Hydraulic Modelling

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Hydraulic Modelling

• by
• Professor Suphat Vongvisessomjai
• Course ED08.24 Modeling in Environmental
  Engineering

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Introduction

• Modeling of water quality
• Requires information on velocity fields (u,v,w)
  to transfer water quality parameters (DO or BOD)
• Can be obtained from Hydrodynamic or Hydraulic
  modeling

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Hydrodynamic or Hydraulic Modeling

• A process of solving for velocity fields through
  analytical or numerical methods or measurement in
  field

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Hydrodynamic Models

• A system of hydrodynamic equations consists of a
  continuity equation and 1, 2 or 3 equations of
  motion respectively for 1, 2 or 3 dimensional
  flows

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Continuity Equation

• A system of 2 equations to be solved for 2
  unknowns in describing tidal movement in a canal
  of constant depth h without bottom friction can
  be written as

(1)
(2)
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Equation of Motion without Frictional Force

• The above two equations (first order) can be
  expressed in terms of the water surface elevation
  or tidal velocity as a wave equation (second
  order)

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Second Order Equations
(3)
or
(4)
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Solution for Equations

• A solution of Eq. (1) and Eq. (2) for a tidal
  wave entering uniform canal of infinite length
  can be written as

(5)
(6)
where
T-period L-length of tide
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Solution for Equations

• By including a linear frictional force per unit
  weight of fluid gMu in Eq. (2),
• Eq. (3) and Eq. (4) are changed to the
  following

(7)
(8)
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Final Solution for Equations

• Solution for Eq. (7) (8) are

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Progressive Tide

• a uniform canal of infinite length without
  dissipation due to bottom friction

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Two-dimensional Hydrodynamic Model

• Demonstration Program
• Application of two-dimensional models to
  investigate the hydrodynamic conditions in the
  sea water systems
• Graphical presentation of the tidal current
  fields in the Gulf of Thailand

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Bathymetry of Gulf of Thailand
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Model Area of Upper Gulf of Thailand
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Summary of Grid Size with Model
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2 D Model - Demo

• Velocity Field in
• Gulf of Thailand (Coarse Grid)
• Upper Gulf of Thailand
• Mae Klong and Thachin River Mouths
• Map Taphut Area
• Pattaya Area

2 D Model
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Summary

• Hydrodynamic or Hydraulic Modelling are
• cheaper
• faster
• than measurements in the field

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The End