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Browsing by Author "Blaisdell, Fred W."

Now showing 1 - 10 of 10
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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.
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    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.
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    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.
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    Hydraulic Model Studies for Whiting Field Naval Air Station, Part I - Part IV
    (St. Anthony Falls Hydraulic Laboratory, 1950-01) Blaisdell, Fred W.; Donnelly, Charles A.
    The purpose of this report is to discuss tests made on a straight drop spillway and its energy dissipator and to present a design of energy dissipator for use in B Ditch at the Whiting Field Naval Air Station, Milton, Florida. The particular structure on which tests were made is designated B-6, but similar designs will be used for Structures F-5, G-2, L-2, S-l, and Y-6. The tests were requested by Mr. Moratz on September 27, 1948, the request amended on October 6, 1948, and the study completed on October 14, 1948.
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    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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    Hydraulics of Closed Conduit Spillways Part VIII. Miscellaneous Laboratory Tests Part IX. Field Tests
    (St. Anthony Falls Hydraulic Laboratory, 1958-03) Blaisdell, Fred W.
    The theory of the hydraulics of closed conduit spillways has been given in Part I of this report series. Parts II to VII, giving results of tests on several forms of the closed conduit spillway and discussion of vortices, have also been published. Parts VIII and IX, presented in this paper, report the results of tests on a number of additional forms of the closed conduit spillway. In contrast to the general tests reported in prior Parts, the tests reported here are model tests of specific field structures and actual field tests of full size structures. The results have been presented in such a way that they have general application to the design of the type of structure they represent.
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    Hydraulics of Closed Conduit Spillways Part X. The Hood Inlet
    (St. Anthony Falls Hydraulic Laboratory, 1958-04) Blaisdell, Fred W.; Donnelly, Charles A.
    Comprehensive experiments on the hood inlet for closed conduit spillways are reported. The capacity and performance of the spillway for variations of the hood inlet length, the conduit slope, the wall thickness and the approach conditions are described. The great effect of vortices on the spillway capacity is shown and anti-vortex devices are developed. Scour in the vicinity of the hood inlet is determined for various sizes of stone and equations for the scour hole dimensions are presented. A few special inlets were tested, the effect of rounding the entering edge being the principal variation.
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    Hydraulics of Closed Conduit Spillways Part XI. Test using Air
    (St. Anthony Falls Hydraulic Laboratory, 1966-01) Blaisdell, Fred W.; Hebaus, George G.
    The use of air instead of water to evaluate the full flow entrance loss coefficients and pressure coefficients for closed conduit spillways is the subject of this paper. The paper explains that air cannot be used as a substitute for water when the spillway is only part full, gives reasons for using air instead of water, presents background information, compares the water and air equations, develops the compressible flow equations required to analyze the data, and describes the test apparatus and procedure. Verification tests show that identical results can be obtained using either air or water.
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    Hydraulics of Closed Conduit Spillways Parts II through VII Results of Tests on Severa Forms of the Spillway
    (St. Anthony Falls Hydraulic Laboratory, 1958-03) Blaisdell, Fred W.
    The theory of the hydraulics of closed conduit spillways has been presented previously as Part I of this report series. Parts II to VI describe the laboratory tests, record the observed flow phenomena, and give the discharge and pressure coefficients necessary for the application of the theory. This information is given for five different forms of the closed conduit spillway, four of which are recommended. The drop inlet described in Part II is not recommended because of its poor hydraulic performance.
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    Straight Drop Spillway Stilling Basin
    (St. Anthony Falls Hydraulic Laboratory, 1954-11) Donnelly, Charles A.; Blaisdell, Fred W.
    This paper describes the development of the generalized design rules for a new stilling basin for use with the straight drop spillway. This generalized stilling basin design was developed because experience in the field had shown that there was no satisfactory stilling basin for the straight drop spillway. However, limited field experience indicates that this new design will adequately protect the downstream channel from scour. Water falling over the spillway crest falls onto a flat apron. The nappe is broken up by floor blocks, which also prevent damaging scour of the downstream channel banks. Scour of the downstream channel bed is prevented by an end still. Flaring wingwalls, triangular in elevation, prevent erosion of the dam fill. For proper operation of the stilling basin, the contraction of the flow at the ends of the spillway opening must be partially suppressed. The stilling basin can be used for a wide range of discharge, head on the crest, crest length, height of drop, and downstream tailwater level. An important finding is that the stilling basin length computed for the minimum tailwater levels. Dangerous scour of the downstream channel may occur if the nappe is supported sufficiently by high tailwater so that it lands beyond the end of the stilling basin. A method of computing the stilling basin length for all tailwater levels is presented. The design rules developed as a result of the laboratory tests were carefully checked an verified. An example shows how these rules are applied to the design of field structure.