2006 Workshop LEEDS

8/3/2019 2006 Workshop LEEDS

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1 FLACS 2006

FLACS TRAINING EXERCISES

Exercise I (and III): Explosion simulation in offshore platform moduleExplosion tests in an offshore test geometry will be simulated. A step by stepdescription will be available to give a flying start in the explosion modelling.

Exercise II: Geometry building, designing Bang-box and explode


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2 FLACS 2006

Exercise Ia: Explosion simulation in offshore module

Typing convention: Command Explanation

To be typed in unix-shells (boldface): cd TEST_EXAMPLE ( means Carriage return)

To be typed in CASD command line (italic): vi 3 abbreviated VIEW menu, 3D View

Keyboard shortcuts in CASD or FLOWVIS (underline): ALT-v 3 same effect as above in CASD

To be typed by mouse or in dialog window (boldface) 3 4 enter 3 TAB 4, click OK with left mouse

In CASD and FLOWVIS, Mouse can be used for most commands

Mouse buttons are shown as: , ,

If alternate ways of typing is indicated, they are separated by an OR

This exercise is to prepare and simulate a gas explosion in the 8m wide Advantica fullscale rig (HIGH-A conf.)

- An existing geometry model will be opened in the preprocessor CASD

- A simulation mesh will be prepared

- Porosity calculation will be run (mapping of geometry information onto the grid)

- The explosion scenario and result output will be defined

- The FLACS simulation will be run

- The simulation results will be studied in postprocessor FLOWVIS- If time allows, different ignition locations will be applied


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3 FLACS 2006

Exercise Ib: Explosion simulation in offshore moduleTO BE TYPED: Explanation:

Initialising and starting the preprocessor CASD

mkdir YOUR_NAME UNIX: make a distinct catalog in which you perform the exercise

cd YOUR_NAME UNIX: move into this directory

cp ~/GEO/*00001* . UNIX: copy setup files and geometry files for the exercise

f81 UNIX: script to initialize for FLACS-v8.1

run casd UNIX: command starting up the preprocessor CASD

Open and view the geometry in CASD (Move cursor to the CASD window)

choose OPEN in the FILE menu ORfile open OR ALT-f o CASD Ask for opening an existing job file

choose 100001.caj CASD: Open jobfile 100001, using mouse button

if any error message appears click CASD: Ignore error message => error message

Make a grid (mesh) for the simulation, calculate porosities (module dim.: 25.6m x 8m x 8m, origin in corner below the control room)

Choose SIMULATION_VOLUME from GRID menu OR ALT-r v CASD: To enter the extension of the simulation domain

Enter -16 -8 0 40 16 16 CASD: Volume is defined (16m out from vent, 8m to the sides)

In GRID menu, choose DIRECTION X, REGION and enter 56 CASD: 56 grid cells chosen (1.0m grid size).

Use mouse OR grid dir y reg24 dir z reg 16 CASD: 24 cells in Y-direction and 16 cells in Z-direction

Type grid info for quality assurance, and to close window CASD: Check that grid dimension is 1.0m as intended

Choose SAVE from the FILE menu OR ALT-f s CASD: Save geometry and grid files

Choose CALCULATE from POROSITIES menu OR ALT-p c CASD: Map geometry information onto the grid, porcalc

Click in the window that pops up PORCALC: Start calculations

Choose DISPLAY OFF in the GRID menus CASD: Dont draw the grid anymore


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4 FLACS 2006

Exercise Ic: Explosion simulation in offshore moduleTO BE TYPED: Explanation:

Define explosion scenario

Choose MONITOR_POINTS in SCENARIO menu

OR scen mon CASD: Define where to measure variables

click, and 0.8 4.7 7.9 CASD: Add and define location of monitor point 1

repeat this for point 2 (12.3, 4, 0.1) and point 3 (24, 7.9, 7.9) CASD: To edit a non-highlighted monitor, click on its number

Click CASD: Close MONITOR_POINT window

Choose SINGLE_FIELD_SCALAR from SCENARIO menu CASD: Define which variables to report at monitors

Click on

, drag mouse pushing across all monitors, CASD: Log pressure at all three transducers

