Id 204 evaluation of adrea hf les against hydrogen release dispersion
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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 CODE dispersionConstantly 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 CODE dispersionADREA 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 CODE dispersionGUI 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 SIMULATION dispersionBetween 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 CASCADE dispersionLES 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-HF dispersionCompressible 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-HF dispersionAlternative 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-HF dispersionNumerics

  • 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 CASE dispersionHySafe 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 SETUP dispersionSimulation 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 SETUP dispersionGeometry, 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
RESULTS dispersionComparison 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
RESULTS dispersionVideo 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
RESULTS dispersionConcentration 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
RESULTS dispersionComparison 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
DISCUSSION dispersionSome 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 dispersionCs 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
DISCUSSION dispersionCs 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 EXAMINATION dispersionC 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
DISCUSSION dispersionA 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 EXAMINATION dispersionEvaluation 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
DISCUSSION dispersionRNG 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 dispersionAcceptable 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 dispersionLES 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 dispersion

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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