Natural River simulation by using iRIC Nays2Dh

1. CE 4000
PROJECT AND THESIS
TWO DIMENSIONAL SIMULATION OF FLOW
IN PUSSUR RIVER USING iRIC NAYS2DH
Abu saad(1201010)
Supervisor: Professor Dr. Md. Shahjahan Ali
Major: Water Resources Engineering
Department of Civil EngineeringDepartment of Civil Engineering
Khulna University of Engineering & TechnologyKhulna University of Engineering & Technology

2. INTRODUCTION
 The simulation of water flow in rivers has been the
subject of many researches in the field of river
engineering.
 Pussur is a very important river in south western part of
Bangladesh as the second largest sea port of the country
is situated on the bank of this river. Mongla port uses
the river for its sea borne trading.
 At present, upto 7m draft vessels can travel from deep
sea to the Mongla Port jetty area. However, for the
transportation of coal for the proposed Rampal power
plant (which is situated 13km upstream of MP jetty
area), it is necessary to extend the navigation route for
7m draft vessel from MP jetty area to proposed Rampal
power plant at Chalna.

3. INTRODUCTION
•In this study numerical simulation were applied to this reach of
Pussur river to study the flow characteristics
•The reach is about 13km long, starting from Rampal power plant
to the downstream Sabur beacon Mongla. Here, the flow
characteristics of this portion during high tides and ebb tides
were simulated for different hydraulic conditions.

4. Figure 1 shows flow depth
of different times of the day
of the simulated portion of
the Pussur river.
Here we can see that the
minimum flow depth is near
0.8m (CD) and the
maximum flow depth above
3m (CD).
But sometimes the flow
depth decreases near 0.5m
(CD)
Figure 1: Flow depth variation of Pussur
river for different times of day
INTRODUCTION

5. OBJECTIVES
i. To simulate the flow at the reach of Pussur river
from Rampal power plant to Mongla Port for high
tides and ebb tides using different discharge.
ii. To compare the flow field of the selected reach of
Pussur river at for different discharge of high tides
and ebb tides.

6. METHODOLOGY
The basic steps of using iRIC Nays2DH are given below:
•To set the bed profile according to the hydrographic
data.
•River survey data from hydrographic chart (collected
from Mongla port) are used to prepare 30 sections of bed
profile and given as input
•To create the grid for the required flow domain.

7. METHODOLOGY
• To provide constant discharge as upstream boundary
condition and a constant depth as downstream
boundary condition.
• To select the model type for simulation.
• To run the simulation by using iRIC Nays2DH and
visualize the simulation results

8. Table 1 Different cases of river simulation
Case Discharge(m3
/sec) Water level
(m)
Case-I
(Ebb tide) 6000 0.5
Case-II
(Ebb tide) 6000 2.5
Case-III
(Ebb tide) 4000 0.5
Case-IV
(Ebb tide) 4000 2.5
Case-V
(High tide) -6000 0.5
Case-VI
( High tide) -6000 2.5
Case-VII
( High tide) -4000 0.5
Case-VIII
( High tide) -4000 2.5

9. PREPARATION OF
GRIDS
Bounday Conditions
Figure 2 Flow domain and
Computational mesh
Figure 3 Flow domain and
calculation grid super imposed
with Google map image.
Figure 2 and 3 shows the flow domain and the calculation grid with and without
Google map. Here he computational mesh consists of 146 x 15 grids for all cases

10. Table 2 Different flow parameters of river simulation
parameters value
Length of the river About 13 km
Width of the river About 1 km
No of grids 146x15=2190
Manning’s roughness co-efficient
for main channel
0.025
Manning’s roughness co-efficient
for flood plain channel
0.04

11. Table 3 Boundary conditions of the river simulation by
iRIC Nays2DH
Boundary condition
(without sediment transport)
value
Solver type Standard
Bed deformation Disabled
Finite differential method of advection
terms
Upwind Scheme
Periodic boundary condition Disabled
Output time interval 20 sec
Calculation time step 0.01 sec
Maximum number of iterations of water
surface calculation
80
Courant number 0.00024333