Repeat for and CASD: Log pressure impulse and dynamic pressure, too

Click and choose SINGLE_FIELD_3D from SCENARIO menu CASD: Define variables for contour plots

Click on

, CTRL-, CTRL-, CASD: Pressure, flame and velocity vectors. CTRL needed to

select more than one (NB! deselect when using the scroll bar)

Choose SIMULATION in SCENARIO menu OR scen sim CASD: Choose output and simulation parameters

Click on , enter 50 , CASD: Increase number of contour plots, return to main menu

Click on GAS_COMP... in SCENARIO menu OR scen gas_c CASD: Define gas cloud loc., size, comp. and concentration

Click on , 0 0 0 CASD: Position of bounding box describing gas cloud

Click on , 25.6 8 8 CASD: Dimension of gas cloud equals module dimensions

Click on , 91.7 7

1.3 CASD: Gas composition is defined

Click on 1.05 0 CASD: Slightly rich gas mixture is chosen ER=1.05

Click on IGNITION in SCENARIO menu

12.5 4.1 4.25

OR scen ign pos 12.5 4.1 4.25 OK CASD: Define location of ignition (12.5, 4.1, 4.25)

Choose SAVE from the FILE menu OR ALT-f s CASD: Save all files, ready to run flacs

Iconise CASD, click at POINT in right corner of CASD frame CASD: Leave CASD for now, can be activated easily


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5 FLACS 2006

Exercise Id: Explosion simulation in offshore moduleTO BE TYPED: Explanation:

Start FLACS simulation, start preprocessor Flowvis(Move cursor to unix-shell)

run flacs 100001 UNIX: Start FLACS simulation

more tt100001 UNIX: Study log-file, give next page, new line

run flowvis UNIX: Start postprocessor FLOWVIS

tail -f tt100001 UNIX: Study tail of log file continuously (end with CTRL-C)

STUDY RESULTS IN POSTPROCESSOR FLOWVIS:

choose ADD from LAYOUT menu, click centrally in window FLOWVIS: Prepare first layoutclick , choose PLOT_TYPE and SCALAR_TIME plot FLOWVIS: Plotting of time histories of variables

choose 100001 and P with , select all 3 monitors (drag mouse) FLOWVIS: Plot pressure time history at all monitors

FLOWVIS: if sim. is running rescan will update plot

Choose MODIFY in the LAYOUT menu, enter 1 2 FLOWVIS: divide plot into 2 layouts

Click at lower frame, then , PLOT_TYPE, SCALAR_TIME_ANNO FLOWVIS: show numerical values from pressure plots

ADD layout and do the same for the DRAG and PIMP variables

Choose ADD in LAYOUT menu, click, PLOT_TYPE, 2D... FLOWVIS: prepare 2D contour plot

Choose 100001, P, click FLOWVIS: contour plot of pressure

click, choose PLOT_SPECIFICATION

deselect GRID/AXIS, select GEOMETRY FLOWVIS: make plot more readable

click, choose PLOT_DOMAIN, change k-index to 5 FLOWVIS: choose XY-cut plane through ignition

Time steps can now be changed moving the lower scroll bar to the right, layout can be varied using the upper scroll bar

Try to show PRESSURE, repeat this method for PROD and VVEC variables FLOWVIS: visualize flame and velocity vectors

Try to show PRESSURE and PROD on the same page using LAYOUT MODIFY

Now that you are familiar with FLOWVIS, try the volume plot menu (select only a job-number not a variable) to study the geometry

Use PLOT SPECIFICATION to switch on geometry drawing and PLOT DOMAIN to narrow the view window and see below the ceiling


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6 FLACS 2006

Exercise Ie: Explosion simulation in offshore module

If time allows, study the effect of ignition location:Enter CASD, open the 100001.caj job-file, save this as a new job number e.g. 100002.caj

Change ignition location in order to study how pressures may vary with different ignition locations

A) End ignition (0.5, 4.1, 4.25), (job number 100002)

B) Your own assumed worst-case location (job number 100003)

Report highest pressure achieved on monitor point

Make mpg-animation of either 2D or volume plots using the export menu (with all timesteps)


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A) Enter CASD and build geometry

Start CASD: run casd

Use Save as option to save job as 200000.caj [accept possible error messages about co-file etc.]

