scholarly journals CROSS-SHORE TRANSPORT ON GRAVEL BEACHES

2011 ◽  
Vol 1 (32) ◽  
pp. 43
Author(s):  
Betsy S. Hicks ◽  
Nobuhisa Kobayashi ◽  
Jack A. Puleo ◽  
Ali Farhadzadeh
Keyword(s):  
Experimental Investigation ◽  
Numerical Model ◽  
Incident Wave ◽  
Small Scale ◽  
Quasi Equilibrium ◽  
Wave Flume ◽  
Test Conditions ◽  
Equilibrium Profiles ◽  
Hydrodynamic Data ◽  
Gravel Beach

A numerical and experimental investigation of profile evolution was completed on a laboratory gravel beach. A total of four tests were completed on a gravel beach constructed in a small-scale wave flume, with different incident wave conditions and initial beach slopes. The tests allowed for an examination of erosional, accretional, and migratory bar conditions as well as how the differences affected the final quasi-equilibrium profiles. Profile evolution and hydrodynamic data were collected for comparison with the time- and depth- averaged numerical model CSHORE. The numerical formulations developed for damage progression on a stone armor layer were found to predict the profile evolution on the steeper test conditions but required modifications to the bedload formula to better predict the accretional and bar migration tests.

Three-Dimensional Modeling of Wave-Induced Seabed Response Around a Semi-Buried Pipeline: A Small-Scale Case

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Jianfeng Zhu ◽  
Hongyi Zhao
Keyword(s):  
Numerical Model ◽  
Three Dimensional ◽  
The Body ◽  
Navier Stokes ◽  
Small Scale ◽  
Buried Pipeline ◽  
Consolidation Process ◽  
Soil Response ◽  
Wave Flume ◽  
Wave Induced

Abstract In this paper, a three-dimensional integrated numerical model for a small-scale case of wave-induced oscillatory soil response around a semi-buried pipeline (PORO-WSSI-PIPE 3D) is proposed. In this model, we combine the Reynolds-averaged Navier–Stokes (RANS) equations for the 3D wave motions and the Biot’s consolidation equations for a porous elastic seabed foundation through pressure continuity at common boundaries, with pipeline being an elastic and impermeable medium. The computational results are validated through comparison with previous analytical solutions and laboratory wave flume tests, obtaining good agreement. Following validation, the numerical model is applied to simulate wave-seabed-pipeline interaction with different obliquities between pipeline and incident wave, varying from 30 deg to 90 deg. Snapshots of wave-seabed-pipeline interaction, as well as dynamic pore pressure distributions at typical locations in the vicinity of a semi-buried pipeline, are obtained and analyzed. The three-dimensional consolidation process of seabed under gravitational forces including the body forces of a pipeline is also discussed.

scholarly journals Quasi-equilibrium models of high-redshift disc galaxy evolution

2020 ◽  
Vol 500 (3) ◽  
pp. 3394-3412
Author(s):  
Steven R Furlanetto
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Formation Rate ◽  
New Physics ◽  
Small Scale ◽  
Quasi Equilibrium ◽  
Mass Relation ◽  
Disc Galaxy

ABSTRACT In recent years, simple models of galaxy formation have been shown to provide reasonably good matches to available data on high-redshift luminosity functions. However, these prescriptions are primarily phenomenological, with only crude connections to the physics of galaxy evolution. Here, we introduce a set of galaxy models that are based on a simple physical framework but incorporate more sophisticated models of feedback, star formation, and other processes. We apply these models to the high-redshift regime, showing that most of the generic predictions of the simplest models remain valid. In particular, the stellar mass–halo mass relation depends almost entirely on the physics of feedback (and is thus independent of the details of small-scale star formation) and the specific star formation rate is a simple multiple of the cosmological accretion rate. We also show that, in contrast, the galaxy’s gas mass is sensitive to the physics of star formation, although the inclusion of feedback-driven star formation laws significantly changes the naive expectations. While these models are far from detailed enough to describe every aspect of galaxy formation, they inform our understanding of galaxy formation by illustrating several generic aspects of that process, and they provide a physically grounded basis for extrapolating predictions to faint galaxies and high redshifts currently out of reach of observations. If observations show violations from these simple trends, they would indicate new physics occurring inside the earliest generations of galaxies.

Experimental study of the initial stages of wind waves' spatial evolution

2011 ◽  
Vol 681 ◽  
pp. 462-498 ◽  
Author(s):  
DAN LIBERZON ◽  
LEV SHEMER
Keyword(s):  
Energy Transfer ◽  
Growth Rates ◽  
Water Surface ◽  
Wind Waves ◽  
Pressure Fluctuations ◽  
Theoretical Models ◽  
Small Scale ◽  
Wave Flume ◽  
Spatial Growth ◽  
The Mean

Despite a significant progress and numerous publications over the last few decades a comprehensive understanding of the process of waves' excitation by wind still has not been achieved. The main goal of the present work was to provide as comprehensive as possible set of experimental data that can be quantitatively compared with theoretical models. Measurements at various air flow rates and at numerous fetches were carried out in a small scale, closed-loop, 5 m long wind wave flume. Mean airflow velocity and fluctuations of the static pressure were measured at 38 vertical locations above the mean water surface simultaneously with determination of instantaneous water surface elevations by wave gauges. Instantaneous fluctuations of two velocity components were recorded for all vertical locations at a single fetch. The water surface drift velocity was determined by the particle tracking velocimetry (PTV) method. Evaluation of spatial growth rates of waves at various frequencies was performed using wave gauge records at various fetches. Phase relations between various signals were established by cross-spectral analysis. Waves' celerities and pressure fluctuation phase lags relative to the surface elevation were determined. Pressure values at the water surface were determined by extrapolating the measured vertical profile of pressure fluctuations to the mean water level and used to calculate the form drag and consequently the energy transfer rates from wind to waves. Directly obtained spatial growth rates were compared with those obtained from energy transfer calculations, as well as with previously available data.

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