We report a computational fluid dynamics (CFD) study of containment of airborne hazardous materials in a ventilated room containing a downdraft table. Specifically, we investigate the containment of hazardous airborne material obtainable under a range of ventilation configurations. The desirable ventilation configuration should ensure excellent containment of the hazardous material released from the workspace above the downdraft table. However, increased airflow raises operation costs, so the airflow should be as low as feasible without compromising containment. The airflow is modeled using Reynolds Averaged Navier Stokes equations with a high Reynolds number k-epsilon turbulence model. CFD predictions are examined for several ventilation configurations. Based on this study, we find that substantial improvements in containment are possible concurrent with reduction in airflow, compared to the existing design of ventilation configuration.

10aairflow and pollutant transport group10acfd modeling10acontamination control10adowndraft table10aindoor airflow and pollutant transport10aindoor environment department10aventilation1 aJayaraman, Buvaneswari1 aKristoffersen, Astrid, H.1 aFinlayson, Elizabeth, U.1 aGadgil, Ashok, J. uhttps://energyanalysis.lbl.gov/publications/cfd-investigation-room-ventilation02156nas a2200289 4500008004100000245013700041210006900178300001400247490000700261520112300268653004201391653001001433653004301443653003401486653003201520653002101552653002101573100002701594700002901621700002201650700002401672700002301696700002001719700002401739700002201763856008101785 2006 eng d00aTracer Gas Transport under Mixed Convection Conditions in an Experimental Atrium: Comparison Between Experiments and CFD Predictions0 aTracer Gas Transport under Mixed Convection Conditions in an Exp a5236-52500 v403 aWe compare computational fluid dynamics (CFD) predictions using a steady-state Reynolds Averaged Navier-Stokes (RANS) model with experimental data on airflow and pollutant dispersion under mixed-convection conditions in a 7 x 9 x 11m high experimental facility. The Rayleigh number, based on height, was O(1011) and the atrium was mechanically ventilated. We released tracer gas in the atrium and measured the spatial distribution of concentrations; we then modeled the experiment using four different levels of modeling detail. The four computational models differ in the choice of temperature boundary conditions and the choice of turbulence model. Predictions from a low-Reynolds-number k- model with detailed boundary conditions agreed well with the data using three different model-measurement comparison metrics. Results from the same model with a single temperature prescribed for each wall also agreed well with the data. Predictions of a standard k- model were about the same as those of an isothermal model; neither performed well. Implications of the results for practical applications are discussed.

10aairflow and pollutant transport group10aatria10aindoor airflow and pollutant transport10aindoor environment department10aindoor pollutant dispersion10amixed convection10aturbulence model1 aJayaraman, Buvaneswari1 aFinlayson, Elizabeth, U.1 aSohn, Michael, D.1 aThatcher, Tracy, L.1 aPrice, Phillip, N.1 aWood, Emily, E.1 aSextro, Richard, G.1 aGadgil, Ashok, J. uhttps://energyanalysis.lbl.gov/publications/tracer-gas-transport-under-mixed01760nas a2200265 4500008004100000245009400041210006900135260004600204300001400250490000900264520088000273653001201153653000801165653002301173653002101196653002501217100002701242700002901269700002001298700002401318700002301342700002401365700002201389856008301411 2005 eng d00aComparison between experiments and CFD predictions of mixed convection flows in an atrium0 aComparison between experiments and CFD predictions of mixed conv aBeijing, ChinabTsinghua University Press a2849-28530 v3(3)3 aThis paper compares results from a computational fluid dynamics (CFD) simulation of airflow and pollutant dispersion under mixed-convection conditions with experimental data obtained in our 7m x 9m x 11m high experimental facility. A tracer gas was continuously released from a 1 m^{2} horizontal source 0.5 m above the floor. Path-integrated concentrations were measured along multiple short and long sampling paths in three horizontal planes. A steady state CFD analysis was used to model these experiments. The Reynolds Averaged Navier-Stokes (RANS) equations were solved for the flow and temperature field using the commercial CFD software, StarCD. CFD results were compared with the measured path-integrated concentrations. Accuracy of CFD predictions was found to improve with inclusion of thermal effects, and further by using a low-Re turbulence model.

