{"id":291,"date":"2020-01-25T12:07:59","date_gmt":"2020-01-25T12:07:59","guid":{"rendered":"https:\/\/seismicconsolidation.com\/?p=291"},"modified":"2020-01-26T10:59:21","modified_gmt":"2020-01-26T10:59:21","slug":"estimation-of-coefficient-of-weir-for-ogee-weir","status":"publish","type":"post","link":"https:\/\/seismicconsolidation.com\/estimation-of-coefficient-of-weir-for-ogee-weir\/","title":{"rendered":"Estimation of coefficient of weir for ogee weir"},"content":{"rendered":"

<\/a>1.\u00a0\u00a0\u00a0\u00a0 Estimation of coefficient of weir for ogee weir<\/h2>\n

<\/a><\/a>1.1.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Objectives:<\/h3>\n
    \n
  1. To find coefficient of weir for ogee weir.<\/li>\n
  2. To observe relationship between discharge and coefficient of weir.<\/li>\n
  3. To observe relationship between discharge and head above crest of weir.<\/li>\n<\/ol>\n

    <\/a><\/a>1.2.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Apparatus:<\/h3>\n
      \n
    1. Ogee weir<\/li>\n
    2. Point gauge<\/li>\n
    3. S6 tilting flume assembly<\/li>\n<\/ol>\n

      <\/a><\/a>1.3.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Related theory:<\/h3>\n

      <\/a>1.3.1.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Weir:<\/a><\/h4>\n

      A\u00a0weir<\/strong>\u00a0or\u00a0low head dam<\/strong>\u00a0is a barrier across the horizontal width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. There are many designs of weir, but commonly water flows freely over the top of the weir crest before cascading down to a lower level.<\/p>\n

      1.3.2.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Functions of weir:<\/h4>\n

      Weirs are commonly used to prevent\u00a0flooding<\/a>, measure water discharge, and help render rivers more\u00a0navigable<\/a>\u00a0by boat. In some locations, the terms\u00a0dam<\/a>\u00a0and weir are synonymous, but normally there is a clear distinction made between the structures. A dam is usually specifically designed to impound water behind a wall, whilst a weir is designed to alter the river flow characteristics.<\/p>\n

      A common distinction between dams and weirs is that water flows over the top (crest) of a weir. Accordingly, the crest of an overflow\u00a0spillway<\/a>\u00a0on a large dam may therefore be referred to as a weir. Weirs can vary in size both horizontally and vertically, with the smallest being only a few inches in height whilst the largest may be hundreds of metres long and many metres tall<\/p>\n

      1.3.3.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Flow measurement<\/h4>\n

      Weirs allow\u00a0hydrologists<\/a>\u00a0and engineers a simple method of measuring the\u00a0volumetric flow rate<\/a>\u00a0in small to medium-sized streams\/rivers or in industrial discharge locations. Since the geometry of the top of the weir is known and all water flows over the weir, the depth of water behind the weir can be converted to a rate of flow. However, this can only be achieved in locations where all water flows over the top of the weir crest. If this condition is not met, it can make flow measurement complicated, inaccurate or even impossible.<\/p>\n

      The discharge calculation can be summarized as:<\/p>\nQ<\/mi>=<\/mo>C<\/mi>L<\/mi>H<\/mi>n<\/mi><\/msup><\/math>\n

      Where:<\/p>\n

      Q<\/em>\u00a0is the\u00a0volumetric flow rate<\/a>\u00a0of fluid (the\u00a0discharge<\/a>)<\/p>\n

      C<\/em>\u00a0is the\u00a0flow coefficient<\/a>\u00a0for the structure (on average a figure of 0.62)<\/p>\n

      L<\/em>\u00a0is the width of the\u00a0crest<\/a><\/p>\n

      H<\/em>\u00a0is the height of\u00a0head<\/a>\u00a0of water over the crest<\/p>\n

      n<\/em>\u00a0varies with structure (e.g., 3\/2 for horizontal weir, 5\/2 for v-notch weir)<\/p>\n

      However, this calculation is a generic relationship and specific calculations are available for the many different types of weir. Flow measurement weirs must be well maintained if they are to remain accurate.<\/p>\n

      \"\"<\/p>\n

      <\/a>Figure 1.1: A weir on the Yass River, New South Wales, Australia directly upstream from a shared pedestrian-bicycle river crossing<\/p>\n

      1.3.4.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Types of weirs:<\/h4>\n

      Weirs are classified according to:<\/p>\n

        \n
      1. Shape of opening<\/li>\n
      2. Shape of crest<\/li>\n<\/ol>\n
        <\/a>1.3.4.1.\u00a0\u00a0\u00a0\u00a0\u00a0 Types of Weirs based on Shape of the Opening:<\/h5>\n
          \n
        1. Rectangular weir<\/li>\n<\/ol>\n

          It is a standard shape of weir. The top edge of weir may be sharp crested or narrow crested. It is generally suitable for larger flowing channels.<\/p>\n

          \"\"<\/p>\n

          <\/a>Figure 1.2: Rectangular shaped weir<\/p>\n

            \n
          1. Triangular weir<\/li>\n<\/ol>\n

            The shape of the weir is actually reverse triangle like V. so, it is also called V-notch weir. This type of weirs are well suitable for measuring discharge over small flows with greater accuracy.<\/p>\n

            \"\"<\/p>\n

            <\/a>Figure 1.3: Triangular shaped weir<\/p>\n