Using nonlinear forecasting to learn the magnitude and phasing of time-varying sediment suspension in the surf zone

1996 ◽  
Vol 101 (C6) ◽  
pp. 14283-14296 ◽  
Author(s):  
Bruce E. Jaffe ◽  
David M. Rubin
Keyword(s):  
Surf Zone ◽  
Time Varying ◽  
Sediment Suspension ◽  
Nonlinear Forecasting

scholarly journals SEDIMENT SUSPENSION DUE TO LARGE SCALE EDDIES IN THE SURF ZONE

1988 ◽  
Vol 1 (21) ◽  
pp. 122 ◽  
Author(s):  
Kazuo Nadaoka ◽  
Seizo Ueno ◽  
Tatsuyuki Igarashi
Keyword(s):  
Large Scale ◽  
Laboratory Experiments ◽  
Surf Zone ◽  
Fiber Optic ◽  
Three Dimensional ◽  
Sampling Technique ◽  
Visual Observation ◽  
Coherence Analysis ◽  
Data Sets ◽  
Sediment Suspension

Laboratory experiments using a fiber-optic LDV system and a small pressure transducer have been made to reveal detailed characteristics of the velocity field in the surf zone and its relationship to the sediment suspension with special reference to the three-dimensional large scale eddies referred to as "obliquely descending eddies", the existence of which was recently revealed by Nadaoka (1986). A conditional sampling technique has been used to find that the obliquely descending eddies bring highly intermittent intensive turbulence to the bottom with the large onshoreward momentum at the upper layer of the water and thus essentially characterize the turbulent flow field in the surf zone. Visual observation and concentration measurements, especially a coherence analysis of two data sets of concentration close to the bottom, have shown that the sediment suspension is mostly governed by such large scale eddies in a wide extent of the surf zone; i.e., the eddies hit the bottom and then lift up the sediment into suspension, yielding the spot-like sediment cloud in accordance with the three-dimensional eddy structure.

scholarly journals USE OF DIGITAL HOLOGRAPHIC CAMERAS TO EXAMINE THE MEASUREMENT AND UNDERSTANDING OF SEDIMENT SUSPENSION IN THE NEARSHORE

2012 ◽  
Vol 1 (33) ◽  
pp. 73
Author(s):  
Daniel Conley ◽  
Daniel Buscombe ◽  
Alex Nimmo-Smith
Keyword(s):  
Size Distribution ◽  
Suspended Sediment ◽  
Surf Zone ◽  
Sediment Concentration ◽  
Acoustic Backscatter ◽  
Sediment Suspension ◽  
Data Set ◽  
Sediment Grain Size ◽  
Grain Sizes ◽  
Wide Range

We present results from a 3-week field experiment measuring surf-zone flows and sediment transport on a steep energetic beach in the south-west UK, including the first reported deployment of an in-line holographic camera (‘holocam’) in the surf zone, co-located with various optical backscatter sensors and an acoustic backscatter sensor (ABS). The extensive data set provides perhaps a unique opportunity to examine the performance of optical and acoustic backscatter instruments in a wide range of conditions including bubbly flows, as well as some fundamental aspects of sediment suspension processes such as the near-bed size-distribution of suspended sediment. The holocam, deployed with a 1.3cm cubic sample volume approximately 10cm above the bed, provides in-focus well-resolved images of the instantaneous suspended load, making it possible to determine highly-accurate estimates of the concentrations of mineral sand grains, bubbles and organic particles, and their size distributions. Instantaneous estimates of sediment concentration from the ABS compare poorly with the equivalent measure from the holocam. This could be due to various factors such as spatial decorrelation or acoustic insensitivities at larger grain sizes. However, the ABS does a very good job at estimating burst-averaged suspended sediment concentrations when bubble concentrations are low (less than 1ml/l). The error in ABS concentrations (as compared against holocam) appears to be related to relative bubble concentration. The OBS is even more sensitive to bubbles. Suspended sediment grain size distribution is skewed towards the finer grain sizes but shifts to the larger sizes with increased flow intensity.

scholarly journals MEASUREMENTS OF SURF BEAT AND SET-DOWN BENEATH WAVE GROUPS

1984 ◽  
Vol 1 (19) ◽  
pp. 49 ◽  
Author(s):  
J.K. Kostense
Keyword(s):  
Surf Zone ◽  
Time Varying ◽  
Equal Frequency ◽  
Wave Groups ◽  
Free Wave ◽  
Wave Channel ◽  
Long Wave ◽  
The Difference ◽  
Active Wave ◽  
Good Agreement

A laboratory study was conducted to measure the amplitudes of long waves In shallow water as induced by wave grouping. In a 55 m long wave channel with a plane beach at the end, two primary waves of nearly equal frequency were generated. Due to a sophisticated control of the wave paddle - including second order wave generation as well as active wave absorption at the paddle face - the wave action at the difference frequency was limited to an incident forced wave, propagating at the group velocity, and a reflected free wave generated in the surf zone. For the incident forced - or bound - wave, also known as set-down, the experimental results show good agreement with the existing theory. Furthermore, the experiments confirm qualitatively a theoretical model by Symonds et al. (198 2) explaining two-dimensional surf beat as a result of the time-varying breakpoint of the incident primary waves.

Sign in / Sign up

Export Citation Format

Share Document