NEW LES CAPABILITY OF ADREA-HF Mr. Nektarios Koutsourakis 1 Dr. - - PowerPoint PPT Presentation

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NEW LES CAPABILITY OF ADREA-HF Mr. Nektarios Koutsourakis 1 Dr. - - PowerPoint PPT Presentation

Aug 25, 2022 1.33k likes •1.57k views

NEW LES CAPABILITY OF ADREA-HF Mr. Nektarios Koutsourakis 1 Dr. Alexander Venetsanos 2 Prof. John G. Bartzis 1 Mr. Ilias Tolias 2 1 University of West Macedonia Greece 2 NCSR Demokritos Greece Harmo 13 LES of ADREA-HF ADREA-HF CFD CODE

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SLIDE 1

Harmo 13 – LES of ADREA-HF

  • Mr. Nektarios Koutsourakis1
  • Dr. Alexander Venetsanos2
  • Prof. John G. Bartzis1
  • Mr. Ilias Tolias2

1 University of West Macedonia Greece 2 NCSR “Demokritos” Greece

NEW LES CAPABILITY OF ADREA-HF

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SLIDE 2

Harmo 13 – LES of ADREA-HF

ADREA-HF CFD CODE Constantly developing

  • Latest additions:

– LES (Large Eddy Simulation) – Parallel solver – Arbitrary number of species – Combustion – GUI pre and post processor (called EDes)

  • Advantages:

– Robust, powerful and general – Specialization in environmental applications – “ADREA + dispersion”: 29 hits in Scopus

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SLIDE 3

Harmo 13 – LES of ADREA-HF

ADREA-HF CFD CODE GUI environment for pre and post processing

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SLIDE 4

Harmo 13 – LES of ADREA-HF

ADREA-HF CFD CODE Post processing example with ADREA-HF GUI

Flow

C1 2*C1 Sources

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SLIDE 5

Harmo 13 – LES of ADREA-HF

LARGE EDDY SIMULATION Between 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

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Harmo 13 – LES of ADREA-HF

ENERGY CASCADE LES solves most of the turbulence

E(k) RANS: All modeled

Energy containing range Viscous subrange

: Kolmogorov scale

Inertial subrange

k=1/ =Re /l

k Solved from DNS Solved from LES

k=1/l

l : integral scale

3/4

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SLIDE 7

Harmo 13 – LES of ADREA-HF

ENERGY CASCADE LES solves most of the turbulence

E(k) RANS: All modeled u l

2

ln

Energy containing range E(k)=C k Viscous subrange

Very large scales range

: Kolmogorov scale

Universal equilibrium range

Inertial subrange

  • 5/3

2/3

k

k=1/ =Re /l

8 6l l /6 60

80% of energy 90% of dissipation

ln(k l ) Solved from DNS Solved from LES

k=1/l

l : integral scale

3/4

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SLIDE 8

Harmo 13 – LES of ADREA-HF

  • Filtered equations:
  • Smagorinsky model of the residual stress tensor

LES EQUATIONS AT ADREA-HF Compressible volume-filtered Navier-Stokes

( )

i i

u t x         ( ) ( ) ( )

l R i j ij ij i j i j

u u u p t x x x                 

p rT  

2

1 2 ; ( ) 2 3

R ij kk ij t ij t s ij ij

S C S S          

R ij i j i j

u u u u      

1 3 Cs=0.1

V   1 2

j i ij j i

u u S x x               2 2 3

l k ij ij ij k

u S x        

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Harmo 13 – LES of ADREA-HF

LES AT ADREA-HF Numerics

  • ADREA/SIMPLER algorithm
  • Central differences convection scheme
  • Solver: Parallel BiCGstab with parallel Schwarz
  • preconditioner. Speedup with 2 CPUs up to 1.7
  • 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.

