St. Anthony Falls Laboratory
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The St. Anthony Falls Laboratory (SAFL) was designed and built in the 1930s under the direction of Lorenz G. Straub with funds from the Works Progress Administration and the University of Minnesota. The building was dedicated on November 17, 1938 and the Laboratory began its work in hydraulic and river engineering research as part of the Department of Civil Engineering.
Today SAFL is an interdisciplinary fluid mechanics research and research training facility of the College of Science and Engineering. Research focuses on environmental, energy, and health challenges.
Current information about SAFL and its programs is at http://www.safl.umn.edu.
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Item 1:27 Scale Physical Model of Spillway Air Ramp Alternatives for the 15 de Septiembre Project(1993-07) Ramanathan, V.; Voigt, Richard L. Jr.Item Abrupt Transition from a Circular Pipe to a Rectangular Open Channel(St. Anthony Falls Hydraulic Laboratory, 1969-07) Blaisdell, Fred W.; Donnelly, Charles A.; Yalamanchili, KesavaraoThe development of criteria and a generalized procedure for the design of an abrupt transition from a circular pipe to a rectangular open channel are presented. The rectangular channel must be 1.0 pipe diameters wide. Wider channels cause high waves which reflect from the channel sidewalls, may overtop the sidewalls, and produce severe disturbances in the channel. To permit the pipe to expand, the channel may be widened for a distance not exceeding 0.5 pipe diameters downstream from the pipe exit, and the floor of the channel may be lowered. The equations developed describe the locations of the water surface elements to within an average of 0.11 pipe diameters of their correct locations. The maximum anticipated location error is +/- 1.4 pipe diameters. The equations for the envelope curves covering the crests of the sidewall waves, which determine the channel sidewall height, provide an average freeboard of 0.08 pipe diameters and a maximum freeboard of 0.31 pipe diameters. When the envelope equations are used only 2 percent of the wall waves will overtop the sidewalls, the maximum overtopping being 0.04 pipe diameters. The average depth of flow-the depth at the wave nodes-is predicted by the equations to within a maximum deviation of +0.13 and -0.06 pipe diameters of the observed depths. The average depth at the nodes is predicted by the equations within 0.01 pipe diameters of the observed average depth.Item An Acoustic Study of Gaseous Micro-Bubbles In Boundary Layers and Propeller Wakes(St. Anthony Falls Hydraulic Laboratory, 1962-12) Ripken, John F.; Killen, John M.This report deals with exploratory tests to measure the nature of the free gas which occurs in natural water due to the dynamic disturbance of a ship. Acoustic attenuation measurements serve to show that micro gas bubbles are evolved from dissolved gases by the shear dynamics of a boundary layer and that the rate of evolution increases as some function of the intensity and duration of the disturbance and of the pressure, viscosity, and gas content of the water. The tests were conducted in the Laboratory, in large scale simulations of a ship's boundary layer and propeller, and in wakes of actual ship propeller's. These exploratory tests indicate the need for more extensive tests in sea water under a wide variety of naval operating conditions. Such tests are necessary to a better determination of the role that these bubbles play in cavitation and acoustic detection problems.Item Addendum To Final Memorandum Of July 1963: Calibration Of Spillway With Low Crest Blocks(St. Anthony Falls Hydraulic Laboratory, 1966-01) Anderson, Alvin G.This addendum reports the results of calibration tests on the partially completed Angat spillway. The study was based upon a memorandum by W. A. Waldorf, Harza Engineering Company, dated September 20, 1965.Item Air Bubble Resorption(St. Anthony Falls Hydraulic Laboratory, 1949-08) Silberman, EdwardThis paper describes an analysis and experiment directed at determining the laws governing the rate of solution of a gas bubble in turbulent liquid. The object of the research was to determine methods for resorbing air bubbles which have been freed from the water in a water tunnel. A basic equation governing the resorption process which has been developed and partially verified in the work is presented as Eq. (13) in the text. Useful approximate forms of this equation are given as Eqs. (14b) and (14d) in the text. The basic equation has led to several suggested methods for accomplishing resorption in water tunnel. These include: (1) a resorber method already developed at the California Institute of Technology[1]*; (2) a method in which air in solution in water would be completely replaced in the closed water tunnel circuit by another gas such as carbon dioxide; and (3) a method in which a lengthened return circuit would be combined with a fin-scale turbulence, introduced in the return circuit to hasten air bubble resorption while keeping the bubble from rising. The time required for resorption by any of these methods may be estimated from the basic equation.Item Air Entrainment in Flowing Water(St. Anthony Falls Hydraulic Laboratory, 1949-08) Lamb, Owen P.The physical entrainment of a gas by a liquid and the flow of gas-liquid mixtures are phenomena commonly encountered in engineering practice, but avoided or arbitrarily compensated for in theoretical considerations and in design analysis. The progress toward a satisfactory explanation of these phenomena has been hampered by a lack of accurate experimental observations of entrained flows and by the complexity of the theoretical analysis when certain of the physical forces can no longer be neglected.Item Air-Water Mixture Flow Through Orfices, Bends, and other Fittings in a Horizontal Pipe(St. Anthony Falls Hydraulic Laboratory, 