TS/CV/DC CFD Team Computational Fluid Dynamics at CERN Michele Battistin CERN, Geneva - Switzerland

Outline of Presentation What is CERN? What is CERN? CFD at CERN CFD at CERN - Team & Resources - Main Applications Casestudy Examples Casestudy Examples - 2D Transient Study of ATLAS Detector - 3D Steady-State Study of ALICE Detector

What is CERN? European Organisation for Nuclear Research European Organisation for Nuclear Research World’s largest physics centre World’s largest physics centre Provides physicists the necessary tools to explore what matters is made of and what forces hold it together Provides physicists the necessary tools to explore what matters is made of and what forces hold it together Founded in 1954, it includes now 20 member states Founded in 1954, it includes now 20 member states Current activities concentrate on the construction of a particle accelerator and collider, the Large Hadron Collider (LHC) and detector experiments for it.Current activities concentrate on the construction of a particle accelerator and collider, the Large Hadron Collider (LHC) and detector experiments for it.

How can we go back the time? 15 Billions of years 5 Billions of years 1 Billion of years years 100 seconds 0.1 Nanoseconds ( ) seconds seconds PS (’59) LEP (’89) LHC (’07) ACCELERATOR ENERGY

Accelerators and Detectors

CFD at CERN Team & Resources Part of the Technical Support Department, Cooling and Ventilation Group, Detector Cooling Section; Part of the Technical Support Department, Cooling and Ventilation 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 Applications Natural and Forced Convection Heat Transfer Natural and Forced Convection Heat Transfer Air and Water Cooling Systems Air and Water Cooling Systems Safety Studies Safety Studies Gas and Humidity Distribution Gas and Humidity Distribution

Casestudy 1 2D Transient Simulation of the Thermal Behaviour of the ATLAS Muon Chambers and Cavern

Casestudy 1 - PROBLEM  The Muon Chambers and the Calorimeter dissipate a total of 80 kW of heat;  the cavern ventilation system: 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 OBJECTIVE: To find the temperature and flow distribution around the detector

Casestudy 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;  ~ non-uniform hexahedral cells.

Casestudy 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

Casestudy 2 3D Steady-State Natural Convection Study of the ALICE Dipole Magnet

Casestudy 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

Casestudy 2 – CFD MODEL  3D, steady-state simulation;  due to its symmetry, only half magnet was modelled;  buoyancy driven flow;  model included solid parts (yoke and supports) and the surrounding air volume. The coils represented as empty volumes;  temperature and suitable heat resistance coefficients imposed on coils’ surfaces;  ~ tetrahedral cells. Air Yoke Supports Coil

Casestudy 2 – RESULTS a b c a b c Air Temperature Distribution Around Magnet Heat Lost, kW CoilsSupportsYokeConvection Radiation Total to Air (half geometry) Total Heat Dissipated by the Dipole Magnet = 10.4kW