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Harmo 13 – LES of ADREA-HF

LES Boundary and initial conditions

  • Initial conditions should also create turbulence

– “Vortex generator” may be needed – Simpler solution: big over-imposed disturbance

  • Boundary conditions should also retain turbulence

– Difficult to do explicitly – Simpler solution: cyclic BC

  • Near wall:

– Well-resolved LES requires z+=1 – “Wall-function”-type solutions for coarser grids

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SLIDE 11

Harmo 13 – LES of ADREA-HF

TEST CASES SETUP a) Channel flow

  • 1D fully-developed channel flow: the classic LES test

– DNS of Moser et al, 1999 Re = 8000 – 90000 cells – Cyclic BC – z+ = 1 – CFLmax < 0.3 – Cs = 0.065 – Mass flow correction to control Re – Time 50s = 160 passes Averaging from 20s

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Harmo 13 – LES of ADREA-HF

TEST CASES SETUP b) Street canyon

  • 2D street canyon: the most basic urban case

– Water channel of Li et al, 2009 Re = 12000 – 300000 cells – Cyclic BC: sequence of identical canyons – z+ = 1 – Time 1000s = 250H/U Averaging from 400s

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SLIDE 13

Harmo 13 – LES of ADREA-HF

FULLY DEVELOPED CHANNEL FLOW Pressure isosurfaces and velocity vectors

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Harmo 13 – LES of ADREA-HF

FULLY DEVELOPED CHANNEL FLOW Comparison with DNS and other LES

z/H Reynolds stress/u*2

0.5 1

  • 2

2 4 6 8 10 12 14 DNS u'u'/u*2 DNS w'w'/u*2 DNS v'v'/u*2 DNS u'w'/u*2 ADREA u'u'/u*2 ADREA w'w'/u*2 ADREA v'v'/u*2 ADREA u'w'/u*2 STAR-CD u'u'/u*2 STAR-CD w'w'/u*2 STAR-CD v'v'/u*2 STAR-CD u'w'/u*2

STAR-CD DNS ADREA

ln(z+) U+

2 4 6 5 10 15 20 DNS ADREA LES STAR-CD LES

STAR-CD DNS ADREA

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SLIDE 15

Harmo 13 – LES of ADREA-HF

STREET CANYON Canyon 1: Building width=2H. Real time movie

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Harmo 13 – LES of ADREA-HF

STREET CANYON Canyon 2: Building =1H. Comparison with exp.

U/Uref z/H

  • 0.4
  • 0.2

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1 1.2

x=0.25H

Experiment Li et al 2008 LES ADREA

u'/Uref z/H

0.05 0.1 0.15 0.2 0.25 0.2 0.4 0.6 0.8 1 1.2

Li et al Experiment ADREA LES Li et al fine-LES

x=0.25H

U profile near

upwind wall

u’ profile near

upwind wall

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Harmo 13 – LES of ADREA-HF

STREET CANYON Canyon 2: Building =1H. Comparison with exp.

U/Uref z/H

  • 0.4
  • 0.2

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1 1.2

x=0.25H W/Uref z/H

  • 0.2

0.2 0.2 0.4 0.6 0.8 1 1.2

x=0.25H W/Uref z/H

  • 0.2

0.2 0.2 0.4 0.6 0.8 1 1.2

x=0.75H w'/Uref z/H

0.05 0.1 0.15 0.2 0.25 0.2 0.4 0.6 0.8 1 1.2

x=0.75H u'/Uref z/H

0.05 0.1 0.15 0.2 0.25 0.2 0.4 0.6 0.8 1 1.2

Li et al Experiment ADREA LES Li et al fine-LES

x=0.25H w'/Uref z/H

0.05 0.1 0.15 0.2 0.25 0.2 0.4 0.6 0.8 1 1.2

x=0.25H U/Uref z/H

  • 0.4
  • 0.2

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1 1.2

x=0.75H u'/Uref z/H

0.05 0.1 0.15 0.2 0.25 0.2 0.4 0.6 0.8 1 1.2

x=0.75H

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Harmo 13 – LES of ADREA-HF

DISCUSSION LES of ADREA-HF is competitive

  • ADREA performs well against exps and other LESs
  • Channel: Cs correction needed near wall
  • General tendency of Reynolds stresses predicted
  • Canyon: Performance very close to fine-grid LES
  • Profiles similar shape to experimental ones
  • Experiment stronger vortex with more turbulence:

– In experiment vortex generators were used – In experiment 3D effects were present

  • RANS (not shown) was also good in these tests
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Harmo 13 – LES of ADREA-HF

CONCLUSIONS LES is not for everyday use

  • ADREA-HF has now tested LES
  • LES is not RANS++
  • LES orders of magnitude more expensive than RANS
  • Near wall treatment a key point for real-world cases
  • What now:

– Refine ADREA LES – Add and test more LES options

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Harmo 13 – LES of ADREA-HF

THE END … is also a beginning

For any suggestions: nk@ipta.demokritos.gr