Landslides and tsunami generation in large-scale flume experiments and numerical particle-following simulations

2020 ◽  
Author(s):  
Ryan Mulligan ◽  
Alessandro Franci ◽  
Miguel Celigueta ◽  
W. Andy Take
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
High Speed ◽  
Large Scale ◽  
Numerical Technique ◽  
Near Field ◽  
Fluid Velocity ◽  
Breaking Waves ◽  
Generation Process ◽  
Flume Experiments

<p>Tsunamis generated by highly mobile slides in large-scale flume experiments are simulated with a numerical model called the Particle Finite Element Method (PFEM). The numerical technique combines a Lagrangian finite element solution with an efficient remeshing algorithm, and is capable of accurately tracking the evolving fluid free-surface and velocity distribution in highly unsteady flows. The slide material is water, which represents an avalanche or debris flow with high mobility, and the reservoir depth is varied, thereby achieving a range of different near-field wave conditions from breaking waves to near-solitary waves. Experimental observations of fluid velocity and water surface levels are obtained using high-speed digital cameras, acoustic sensors and capacitance wave probes, and the data are used to analyze the accuracy of the PFEM predictions. The numerical model shows the capability of holistically reproducing the entire problem from landslide motion, to impact with water, to wave generation and propagation. Very good agreement with the experimental observations are obtained, in terms of landslide velocity and thickness, wave time series, maximum wave amplitude, wave speed and wave shape. The results demonstrate the potential of this numerical method for simulating mass flows, impacts with water, and the tsunamis generation process.</p>

scholarly journals Simulation Analysis of a Multiple-Vehicle, High-Speed Train Collision Using a Simplified Model

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Suchao Xie ◽  
Weilin Yang ◽  
Ping Xu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
High Speed ◽  
Large Scale ◽  
Computing Time ◽  
Element Model ◽  
Vehicle Body ◽  
Railway Vehicle ◽  
Storage Space ◽  
High Speed Train

To solve the problems associated with multiple-vehicle simulations of railway vehicles including large scale modelling, long computing time, low analysis efficiency, need for high performance computing, and large storage space, the middle part of the train where no plastic deformation occurs in the vehicle body was simplified using mass and beam elements. Comparative analysis of the collisions between a single railway vehicle (including head and intermediate vehicles before, and after, simplification) and a rigid wall showed that variations in impact kinetic energy, internal energy, and impact force (after simplification) are consistent with those of the unsimplified model. Meanwhile, the finite element model of a whole high-speed train was assembled based on the simplified single-vehicle model. The numbers of nodes and elements in the simplified finite element model of the whole train were 63.4% and 61.6%, respectively, compared to those of the unsimplified model. The simplified whole train model using the above method was more accurate than the multibody model. In comparison to the full-size finite element model, it is more specific, had more rapid computational speed, and saved a large amount of computational power and storage space. Finally, the velocity and acceleration data for every car were discussed through the analysis of the collision between two simplified trains at various speeds.

Verification Test for Hybrid Seismic Experimental Method Using Nonlinear Finite Element Method

2005 ◽  
Author(s):  
Yoshihiro Dozono ◽  
Mayumi Fukuyama ◽  
Toshihiko Horiuchi ◽  
Takao Konno ◽  
Michiya Sakai ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Experimental Method ◽  
Large Scale ◽  
Branch Pipe ◽  
Nonlinear Finite Element ◽  
Shaking Table ◽  
Piping System ◽  
Analysis Tool ◽  
Seismic Testing

An improved substructure hybrid seismic experimental method has been developed. This method consists of numerical computations using a general-purpose nonlinear finite element analysis tool and a pseudo-dynamic vibration test. Therefore, it enables seismic testing of large-scale structures that cannot be loaded onto a shaking table. The method also visualizes both data measured by sensors placed on the specimen and the results of the numerical analysis, and it helps us to understand the behavior of an entire structure consisting of a specimen and a numerical model. We performed verification tests for a piping system, in which we used a numerical model including supports, valves, and a branch pipe, and a specimen including two elbows. As results of tests, we conclude that the developed system has enough accuracy to be used as a seismic testing method.

