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

mpaudel@woodrodgers.com

(916) 341-7760