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Projects / Programmes source: ARIS

Erosion in Coastal Seas and Navigable Rivers

Research activity

Code Science Field Subfield
2.20.00  Engineering sciences and technologies  Hydrology   

Code Science Field
T220  Technological sciences  Civil engineering, hydraulic engineering, offshore technology, soil mechanics 

Code Science Field
2.07  Engineering and Technology  Environmental engineering  
Keywords
sediment erosion, sediment resuspension, bottom stress, propeller's jet, ship waves, orbital velocity of waves
Evaluation (rules)
source: COBISS
Researchers (8)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  13407  PhD Branko Čermelj  Biology  Researcher  2018 - 2022  182 
2.  08247  PhD Matjaž Četina  Hydrology  Researcher  2018 - 2022  586 
3.  18338  Tihomir Makovec    Technical associate  2018 - 2022  386 
4.  05226  PhD Vlado Malačič  Hydrology  Head  2018 - 2022  366 
5.  26112  PhD Gorazd Novak  Hydrology  Researcher  2018 - 2022  126 
6.  20320  PhD Boris Petelin  Hydrology  Researcher  2018 - 2022  127 
7.  10903  Milijan Šiško  Biology  Technical associate  2018 - 2022  239 
8.  12068  PhD Dušan Žagar  Mechanics  Researcher  2018 - 2022  766 
Organisations (2)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0105  National Institute of Biology  Ljubljana  5055784  13,335 
2.  0792  University of Ljubljana, Faculty of Civil and Geodetic Engineering  Ljubljana  1626981  26,383 
Abstract
In coastal seas, as well as in navigable rivers, the issue of erosion of the bottom of water bodies or their banks is one of the most important challenges in coastal and riverine engineering. The basic principles of erosion of a substrate over which the volume of fluid (water) flows have long been known and are grounded on a surpassing of the bottom shear stress, a critical bottom stress value. The former is caused by the vertical shear of the velocity of currents and waves while the latter depends heavily on the nature of the substrate. Three major possible mechanisms by which the moving vessels may erode sediments ANG are: 1. erosion due to changes of a flow field by a ship’s movement in the absence of propeller’s propulsion 2. erosion due to propeller wake that reaches the sea bottom or near-shore area 3. erosion due to ship waves that reach near-shore zone. We intend to complement field observations with state-of-the art equipment, e.g. Laser In-Situ Scattering and Transmissometery (LISST) instruments operated by a Slovenian and a Hungarian team to measure the size distribution of suspended sediments (and their falling speeds)[1], and acoustic probes for the measurement of near-bottom turbulence[2] and for acoustic current meter profilers (ADCP), with the addition of turbidimeters. The microstructure probe[3] (Slovenian team) will make available vertical profiles of density and turbulence. Field observations will also be complemented by numerical modelling of fluid motion and sediment transport in the northern Adriatic[4] and the River Danube[5]. Analytical expressions will also be utilized appropriately. The original method of estimating bottom stress under the direct influence of vessel passage over (nearby) a spot at depth will be applied. There have been numerous research papers and reports stimulated by significant damage on moored vessels from ship passage. To our knowledge, studies relating a velocity (near) field around the vessel to bottom stress are extremely scarce, so this present study will thus be novel. There have been many studies concerning propeller wash, relating the propeller’s vorticity trail behind a ship, considered a jet, to bottom stress. Two aspects will be new in this study: First, the numerical merge of a narrow jet structure with an ambient velocity field due to circulation, which is feasible along the vessel’s path using the adaptive mesh concept, or the one-way nesting concept within the fixed ‘hot-spot’ area. A second topic is more a conceptual one: an in-depth study should remove doubts concerning tangential (and radial) velocity components in intertwined swirling vorticity trails, generated by each of the propeller blades, on bottom stress. The third element of the study, on ship waves affecting the bottom sediment (and organisms on it) in a very-near-shore zone is also novel. It will combine video imaging of the near-shore area where waves break, the high-frequency measurements of the velocities near the bottom and the sophisticated numerical modeling in a model grid of an order of 1 cm. Bottom stress will be calculated by several methods. The concept developed for the calm areas on the Danube banks will also be directly applicable to coastal sea problems. The proposed project will explore all important mechanisms of ship-generated erosion of sediments on the sea and river floor. This research of a broader picture of the effects of ship motion will select from three major mechanisms the most important ones that matter at a specific site. [1] http://www.sequoiasci.com/product/lisst-100x/ [2] http://www.nortek-as.com/en/products/velocimeters/vector; http://www.fondriest.com/pdf/sontek_adv_spec.pdf [3] http://www.sea-sun-tech.com/marine-tech/offshore/mss-microstructureprobe/ mss-90-profiler-microstructure-probe.html [4] http://www.ccpo.odu.edu/POMWEB/ http://www.hydroqual.com/ehst_ecomsed.html [5] http://folk.ntnu.no/nilsol/ssiim/
Significance for science
State of the art field observations, numerical simulations and hydrodynamic analysis of three key mechanisms (bypassing of vessels, the propellers jet during manoeuvring, arrivals to and departures from ports/berths, and ship waves) that affect erosion of shallow bottom will contribute to the development of engineering sciences in the field of environmental fluid dynamics. We will also introduce novel methods in the observation and analysis of these mechanisms. This seems to be one of first projects that will embrace these different mechanisms. The assessment of their relative impact on the erosion in specific coastal zones will represent a significant contribution to science.
Significance for the country
State of the art field observations, numerical simulations and hydrodynamic analysis of three key mechanisms (bypassing of vessels, the propellers jet during manoeuvring, arrivals to and departures from ports/berths, and ship waves) that affect erosion of shallow bottom will contribute to the development of engineering sciences in the field of environmental fluid dynamics. We will also introduce novel methods in the observation and analysis of these mechanisms. This seems to be one of first projects that will embrace these different mechanisms. The assessment of their relative impact on the erosion in specific coastal zones will represent a significant contribution to science.
Most important scientific results Interim report
Most important socioeconomically and culturally relevant results
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