1. Agriculture University in Kraków Department of Water Engineering
Andrzej Strużyński, Maciej Wyrębek
Agriculture University in Kraków
Department of Water Engineering
Evaluation of the Nida River main current below the outlet of the perpendicular channel

2. XXVIII School of Hydraulics
Localization
XXVIII School of Hydraulics
23-26 September 2008, Krąg

3. XXVIII School of Hydraulics
Main hydrological parameters
Nida River basin
XXVIII School of Hydraulics
23-26 September 2008, Krąg
The area of the Nida River basin km2
- Brzegi (km 97.8) km2,
- Motkowice (km 76.1) km2 ,
- Pińczów (km 56.8) km2 .
The length of the Nida River km
Characteristic flows:
in Motkowice:
Q50% = 130 m3/s,
Q1% = 375 m3/s,
in Pińczów:
Q50% = 150 m3/s,
Q1% = 450 m3/s.
The average slope of the valley in the middle delta region
I = 0,0007

4. XXVIII School of Hydraulics
Localization
of the object
XXVIII School of Hydraulics
23-26 September 2008, Krąg

5. XXVIII School of Hydraulics
Main hydrological parameters
Nida River characteristics
XXVIII School of Hydraulics
23-26 September 2008, Krąg
The Nida River slope – the discharge: during summer – m3/s bankfull discharge – 40 – 60 m3/s mean diameter – 0.6 mm

6. XXVIII School of Hydraulics
Main hydrological parameters
Nida River characteristics
XXVIII School of Hydraulics
23-26 September 2008, Krąg
mean diameter – 0.6 mm

7. XXVIII School of Hydraulics
Main hydrological parameters
reservoir
XXVIII School of Hydraulics
23-26 September 2008, Krąg
The area of the reservoir – 10 ha
capacity – m3
designed maximum depth – 1.93 m
measured maximum depth – 1.5 m
average depth – 1 m
actual outflow – 170 l/s
needed outflow trough the additional duct – l/s
the discharge during floods – 750 l/s
actual retention – 8 days
needed retention – 2-4 days
the agreement for the intake water from the Nida River during winter – 272 l/s during summer – 1000 l/s

8. XXVIII School of Hydraulics
Governing equations
CCHE2D
XXVIII School of Hydraulics
23-26 September 2008, Krąg
The CCHE is an analysis system for two-dimensional, unsteady, turbulent river flow, sediment transport, and water quality evaluation Continuity equation: momentum equations:

9. XXVIII School of Hydraulics
Governing equations
CCHE2D
XXVIII School of Hydraulics
23-26 September 2008, Krąg
Reynolds stresses are approximated based on Boussinesq's assumption:
There are two zero-equation eddy viscosity models adopted in CCHE2D model. The first one is the depth-integrated parabolic model, in which the eddy viscosity vt is calculated by the fallowing formula:

10. XXVIII School of Hydraulics
Governing equations
superposition of potential flow
XXVIII School of Hydraulics
23-26 September 2008, Krąg
flow potentials:
where: w1 – potential flow in river, w2 – potential flow in channel, U – average velocity in river, z – imaginary variable, q – discharge per unit width, b – half width of the channel.
where: φ – velocity potential, ψ – current function.

11. XXVIII School of Hydraulics
CCHE2D modelling
XXVIII School of Hydraulics
23-26 September 2008, Krąg

12. XXVIII School of Hydraulics
CCHE2D modelling
XXVIII School of Hydraulics
23-26 September 2008, Krąg
profiles
up:
longitudinal in river
down:
longitudinal in channel with cross-section of Nida River

13. XXVIII School of Hydraulics
CCHE2D
results
XXVIII School of Hydraulics
23-26 September 2008, Krąg
case 0
river
Q = 8 m3/s
channel
Q = m3/s

14. XXVIII School of Hydraulics
CCHE2D
results
XXVIII School of Hydraulics
23-26 September 2008, Krąg
case 0
river
Q = 8 m3/s
channel
Q = m3/s

15. XXVIII School of Hydraulics
CCHE2D
case 2, Qr = 8, Qc = 0.45 [Q3/s]
XXVIII School of Hydraulics
23-26 September 2008, Krąg

16. XXVIII School of Hydraulics
CCHE2D
case 3, Qr = 8, Qc = 0.75 [Q3/s]
XXVIII School of Hydraulics
23-26 September 2008, Krąg

17. XXVIII School of Hydraulics
CCHE2D
case 4, Qr = 40, Qc = 0.75 [Q3/s]
XXVIII School of Hydraulics
23-26 September 2008, Krąg

18. XXVIII School of Hydraulics
CCHE2D
case 5, Qr = 70, Qc = 0.75 [Q3/s]
XXVIII School of Hydraulics
23-26 September 2008, Krąg

19. XXVIII School of Hydraulics
CCHE2D
case 2, Qr = 8, Qc = 0.45 [Q3/s]
results – comparing
XXVIII School of Hydraulics
23-26 September 2008, Krąg

20. XXVIII School of Hydraulics
CCHE2D
results
XXVIII School of Hydraulics
23-26 September 2008, Krąg
maximum safe velocity [m/s]

21. XXVIII School of Hydraulics
Results
XXVIII School of Hydraulics
23-26 September 2008, Krąg

22. XXVIII School of Hydraulics
Results
XXVIII School of Hydraulics
23-26 September 2008, Krąg

23. XXVIII School of Hydraulics
Main hydrological parameters
Nida River characteristics
XXVIII School of Hydraulics
23-26 September 2008, Krąg

24. XXVIII School of Hydraulics
CCHE2D
results
XXVIII School of Hydraulics
23-26 September 2008, Krąg
case 4, 5
case 3
case 1, 2

25. XXVIII School of Hydraulics
Results
XXVIII School of Hydraulics
23-26 September 2008, Krąg

26. XXVIII School of Hydraulics
1. Few conclusions
XXVIII School of Hydraulics
23-26 September 2008, Krąg
The results of performed modeling in cases 1 and 2 approved the possibility of using the proposed conduct during low flow conditions in river and reservoir.
The results calculated in case 3 indicate that flow from the channel would overcome parameters of bed stability.
As shown in case 4 results the conduct should not be used in high flow conditions appearing in the river. There would be possible to perform short term outflows of needed Q=0.75 [m3 s-1] of which influence would be easily supplement within the natural processes of aggradation of bed material.
In case 5 there is a backwater in the conduct. The drown outlet will increase flow resistance in the pipe (in CCHE2D modeled as channel). This would decrease the risk of using the conduct in flood conditions in the Nida River.
The CCHE2D modeling was finished with results which could be compared with Chezy calculations as well as with superposition of potential flow method.
The problem of instability of the model wasn't solved in performed modeling session. The results taken from created mesh should be verified on new mesh of higher density localized close to the outlet of the channel.

27. XXVIII School of Hydraulics
2. Few conclusions
XXVIII School of Hydraulics
23-26 September 2008, Krąg

28. XXVIII School of Hydraulics
2. Few conclusions
XXVIII School of Hydraulics
23-26 September 2008, Krąg
Thank you for your attention