/LOAD/PFLUID

Block Format Keyword

/LOAD/PFLUID - Applies hydrodynamic pressure on a structural surface

Description

This entry provides a simple way to simulate hydrodynamic fluid pressure on a structure. The fluid pressure is calculated according to the specified fluid velocity, orientation of the structural surface against the fluid vector and the height of the fluid column above the surface of the structure.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/LOAD/PFLUID/load_ID/unit_ID
load_title
surf_ID	sens_ID
fct_hsp		Ascalex_hsp		Fscaley_hsp
Dir_hsp	frahsp_ID
fct_pc		Ascalex_pc		Fscaley_pc
fct_vel		Ascalex_vel		Fscaley_vel
Dir_vel	fravel_ID

Field	Contents	SI Unit Example
load_ID	Load block identifier (Integer, maximum 10 digits)
unit_ID	Optional unit identifier (Integer, maximum 10 digits)
load_title	Load block title (Character, maximum 100 characters)
surf_ID	Surface identifier (Integer)
sens_ID	Sensor identifier (Integer)
fct_hsp	Hydro-static pressure as a function of the fluid column height above the structural surface. (Integer)
Ascalex_hsp	Abscissa scale factor for fct_hsp Default = 1.0 (Real)
Fscaley_hsp	Ordinate scale factor for fct_hsp Default = 1.0 (Real)
Dir_hsp	Vertical (gravitational) direction of the water column above the structural surface (input X, Y or Z) (Text)
frahsp_ID	Frame identifier for the vertical (gravitational) direction of the water column above the structural surface. (Integer)
fct_pc	Hydrodynamic drag coefficient as a function of time (Comment 4) (Integer)
Ascalex_pc	Abscissa scale factor for fct_pc Default = 1.0 (Real)
Fscaley_pc	Ordinate scale factor for fct_pc Default = 1.0 (Real)
fct_vel	Fluid velocity as a function of time (Integer)
Ascalex_vel	Abscissa scale factor for fct_vel Default = 1.0 (Real)
Fscaley_vel	Ordinate scale factor for fct_vel Default = 1.0 (Real)
Dir_vel	Direction of fluid velocity (input X, Y or Z) (Text)
fravel_ID	Frame identifier for the fluid velocity direction (Integer)

In this example, /LOAD/PFLUID is used to simulate wind (with velocity 15[mm/ms]) effect on textile.

load_pfluid_example

#RADIOSS STARTER

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/UNIT/1

unit for load

# MUNIT LUNIT TUNIT

kg mm ms

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/LOAD/PFLUID/1/1

Wind effect

# surf_ID sens_ID

8 0

# fct_hsp Ascalex_hsp Fscaley_hsp

0 0 0

# Dir_hsp frahsp_ID

# fct_pc Ascalex_pc Fscaley_pc

2 0 2

# fct_vel Ascalex_vel Fscaley_vel

3 0 15

# Dir_vel fravel_ID

Y 0

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/FUNCT/2

Air density

# X Y

0 1.2E-9

1000 1.2E-9

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/FUNCT/3

Air velocity

# X Y

0 1

1000 1

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#ENDDATA

1.	The fluid pressure applied to each element of the structural surface is computed as:

Where,

is the fluid density

g is the acceleration due to gravity

h is the height of the water column above an element of the structural surface

V(t) is the relative fluid velocity which is normal to the element of the structural surface

D(t) is the drag coefficient for complete structural surface. The value of the drag coefficient depends on the shape of the cross-section of the body in the direction of fluid flow (Figure 1).

measured_drag_coefficients

Figure 1: Drag coefficient values for different shapes

2.	The value of hydrostatic pressure () as a function of fluid column height (h) above the structural surface is stated using the function fct_hsp. If this is not defined (=0), the effect is not accounted for (fct_hsp(altitude)=0).

3.	Hydrodynamic pressure is calculated with respect to the relative orientation of the fluid vector and the element normal.

Where,

is the specified fluid velocity (fct_vel(t)). If not defined (=0), the effect of fluid velocity is not accounted for (V(t) =0)

is the element velocity

is the element normal

4.	fct_pc defines the value of as a function of time. If this is not defined, the effect of fluid velocity is not accounted for.