Impact of low-head dams on bedload transport rates in coarse-bedded streams

An experimental study of the transport of sediment in a part-full pipe was carried out in a concrete pipe. The experiments were confined to bedload transport. The purpose of this study was to analyze the flow conditions that characterize the stream traction in pipe channels and their relationship to flow resistance and sediment transport rate. Three procedures used in this kind of experimental study were tested and found valid: 1) the vertical velocity distribution near the sediment bed can be described by the velocity-defect law, 2) the side wall elimination procedure can be used to compute the hydraulic radius of the sediment bed, and 3) the critical shear stress of the sediment particles can be obtained by using Shields' diagram. A relationship to estimate bedload transport, based on dimensional analysis, was proposed. This was expressed in terms of both flow and particle parameters as well as geometric factors. Further experimental work is recommended before this relationship can be fully incorporated in a simulation model for the analysis of storm sewers.

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Utilization of Water Energy Potential on Tail Race for Very Low Head Hydro Power Plant

2020 International Conference on Sustainable Energy Engineering and Application (ICSEEA) ◽

10.1109/icseea50711.2020.9306142 ◽

2020 ◽

Author(s):

Ridwan Arief Subekti ◽

Anjar Susatyo ◽

Henny Sudibyo ◽

Ghalya Pikra

Keyword(s):

Power Plant ◽

Energy Potential ◽

Hydro Power ◽

Low Head

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Numerical investigation of alleviation of undesirable effect of inter-blade vortex with air admission for a low-head Francis turbine

Journal of Hydrodynamics ◽

10.1007/s42241-020-0081-6 ◽

2020 ◽

Vol 32 (6) ◽

pp. 1151-1164

Author(s):

Long-gang Sun ◽

Peng-cheng Guo ◽

Luo-chang Wu

Keyword(s):

Numerical Investigation ◽

Francis Turbine ◽

Undesirable Effect ◽

Low Head

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The intensity of slope and fluvial processes after a catastrophic windthrow event in small catchments in the Tatra Mountains

Journal of Mountain Science ◽

10.1007/s11629-021-6726-2 ◽

2021 ◽

Vol 18 (6) ◽

pp. 1405-1423

Author(s):

Dariusz Strzyżowski ◽

Elżbieta Gorczyca ◽

Kazimierz Krzemień ◽

Mirosław Żelazny

Keyword(s):

Environmental Changes ◽

Bedload Transport ◽

Strong Wind ◽

Tatra Mountains ◽

Salvage Logging ◽

Fluvial Processes ◽

Wind Events ◽

And Control ◽

The Tatra Mountains ◽

The Impact

AbstractStrong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation.

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Optimization of Low Head Axial-Flow Turbines for an Overtopping BReakwater for Energy Conversion: A Case Study

Energies ◽

10.3390/en14154618 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4618

Author(s):

Antonio Mariani ◽

Gaetano Crispino ◽

Pasquale Contestabile ◽

Furio Cascetta ◽

Corrado Gisonni ◽

...

Keyword(s):

Energy Conversion ◽

Control Strategy ◽

Energy Production ◽

San Antonio ◽

Axial Flow ◽

Complex Process ◽

Low Head ◽

Wave Power Conversion ◽

And Control

Overtopping-type wave power conversion devices represent one of the most promising technology to combine reliability and competitively priced electricity supplies from waves. While satisfactory hydraulic and structural performance have been achieved, the selection of the hydraulic turbines and their regulation is a complex process due to the very low head and a variable flow rate in the overtopping breakwater set-ups. Based on the experience acquired on the first Overtopping BReakwater for Energy Conversion (OBREC) prototype, operating since 2016, an activity has been carried out to select the most appropriate turbine dimension and control strategy for such applications. An example of this multivariable approach is provided and illustrated through a case study in the San Antonio Port, along the central coast of Chile. In this site the deployment of a breakwater equipped with OBREC modules is specifically investigated. Axial-flow turbines of different runner diameter are compared, proposing the optimal ramp height and turbine control strategy for maximizing system energy production. The energy production ranges from 20.5 MWh/y for the smallest runner diameter to a maximum of 34.8 MWh/y for the largest runner diameter.

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