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PARTICLE_DOMAIN

Particle

*PARTICLE_DOMAIN
entype, enid, N${}_p$, $\mu$, $pfac$, $c_{dec}$, xsmooth, $t_{end}$
$x_0$, $y_0$, $z_0$, $x_1$, $y_1$, $z_1$
bc${}_{x0}$, bc${}_{y0}$, bc${}_{z0}$, bc${}_{x1}$, bc${}_{y1}$, bc${}_{z1}$
$\delta_0^{max}$, ctype, kernel

Parameter definition

Variable
Description
entype
Structure entity type for particle structure interaction
options: P, PS, ALL
enid
Structure entity ID
N${}_p$
Total number of particles
$\mu$
Particle-structure contact friction
$pfac$
Particle-structure contact stiffness
quantity: Stiffness
$c_{dec}$
Impulse transfer smoothing time (gas-structure)
quantity: Time
xsmooth
Spatial impulse smoothing level
quantity: Impulse
default: inactive
$t_{end}$
Particle deactivation time
quantity: Time
$x_0$
Particle domain minimum x-coordinate
quantity: Length
$y_0$
Particle domain minimum y-coordinate
quantity: Length
$z_0$
Particle domain minimum z-coordinate
quantity: Length
$x_1$
Particle domain maximum x-coordinate
quantity: Length
$y_1$
Particle domain maximum y-coordinate
quantity: Length
$z_1$
Particle domain maximum z-coordinate
quantity: Length
bc${}_{x0}$
Boundary condition at $x=x_0$
options:
0 $\rightarrow$ free
1 $\rightarrow$ rigid reflecting boundary
2 $\rightarrow$ fully clamped (SPH only)
bc${}_{y0}$
Boundary condition at $y=y_0$
options:
0 $\rightarrow$ free
1 $\rightarrow$ rigid reflecting boundary
2 $\rightarrow$ fully clamped (SPH only)
bc${}_{z0}$
Boundary condition at $z=z_0$
options:
0 $\rightarrow$ free
1 $\rightarrow$ rigid reflecting boundary
2 $\rightarrow$ fully clamped (SPH only)
bc${}_{x1}$
Boundary condition at $x=x_1$
options:
0 $\rightarrow$ free
1 $\rightarrow$ rigid reflecting boundary
2 $\rightarrow$ fully clamped (SPH only)
bc${}_{y1}$
Boundary condition at $y=y_1$
options:
0 $\rightarrow$ free
1 $\rightarrow$ rigid reflecting boundary
2 $\rightarrow$ fully clamped (SPH only)
bc${}_{z1}$
Boundary condition at $z=z_1$
options:
0 $\rightarrow$ free
1 $\rightarrow$ rigid reflecting boundary
2 $\rightarrow$ fully clamped (SPH only)
$\delta_0^{max}$
Max allowed initial contact penetration
quantity: Length
default: 0
ctype
Particle-structure contact type
options:
0 $\rightarrow$ point to surface
1 $\rightarrow$ sphere to surface
kernel
SPH kernel function type
options:
0 $\rightarrow$ Cubic spline
1 $\rightarrow$ Wendland C2
2 $\rightarrow$ Wendland C4
default: Cubic spline

Description

This command is used to define a global domain and general settings for SPH and discrete particles. $N_p$ defines the total number of particles. The distribution of particles to the different sub-domains (PARTICLE_HE, PARTICLE_AIR, PARTICLE_SOIL, PARTICLE_SPH) is automatic.

The automatic distribution of particles ensures a good particle mass balance, which is important for particle–particle interactions. An inadequate particle mass ratio can lead to energy errors (SPH–SPH or SPH–soil interactions) or significant numerical noise (gas–soil or gas–SPH interactions). However, there are situations where it is desirable to control the number of particles assigned to each subdomain. To address these cases, particles can also be allocated to each subdomain individually, directly via the commands PARTICLE_AIR, PARTICLE_HE, PARTICLE_SOIL and PARTICLE_SPH.

Particles leaving the particle domain are deactivated.

Particles overlapping the underlying Finite Element mesh by more than $\delta_0^{max}$ will be removed from the model during initialization.

When working with SPH and materials with significanlty different properties (density and/or stiffness) or with different node masses, it is adviceable to set slide=1 (in PARTICLE_SPH). Sticking between materials with significanlty different properties is better modelled using MERGE than through SPH kernel function interactions.

The spatial impulse smoothing option smears out transferred impulses (in the particle-structure interaction) to more than one element face. xsmooth is an integer that defines the size of the region where impulses are distributed. xsmooth=1 means that only the direct neighbours of an impacted face will share a fraction of the impulse. With xsmooth=2 the impulse is distributed to both the direct and to the second level neighbours. Typical xsmooth parameters are in the range 1 to 10.

For now, the SPH kernel function type is global. Note that the same kernel type should be used in GENERATE_PARTICLE_DISTRIBUTION.