/GRAV
Block Format Keyword Defines gravity load on node group.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/GRAV/grav_ID/unit_ID  
grav_title  
fct_ID_{T}  Dir  skew_ID  sens_ID  grnd_ID  Ascale_{x}  Fscale_{Y} 
Definitions
Field  Contents  SI Unit Example 

grav_ID  Gravity load block
identifier (Integer, maximum 10 digits) 

unit_ID  Unit Identifier (Integer, maximum 10 digits) 

grav_title  Gravity load block
title. (Character, maximum 100 characters) 

fct_ID_{T}  Time function identifier.
3
(Integer) 

Dir  Direction in translation
(input should be: X, Y or Z). Default = Z (Text) 

skew_ID  Skew
identifier. (Integer) 

sens_ID  Sensor identifier.
(Integer) 

grnd_ID  Node group to which the
gravity load is applied. Default = 0 (See Comment 2) (Integer) 

Ascale_{x}  Abscissa (time) scale
factor. Default = 1.0 (Real) 
$\left[\text{s}\right]$ 
Fscale_{Y}  If
fct_ID_{T} =
0: A constant gravity value is applied. If fct_ID_{T} > 0: Ordinate (force) scale factor. Default = 1.0 (Real) 
$\left[\frac{\text{m}}{{\text{s}}^{2}}\right]$ 
Example
#12345678910
/UNIT/1
unit for load
# MUNIT LUNIT TUNIT
g mm ms
#12345678910
/INIGRAV/1/1
hydrostatique pressure â€“ 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
#12345678910
/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
#12345678910
/FUNCT/2
unity
# X Y
0 1.0
1000000 1.0
#12345678910
#enddata
Comments
 The gravity load direction must be right justified in the ten characters of field number 2.
 By default, the gravity loads are applied to all the nodes in the model. The gravity loads can be applied to a specifc group of nodes by defining grnd_ID.
 If function
fct_ID_{T}
=0 or is blank, the gravity load is a constant value
$\mathrm{g}\left(t\right)=Fscal{e}_{y}$
.Otherwise, if the function fct_ID_{T} is defined, the actual load function value is calculated as:
(1) $$\mathrm{g}\left(t\right)=Fscal{e}_{y}\cdot {\mathrm{f}}_{t}\cdot \left(\frac{t}{Ascal{e}_{x}}\right)$$Where, ${\mathrm{f}}_{T}$ is the function of fct_ID_{T}.
/GRAV applies to each node and is stated as force:(2) $$\mathrm{F}\left(t\right)=m\cdot \mathrm{g}\left(t\right)$$With m being the mass of node. The node will be moving until a force balance reached.
 If the gravity card is referenced by an /INIGRAV card for hydrostatic pressure initialization in a fluidstructure interaction simulation, the applied gravity must be constant be a constant value by defining Fscale_{Y} without fct_ID_{T} or by referencing a constant function from t=0 in fct_ID_{T}.