KJELD SVIDT, AALBORG UNIVERSITY

it.civil.auc.dk

CFD AND VIRTUAL REALITY FOR AIRFLOW VISUALISATION

Kjeld SvidtDept of Building Technology and Structural Engineering

Aalborg University

KJELD SVIDT, AALBORG UNIVERSITY

it.civil.auc.dk

Contents

BackgroundMethodsFacilitiesCasesResults and conclusions

KJELD SVIDT, AALBORG UNIVERSITY

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The IT in Civil Engineering groupat dept of Building Technology

• Professor Per Christiansson (1998) (former KBS-Media Lab, Lund University and the IT Bygg program in Sweden)

• Assistant Prof. Kjeld Svidt• PhD student Yoke-Chin Lai

KJELD SVIDT, AALBORG UNIVERSITY

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The IT in Civil Engineering group.Research areas and projects

• Virtual Buildings and Collaboration– ’Distributed Virtual Workspace for enhancing

Communication within the Construction Industry - DIVERCITY’ (EU IST)

– ’It in Collaborative Design’ (Danish Centre for Integrated Design, CID)

• Knowledge Nodes for Knowledge Transfer– (SERFIN, Merkurius, e-learning)

• Digital Cities and Intelligent Buildings

KJELD SVIDT, AALBORG UNIVERSITY

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CFD at dept of Building Technology- indoor environmental engineering group

Airflow in and around buildings Office buildings Industrial and livestock buildings Mechanical, natural and hybrid ventilation Thermal comfort Air quality Energy efficiency

KJELD SVIDT, AALBORG UNIVERSITY

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CFD Model of Incineration Hall, Amagerforbrænding

67 m

50 m

21 m

Displacement Ventilation SupplyCase C-D

Outdoor Air SupplyCase E-H

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Comparison between Calculated and Measured Results

- Amagerforbrænding

Vertical Plane at Incineration LineFillTemperature

52 oC46 oC40 oC34 oC28 oC22 oC16 oC10 oC

35o43o

34o

12-18o30-35o

53o

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Thermal manikins

Ref: Erik Bjørn

KJELD SVIDT, AALBORG UNIVERSITY

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Airborne transmission of respiratory disease between pig units located at close range (CEPROS) 1%

Ref: Bjarne Bjerg, KVL

KJELD SVIDT, AALBORG UNIVERSITY

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Airborne transmission of respiratory disease between pig units located at close range (CEPROS) 0.2%

Ref: Bjarne Bjerg, KVL

KJELD SVIDT, AALBORG UNIVERSITY

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Airborne transmission of respiratory disease between pig units located at close range (CEPROS) 0.1%

Ref: Bjarne Bjerg, KVL

KJELD SVIDT, AALBORG UNIVERSITY

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Test of VR in a specific project

Research project: “Control of Air Movement in Livestock Buildings”

... a joint research project between three Danish research groups:

The Royal Veterinary and Agricultural University, Department of Animal Science & Animal Health, Copenhagen, Denmark

Danish Institute of Agricultural Sciences, Department of Agricultural Engineering, Research Centre Bygholm, Horsens, Denmark

Aalborg University, Department of Building Technology and Structural Engineering, Aalborg, Denmark

KJELD SVIDT, AALBORG UNIVERSITY

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Why livestock buildings

Livestock production an important export industry in Denmark

Increased focus on working environment, indoor air quality, animal welfare

New housing types and production systems

New design tools such as Computational Fluid Dynamics

KJELD SVIDT, AALBORG UNIVERSITY

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The VR part of the project

One-day information seminar for professionals in the ventilation industry and consultants from the agricultural extension service.

For this seminar, a few cases reflecting research results as well as problem-cases from the industry were selected to be presented in the Virtual Reality facilities at Aalborg University.

Airflow was calculated with the commercial CFD-code Fluent version 5.5. Results were displayed with VU visualisation software (www.cerca.umontreal.ca/vu).

The results were displayed with active stereo in the panorama as well as the six-sided CAVE.

KJELD SVIDT, AALBORG UNIVERSITY

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What is Virtual Reality ?

Presentations that take place at the VR-Centre ?

