Moving Train FDS 6.7

[Dimitris_fds]

Hello all, I would like to simulate a moving train inside tunnel using the 6.7 version of FDS. I ' ve been trying the old code above.The problem is the velocity variable is not well defined cause the box does not move. Any ideas??

&HEAD CHID='train', TITLE='train moving through a tunnel' /

&MESH IJK=100,16,16, XB=0,100,-8,8,0,16/

&TIME T_END=10.0/

/&MISC IMMERSED_BOUNDARY_METHOD=2/

&VENT MB='XMIN', SURF_ID='OPEN'/

&VENT MB='XMAX', SURF_ID='OPEN'/

&SLCF PBY=0,QUANTITY='VELOCITY',VECTOR=.TRUE./

&SLCF PBY=0,QUANTITY='PRESSURE'/

&SLCF PBZ=8,QUANTITY='VELOCITY',VECTOR=.TRUE./

&SLCF PBZ=8,QUANTITY='PRESSURE'/

&GEOM ID='train'

/XB=80,100,-4,4,4,12

/VELOCITY=20,0,0

/SHAPE='BOX'/

&TAIL /

[dr_jfloyd]

FDS 6.7 does not have a VELOCITY input for GEOM.

[Randy McDermott]

Moving geometry is not supported in FDS.  You are better off leaving the geometry fixed and putting a tangential velocity on the walls of the tunnel.

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[Matteo Pachera]

Dear,

I have a similar question and I hope there can be a solution to my problem, I would like to track the effect of an object (I'm trying with a particle as obstacles shouldn't move around) moving in a quiescent flow following a prescribed path.

I made few trials:

I modelled few particles dropping in a domain which is open at the two ends (input_gravity.fds), in this case the particles' movement is driven by the gravity force.

I later tried to impose the particle movement using PATH_RAMP  instead of the gravity (input_path.fds)

In the first case I see the flow moving and I see a variation in pressure along the domain which is induced by the particles' drag, in the second case nothing moves and the pressure remains constant.

I don't know if I'm doing some implementation errors in the second case or simply FDS works differently with the two approaches. 

Thanks in advance for the support,

Matteo

[Matteo Pachera]

I apologize for sending the input code in this form, but I get an error when I try to attach the input files

&HEAD CHID='moving_gravity', TITLE='Pressure drop in a duct filled with spheres' /

&MESH IJK=400,10,10, XB=0.0,4.0,0.0,0.1,0.0,0.1 /

&TIME T_END=20./

&MISC NOISE=.FALSE., GVEC=10,0,0/

&DUMP DT_DEVC=0.1,DT_SLCF=0.2, DT_PART=0.2 / 

&RADI RADIATION=.FALSE./

&PRES SOLVER='GLMAT'/

&VENT MB='XMIN', SURF_ID='OPEN' /

&VENT MB='XMAX', SURF_ID='OPEN' /

&SURF ID         = 'ball'

      MATL_ID    = 'stuff'

      THICKNESS  = 0.001

      GEOMETRY   = 'SPHERICAL' /

      

&MATL ID = 'stuff'

      DENSITY = 514.

      CONDUCTIVITY = 0.1

      SPECIFIC_HEAT= 1.0 /

 

&PART ID='ball', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&INIT PART_ID='ball', XB=0.0,0.01,0.0,0.1,0,0.1, N_PARTICLES_PER_CELL=50, CELL_CENTERED=.TRUE./

&DEVC XB=0.0,0.0,0.0,0.1,0.0,0.1 , QUANTITY='MASS FLOW', ID='mass_in'/

&DEVC XB=4.0,4.0,0.0,0.1,0.0,0.1 , QUANTITY='MASS FLOW', ID='mass_out'/

&DEVC XB=0.0,0.0,0.0,0.1,0.0,0.1 , QUANTITY='VOLUME FLOW', ID='volume_in'/

&DEVC XB=4.0,4.0,0.0,0.1,0.0,0.1 , QUANTITY='VOLUME FLOW', ID='volume_out'/

&DEVC XB=0.5,0.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo01', STATISTICS='MEAN'/

&DEVC XB=1.0,1.0,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo02', STATISTICS='MEAN'/

&DEVC XB=1.5,1.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo03', STATISTICS='MEAN'/

&DEVC XB=2.0,2.0,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo04', STATISTICS='MEAN'/

&DEVC XB=2.5,2.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo05', STATISTICS='MEAN'/

&DEVC XB=3.0,3.0,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo06', STATISTICS='MEAN'/

&DEVC XB=3.5,3.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo07', STATISTICS='MEAN'/

&DEVC XB=0.5,0.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres01', STATISTICS='MEAN'/

&DEVC XB=1.0,1.0,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres02', STATISTICS='MEAN'/

&DEVC XB=1.5,1.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres03', STATISTICS='MEAN'/

&DEVC XB=2.0,2.0,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres04', STATISTICS='MEAN'/

&DEVC XB=2.5,2.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres05', STATISTICS='MEAN'/

&DEVC XB=3.0,3.0,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres06', STATISTICS='MEAN'/

