#### PARTICLE_SPH

###### Particle
*PARTICLE_SPH
"Optional title"
sid
mid, gid, correction, $s$, $dsf$, ., slide, $t_{end}$
##### Parameter definition
VariableDescription
sid Subdomain ID
mid Material ID
gid Geometry ID
correction Dynamic SPH node coordinate correction
options:
0 $\rightarrow$ weak correction
1 $\rightarrow$ strong correction
2 $\rightarrow$ no correction
$s$ Smoothing length scale factor
default: 2.5
$dsf$ Particle density scale factor (particles per unit volume)
default: 1
slide Sliding contact flag
options:
0 $\rightarrow$ full merge
1 $\rightarrow$ sliding only
$t_{end}$ Particle deactivation time or FUNCTION (fcn)
options: time or fcn
default: not used
##### Description

SPH subdomain definition.

The subdomain ID (sid) determines in which order particles are filled into the global domain. In case subdomains are overlapping, the domain with the largest ID will overwrite (remove) particles belonging to domains with lower domain ID's.

The smoothing length (radius) is defined as:

$\displaystyle{ R = s \cdot h }$

where $h$ is the initial SPH node spacing and the default value of $s=2.5$.

There is, by default, a dynamic repositioning of SPH coordinates that helps supressing tensile instability modes. This feature can be turned off by setting correction$=2$.

The SPH particle density scale factor $dsf$ is optional and it is used to control the relative particle density (number of particles per unit volume) in the different subdomains. Increasing $dsf$ for a subdomain means that a larger fraction of the total number of particles will be allocated to that specific subdomain.

By default, SPH particles belonging to different subdomains will merge when coming into contact. However, this interaction can be changed to friction free sliding by setting slide $=1$.