Browsing by Author "Ellis, Christopher R."

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Density Current Instrusions in an Ice-Covered Urban Lake
(St. Anthony Falls Laboratory, 1997-03) Ellis, Christopher R.; Champlin, Jerry; Stefan, Heinz G.
Evidence is presented that snowmelt runoff from an urban watershed can produce density current intrusions (underflows) in a lake. Several episodes of density current intrusions are documented. Water temperatures and salinities measured near the bottom of a 10m deep Minneapolis lake during the late winter warming periods in 1989, 1990, 1991, and 1995 show significant rapid changes which are correlated with observed higher air temperatures and snowmelt runoff. The snowmelt runoff entering this particular lake (Ryan Lake) has increased electrical conductivity, salinity, and density. The source of the salinity is the salt spread on urban streets in the winter. Heating of littoral waters in spring may also contribute to the occurrence of the sinking flows, but is clearly not the only cause.
Density Current Instrusions in an Ice-Covered Urban Lake
(St. Anthony Falls Laboratory, 1997-03) Ellis, Christopher R.; Champlin, Jerry; Stefan, Heinz G.
Evidence is presented that snowmelt runoff from an urban watershed can produce density current intrusions (underflows) in a lake. Several episodes of density current intrusions are documented. Water temperatures and salinities measured near the bottom of a 10m deep Minneapolis lake during the late winter warming periods in 1989, 1990, 1991, and 1995 show significant rapid changes which are correlated with observed higher air temperatures and snowmelt runoff. The snowmelt runoff entering this particular lake (Ryan Lake) has increased electrical conductivity, salinity, and density. The source of the salinity is the salt spread on urban streets in the winter. Heating of littoral waters in spring may also contribute to the occurrence of the sinking flows, but is clearly not the only cause.
Dissolved Oxygen Demand at the Sediment-Water Interface in Monongalia Lake, Minnesota
(St. Anthony Falls Laboratory, 2002-10) Wang, Hong; Hondzo, Miki; Ellis, Christopher R.
The objective of this study is to determine the sediment oxygen demand in Monongalia Lake. The measurements will be utilized in designing a cost~effective aeration system at the New London Mill Ponds. The activities outlined below were conducted at the Saint Anthony Falls Laboratory, University of Minnesota: 1.) Determining the chemical composition of sediments at the sediment~water interface; 2.) Sampling 3~5 sediment cores in the field at representative locations within the New London Mill Pond/lower Monongalia Lake area; 3.) Determining the Sediment Oxygen Demand (SOD) of core samples using appropriate techniques under controlled laboratory conditions; 4.) Providing summary information to be used by another investigator for a cost-effective aeration design at the New London Mill Pond.
Fairview Riverside Medical Center Helistop, Minneapolis, Minnesota: Design and Operational Issues
(St. Anthony Falls Hydraulic Laboratory, 1995-06) Farell, Cesar; Sitheeq, M. Mohamed; Ellis, Christopher R.; Voigt, Richard L. Jr.
An analysis of wind conditions and aerodynamic design for the rooftop helideck of the Fairview Riverside Medical Center, Minneapolis, Minnesota, is presented, based on an extensive literature search and the examination of current Federal Aviation Administration and Civil Aviation Authority (United Kingdom) guidelines. The following points are examined: pilot comments following the opening of the facility; the advisability of. a model study; the need for field wind measurements; the configuration of the helideck, including its location on the rooftop, dimensions, and the size of the air gap under it; and the effects of rotor downwash and temperature on helicopter power and lift. Recommendations for site measurement of wind characteristics and additional future work are given.
Field Testing of a Winter Lake Aeration System
(St. Anthony Falls Hydraulic Laboratory, 1991-06) Ellis, Christopher R.; Stefan, Heinz G.
Conventional aeration of winterkill lakes results in lDlxmg. of the water column and open water in the ice cover. A non-mixing winter lake aeration system has been designed and field tested that can maintain water temperature stratification in the lake and not create open water. The performance of a cascade aerator was evaluated for which the design discharge and dissolved oxygen input rate were 85 lis and 70 kg/d, respectively, Unusually high levels of dissolved oxygen due to photosynthetic productivity under the ice-cover were also observed and are reported.
