Post on 22-May-2018
KIT – Universität des Landes Baden-Württemberg undnationales Großforschungszentrum in der Helmholtz-Gemeinschaft
www.kit.edu
MODELLIERUNG VALIDIERUNG
Direct numericalsimulations(DNS)-TUD
RANS simulations
KIT-Univ.
u0
g q''
q''
Responsible: R. Stieglitz
LIMTECH A1: Thermo-hydraulic flow in a sudden expansion
� Motivation-Challenge-Aim� Infrastructure & preparatory work� Time planing
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A1: Thermo-hydraulic flow in a sudden expansion
Motivation
� in- and outflow of thermal storage containers,� heat exchanger bundles, � manifolds & collectors in PCS� highly heat loaded surfaces (CSP, ….) � Reliable CFD model badly needed
Challenges
� scale separation of thermal-viscous boundary layers� Different statistics of flow and thermal field� multi-scale flow structure � buoyancy � anisotropic turbulence� non-standard situation: liquid metal
Aim
� Reliable description of TH performance in different flow regimes � development of adequate numeric design tools
q
q
CSP reveiver
Receiver
collectormanifold
distributor
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FOCUS
� validity limits of model assumptions
� Model development & validation (anisotropy momentum, heat flux)for LM
Benchmark experiment
KIT
Direct numerical
simulations (DNS)-
TUD
RANS
Simulations
KIT-Univ.
A1: Thermo-hydraulic flow in a sudden expansion
T=const.
Trifold strategy�Benchmark experiment in simple geometry ����backward facing step (BFS) �data
�RANS simulation (industrial approach)� anisotropic turbulence modelling
for industrial application� identification of limitations
�DNS simulation� reference data for RANS � transition regimes
(laminar � turbulent, buoyant � mixed � forced convection)
u0
a
u0
h
g q, T
q, T
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Work plan
� WP1: Preparatory Phase (all Partners)
� WP2: RANS simulations /modeling (KIT-FSM)
� WP3: DNS, LES, Hybrid modeling and simulations (TUD)
� WP4: Experiment @ KASOLA facility (KIT)
� WP5: Flow field analysis (all Partners)
Know how & role of Partners
� KIT KASOLA: Liquid metal know how, design & experiment (1 Sci.)
� KIT –FSM: RANS simulation& modeling (1 PhD)
� TUD: LES, DNS & Hybrid modeling & simulation (1 PhD)
Link to other subprojects
� Young investigator group for measurement techniques
� B1 (transitional flows), B2 (solar apps), B4 (PCS) and C3 (LIMMCAST)
A1: Thermo-hydraulic flow in a sudden expansion
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Prototypic Benchmark: Vertical Backward Facing Step
� stratification problem (buoyancy) at large axial ∆T
� flow separation at geometry discontinuities� challenging experiment with liquid metal
Approach
� Here small Pr-Fluid(PrSodium=0.007)
� LES u-Field
� + DNS of T-Field
Measurement
� Velocity - Pitot-tube
� Thermocouples
Conditions:
Re=104, T =310°C=const,Tin=260°C
a=60mm, l=50a, h=1/4a
aa
u0
h
g q''
q''
A1: Thermo-hydraulic flow in a sudden expansion
T=const.
u0
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KASOLA: Plant
Na-Air HX
Cold trap
Na tank
MHD pump
Solar storage tank H
~ 1
2 m
Expansion tank
Test pool
Versatile test circuit
R&D Focus
� liquid metal (LM) systems for transmutation
� Accelerator target development
� Studies of LM for solar applications
� Development of turbulent LM heattransfer models for CFD tools
KEY DATA
� Heating power: ~ 800 kW
� Temperature range: 150°-550°C
� Maximum flow rate: 150 m3/h
� Sodium inventory : 7m3
� Tent. Start-up: 2/3 Quarter2013
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CURRENT STATUS
� Design, development & build-up of the KASOLA loop (Hering et al.)
� Components in house (purchased, manufactured)
� Loop concept certified by in principal technical survey
� Safety concept elaborated and safety report existent (to be completed in minor parts by the pre-requisites of the TÜV)
� Development of a KASOLA model with TRACE to estimate the required thermal load (Homann, Jäger)
� Hydraulic evaluation of KASOLA with numerical methods (Onea, Homann)
� Design, optimization of KASOLA components, e.g. cold trap, with CFD (Onea)
� Improvement of the system code TRACE for thermal-hydraulic investigations of Na flow (Jaeger)
SPECIFIC project related work
� Evaluation of preliminary isothermal tests in air strand (A1 -Jäger…..)
� Set-up of small loop (Na; In-Ga-Sn, B1) for preliminary investigations (W. Jaeger
+ Student),
KASOLA
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CURRENT STATUS- Simulation work
� DNS computations by TUD started
� Turbulent LM Heat transfer RANS-LES modelling at KIT (FSM/ISL) revisited
� Development of a turbulent Prandtl number approach Prt = f(y+, Re, Pr) for CFD (M. Boettcher)
� Evaluation of the instrumentation ( ongoing Jianu )
KASOLA
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CFD-Simulation @TUD :backward-facing step
Spectral-Element & Fourier-Method
12.5 Mio nodes
electro-magneticactuator
1870 =HRe
laminar
inflow
)sin(),,( tzyxff L ω=
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� Momentum field
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no forcing sinusoidal forcing
� Momentum field
Simulation: Flow with forcing
� iso-surface = λ2 criterion
� color = stream-wise velocity
CFD-Simulation @TUD :backward-facing step
Result: � Use of actuator reduces separation
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Analysis of DNS-Data of a Poiseulle duct flow (Kawamura et. al.)
RANS-Model: HFM
Dimensionless quantities
CFD-Simulation @KIT : advanced turbulent heat flux modeling
� Temperature field
flow direction
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� Low Pr extension requires modified damping term of pressure dissipation
CFD-Simulation @KIT : advanced turbulent heat flux modeling
� Temperature field
© PhD Baumann 2012
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CFD-Simulation @KIT : advanced turbulent heat flux modeling
� Temperature field
© PhD Baumann 2012
LES: 6.4 Mio. CellsFine structure model: dyn. Smagorinksi-Model
DNS-Data of Chung, [2002]
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Isothermal Pre-testing of BFS-geometry
Idea1:1 representation of geometry, Re-analogyOptical access to flow field (u,u‘)Elaboration of critical measurementpositions complementary to CFD results
GoalOptimization of inflow conditioningGeometry optimizationWell defined CFD-boudary conditions L-STAR/SL
L-STAR/LLLDA
PIV / LIF