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[ID 204] Evaluation of ADREA-HF LES against Hydrogen release dispersion. Mr. Nektarios Koutsourakis 1,2 Dr. Alexander Venetsanos 2 Prof. John G. Bartzis 1 4th International Conference on Hydrogen Safety San Francisco, California, September 12-14, 2011 1 University of West Macedonia Greece

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id 204 evaluation of adrea hf les against hydrogen release dispersion
[ID 204] Evaluation of ADREA-HF LES against Hydrogen release dispersion

Mr. Nektarios Koutsourakis1,2

Dr. Alexander Venetsanos2

Prof. John G. Bartzis1

4th International Conference on Hydrogen Safety

San Francisco, California, September 12-14, 2011

1 University of West Macedonia Greece

2 NCSR “Demokritos” Greece

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

adrea hf cfd code constantly developing
ADREA-HF CFD CODEConstantly developing
  • Latest additions:
    • LES (Large Eddy Simulation)
    • Parallel solver
    • Arbitrary number of species
    • Combustion
    • Back tracking
    • GUI pre and post processor (called EDes)
  • Advantages:
    • Robust, powerful and general
    • Specialization in environmental applications

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

adrea hf cfd code adrea specializes in dispersion applications
ADREA-HF CFD CODEADREA specializes in dispersion applications

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

adrea hf cfd code gui environment for pre and post processing
ADREA-HF CFD CODEGUI environment for pre and post processing

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

large eddy simulation between dns and rans
LARGE EDDY SIMULATIONBetween DNS and RANS
  • Navier-Stokes math. analysis: impossibly difficult
  • DNS: Fully-resolved NS
    • Cost Re2.75 (for wall-bounded flows  Re3.5)
  • RANS: Time-averaged NS
    • Fast, widely tested, usually accurate “enough”
  • LES: Spatially-filtered NS
    • Cost near wall: Re2.4 ! (at outer layer  Re0.5)
    • Converges to DNS. As in DNS, LES needs:a) averaging b) demanding boundary conditions
    • Suggested were RANS fails: transient, separated flow

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

energy cascade les solves most of the turbulence
ENERGY CASCADELES solves most of the turbulence

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

les equations at adrea hf compressible volume filtered navier stokes
LES EQUATIONS AT ADREA-HFCompressible volume-filtered Navier-Stokes

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

les equations at adrea hf alternative subgrid model rng les
LES EQUATIONS AT ADREA-HFAlternative subgrid model: RNG-LES

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

les at adrea hf numerics
LES AT ADREA-HFNumerics
  • ADREA/SIMPLER algorithm
  • Solver: Parallel BiCGstab with parallel Schwarz preconditioner. Speedup with 2 CPUs up to 1.7
  • Numerics:
    • Deferred correction central scheme for convection
    • Crank-Nicolson 2d order for time advancement
    • Linear upwind with VanLeer limiter for concentration
  • For more:
    • Venetsanos, A. G., E. Papanikolaou and J. G. Bartzis, 2010: The ADREA-HF CFD code for consequence assessment of hydrogen applications. Int. J. Hydrogen Energy, 35, 3908.

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

test case hysafe ineris 6c experiment
TEST CASEHySafe INERIS-6Cexperiment
  • 1g/s H2 for 240s
  • Jet 20mm
  • Room 3.78 * 7.2 * 2.88m

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

test case setup simulation details
TEST CASE SETUPSimulation details
  • Standard Smagorinsky with Cs=0.1
  • Total number of cells in the room: 130000
  • CFLmax=0.3
  • Minimum mesh resolution: 0.02*0.02*0.053 m
  • Simulation time in a workstation:15 days for the release phase (240s); dtav1= 0.0005s+ 2 days for the first 260s of the post-release phase

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

test case setup geometry sensors part of the grid
TEST CASE SETUPGeometry, sensors, part of the grid

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

results comparison with experiment
RESULTSComparison with experiment

Photo fromexperiment

ADREALES

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

results video of the hydrogen propagation
RESULTSVideo of the Hydrogen propagation

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

results concentration contours animation
RESULTSConcentration contours animation

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

results comparison with sensors
RESULTSComparison with sensors

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

discussion some remarks
DISCUSSIONSome remarks
  • In general very good agreement
  • High turbulence during release phase, only
  • Release overestimated, especially near source.Very difficult for CFD and for turbulence modelling to capture the physical processes next to the source
  • Diffusion underestimated (possible experimental asymmetry?) - improvement with better grid
  • Better agreement is prevented from experimental inaccuracies and numerical discrepancies

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

further examination cs value influence release phase coarse grid
FURTHER EXAMINATION Cs value influence (release phase -coarse grid)

Jet axis sensors

Ceilingsensors

Side wall sensors

Sensor 16

Sensor 14

Sensor 13

Sensor 1

Sensor 4

Sensor 6

Sensor 7

Sensor 8

Sensor 9

Sensor 10

Sensor 12

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

discussion cs affects the results
DISCUSSIONCs affects the results
  • Cs (SGS modelling in general) important near jet
  • At the ceiling, no Cs influence (buoyancy dominates)
  • Non-monotonic behaviour (increasing the Cs gives better results, but up to a limit)
  • Worst Cs by far: 0.2

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

further examination c variances for each cs
FURTHER EXAMINATIONC variances for each Cs

C variance = mean (Ci’2)

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

discussion a critical balance resolved vs sgs turbulence
DISCUSSIONA critical balance: resolved vs. SGS turbulence
  • As we go away from the jet, variance (and resolved turbulence intensity) drops
  • Two mechanisms compete:- Modelled SGS turbulence- Resolved turbulence (generally low if SGS is high)
  • With Cs=0.2, very high artificial viscosity causes more “laminar” flow and lower fluctuations

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

further examination evaluation of rng les run not finished yet
FURTHER EXAMINATIONEvaluation of RNG-LES (run not finished yet)

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

discussion rng les seems to be an improvement
DISCUSSIONRNG LES seems to be an improvement
  • RNG LES provides in general better results
  • Improvement towards the right side for sensors both close to the jet (turbulent flow) and far from it (laminar flow). That was not the case by varying Cs
  • Resolved turbulence seems to decrease close to the jet and increase far from it
  • RNG LES is believed to better model the subgrid scales for both the turbulent and the laminar flow

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

conclusions i acceptable results and physical insight
CONCLUSIONS I Acceptable results and physical insight
  • LES results are good, given all numerical and experimental inaccuracies
  • Overestimation during release phase (close to jet)
  • Underestimation during diffusion phase (and far from jet)
  • Attempt to investigate the balance between resolved and SGS turbulence with parametric analysis of Cs
  • RNG LES seems to behave slightly better in both turbulent and laminar parts of the flow

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

conclusions ii les is good but not for everyday use
CONCLUSIONS II LES is good, but not for everyday use
  • ADREA-HF has now tested LES in hydrogen release
  • LES can provide peak concentrations (good for flammable mixtures or for calculation of dosages)
  • LES can provide concentration statistics
  • LES many times more expensive than RANS
  • LES is not RANS++

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

thank you
THANK YOU

Acknowledgements: Greek Scholarships Foundation, Municipality of Aghia Varvara

ICHS 2011, #204 LES MODELLING OF HYDROGEN RELEASE AND ACCUMULATION WITHIN A NON-VENTILATED AMBIENT PRESSURE GARAGE USING THE ADREA-HF CFD CODE

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