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Browsing by Author "Song, Charles"

Now showing 1 - 7 of 7
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    Cerron Grande Project
    (St. Anthony Falls Hydraulic Laboratory, 1973-01) Song, Charles
    This report describes the results of a hydraulic model test for the Cerron Grande hydroelectric power project. A 1:100 undistorted scale model including the spillway, the power intake and outlet, the headwater approach channel, the spillway exit channel, and a portion of the existing river downstream of the proposed dam site was constructed and tested. All major features of the model performed satisfactorily. The deflector at the downstream end of the spillway was very effective and operated satisfactorily over the entire range of discharges tested. Concentrated vortices were found at the spillway gates when the four gates were not open equally.
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    The Generation of Internal Waves in Stratified Fluids
    (St. Anthony Falls Hydraulic Laboratory, 1973-06) Song, Charles; Hwang, Jack
    Internal waves in exponentially stratified fluids confined between two parallel boundaries have been studied analytically and experimentally with both a fixed and a free upper surfaoe. In the analytical model, waves were generated by vortex-like or sourcelike oscillatory disturbances. A modified image method was developed according to the principle of superposition using Hurley's elementary solutions for unbounded fluid. A basic image system which satisfies the wall boundary condition and is free of singularities in the flow field was found for every elementary vortex or source located anywhere in the field. The internal wave associated with this image system is intimately related to the characteristic mesh of the system. Only the first mode of the progressive internal wave is possible when the elementary vortex or source is located on the centerline of the channel. It appears that eccentrically located disturbances are required to generate higher mode internal waves, although numerical analysis has not been carried out for this case. An experiment was carried out in a channel filled with salt water of exponential density stratification. A rigid flat plate wave generator and a flexible rubber diaphragm wave generator located at mid-depth, both oscillating in a vertical direction, were used. Excellent agreement was obtained between the predicted and the measured wave length. The predicted wave shape and the measured wave shape were also in good agreement. Less complete agreement was obtained for the case of wave amplitude, however.
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    Hydraulic Model Study of South Yard Pier and Wave Screens
    (St. Anthony Falls Hydraulic Laboratory, 1974-11) Song, Charles
    This report describes the results of a hydraulic model test carried out to study the effectiveness of the proposed South Yard pier in sheltering a submarine, two APL models, and a YRBM model from wave action. Various types of wave screens were also tested. The submarine model was found to be very stable in waves with periods ranging from 2.8 seoonds to 8.2 seoonds with no wave screen. In fact, no screen tested in the study was found to contribute significantly to the stability of the submarine. The existence of the proposed pier alone reduced the amplitudes of pitching, rolling, and heave oscillations of an APL model by roughly 50 percent. A submarine model moored to the pier reduced the oscillations of an APL by another 50 peroent.
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    Hydraulic Model Tests for Mayfield Power Plant
    (St. Anthony Falls Hydraulic Laboratory, 1974-04) Song, Charles
    This report describes the results of the hydraulic model tests for the forebay structure of the Mayfield hydroelectric power plant conducted at the St. Anthony Falls Hydraulic Laboratory during the period May 1973 through March 1974. There are three existing power generating units, each of which is fed by an 18-ft-diameter penstock. Provisions have been made for an additional unit to be installed in the near future. Water is taken from Mayfield Lake, conveyed through a 37-ft-diameter tunnel, and discharged into a forebay. There are four intake structures, one for each penstock, at the downstream end of the forebay. Presently, the operation is hampered at high loading conditions. It is generally believed that unstable hydraulic conditions in the forebay are the cause of the present poor operating conditions. Strong vortices at the intakes have been observed in the field. The flow in the forebay is rough and turbulent. There are large shock waves at the pier noses, causing the water surface to fluctuate and become higher at units 42 and 43 and lower at unit 44. It is planned to add the fourth unit in the immediate future. Because an additional unit would mean an increased flow requirement, it is probable that the problems stated above would worsen. For this reason, a model study has been conducted to assess the problems for the expanded operation and find means of alleviating them. A 1:36 scale model was constructed and tested. After calibration, the model satisfactorily reproduced the existing flow conditions. The model indicated an increase in flow distortion and in water surface instability for the planned expansion. Air-entraining vortices were observed for all flows tested without modification of the existing facilities. On the basis of the experiments with various alternatives, the following schemes are recommended to provide good flow conditions: (a) two 18-ft-wide submerged guide vanes to be installed near the tunnel portal to redistribute the flow and improve the water surface profile and (b) a V-shaped vortex suppressor to be installed at each intake bay to eliminate the air-entraining vortices. A documentary motion picture showing the highlights of the model tests has been made as part of this test program.
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    Hydraulic Transient Analysis for the Culver-Goodman Tunnel Rochester, New York
    (St. Anthony Falls Hydraulic Laboratory, 1975-12) Song, Charles; Ring, Timothy; Young, Alwin; Leung, Kim
    This report describes a mixed-flow hydraulic transient model for the Culver-Goodman Tunnel of Rochester, New York. The model is based on the one-dimensional unsteady partial differential equations for open channels and closed conduits. These differential equations are solved numerically using the method of characteristics. Thus, the model is capable of dealing with the rapidly changing water hammer pressures and surges in a complex system. Hydrographs at 18 dropshafts due to a 5 year storm are used as the inputs. Outflow hydrographs, storage, depth or piezometric head, and velocity at 104 stations at small time intervals are obtained as output.
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    Simulation of the Quantity and Quality of Flow in a River Basin
    (St. Anthony Falls Hydraulic Laboratory, 1973-06) Song, Charles; Pabst, Arthur; Bowers, C. Edward
    Recognizing the importance of optimum use of our water resources, the Office of Water Resources Research and other governmental agencies have encouraged studies concerning quality improvement and optimum management of these resources. Because of the extremely complex nature of the problem, much more work is needed. The study reported on herein is concerned with simulating the quantity and quality of flow in fairly large watersheds or basins. The problem was separated into two parts: (a) simulation of water quantity on a continuous synthesis basis and (b) simulation of water quality by means of a model which would interact with the quantity model.
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    Vibration of Cavitating Hydrofoils
    (St. Anthony Falls Hydraulic Laboratory, 1969-10) Song, Charles
    A primarily experimental research program has been carried out using a free-jet water tunnel for the purpose of studying force and moment fluctuations on cavitating two-dimensional hydrofoils. Both a symmetrical wedge and a non-symmetrical wedge were tested for a wide range of cavity lengths and several different elastic conditions. Fluctuations in lift and moment were of primary concern in the experiments. It was revealed that the force and moment were quite steady if the cavity was longer than two chords unless an excessive amount of ventilation caused cavity pulsations. For a shorter cavity, however, the flow was generally very unstable, and severe vibrations were noted. A cavity of any length was found to be basically unstable and to oscillate at a characteristic frequency which was primarily a function of the cavity length. The vibrating cavity may cause an elastically supported foil to vibrate severely when the cavity is short. The largest-amplitude vibration often occurred when the cavity length was approximately equal to one chord. Flutter-like vibrations were noted in the first and second natural modes of the two-degree-of-freedom system. The frequency of these vibrations was found to be practically independent of the cavity length. The severest vibration in the first natural mode usually occurred when the average cavity length was approximately equal to one chord, whereas vibration in the second natural mode was found more likely to occur when the cavity was very short.