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    Open Channel Hydraulic (Ven Te Chow)

    Uploaded by

    Gigih Adhityatama

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Open Channel Hydraulic (Ven Te Chow)

    Uploaded by

    Gigih Adhityatama
    10 views2 pages

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

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    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    10 views2 pages

    Open Channel Hydraulic (Ven Te Chow)

    Uploaded by

    Gigih Adhityatama

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 2

    404 RAPIDLY VARIED FLOW

    After the length of jump is determined, a horizontal intercept EF equal to 9.6 ft

    is found between the curve A'F'B and CF'D. The hydraulic jump will, therefore,

    occur between G and F. As shown in Fig. 15-8, the jump appears to start at a dis­

    tance of about 140 ft from the vena contracta. Since the location of the jump is

    determined, the approximations mentioned above can be checked, and more exact

    determination can be made by repeating the procedure if desired. Such verification

    seems unnecessary, however, on account of the approximations involved in the theory

    and other aspects of the problem.

    15-8. Jump as Energy Dissipator. From a practical viewpoint,

    hydraulic jump is a useful means of dissipating excess energy in super­

    critical flow. Its merit is in preventing possible erosion below overflow

    spillways, chutes, and sluices, for it quickly reduces the velocity of the

    flow on a paved apron to a point where the flow becomes incapable of

    scouring the downstream channel bed.

    The hydraulic jump used for energy dissipation is usually confined

    partly or entirely to a channel reach that is known as the stilling basin.

    The bottom of the basin is paved to resist scouring. In practice, the

    stilling basin is seldom designed to confine the entire length of a free

    hydraulic jump on the paved apron, because such a basin would be too

    expensive. Consequently, accessories to control the jump are usually

    installed in the basin. The main purpose of such control is to shorten

    the range within which the jump will take place and thus to reduce the

    size and cost of the stilling basin. The control has additional advantages,

    for it improves the dissipation function of the basin, stabilizes the jump

    action, and in some cases increases the factor of safety. In designing a

    stilling basin using hydraulic jump as energy dissipator, the following

    practical features should be considered.

    A. Jump Position. There are three alternative patterns (Fig. 15-9)

    that allow a hydraulic jump to form downstream from the source (such

    source as an overflow spillway, a chute, or a sluice):

    Case I represents the pattern in which the tailwater depth y%' is equal

    to the depth y» sequent to yr. In this case, the values of F,, g,, and

    y' (= ») will satisfy Eq. (3-21), and the jump will occur on a solid apron

    immediately ahead of the depth y,. For scour-protection purposes, this is

    an ideal case. One big objection to this pattern, however, is that a little

    difference between the actual and assumed values of the relevant hydrau­

    lic coefficients may cause the jump to move downstream from its esti­

    mated position. Consequently, some device to control the position of

    the jump is always necessary.

    Case 2 represents the pattern in which the tailwater depth y,' is less

    1 For simplicity, the length of the hydraulic jump will not be considered in the

    present discussion. See [25], [34], [35], [43], and "Hydraulic Energy Dissipators," by

    E. A. Elevatorski, McGraw-Hill Book Company, Inc., New York, 1959, for further

    information on the design of stilling basins.

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