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The region command is used to label a group of nodes and elements. This command is also used to assign rayleigh damping parameters to the nodes and elements in this region.
region $regTag <-ele ($ele1 $ele2 ...)> <-eleRange $startEle $endEle> <-ele all> <-node ($node1 $node2 ...)> <-nodeRange $startNode $endNode> <-node all> <-rayleigh $alphaM $betaK $betaKinit $betaKcomm>
The region is specified by either elements or nodes, not both. If elements are defined, the region includes these elements and the all connected nodes. If nodes are specified, the region includes these nodes and all elements whose external nodes are prescribed.
$regTag |
unique integer tag |
$ele1 $ele2 ... |
tags of elements -- selected elements in domain (optional, default: omitted) |
$startEle $endEle |
tag for start and end elements -- range of selected elements in domain (optional, default: all) |
all |
all elements in domain (optional & default) |
$alphaM $betaK $betaKinit $betaKcomm |
Arguments to define Rayleigh damping matrix (optional, default: zero) |
OR:
$regTag |
unique integer tag |
$node1 $node2 ... |
node tags -- select nodes in domain (optional, default: all) |
$startNode $endNode |
tag for start and end nodes -- range of nodes in domain (optional, default: all) |
all |
all nodes in domain (optional & default) |
$alphaM $betaK $betaKinit $betaKcomm |
Arguments to define Rayleigh damping matrix (optional, default: zero) |
The damping matrix D is specified as a combination of stiffness and mass-proportional damping matrices:
D = $alphaM * M + $betaK * Kcurrent +$betaKinit * Kinit + $betaKcomm * KlastCommit
The mass and stiffness matrices are defined as:
M |
mass matrix used to calculate Rayleigh Damping |
Kcurrent |
stiffness matrix at current state determination used to calculate Rayleigh Damping |
Kinit |
stiffness matrix at initial state determination used to calculate Rayleigh Damping |
KlastCommit |
stiffness matrix at last-committed state determination used to calculate Rayleigh Damping |
NOTE: a region is defined by either nodes or elements, not both.
EXAMPLE:
region 1 -ele 1 5 -eleRange 10 15
region 2 -node 2 4 6 -nodeRange 9 12
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