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/INIGRAV

Block Format Keyword Defines initial state from hydrostatic pressure due to gravity loading.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/INIGRAV/inigrav_ID/unit_ID
inigrav_title
grpart_ID surf_ID grav_ID              
Pref Bx By Bz    

Definition

Field Contents SI Unit Example
inigrav_ID Initial gravity loading identifier.

(Integer, maximum 10 digits)

 
unit_ID Optional unit identifier.

(Integer, maximum 10 digits)

 
inigrav_title Initial gravity loading title.

(Character, maximum 100 characters)

 
grpart_ID Group of part identified. If non defined (0), initial state is applied on all solid PARTs.

Default = 0 (Integer)

 
surf_ID (Optional) Free surface identifier.

If not defined, basis point is read.

(Integer)

 
grav_ID (Mandatory) Gravity card identifier used.

(Integer)

 
Pref Reference pressure on the reference surface.

(Real)

[Pa]
Bx Basis point X-coordinate (used only if surf_ID=0).

(Real)

[m]
By Basis point Y-coordinate (used only if surf_ID=0).

(Real)

[m]
Bz Basis point Z-coordinate (used only if surf_ID=0).

(Real)

[m]

Example (Water Hydrostatic Pressure)

Comments

  1. Gravity value and direction are read from /GRAV card, then grav_ID value is mandatory.
  2. The surface identifier provides the sea level. surf_ID can either be a /SURF/PLANE (Figure 1) or any other user surface describing the air-water limit (Figure 2). If surf_ID is not provided, then planar surface is assumed by using B=(Bx,By,Bz) as basis point and gravity vector as surface normal.
  3. Pref is the reference pressure at sea level. Above the surface pressure is decreasing and below the surface pressure is increasing.
  4. This keyword is computing for each cell in group of part provided by grpart_ID. This initial density ρ0 is such as pressure changed is ΔP0=ρ0|g|dist where dist=ndist is the signed distance from the sea level. Distance from sea level is computed using cell centroid.
  5. Mathematical model is such as for each cell P=Pref+ρref|g|dist . This model is only valid if material type is not changing along the distance (constant reference density).
    For example: only air above the surface and only water below the surface. Introducing an immersed body into water would require running a computation to solve hydrostatic state in the immersed body.


    Figure 1. Initial pressure computed from sea level with planar surface


    Figure 2. Initial pressure computed from sea level with user surface
  6. If /INIVOL option is used to initialize volumetric fraction with LAW51 then reference density is automatically computed from initial volumetric fractions.
  7. Currently only compatible with hydrodynamic laws 3, 4, 6, 37, 49, 51, and 151.
  8. The grav_ID card must reference a gravity /GRAV with a constant gravity function fct_IDT from t=0; or, the function can be left blank and the constant gravity value defined in /GRAV, FscaleY.


    Figure 3.