12. SIMULATION FOR EBB TIDE

13. SIMULATION FOR HIGH TIDE

14. RESULTS AND DISCUSSIONS
Figure 4 : Bed elevation counter with respect
to CD
The bed elevation
counter with
respect to Chart
Datum (CD) has
been shown in
Figure 4.2.
From this figure it
is seen that Sabur
beacon to Digraj,
the bed elevation is
within a range of
3m to around 6.5m
below the CD.Near
Rampal power
plant point the bed
elevation is less
than 1m below the
CD

15. RESULTS AND DISCUSSIONS
Figure 5:Velocity vector superimposed on depth counter for
case I
Figure 6: Velocity vector superimposed on velocity counter for
case I
In this case the simulation
has been performed for
ebb tides and a constant
discharge of 6000m3
/s is
given as boundary
condition of upstream and
a constant depth of +0.5m
CD is used as boundary
condition at downstream.
Figure 5 shows the water
depth is found to be varied
from about 0.5m to 7.8m
in selected portion of the
river.
Figure 6 shows the
velocity along the
navigation route is found
to be varied from about
0.929m/sec to 1.9m/sec.

16. RESULTS AND DISCUSSIONS
Figure 7:Velocity vector superimposed on depth counter for
case II
Figure 8: Velocity vector superimposed on velocity counter for
case II
In this case the simulation
has been performed for ebb
tides and a constant
discharge of 6000m3
/s is
given as boundary condition
of upstream and a constant
depth of +2.5m CD is used
as boundary condition at
downstream.
Figure 7 shows the water
depth is found to be varied
from about 2m to 9.5m in
selected portion of the river.
Figure 8 shows the velocity
is found to be varied from
about 0.25m/sec to
1.5m/sec.

17. RESULTS AND DISCUSSIONS
Figure 9:Velocity vector superimposed on depth counter for
case III
Figure 10: Velocity vector superimposed on velocity counter for
case III
In this case the simulation
has been performed for ebb
tides and a constant
discharge of 4000m3
/s is
given as boundary condition
of upstream and a constant
depth of +0.5m CD is used
as boundary condition at
downstream.
Figure 9 shows the water
depth is found to be varied
from about 0.5m to 7.5m in
selected portion of the river.
Figure 10 shows the velocity
is found to be varied from
about 0.5m/sec to 1.3m/sec.

18. RESULTS AND DISCUSSIONS
Figure 11:Velocity vector superimposed on depth counter for
case IV
Figure 12: Velocity vector superimposed on velocity counter for
case IV
In this case the simulation
has been performed for ebb
tides and a constant
discharge of 4000m3
/s is
given as boundary condition
of upstream and a constant
depth of +2.5m CD is used
as boundary condition at
downstream.
Figure 11 shows the water
depth is found to be varied
from about 2.0m to 8.5m in
selected portion of the river.
Figure 12 shows the velocity
is found to be varied from
about 0.2m/sec to 1.2m/sec.

19. RESULTS AND DISCUSSIONS
Figure 13:Velocity vector superimposed on depth counter for
case V
Figure 14: Velocity vector superimposed on velocity counter for
case V
In this case the simulation
has been performed for high
tides and a constant
discharge of -6000m3
/s is
given as boundary condition
of upstream and a constant
depth of +0.5m CD is used
as boundary condition at
downstream.
Figure 13 shows the water
depth is found to be varied
from about 0.5m to 7.8m in
selected portion of the river.
Figure 14 shows the velocity
is found to be varied from
about 0.3m/sec to 1.0m/sec.

20. RESULTS AND DISCUSSIONS
Figure 15:Velocity vector superimposed on depth counter for
case VI
Figure 16: Velocity vector superimposed on velocity counter for
case VI
In this case the simulation
has been performed for high
tides and a constant
discharge of -6000m3
/s is
given as boundary condition
of upstream and a constant
depth of +2.5m CD is used
as boundary condition at
downstream.
Figure 15 shows the water
depth is found to be varied
from about 3.0m to 10.0m in
selected portion of the river.
Figure 16 shows the velocity
is found to be varied from
about 0.1m/sec to 0.8m/sec.

