scholarly journals NUMERICAL SIMULATIONS AND ASSESSMENTS OF PERFORATED BREAKWATERS

2018 ◽  
pp. 19
Author(s):  
Philip L.-F. Liu ◽  
Pablo Higuera
Keyword(s):  
Numerical Simulations ◽  
Laboratory Experiments ◽  
Numerical Solutions ◽  
Scale Effects ◽  
Laboratory Data ◽  
Physical Processes ◽  
Hydrodynamic Processes ◽  
Wave Trains ◽  
Perforated Breakwater ◽  
Rectangular Columns

In this paper we study the physical processes of regular wave trains impacting on a perforated breakwater. The breakwater consists of an array of vertical rectangular columns and a backwall. We have performed numerical simulations in which reflection coefficients have been calculated based on the Mansard and Funke (1980) theory and compared with laboratory data and analytical solutions (Kakuno et al. 1992, Kakuno & Liu, 1993). The numerical solutions will be further analyzed to describe the hydrodynamic processes, identify the limitations of the analytical theory and the scale effects in the laboratory experiments.

scholarly journals Predicting Fault Slip via Transfer Learning

2021 ◽  
Author(s):  
Kun Wang ◽  
Christopher Johnson ◽  
Kane Bennett ◽  
Paul Johnson
Keyword(s):  
Machine Learning ◽  
Numerical Simulations ◽  
Transfer Learning ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Fault Slip ◽  
Geophysical Data ◽  
Training Data ◽  
Data Sets ◽  
Earthquake Cycle

Abstract Data-driven machine-learning for predicting instantaneous and future fault-slip in laboratory experiments has recently progressed markedly due to large training data sets. In Earth however, earthquake interevent times range from 10's-100's of years and geophysical data typically exist for only a portion of an earthquake cycle. Sparse data presents a serious challenge to training machine learning models. Here we describe a transfer learning approach using numerical simulations to train a convolutional encoder-decoder that predicts fault-slip behavior in laboratory experiments. The model learns a mapping between acoustic emission histories and fault-slip from numerical simulations, and generalizes to produce accurate results using laboratory data. Notably slip-predictions markedly improve using the simulation-data trained-model and training the latent space using a portion of a single laboratory earthquake-cycle. The transfer learning results elucidate the potential of using models trained on numerical simulations and fine-tuned with small geophysical data sets for potential applications to faults in Earth.

scholarly journals NUMERICAL MODELING OF COASTAL TSUNAMI IMPACT DISSIPATION AND IMPACT

2012 ◽  
Vol 1 (33) ◽  
pp. 9 ◽  
Author(s):  
Stephan T. Grilli ◽  
Jeffrey C. Harris ◽  
Fengyan Shi ◽  
James T. Kirby ◽  
Tayebeh S. Tajalli Bakhsh ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
East Coast ◽  
Tsunami Hazard ◽  
Physical Processes ◽  
Numerical Work ◽  
Tsunami Waves ◽  
Long Wave ◽  
Tsunami Hazard Assessment ◽  
Long Time ◽  
Wave Trains

Recent observations of the coastal impact of large tsunamis (e.g., Indian Ocean 2004; Tohoku 2011) and related numerical and theoretical works have made it increasingly clear that tsunami waves arrive nearshore as a series of long waves (so-called N-waves) with, often, the superposition of undular bores around each crest. Such wave trains are much more complex and very much in contrast with the solitary wave paradigm which for a long time was the accepted idealization of tsunami waves in both experimental and numerical work. The dissipation associated with these breaking bores can be very large, particularly over a wide and shallow continental shelf such as along the east coast of North America, particularly for the shorter waves associated with tsunamis generated by Submarine Mass Failures (SMFs). In this paper, we perform numerical simulations of tsunami coastal impact in the context of both idealized laboratory experiments and several tsunami case studies. We attempt to clarify the key physical processes at play in such cases, and discuss the parameterization of long wave dissipation and implications for models of coastal tsunami hazard assessment.

