# /SPHGLO

Block Format Keyword Describes the SPH global parameters.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/SPHGLO
${\alpha }_{sort}$ Maxsph Lneigh Nneigh Isol2sph

## Definitions

Field Contents SI Unit Example
${\alpha }_{sort}$ Security coefficient on search for neighbors, so that for each particle more than the actual neighbors are found. This allows reducing the computational time. 1

Maximum value is set to 0.5

Default = 0.25 (Real)

Maxsph Maximum number of ghost particles allowed to be created at one time. It is used to allocate memory for ghost particles creation. Since v14.0.220, this input is ignored and the memory is dynamically allocated. 2

(Integer)

Lneigh Maximum number of neighbors to be taken into account for the SPH approximation.

Default = 120, if Nneigh = 0

otherwise, = max(120,Nneigh)

(Integer)

Nneigh Maximum number of neighbors

Default = 120 (Integer)

Isol2sph Particle activation process method for Sol2SPH. 7
=0 (Default)
Set to 1.
=1
Switch of elements to particles based on part.
=2
Switch of elements to particles based on subset.

1. ${\alpha }_{sort}$ is a security coefficient which is used when searching for neighbors, so that for each particle more than the actual neighbors are found. This allows reducing the computational time.

Nevertheless, the number of neighbors found within the security distance should not be too large.

It is recommended to set the value of ${\alpha }_{sort}$ , so that neighbors next to the neighbors lying at distance 2h into the initial net will be retained (where h is the smoothing length defined into property).

This leads to ${\alpha }_{sort}$ =0.25 (default value), if the net is an hexagonal net and $h$ is the minimum distance between two particles into the net.

2. Maxsph is the maximum number of ghost particles which will be allowed to be created at one time. It is used to allocate memory for ghost particles creation.

Since v14.0.220, Maxsph is ignored and the memory is dynamically allocated.

Maxsph default's value is the number of SPH symmetry conditions multiplied by the number of particles, which corresponds to the case of all particles are symmetrized with respect to each conditions and is sufficient to treat any problem.

It is recommended to use the default value for Maxsph.

Nevertheless, all particles do not generally need to be symmetrized with respect to each condition and Maxsph default's value can lead in specific cases to a large over-estimation of the necessary memory (refer to Maximum Created Number of Ghost Particles ).

3. Nneigh is the maximum number of neighbors to be stored around each particle.

It determines the memory allowed for storing the neighbors within the security distance at each bucket sort (refer to Maximum Stored Number of Neighbors).

4. Lneigh determines the maximum number of particles participating to the SPH approximation around each particle. Thus, the number of particles participating to the SPH approximation around a particle, generally depends on the particle diameter $h$ , but is limited to Lneigh.
5. If Nneigh is less than 120, Nneigh is set to 120.

If Nneigh is not equal to 0 and less than Lneigh, Nneigh is set to Lneigh.

6. Setting Nneigh > Lneigh enables reducing the frequency of particles sorting.
7. For Sol2sph:

If Isol2sph=1, if an unreleased particle of a main solid element is within interaction distance of any particle of another solid element belonging to a different part, then both solid elements are deleted and their particles are released.

If Isol2sph=2 the switch is activated only if the solid elements belong to different subsets.