a comparative study of hec-ras 2d, tuflow, & mike 21 · a comparative study of hec-ras 2d,...
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A Comparative Study of HEC-RAS 2D, TUFLOW, & Mike 21
Model Benchmark Testing
Presented by:
Murari Paudel, PhD, PE, CFM
Soledad B Roman, EIT
John Prichard, PE, CFM
Wood Rodgers Inc. Sacramento, CA
June 2016
Acknowledgements
• Co-authors Soledad B Roman and John Prichard
• Hydrologic Engineering Center (HEC), Davis, CA
• BMT WBM, Australia
• DHI USA
• Water Resources Engineering Dept., Wood Rodgers Inc.
Presentation Overview
• Study Purpose
• Methodology and Limitations
• Test Cases
• Assessment of Results
• Conclusions
Study Purpose
• Benchmark TUFLOW (2016), MIKE21 (2014) and HECRAS 5.0.1 (2016)
• Test the models for a range of basic hydraulic conditions and model performance measures:
1. Hydraulic losses: Does the model scheme account for losses accurately?
2. Grid convergence: Does the model produce similar result for different cell sizes?
3. Simulation run time: Evaluate the simulation times for the different scenarios in each software
Methodology
• Create 3 simple test cases
1. Channel bend
2. Constriction
3. Flat bed (flood propagation)
• Run simulations for a range of flow conditions and cell sizes
– Number of scenarios = 280
• Different grid resolution and boundary conditions
1
2
3
Test Case – Bend Loss
• Objective: verify models estimate losses resulting from an abrupt bend
• Laboratory experiment (Malone 2008)
Test Case – Bend Loss
• Empirical equations from laboratory results
Bend – Model Configuration
• Scaled to match dimensions of laboratory test (Froude Model Law)
• 00, 45 and 90 degree scenarios
• 15ft grid resolution
• Free overfall conditions downstream boundary
• Same grid resolution across all three programs
• 12 computational nodes across the X-section
• Default parameters in all three programs
• Eddy Viscosity
– HECRAS 2D – Not used
– M21 and TUFLOW - Smagorinsky
• No Calibration effort
InflowBoundary
Downstream Boundary
12 grid cells15ftX15ft
A
Cross section A
Bend – Model Configuration
Base – 00 Degree
90 Degree Bend
45 Degree Bend
Bend – Model Configuration
• Water Surface Elevation and Flow velocity monitored at two location:
– Upstream of the bend – Point P1
– After the channel bends – Point P2
• Base condition (00- bend) is used to compute friction loss
• Hf-00 = WSEL at point1 – WSEL at point 2
Output Location P1
Output Location P2
hb-45 degree = (Head loss in 45 degree – Head loss in 00 degree)hb-90 degree = (Head loss in 90 degree – Head loss in 00 degree)
Velocity Profiles
HEC-RAS TUFLOW
Result: HECRAS 5.0.1
Result: TUFLOW
Result: MIKE21
Result: HEC-RAS, MIKE21 and TUFLOW
Bend Test Result Summary
• All models produced consistent results for various flows
– HEC-RAS 5.0.1 showed highest head loss among the three programs
– MIKE21 simulated head loss in between HEC RAS 2D and TUFLOW
– TUFLOW resulted in smallest head loss among the three
– All three programs exhibited higher head loss in 90 degree bend
• Runtime – 90 degree 36000cfs
HECRAS 5.0.1 (FM) = 41 mins 51 sec (8 Processors)
MIKE 21 = 35mins 44 sec (8 Processors)
TUFLOW = 22 mins 18sec (1 Processor)
Test Case – Constriction
• Objective:
– Verify models estimate losses resulting from a constriction (eg. bridge abutments)
– Assess grid convergence in model results
• Validated against Federal Highways Administration Equations (Bradley, 1978)
Constriction – Model Configuration
• Sudden contraction and expansion of flow path in a uniform rectangular channel
• 5ft and 10ft grid resolution.
• 11 flow scenarios (1000, 1200…. 3000cfs)
• Free overfall conditions downstream boundary
InflowBoundary
Downstream Boundary
Constriction – Model Configuration
Base – No Constriction
With Constriction
5ft grid cells
10ft grid cells
Constriction – Model Configuration
• Base condition (no constriction) is used to compute friction loss
• Eddy viscosity
– HEC-RAS 5.0.1 – Not used
– TUFLOW and Mike21 – Smagorinsky
• hL = WSEL at point1 – WSEL at point 2
Output Location P1
Output Location P3
hc degree = (Head loss in constriction – Head loss in base)= hL_cons – hL_base
Output Location P2
Velocity Profiles
HEC-RAS
TUFLOW
Mike21
Result: HECRAS 5.0.1
Result: TUFLOW
Result: MIKE21
Result: HEC-RAS, MIKE21 and TUFLOW
Constriction Test Result Summary
• HEC-RAS 2D (Full momentum), Mike21 and TUFLOW produced consistent and reasonable results
– The results from all of these programs are slightly different
– As compared to the loss computed using FHA equation:
• HECRAS 5.0.1 seems to slightly overestimated losses, results are closer to FHA on 5ft grid
• Mike21 matched the FHA results quite well with 5ft resolution grid and underestimates on 10ft grid
• TUFLOW simulated loss quite well with 5ft grid and slightly underestimated with 10 ft grid
– HECRAS 5.0.1 Diffusion wave method is not suggested in this kind of problem
• Runtime (5ft resolution)
HECRAS 5.0.1 = 2 hrs 54 minutes (8 Processors) -- Computation Time step = 0.1 s
MIKE 21 = 2 hrs 48 mins (8 Processors) -- Computation Time step = 0.1 s
TUFLOW = 21 min 31 seconds (1 Processor) -- Computation Time step = 0.4 s
Test Case – Speed of flood propagation
• Based on UK EPA benchmark test
• Objective: “test is to assess the package’s ability to simulate the celerity of propagation of a flood wave and predict transient velocities and depths”.
• Aim: Compare model simulation run time
• The model scenario size has been increased from UK version to make a better estimate of the model simulation time (50,000 cells)
Flood propagation – Model Configuration
• Flat bed
• 20m grid resolution
• 20m3/s inflow through a 20m opening
• 24hr simulation periodInflowBoundary 8000m
4000m
P2P1
Conclusions
• Model Results?
– Channel Bend Loss – All three software produce slightly different but consistent results
• HECRAS 5.0.1 produced highest head loss, MIKE21 less than HEC-RAS but slightly more than TUFLOW and TUFLOW produced the least head loss
– Channel Constriction – Consistent results across all the three software
• HECRAS 5.0.1 and MIKE21 produced slightly higher head lossas compared to TUFLOW
• Difference in head loss computed in three programs… Expected?
Conclusions
• Model Simulation Times?
– Is it an indicator of overall software efficiency?
– Parallel processing vs parallel simulations?
– Courant Criteria
• Other factors?
– Turbulence simulation (Kinematic viscosity)
– HEC-RAS 5.0.1 - Diffusive wave… Use with caution
– GIS data model compatibility
– Mapping and cartographic options
– Single simulation vs production job
– Pretty pictures/animations
• Which program to use among the three?
– All
Thank You
Murari Paudel, PhD, PE, CFM
Wood Rodgers Inc.
Sacramento, CA
(916) 341-7760