This paper reports a computational fluid dynamics (CFD) study on containment of airborne hazardous materials in a ventilated room containing a downdraft table. Specifically, we investigated the containment of hazardous airborne material under a range of ventilation configurations. The desirable ventilation configuration should ensure excellent containment of the hazardous material released from the workspace above the downdraft table. However, increased airflow raises operation costs, so the airflow should be as low as feasible without compromising containment. The airflow was modeled using Reynolds Averaged Navier Stokes equations with a high Reynolds number k-epsilon turbulence model using the commercial CFD code StarCD. CFD predictions were examined for several ventilation configurations. Based on this study, we found that substantial improvements in containment were possible with a significant reduction in airflow, compared to the existing ventilation configuration.

10aairflow and pollutant transport group10acfd modeling10acontamination control10adowndraft table10aindoor airflow and pollutant transport10aindoor environment department10aventilation1 aJayaraman, Buvaneswari1 aKristoffersen, Astrid, H.1 aFinlayson, Elizabeth, U.1 aGadgil, Ashok, J. uhttps://energyanalysis.lbl.gov/publications/investigation-room-ventilation02021nas a2200157 4500008004100000245016500041210006900206300001200275490000700287520138800294100002901682700002201711700002401733700002401757856008201781 2004 eng d00aPollutant Dispersion in a Large Indoor Space Part 2 -- Computational Fluid Dyamics (CF) Predictions and Comparisons with a Model Experiment for Isothermal Flow0 aPollutant Dispersion in a Large Indoor Space Part 2 Computationa a272-2830 v143 aThis paper reports on an investigation of the adequacy of Computational fluid dynamics (CFD), using a standard Reynolds Averaged Navier Stokes (RANS) model, for predicting dispersion of neutrally buoyant gas in a large indoor space. We used CFD to predict pollutant (dye) concentration profiles in a water filled scale model of an atrium with a continuous pollutant source. Predictions from the RANS formulation are comparable to an ensemble average of independent identical experiments. Model results were compared to pollutant concentration data in a horizontal plane from experiments in a scale model atrium. Predictions were made for steady-state (fully developed) and transient (developing) pollutant concentrations. Agreement between CFD predictions and ensemble averaged experimental measurements is quantified using the ratios of CFD-predicted and experimentally measured dye concentration at a large number of points in the measurement plane. Agreement is considered good if these ratios fall between 0.5 and 2.0 at all points in the plane. The standard k-epsilon two equation turbulence model obtains this level of agreement and predicts pollutant arrival time to the measurement plane within a few seconds. These results suggest that this modeling approach is adequate for predicting isothermal pollutant transport in a large room with simple geometry.

1 aFinlayson, Elizabeth, U.1 aGadgil, Ashok, J.1 aThatcher, Tracy, L.1 aSextro, Richard, G. uhttps://energyanalysis.lbl.gov/publications/pollutant-dispersion-large-indoor01624nas a2200145 4500008004100000245004100041210004100082260001200123520115300135100002901288700002701317700003001344700002201374856008201396 2003 eng d00aCFD Analysis of LLNL Downdraft Table0 aCFD Analysis of LLNL Downdraft Table c10/20033 aThis study examines the airflow and contaminant transport in an existing room (89"x77"x98") that houses a downdraft table at LLNL. The facility was designed and built in the 1960's and is currently being considered for redesign. One objective of the redesign is to reduce airflow while maintaining or improving user safety. Because this facility has been used for many years to handle radioactive material it is impractical to conduct extensive experimental tests in it. Therefore, we have performed a Computational Fluid Dynamic (CFD) analysis of the facility. The study examines the current operational condition and some other cases with reduced airflow. Reducing airflow will lead to savings in operating costs (lower fan power consumption), and possible improvements in containment from reduced turbulence. In addition, we examine three design (geometry) changes. These are: (1) increasing the area of the HVAC inlet on the ceiling, (2) adding a 15° angled ceiling inlet and (3) increasing the area of the slot in the doorway. Of these three geometry modifications, only the larger doorway slot leads to improved predicted containment.