Laboratory-scale swash flows generated by a non-breaking solitary wave on a steep slope

2018 ◽  
Vol 847 ◽  
pp. 186-227 ◽  
Author(s):  
P. Higuera ◽  
P. L.-F. Liu ◽  
C. Lin ◽  
W.-Y. Wong ◽  
M.-J. Kao
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Solitary Wave ◽  
Numerical Simulations ◽  
Hydraulic Jump ◽  
High Speed ◽  
Laboratory Experiments ◽  
Numerical Solutions ◽  
Steep Slope ◽  
Bottom Shear Stress

The main goal of this paper is to provide insights into swash flow dynamics, generated by a non-breaking solitary wave on a steep slope. Both laboratory experiments and numerical simulations are conducted to investigate the details of runup and rundown processes. Special attention is given to the evolution of the bottom boundary layer over the slope in terms of flow separation, vortex formation and the development of a hydraulic jump during the rundown phase. Laboratory experiments were performed to measure the flow velocity fields by means of high-speed particle image velocimetry (HSPIV). Detailed pathline patterns of the swash flows and free-surface profiles were also visualized. Highly resolved computational fluid dynamics (CFD) simulations were carried out. Numerical results are compared with laboratory measurements with a focus on the velocities inside the boundary layer. The overall agreement is excellent during the initial stage of the runup process. However, discrepancies in the model/data comparison grow as time advances because the numerical model does not simulate the shoreline dynamics accurately. Introducing small temporal and spatial shifts in the comparison yields adequate agreement during the entire rundown process. Highly resolved numerical solutions are used to study physical variables that are not measured in laboratory experiments (e.g. pressure field and bottom shear stress). It is shown that the main mechanism for vortex shedding is correlated with the large pressure gradient along the slope as the rundown flow transitions from supercritical to subcritical, under the developing hydraulic jump. Furthermore, the bottom shear stress analysis indicates that the largest values occur at the shoreline and that the relatively large bottom shear stress also takes place within the supercritical flow region, being associated with the backwash vortex system rather than the plunging wave. It is clearly demonstrated that the combination of laboratory observations and numerical simulations have indeed provided significant insights into the swash flow processes.

scholarly journals How to adapt numerical simulation of wave propagation and ultrasonic laboratory experiments to be comparable — A case study for a complex topographic model

Geophysics ◽  
2018 ◽  
Vol 83 (4) ◽  
pp. T195-T207 ◽  
Author(s):  
Bence Solymosi ◽  
Nathalie Favretto-Cristini ◽  
Vadim Monteiller ◽  
Dimitri Komatitsch ◽  
Paul Cristini ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Numerical Simulations ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Computational Cost ◽  
Seismic Exploration ◽  
Quality Data ◽  
Small Scale ◽  
Water Tank ◽  
Zero Offset

Numerical methods are widely used in seismic exploration to simulate wave propagation; however, the algorithms are based on various assumptions. The accuracy of numerical simulations is of particular interest in the case of realistic geologic setups. The direct comparison of numerical results can have limitations, and an alternative approach can be the comparison of synthetic results with experimental data, obtained for a small-scale physical model in laboratory conditions. Laboratory experiments are repeatable and provide high-quality data for a known configuration. We have developed a possible workflow to adapt the numerical simulations and the laboratory experiments to each other, such that the two can be easily compared with high accuracy. The model is immersed in a water tank, and a conventional pulse-echo technique is used to collect the reflection data in zero-offset and offset configurations. We use a spectral-element method for the numerical modeling. The model geometry is implemented using a nonstructured mesh, and the computational cost can be optimized using larger elements and higher-order basis functions. The real source transducer characteristics are implemented based on a new approach: laboratory characterization of the impulse response, followed by an inversion step to obtain a numerically equivalent source. The comparison of the zero-offset synthetic and laboratory results reveals an excellent fit in terms of arrival time, phase, and amplitude. Minor amplitude mismatches may be attributed to the noise recorded in the laboratory data and to the possible inaccuracy of the proposed source implementation. Comparison of the simulated and laboratory offset traces also exhibits a good fit in general, but with significantly less accuracy for some arrivals than in the zero-offset case. This can be mainly attributed to the inaccuracies of the transducer positions during the laboratory measurements combined with the strong topography of the model.

