Phases
In the phases section the material parameters are defined for different SPH components.
The name of the phases as given/used in SimLab is not important, only the material ID in SimLab that relates to the phase number as defined here. The first phase definition in the configuration file defines the properties of the SPH particles with the material ID “1”, the second group for the material ID “2”, and so on.
For more information, refer to Solver Features in the Theory Manual.
Commands
phases
{
phase
{
name Water
type FLUID
rho_0 1000.
dyn_visc 1.e-3
surf_ten 0.1
temp_0 0.
heat_cond 0.
heat_cap 0.
evolve_temp false
rho_compr 0.01
pc_factor 1.0
print_info false
print_phase true
cs 100
rm_rho_theta 1.1
init_vel “0.0 0.0 0.0”
}
phase
{
name Housing
type WALL
heat_cond 0.0
heat_cap 0.0
temp_0 0.0
evolve_temp false
noSlip true
print_info true
print_phase true
adhesionCoeff 0.01
contact_angle 90.0
fluidContactPhase 1
makesubphase true
init_vel “0.0 0.0 0.0”
}
phase
{
name Something_moving
type MOVINGWALL
rho_0 1.0
heat_cond 0.0
heat_cap 0.0
temp_0 0.0
evolve_temp false
noSlip true
print_info true
print_phase true
adhesionCoeff 0.01
contact_angle 90.0
fluidContactPhase 1
makesubphase true
init_vel “0.0 0.0 0.0”
}
…
}
Definitions
Command | Contents | SI Unit Example |
---|---|---|
name | The name of this phase. Note: This does not need to match the
component name in SimLab.
Options
|
|
type | The type of the phase defines the physical behavior. Attention: This property is mandatory.
Options
|
|
rho_0 | The reference density of this phase. This is the initial
density of all particles of this phase. Warning: In
case that the body is defined as rigid
(fluidCoupledMotion), this value is
overridden by a density which is calculated based on the
specified mass of the body (body_mass)
and the total number of particles representing the phase in
question.
Default = 1.0 |
|
dyn_visc | The dynamic viscosity of this phase in [kg / (m s), Pa
s]. Warning: If
viscTempCoupling
(temperature-viscosity coupling) is set to true, this value
will be ignored since it is specifically defined by
temperature-viscosity models which determine the viscosity
of the fluid.
Note: For more information, refer to
Viscosity Models.
Default = 0.0 |
|
heat_cap | The specific heat capacity at constant pressure
(Cp) of this phase. Related Commands
Default = 0.0 |
[J/kg/K] |
heat_cond | The heat conductivity of this phase. Related Commands
Default = 0.0 |
[W/m/K] |
evolve_temp | This flag can be used to set the temperature of a phase
constant, or to allow it to evolve using the energy equation. Options
Related Commands
Default = false |
|
noSlip | Switch to enable the WALL or
MOVINGWALL to become a slip or no-slip
boundary condition. Options
Default = true |
|
temp_0 | The initial temperature of a phase in Kelvin [K]. Related Commands
Default = 273.15 |
|
surf_ten | The surface tension coefficient [N/m]. Note:
Related Commands
Default = 0.0 |
|
rho_compr | The compressibility of the fluid. Note: Following the weakly
compressible approach, the admissible density variation is 1
percent. For example, rho_compr =
0.01.
CAUTION: Changing this value without
an advanced understanding could have undesired
consequences.
Default = 0.01 |
|
pc_factor | Background correction pressure associated with the transport
velocity formulation. It can have an arbitrary value, however it
is generally recommended to keep it on the same order of
magnitude of the
p0 (base
pressure). Related Commands
Default = 1.0 |
|
print_info | If this Boolean flag is set to true, an additional file is
written during the simulation with the filename
name_info.txt
(name is the phase
name as defined earlier). The content is
written every #N steps (see dt_phaseinfo) and
contains information on for example the forces, torques, kinetic
energy and center-of-mass of this phase. Options
Default = false |
|
print_phase | This Boolean flag switches the output of this phase on or
off. This switch is useful to limit the amount of output since
wall particles, for example, do not change their position in
time and might not be necessary in the output. Options
Default = false |
|
cs | Specify the speed of sound in the FLUID
phases (individually). Note: By default, this parameter is left
out of the phase definition in which case the code will use
the automatically calculated speed of sound based on the
ref_vel and
rho_compr. Speed of sound can have a
profound influence on the overall behavior of the simulation
and is generally considered an advanced
parameter.
CAUTION: Defining this value
without an advanced understanding could have undesired
consequences.
|
|
rm_rho_theta | Scaling parameter designed to enable local particle density
reinitialization once the threshold of
rho_0*rm_rho_theta is
exceeded. Restriction: This parameter is only
available and meaningful when Riemann scheme is
used.
Tip: Suggested best practices
maintain the stability of the Riemann formulation in
multiphase simulations.
|
|
rm_beta | Numerical parameter used in the low-dissipation Riemann
solver. It determines the level of numerical dissipation being
introduced in the pair-wise interactions. Tip:
Default = 3.0
Tip: Reducing this value increases the amount of dissipation. The value
of 3.0 is adopted from academic sources.
CAUTION: Changing this value without an advanced
understanding could have undesired
consequences.
|
|
adhesionCoeff | Scalar value that determines the strength of adhesion force
of the fluid particles to the material. Tested range goes from
0.001 to 2.0. Note: This is a numerical parameter, so it does
not have its physical counterpart
defined.
Default = 0.0 |
|
contact_angle | This is the contact angle in degrees as seen from the fluid
phase. Warning:
Default = 90.0 Tip: For more
information, refer to Contact Angle.
|
|
fluidContactPhase | Use this command in the phase definition to track the amount
of time the WALL or MOVINGWALL
phase spends in contact with the specified fluid phase. The time
data is written in the respective particle output file. Attention: This command is only valid for
WALL and MOVINGWALL
type phases, whereas the tracked phase can only be a
FLUID.
|
|
makesubphase | Setting this value to true enables more
efficient treatment of the phases when executing the main GPU
calculations. The performance gain increases as the number of
the phases in the case increases. Tip:
Default = true |
|
init_vel | This command can be applied to all phase types. Attention:
Default = “0.0 0.0 0.0” |