Schindfessel large eddy simulations of an open-channel confluence
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L. Schindfessel, S. Creëlle & T. De Mulder Hydraulics Laboratory – Department of Civil Engineering – Ghent University Large-eddy simulation of a laboratory confluence L. Schindfessel, S. Creëlle & T. De Mulder
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Transcript of Schindfessel large eddy simulations of an open-channel confluence
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
Large-eddy simulation of a laboratory
confluence
L. Schindfessel, S. Creëlle & T. De Mulder
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
Open-channel confluences
After Best, J. (1985): Flow dynamics and sediment transport at river channel confluences. Ph.D. thesis,
University of London, BirkBeck college.
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
Open-channel confluences
𝑞 =𝑄𝑚𝑄𝑑
=𝑄𝑚
𝑄𝑚 + 𝑄𝑡
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
Open-channel confluences
Source: The Internet
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
7
Confluence research @ UGent
Laurent Schindfessel
Extreme discharge ratios
Large-eddy simulation
Stéphan Creëlle
Mixing & head loss
Experiments
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
8
Research Question
To characterize (turbulent) flow patterns at a
confluence where the incoming discharges differ
more than an order of magnitude
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
9
Research Question
To characterize (turbulent) flow patterns at a
confluence where the incoming discharges differ
more than an order of magnitude
𝑞 =𝑄𝑚𝑄𝑑
=𝑄𝑚
𝑄𝑚 + 𝑄𝑡
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
10
Research Question
To characterize (turbulent) flow patterns at a
confluence where the incoming discharges differ
more than an order of magnitude
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
12
Large-Eddy Simulations (LES)
Spatially filtered Navier-Stokes equations,
whereby the small scale turbulence is removed.
Small-scale turbulence is modelled (Subgrid Scale
model, SGS).
Large-scale motions are resolved
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
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Large-Eddy Simulations (LES)
In the OpenFOAM toolbox
Wall-modelled, rigid lid, standard Smagorinsky
Mesh size about 1cm => 4,2 million cells
Parallel computing on 32 processors
90° confluence, 3 discharge ratios q
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
15
Validation Experiment
LES
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
18
Results
q = 0.25
q = 0.05
q = 0
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
19
Results
Schindfessel et al. (2015): Flow patterns in an open channel
confluence with increasingly dominant tributary inflow. Water,
7:9, 4724-4751.
q = 0.25
q = 0.05
q = 0
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
20
Results: TKE
q = 0.25
q = 0.05
q = 0
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
21
Results
q = 0.25
q = 0
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
22
Conclusions
Large eddy simulations have been used to
simulate the flow in a laboratory confluence
Discharge ratio is varied, corresponding to
increasingly dominant tributary inflow
Changes in flow patterns: impinging on opposing
wall, recirculating eddy
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
Thank you for your attention
Mail to: [email protected]
L. Schindfessel, S. Creëlle & T. De Mulder
Hydraulics Laboratory – Department of Civil Engineering – Ghent University
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Further Reading
Schindfessel et al. (2015): Flow patterns in an open channel confluence with increasingly dominant tributary
inflow. Water, 7:9, 4724-4751.
Creëlle, S.; De Mulder, T; Schindfessel, L; van Oyen, T. Influence of Hydraulic Resistance on Flow Features
in An Open Channel Confluence. In Proceedings of the 3rd IAHR Europe Congress, Porto, Portugal, 14–16
April 2014.
Schindfessel, L.; Creëlle, S.; Boelens, T.; De Mulder, T. Flow Patterns in An Open Channel Confluence with
A Small Ratio of Main Channel to Tributary Discharge. In River Flow 2014; Schleiss, et al. Eds.; Taylor &
Francis Group: London,UK, 2014; pp. 989–996.
Best, J.L. Flow Dynamics and Sediment Transport at River Channel Confluences. Ph.D. Thesis, University
of London, London, UK, 1985.
Mignot, E.; Vinkovic, I.; Doppler, D.; Riviere, N. Mixing layer in open-channel junction flows. Environ. Fluid
Mech. 2014, 14, 1027–1041.
Constantinescu, G.; Miyawaki, S.; Rhoads, B.; Sukhodolov, A. Numerical analysis of the effect of
momentum ratio on the dynamics and sediment-entrainment capacity of coherent flow structures at a
stream confluence. J. Geophys. Res. 2012, 117, 1–21.
Stoesser, T. Large-eddy simulation in hydraulics: Quo vadis? J. Hydraul. Eng. 2014, 52, 441–452.
