/DT/FVMBAG/Iflag

Engine Keyword Time step for control for Finite Volume Method airbag.

Format

  • For Iflag = 0, 1

    /DT/FVMBAG/Iflag

    ΔTsca ΔTmin

  • For Iflag = 2

    /DT/FVMBAG/Iflag

    ΔTsca ΔTmin Lambda L_type

    Monvol_ID

Definition

Field Contents SI Unit Example
Iflag Finite volume merge flag.
= 0 or blank (Default)
The finite volume is merged, if the time step < airbag volume < 10 * the minimum volume defined in global merge, /FVMBAG/MODIF.
= 1
The finite volume is merged, if time step < ΔTmin .
= 2
The finite volume is merged, if time step < ΔTmin . The time step computation is defined by the flag L_type. 2
ΔTsca Scale factor on time step.

Default = 0.9 (Real)
ΔTmin Minimum time step.

(Real)

 [s]
Lambda Stability factor.

Default = 0.01 (Real)
L_type Time step computation method.
= 1
Characteristic length of FVM mesh (computed during Starter).
= 2 (Default)
Characteristic length is computed from cubic root of the volume.
Monvol_ID Monitored volume identifier.

(Integer)

Comments

  1. The ΔTsca and ΔTmin can be defined to ensure stability and a minimum time step size by triggering additional finite volume merges when the FVMBAG entity penalizes the computation.
  2. When using /DT/FVMBAG/2, time step is computed as:
    ΔT=ΔTscalΔx|u−w|+c
    Where,
    u
    Gas velocity.
    w
    Polyhedron velocity.
    c
    Speed of sound.
    Δx
    Characteristic length.

    The soothing factor is applied using ΔT←min(ΔT,ΔTold(1+λ)) .