21. RESULTS AND DISCUSSIONS
Figure 17:Velocity vector superimposed on depth counter for
case VII
Figure 18: Velocity vector superimposed on velocity counter for
case VII
In this case the simulation
has been performed for high
tides and a constant
discharge of -4000m3
/s is
given as boundary condition
of upstream and a constant
depth of +0.5m CD is used
as boundary condition at
downstream.
Figure 17 shows the water
depth is found to be varied
from about 0.5m to 7.0m in
selected portion of the river.
Figure 18 shows the velocity
is found to be varied from
about 0.1m/sec to
1.04m/sec.

22. RESULTS AND DISCUSSIONS
Figure 19:Velocity vector superimposed on depth counter for
case VIII
Figure 20: Velocity vector superimposed on velocity counter for
case VIII
In this case the simulation
has been performed for high
tides and a constant
discharge of -4000m3
/s is
given as boundary condition
of upstream and a constant
depth of +2.5m CD is used
as boundary condition at
downstream.
Figure 19 shows the water
depth is found to be varied
from about 4.0m to 9.0m in
selected portion of the river.
Figure 20 shows the velocity
is found to be varied from
about 0.1m/sec to 0.8m/sec.

23. RESULTS AND DISCUSSIONS
In figure 21 shows
the velocity
difference between
Case I and Case II.
Both of them has
same upstream
discharge 6000m3
/s.
But different
downstream depth.
From this figure it
is clear that the
velocity for case I
is higher than case
II
Figure 21:Comparison of velocity between case-I
and case-II

24. RESULTS AND DISCUSSIONS
In figure 22 shows
the velocity
difference between
Case III and Case
IV. Both of them
has same upstream
discharge 4000m3
/s.
But different
downstream depth.
From this figure it
is seen that the
velocity for case III
is higher than case
IV.
Figure 22:Comparison of velocity between case-
III and case-IV

25. RESULTS AND DISCUSSIONS
In figure 23 shows the
velocity difference
between Case V and
Case VI. Both of them
has same upstream
discharge 6000m3
/s. For
high tides. From this
figure it is clear that the
velocity for case V is
higher than case VI
along the at upstream.
After that for case VI
the velocity is higher
than case V. But near
the downstream the
velocity for case V
becomes high again. So
it is very much clear
that the velocity is too
much fluctuating in
nature
Figure 23:Comparison of velocity between case-
V and case-VI

26. RESULTS AND DISCUSSIONS
In figure 24 shows the
velocity difference
between Case VII and
Case VIII Both of them
has same upstream
discharge 4000m3
/s. For
high tides. From this
figure it is clear that the
velocity for case VII is
higher than case VIII
along the thalwegline at
upstream. After that for
case VIII the velocity is
higher than case VII.
But near the
downstream the velocity
for case VII becomes
high again. So it is very
much clear that the
velocity is too much
fluctuating
Figure 24:Comparison of velocity between case-
VII and case-VIII

27. CONCLUSIONS
• In this study numerical simulation by using iRIC Nays2DH
software were applied to this reach of Pussur river to study the
flow characteristics during high tides and ebb tides for different
flow conditions.
• This simulation have provided us with detailed information
regarding the flow pattern, the velocity, the bed elevation, the
water depth for high tides and ebb tides for the Pussur river.
• The model successfully generated the flow field, where the
dominated route of current and their directions are clearly
visualized

28. CONCLUSIONS
• It is seen that the water depth during high tides are higher than the
water depth during ebb tides. But the velocity during high tides
are generally smaller than the velocity during the ebb tides.
• And it is also seen that the velocity at different points of the
simulated portion of the river is more fluctuating in nature for high
tides than ebb tides.
• This result can help in selecting navigation route and prepare the
possible dredging plan.

29. Thanks
to
All