/DFS/DETCORD

Block Format Keyword Set burning times of explosive material elements along a neutral fiber of detonating cord. Neutral fiber is provided with an ordered group of nodes and numerically built by spline interpolation.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/DFS/DETCORD/`detcord_ID`/`unit_ID`
		`V`_DET		`T`_DET		`I`_opt		`mat_ID`	`grnod_ID`

Definitions

Field	Contents	SI Unit Example
`detcord_ID`	Detonator identifier (Integer, maximum 10 digits)
`unit_ID`	Unit Identifier (Integer, maximum 10 digits)
`V`_DET	(Optional) Detonation velocity. = 0.0 (Default) Means instantaneous detonation. (Real)	$[\frac{m}{s}]$
`T`_DET	Detonation time. Default = 0.0 (Real)	$[s]$
`I`_opt	(Optional) Formulation flag. = 0 Set to 3. = 1 Piecewise linear using `V`_DET. = 2 Instantaneous detonation. = 3 (Default) Ignition from the first node and propagation along neutral fiber computed with Spline interpolation. Using JWL DCJ parameter or `V`_DET if defined. (Integer)
`mat_ID`	Explosive identifier. = 0 (Default) All "JWL" material laws are included. (Integer)
`grnod_ID`	Ordered node group identifier. Must use /GRNOD/NODENS. (Integer)

Example (TNT)

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/DFS/DETCORD/11
#                                   VDET                TDET      Iopt               MatID   GrNodID
                                     1.0                10.0         0                  55        21
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/JWL/55
TNT - data from example 46 with unit: (g-mm-mus) - Standard JWL , No Afterburning
#              RHO_I
                1.63
#                  A                   B                  R1                  R2               OMEGA
              3.7121               .0323                4.15                 .95                  .3
#                  D                P_CJ                  E0                Eadd   I_BFRAC     Q_OPT
                .693                 .21                 .07                   0         0         0		
#                 P0                 Psh
                   0                   0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/EULER/MAT/55
#               Flrd
                 0.0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#enddata

Comments

Catmull-Rom Spline interpolation ¹ is used to build the neutral fiber with the provided group of nodes. Centripetal-Catmull-Rom method ² is chosen because it has several desirable mathematical properties: it prevents from loops, self-intersections, cups, and it follows control points more tightly. ³
Ignition starts from the cord section which contains the first node and is propagated along the neutral fiber. Each section of the cord is supposed to have the same ignition time depending on its position along the neutral fiber. For each element, centroid is projected on neutral fiber and ignition time is deduced from position along neutral fiber.
Detonation times are available in the Starter output file (I_PRI ≥ 3).
Burn fractions are available in time history file with /TH/BRIC card and the BFRAC contour output keyword.
Detonation velocity is taken from the JWL material law. Cord detonation is instantaneous.

¹ E. Catmull and R. Rom. “A class of local interpolating splines. Computer Aided Geometric Design”, pages 317–326, 1974

² P. J. Barry and R. N. Goldman. “A recursive evaluation algorithm for a class of catmull-rom splines”. SIGGRAPH Computer Graphics, 22(4):199–204, 198

³ Cem Yuksel, Scott Schaefer, John Keyser, “On the Parameterization of Catmull-Rom Curves”, NSF grant CCF-0702409