/EBCS
Block Format Keyword Describes the elementary boundary condition sets.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/EBCS/type/ebcs_ID/unit_ID  
ebcs_title 
Type: GRADP0, PRES, VALVIN or VALVOUT
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

surf_ID  
C  
fct_ID_{pr}  Fscale_{pr}  
fct_ID_{rho}  Fscale_{rho}  
fct_ID_{en}  Fscale_{en}  
l_{c}  r_{1}  r_{2} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

surf_ID  
C  
fct_ID_{vx}  Fscale_{vx}  
fct_ID_{vy}  Fscale_{vy}  
fct_ID_{vz}  Fscale_{vz}  
fct_ID_{rho}  Fscale_{rho}  
fct_ID_{en}  Fscale_{en}  
l_{c}  r_{1}  r_{2} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

surf_ID  
C  
fct_ID_{vim}  Fscale_{vim}  
fct_ID_{rho}  Fscale_{rho}  
fct_ID_{en}  Fscale_{en}  
l_{c}  r_{1}  r_{2} 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

surf_ID  
Rho  C  ${l}_{c}$ 
Definitions
Field  Contents  SI Unit Example 

type  Elementary boundary
condition keyword. (see EBCS Type for available keywords) 

ebcs_ID  Elementary boundary
condition identifier. (Integer, maximum 10 digits) 

unit_ID  Unit Identifier (Integer, maximum 10 digits) 

ebcs_title  Elementary boundary
condition title. (Character, maximum 100 characters) 

surf_ID  Surface
identifier. (Integer) 

C  Speed of sound. Default = 0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$ 
fct_ID_{pr}  Function
${\mathrm{f}}_{pr}\left(t\right)$
identifier for pressure.
(Integer) 

Fscale_{pr}  Pressure scale
factor. Default = 0 (Real) 
$\left[\text{Pa}\right]$ 
fct_ID_{rho}  Function
${\mathrm{f}}_{rho}\left(t\right)$
identifier for density.
(Integer) 

Fscale_{rho}  Density scale
factor. Default = 0 (Real) 
$[\frac{\text{kg}}{{\text{m}}^{3}}]$ 
fct_ID_{en}  Function
${\mathrm{f}}_{en}\left(t\right)$
identifier for energy.
(Integer) 

Fscale_{en}  Energy scale
factor. Default = 0 (Real) 
$\left[\text{J}\right]$ 
${l}_{c}$  Characteristic
length. Default = 0 (Real) 
$\left[\text{m}\right]$ 
r_{1}  Linear resistance. 6 Default = 0 (Real) 
$\left[\frac{\text{kg}}{{\text{m}}^{2}\text{s}}\right]$ 
r_{2}  Quadratic resistance.
6 Default = 0 (Real) 
$\left[\frac{\text{kg}}{{\text{m}}^{3}}\right]$ 
fct_ID_{vx}  Function
${\mathrm{f}}_{VX}\left(t\right)$
identifier for X velocity.
(Integer) 

Fscale_{vx}  X velocity scale
factor. Default = 0 (Real) 
$\left[\frac{\text{kg}}{{\text{m}}^{3}}\right]$ 
fct_ID_{vy}  Function
${\mathrm{f}}_{VY}\left(t\right)$
identifier for Y velocity.
(Integer) 

Fscale_{vy}  Y velocity scale
factor. Default = 0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$ 
fct_ID_{vz}  Function
${\mathrm{f}}_{VZ}\left(t\right)$
identifier for Z velocity.
(Integer) 

Fscale_{vz}  Z velocity scale
factor. Default = 0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$ 
fct_ID_{vim}  Function
${\mathrm{f}}_{vim}\left(t\right)$
identifier for imposed velocity.
(Integer) 

Fscale_{vim}  Imposed
velocity. Default = 0 (Real) 
$\left[\frac{\text{m}}{\text{s}}\right]$ 
Rho  Initial density. Default = 0 (Real) 
$\left[\frac{\text{kg}}{{\text{m}}^{3}}\right]$ 
EBCS Type
Type  Keyword  Description 

0  GRADP0  Zero pressure gradient. Is not allowed for SPMD parallel version. 
1  PRES  Imposed density and pressure 
2  VALVIN  Inlet valve (Imposed density and pressure) 
3  VALVOUT  Outlet valve (Imposed density and pressure) 
4  VEL  Imposed velocity 
5  NORMV  Imposed normal velocity 
6  INIP  Initial pressure 
7  INIV  Initial velocity 
Comments
 Input is general, no prior assumptions are enforced! You must verify that the elementary boundaries are consistent with general assumptions of ALE (equation closure).
 It is not advised to use the Hydrodynamic Bimaterial Liquid Gas Law (/MAT/LAW37 (BIPHAS)) with the elementary boundary conditions.
 Density, pressure, energy are imposed according to a scale factor and a time function. If the function number is 0, the imposed density, pressure and energy are used.
 All EBCS which type is less tha four or
equal to six are nonreflective frontiers (NRF), using:
(1) $$\frac{\partial P}{\partial t}=\rho c\frac{\partial {V}_{n}}{\partial t}+c\frac{\left({P}_{\infty}P\right)}{{l}_{c}}$$Pressure in the far field ${P}_{\infty}$ is imposed with a function of time. The transient pressure is derived from ${P}_{\infty}$ , the local velocity field V and the normal of the outlet facet.
Where, ${l}_{c}$ is the characteristic length, to compute cutoff frequency ${f}_{c}$ as:(2) $${f}_{c}=\frac{c}{2\pi .{l}_{c}}$$  In order to impose a positive velocity fct_ID_{vim} (for instance 15 m/s), you must input fct_ID_{vim} (for instance 15 m/s).
 A resistance pressure is computed and
added to the current pressure.
(3) $${P}_{res}={r}_{1}\cdot {V}_{n}+{r}_{2}\cdot {V}_{n}\cdot \left{V}_{n}\right$$It aims at modeling the friction loss due to the valves.