The
Define/Models/Discrete Phase... menu item opens the
Discrete Phase Model panel.
Discrete Phase Model Panel
The
Discrete Phase Model panel allows you to set parameters related to the calculation of a discrete phase of particles. See Chapter
22 for details.
Controls
Interaction
contains parameters used for performing coupled calculations of the continuous and discrete phase flow. See Section
22.15.2 for details.
Interaction with Continuous Phase
enables a coupled calculation of the discrete phase and the continuous phase.
Update DPM Sources Every Flow Iteration
enables calculation of particle source terms at every DPM Iteration. It is recommended for unsteady simulations.
Number of Continuous Phase Iterations per DPM Iteration
allows you to control the frequency at which the particles are tracked and the DPM sources are updated.
Particle Treatment
contains options for choosing to treat the particles in an unsteady or a steady fashion.
Unsteady Particle Tracking
enables unsteady tracking of particles.
Track with Fluid Flow Time Step
enables the use of fluid flow time steps to inject the particles.
Inject Particles at
contains parameters to decide when to inject the particles for a new time step.
Particle Time Step
enables injection of particles for every particle time step.
Fluid Flow Time Step
enables injection of particles for every fluid flow time step. In any case, the particles will always be tracked in such a way that they coincide with the flow time of the continuous flow solver.
Particle Time Step Size
specifies particle time step size for the calculation.
Number of Time Steps
allows you to specify the number of time steps for the calculation.
Clear Particles
clears the particles that are currently in the domain.
Tracking
contains two parameters to control the time integration of the particle trajectory equations.
Tracking Parameters
contains parameters that control the tracking of particle trajectories. One simple rule of thumb to follow when setting the two parameters below is that if you want the particles to advance through a domain of length
, the
Length Scale times the number of
Max. Number of Steps should be approximately equal to
. See Section
22.15.1 for details about the items below.
Max. Number of Steps
is the maximum number of time steps used to compute a single particle trajectory via integration of Equations
22.2-1 and
22.15-1.
Specify Length Scale
when enabled allows you to specify the length scale.
Length Scale
controls the integration time step size used to integrate the equations of motion for the particle. It appears only when the
Specify Length Scale option is enabled.
Step Length Factor
specifies the value of
in Equation
22.11-2.
Drag Parameters
allows the setting of the drag law used in calculating the force balance on the particles. See Section
22.2.1 for details on the items below.
Drag Law
is a drop-down list containing three choices:
spherical
assumes that the particles are smooth spheres.
nonspherical
assumes that the particles are not spheres, but are all identically shaped. The shape is specified by the
Shape Factor.
Stokes-Cunningham
is for use with sub-micron particles. A
Cunningham Correction is added to Stokes' drag law to determine the drag.
high-Mach-number
is similar to the spherical law with corrections to account for a particle Mach number greater than 0.4 or a particle Reynolds number greater than 20.
dynamic-drag
accounts for the effects of droplet distortion. This drag law is available only when one of the droplet breakup models is used in conjunction with unsteady tracking. See Section
22.6 for details.
Shape Factor
specifies the shape of the particles when
nonspherical is selected as the
Drag Law (
in Equation
22.2-9). It is the ratio of the surface area of a sphere having the same volume as the particle to the actual surface area of the particle. The shape factor value cannot be greater than
1.
Cunningham Correction
(
in Equation
22.2-11) is used with Stokes' drag law to determine the force acting on the particles when the particles are sub-micron size. It appears when
Stokes-Cunningham is selected as the
Drag Law.
Physical Models
contains optional discrete phase models and their relevent parameters.
Options
contains additional models that can be included in the calculation. See Section
22.11.5 for more information.
Particle Radiation Interaction
includes the effect of radiation heat transfer to the particles (Equation
13.3-13). You will also need to define additional properties for the particle materials (emissivity and scattering factor), as described in Section
22.14.2.
This item appears only if the P-1 or discrete ordinates model is selected in the
Radiation Model panel.
Thermophoretic Force
enables the inclusion of a thermophoretic force on the particles as an additional force term. See Section
22.2.1 for details.
Brownian Motion
enables the incorporation of the effects of Brownian motion. See Section
22.2.1 for details.
Saffman Lift Force
enables the inclusion of Saffman's lift force (lift due to shear) as an additional force term. See Section
22.2.1 for details.
Erosion/Accretion
enables the monitoring of erosion/accretion rates at wall boundaries. See Section
22.11.5 for details. This item appears only if
Interaction with Continuous Phase is enabled.