Convincing your senses that something virtual is real

Realistic visualisation of phenomena which are difficult to see in reality (e.g. airflow)

KJELD SVIDT, AALBORG UNIVERSITY

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Virtual Reality may include the following elements:

Stereo viewing (different pictures for right and left eye)• Passive (polarized or colour filter)• Active (shutter glasses)

A certain degree of immersion• Wide screens, power walls• Large curved screens • CAVE• Head mounted displays

Realtime interaction with the model/database• Mouse or keyboard• Tracking of persons or interaction devices• Haptic devices

KJELD SVIDT, AALBORG UNIVERSITY

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VR facilities at Aalborg University (1)

Onyx2 IR2(will be replaced by PC cluster 2003)

LightwaveMatrix-Hub

Cave

Panorama

3D Auditorium

KJELD SVIDT, AALBORG UNIVERSITY

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VR facilities at Aalborg University (2)

• Panorama– Ø 7.1m, 160°, H 3.5m– Mono & aktive stereo– 28 persons– Tracking

KJELD SVIDT, AALBORG UNIVERSITY

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VR facilities at Aalborg University (3)

• 6-sided CAVE– 2.5m x 2.5m x 2.5m– Back projektion– Aktive stereo– 1 person with tracking,

+ a few observers without tracking

KJELD SVIDT, AALBORG UNIVERSITY

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VR facilities at Aalborg University (4)

• Portable equipment– 2.5m x 3.5m – Portable projector and PC– Passive stereo– 30 persons +

KJELD SVIDT, AALBORG UNIVERSITY

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Cases selected for VR presentation in the project

1. 3D airflow in a laboratory set-up with an isothermal slot inlet

2. Airflow and CO2-concentrations in a laboratory set-up with 4 wall inlets and “pig simulators”

3. Simulation of displacement ventilation in a room with closed pen partitions

4. Airflow in a similar room with a low momentum ceiling inlet

5. Airflow in a room with a radial inlet device

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Inlet

Outlet

Y

2.98m2.80m

1.00m

0.20m0.40m

X

Z

Y´

0´ X´

Z´

a

3.00m

5.00m

0

8.50m

Inlet flap

Inlet wall

Case 1

3D airflow in a laboratory set-up with an isothermal slot inlet

Air inlet

Air exhaust

KJELD SVIDT, AALBORG UNIVERSITY

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Air velocity at different z-positions during 13 hours (5 min average) - 4.5 m from inlet, 0.2 m below ceiling - the flow changes occasionally between two semi-stable conditions - values seem to be mirrored between z = 0.5 m and z = 4.5 m

0

0.2

0.4

0.6

0.8

1

Ve

locity,

m/s

0 200 400 600 800 Time, minutes

z=4.5mz=0.5mz=2.5m

Measured at 0.2m from ceiling & x=4.5m

KJELD SVIDT, AALBORG UNIVERSITY

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Case 2

Airflow and CO2 concentration in a laboratory set-up with 4 wall inlets and “pig simulators”

Air inlet

Air exhaust

KJELD SVIDT, AALBORG UNIVERSITY

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Case 3 – 4

Low momentum airflow in a room with closed pen partitions

Air inlet

Air exhaust

KJELD SVIDT, AALBORG UNIVERSITY

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Case 5

Airflow in a room with a radial inlet device

Air inlet

Air exhaust

KJELD SVIDT, AALBORG UNIVERSITY

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Methods of flow visualisation

• The presenter could scale and position the model in the 3D environment

• He could drag filled contour planes and vector planes arbitrarily through the model

• In addition he could place or drag seed points for streamlines or animated particle tracks in an intuitive way by moving physically around in the model

KJELD SVIDT, AALBORG UNIVERSITY

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Results and Conclusions

The VR facilities proved to be very efficient to visualise the three-dimensional airflow for people with no special background in 3D modelling and fluid motion

Especially the CAVE gave a very persuasive experience of being inside a virtual room with a virtual airflow

It requires some experience to navigate in the models and to scale and position them in a suitable way in relation to the physical surroundings (the audience, the panorama screen, the walls of the CAVE etc.)