Technical Papers

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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, Kesavarao
The 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.
Air Bubble Resorption
(St. Anthony Falls Hydraulic Laboratory, 1949-08) Silberman, Edward
This 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.
A Capacitive Wave Profile Recorder
(St. Anthony Falls Hydraulic Laboratory, 1952-10) Killen, John M.
Research studies at the St. Anthony Falls Hydraulic Laboratory necessitated the development of a device for measuring and recording the profile of surface waves. The initial phase of these studies involved waves with periods ranging from 1/3 to 1 sec and with heights ranging from 1/2 to 3 inches. Existing methods of measuring and recording the profiles of these waves were considered to be not entirely satisfactory. A method has been developed whereby wave heights are measured electrically with a recording oscillograph; the deflections correspond to the depths of submergence of an insulated wire into the water. This insulated wire acts as a small capacitor whose capacity varies directly with the wetted area of the wire. The system has a linear calibration. Thus, accurate and continuous wave profiles can be recorded. Hysteresis effects due to surface tension are about 0.003 ft. A sensitivity up to 1/2 cm pen deflection per O.OO1-ft variation in water level is possible. The method may be used for greater wave heights, however some adjustment in oscillator may be required in extreme instances.
Capacity of Box Inlet Drop Spillways Under Free and Submerged Flow Conditions
(St. Anthony Falls Hydraulic Laboratory, 1951-01) Blaisdell, Fred W.; Donnelly, Charles A.
The box inlet drop spillway is defined as a rectangular box open at the top and at the downstream end. The spillway is shown in Figure 1. Storm runoff is directed to the box by dikes and headwalls, enters over the upstream end and two sides, and leaves through the open downstream end. An outlet structure is attached to the downstream end of the box. The long crest of the box inlet permits large flows to pass over it with relatively low heads, yet the width of the spillway need be no greater than that of the exit channel. the drop spillway has been extensively used as a gully control structure where it is necessary to drop water from as short a distance as 2 feet to as much as 12 feet. In more recent years it has also been used in drainage ditches where it functions as a title outlet and means of dropping excess surface water into the ditch. For the sake of economy, auxiliary vegetated spillways are sometimes provided to pass part of the runoff from the larger storms and to permit the use of smaller mechanical spillway. In order to prevent scour of the drainage ditch banks the elevations of the vegetated spillways are adjusted so no water will pass over them until the downstream drainage ditch flows back full. In other words, the mechanical spillway must have sufficient capacity to fill the ditch completely before any flow passes over the vegetated spillway. Under these conditions the high downstream water level will likely submerge the spillway and reduce its flow. After the vegetated spillways come into operation, the downstream level rises still further and submergence of the mechanical spillway becomes greater. Spillways designed in this manner are known as the "island dam" type because they can be completely surrounded by water during flood periods. The necessity for these studies to determine the capacity of box inlet drop spillways under submerged flow conditions thus becomes apparent.
Design Studies for a Closed-Jet Water Tunnel
(St. Anthony Falls Hydraulic Laboratory, 1951-08) Ripken, John F.
A variable-pressure water tunnel, which is a testing facility analogous to a wind tunnel, is a useful tool in the study of cavitation or hydrodynamic characteristics of underwater bodies. This paper includes general, selective, hydrodynamic design studies for the construction of a large closed-jet water tunnel, together with experimental model test data and design analysis of a specific selection of flow components. Each flow component is critically examined with regard to its influence on test section flow quality, cavitation, susceptibility, and energy head loss. Included are studies of the test section, contraction, diffuser, vaned elbows, and pump. Presentation in chapters devoted to single flow components simplifies the treatment and increases adaptability of the findings to conduit design problems other than water tunnels.
A Dynamometer for the Two-Dimensional, Free-Jet Water Tunnel Test Section
(St. Anthony Falls Hydraulic Laboratory, 1962-06) Silberman, E.; Daugherty, R. H.
This paper describes a strain-gage type dynamometer designed for use in the two-dimensional test section of the free-jet water tunnel. This dynamometer replaces one originally instaled in the tunnel and described in an earlier paper [1].
