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• Hydraulics is a science dealing with the physical properties and movement phenomena of water
• Hydrostatics


  The part of hydraulics dealing with the laws of stationary fluids
• Hydrodynamics


  The part of hydraulics examining the laws of water movements
• Flows


  • Permanent flow: hydraulic characteristics in a given section do not change over time
  • Non-permanent flow: hydraulic characteristics of water movement in the examined section change over time with time
  • In practice, flows are not permanent, but if the time average of their hydraulic characteristics is constant, we speak of quasi-permanent movement
• The mean velocity vK (m/s), interpreted uniformly for the section, is the velocity value that, if it occurred at all points in the section, would cause the water transport to match the natural velocity distribution
• Flow rate, Q (m3/s)


  The volume of water, i.e. the volumetric flow, that has passed through a section A (m2) perpendicular to the flow in a unit time
• Bernoulli's theorem


  1. During the permanent flow of an ideal fluid, the sum of its positional, kinetic and pressure energy is the same and constant at any point in the fluid space

  2. z = the height of the center of the examined cross-section compared to the reference plane [m]

  3. g = the acceleration due to gravity, 9.81 m/s2

  4. v = mean flow velocity [m/s]

  5. p = pressure prevailing in the cross-section of the section [Pa]

  6. ρ = density of the liquid [kg/m³]
• Continuity Theorem


  In the case of an ideal fluid flow, the concept of continuity of movement means that the same flow of water passes through every section
• If the local energy losses are negligibly small (1-2%) compared to the friction losses, the pipeline is called hydraulically long, otherwise it is called hydraulically short
• Cross section


  The cross-section is usually a plane perpendicular to the longitudinal section and the intersecting line of the terrain. Facilities that fall within the line of the cross section are depicted in the vertical section of the cross section
• Taking a cross section

  1. The height survey of linear facilities and linear natural terrain structures is usually carried out by taking longitudinal and cross sections

  2. Longitudinal and cross section leveling are usually performed together

  3. When taking a longitudinal and cross section, characteristic terrain points located along a designated line and in its immediate vicinity are determined by simultaneous horizontal and height measurement. Horizontal determination is performed by length measurement (with a tape measure), height measurement is performed by leveling

  4. The location and distance from each other of the cross-sections may vary depending on the purpose of the survey. Factors: characteristic landforms, changes in the cross section
• Tools to take cross sections

  • Leveling instrument
  • Tape measure
  • Badge rod
• Hydraulic dimensioning of cross section

  The hydraulic basis of sizing is the Chèzy relation suitable for describing the permanent, uniform state
• Chezy's Formula


  • V=Average flow velocity (m/s)
  • R=Hydraulic radius (m)
  • So=Channel bed slope (no dimension/unitless)
  • C= Chezy's constant
• Manning's Formula


  n= Manning's Roughness coefficient (no dimension/unitless)
• Main factors influencing the movement of water in natural watercourses

  • force of gravity
  • an irregularly shaped bed constantly changing along its length
  • uneven bottom drop
  • bed and air resistance
  • internal fluid friction
  • sediment transport
  • ice phenomena
• Measurement of water movement

  • constant water level
  • slight bed change, practically unchanged bed cross-section
  • the section should be on a longer straight section of the watercourse
  • regularly shaped, uniform middle and floodplain
• Measurement principles


  • Occasional measurement
  • Continuous measurement
• Measurement types


  • Cubing
  • Measuring with a tumbler
  • Measurement with indicator material
  • Measurement based on the speed-area principle
  • Ultrasonic water flow measurement
  • Measurement based on the inductive principle
  • Another method
• Cubing


  1. Q: yield

  2. V: the measured amount of water (m3)

  3. t - the measurement time (seconds)
• Measuring with a tumbler

  1. It can be effectively used in the range of 2 - 20 l/s

  2. Types of portable measuring tumblers: square section side taper (Poncelet) tumbler, triangular section (right-angled triangle: Thomson) tumbler, trapezoidal, Chipoletti tumbler, circular cross-section tumbler
• Measurement based on the speed-area principle

  1. Determination of section area: with probing, with measuring weight, with an ultrasonic depth meter

  2. Determination of speed: with a float, with rotary vane water speedometer, with an inductive speedometer, with ultrasonic speedometer (Doppler principle)
• Calculation of water flow (yield/discharge)

  1. The cross-section and velocity distribution diagrams are divided into vertical bands of width Δl

  2. We read the depth and speed in the center line of each lane

  3. Multiplying the product of these two values by the lane width (Δl) gives the partial water yield of the lane

  4. The sum of the partial water flows gives the total water flow
• Hydraulics


  Hydraulik