{"id":2293,"date":"2020-03-31T11:02:47","date_gmt":"2020-03-31T11:02:47","guid":{"rendered":"https:\/\/seismicconsolidation.com\/?p=2293"},"modified":"2020-03-31T11:03:00","modified_gmt":"2020-03-31T11:03:00","slug":"study-characteristics-of-flow-on-a-plane-and-gravel-bed","status":"publish","type":"post","link":"https:\/\/seismicconsolidation.com\/study-characteristics-of-flow-on-a-plane-and-gravel-bed\/","title":{"rendered":"Study characteristics of flow on a plane and gravel bed"},"content":{"rendered":"

<\/a>Study characteristics of flow on a plane and gravel bed<\/h1>\n

<\/a>Objectives:<\/h2>\n
    \n
  1. To derive Chezy\u2019s and Manning\u2019s roughness coefficients for S6 Tilting Flume in laboratory.<\/li>\n
  2. To study the effect of Chezy\u2019s and Manning\u2019s roughness coefficient on plane and gravel bed.<\/li>\n
  3. To study relationship between Chezy\u2019s and Manning\u2019s roughness coefficient.<\/li>\n
  4. To compare average Chezy\u2019s and Manning\u2019s roughness coefficients with the values available in literature.<\/li>\n
  5. To plot the bed profile, hydraulic grade line & energy line for different discharges on different beds.<\/li>\n<\/ol>\n

    <\/a>Apparatus:<\/h2>\n
      \n
    1. S6 tilting flume<\/li>\n
    2. Point gauge<\/li>\n
    3. Plane and gravel bed arrangement<\/li>\n<\/ol>\n

      <\/a>Related theory:<\/h2>\n

      <\/a>Flume:<\/h3>\n

      Flume is a man-made open channel for flow of water in the form off open declined gravity channel.<\/p>\n

      <\/a>Flow:<\/h3>\n

      The quantity of fluid passing through any particular section per unit time.<\/p>\n

      <\/a>Uniform flow:<\/h3>\n

      A flow in which flow parameters like velocity, depth & pressure remains constant in between two sections of a pipe or channel at any given instant of time.<\/p>\n

      \"\"<\/strong><\/p>\n

      \"\"<\/p>\n

      Figure: Uniform Flow<\/p>\n

      <\/a>Non-uniform flow:<\/h3>\n

      A flow in which flow parameters like velocity, depth & pressure do not remain constant in between two sections of a pipe or channel at any given instant of time.<\/p>\n

      \"\"<\/p>\n

      Figure: Establishment of uniform flow in a long channel<\/p>\n

      <\/a>Steady flow:<\/h3>\n

      The type of flow in which the fluid characteristics like velocity, pressure, density etc at a point do not change with time<\/p>\n

      \"\"<\/p>\n

      <\/a>Unsteady flow:<\/h3>\n

      The type of flow in which the fluid characteristics like velocity, pressure, density etc at a point change with time.<\/p>\n

      \"\"<\/p>\n

      <\/a>Laminar flow:<\/h3>\n

      The type of flow in which the fluid particles move along well defined paths or stream line and all the stream lines are straight and parallel. This type of flow is also called stream line flow or viscous flow.<\/p>\n

      Its Reynold number is less than 2000.<\/p>\n

      <\/a>Turbulent flow:<\/h3>\n

      The flow in which the fluid particles move in a zig-zag way. Due to movement in this manner, the eddies formation takes place which are responsible for high energy loss.<\/p>\n

      Its Reynold number is more than 4000.<\/p>\n

      Note: if Rn lies between 2000-4000, the flow may be laminar or turbulent.<\/p>\n

      <\/a>Open channel:<\/h3>\n

      A conduit in which fluid flow is with a free surface and under gravity.<\/p>\n

      <\/a>Prismatic channel:<\/h3>\n

      Channels having same cross sections are prismatic.<\/p>\n

      <\/a>Chezy\u2019s formula:<\/h3>\n

      The formula is named after\u00a0Antoine de Ch\u00e9zy, the French hydraulics engineer who devised it in 1775. It describes the mean\u00a0flow velocity\u00a0of\u00a0steady,\u00a0turbulent\u00a0open channel flow.<\/p>\n

