◽  
Junseon Lee ◽  
Chang Geun Song ◽  
Seung Oh Lee
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Behavior ◽  
Prediction Method ◽  
Heavy Rain ◽  
Accurate Analysis ◽  
Propagation Length ◽  
2D Simulation ◽  
Entrainment Effect ◽  
The Relationship

Background/Objectives: Due to the extreme climate and the localized heavy rain, the frequency of debris flow has been increasing. Therefore, there is a growing expectation for accurate numerical analysis.Methods/Statistical analysis: We present a prediction method that can calculate the propagation length of the debris flow. This analysis indicates the relationship between the potential energy and the propagation length of the debris flow. To study the behavior of the debris flow accurately, the change in the momentum force must be considered; otherwise the calculation accuracy of the debris flow behavior is inevitably low.Findings: Entrainment is a common behavior in a debris flow that leads to changes in the momentum force. Here, we analyzed the change in the momentum force using a 2D simulation model that included entrainment. The results show how the debris flow behaves with changes in the momentum force. When entrainment is considered, the propagation length tends to be underestimated. With detailed information, the uncertainty in the prediction accuracy can be reduced.Improvements/Applications: If studies on the material properties of debris flow would be added, it will be possible to carry out various and accurate analysis of the debris flow  

scholarly journals REFLECTIONS FROM COASTAL STRUCTURES

1988 ◽  
Vol 1 (21) ◽  
pp. 58 ◽  
Author(s):  
N.W.H. Allsop ◽  
S.S.L. Hettiarachchi
Keyword(s):  
Wave Motion ◽  
Significant Contribution ◽  
Numerical Models ◽  
Coastal Structures ◽  
Wave Reflections ◽  
Reflected Waves ◽  
Sea Bed ◽  
Wide Range ◽  
Alternative Structure ◽  
General Reduction

Wave reflections at and within a coastal harbour may make a significant contribution to wave disturbance in the harbour. Reflected waves may lead to danger to vessels navigating close to structures, and may reduce the availability of berths within the harbour. Wave reflections may also increase local scour or general reduction in sea bed levels. In the design of breakwaters, sea walls, and coastal revetments, it is therefore important to estimate and compare the reflection performance of alternative structure types. In the use of numerical models of wave motion within harbours, it is essential to define realistically the reflection properties of each boundary. This paper presents results from a study of the reflection performance of a wide range of structures used in coastal and harbour engineering.

scholarly journals Debris Flow Rule Based on Rough Set Theory Extraction from Disaster Caused by the Nagasaki Heavy Rain in July, 1982.

2002 ◽  
pp. 13-25
Author(s):  
Takeharu SATO ◽  
Yasunori KAWANO ◽  
Yoshinori ARAKI ◽  
Hirotaka NAKAYAMA ◽  
Takahisa MIZUYAMA ◽  
...  
Keyword(s):  
Debris Flow ◽  
Set Theory ◽  
Rough Set ◽  
Rough Set Theory ◽  
Heavy Rain ◽  
Flow Rule ◽  
Rule Based

scholarly journals Debris-flow velocities and superelevation in a curved laboratory channel

2015 ◽  
Vol 52 (3) ◽  
pp. 305-317 ◽  
Author(s):  
Christian Scheidl ◽  
Brian W. McArdell ◽  
Dieter Rickenmann
Keyword(s):  
Debris Flow ◽  
Flow Velocity ◽  
Correction Factor ◽  
Debris Flows ◽  
Laboratory Experiments ◽  
Flow Conditions ◽  
Vortex Equation ◽  
Flow Surface ◽  
Sediment Mixture ◽  
Sediment Mixtures

The vortex equation is often used to estimate the front velocity of debris flows using the lateral slope of the flow surface through a channel bend of a given radius. Here we report on laboratory experiments evaluating the application of the vortex equation to channelized debris flows. Systematic laboratory experiments were conducted in a 8 m long laboratory flume with a roughened bed, semi-circular cross section (top width 17 cm), and two different bend radii (1.0 and 1.5 m) with a common bend angle of 60°, and two channel inclinations (15° and 20°). Four sediment mixtures were used with systematic variations in the amount of fine sediment. In the experiments, 12 kg of water-saturated debris were released in a dam-break fashion, and multiple experiments were conducted to verify the repeatability for a given sediment mixture. Data are available for 69 experimental releases at a channel inclination of 20° and 16 releases at an inclination of 15°. Flow velocity was determined with high-speed video, and flow depth and the lateral inclination of the flow surface (superelevation) were measured using laser sensors. In general, the results from an individual sediment mixture are repeatable. We found that the channel slope as well as centerline radius have a significant influence on the correction factor k used in the vortex equation. Relatively coarse-grained sediment mixtures have larger superelevation angles than finer-grained mixtures. We found a statistically significant relation between the correction factor and Froude number. Correction factors of 1 < k < 5 were found for supercritical flow conditions. However, for subcritical flow conditions the correction factor shows a larger value as a function of the Froude number, which leads to an adaption of the forced vortex formula considering active and passive earth pressures. Finally, based on our experimental results, we present a forced vortex equation for debris-flow velocity estimation without a correction factor.

Unusual disturbance: forest change following a catastrophic debris flow in the Canadian Rocky Mountains

2006 ◽  
Vol 36 (9) ◽  
pp. 2204-2215 ◽  
Author(s):  
Stewart B Rood
Keyword(s):  
Debris Flow ◽  
Populus Tremuloides ◽  
Rocky Mountains ◽  
Forest Type ◽  
Populus Trichocarpa ◽  
Heavy Rain ◽  
Extreme Weather Events ◽  
Canadian Rocky Mountains ◽  
Forest Change ◽  
Riparian Tree

Trees are often well adapted to periodic physical disturbances such as fires or floods. However, I investigated forest response to an extremely unusual disturbance event. Following heavy rain in June 1995 a catastrophic debris flow from Vimy Peak in the Canadian Rocky Mountains terminated as an alluvial debris fan that plowed through a trembling aspen (Populus tremuloides Michx.) grove. I analyzed the site over a decade to monitor forest response and determine whether there would be recolonization to the prior forest type. In contrast to my expectation, aspen recolonization did not occur; instead, black cottonwoods (Populus trichocarpa Torr. & Gray) colonized the site. These originated from seedlings and not through clonal propagation, and by 2004, black cottonwoods composed 99% of the saplings and were typically 0.6–1.4 m tall with a density of about 1/m2. The debris fan dramatically changed the physical environment, which partly resembled a floodplain depositional zone and was colonized by the regionally dominant riparian tree. I propose the concept of foreign disturbance to recognize an unusual disturbance that an organism would very rarely experience and thus to which it is unlikely to be adapted. In this example the disturbance produced an abrupt transition to an alternative forest type and this response may provide insight into forest response to other unusual disturbances, such as extreme weather events, that might increase with climate change.

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