POLLUTION OF COASTAL ZONES DUE TODEFLECTIONS OF RIVERS UNDER THE INFLUENCE

OF THE CORIOLIS FORCE

Grigoriadou V., Konidaris A., Angelidis P., Kotsovinos N.

Department of Civil Engineering, Democritus University of Thrace,V. Sofias 12, Xanthi 67100, Greece

e-mails: akonida@civil.duth.gr, pangelid@civil.duth.gr, kotsovin@civil.duth.gr

Surface plume trajectory of river discharging into sea

Initial momentum at the estuary

Buoyancy forces due to the density difference of the sea ambient

Surface shear stress due to the winds

Geomorphology of the seabed

Coriolis force due to the earth’s rotation

Satellite image of North Aegean and Propontis (June 2003)

(source: http//modis.gsfc.nasa.gov/)

motor

Angular velocity control sensor

cameras

flow meter

PC

Observation platform

55.2m.2m

1.0m1.0m

15cm15cm

Outflow pipe

Usage of potassium permanganate (red colour)

Identical density for outflow & ambient water

Rotation of the basin for some hours before the experiment, for the ambient water to acquire rigid body form

30cm30cm

26 experiments

Volume rate Q: 0.48 – 1.76 lt/min

Rotation period Τ: 30 – 90 s

Froude number: : 0.33 – 1.19

Rossby number: : 0.017 – 0.214

o

o

UF

gd

o

o

UF

gd

o

UR

L

INERTIAL FORCES

GRAVITY FORCES

INERTIAL FORCES

CORIOLIS FORCES

y max

t/T=5.67

Behavior at the initial phase of the spread

Dimensionless parametric equation of the trajectory (clotoid curve)

: characteristic length

: dimensionless distance along the trajectory

Jr : momentum flux at the orifice

α : 0.01 - 0.095Valid for deep

ambient (h/L > 0.2)

1 ln 2

2rJπ

LaΩ ρ

x

y

0 0.2 0.4 0.6 0.8 1x/L0

0.2

0.4

0.6

0.8

1

y/L

2

0

sin2

rx r πx r r dr

L

2

0

cos2

ry r πy r r dr

L

8r tr

rL

tt

T

Comparison of an experimental trajectory at the initial phase of spread with

the theoretical clotoid curve from Savage & Sobey.

Q = 0.96 lt/min

T = 60 sec

Ltheor. = 0.44 m

Fo = 0.65

Ro = 0.08

y max

t/T=5.67

0.2 0.4 0.6 0.8 1.0Fo

0.6

0.8

1.0

1.2

1.4

Ymax/YA

1.0 1.1 1.2 1.3Fo

2.0

2.2

2.4

2.6

2.8

Ymax/YA

Fo < 1 Fo > 1

Correlation of the dimensionless maximum spread width and the Froude number

APPLICATION: calculation of the maximum

spread width for flood discharge of Evros river

Q = 3000 m3/s

average estuary depth: 4m Uo = 1.25 m/s

estuary width: 600m

41o north parallel Τ = 37 hr

natural river α = 0.01

L = 11640 m

YΑ = 0.8L = 9300 m

Fo = 0.2 Ymax/YA = 1.3 Ymax = 12000 musing graph

CONCLUTIONS

The influence of the earth’s rotation (Coriolis force) on the spread of the large scale environmental flow was studied

A series of experiments with horizontal outflow in rotating ambient was performed

Deflection to the right of the outflow axes was observed

The theory of Savage & Sobey that at the initial phase the trajectory of the front follows the clothoid curve was validated

The existence of a maximum spread width, where the discharge water is restricted and remains for a long time was detected

A method for the calculation of the maximum spread width was suggested, as a function of the initial conditions:

• outflow velocity

• outflow momentum flux

• angular velocity

• ambient depth