A physical model of Buncefield – Progress Report - ukelg

MANUAL DE POLÍTICASAPLICABLES A LOS PROCEDIMIENTOSDirección de PersonalSeptiembre 20101 de 26

Experimental DesignSTEADY FEED -~ 4 cm~ 1 m/s1 meter• Reynolds Number• Froude Numberν = kinematic viscosity, m 2 /sg ’ = g((ρ – ρ air )/ ρ air ), m/s 2

Experimental DesignWind TunnelWorking Section• Length 80 ft• Width 20 ft• Height 7 ftLDVVelocityprobeFIDGasConc probe11 mSource Box1 m square6

Video Recording• Synchronized digital video capture of about 45 cm wideside-on views of flow (visualized with smoke) at 5stations, starting from release edge• Use timed video to measure gravity current height andvelocity as function of down-current position and time• Test Fr = 1 (and constancy) assumption• Use video to determine rough measurements ofentrainment from cloud height measurements asfunction of distance traveled – these measurements usedto assist estimation of approach to N Re independence

Experimental DesignSource box Coverfor filling(removable)15432SlavedVideoCameras8

“C0 2 “ Timing Camera #2 FramesShowing Head Development44 cmt 1 t 2 t 39

Gas Concentration Measurements• Measure gas concentrations with FID at specificheights and down-channel locations for differentflow rates (different N Re )• Compare concentrations at identical dimensionlesstimes and locations, emphasizing “steady” part ofthe flow• If flows are N Re independent, the concentrations atidentical scaled values should approach equality10

Initial Trials Measurements• Density = 1.77 kg/m 3 “CO 2 ” (g ’ = 4.87 m/s 2 )• Density = 1.35 kg/m 3 “Buncefield” (g ’ = 1.40 m/s 2 )11

“C0 2 ”Initial Trials MeasurementsReynolds Number “1500”Gas Density = 1.77 kg/m 3Height of Gas Layer Moving from Box = 5.2 cmHeight of 5.2 cm indicatesVelocity of Current = 25.4 cm/s12

Reynolds Number “1500”“CO 2 ” - 1.77 kg/m 3ReducedGravitym/s 2(upward)FloorVelocitycm/sCalculatedHorizontalVelocity(quasi steady)cm/sMeasuredCloudHeight(initial)cm4.87 1.31 25.4 5.2“Measured” Reynolds Number = 160513

35Reynolds Number “1500” – “CO 2 “ 1.77 g/m 330Velocity (cm/s)25201510Video Run#1Video Run#2FID Runs(averaged)500 100 200 300 400 500 600Down Channel Distance (cm)14

Reynolds Number “1500” - “CO 2 ”Concentration vs. Time – 5 ft down channelConcentration (%)1009080706050403020100120927A #1120927A #20 5 10 15 20 25 30 35 40 45 50 55 60Time (s)Reynolds Number “1500” - “CO 2 ”Concentration vs. DistanceMaximum Concentration100959085800 5 10 15 20Location (ft)15

Front Structure19

“Buncefield”Initial Trials MeasurementsReynolds Number “1000”Gas Density = 1.35 kg/m 3Height of Gas Layer Moving from Box = 8.4 cmHeight of 8.4 cm indicatesVelocity of Current = 15.3 cm/s20

Reynolds Number “1000”“Buncefield” – 1.35 kg/m 3ReducedGravitym/s 2(upward)FloorVelocitycm/sCalculatedHorizontalVelocity(quasi steady)cm/sMeasuredCloudHeight(initial)cm1.40 1.28 15.3 8.4“Measured” Reynolds Number = 102021

20Reynolds Number “1000” -- Buncefield 1.35 g/m 3Velocity (cm/s)1816141210864200 50 100 150 200 250 300 350 400Down Channel Distance (cm)Video Run #1Video Run #2FID Runs22

Concentration (%)1009080706050403020100Reynolds Number “1000” - “Buncefield”Concentration vs. Time – 3 ft down channel0 5 10 15 20 25 30 35 40 45 50 55 60Time (s)121005A #1121005A #2Reynolds Number “1000” - “Buncefield”Concentration vs. DistanceMaximum Concentration (%)100959085800 50 100 150 200 250 300 350 400Distance (cm)23

Current StatusImmediate Plans• Demonstrated experiment repeatability, includingnear-exact transient concentration repeatability• Demonstrated consistent measurement of gravitycurrent velocity by video records and FID gasconcentration measurements• Identified importance of transient phase of gravitycurrent in these experiments• Automate experiment plan/procedure• Investigate vertical concentration distribution• Investigate Reynolds Number Similarity• Investigate scaling considerations for BuncefieldQuestions?24