Heating and Cooling of a Shallow Bay in Eau Galle Reservoir: Field Measurements and Interpretation
(St. Anthony Falls Hydraulic Laboratory, 1989-10) Silver, Craig A,; Ellis, Christopher R.; Stefan, Heinz G.
Water quality concerns associated with the distribution of nutrients in lakes and reservoirs make information on naturally occurring processes, which affect water movement, of significant value. These processes can be driven by wind, rain, solar radiation, surface cooling, photosynthetic activity, ground water intrusion and Coriolis forces. This study focuses on the diurnal effects of radiative heating and convective surface cooling as the driving forces of change in the water temperature profiles. It has been shown that the horizontal temperature gradients caused by the heating and cooling of littoral waters, and the density differences associated with these temperature gradients, cause horizontal and vertical exchange of water within the littoral and adjacent profundal regions (Stefan, Horsch and Barko, 1989).
A Hydraulic Model Study of Navigation Improvement in the Upstream Approach to Locks and Dam No. 2, Mississippi River
(St. Anthony Falls Hydraulic Laboratory, 1988-10) Groethe, Jon; Ellis, Christopher R.; Stefan, Heinz G.
Locks and Dam No. 2 are located on the Mississippi River, 1.4 miles above Hastings, Minnesota, and 26 miles south of St. Paul, Minnesota. The structures are 815.2 river miles above the mouth of the Ohio River, 32.4 river miles below Locks and Dam No.1, and 17.3 river miles above Locks and Dam No.3. Locks and Dam No. 2 were put into operation in 1931 as part of the Army Corps of Engineers Mississippi River 9-foot channel navigation project. Today they consist of twenty 30 ft tainter gates and two locks on the southwest side of the river. The riverward lock is presently non-operational.
Hydraulic Model Study of the Blue River Dam Power Plant, Penstock, and Outlet Works
(St. Anthony Falls Laboratory, 1994-07) Voigt, Richard L.; Erickson, Benjamin; Ellis, Christopher R.
The Stone and Webster Engineering Corporation (S&W) contracted with St. Anthony Falls Hydraulic Laboratory (SAFHL) to construct and test a physical hydraulic model of a modified stilling basin for the Blue River Dam Power Plant Project outlet works. This project was designed by Stone and Webster for the Eugene Water and Electric Board. Modification to the stilling basin was necessary to accommodate changes in the design of the outlet structure necessitated by the installation of hydroelectric power generating turbines. The basin is presently owned and operated as a flood control structure by the U.S. Army Corps of Engineers (COE). The facility is operated according to COE procedures within the general constraints of a reservoir water surface level of maximum 1357 ft MSL and minimum 1180 ft MSL, and between the minimum and maximum flows of 50 cis to 8400 cfs, respectively. Flow exiting the reservoir is controlled through gates located at the upstream end of a 2000 it long 18.5 diameter conduit. The downstream end of the conduit concludes in an open channel outfall into the existing stilling basin. The design scheme for the hydro facility involved modifying the outlet works to incorporate a multiple bay gated outlet structure and a bifurcation leading to the powerhouse. Modifications included pressurization of the penstock and outlet works necessitated by the combined usage of the flow conduit for both hydropower and flood discharge. The objective of the study was to perform comparative testing of the existing outlet works stilling basin and the proposed design. In this effort, the study evolved into five distinct phases of testing. The test results are summarized according to phases with the reason for and objectives of the next phase outlined in the conclusion of each existing phase. A summary of the various phases is as follows:
Hydro-aesthetic improvement of St. Anthony Falls spillway at low flow
(1986-08) Stefan, Heinz G.; Ellis, Christopher R.; Johnson, Thomas R.
