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CFD_HE

CFD

*CFD_HE
"Optional title"
sid
type, gid, E2C
$\rho$, $A$, $B$, $R_1$, $R_2$, $\omega$, $e_0$, $D$
$e_{ab}$, $t_{ab}$, $C_v$

Parameter definition

Variable
Description
sid
Subdomain ID
type
High explosive type
options:
preset $\rightarrow$ see list below
USER $\rightarrow$ user defined
mid $\rightarrow$ material ID
gid
Geometry ID
E2C
CFD cells are filled as elements are eroded (element to CFD mapping)
options:
0 $\rightarrow$ no
1 $\rightarrow$ yes
$\rho$
Density (this line is only used if type=USER)
$A$
JWL coefficient
$B$
JWL coefficient
$R_1$
JWL coefficient
$R_2$
JWL coefficient
$\omega$
JWL coefficient
$e_0$
Internal energy per unit volume, released at detonation
$D$
Detonation velocity
$e_{ab}$
Afterburn energy per unit volume at detonation time
$t_{ab}$
Afterburn time parameter, controlling energy release rate
$C_v$
Heat capacity
default: $711.14 J/kg K$

Description

This command is used to fill a region of the CFD_DOMAIN with a high explosive. Explosives can be detonated using CFD_DETONATION. The pressure is defined as:

$\displaystyle{ p = A \left( 1 - \frac{\omega}{R_1 V} \right) \mathrm{e}^{-R_1 V} + B \left( 1 - \frac{\omega}{R_2 V} \right) \mathrm{e}^{-R_2 V} + \omega e}$

where $V$ is the ratio of current density to initial density and $e$ is the current internal energy per unit volume. The remaining afterburn energy at coordinate $\mathbf{x}$ evolves according to:

$\displaystyle{ \frac{\partial e_{ab}}{\partial t} (\mathbf{x},t) = -\frac{e_{ab}(\mathbf{x},t)}{t_{ab}} }$

Parameter type can be specified as a preset, USER, or as a material ID of MAT_EXPLOSIVE_JWL. In case a material ID is specified, the following parameters are extracted from the referenced command: density, JWL coefficients, energy per unit volume and detonation velocity. Available presets are listed below. The input parameters for these presets are presented on our website (Support > Verifier documentation > Verification of explosives).

Available presets:

$\begin{array}{ll} \textsf{ANFO} & \textsf{(Ammonium nitrate fuel oil)} \\ \textsf{C4} & \textsf{(Composition C-4)} \\ \textsf{COMPA} & \textsf{(Composition A-3)} \\ \textsf{COMPB} & \textsf{(Composition B, grade A)} \\ \textsf{HMX} & \\ \textsf{LX-10-1} & \\ \textsf{LX-14-0} & \\ \textsf{M46} & \\ \textsf{MCX-6100} & \\ \textsf{NSP-711} & \\ \textsf{OCTOL} & \textsf{(Octol 78/22)} \\ \textsf{PBXN-110} & \\ \textsf{PBXN-9010} & \\ \textsf{PETN} & \\ \textsf{TETRYL} & \\ \textsf{TNT} & \\ \end{array} $

Note that the material parameters ($\rho$, $A$, $B$, ...) only need to be specified if type = USER.

The E2C option is used to switch between FE and CFD formulations for the explosive. This can be done incrementally by eroding individual elements as they become too distorted, or on a signal using ACTIVATE_ELEMENTS. Removing all elements at the same time generally produces a more accurate solution.

Example

High explosive defined by preset, user and material

This example demonstrates the different options for parameter type. The model consists of three spherical C4 charges. The first CFD_HE command uses the preset, the second command uses a user defined explosive, and the third command uses data extracted from a MAT_EXPLOSIVE_JWL command with material ID = 3. The data specified in the user defined explosive and in the MAT_EXPLOSIVE_JWL command is identical to the data used in the preset.

*PARAMETER tend = 2e-5, "Termination time" R = 0.05, "HE charge radius" D = 0.25, "Distance between HE charges" L = 1.0 , "CFD domain size parameter" dx = 5e-3, "CFD cell size" *UNIT_SYSTEM SI *TIME %tend # # --- CFD --- # *CFD_DOMAIN 1 ALL, 0, %dx, 1 -%L/2, -%L/4, -%L/4, %L/2, %L/4, %L/4 0, 0, 0, 0, 0, 0 # *CFD_HE "Type specified as a preset" 1 C4, 1 *CFD_HE "Type specified as user" 2 USER, 2 1601, 609.8e9, 12.95e9, 4.5, 1.4, 0.25, 9.0e9, 8193 *CFD_HE "Type specified as a material ID" 3 3, 3 *MAT_EXPLOSIVE_JWL "C4" 3, 1601, 1.0e10, 0.3 1.0e7, 0, 0, 1.5, 2.0 609.8e9, 12.95e9, 4.5, 1.4, 0.25, 9.0e9, 8193 # *CFD_DETONATION "Preset" 1 -%D, 0, 0 *CFD_DETONATION "User" 2 0, 0, 0 *CFD_DETONATION "Material ID" 3 %D, 0, 0 # # --- GEOMETRIES --- # *GEOMETRY_SPHERE "Preset" 1 -%D, 0, 0, %R *GEOMETRY_SPHERE "User" 2 0, 0, 0, %R *GEOMETRY_SPHERE "Material ID" 3 %D, 0, 0, %R # # --- SENSORS --- # *OUTPUT_SENSOR "Preset" 1, CFD, -%D, 0, 0 *OUTPUT_SENSOR "User" 2, CFD, 0, 0, 0 *OUTPUT_SENSOR "Material ID" 3, CFD, %D, 0, 0 *END