Download - POLLUTION OF COASTAL ZONES DUE TO DEFLECTIONS OF RIVERS UNDER THE INFLUENCE OF THE CORIOLIS FORCE
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: [email protected], [email protected], [email protected]
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