Free and Forced Vibrations of the Strongly Nonlinear Cubic-Quintic Duffing Oscillators

2017 ◽  
Vol 72 (1) ◽  
pp. 59-69 ◽  
Author(s):  
M.M. Fatih Karahan ◽  
Mehmet Pakdemirli
Keyword(s):  
Numerical Simulations ◽  
Numerical Solutions ◽  
Multiple Scales ◽  
Approximate Solutions ◽  
Response Curves ◽  
Strongly Nonlinear ◽  
Free And Forced Vibrations ◽  
Approximate Analytical Solutions ◽  
Strongly Nonlinear Oscillators ◽  
Good Agreement

AbstractStrongly nonlinear cubic-quintic Duffing oscillatoris considered. Approximate solutions are derived using the multiple scales Lindstedt Poincare method (MSLP), a relatively new method developed for strongly nonlinear oscillators. The free undamped oscillator is considered first. Approximate analytical solutions of the MSLP are contrasted with the classical multiple scales (MS) method and numerical simulations. It is found that contrary to the classical MS method, the MSLP can provide acceptable solutions for the case of strong nonlinearities. Next, the forced and damped case is treated. Frequency response curves of both the MS and MSLP methods are obtained and contrasted with the numerical solutions. The MSLP method and numerical simulations are in good agreement while there are discrepancies between the MS and numerical solutions.

scholarly journals Motion of a tightly fitting axisymmetric object through a lubricated elastic tube

2021 ◽  
Vol 926 ◽  
Author(s):  
Bhargav Rallabandi ◽  
Jens Eggers ◽  
Miguel Angel Herrada ◽  
Howard A. Stone
Keyword(s):  
Numerical Simulations ◽  
Numerical Solutions ◽  
Elastic Tube ◽  
Direct Numerical Simulations ◽  
Fluid Film ◽  
Square Root ◽  
Membrane Tension ◽  
Relative Speed ◽  
Thin Fluid ◽  
Thin Fluid Film

We consider the translation of a rigid, axisymmetric, tightly fitting object through a cylindrical elastic tube filled with viscous fluid, using a combination of theory and direct numerical simulations. The intruding object is assumed to be wider than the undeformed tube radius, forcing solid–solid contact in the absence of relative motion. The motion of the object establishes a thin fluid film that lubricates this contact. Our theory couples lubrication theory to a geometrically nonlinear membrane description of the tube's elasticity, and applies to a slender intruding object and a thin tube with negligible bending rigidity. We show using asymptotic and numerical solutions of the theory, that the thickness of the thin fluid film scales with the square root of the relative speed for small speeds, set by a balance of hoop stresses, membrane tension and fluid pressure. While membrane tension is relatively small at the entrance of the film, it dominates near the exit and produces undulations of the film thickness, even in the limit of vanishing speeds and slender objects. We find that the drag force on the intruding object depends on the slope of its surface at the entrance to the thin fluid film, and scales as the square root of the relative speed. The predictions of the lubricated membrane theory for the shape of the film and the force on the intruder are in quantitative agreement with three-dimensional direct numerical simulations of the coupled fluid–elastic problem.

Numerical solutions to wave interaction with rubblemound breakwaters

1990 ◽  
Vol 17 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Kevin R. Hall
Keyword(s):  
Numerical Modelling ◽  
Numerical Solution ◽  
Numerical Solutions ◽  
Scale Effects ◽  
Numerical Models ◽  
Internal Flow ◽  
Wave Interaction ◽  
Theoretical Development ◽  
Porous Media Flow ◽  
Complex Flow

The interaction of a wave with a rubblemound breakwater results in a complex flow field which is both nonlinear and turbulent, particularly within a region close to the surface of the structure. Numerical models describing internal flow in a rubblemound breakwater are becoming increasingly important, particularly as the influence of scale effects on internal flow in physical hydraulic models are becoming understood as important. A number of numerical models to predict the internal breakwater flow kinematics have been produced in the past two decades. This paper provides a review of the state-of-the-art of numerical modelling of wave interaction with rubblemound breakwaters. Details of the theoretical development and the resulting numerical solution techniques are presented. Methods for incorporating secondary effects such as two-phase (air–water) flow, inertia, and unbalanced boundary conditions are discussed. Limitations of the models resulting from the validity of the assumptions made in order to effect a numerical solution are discussed. Key words: breakwaters, internal flow, porous media flow, numerical modelling, rubblemound breakwaters.

Analysis of Physical Processes in a Holding Electrical Furnace

2014 ◽  
Vol 698 ◽  
pp. 188-192
Author(s):  
Victor Timofeev ◽  
Sergey Perfilyev
Keyword(s):  
Aluminum Alloys ◽  
Present Article ◽  
Automated Design ◽  
Physical Processes ◽  
Electrical Furnace ◽  
Hydrodynamic Processes

The present article describes the results of automated design and analysis of electromagnetic, thermal and hydrodynamic processes in a holding electrical furnace for preparation of aluminum alloys. The availability of a parameter model enables to design a furnace of any given capacity in quick time and carry out an analysis of physical processes in it.

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