/PROP/TYPE15 (POROUS)

Block Format Keyword Describes the porous solid element property set (extended Darcy's law).

Format

(1)	(2)	(3)	(4)	(5)
/PROP/TYPE15/`prop_ID` or /PROP/POROUS/`prop_ID`
`prop_title`
Blank Format
`q`_a		`q`_b		`h`
`Por`
`R`₁		`R`₂		`R`₃
`skew_ID`_r	`Ihon`
`Itu`	$α$		`l`_mix
`node_ID`

Definition

Field	Contents	SI Unit Example
`prop_ID`	Property identifier (Integer, maximum 10 digits)
`prop_title`	Property title (Character, maximum 100 characters)
`q`_a	Quadratic bulk viscosity Default = 10^-20 (Real)
`q`_b	Linear bulk viscosity Default = 10^-20 (Real)
`h`	Hourglass viscosity coefficient Default = 0.10 (Real)
`Por`	Porosity Default = 1.0 (Real)
`R`₁	Specific resistance factor in direction 1 Default = 0.0 (Real)
`R`₂	Specific resistance factor in direction 2 Default = 0.0 (Real)
`R`₃	Specific resistance factor in direction 3 Default = 0.0 (Real)
`skew_ID`_r	Skew identifier for resistance orthotropy (Integer)
`Ihon`	Honeycomb substrate flag. =1 Resistance applies only in direction 1 of `skew_ID`_r and velocities are constrained in directions 2 and 3. Default = 0.0 (Integer)
`Itu`	Turbulence imposed by medium flag. 7 = 0 Turbulence is done according to $k - ε$ model. = 1 Turbulence is imposed by porous model. Default = 0.0 (Integer)
$α$	Turbulence coefficient for honeycomb substrate. Default = 0.1 (Real)
`l`_mix	Turbulence mixing length. (Real)	[m]
`node_ID`	Main node identifier of rigid body modeling rigid substrate. Default = 0 (Integer)

Example (Air)

#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/PROP/POROUS/4
AIR (unit kg_m_s)

#                q_a                 q_b                   h
               1E-20               1E-20                   0
#                Por
                   1
#                 R1                  R2                  R3
                 400                 400                 400
# skew_IDr      Ihon
         0         0
#      Itu               alpha               I_mix
         0                   0                   0
#rbody_IDs
         0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata
/END
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Example (Gas)

#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/PROP/POROUS/13
GAS (unit kg_m_s)

#                q_a                 q_b                   h
                 1.1                 .05                   0
#                Por
                   0
#                 R1                  R2                  R3
                3500                   0                   0
# skew_IDr      Ihon
         3         1
#      Itu               alpha               I_mix
         1                 .05                .003
#rbody_IDs
     43218
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata
/END
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Comments

The q_a and q_b default values are equal to 1.10 and 0.05 in non-CFD versions.
Porosity (relative volume of pores) is taken into account for 3D Euler materials only. Porosity is otherwise set to 1.
$F_{i} = - m R_{i j} V_{j}$ is added to nodal force vector, $R_{i j}$ being the tension representation of the specific resistance factor in the global skew system.
If all resistance factors are set to 0, no computation is performed but the grid velocity can be tied to rigid body node_ID (Line 9).
Specific resistances along orthotropic axis are defined in Line 7 with respect to skew_ID_r (by default global system).
Relevant only if material is material law 6 with $k - ε$ turbulence.
If Itu =1, turbulence is imposed by porous model.(1)
$k = {(α V)}^{2}$

and(2)
$ε = \frac{k^{1.5}}{l_{m i x}}$
Fluid reaction force vector and moment are transmitted to specified rigid body; this option is available in 3D only.
Grid velocity is computed according to node_ID rigid body movement. This option is useful to impose such a movement to a grid, even for non-porous material.