Hydraulic Design - Longitudinal Devices

For the purposes of Hydraulic Design, the device longitudinal are divided into smaller parts in order to evaluate each section as a linear device. Thus, the calculation can take into account the differences in slope in each stretch, as well as more accurately assess the contribution area that effectively contributes at that point. Thus, the so-called "critical length" can be evaluated by observing the variation of the various quantities involved in the calculation.

Note that it is possible to visualize the graph of results for several quantities:

• Elevation, Double - represents the height of the section axis at each modeled station
• Slope (Slope, Double) - instant section slope
• Travel time (TP, Double) - travel time between one station and another
• System Time (TM, Double) - total travel time upstream of the stretch, for calculating precipitation
• Sum of C*A (SCXA, Double) - sum of the waterproofing coefficient (C) multiplied by the proportional area (Area) that contributes to the section in question
  Includes upstream device areas if any.
  Note: one or more Longitudinal catchments can be associated with the device and at a given station, not all catchments are contributing at that point and even those that contribute may not be fully upstream of the section. Thus, the Starting Station and Ending Station are weighted with an equivalent width, given per:
  L = Ending - Starting
  
  EquivalentWidth = ContributionArea / L
  
  Delta = If(Section.Station ≤ Catchment.Ending, Section.Station, Catchment.Ending) - Catchment.Starting
  
  SCXA = EquivalentWidth * Delta
  This ensures the weighting of the C coefficient and the flow assessment is more accurate.
• Total Area (AreaTotal, Double) - sum of the total upstream area of the section contributing to the section. Includes upstream device areas if any
• Distribution coefficient (nCr, Double) - Coefficient calculated as a function of the total area (see Standards / drainage / Delay Coefficient)
  
  nCr = f(TotalArea)
  
• Coefficient of Delay (CR, Double) - reducing factor for very large catchments, given by:
  
  CR = (Total Area) ^ (-nCr)
  Being the Total Area in hectares
• Precipitation (I, Double) - precipitation calculated for the recurrence time (TR) and system time (TM) calculated for the section
  
  I = f(TR, TM)
  
  The rain equation is configured in Options / drainage / Rain Equation
• Fantoli coefficient (F, Double)
  
  • If calculation method is DNIT
    F = 0.0725 * (I * TM) ^ (1 / 3))
  • Otherwise
    F = 1.0
  
  Where:
  • C - Runoff coefficient
  • I - Precipitation, depending on Tr and TM
• Freeboard Width (B, Double) - width of the water freeboard in contact with the atmosphere
• Wet Area (Am, Double) - area of the section filled by water in the device
• Wet Perimeter (Pm, Double) - length of the cross-sectional portion of the device in contact with water
• Hydraulic Radius(Rh, Double) - ratio between the wetted area and the wetted perimeter:
  
  Rh = Am / Pm
• Height of the Blade (hLam, Double) - height of the water board in the section
• Blade Flowing (Lamina, Double) - Ratio between the Height of the board flowing and the maximum possible board (h) of the device
  
  Lamina = hLam / h
• Clear Height (FreeBoard, Double) - difference between the maximum possible water depth (h) and the water depth in the section (hLam)
  
  FreeBoard = h - hLam
• Outflow Flowing (Qesc, Double) - flow flowing in the section
  
  Qesc = F * Cr * I * SCXA
• Velocity of Flow (Vesc, Double) - flow velocity of the section
  
  Vesc = Rh ^ (2.0 / 3.0) * Slope ^ 0.5 / ACMan
  
  ACMan is the Manning coefficient
• Froude number (Fr, Double) - given by:
  
  yh = Am / B
  
  Fr = Vesc / (g * yh) ^ 0.5
  
  g is the Gravity Acceleration
• Tractive Tension (TT, Double) - Trative tension of the water in the section, given by:
  
  TT = Gamma * Rh * Slope
  
  
  Gamma is the density of water flowing through the section

To access these properties, select the longitudinal gravity device and use the tab Hydraulic Sections