An Electrical Method for Measuring Air Concentration in Flowing Air-Water Mixtures
(St. Anthony Falls Hydraulic Laboratory, 1950-03) Lamb, Owen P.; Killen, John M.
An electrical instrument has been developed to measure the air concentration in flowing air-water mixtures as part of an investigation of the mechanism by which atmospheric air is entrained in flowing water. The theory, development, and verification of this instrument are described in this report. The instrument is shown in Figs. 6c and 7, and the electrical circuit is shown in Fig. 9b. The electrical measurement of air concentration was chosen after examining possible mechanical, chemical, and magnetic methods. The method consists basically of a measurement of the difference between the conductivity of a mixture of air and water and conductivity of water alone. A mechanical strut supporting a pair of electrical probes has been combined with the electrical circuit in such a manner that air-concentration measurements may be made, not at a point, but at least in a small region of the flow. With this instrument it is now possible to traverse the flow cross section both vertically and laterally and to obtain the distribution of air in the flowing mixture. The relation between the instrument readings and air-concentration values are determined theoretically and the instrument is direct reading. by checking the results of the electrical method against a direct mechanical sampling method, it has been determined that the values of air concentration computed form theoretical conditions alone were sufficiently accurate for experimental work without further calibration. The instrument is now designed for application in an experimental laboratory channel, but with the use of a more rugged strut and supporting structure the method could be applied equally well in large flumes and spillways.
Experimental and Analytical Studies of the Longitudinal Motions of a Tandem Dihedral Hydrofoil Craft in Regular Waves
(St. Anthony Falls Hydraulic Laboratory, 1960-04) Wetzel, J. M.
Experimental investigations were conducted with a tandem surface-piercing hydrofoil configuration free to heave and pitch in regular waves. Towing velocities of 5 and 10 fps were used in head and following seas. Tests at the lower velocity were conducted to check data previously reported by Leehey and Steele; the agreement was satisfactory. The data were compared with nonlinear and linearized theory developed by Ogilvie for both quasi-steady and unsteady conditions. The oscillatory heave, pitch, and phase relationships in general agreed well with solutions based on the linearized equations. Consideration of unsteady effects in most cases improved the correlation between theory and experiment. The primary effect of the nonlinearities was in the existence of steady components of heave and pitch. The theoretical components were verified qualitatively by the experimental results.
Experimental Studies of Cavitation Noise in a Free-Jet Tunnel
(St. Anthony Falls Hydraulic Laboratory, 1961-07) Song, C. S.; Silberman, Edward
The present paper summarizes the results of experimental studies on cavitation noise generated in the free-jet tunnel at St. Anthony Falls Hydraulic Laboratory in the period October 1960 to June 1961. Two-dimensional test bodies of different shapes, such as a circular cylinder, wedge, and a Tulin-Burkhart hydrofoil were tested. Various types of cavitating flows, namely, transient cavities, steady-state cavities, and non-stationary cavities were covered. Special attention was given to the effect of ventilation on the intensity of cavitation noise. Effects of body size and the presence of a solid boundary were also investigated.
Experimental Studies of Pneumatic and Hydraulic Break Waters
(St. Anthony Falls Hydraulic Laboratory, 1959-08) Straub, Lorenz G.; Bowers, C. E.; Tarapore, Zal S.
Experimental studies were conducted on two similar models of both pneumatic and hydraulic breakwaters, having a length ratio of 4.5:1. Tests of the pneumatic system indicated that the horsepower requirements for a given percentage of attenuation depended only on the wave length, the submergence of the manifold, and the depth of water. Multiple-manifold breakwaters with different spacings between manifolds were tried and found to be of no particular advantage over the one-manifold system. An intermittent bubbler device was also tested very briefly, showing very little difference from the one-manifold data. Tests of the hydraulic system indicated that power requirements varied with wave steepness as well as wave length. Orifice area was a very important parameter as this affected the discharge requirements and the required size of supply piping. The power requirements of the pneumatic system are somewhat less than the hydraulic for average values of wave steepness, but the maximum attenuation achieved was less than the hydraulic.
