Iform = 12
Block Format Keyword Up to 4 different submaterials (solid, liquid, gas and explosives) can be defined by specifying a material identifier and initial volume fraction.
 LAW3 (HYDPLA)
 LAW4 (HYD_JCOOK)
 LAW5 (JWL)
 LAW6 (HYDRO)
 LAW10 (DPRAG1)
 LAW102 (DPRAG2)
 /EOS/LINEAR
 /EOS/POLYNOMIAL
 /EOS/IDEALGAS
 /EOS/STIFFGAS
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/MAT/LAW51/mat_ID/unit_ID  
mat_title  
Blank  
I_{form} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

$\nu $  ${\nu}_{vol}$ 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

mat_ID_{1}  ${\alpha}_{0}^{mat\text{\hspace{0.05em}}\_\text{}\text{\hspace{0.05em}}1}$ 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

mat_ID_{1}  ${\alpha}_{0}^{mat\text{\hspace{0.05em}}\_\text{}\text{\hspace{0.05em}}1}$  
mat_ID_{2}  ${a}_{}^{mat\text{\hspace{0.05em}}\_\text{}2}$  
mat_ID_{3}  ${a}_{}^{mat\text{\hspace{0.05em}}\_\text{}3}$  
mat_ID_{4}  ${a}_{}^{mat\text{\hspace{0.05em}}\_\text{}4}$ 
Definitions
Field  Contents  SI Unit Example 

mat_ID  Material
identifier. (Integer, maximum 10 digits) 

unit_ID  Unit Identifier (Integer, maximum 10 digits) 

mat_title  Material
title. (Character, maximum 100 characters) 

I_{form}  Formulation flag =
12. (Integer) 

$\nu $  Kinematic viscosity in
shear
$\nu =\mu /\rho $
. Default = 0 (Real) 
$\left[\frac{{\text{m}}^{\text{2}}}{\text{s}}\right]$ 
${\nu}_{vol}$  Kinematic viscosity
(volumetric),
${\nu}_{vol}=\frac{3\lambda +2\mu}{\rho}$
which corresponds to Stokes
Hypothesis. Default = 0 (Real) 
$\left[\frac{{\text{m}}^{\text{2}}}{\text{s}}\right]$ 
mat_ID_{1}  Material Identifier for
the 1st submaterial which must refer to LAW3, 4, 5, 6, 10, or
102. Mandatory (Integer) 

${\alpha}_{0}^{mat\text{\hspace{0.05em}}\_1}$  Initial volumetric
fraction for the 1st submaterial. Default = 0 (Real) 

mat_ID_{i}  (Optional) Material
Identifier from 2nd to 4th submaterial which must refer to LAW3, 4,
5, 6, 10 or 102. Default = 0 (Integer) 

${\alpha}_{0}^{mat\text{\hspace{0.05em}}\_i}$  (Optional) Initial
volumetric fraction. (Real) 
Example
#RADIOSS STARTER
#12345678910
/UNIT/1
unit for mat
g mm ms
#12345678910
/MAT/LAW51/101/1
99.99% WaterMULTIMAT:AIR+WATER ,units {g,mm,ms}
# RHO_I RHO_0
# IFLG
12
# NU LAMDA
0 0
# MAT_1 ALPHA_1
5 0.9999
# MAT_2 ALPHA_2
4 0.0001
/ALE/MAT/101/1
# Modif. factor.
0
#12345678910
/MAT/HYDRO/4/1
AIR
# RHO_I RHO_0
1.22e6 0
# Knu Pmin
0 0
/EOS/IDEALGAS/4/1
EoS for Air at atmospheric pressure
# GAMMA P0 PSH T0 RHO0
1.4 0.10 0 300.0 1.22E6
#12345678910
/MAT/LAW06/5/1
water
# RHO_I
0.001
# KNU PMIN
0 0
/EOS/STIFFGAS/5/1
STIFF_GAS_WATER
# GAMMA P0 PSH P_STAR RHO0
6.1 0.10 0 368.85
#12345678910
#enddata
Comments
 The material law is based on a diffusive interface technique. Numerical diffusion can be improved using MUSCL method for volume fraction (/ALE/MUSCL). The previous /UPWIND used to limit diffusion is now obsolete.
 The submaterials can be listed in any order, but there can only be one explosive submaterial /MAT/LAW5.
 If 4 submaterials are requested, at least one of them should be an explosive submaterial /MAT/LAW5.
 Kinematic
viscosities are global and is not specific to each material. They are used to
compute the viscous stress tensor:
(1) $$\tau =\mu \left[\left(\nabla \otimes V\right)+{\text{\hspace{0.17em}}}^{t}\text{}\left(\nabla \otimes V\right)\right]+\lambda \left(\nabla V\right)I$$Where, $\nu =\mu /\rho $
 Kinematic viscosity in shear
 ${\nu}_{vol}=\frac{3\left(\lambda +\frac{2\mu}{3}\right)}{\rho}$
 Kinematic volumetric viscosity flag
 Volumetric
fractions enable the sharing of elementary volume within the three different
materials.
For each material ${\alpha}_{0}^{mat\text{\hspace{0.05em}}\_\text{}\text{\hspace{0.05em}}i}$ must be defined between 0 and 1.
Sum of initial volumetric fractions $\sum}_{i=1}^{3}{\alpha}_{0}^{mat\text{}\_\text{}i$ must be equal to 1.
For automatic initial fraction of the volume, refer to the /INIVOL card.
 It is not recommended to use this law with Radioss single precision engine.