The possible expansion of hydropower development at St. Anthony Falls on the Mississippi River within the City of Minneapolis is likely to generate questions on the future appearance of the St. Anthony Falls spillway when most of the riverflow is routed through the existing powerplant and a projected additional power station. In particular, it may be asked how the aesthetics of the St. Anthony Falls spillway can be enhanced when only a small (minimum) flow is discharged over the spillway. It is anticipated that minimum flow spillway discharge will occur for 10 months in an average year when the proposed hydropower facility becomes operational. To study this particular question, an experimental study was conducted at St. Anthony Falls Hydraulic Laboratory and small flow deflectors which can be attached to the spillway surface and generate a "roostertail-like" spray were devised to make the appearance of the spillway more pleasing. The methods used in the study and the recommended design modifications are described in this report. It was not the intent of this study to determine what the minimum flow over the spillway should be, but rather to determine the best aesthetic effects on the spillway that can be accomplished at a low flow.
Investigation of the Use of Air Injection to Mitigate Cavitation Erosion
(St. Anthony Falls Laboratory, 1993-09) Arndt, Roger E. A.; Paul, Saurav; Ellis, Christopher R.
This project was initiated as part of a new research and development focus to improve hydropower generation. One aspect of the problem is severe cavitation erosion which is experienced when hydroturbines are operated at best power and in spinning reserve. Air injection has been used successfully to minimize or eliminate cavitation erosion in other applications. Thus, an investigation was initiated to determine whether or not air injection would be an effective solution for turbine erosion problems. A specially instrumented hydrofoil of elliptic planform ·and a NACA 0015 cross section was tested at flow velocities up to 20 m s·I, at various values of cavitation index. Pitting rate was not measured directly but was inferred from direct measurement of impulsive pressures on the surface of the hydrofoil and by monitoring accelerometers mounted at the base of the hydrofoil. Cavitation noise was also measured by a hydrophone positioned in the water tunnel test section. Air was injected through small holes in the leading edge of the foil. Air injection was found to be very effective in minimizing erosion as inferred from all three cavitation erosion detection techniques.
Navigation Conditions and Flood Conveyance at Locks and Dam No. 2, Mississippi River, Before and After Construction of a Proposed Hydropower Plant: Hydraulic Model Investigations
(St. Anthony Falls Hydraulic Laboratory, 1987-10) Ellis, Christopher R.; Stefan, Heinz G.
Locks and Dam No. 2 are located on the Mississippi River, 1.4 miles above Hastings, Minnesota, and 26 miles south of St. Paul, Minnesota. The structure is 815.2 river miles above the mouth of the Ohio River, 32.4 river miles below Locks and Dam No.1, and 17.3 river miles above Locks and Dam No.3. Locks and Dam No. 2 were put into operation in 1931 as part of the Army Corps of Engineers Mississippi River 9-foot channel navigation project. At that time they consisted of twenty 30 ft tainter gates and a single lock on the southwest side of the river. A second lock, landward of the first, was placed into operation in 1948. The original riverward lock is today non-operational.
Powerhouse Approach Flow Study for Mississippi River Lock and Dam No. 2 Hydrowpower Project
(St. Anthony Falls Hydraulic Laboratory, 1987-05) Ellis, Christopher R.; Stefan, Heinz G.
A 5 MW hydroelectric generating facility is currently under construction on the Mississippi River at Lock and Dam No. 2 near Hastings, Minnesota. As part of its licensing agreement, the City of Hastings was required to have a model study done to ascertain that the impact of the power plant on navigation into and out of the lock and on scour potential of the new faci1ilty would be negligible or acceptable. The model study was conducted at the St. Anthony Falls Hydraulic Laboratory, University of Minnesota, Minneapolis, Minnesota. For that study, a 1:72 scale fixed bed model was constructed of a river reach extending 1-1/3 miles upstream and 2/3 mile downstream of the dam. Upon completion of the tests required for the navigation study, it was decided that the model would further be used to study some aspects of the powerhouse approach flow.