Mobile Payment Development in China

2013 ◽  
Vol 464 ◽  
pp. 416-419
Author(s):  
Li Zhao ◽  
Hua Ying Shu
Keyword(s):  
Financial Institutions ◽  
High Speed ◽  
Large Scale ◽  
Rapid Development ◽  
Near Field ◽  
Mobile Internet ◽  
Mobile Payment ◽  
Industry Chain ◽  
3G Network ◽  
Internet Economy

The thesis first analyzes the concept of mobile payment, and then it makes a distinction between remote payment and near field payment. In addition to that, it infers the development of global mobile payment, which involves the users and the market size. Secondly it probes into Chinas rapid development of mobile internet economy, whose 3G network and smart phones provides high-speed mobile Internet and visual, convenient interface for mobile payment. Thirdly, harmonization of standards of mobile payment will help create industry chain parties openness, cooperation and win-win situation and promote mobile payment intensive and large-scale development process. In the end, it probes into the win-win business model for the telecom operators and financial institutions: Telecom operators will lease SIM card space to obtain revenue and financial institutions will get more fee income.

Numerical modelling of turbulent flow in a combustion tunnel

1982 ◽  
Vol 304 (1484) ◽  
pp. 303-325 ◽  
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
High Speed ◽  
Large Scale ◽  
Numerical Technique ◽  
Vortex Method ◽  
Reacting Flow ◽  
Exothermic Process ◽  
Schlieren Photography ◽  
Large Scale Flow

A numerical technique is presented for the analysis of turbulent flow associated with combustion. The technique uses Chorin’s random vortex method (r.v.m .), an algorithm capable of tracing the action of elementary turbulent eddies and their cumulative effects without imposing any restriction upon their motion. In the past, the r.v.m . has been used with success to treat non-reacting turbulent flows, revealing in particular the mechanics of large-scale flow patterns, the so-called coherent structures. Introduced here is a flame propagation algorithm , also developed by Chorin, in conjunction with volume sources modelling the mechanical effects of the exothermic process of combustion. As an illustration of its use, the technique is applied to flow in a combustion tunnel w here the flame is stabilized by a back-facing step. Solutions for both non-reacting and reacting flow fields are obtained. Although these solutions are restricted by a set of far-reaching idealizations, they nonetheless mimic quite satisfactorily the essential features of turbulent combustion in a lean propane—air mixture that were observed in the laboratory by means of high speed schlieren photography.

Numerical Optimization of a Vaned Shroud Design for Increased Operability Margin in Modern Centrifugal Compressors

2004 ◽  
Author(s):  
M. T. Barton ◽  
M. L. Mansour ◽  
J. S. Liu ◽  
D. L. Palmer
Keyword(s):  
Numerical Optimization ◽  
High Speed ◽  
Numerical Technique ◽  
Three Dimensional ◽  
Grid Generation ◽  
Generation Process ◽  
Surge Margin ◽  
Flow Mixing ◽  
Speed Performance ◽  
Cfd Analyses

This paper describes the computational fluid dynamics (CFD) approach coupled with an automated grid generation technique utilized for the numerical optimization of a modern centrifugal compressor with an inducer vaned shroud for increased operability margin. The grid generation process was automated to permit rapid optimization of the impeller and vaned shroud geometry. A three dimensional (3D), viscous, steady flow, mixing-plane approach was utilized to numerically analyze the impeller and vaned shroud in a coupled fashion to capture the interaction effects. The numerical technique verifies the ability of the vane shroud to extend compressor surge margin at the part-speed operating condition, while maintaining acceptable high-speed performance. CFD analyses confirm that the aerodynamics of the vaned shroud match expectation, and are consistent with the mass-averaged compressor speedline characteristics generated from the CFD results.

scholarly journals Analysis methods of the dynamic structural stress in a full-scale welded carbody for high-speed trains

