http://www.eqstar.orghttp://www.syracusecoe.org

http://www.eqstar.orghttp://www.syracusecoe.org

Task 2CTask 2CComputation of Transport in PMEComputation of Transport in PME

I. Flow and Pollutant TransportI. Flow and Pollutant TransportChris Sideroff

Thong Dang

July 26, 2006

SAC 07/26-27/06 - 2

“Better” IAQ“Better” IAQ

P.O. Fanger, SU June 06 “Healthy Indoor Air, i.e. complete well being, requires more than 20 times

higher IAQ” “A paradigm shift is required”

For high IAQ need to address: Source control Air-cleaning Personal ventilation

Fanger SU Lecture June 2006

Fanger: “Improve quality of breathed air by factor of 10”

SAC 07/26-27/06 - 3

OverviewOverview

Ventilation systems other than the mixing type (e.g. personal, displacement), flow/contaminant gradients are important – cannot use “well-mixed” assumption

Flow/contaminant gradients near manikin are important if prediction of human exposure to contaminants is of interest

Topp et al. 2002

Personal Micro-Environment (PME): region around person which affects her/his breathed air – PME not a well-mixed environment

Interaction of the PME and surrounding environment is a complicated problem and requires accurate tools to tackle it => Task 2

“… when interested in the local air movements around occupants, the results show that a more detailed CSP should be applied as the local velocities were found to be different for the two CSP investigated.” They go on to say “… the local flow plays a role in the transport of contaminants to and from the breathing zone and, thus, the personal exposure”

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ApproachApproach

CFD is a potentially efficient (fast/inexpensive) and flexible tool because of advancements in CFD methodologies (modeling of complex geometry and transient problems, advanced RANS turbulence models and LES models) and computing hardware (e.g. parallel computing clusters)

Accuracy of CFD? Determine whether RANS/LES CFD is capable of characterizing/ assessing the PME EPA02

Develop procedures/guidelines to use CFD for PME EPA02 Use CFD to increase fundamental knowledge of PME (and IAQ) and

as a design tool when theory and/or experiments can not be applied => EPA03

Characterize and assess IAQ (PME) using Computational Fluid Dynamics

SAC 07/26-27/06 - 5

CollaborationCollaboration

Task 2C Detailed CFD

Task 1 Source Char.

Task 2A Resusp. Exp.

Task 2B Detailed Exp.

Task 5A PEL Exp.

Provide Gaseous Conc. for BC’s

Enhanced Validation and PM measurement

Provide PM Conc. For BC’s

Provide Guidelines for PEL CFD

SAC 07/26-27/06 - 6

Current State-of-the-ArtCurrent State-of-the-Art

In open literature, grid resolutions are typically on the order of a few hundred thousand (for 3D)

Traditional turbulence models zero-equation (mixing length) k- family

Single-point, omni-directional measurements velocity magnitude, no components no turbulence information (length scale, intensity) better error estimation

Steady-state if breathing, steady inhalation/exhalation no motion

Active research group at ASHRAE and Indoor Air – e.g. ASHRAE Chicago (Feb. 2006) Benchmark Symposium (Nielsen, Kato, Chen)

SAC 07/26-27/06 - 7

EPA03: Realistic ConditionsEPA03: Realistic Conditions

EPA02 - steady-state validation done Using validation guidelines proceed to assess exposure under more

realistic conditions Unsteady breathing Head motion (rotation) Body motion (rotation) Foot motion (tapping)

Further validate CFD for realistic setups with T2B (body rotation) Some important consequences

Difference between exposure in these situations and those using steady-state assumption

Fundamental impact of these effects on the flow (e.g. thermal plume, origin of inhaled air, etc)

SAC 07/26-27/06 - 8

BreathingBreathing

Breathing is a transient process however a common assumption is to assume steady inhale or exhale

Important issues:1. Difference in exposure (gaseous contaminant) – is the steady assumption

sufficient?

2. Origin of breathed air – this information could help design of PME Model the breathing cycle with a sinusoidal curve

-1

-0.5

0

0.5

1

0 1 2 3 4 5

Time (s)

Velo

cit

y (

m/s

)

Actual (Marr T2B)

Sinusoidal

SAC 07/26-27/06 - 9

BreathingBreathing

Breathing is a transient process however a common assumption is to assume steady inhale or exhale

Important issues: Origin of breathed air – could help in design strategies of PME

Air comes from in front of lower torso region – _not_ directly from feet

Gao & Nui 2004

Transient Breathing

Steady Inhalation

Origin of air: Stationary, Breathing Manikin Movie

SAC 07/26-27/06 - 10

BreathingBreathing

Breathing is a transient process however a common assumption is to assume steady inhale or exhale

Important issues: Difference in exposure (gaseous contaminant) – is the steady assumption

sufficient? Currently under investigation T1A (Zhang - Source characterization) provides information for

gaseous contaminant boundary conditions (concentration and/or flux)

Front-cutSide-cut

Emissions from clothing

SAC 07/26-27/06 - 11

45° Left22° Left

Rotating HeadRotating Head

People typically are not completely stationary for long periods of time Rotation of head mimics a person reading Important issues:

Origin of breathed air – how much does the motion affect where/what we breath?

Difference in exposure compared to 1) breathing alone 2) steady-state

45° Right 22° Right Centered

Breathing, Head Rotating Manikin Movie

SAC 07/26-27/06 - 12

Body RotationBody Rotation

Large scale motions of people my affect more than small breathing zone – e.g. person swiveling in an office chair

In parallel with T2B (Glauser) => enhanced validation Important issues

Does this type of motion disturb the room flow enough to create enhanced mixing, i.e. will it cause the transport of contaminants not otherwise possible?

Fundamental impact of these effects on the flow (e.g. thermal plume, origin of inhaled air, etc)

IFL T2B Setup

SAC 07/26-27/06 - 13

Foot MotionFoot Motion

The interaction of a foot approaching the floor has been shown (SU work by Khalifa and Elhadidi 2005) to be an important mechanism in particulate matter (PM) resuspension

Simulation of actual motion (rotation & translation) of 3D foot is beyond our capability therefore a model was created that can recreate the flow from a foot approaching a flat surface

We suspect the flow created by this interaction will be an important factor in transport of pollutants and PM (T2C Ahmadi) away from the floor and eventually into the breathing zone (T2B Higuchi)

Full 3D foot

Body-force Model

Axi-sym. 2D Piston

SAC 07/26-27/06 - 14

Foot MotionFoot Motion

Using the guidance of T2B (Higuchi - piston exp.) and CFD, momentum source constructed mimicking the external flow cause by a falling foot

Simulate transport of PM from falling foot – Boundary conditions for PM (loading and concentration) from T2A (Ferro)

SAC 07/26-27/06 - 15

Summary and Continuing WorkSummary and Continuing Work

Capturing the flow/contaminant gradients are important for PME, hence detailed CFD required

Realistic details of a person in their PME are important - Investigation on the impact of the transient details (breathing and motions) is currently in progress

Interaction and collaboration with others relevant tasks (T1A, T2A, T2B, T5A) critical for success of detailed simulations