An Experimental Study of Flexible Floating Breakwaters
(St. Anthony Falls Hydraulic Laboratory, 1960-10) Ripken, John F.
Earlier studies had indicated that moored flexible bags positioned slightly below the water surface and filled with a liquid or a gas could attenuate the height of gravity water waves. The studies reported herein describe large and small scale laboratory tests evaluating the attenuation effects and mooring forces for various bag configurations. A breakwater composed of a moored row of lean, floating cylindrical bags filled with water provided excellent wave attenuation with moderate mooring forces. This type of breakwater appeared suitable for practical development of temporary wave protection works. Submerged bags filled with air also provide good attenuation action but involved a substantial structural system for mooring.
Experiments on a Jet Flap in Supercavitating Flow
(St. Anthony Falls Hydraulic Laboratory, 1964-01) Silberman, Edward
Experiments on a fully-cavitated, flat-plate hydrofoil equipped with a pure jet flap were conducted in the free-jet water tunnel at the St. Anthony Falls Hydraulic Laboratory. The foils were of 2-in. and 2.75-in. chord and were tested in 6-in., 10-in., and l4-in. wide free jets. Data were obtained on the increments in lift, drag, and moment coefficients and on the shift in center of pressure as a function of jet momentum coefficient C_j, cavitation number, and other variables.
Field Survey on Aquatic Environment and "Ayu" Habitat in Urban River
(2006) Higashino, Makoto; Takami, Tohru; Onitsuka, Kouki; Akiyama, Juichiro; Nagaya, Takayuki; Shiraishi, Yoshiki; Ohtsuka, Noriharu
Field measurements were performed to investigate "Ayu" habitat in the Gokase (Ose) river in Miyazaki. "Ayu" is famous and popular, and hence, one of the most important fish in Japan. There has been substantial river engineering for flood control, e.g. dredging of bed, especially near urban areas. This engineering work can damage the fish habitat. In order to protect "Ayu" habitat, it is necessary to predict how the fish respond to habitat damage in the river, i.e. an environmental assessment. The water quality e.g. DO (Dissolved Oxygen), BOD, COD, SS, the temperature, and the discharge are all significant for the fish habitat. The abundance of algae attached to the surface of bed material, e.g. stones, is also significant because it is a food source for the fish. The water quality, the temperature, and the velocity of flow were measured at the several points in one of the artificial spawning beds "Ogura-shita rapid" in the Ose river. Material attached to the river bed was collected, and TR (Total Residue) and Chl.a (Chlorophyll.a) were smaller in summer, and larger in winter, which is different from what is generally expected. The growth rate of algae in the Ose river was found to depend on the velocity of flow, i.e. the value of Chl.a was increased as the velocity was increased, became the largest at a velocity of 0.4 to 0.5m/s, and decreased with increasing velocity above 0.5m/s.
Headrace Design Studies for the Jim Falls Hydro-Redevelopment Project
(St. Anthony Falls Laboratory, 1987-08) Stefan, Heinz G.; Voigt, Richard L. Jr.; Lindblom, Karen L. C.; Ainsworth, Bruce; Colgan, Patrick
The 48 MW Jim Falls Hydropower Redevelopment project on the Chippewa River, Wisconsin, required extensive model studies to facilitate the debris sluicing and to prevent intermittent vortex formation in front of the powerhouse intake. Debris, consisting mainly of natural materials from a forested and agricultural watershed, had to be directed to a gated spillway adjacent to the powerhouse (Fig. 1). To accomplish that goal, the surface circulation in the headwater pool had to be reversed. Vortices formed preferentially at two locations near the ends of the powerhouse, and were highly unstable in space and time. The highly irregular headrace geometry, in terms of width and depth, was found to be the cause of the undesirable flow features. A series of headrace modifications resulting in a more symmetrical approach channel configuration provided a debris flow pattern away from the powerhouse intake, and reduced frequency and strength of vortex formation to acceptable levels. A description of effective and ineffective design changes will be given.
