scholarly journals STEADY FLOWS IN THE NEARSHORE ZONE

1984 ◽  
Vol 1 (19) ◽  
pp. 153
Author(s):  
John W. Haines
Keyword(s):  
Vertical Structure ◽  
Field Measurements ◽  
Steady Flows ◽  
Nearshore Zone

Field measurements using electronmagnetic flowmeters on two natural beaches are presented. Mean flows are compared to theory. The horizontal and vertical structure are discussed.

Numerical Investigation of Steady Flow in Proximal and Distal End-to-Side Anastomoses

1996 ◽  
Vol 118 (3) ◽  
pp. 302-310 ◽  
Author(s):  
F. S. Henry ◽  
M. W. Collins ◽  
P. E. Hughes ◽  
T. V. How
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Field Measurements ◽  
In Vitro Models ◽  
Acute Angle ◽  
Careful Examination ◽  
Spatial Gradient ◽  
Steady Flows ◽  
Flow Through

Steady flows in model proximal and distal end-to-side bypass anastomoses were simulated numerically. The predictions were compared to whole field measurements of the flow in in vitro models, and were shown to match well the general features of the measured flows. The predictions confirmed that the flows in end-to-side anastomoses are complex and three dimensional, and contain areas that could allow long residence times. Careful examination of the predictions revealed certain features of the flows not seen easily in the experiments. Shear stress and pressure on the vessel walls were predicted, and areas known to be prone to intimal hyperplasia were shown to correspond to areas of high spatial gradient of shear stress. Two anastomosis angles, 30 and 45 deg, were considered, and it was shown that the more acute angle may have some benefit in terms of the levels of shear gradients and the power required to drive the flow through the anastomosis.

Wind Influence on the Formation of Nearshore Currents in the Southern Baltic: Numerical Modelling Results

2012 ◽  
Vol 59 (1-2) ◽  
pp. 37-48 ◽  
Author(s):  
Andrei Sokolov ◽  
Boris Chubarenko
Keyword(s):  
Field Measurements ◽  
Wave Transformation ◽  
Nearshore Zone ◽  
Field Station ◽  
Longshore Currents ◽  
Baltic Proper ◽  
Wind Influence ◽  
Southern Baltic ◽  
The Baltic ◽  
Drift Component

Abstract A two-dimensional numerical model was used for a simulation of vertical average longshore currents generated by both wind friction and wind-wave action in the nearshore zone. The modelling domain includes the southern part of the Baltic Proper (all boundaries were closed). Wind, uniform in space and varying in time, was the only forcing in the model. The correlation coefficient higher than 0.8 was obtained by model calibration versus the field measurements of currents conducted at the Lubiatowo field station (southern Baltic) during about 1.5 months in 2006. Comparative simulations of total currents including both wind-induced drift and wave components, and of total currents including only a wind-induced drift component, showed that the input of the drift component into currents in the nearshore zone is greater than commonly believed.Wind-induced drift strongly dominates outside the zone of wave transformation, and its input into the total resulting currents remains noticeable even in a zone between the shoreline and the depth of the first wave breaking. Thus, wind-induced drift constitutes up to 50% of the resulting longshore currents for longshore winds and no less than 20% of the longshore component of currents for winds at 45 degrees to the longshore direction.

scholarly journals Warm Spiral Streamers over Gulf Stream Warm-Core Rings

2020 ◽  
Vol 50 (11) ◽  
pp. 3331-3351
Author(s):  
Weifeng (Gordon) Zhang ◽  
Dennis J. McGillicuddy
Keyword(s):  
Surface Waters ◽  
Gulf Stream ◽  
Large Scale ◽  
Vertical Structure ◽  
Water Mass ◽  
Field Measurements ◽  
Mesoscale Dynamics ◽  
Density Anomaly ◽  
Warm Core ◽  
Spiral Structures

AbstractThis study examines the generation of warm spiral structures (referred to as spiral streamers here) over Gulf Stream warm-core rings. Satellite sea surface temperature imagery shows spiral streamers forming after warmer water from the Gulf Stream or newly formed warm-core rings impinges onto old warm-core rings and then intrudes into the old rings. Field measurements in April 2018 capture the vertical structure of a warm spiral streamer as a shallow lens of low-density water winding over an old ring. Observations also show subduction on both sides of the spiral streamer, which carries surface waters downward. Idealized numerical model simulations initialized with observed water-mass densities reproduce spiral streamers over warm-core rings and reveal that their formation is a nonlinear submesoscale process forced by mesoscale dynamics. The negative density anomaly of the intruding water causes a density front at the interface between the intruding water and surface ring water, which, through thermal wind balance, drives a local anticyclonic flow. The pressure gradient and momentum advection of the local interfacial flow push the intruding water toward the ring center. The large-scale anticyclonic flow of the ring and the radial motion of the intruding water together form the spiral streamer. The observed subduction on both sides of the spiral streamer is part of the secondary cross-streamer circulation resulting from frontogenesis on the stretching streamer edges. The surface divergence of the secondary circulation pushes the side edges of the streamer away from each other, widens the warm spiral on the surface, and thus enhances its surface signal.

scholarly journals Burrowing seabirds drive decreased diversity and structural complexity, and increased productivity in insular-vegetation communities

2005 ◽  
Vol 53 (3) ◽  
pp. 231 ◽  
Author(s):  
Wesley J. Bancroft ◽  
J. Dale Roberts ◽  
Mark J. Garkaklis
Keyword(s):  
Vegetation Change ◽  
Vertical Structure ◽  
Structural Complexity ◽  
Field Measurements ◽  
Bare Soil ◽  
Individual Species ◽  
Nutrient Loads ◽  
Functional Interaction ◽  
High Nutrient ◽  
Burrowing Seabirds

Burrow-nesting seabirds, such as the wedge-tailed shearwater (Puffinus pacificus (Gmelin)) physically and chemically engineer the soil of their colonies in a manner that is likely to affect plant growth and ecology. We examined this functional interaction by measuring the diversity, vertical structure and productivity of vegetation in shearwater colonies on Rottnest Island, Western Australia, and by comparing these with those in the adjacent, non-colonised heath. The colony supported a distinct, less diverse vegetation community and was dominated by short-lived, succulent exotics. An ecotone was present between the two communities. Across all species, vegetation was shorter and denser in the colony and individual species that co-occurred in both locations were stunted in the colony. The percentage of bare soil in the colony was double that of the heath. The productivity of a phytometer (Rhagodia baccata) was significantly higher in colony soil than in heath soil. In a glasshouse experiment, cuttings grown in colony soil had 337% of the root mass and 537% of the foliage mass of plants grown in heath soil. Field measurements demonstrated increased leaf set and foliage extension in colony plants. Seed germination from the colony soil (2674 seedlings m–2) greatly exceeded that of the heath (59 seedlings m–2). Dense, productive and species-poor colony vegetation supports the assemblage-level thinning hypothesis as the mechanism for vegetation change, but we argue that prominent colony species are simply better adapted to high nutrient loads and frequent disturbance. A model of vegetation succession is also proposed.

Wind-Induced Waves and Currents in a Nearshore Zone

1997 ◽  
Author(s):  
Nobuhiro Matsunaga ◽  
Misao Hashida ◽  
Hiroshi Kawakami
Keyword(s):  
Nearshore Zone ◽  
Waves And Currents
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