/EBCS/NORMV

Block Format Keyword Describes the elementary boundary condition of imposed normal velocity.

Format


Field	Contents	SI Unit Example
`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)	$[\frac{m}{s}]$
`fct_ID`_vim	Function $f_{v i m} (t)$ identifier for imposed velocity. = 0 $V = F s c a l e_{v i m}$ = n $V = F s c a l e_{v i m} \cdot f_{v i m} (t)$ (Integer)
`Fscale`_vim	Imposed velocity. Default = 0 (Real)	$[\frac{m}{s}]$
`fct_ID`_rho	Function $f_{r h o} (t)$ identifier for density. = 0 $ρ = F s c a l e_{r h o}$ = n $ρ = F s c a l e_{r h o} \cdot f_{r h o} (t)$ (Integer)
`Fscale`_rho	Density scale factor. Default = 0 (Real)	$[\frac{kg}{m^{3}}]$
`fct_ID`_en	Function $f_{e n} (t)$ identifier for energy. = 0 $E = F s c a l e_{e n}$ = n $E = F s c a l e_{e n} \cdot f_{e n} (t)$ (Integer)
`Fscale`_en	Energy scale factor. Default = 0 (Real)	$[J]$
$l_{c}$	Characteristic length. Default = 0 (Real)	$[m]$
`r`₁	Linear resistance. 6 Default = 0 (Real)	$[\frac{kg}{m^{2} s}]$
`r`₂	Quadratic resistance. 6 Default = 0 (Real)	$[\frac{kg}{m^{3}}]$

Input is general, no prior assumptions are enforced! Verify that the elementary boundaries are consistent with general assumptions of ALE (equation closure).
Compatible with /MAT/LAW6 only.
Density, pressure, and 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.
This keyword is less than four or equal to six (non-reflective frontiers (NRF)) using:

$\frac{\partial P}{\partial t} = ρ c \frac{\partial V_{n}}{\partial t} + c \frac{(P_{\infty} - P)}{l_{c}}$

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:
$f_{c} = \frac{c}{2 π . l_{c}}$
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.
$P_{r e s} = r_{1} \cdot V_{n} + r_{2} \cdot V_{n} \cdot | V_{n} |$
It aims at modeling the friction loss due to the valves.