Choose EDIT FILE option in the GEOMETRY menu geometry will be built in the new window

ADD BOX [pos 10, -10, -1, size 40, 25, 1, hue 140, keep all porosities=0] ground is added

Choose MAXIMIZE from VIEW menu to see the full geometry

ADD BOX [pos 0, 0, 0, size 0.01, 4.5, 4.5, hue 210] rear wall of boxADD COPY, EDIT PROPERTIES [change first position from 0 to 9] define front wall of box

ADD COPY, EDIT PROP.. [pos 8, 0.66, 0.66 size 2, 3.18, 3.18], ADD LEFT_DIFF make vent opening in front wall

ADD BOX [pos 0,0,0 size 9, 0.01, 4.5, hue 210], ADD COPY, EDIT PROP [pos 0,4.5,0] side walls

ADD BOX [pos 0,0,4.5 size 9,4.5, 0.01, hue 210] roof is added

Choose ADD UNION 5 times connect primitives in the geometry string

ADD CYLINDER [pos 1, 0, 0.225 dia 0.18, len 4.5, dir Y, hue 0] make cylinder obstruction

EDIT DUPLICATE [no 4, delta 0, 0, 0.9] make 4 more cylinders at same X-location

EDIT DUPLICATE [no 3, delta 2, 0, 0] make 3 more rows of cylinders at this Z-posEDIT DUPLICATE [no 1, delta 1, 0, 0.45] make 4 more rows, with shift in Z-pos

ADD UNION connect to rest of geometry

ADD BOX [pos 22, 1, 0, size 2.5, 2.5, 2.5, hue 0] create one target outside box

ADD UNION connect object primitives

Geometry is now complete, choose FILE SAVE, FILE EXIT [answer yes when asked]

Use view options [3D_VIEW and thereafter SHADE in VIEW menu]

Exercise II: Geometry building & pressure wave propagation


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Exercise IIIb: Blast propagationGrid will now be defined

B) Make grid, save and calculate porosities

Choose GRID SIMULATION_VOLUME [min 0, -9, 0 max 30, 13.5, 13.5] choose grid extent

GRID DIR X, GRID REGION 60, GRID DIR Y, REGION 45, DIR Z REG 27 define regular 0.50m grid

Press CTRL-G 9 times, choose GRID STRETCH POS OK OK stretch grid upwards

GRID DIR Y, CTRL-o, repeat CTRL-SHIFT-G until 9 to 1 (m) is selected select Y-grid lines for y < -1

GRID STRETCH NEG OK OK stretch negative Y

GRID DIR X, GRID DIR Y, repeat CTRL-G until 5.5 to 13.5 (m) is selected select Y-grid lines for y > 5.5mGRID STRETCH POS OK OK stretch positive Y

GRID INFORMATION [close window by OK] check that grid is OK

(if something goes wrong, start again with choosing simulation volume, direction and region for the direction where things went wrong)

FILE SAVE, OK, POROSITIES CALCULATE, CALCULATE save grid, calculate porosities

Geometry is now complete, choose FILE SAVE, FILE EXIT [answer yes when asked] to leave child window and return to main window

Use view options [open inventor symbols to the right + mouse left and central button to study the geometry.]

Box 9m x 4.5m x 4.5m box

with 40 cylinders D= 0.18m

Vent opening is 3.18m x 3.18m

(50% of 4.5m x 4.5m end wall)

Picture shows 3 boxes, only nearest

one is used in this exercise

Picture from similar tests at

Advantica tests site Spadeadam UK


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Exercise IIc: Blast propagationC) Define scenario for calculations

SCENARIO MONITOR_POINTS, choose ADD, EDIT [pos 1, 2.25, 1.25] Define first monitor pointChoose COPY and thereafter ADD 5 times Define points along the axis

use EDIT to change first position to 6, 15, 21.5, 23 and 25 for points 2-6 Modify X-coordinate

Select point at 23m, change 3rd position to 2.75m, exit monitor points menu Put points at top of target box

