Smoothed-Particle Hydrodynamics (SPH) Model Reference

The Smoothed-Particle Hydrodynamics (SPH) model makes accessible the physics models and setting to define properties and disrcetization for SPH multiphase simulations.

表 1. Smoothed-Particle Hydrodynamics (SPH) Model Reference
Theory 多相流的平滑颗粒流体动力学 (SPH) 法.
Provided By [physics continuum] > Models > Multiphase Model
Example Node Path Continua > Physics 1 > Models > Smoothed-Particle Hydrodynamics (SPH)
Requires
Pre-requisite selections:
  • Time: Implicit Unsteady
  • Space: Three Dimensional
  • Material: Multiphase
  • Multiphase Model: Smoothed-Particle Hydrodynamics (SPH)
Properties None.
Activates Physics Models

Automatically selected models:

Multiphase Interaction (activated by selecting the Multiphase model)

Incompressible Flow (ISPH)

Solution Interpolation

Adaptive Time-Step
Region Settings Physics Conditions:
  • Initial Condition Option
  • Motion Specification Source Option
Physics Values:
  • Particle Base Size
  • Direct Rotating Option
  • Particle Generation
  • Part Orientation

See Region Settings.
Field Functions None.

Region Settings

The following setting applies to each surface region.

Initial Condition Option
Lets you customize initial conditions for an individual region.

See Setting Initial Conditions for a Particular Region.

Motion Specification Option
Method Corresponding Physics Value Nodes
Direct Rotating Motion Values

Allow you to define rotating motions directly within the region. It allows you to add rotations independently to different parts of a region.
Direct Rotating Motion
This option allows for part subgrouping, that is, it allows you to define the rotation values independently for each geometry part of the same region.
Direct Rotating Motion Values
Specifies the properties for the rotation.

See Defining Direct Rotating Motion.
Particle Base Size
Specifies the particle size (disretization length) for spacing the fluid particles in the domain. This value represents the target size for the Cartesian lattice used in particle generation.
Particle Generation

Generates particles within the geometry part that represents the initial shape and position of the liquid. The total number of particles is computed by the solver based on the initial liquid volume and particle base size. The particles are distributed uniformly and provide the discretization of the liquid.

Parts
Selects the geometry part in which to generate the particles that define the initial fluid domain. The surface of the geometry part must be free of errors and completely closed.
Boundary Distance Ratio
Specifies the initial minimum distance ratio between the particle center and the boundary surface of the initial fluid volume.
Grid Offset Ratio
Specifies the offset ratio between the particle center and the origin of the fluid at initialization. The grid offset ratio is aligned with a Cartesian pattern so that it suitable for block-shaped initial fluid volumes.

The following image illustrates the basic concept of the grid offset and boundary distance ratios. These values are in relation to the surface of the initial fluid volume (red), the offset distance determined the actual particle volume (green). The ratios are obtained by dividing the grid offset and boundary distance by the particle size.

To enhance stability in the initial stages of the simulation, adjust these properties to shift particles slightly inward within the liquid domain.

Part Orientation

Provides the option to reverse the direction of the surface normal vectors in relation to the fluid location. By default, the surface normals are oriented inward for closed geometry parts, that is, the positive side of a boundary is facing outwards. SHP particles interact with a boundary only on the positive side. Therefore, for external flow around a closed geometry part, the default orientation is correct. However, for internal flow within the geometry part, the default orientation is incorrect and must be reversed.

Specify by Part Subgroup
Available when Allow Per-Part Values is activated for the Region > [surface region].
When activated, lets you subgroup individual geometry parts that are assigned to the same surface region. The By Part Subgroup node appears in the simulation tree with a predefined Subgroup node.
Reverse Orientation
When activated, it reverses the direction of the surface normals for the subgroup part.