Hydraulic Data Comparison of Concrete and Corrugated Metal Culvert Pipes
(St. Anthony Falls Hydraulic Laboratory, 1950-07) Straub, Lorenz G.; Morris, Henry M.
Full-scale tests were conducted at the St. Anthony Falls Hydraulic Laboratory of the University of Minnesota primarily for the purpose of obtaining pipe friction and entrance loss coefficients for concrete and corrugated metal culvert pipes, which would be more accurate and dependable than those currently recommended in culvert design literature. Comparison of these test data is presented in this paper and recommendations are given for design values of the coefficients under various flow conditions. The experimental studies were made on new culverts, all of which were installed and maintained with excellent alignment. A high degree of accuracy was possible in these tests for all of the culverts. Sizes up to 3 ft in diameter were investigated. Analytical studies were made of the data obtained from the experimental observations which were significant to basic pipe flow theory where systematic form roughness and large diameters come into consideration.
Hydraulic Design of the Box Inlet Drop Spillway
(St. Anthony Falls Hydraulic Laboratory, 1951-01) Blaisdell, Fred W.; Donnelly, Charles A.
This paper contains sufficient information to permit the complete hydraulic design of a box inlet drop spillway and explains briefly the various factors that influence the design. Its four major sections deal with the free flow capacity, the outlet design, the submerged flow capacity, and the utilization of the preceding information in the design of box inlet drop spillways. The box inlet drop spillway may be described as a rectangular box open at the top and at the downstream end. The spillway is shown in the Frontispiece and in Figure 1. Storm runoff is directed to the box by dikes and headwalls, enters over the upstream end and two sides, and leaves through the open downstream end. An outlet structure is attached to the downstream end of the box. The long crest of the box inlet permits large flows to pass over it with relatively low heads, yet the width of the spillway need be no greater than that of the exit channel.
Hydraulic Model Studies for Whiting Field Naval Air Station
(St. Anthony Falls Hydraulic Laboratory, 1950-01) Bowers, Charles E.
The Naval Auxiliary Air Station, Whiting Field, is to have a stormwater disposal system in which the existing pipes and terraces under and in the vicinity of the runways and building area will discharge into paved trapezoidal open channels. Many of the channels join other channels as they pass down the sides of the plateau on which the airfield is located. The grades of the main channels and of many of the lateral channels are such that water flows at supercritical velocities or at velocities greater than that of a gravity wave. The difficulties anticipated in joining two streams of water, one or more of which is flowing at supercritical velocities, led to the request for model studies of several of the channel junctions. The primary objectives in the present study include (1) the development of junction designs for specified operating conditions which would result in reasonably smooth flow downstream of the junction and (2) the determination of the necessary wall heights in the vicinity of the junction. Economic and structural considerations involved in the junction designs were considered in the final selection. Dependent upon the junction design, the discharges, velocities, and related phenomena of the flow in the vicinity of the junction, a hydraulic jump may form in one or both of the inlet channels. This may necessitate a large increase in the height of the sidewalls in the vicinity of the junction. On the other hand, if the flow passes through the junction at velocities greater than the critical, standing waves may form which have a height greatly in excess of a normal freeboard and which continue to oscillate back and forth across the channel for a considerable distance downstream from the junction before being damped by frictional forces. These standing waves necessitate higher sidewalls not only in the vicinity of the junction but for a considerable distance downstream. As available information on junctions of this type is almost nonexistent, it was necessary to resort to model studies in order to determine the flow conditions and the minimum sidewall heights. Two general types of junctions were studied. One type consists of the junction of two large channels in which the lateral and inlet main have comparable discharges. The other type, called terrace outlets, consists of a junction between a main channel and a terrace channel having a relatively small discharge. The maximum discharge ranges from 380 to 960 cfs in the main channels and from 25 to 70 cfs in the terrace channels. The maximum velocity of flow encountered is approximately 30 fps.
Hydraulic Tests on Concrete Culvert Pipes
(St. Anthony Falls Hydraulic Laboratory, 1950-07) Straub, Lorenz G.; Morris, Henry M.