&DEVC XB=3.5,3.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres07', STATISTICS='MEAN'/

&SLCF PBY=0.05, QUANTITY='VELOCITY' /

&SLCF PBY=0.05, QUANTITY='PRESSURE' /

&TAIL /

&HEAD CHID='moving_path', TITLE='Pressure drop in a duct filled with spheres' /

&MESH IJK=400,10,10, XB=0.0,4.0,0.0,0.1,0.0,0.1 /

&TIME T_END=20./

&MISC NOISE=.FALSE., GVEC=10,0,0/

&DUMP DT_DEVC=0.1,DT_SLCF=0.2, DT_PART=0.2 / 

&RADI RADIATION=.FALSE./

&PRES SOLVER='GLMAT'/

&VENT MB='XMIN', SURF_ID='OPEN' /

&VENT MB='XMAX', SURF_ID='OPEN' /

&SURF ID         = 'ball'

      MATL_ID    = 'stuff'

      THICKNESS  = 0.01

      GEOMETRY   = 'SPHERICAL' /

      

&MATL ID = 'stuff'

      DENSITY = 514.

      CONDUCTIVITY = 0.1

      SPECIFIC_HEAT= 1.0 /

 

&PART ID='ball01', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball02', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball03', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball04', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball05', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball06', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball07', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball08', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball09', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&PART ID='ball10', SAMPLING_FACTOR=1, SURF_ID='ball',DRAG_COEFFICIENT=4, /

&INIT XB=0.00,0.001,0.050,0.051,0.004,0.005,  PART_ID='ball01', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.014,0.015,  PART_ID='ball02', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.024,0.025,  PART_ID='ball03', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.034,0.035,  PART_ID='ball04', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.044,0.045,  PART_ID='ball05', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.054,0.055,  PART_ID='ball06', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.064,0.065,  PART_ID='ball07', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.074,0.075,  PART_ID='ball08', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.084,0.085,  PART_ID='ball09', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&INIT XB=0.00,0.001,0.050,0.051,0.094,0.095,  PART_ID='ball10', PATH_RAMP(1)='PART RAMP X' N_PARTICLES=1/

&RAMP ID='PART RAMP X', T=0.00, F=0.0/

&RAMP ID='PART RAMP X', T=1.0, F=4.0/

&DEVC XB=0.0,0.0,0.0,0.1,0.0,0.1 , QUANTITY='MASS FLOW', ID='mass_in'/

&DEVC XB=4.0,4.0,0.0,0.1,0.0,0.1 , QUANTITY='MASS FLOW', ID='mass_out'/

&DEVC XB=0.0,0.0,0.0,0.1,0.0,0.1 , QUANTITY='VOLUME FLOW', ID='volume_in'/

&DEVC XB=4.0,4.0,0.0,0.1,0.0,0.1 , QUANTITY='VOLUME FLOW', ID='volume_out'/

&DEVC XB=0.5,0.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo01', STATISTICS='MEAN'/

&DEVC XB=1.0,1.0,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo02', STATISTICS='MEAN'/

&DEVC XB=1.5,1.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo03', STATISTICS='MEAN'/

&DEVC XB=2.0,2.0,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo04', STATISTICS='MEAN'/

&DEVC XB=2.5,2.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo05', STATISTICS='MEAN'/

&DEVC XB=3.0,3.0,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo06', STATISTICS='MEAN'/

&DEVC XB=3.5,3.5,0.0,0.1,0.0,0.1 , QUANTITY='VELOCITY', ID='velo07', STATISTICS='MEAN'/

&DEVC XB=0.5,0.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres01', STATISTICS='MEAN'/

&DEVC XB=1.0,1.0,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres02', STATISTICS='MEAN'/

&DEVC XB=1.5,1.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres03', STATISTICS='MEAN'/

&DEVC XB=2.0,2.0,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres04', STATISTICS='MEAN'/

&DEVC XB=2.5,2.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres05', STATISTICS='MEAN'/

&DEVC XB=3.0,3.0,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres06', STATISTICS='MEAN'/

&DEVC XB=3.5,3.5,0.0,0.1,0.0,0.1 , QUANTITY='PRESSURE', ID='pres07', STATISTICS='MEAN'/

&SLCF PBY=0.05, QUANTITY='VELOCITY' /

&SLCF PBY=0.05, QUANTITY='PRESSURE' /

&TAIL /

[dr_jfloyd]

We had added the PATH_RAMP for a particle with the thought of supporting a DEVC that could move over time. With that in mind the logic was coded so that it only updates the particle position but doesn't take the derivative of position to define a velocity. With no velocity defined, the drag, which is computed using velocity, is zero.  

[Matteo Pachera]

Thank you for your quick reply, is there another way I could use to impose the velocity of the moving object?

[dr_jfloyd]

As Randy already noted. FDS is not set up to have a moving object.  Even if we had the particle path ramp tied into drag, this would still not act like a train. Lagrangian particles do not currently occupy any volume, so the moving train particle would not displace air around it.