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11. March 2010
I. Klein, S. Peterseim, L. Sauder, L. Schneider, K. Urbanek
Dr. M. Oertel, Prof. Dr. A. Schlenkhoff
Hydraulic Engineering SectionCivil Engineering Departement
Bergische University of WuppertalGERMANY
Investigations on a rough slide
in a physical model
Slide 2Investigations on a rough slide in a physical model 11. March 2010
Contents
• Introduction
• Physical Model– Model configurations– Discharges– Modelruns– Measuring technique
• Results
• Conclusion
Slide 3Investigations on a rough slide in a physical model 11. March 2010
Rough ramps and slides
• Erosion protection of river beds
• fish-climb possibility
• classified by• slope• arrangement of stones
Photograph of an example rough slide at the Wupper river, Germany
Introduction
Physical Model
Results
Conclusion
Slide 4Investigations on a rough slide in a physical model 11. March 2010
Physical model
• A physical model of a rough slide is built up at the University of Wuppertal’s Hydraulic Laboratory
• scaled 1:15
• to get information about main flow characteristics as well as forces on the boulders
• the physical model allows variations ofboulder arrangements and discharges
Photo of an example model run
Introduction
Physical Model
Results
Conclusion
Slide 5Investigations on a rough slide in a physical model 11. March 2010
Measuring technique: Load-cells
• Measuring forces on the boulders in flow direction
• SOEMER platform-load-cells, type 1040
• nominal load 5kg
• record tensions
Source: www.soemer.de
Introduction
Physical Model
Results
Conclusion
Slide 6Investigations on a rough slide in a physical model 11. March 2010
Measuring technique: Ultrasonic sensors
• Six sensors are measuring the water surface elevation in a 5x5 cm grid:
• for calibration and validation of the numerical model
• for final analysis
Example results of water depth for one boulder configuration in physical model
Introduction
Physical Model
Results
Conclusion
Slide 7Investigations on a rough slide in a physical model 11. March 2010
Physical model
• Boulders are sized l x w x h = 6x6x6 cm
• four varying discharges are combined with 10 boulder configurations
• discharges between 7 – 46 l/s (in prototype ~ 6 - 40 m³/s)
Introduction
Physical Model
Results
Conclusion
Slide 8Investigations on a rough slide in a physical model 11. March 2010
Froude-model for prototype
• The results of the physical model are scaled to prototype with the Froude-model
• λ is the scaling factor
Introduction
Physical Model
Results
Conclusion
3
5
λλλ
λ
mp
mp
mp
mp
FFQQvvLL
====
force discharge
velocity length
Slide 9Investigations on a rough slide in a physical model 11. March 2010
Forces on boulders and drag coefficients
• Forces caused by the flow on single stones:
with: cD = drag coefficient, A = load area, ρ = density, v = velocity
Results for example forces on boulder configuration in physical model scaled to prototype
Introduction
Physical Model
Results
Conclusion
2²vAcF Dx ρ=
Slide 10Investigations on a rough slide in a physical model 11. March 2010
Forces on boulders and resulting drag coefficients
• National guidelines: cD = 0.5 to 1.5 for rough ramps and slides
• drag coefficient depends on various boundary conditions
• drag coefficients of boulders in the physical model can be calculated by:
Introduction
Physical Model
Results
Conclusion
2
2AvFc x
D ρ=
Slide 11Investigations on a rough slide in a physical model 11. March 2010
Forces on boulders and resulting drag coefficients
• Including hydrostatic forces modified drag coefficient can be defined as:
Case 1 Case 2 Case 3
Introduction
Physical Model
Results
Conclusion
bbbbb
*D
bbbbbb
*D
bbbb
*D
hhhh)hh(hgbF²vhb
c
hhhh)h]h[h(hgbF²vhb
c
hhhh)hh(gbF²vhb
c
>>−−=
≤>−−−=
≤≤−−=
21211
212
211
212
22
11
22121
21221
21
and for
and for
and for
ρ
ρ
ρ
Slide 12Investigations on a rough slide in a physical model 11. March 2010
Forces on boulders and resulting drag coefficients
• Modified drag coefficients of 1.1 for single boulders up to 6.5 for boulder assembles can be calculated
• the results for large water surface differences in combination with small measured forces are unrealistic
necessarity of more detailed investigations⇒
Introduction
Physical Model
Results
Conclusion
Slide 13Investigations on a rough slide in a physical model 11. March 2010
Thank you for your attention!
Hydraulic Engineering SectionBergische University of Wuppertal
Fon: +49 202 439 4195Fax: +49 202 439 4196
Conclusion and outlook
• Physical model shows water surface elevations and influences of arranged boulders
• modified drag coefficients have been analyzed
• future investigations deal with forces on boulders and their achieved drag coefficients under consideration of pressure based approaches
Introduction
Physical Model
Results
Conclusion