      \"\"<\/p>\n

      Where,<\/p>\n

      c= Chezy\u2019s constant and it depends on roughness of the channel bed (m1\/2<\/sup>s-1<\/sup>)<\/p>\n

      v= Average velocity (m\/s)<\/p>\n

      R= Hydraulic radius (m)<\/p>\n

      S= Slope of energy line (m\/m)<\/p>\n

      <\/a>Manning\u2019s formula:<\/h3>\n

      It\u00a0is an\u00a0empirical formula\u00a0estimating the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid, i.e.,\u00a0open channel flow. However, this equation is also used for calculation of flow variables in case of\u00a0flow in partially full conduits, as they also possess a free surface like that of open channel flow. All flow in so-called open channels is driven by\u00a0gravity. It was first presented by the French engineer Philippe Gauckler in 1867,\u00a0and later re-developed by the Irish engineer\u00a0Robert Manning\u00a0in 1890.<\/p>\n

      \"\"<\/p>\n

      Where,<\/p>\n

      n= Manning\u2019s coefficient (s\/m1\/3<\/sup>)<\/p>\n

      v= Average velocity (m\/s)<\/p>\n

      R= Hydraulic radius (m)<\/p>\n

      S= Slope of energy line (m\/m)<\/p>\n

      <\/a>Factors affecting Manning\u2019s roughness coefficient:<\/h3>\n
        \n
      1. Surface roughness (for fine grained less \u201cn\u201d, fine coarse grained more \u201cn\u201d value)<\/li>\n
      2. Vegetation (height, density, distribution and type of vegetation)<\/li>\n
      3. Channel irregularity (variation in wetted perimeter, shape, cross section & size along channel length)<\/li>\n
      4. Channel alignment (smooth curvature with large radius will give less \u201cn\u201d value whereas sharp curvature with severe meandering will increase \u201cn\u201d<\/li>\n
      5. Silting and scouring<\/li>\n
      6. Obstruction<\/li>\n
      7. Size and shape of channel<\/li>\n
      8. Stage and discharge<\/li>\n
      9. Seasonal change<\/li>\n
      10. Suspended material and bed load<\/li>\n<\/ol>\n

        <\/a>Importance of determining Manning\u2019s roughness coefficient:<\/h3>\n
          \n
        1. It estimates the resistance to flow in a given channel or pipe.<\/li>\n
        2. Different types of channels have different n values e.g. earthen channels, concrete channels. If these values are not correctly estimated then velocity and discharge would not be accurately determined.<\/li>\n
        3. The value also changes with respect to bed grains of channel.<\/li>\n
        4. For the design of power channels, the correct manning\u2019s roughness coefficient is required.<\/li>\n
        5. Also, in irrigation channels the manning\u2019s roughness coefficient is required for proper channel design.<\/li>\n<\/ol>\n

          <\/a>Relation between Chezy\u2019s and Manning\u2019s roughness coefficient:<\/h3>\n

          C=R1\/6<\/sup>\/n<\/p>\n

          <\/a>Procedure:<\/h2>\n
            \n
          1. Turn the pump on of the apparatus.<\/li>\n
          2. Wait to stabilize the water in flume<\/li>\n
          3. Measure the width of the channel (B).<\/li>\n
          4. Adjust suitable value of the slope.<\/li>\n
          5. For constant values of slope, vary discharge \u201cQ\u201d and measure depth of flow of water at different locations and take the average depth.<\/li>\n
          6. Compute area of flow, wetted perimeter, velocity, hydraulic radius, Chezy\u2019s and Manning\u2019s roughness coefficient.<\/li>\n
          7. Plot energy line and graphs between n & v, c &v, n &c of plane and gravel beds.<\/li>\n<\/ol>\n

            <\/a>Observations and calculations:<\/h2>\n

            Flume dimensions:<\/p>\n\n\n\n\n\n
            Width<\/strong><\/td>\n300 mm<\/td>\n<\/tr>\n
            Length<\/strong><\/td>\n10 m<\/td>\n<\/tr>\n
            Slope<\/strong><\/td>\n1:500<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