1 aFinlayson, Elizabeth, U.1 aJayaraman, Buvaneswari1 aKristoffersen, Astrid, H.1 aGadgil, Ashok, J. uhttps://energyanalysis.lbl.gov/publications/cfd-analysis-llnl-downdraft-table01963nas a2200181 4500008004100000022001500041245009000056210006900146260001200215300001400227490000700241520135900248100002201607700002501629700002101654700002901675856007701704 2003 eng d a1352-2310 00aIndoor Pollutant Mixing Time in an Isothermal Closed Room: An investigation using CFD0 aIndoor Pollutant Mixing Time in an Isothermal Closed Room An inv c12/2003 a5577-55860 v373 aWe report computational fluid dynamics (CFD) predictions of mixing time of a point pulse release of a pollutant in an unventilated mechanically mixed isothermal room. The aims of the study are to determine (1) the adequacy of the standard RANS two-equation (*k-ℇ*) turbulence model to predict the mixing times under these conditions, and (2) the extent to which the mixing time is a feature of the room airflow, rather than the source location within the room. CFD simulations modeled the twelve mixing time experiments performed by Drescher et al. (1995) in an isothermal sealed room for a point pulse release. Predictions of mixing time were found in good agreement with experimental measurements, over an order of magnitude variation in blower power. Additional CFD simulations were performed to investigate the relation between pollutant mixing time and pollutant source location. Seventeen source locations were investigated for five different blower power configurations in the room. Results clearly show large dependence of the mixing time on the room airflow, with some dependence on source location. We further explore dependence of mixing time on the local airflow properties (velocity and turbulence intensity) at the source location. Implications for our findings for positioning air-toxic sensors in rooms are also discussed.

This report presents advice on how to operate a building to reduce casualties from a biological or chemical attack, as well as potential changes to the building (e.g. the design of the ventilation system) that could make it more secure. It also documents the assumptions and reasoning behind the advice. The particular circumstances of any attack, such as the ventilation system design, building occupancy, agent type, source strength and location, and so on, may differ from the assumptions made here, in which case actions other than our recommendations may be required; we hope that by understanding the rationale behind the advice, building operators can modify it as required for their circumstances. The advice was prepared by members of the Airflow and Pollutant Transport Group, which is part of the Indoor Environment Department at the Lawrence Berkeley National Laboratory. The group's expertise in this area includes: tracer-gas measurements of airflows in buildings (Sextro, Thatcher); design and operation of commercial building ventilation systems (Delp); modeling and analysis of airflow and tracer gas transport in large indoor spaces (Finlayson, Gadgil, Price); modeling of gas releases in multi-zone buildings (Sohn, Lorenzetti, Finlayson, Sextro); and occupational health and safety experience related to building design and operation (Sextro, Delp). This report is concerned only with building design and operation; it is not a how-to manual for emergency response. Many important emergency response topics are not covered here, including crowd control, medical treatment, evidence gathering, decontamination methods, and rescue gear.

1 aPrice, Phillip, N.1 aSohn, Michael, D.1 aGadgil, Ashok, J.1 aDelp, William, W.1 aLorenzetti, David, M.1 aFinlayson, Elizabeth, U.1 aThatcher, Tracy, L.1 aSextro, Richard, G.1 aDerby, Elisabeth, A.1 aJarvis, Sondra, A. uhttps://energyanalysis.lbl.gov/publications/protecting-buildings-biological-or00884nas a2200229 4500008004100000245013100041210006900172260006100241100002200302700002900324700002200353700002300375700002400398700002300422700001900445700001600464700002500480700002200505700002000527700002400547856008300571 2000 eng d00aPollutant transport and dispersion in large indoor spaces: A status report for the large space effort of the Interiors Project0 aPollutant transport and dispersion in large indoor spaces A stat aBerkeleybLawrence Berkeley National Laboratoryc06/20001 aGadgil, Ashok, J.1 aFinlayson, Elizabeth, U.1 aFischer, Marc, L.1 aPrice, Phillip, N.1 aThatcher, Tracy, L.1 aCraig, Mathias, J.1 aHong, Ki-Hyuck1 aHousman, J.1 aSchwalbe, Carrie, A.1 aWilson, David, J.1 aWood, Emily, E.1 aSextro, Richard, G. uhttps://energyanalysis.lbl.gov/publications/pollutant-transport-and-dispersion