Pressure Loss Coefficients of 6, 8 and 10-inch Steel Pipe Fittings
(St. Anthony Falls Laboratory, 2005-02) Ding, Chengwei; Carlson, Luke; Ellis, Christopher R.; Mohseni, Omid
The scope of this study includes the testing of 6, 8 and 10-inch wrought steel fittings with flowing water to determine their head loss coefficient values. The fittings comprise long elbows, reducing and expansion elbows, Tees, reducing Tees, concentric reducers and expansions. Sixty fittings from seven manufacturers (four manufacturers per fitting) were tested at specified ranges of flow velocities to determine their head loss coefficients. In addition, an uncertainty analysis was conducted to determine the errors associated with the test set-up, the instrumentation, and the procedures used for these tests. The head loss coefficients of the fittings and their ranges are presented in this report as a function of upstream flow velocity and the Reynolds number. The results of the study show that the K-value of long elbows is smallest for larger pipe fittings and increases as the pipe fitting size decreases. For branching flows in Tees, the K-value of the straight leg is very similar to those in reducing Tees. However, for branching flows in reducing Tees, the K-value of the branching leg varies with size and the percent reduction in flow area. The K-values of reducers and expansions show a weak dependence on upstream velocity. They are dependent on both the fitting size, and the percent reduction and expansion of the flow area.
StreamLab06: Overview of Experiments, Instrumentation, and Data collection
(St. Anthony Falls Laboratory, 2010-11) Marr, Jeff; Wilcock, Peter; Hondzo, Miki; Foufoula-Georgiou, Efi; Johnson, Sarah; Hill, Craig; Leonardson, Rebecca; Nelson, Peter; Venditti, Jeremy; O'Connor, Ben; Ellis, Christopher R.; Mullin, James; Jefferson, Anne; Clark, Jeff
This report summarizes the StreamLab06 experimental research program conducted in the St. Anthony Falls Laboratory (SAFL) Main Channel facility from April through October 2006. The experiments were funded through the National Center for Earth-surface Dynamics and involved a host of researchers, graduate students, visitors, and undergraduate students. The experiments were organized into seven phases of work. The first two phases of the project involved testing of conventional and surrogate bedload monitoring technologies (Marr et. al. 2007). The last five phases involved interdisciplinary research of sediment transport and ecohydraulics. This report focuses on the later phases of the project and does not include the bedload monitoring technologies. This report contains information on the organization of the experiments, the methodologies and protocols used to collect data, the types of data collected, data structure and format, and information on data storage and access.
University of Minnesota's Health Science Complex Wind Measurement Program
(St. Anthony Falls Hydraulic Laboratory, 1994-12) Ellis, Christopher R.; Farll, Cesar
Field measurements of wind velocity and direction carried out at the University of Minnesota Health Science Complex from July 1 to November 30, 1994, are reported. Two anemometers and one wind direction vane were used in the measurements, One anemometer was located outside the Unit B/C door, 4.3 m above the sidewalk and 0.5 m out from the wall. The other anemometer and a wind direction vane were installed atop the north-west corner of the Unit A building to provide information on the wind conditions above the buildings. Conditional sampling using the ground level anemometer to provide minimum threshold wind speeds was used to identify critical wind directions.
Wind Energy Feasibility and Energy Education Project Lower Sioux Community
(St. Anthony Falls Laboratory, 1997-07-24) Farell, Cesar; Ellis, Christopher R.
The results of wind speed and direction measurements carried out in the Lower Sioux Community during the twelve~month period from November 1, 1995, to October 31, 1996, are reported. The measurement were performed using six wind anemometers and six wind direction vanes installed at four sites in the community. The data presented include the monthly averages of the semi~hour1y wind speeds and of their cubes, monthly wind roses, the probability distributions of the wind speeds and the parameters of Wei bull distributions fitted to them, turbulence intensity data, and total energy roses for each month. The data are presented so as to streamline a comparison with wind energy data at other area sites where comparable records may be available. Possible sites and methodology for such a comparison and errors which may arise in a potential extrapolation of the twelve-month record to longer time periods are discussed.

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