            \"\"<\/p>\n

            Result:<\/strong><\/p>\n

            Average Chezy\u2019s constant for plain bed= 42.266 m1\/2<\/sup>s-1<\/sup><\/strong>\u00a0<\/strong><\/p>\n

            Average Manning\u2019s constant for plain bed= 14.777 *10-3<\/sup> s\/m1\/3<\/sup><\/p>\n

            \"\" \"\" \"\"<\/sup><\/p>\n

            \"\"<\/p>\n

            Result:<\/strong><\/p>\n

            Average Chezy\u2019s constant for plain bed= 65.381 m1\/2<\/sup>s-1<\/sup><\/strong>\u00a0<\/strong><\/p>\n

            Average Manning\u2019s constant for plain bed= 9.213 *10-3<\/sup> s\/m1\/3<\/sup><\/p>\n

            \"\" \"\" \"\"<\/p>\n

            Bed profile, hydraulic grade line and energy line for gravel bed<\/strong><\/p>\n

            \"\"<\/p>\n

            \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\"<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
            \n

            <\/a>Comparison<\/h2>\n<\/td>\n<\/tr>\n

            Chezy’s Coefficient<\/td>\nComments<\/td>\nSource<\/td>\n<\/tr>\n
             <\/td>\nLaboratory flume<\/td>\nLiterature<\/td>\n <\/td>\n <\/td>\n <\/td>\n<\/tr>\n
            Plain bed<\/td>\n42.266<\/td>\n30<\/td>\n <\/td>\nSteel<\/td>\nRiver mechanics by Pierre Y. Julien<\/td>\n<\/tr>\n
            Gravel bed<\/td>\n65.381<\/td>\n32-68<\/td>\n <\/td>\nGraveled surface<\/td>\nRiver mechanics by Pierre Y. Julien<\/td>\n<\/tr>\n
            Manning’s Coefficient<\/td>\n <\/td>\n <\/td>\n <\/td>\n<\/tr>\n
             <\/td>\nLaboratory flume<\/td>\nLiterature<\/td>\n <\/td>\n <\/td>\n <\/td>\n<\/tr>\n
            Plain bed<\/td>\n0.01477<\/td>\n0.014<\/td>\nMaximum<\/td>\n <\/td>\nOpen channel Hydraulics by Ven te Chow<\/td>\n<\/tr>\n
            Gravel bed<\/td>\n0.00921<\/td>\n0.022<\/td>\nNormal<\/td>\nGravel uniform section, clean<\/td>\nOpen channel Hydraulics by Ven te Chow<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

             <\/p>\n

            <\/a>Comments:<\/h2>\n
              \n
            1. The manning\u2019s and Chezy\u2019s constants have not been calculated by using slope of energy lines because slope of energy lines are coming to be negative in graphs. The negative slope will give undefined results for the calculations of co-efficients.<\/li>\n
            2. The reason of negative slope is that with increasing distance the depth of water is increasing which is not the real scenario. It should be decreasing.<\/li>\n
            3. The graph of C vs V & n vs V are nearly straight line which shows that it is the property of bed which does not change with change in velocity.<\/li>\n
            4. From the graph of manning\u2019s vs chezy\u2019s roughness coefficients it can be verified that these two are inversely proportional to each other.<\/li>\n
            5. The literature values are reported in comparison table which indicates that our results are close to literature values.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

              Study characteristics of flow on a plane and gravel bed Objectives: To derive Chezy\u2019s and Manning\u2019s roughness coefficients for S6 Tilting Flume in laboratory. To study the effect of Chezy\u2019s and Manning\u2019s roughness coefficient on plane and gravel bed. To study relationship between Chezy\u2019s and Manning\u2019s roughness coefficient. To compare average Chezy\u2019s and Manning\u2019s roughness…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[238],"tags":[282],"_links":{"self":[{"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/posts\/2293"}],"collection":[{"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/comments?post=2293"}],"version-history":[{"count":1,"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/posts\/2293\/revisions"}],"predecessor-version":[{"id":2321,"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/posts\/2293\/revisions\/2321"}],"wp:attachment":[{"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/media?parent=2293"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/categories?post=2293"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/seismicconsolidation.com\/wp-json\/wp\/v2\/tags?post=2293"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}