Estuarine

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Estuarine Coastal Modelling Course
MODULE X MODELLING WORKSHOP
Stephen Nash, Environmental Change Institute, NUI
Galway
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MODELLING WORKSHOP CONTENT- I The
Model II Scenarios III Dye Concentration
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I THE MODEL Cork Harbour

• DIVAST model
• 90m grid spacing
• 60 second timestep
• I 189, J 233
• gt 40,000 grid points
• Tidal forcing only
• gt No rivers

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II SCENARIOS
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II SCENARIOS Hydrodynamics

• Tidal Effect
• Run 1 Spring tide (tidal amplitude 2.1m)
• Plot timetrace in main channel (Point A)
• Velocity magnitude and water elevation
• Plot contour map of current magnitude
• High water (slack water) and mid-ebb (maximum
  currents)
• Run 2 Neap tide (tidal amplitude 1.05m)
• Plot timetrace in main channel (Point A) and
  compare with Run 1

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II SCENARIOS Points of Interest
Point A
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II SCENARIOS Hydrodynamics

• Instability
• Run 3 Spring tide (tidal amplitude 2.1m)
• As Run 1 but with larger timestep
• Model will terminate prematurely due to numerical
  instabilities

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II SCENARIOS Solute Transport

• Conservative Dye
• Run 4 Spring tide (tidal amplitude 2.1m)
• Continuous dye release from 3 outfalls no decay
  of dye
• Dye released at high water, 12.5 hrs
• Plot timetrace of dye concentration
• Outfall 1 (Point B) (top of Passage West)
• Point E location (bottom of Passage West)
• Plot contour maps of solute concentrations
• HW, HW1, HW3, HW5

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II SCENARIOS Points of Interest
Outfall 2 (Point C)
Outfall 1 (Point B)
Point E
Point A
Outfall 2 (Point C)
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III DYE CONCENTRATION
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III DYE CONCENTRATION Check on Initial Dye
Concentration

• The model will compute an initial dye
  concentration. We can check this
• Outfall A
• Flow rate 1m3/s
• Dye concentration 300 mg/l 300,000 mg/m3
• In 1 minute
• ? 1 m3/s x 60s 60 m3 of discharge from outfall
• 60 m3 x 300,000 mg/m3 18x106 mg dye released

11.8m
30m
30m
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III DYE CONCENTRATION Check on Initial Dye
Concentration

• The model will compute an initial dye
  concentration. We can check this
• Outfall A
• Dye mixes with (90 x 90 x 11.8) m3 of water
• ? Dye Concentration in water after 1 minute
• 18x106 / (90x90x11.8)
• 188.3 mg/m3
• 0.1883 mg/l

11.8m
30m
30m
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MODELLING WORKSHOP CONTENT- I The
Model II Scenarios III Dye Concentration
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Estuarine Coastal Modelling Course
MODULE X MODELLING WORKSHOP
Stephen Nash, Environmental Change Institute, NUI
Galway