/INIGRAV

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

Format

(1)	(2)	(3)	(5)	(7)
/INIGRAV/`inigrav_ID`/`unit_ID`
`inigrav_title`
`grpart_ID`	`surf_ID`	`grav_ID`
`P`_ref		`Bx`	`By`	`Bz`

Definitions

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)
`P`_ref	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)

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/1
unit for load
#              MUNIT               LUNIT               TUNIT
                   g                  mm                  ms
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/INIGRAV/1/1
hydrostatique pressure - “ sea level : {Z=0} where Pref=0.101325 MPa
#GRPART_ID   SURF_ID   GRAV_ID    
         0         0         1  
#               Pref                  Bx                  By                  Bz          
            0.101325                   0                   0                   0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/GRAV/1/1
Terrestrial gravity field
#funct_IDT       DIR   skew_ID sensor_ID  grnod_ID                      Ascale_x            Fscale_Y
         2         Z         0         0         5                             0            -0.00981
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FUNCT/2
unity
#                  X                   Y
                   0                 1.0                                                            
             1000000                 1.0                                                            
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata

Comments

Gravity value and direction are read from /GRAV card, then grav_ID value is mandatory.
Surface is defined by basis point B=(Bx, By, Bz) and normal vector $g \cdot n$ unless a surface identifier surf_ID is provided. surf_ID is currently only compatible with /SURF/PLANE option in 2018.0 release.
P_ref is the reference pressure which is measured on reference surface. Usually it is pressure at sea level. Above the surface pressure is decreasing, below it is increasing using. The pressure change depends on the signed distance from the reference surface:
(1)
$Δ P_{0} = ρ_{0} | g | d i s t$

Where,

$d i s t = n \cdot d i s t$

Signed distance

$ρ_{0}$

Reference density of the element

Signed distance is computed from element centroid to reference surface. Initial pressure in a given element is:(2)
$P = P_{r e f} + ρ_{0} (d i s t) | g | d i s t$

Where,

$ρ_{0} (d i s t)$

Reference density of the given element

Figure 1.
Same pressure value is applied on all integration point of the elements.
If /INIVOL option is used to initialize volumetric fraction with LAW51 then reference density is automatically computed from initial volumetric fractions.
Currently only compatible with hydrodynamic LAW3, 4, 6, 37, 49, 51 (ALE, EULER).
The grav_ID card must reference a gravity /GRAV with a constant gravity function fct_ID_T from t=0.

Figure 2.