Two-Way Turbulence Coupling
enables the effect of change in turbulent quantities due to particle damping and turbulence eddies.
Spray Model
contains parameters that control droplet breakup and collision. (This section of the panel appears only if
Unsteady Tracking is enabled.)
Droplet Collision
includes the effect of droplet collisions. See
Section
22.7.1 for details.
Droplet Breakup
includes the effects of droplet breakup.
Breakup Model
contains parameters that control droplet breakup. (This item appears only if
Droplet Breakup is enabled.)
TAB
enables the Taylor Analogy Breakup (TAB) model, which is applicable to many engineering sprays. This method is based upon Taylor's analogy between an oscillating and distorting droplet and a spring mass system. See Section
22.7.2 for details.
Wave
enables the wave breakup model, which considers the breakup of the injected liquid to be induced by the relative velocity between the gas and liquid phases. See Section
22.7.2 for details.
Breakup Constants
contains model constants used in the equations for spray breakup. (This item appears only if
Droplet Breakup is enabled.)
y0
(only for the TAB model) is the constant
in Equation
22.7-17.
Breakup Parcels
is the number of child parcels the droplet is split into, as described in Section
22.7.2.
B0
(only for the wave model) is the constant
in Equation
22.7-43.
B1
(only for the wave model) is the constant
in Equation
22.7-45.
UDF
contains parameters that can be used to customize the discrete phase model using UDF. See the separate
UDF Manual for details about user-defined functions.
User-Defined Functions
lists will show available user-defined functions that can be selected to customize the discrete phase model.
Body Force
contains a drop-down list of user-defined functions available for including additional body forces.
Erosion/Accretion
contains a drop-down list of user-defined functions available for incorporating non-standard erosion rate definitions. This item will appear only when the
Erosion/Accretion option has been enabled.
Scalar Update
contains a drop-down list of user-defined functions available for calculating or integrating scalar values along the particle trajectory.
Source
contains a drop-down list of user-defined functions available for modifying interphase exchange terms.
Spray Collide Function
contains a drop-down list of user-defined functions available for modifying spray collide function.
DPM Timestep
contains a drop-down list of user-defined functions available for modifying DPM time step.
User Variables
lists the user input variables.
Number of Scalars
sets the number of scalar values used in the calculations with user-defined functions.
Numerics
tab gives you control over the numerical schemes for particle tracking as well as solutions of heat and mass equations. See Section
22.11.7 for details.
Options
contains parameters of solutions of heat and mass equations.
Accuracy Control
enables the solution of equations of motion within a specified tolerance.
Tolerance
is the maximum relative error which has to be achieved by the tracking procedure.
Max. Refinements
is the maximum number of step size refinements in one single integration step. If this number is exceeded the integration will be conducted with the last refined integration step size.
Coupled Heat-Mass Solution
enables the solution of the particle heat and mass equations using a stiff, coupled ODE solver with error tolerance control. See Section
22.11.7 for details.
Track in Absolute Frame
enables tracking the particles in the absolute reference frame.
Tracking Scheme Selection
contains parameters for selection of numerical schemes.
Automated
enables a mechanism to switch in an automated fashion between numerically stable lower order schemes and higher order schemes, which are stable only in a limited range.
High Order Scheme
can be chosen from the group consisting of
trapezoidal and
runge-kutta scheme.
Low Order Scheme
consists of
implicit and the exponential
analytic integration scheme.
Tracking Scheme
allows to choose any of the tracking schemes. You also can combine each of the tracking schemes with Accuracy Control. It is selectable only if
Automated is switched off.
Parallel
contains parameters that control the compute nodes for performing discrete phase calculations in parallel. See Section
22.11.9 for details.
Message Passing
enables cluster computing and also works on shared memory machines. With this option, the compute node processes themselves perform the particle work on their local partitions and particle migration to other compute nodes is implemented using message passing primitives. No special requirements are placed on the host machine. Note that this model is not available if the
Cloud Model option is turned on under the
Turbulent Dispersion tab of the
Set Injection Properties panel. The
Message Passing option is irrelevant for the serial
FLUENT code while the
Shared Memory option remains valid.
Shared Memory
allows you to specify parameters for performing the calculations on shared-memory multiprocessor machine.
Workpile Algorithm
specifies that the discrete phase calculations are to be performed on a shared-memory multiprocessor machine.
Number of Threads
specifies the number of threads to be used in performing the particle calculations. By default, this parameter is equal to the number of compute nodes you specified for the parallel solver. (This item appears only if
Workpile Algorithm is enabled.)