EPRI recommends improvements to runners to aid fish survival
To improve survival of fish passing through hydroelectric turbines, EPRI recommends use of turbine runners with thick leading edge blades shaped in a semi circle. This is based on results from a four-year research project on fish mortality due to turbine blade strike.
The objective of the research project was to better understand fish mortality due to hydroturbine blade strike and then to improve the design of blade leading edge shapes to minimize this mortality.
The work was sponsored by EPRI and performed at the Alden Research Laboratory in Holden, Mass.
Efforts during the final year of the project focused on:
- – Computational fluid dynamics (CFD) analysis of several leading edge geometries;
– Design and construction of a linear test facility for accelerating blades with the most favorable leading edge shape identified during the CFD study; and
– Biological evaluation of blade strike using the leading edge design considered to have the most potential for minimizing fish injury.
EPRI added this final year to the program to test fish injuries at the higher blade speeds frequently encountered with actual turbines.
Results from the final year of research are contained in Evaluation of the Effects of Turbine Blade Leading Edge Design on Fish Survival. The report discusses the CFD evaluation of leading edge blade geometries, the CFD simulation scope and methods, and results of two- and three-dimensional simulations. For the biological evaluation, tests were performed on rainbow trout, white sturgeon, and American eel.
– For information on access to the final report, contact Doug Dixon, project manager, at (1) 804-642-1025; E-mail: firstname.lastname@example.org.
Research projects proceed at outdoor testing facility
Five research projects are under way at the new Outdoor StreamLab at St. Anthony Falls Laboratory (SAFL).
These projects are intended to:
- – Establish appropriate metrics for sediment-related total maximum daily loads in rivers and streams;
– Predict water residence time and sedimentation within patches of aquatic vegetation in river channels;
– Expand knowledge of the effects of stream restoration projects in small sand-bed rivers;
– Determine which forces control water surface super-elevation within meander bends of a river; and
– Develop a high-resolution water table and ground water flow path map to aid understanding of the relations between surface and ground water.
The Outdoor StreamLab, developed by SAFL and the National Center for Earth-surface Dynamics, is on the banks of the Mississippi River in downtown Minneapolis. According to Fotis Sotiropoulos, PhD, SAFL director, the lab will allow researchers to explore how ecosystems relate to flow dynamics.
The lab features a 130-foot-long Riparian Basin and a 430-foot-long Riverine Corridor. Within these two basins, researchers can control discharge, water velocity, bed and floodplain substrate, channel morphology, streambank stabilization, and vegetation.
The facility uses water from the Mississippi River to produce a large range of flow rates, including overbank floods. Dams and bridge piers placed within the Outdoor StreamLab allow study of dynamic human-river interactions.
Instruments to be installed include:
- – Acoustic and laser Doppler velocimetry probes;
– Surface particle image velocimetry;
– Digital single-lens reflex cameras;
– Laser and sonar scanners for bed topography and surface elevation;
– Water quality sondes (a package of instruments used to measure a number of variables in the water column);
– Water elevation loggers;
– Radio frequency identification system;
– Sediment feed;
– Sediment recirculation;
– Bedload and suspended load samplers; and
– Computer-controlled valves and weirs.
Rock anchor study points to inadequate corrosion protection
Prestressed rock anchors that were installed 12 or more years ago may not be adequately protected against corrosion, says Donald A. Bruce, PhD, president of Geosystems L.P. This conclusion is drawn from Phase 2 of the National Research Program on Rock Anchors for Dams, conducted by Bruce and John S. Wolfhope, principal with Freese and Nichols Inc. The program aims to produce a definitive and detailed list of all North American dam anchor projects, trace the evolution of practice, and project the market for post-tensioned anchors on large dams and hydro facilities.
Bruce and Wolfhope studied more than 400 case histories and 230 technical papers on practices related to rock anchors in dams in North America. The anchoring projects studied were completed from 1968 to 2004.
Because virtually every rock anchor installed is regarded as permanent, corrosion protection is a vital part of anchor design and construction, Bruce says.
In 1996, the Post Tensioning Institute updated its recommendation document for these anchors. The document identified two classes of protection (Class I and II). Class I, also called an encapsulated tendon, called for installing a steel pipe trumpet at the anchor head to prevent water from penetrating behind the anchor plate and covering the anchor head if it is exposed; protecting the unbonded length with a grease-filled sheath, a grout-filled sheath, or epoxy for fully bonded anchors; and using either grout-filled encapsulation or epoxy for the tendon bond length. Class II, also called a grout-protected tendon, called for the trumpet and cover for the anchor head; a grease-filled sheath of heat shrink sleeve for the unbonded length; and grout for the tendon bond length.
Changes have since been made to refine Class I protection. Today, installing a permanent anchor in a dam without Class I protection is not only impermissible but unthinkable, Bruce says.
Anchors installed with bare steel (wire or strand) up until the mid-1990s often cannot be load tested, Bruce says. As a result of this study of rock anchors, the conservative view is to assume that bare steel anchors installed before the mid-1990s are of questionable and indeterminable value and therefore should be replaced, he says.