TS/CV/DC CFD TeamTS/CV/DC CFD Team

Computational Fluid Dynamics at CERNComputational Fluid Dynamics at CERNMichele Battistin

CERN, Geneva - Switzerland

Outline of PresentationOutline of Presentation

• What is CERN?What is CERN?

• CFD at CERNCFD at CERN

- Team & Resources- Team & Resources

- Main Applications- Main Applications

• Casestudy ExamplesCasestudy Examples

- 2D Transient Study of ATLAS Detector- 2D Transient Study of ATLAS Detector

- 3D Steady-State Study of ALICE Detector- 3D Steady-State Study of ALICE Detector

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What is CERN?What is CERN?

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• European Organisation for Nuclear ResearchEuropean Organisation for Nuclear Research

• World’s largest physics centreWorld’s largest physics centre

• Provides physicists the necessary tools to Provides physicists the necessary tools to explore what matters is made of and what explore what matters is made of and what forces hold it togetherforces hold it together

• Founded in 1954, it includes now 20 member Founded in 1954, it includes now 20 member statesstates

• Current activities concentrate on the Current activities concentrate on the construction of a particle accelerator and construction of a particle accelerator and collider, the Large Hadron Collider (LHC) and collider, the Large Hadron Collider (LHC) and detector experiments for it.detector experiments for it.

How can we go back the time?How can we go back the time?

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15 Billions of years

5 Billions of years

1 Billion of years

330.000 years

100 seconds

0.1 Nanoseconds (10-10)

10-34 seconds

10-43 seconds

PS (’59)

LEP (’89)

LHC (’07)

ACCELERATOR ENERGY

Accelerators and DetectorsAccelerators and Detectors

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CFD at CERNCFD at CERN

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Team & ResourcesTeam & Resources• Part of the Technical Support Department, Cooling and Ventilation Part of the Technical Support Department, Cooling and Ventilation Group, Detector Cooling Section;Group, Detector Cooling Section;

• 3-5 young engineers 3-5 young engineers (PJAS, FELL, TechStud);

• standard PCs for pre and post processing;

• 20 Itanium® dual CPU 64 bit cluster connected with Infiniband®, Openlab (cern.ch/openlab), for parallel calculation (8 times faster since May 05);

• 116 licenses available.

Main ApplicationsMain Applications• Natural and Forced Convection Heat TransferNatural and Forced Convection Heat Transfer

• Air and Water Cooling SystemsAir and Water Cooling Systems

• Safety StudiesSafety Studies

• Gas and Humidity DistributionGas and Humidity Distribution

Casestudy 1Casestudy 1

2D Transient Simulation of the Thermal 2D Transient Simulation of the Thermal BehaviourBehaviour of the ATLAS Muon Chambers and Cavernof the ATLAS Muon Chambers and Cavern

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Casestudy 1 - PROBLEMCasestudy 1 - PROBLEM

The Muon Chambers and the Calorimeter dissipate a total of 80 kW of heat;

the cavern ventilation system: 60.000 m3/h of air at 17°C;

to improve the cooling, thermal screens at 20°C can be installed in the inner layer of sectors 3, 5 and 7;

for operational reasons, temperature and velocity gradients must be minimised in regions around the detector.

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3

5

7

OBJECTIVE: To find the temperature and flow distribution around the detector

Casestudy 1 – CFD MODELCasestudy 1 – CFD MODEL

2D, time dependent simulation;

only the air region is modelled;

convection assumed as main mode of heat transfer

turbulence flow: standard k-ε for low Re;

buoyancy effect;

heat sources defined as heat fluxes;

cavern ventilation system taken into account;

~230.000 non-uniform hexahedral cells.

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Casestudy 1 - RESULTSCasestudy 1 - RESULTS

predicted temperature and velocity fields will be used in a more detailed thermal study of the muon chambers to be performed by RFNC-VNIITF – LLC Strela, Snezhinsk, Russia www.cern.ch/cfd

Casestudy 2Casestudy 2

3D Steady-State Natural Convection Study of the 3D Steady-State Natural Convection Study of the ALICE Dipole MagnetALICE Dipole Magnet

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Casestudy 2 - PROBLEMCasestudy 2 - PROBLEM

The coils of the Dipole Magnet dissipate a total of 3.46 MW of heat by Joule effect;

a water cooling system is designed to extract this heat;

insulation of the coils is not sufficient to prevent heat transfer to the surrounding environment;

for operational reasons, temperature inside the magnet must be within a specified limit.

OBJECTIVE: To evaluate the overall heat loss from the coils, yoke and supports to air and the temperature

field around the magnet www.cern.ch/cfd

Casestudy 2 – CFD MODELCasestudy 2 – CFD MODEL

3D, steady-state simulation;

due to its symmetry, only half magnet was modelled;

buoyancy driven flow;buoyancy driven flow;

model included solid parts (yoke model included solid parts (yoke and supports) and the and supports) and the surrounding air volume. The surrounding air volume. The coils represented as empty coils represented as empty volumes;volumes;

temperature and suitable heat temperature and suitable heat resistance coefficients imposed resistance coefficients imposed on coils’ surfaces;on coils’ surfaces;

~~700.000 tetrahedral cells.700.000 tetrahedral cells.

Air

Yoke

Supports

Coil

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Casestudy 2 – RESULTSCasestudy 2 – RESULTS

a b ca b c

Air Temperature Distribution Around Magnet

Heat Lost, Heat Lost, kWkW

CoilsCoils SupportsSupports YokeYoke

ConvectionConvection 1.71.7 1.21.2 1.21.2

RadiationRadiation 1.41.4 0.40.4 -0.7-0.7

Total to AirTotal to Air

(half (half geometry)geometry)

3.13.1 1.61.6 0.50.5

Total Heat Dissipated by the Dipole Magnet = 10.4kW

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