2018 ◽  
Vol 10 (10) ◽  
pp. 168781401880591 ◽  
Author(s):  
Yaohui Lu ◽  
Heyan Zheng ◽  
Chuan Lu ◽  
Tianli Chen ◽  
Jing Zeng ◽  
...  
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Large Scale ◽  
Dynamic Stress ◽  
Full Scale ◽  
Structural Stress ◽  
Random Load ◽  
Analysis Methods ◽  
Welded Structure ◽  
High Speed Trains

The calculation of the dynamic stress of a large and complex welded carbody is the key to the fatigue design and the durability evaluation of the carbody. Adopting the advanced structural stress based on the finite element method, a new finite element transformation method between random loads and dynamic stresses is proposed to be applied in carbody for high-speed trains. The multi-axial random dynamic load spectrums of full-scale carbody are obtained by the vehicle system dynamics method, and the shell finite element model of a full-scale carbody is established. Adopting the concept of a surrogate model, the finite element transformation relationship between the random load and the dynamic structural stress at concerned points is constructed by using multidisciplinary methods to compute the dynamic stress spectrums of concerned points at the welding seam, and dynamic structural stresses are compared and validated through carbody rig-test. The analysis methods of dynamic structural stress are performed systematically for a full-scale welded structure, which provides reference methods for the fatigue durability evaluation of large-scale welded structures.

Synoptic velocity and pressure fields at the water–sediment interface of streambeds

2010 ◽  
Vol 660 ◽  
pp. 55-86 ◽  
Author(s):  
M. DETERT ◽  
V. NIKORA ◽  
G. H. JIRKA
Keyword(s):  
Flow Structure ◽  
High Speed ◽  
Large Scale ◽  
Pressure Sensors ◽  
Vertical Plane ◽  
Angle Of Repose ◽  
Time Data ◽  
Flume Experiments ◽  
Pressure Pattern ◽  
Velocity Statistics

This paper presents a comprehensive study of the near-bed hydrodynamics at non-moving streambeds based on laboratory experiments in open-channel flows. Pressure and velocity measurements were made with an array of up to 15 miniaturized piezo-resistive pressure sensors within the bed and slightly above it, and a two-dimensional particle-image-velocimetry (PIV) system measuring in streamwise vertical or horizontal planes. Three different types of bed materials were studied covering typical natural streambed conditions. The range of the global Reynolds number covered in the experiments was from 20000 to 200000. This study provides new insights into the flow structure over gravel beds based on the PIV measurements in both streamwise vertical and horizontal planes. In a streamwise vertical plane, large-scale wedge-like flow structures were observed where a zone of faster fluid over-rolled a zone with slower fluid. The resulting shear layer was inclined along the flow at an angle of 10°–25° to the bed, and was populated with clockwise rotating eddies. This mechanism occurred with sufficient frequency and shape to leave an ‘imprint’ in the velocity statistics. Typically, the described flow pattern is formed near the bed and is approximately scaled with the height of the logarithmic layer, although the biggest structures extended over the whole flow depth. In a horizontal near-bed plane, turbulent structures formed a patched ‘chessboard’ pattern with regions of lower and higher velocities that were elongated in the streamwise direction. Their lateral extension was typically two to four times the equivalent sand roughness with lengths up to several water depths. The dimensions of the regions were increasing linearly with the distance from the bed. These findings are consistent with conceptual models originally developed for smooth-wall flows. They also support observations made in rough-bed flume experiments, numerical simulations and natural rivers. Spatial fields of bed-pressure fluctuations were reconstructed by applying Taylor's frozen turbulence hypothesis on time data obtained with an array of pressure sensors. Based on the conditional sampling of velocity patterns associated with pressure-drop events a distinct bed-destabilizing flow-pressure pattern was identified. If a high-speed fluid in the wake of a large-scale wedge-like flow structure reaches the vicinity of the bed, a phenomenon akin to a Bernoulli effect leads to a distinctive low-pressure pattern. The resulting force may exceed the particles' submerged weight and is assumed to be able to give an initial lift to the particle. As a result, the exposed area of a particle is amplified and its angle of repose is reduced, increasing the probability for entrainment.

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