1960-09) Silberman, EdwardIn planning piping systems for flow of gas-liquid mixtures, it is necessary to know something about the pressure and the pressure changes along the line. The pressure changes may be considered partly frictional and partly nonfrictional. Both of these mechanisms are active in mixture flows in straight, uniform pipes, and in fittings with gradual changes in cross section and/or alignment such as diffusers and bends. In fittings with abrupt changes in cross section, such as orifices, frictional losses are relatively small and pressure changes are largely the result of changes in kinetic energy and momentum. Furthermore, the flow pattern (that is, whether the flow be bubble, plug, annular, etc.) is dependent on the local pressure, other factors being constant, and it may be desirable to mow something about the flow pattern for use in heat transfer calculations, for example, and even for use in calculations for pressure drop in some fittings.Item All-Weather Ground Surface Temperature Simulation(St. Anthony Falls Laboratory, 2006-09) Herb, William R.; Janke, Ben; Mohseni, Omid; Stefan, Heinz G.Thermal pollution from urban runoff is considered to be a significant contributor to the degradation of coldwater ecosystems. Impervious surfaces (streets, parking lots and buildings) are characteristic of urban watersheds. A model for predicting temperature time series for dry and wet ground surfaces is described in this report. The model has been developed from basic principles. It is a portion of a larger project to develop a modeling tool to assess the impact of urban development on the temperature of coldwater streams. Heat transfer processes on impervious and pervious ground surfaces were investigated for both dry and wet weather periods. The principal goal of the effort was to formulate and test equations that quantify the heat fluxes across a ground surface before, during and after a rainfall event. These equations were combined with a numerical approximation of the 1-D unsteady heat diffusion equation to calculate temperature distributions in the ground beginning at the ground surface. Equations to predict the magnitude of the radiative, convective, conductive and evaporative heat fluxes at a dry or wet surface, using standard climate data as input, were developed. Plant canopies were included for surfaces covered by vegetation. The model can simulate the ground surface and subsurface temperatures continuously throughout a specified time period (e.g. a summer season) or for a single rainfall event. Ground temperatures have been successfully simulated for pavements, bare soil, short and tall grass, trees and two agricultural crops (corn and soybeans). The simulations were first run for different locations and different years as imposed by the availability of measured soil temperature and climate data. Data came from sites in Minnesota, Illinois and Vermont. To clarify the effect of different land uses on ground temperatures, the calibrated coefficients for each land use and the same soil coefficients were used to simulate surface temperatures for a single climate data set from St. Paul, MN (2004). Asphalt and concrete give the highest surface temperatures, as expected, while vegetated surfaces gave the lowest. Bare soil gives surface temperatures that lie between those for pavements and plant-covered surfaces. The soil temperature and moisture model appears to model surface temperatures of bare soil and pavement with RMSEs of 1 to 2°C, and surface temperatures of vegetation-covered surfaces with RMSEs of 1 to 3oC. The plant canopy model used in this study, based on the work of Best and Deardorff, provides an adequate approximation for the effect of vegetation on surface heat transfer, using only a few additional parameters compared to bare surfaces. While further simplifications of the model are possible, such simplifications do not reduce the number of required input parameters, and do not eliminate the need for estimating the seasonal variation of the vegetation density. A model for roof temperatures was also developed, based on the surface heat transfer formulations used for pavement. The model has been calibrated for both a commercial tar/gravel roof and a residential roof. Compared to pavement, the roof surface reach similarly high maximum temperatures, but reach lower minimum temperature at night cool due to their lower thermal mass.Item Alumni Channel (Fall 2005)(St. Anthony Falls Laboratory, 2005)Item Alumni Channel (Fall 2006)(St. Anthony Falls Laboratory, 2006)Item Alumni Channel (Fall 2007)(St. Anthony Falls Laboratory, 2007)Item Alumni Channel (Spring 2004)(St. Anthony Falls Laboratory, 2004)Item Alumni Channel (Spring 2005)(St. Anthony Falls Laboratory, 2005)Item Alumni Channel (Spring 2006)(St. Anthony Falls Laboratory, 2006)Item Alumni Channel (Spring 2007)(St. Anthony Falls Laboratory, 2007)Item Analysis and Simulation of Mixing of Stratified Layers or Reservoirs by Air Bubble Plumes(St. Anthony Falls Hydraulic Laboratory, 1990-12) Zic, Kresimir; Stefan, Heinz G.The goal of the research presented in this report is to analyze, understand, and simulate the flow field induced by a bubble plume in a lake or reservoir. This is useful and necessary for the design of lake or reservoir aeration and destratification projects. Three mathematical models were developed and laboratory experiments were performed. Experiments similar to the ones presented here are not available in the literature but were necessary to understand the governing physical processes and to verify the mathematical models. What makes these experiments unique, in comparison with other bubble plume measurements is the description of the entire flow field (not just the flow in vicinity of the bubble plume), the inclusion of stratified ambient water, and the evaluation of destrati:fication over time. The first. model developed is a modified version of a dynamic 1-D mathematical