SCENARIO SINGLE_FIELD_SCALAR choose P, select all 6 monitors with left-mouse Select pressure to be recorded

Repeat for variables PIMP, PROD, UVW Pressure impulse, flame and velocity

SCENARIO_SINGLE_FIELD_3D_ choose P, PROD, VVEC (+U, V, W) and PMAX Remember CTRL-button selecting multiple

SCENARIO SIMULATION_AND choose NPLOT=25, then DTPLOT=0.025 Output options

SCENARIO BOUNDARY choose XLO edit, type PLANE_WAVE, copy/paste to all Non-reflecting boundary cond. everywhereSCEN GAS_COMP, DIM [9, 4.5, 4.5], VOL FRAC [meth 91, ethane 7, propane 2], EQUI [1.05, 0]Define natural gas in box

SCENARIO IGNITION, POS [0.1, 2.25, 2.25] Ignition at rear wall

FILE SAVE 200000.caj and exit CASD

Start simulation in LINUX window: run flacs 200000, check how tt200000 starts up (more tt200000)

D) Result viewing in flowvis

How to operate flowvis you should know from previous exercise, limited explanation is therefore given here.

Study pressure curves at different locations (if in doubt where the monitor points are, use a MONITOR plot option)

Study the 2D-field variables, P, PMAX, PROD, VVEC

If time allows, make a VOLUME plot and animation of this [see hints in the flowvis presentation]


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Exercise IId: Blast propagation

Comparison: experiments by Shell Global Solutions /Advantica (Phase 3B)

40 pipes and 10.1m2 vent (50%) [exact pipe and sensor locations may deviate]

Pressure inside box Pressure at target 13m

Multi-energy method estimate (strong curve 7 or higher) 17.5m away from cloud centre

4893491971197713 m outside free-field blast (mbarg)

100%50%20%10%3%Yield factor4893491971197713 m outside free-

field blast (mbarg)

100%50%20%10%3%Yield factor


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Exercise III: Explosion mitigationApply the test geometry from Exercise I, and investigate how pressures can be reduced

A) Deluge:Open job-files from Exercise I, add a water deluge system and save as new job-number (100004.caj etc.)

Possible systems are:

The FACTORS are calculated based on the water application rate (WAR), which were 16 litre/minute/sqm (MV57) and 26 litre/minute/sqm,(LDN). The simplified relations F1 = 0.23 x WAR and F2 = 4.5 / WAR are used. Simulate two ignition points and one deluge system withFLACS, compare pressure curves of new calculations with dry tests, and also with Interim Guidance Note from Steel Construction Institute.

DELUGE SYSTEM POSITION SIZE VOLUME_FRACTION MEAN_DROPLET_DIA... NOZZLE_TYPE

MV57 (TYPE I) -1, 0, 0 27.6 8.0 8.0 0.2 846 FACTORS:3.73,0.284

LDN (TYPE II) -1, 0, 0 27.6 8.0 8.0 0.2 1280 FACTORS:5.98,0.173

B) Pressure relief panels (remove water deluge before saving as new job number 100006.caj):

Define the following panel on North wall (Y=8), evaluate how the relief panels will influence pressures for worst-case ignition location.

POSITION SIZE MATERIAL PANEL_TYPE OPE.._PR..._DIFF... IN.._AND_FI.._POR.. WEIGHT PANEL_SUBS...

4, 8, 0 12, 0, 8 DefaultMaterial HINGED 0.05, 0.05 0, 0.8 7 0.7, 1

C) Inert gas (remove panels and deluge before saving as 100007.caj):

Add CO2 to the gas mixture, so that the amounts of CO2 is similar to the amount of flammable gas (same volume fraction gives

about 8-9% in final mixture). How will this influence pressures of the explosion, choose one ignition point?

D) Geometry change (remove inert gas, deluge and panel before saving as 100008.caj):

The room between the two control rooms in the test geometry may influence the pressure. Close this room by adding a 16m x 4m x 4m

BOX at POSITION (4, 0, 4). Simulate one scenario to consider the effect of closing the gap and compare to base case.

HINT, use GEOMETRY EDIT FILE, ADD (and define) BOX and ADD UNION

2006 Workshop LEEDS

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