====== MWAT3 ======
===== Description =====
Coupled mechanical-3 flows analysis; Coupling: Mechanical-Water-Air-Temperature in large deformations. \\ \\
The element is defined by 4, 8, 16, 20, 24 or 32 nodes specified in NODES following the order indicated in the figure.
{{:elements:3delem.png?600|}}
{{:elements:tetraedre.png?400|}} \\ \\
The constitutive "fluid" laws that can be used with this element are: 
  * [[laws:wavat|WAVAT3]]: Mechanical-Water-Air coupling
  * [[laws:wapet|WAPET3]]: Mechanical-Water-Oil coupling
Type: 225 \\ \\
Implemented by: J-P. Radu (2000)
==== Files ====
Prepro: MWAT3A.F \\
Lagamine: MWAT3B.F

===== Input file =====
^Title (A5)^^
|TITLE|"MWAT3" in the first 5 columns|
^Control data (4I5)^^
|NELEM|Number of elements|
|ISPSMAS|= 0 → nothing \\ = 1 → specific weight taken into account if and only if [[:prepro#remark_on_ntana|NTANA]] < 0|
|INSIG|= 0 → No initial stress \\ = 1 or 2 → Initial stresses|
|INBIO|= 0 → No Biot coefficient \\ = 1 → Isotropic Biot coefficient \\ = 2 → Anisotropic Biot coefficient \\ Only for orthotropic mechanical law [[laws:orthopla|ORTHOPLA]]|
^Specific mass - Only if ISPMAS = 1 (1G10.0)^^
|SPEMA5|Specific mass|
^Initial stresses - Only if INSIG > 0 (4G10.0)^^
|If INSIG=1: $\sigma_z=\sigma_{z0}+zd\sigma_{z}$ \\ If INSIG=2: $\sigma_z=min(\sigma_{z0}+zd\sigma_z,0)$||
|SIGZ0| $\sigma_{y0}$ effective stress $\sigma_y$ at the axes origin|
|DSIGZ|Effective stress gradient along Y axis|
|AK0X|$k_0$ ratio $\sigma_x/\sigma_z$|
|AK0Y|$k_0$ ratio $\sigma_y/\sigma_z$ (if AK0Y=0, AK0Y=AK0X)|
|In the calculation of SIGZ0 and DSIGZ, the apparent density $\rho_a'$ must be taken into consideration: \[\rho_a'=\left[(1-n)\rho_s+n S_w\rho_w\right]-\rho_w\] With: \\ $\rho_s$ the solid density (this corresponds to the density of a fictive sample where porosity would be equal to zero) \\ $\rho_w$ the density of the fluid \\ $n$ the porosity defined in the flow law related to this element \\ $S_w$ the fluid saturation, ∈ [0,1]||
^Biot coefficient - Only if INBIO = 1 (1G10.0)^^
|CBIOT|Biot coefficient|
^Definition of the elements (6I5/14I5)^^
|NNODE|Number of nodes of the brick: 8, 16, 20, 24, 32, or 4 for the tetrahedron|
|NPI(1)|Number of integration points in each direction \\ For the tetrahedron with 1 I.P., NPI(1)=1 and NPI(2)=NPI(3)=0 \\ For the tetrahedron with 4 I.P., NPI(1)=4 and NPI(2)=NPI(3)=0|
|NPI(2)|:::|
|NPI(3)|:::|
|LMAT1|Mechanical law|
|LMAT2|Flow law|
|NODES|List of nodes|

===== Results =====
__Stresses (in global axes)__ \\
  * Mechanical stresses: $\sigma_x,\sigma_y,\sigma_z,\sigma_{xy},\sigma_{xz},\sigma_{yz}$
  * Water flow: $f_{wx},f_{wy},f_{wz},f_{w,stored}$ 
  * Air flow: $f_{ax},f_{ay},f_{az},f_{a,stored}$ 
  * Thermal flow: $f_{tx},f_{ty},f_{tz},f_{capacitif}$ 

__Internal variables__ \\
Internal variables of the mechanical law \\
Internal variables of the fluid law