model originally formulated by Goossens[1979]. The improved model is based on the research described here and is linked to a general dynamic lake model MINLAKE. It is a tool useful for lake restoration projects, particularly for evaluation of different restoration techniques. The second model is also an integral model of a bubble plume. The flow field induced by an air bubble plume in stratified ambient water is presented in the general context of mixing mechanics of water jets and plumes. The third model is a 2-D numerical model that gives insight into the subregions of the flow field. The 2-D model solves the Reynolds' equations by using the buoyancy-extended version of the k-e model as a closure of the turbulent quantities. The effect of the bubbles in the fluid flow is modeled by imposing internal forces in the region where the air bubbles are present. A discussion of lake aeration as an oxygen transfer technique is beyond the scope of the research described herein.Item Analysis of a Hydroacoustic Gravity Flow Facility(St. Anthony Falls Laboratory, 1984-09) Arndt, Roger E.; Wetzel, Joseph M.; Bintz, David W.; Ripken, John F.Two preliminary designs of a hydroacoustic gravity flow facility have been developed for a Ship Silencing Laboratory, DTNSRDC, by Dr. George F. Wis1icenus. It was desired to attain a test section velocity of 60 fps for a 90 sec time period. As the facility will be used for acoustic measurements, cavitation-free flow is a necessity. After a test run has been completed, the water is returned by a pump in a separate line back to the head tank. To ma~imize usage of the facility, the recycling time between runs should be kept short. As part of the overall development program, the Laboratory has been asked to carry out some preliminary calculations on the proposed designs to further establish feasibility and to independently evaluate the designs. The calculations included an estimate of head loss in the system and an elementary transient analysis. An alternate configuration also has been suggested for consideration.Item Analysis of Flow Data from Miller Creek, Duluth, MN(St. Anthony Falls Hydraulic Laboratory, 2008-11) Herb, William R.; Stefan, Heinz G.This report summarizes an analysis of flow and precipitation data for Miller Creek, a trout stream in Duluth, MN, which was undertaken in support of the MPCA-mandated temperature TMDL. The main goals of this analysis were to determine the availability and quality of Miller Creek flow data and to characterize typical summer low flow conditions to be used in subsequent stream temperature analysis. Flow data from the three existing flow aging sites (lower, middle, upper) on Miller Creek were analyzed, along with precipitation data from the Duluth International Airport. The analyses of flow and precipitation data suggest that the flow data at the lower site are relatively consistent for all years, except 2007. Flow data from the middle site for the periods 1997-2003 and 2004-2007 have different character, with the 2004-2007 data from the middle site considered suspect. Flow data from the upper site (Kohl’s) in 1997 and 1998 appear reasonable, but a rating curve does not exist to translate stage data to flow for 2003 – 2007. Relationships between stream flows and precipitation have been established at weekly timescales and are reasonable (r2 = 0.70), but with RMSEs similar in magnitude to the mean flows. Based on 1997 and 1998 data, weekly-averaged flows at the middle and upper gaging sites are, on average, 92% and 77% of the lower site, respectively. This suggests that a large fraction of the flow in Miller Creek originates from the upper portion of the watershed, upstream of the Kohl’s site. A statistical analysis of five years of flow data from the Miller Creek lower site indicates that low flows in the range of 1 to 2 cfs are quite common at weekly time scales. Therefore a rainfall event of moderate magnitude may be expected to have a significant impact on stream flow and temperature at the lower site. Although the flow record is relatively short (5 years), the results of a frequency analysis suggest that weekly mean flows near zero are possible with a 10 year return period.Item Analysis of Flow through Sturgeon Lake and Backwater Channels of Mississippi River Pool No. 3 Near Red Wing, Minnesota(St. Anthony Falls Hydraulic Laboratory, 1977-04) Stefan, Heinz; Anderson, KeithFlow rates through Sturgeon Lake and backwater channels of the Mississippi River in the vicinity of the Prairie Island Nuclear power Generating Plant are determined as a function of total river flow and of wind direction and wind velocity, particularly for low flow conditions. The analysis is made in order to determine; (a) how much of the Sturgeon Lake flow is drawn into the cooling water intake of the plant, and (b) by how much plant effluent cooling water or blow down water is diluted by sturgeon Lake effluent before entering the Mississippi River. A channel network analysis including effects of wind stress on the water surface in addition to bed shear stress and local (minor) energy losses was made to provide the required information. Forty-three channel and channel segments were used to describe the entire system. The Sturgeon Lake/North Lake system was studied before the complete analysis was made. In the absence of wind, flow through Sturgeon Lake amounted to about 22 percent of total river flow. At low plant withdrawal rates and at zero wind, the flow through the backwater channel in front of the plant outlet (channel 42) was about 10 percent of total river flow. Winds from 5 to 30 mph had a very noticeable effect on flows through Sturgeon Lake, particularly when total river flows were less than 10,000 cfs. The analysis was made without consideration of stratification effects near the plant intake and outlet.Item Analysis of Stormwater Runoff Best Management Practices in Miller Creek, Duluth, MN(2021-01) Herb, William