Included in an experimental program conducted at the St. Anthony Falls Hydraulic Laboratory of the University of Minnesota on full-scale culverts was a series of tests on concrete pipes up to 3 ft in diameter. The primary purpose of these tests was to obtain pipe friction and entrance loss coefficients which would be more accurate and dependable than those currently recommended in culvert design literature. the studies were begun in 1946. This paper is confined to a discussion of the concrete culvert test program and the results of the studies. The test series included three concrete culvert pipes, 18 inches, 24 inches, and 36 inches in diameter, respectively. Each pipe was 193 ft long and laid on a slope of 0.20 per cent, except that the 24-in. pipe was on a slope of 0.224 per cent. the pipes tested were all manufactured by the cast-and-vibrated process. Details of the pipe sections are shown on page 22. Friction and entrance loss coefficients were established for the culverts under the usual conditions of field operations: (a) Full flow with submerged inlet and outlet. (b) Part-full flow at uniform depth. The 18-in. and 36-in. diameter pipes were tested for each of the two types of flow with two different entrance conditions; namely, (a) pipe projecting 2 ft into the headwater pool, (b) pipe entrance flush with the headwall. The 24-in. pipe was tested with the projecting entrance only.
Hydraulic Tests on Corrugated Metal Culvert Pipes
(St. Anthony Falls Hydraulic Laboratory, 1950-07) Straub, Lorenz G.; Morris, Henry M.
Experimental studies on culverts conducted at the St. Anthony Falls Hydraulic Laboratory of the University of Minnesota, beginning in 1946, included several series of observations on commercial , corrugated metal culvert pipes, The primary purpose of these large-scale tests was to obtain pipe friction and entrance loss coefficients which would be more accurate and dependable than those currently recommended in culvert design literature. A previous paper in this series gives a discussion of the comparison with the results of parallel studies on concrete culverts. The present paper is confined to a discussion of the corrugated pipe culvert test program and an analysis of the results of the studies. Two types of corrugated metal culverts were tested, namely, the circular and the pipe arch types. In each case, threee different nominal diameter pipe sections were tested--18 in., 24 in., and 36 in., respectively--, making a total of six corrugated metal culverts in the test program. Each pipe was 193 ft long and laid on a slope of 0.20 per cent. For the pipe arch culverts, the identifying dimensions refer to the diameters of circular pipes having the same length of periphery. For example, the 36-in. pipe arch and the 36-in. circular culvert have equal perimeters although their heights, widths, and areas are unequal. Cross sections of the various pipes, with controlling dimensions, appear in Fig. 1. (Note that the corrugation height in each case is 1/2 in. and that all computations have been based on the inside section, that is on the minimum cross-sectional area.) Friction and entrance loss coefficients were established for the culverts under the usual conditions of field operation. With this objective in view, each pipe was tested for the following conditions: (a) Full flow with submerged inlet and outlet. (b) Part-full flow at uniform depth. For each flow condition, several values of head and discharge were used. In addition, five of the culverts were tested with two different entrance conditions; namely, (a) Pipe projecting 2 ft into the headwater pool. (b) Pipe entrance flush with headwall.
Hydraulics of Closed Conduit Spillways Part 1. Theory and Its Application
(St. Anthony Falls Hydraulic Laboratory, 1952-01) Blaisdell, Fred W.
The closed conduit spillway is any conduit having a closed cross section through which water is spilled. The inlet and outlet may be of any type. The barrel may be of any size or shape and may flow either full or partly full. Also, the barrel may be on any slope. This broad definition includes the smallest culvert as well as the largest morning glory spillway. The basic theory of the flow is the same for each of the many forms which the spillway may take. This paper discusses the control of the flow through closed conduit spillways by weirs, the barrel exit, tailwater, pipe, orifice, and short tube, since each of these controls may govern, at some time or other, the rate of flow through the spillway. The effect of these various controls on the performance of the spillway is explained. A means of developing a composite head-discharge curve is given. Pressures within the closed conduit spillway must sometimes be determined, so the methods for this determination are presented. A selected bibliography useful to the understanding and for the design of closed conduit spillways concludes this technical paper.

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