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PARTICLE_SPH

Particle

*PARTICLE_SPH
"Optional title"
sid, $N_p^{sid}$
mid, gid, correction, $s$, $dsf$, E2S, slide, $t_{end}$
$\Delta$

Parameter definition

Variable
Description
sid
Subdomain ID
$N_p^{sid}$
Number of particles
default: not used
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
E2S
SPH particles are activated as elements are eroded (element to SPH mapping)
options:
0 $\rightarrow$ no
1 $\rightarrow$ yes (amorphous unit cell)
2 $\rightarrow$ yes (hexagonal close packed unit cell)
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
$\Delta$
Target particle spacing (only used if E2S>0)
default: automatic

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.

Material models presented with an SPH badge in the command manual are supported by SPH.

Smoothing length and dynamic repositioning

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 $s=2.5$. If an SPH particle becomes isolated from its neighbours, it is automatically deactivated.

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.

Number of particles and Erode-to-SPH

$N_p^{sid}$ is optional if E2S=0. If it is not specified, then this sub-id will use a fraction of the the total number of particles $N_p$ defined in PARTICLE_DOMAIN.

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 $N_p$ will be allocated to that specific subdomain.

When Erode-to-SPH (E2S) is enabled (i.e. E2S>0), $N_p^{sid}$ must be specified. It then defines the maximum number of SPH particles that can be activated to replace eroded elements. $\Delta$ is the target SPH node spacing, meaning that $(1/\Delta)^3$ SPH particles per unit volume of eroded elements will be generated. E2S requires that gid refers to a GEOMETRY_PART.

SPH-to-SPH interaction

By default, SPH particles using different material ID's will merge when coming into contact. However, this interaction can be changed to friction free sliding by setting slide=1.