/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_IDT Dir skew_ID sens_ID grnd_ID   Ascalex FscaleY

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_IDT Time function identifier. 3
= 0 (Default)
A constant gravity defined in FscaleY is applied.
> 0
The applied gravity is time dependent.

(Integer)

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

Default = Z (Text)

 
skew_ID Skew identifier.

(Integer)

 
sens_ID Sensor identifier.
0
The gravity load is applied after sensor activation (the time function is shifted in time).

(Integer)

 
grnd_ID Node group to which the gravity load is applied.

Default = 0 (See Comment 2)

(Integer)

 
Ascalex Abscissa (time) scale factor.

Default = 1.0 (Real)

[ s ]
FscaleY If fct_IDT = 0: A constant gravity value is applied.

If fct_IDT > 0: Ordinate (force) scale factor.

Default = 1.0 (Real)

[ m s 2 ]

Example

#---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

  1. The gravity load direction must be right justified in the ten characters of field number 2.
  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.
  3. If function fct_IDT =0 or is blank, the gravity load is a constant value g ( t ) = F s c a l e y MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaci4zamaabm aabaGaamiDaaGaayjkaiaawMcaaiabg2da9iaadAeacaWGZbGaam4y aiaadggacaWGSbGaamyzamaaBaaaleaacaWG5baabeaaaaa@4101@ .
    Otherwise, if the function fct_IDT is defined, the actual load function value is calculated as: (1)
    g ( t ) = F s c a l e y f t ( t A s c a l e x )

    Where, f T is the function of fct_IDT.

    /GRAV applies to each node and is stated as force:(2)
    F ( t ) = m g ( t )

    With m being the mass of node. The node will be moving until a force balance reached.

  4. If the gravity card is referenced by an /INIGRAV card for hydrostatic pressure initialization in a fluid-structure interaction simulation, the applied gravity must be constant be a constant value by defining FscaleY without fct_IDT or by referencing a constant function from t=0 in fct_IDT.


    Figure 1.