Segregated Fluid Energy Models Reference
There are three Segregated Fluid Energy models, which are companion models to the Segregated Flow model: the Segregated Fluid Enthalpy, Segregated Fluid Temperature, and Segregated Fluid Isothermal models.
The Segregated Fluid Enthalpy model solves the total energy equation Eqn. (1658) with chemical thermal enthalpy as the solved variable. Temperature is then computed from enthalpy according to the equation of state. This model is recommended for any simulation involving combustion. It is required with the flamelet combustion models.
The Segregated Fluid Temperature model solves the total energy equation Eqn. (1658) with temperature as the solved variable. Enthalpy is then computed from temperature according to the equation of state. This model is appropriate for simulations that do not involve combustion.
The Segregated Fluid Isothermal model keeps the temperature in the continuum constant. For problems where the temperature variations are small and negligible, it would be computationally expensive to solve an ordinary energy transport equation when it would yield a nearly constant field of temperature. Hence, Simcenter STAR-CCM+ includes the isothermal energy option to provide a constant temperature field for all models that require temperature.
Model Names and Abbreviations | Segregated Fluid Enthalpy | SFE | |
Segregated Fluid Temperature | SFT | ||
Segregated Fluid Isothermal | SFI | ||
Theory | See Fluid Flow and Heat Transfer. | ||
Provided By | |||
Example Node Path | |||
Requires |
If a flamelet combustion model is selected, Segregated Fluid Enthalpy is selected automatically (when Auto-select recommended physics models is activated). |
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Properties |
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Activates | Physics Models | Optional Models: Boiling, Circumferential Heat Flux Averaging, Thermal Comfort, Thin Film | |
Model Controls (child nodes) |
See Model Controls. |
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Material Properties |
See Material Properties. |
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Reference Values |
See Reference Values. |
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Initial Conditions |
See Initial Conditions. |
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Boundary Inputs | See Boundary Settings (SFE, SFT). | ||
Region Inputs |
See Region Settings (SFE, SFT) |
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Interface Inputs | See Interface Settings (SFE, SFT). | ||
Monitors |
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Solvers |
See Solvers. |
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Report Options |
See Reports. |
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Field Functions | For SFE
and SFT:
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Segregated Fluid Energy Models Properties
- Continuum Temperature
- Specifies the temperature of the continuum.
- Convection
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Sets the discretization scheme that Simcenter STAR-CCM+ uses for computing the convection flux on a cell face in appropriate transport equations. More information is given in the related topic for the Convection Term:
- 1st-Order: First-order upwind scheme. This scheme scales the transported quantity by the upstream or downstream mass flowrate depending on flow direction. Only use when a higher-order scheme fails to give convergence, or in order to obtain an initial solution before switching to a higher-order scheme.
- 2nd-Order: Second-order upwind scheme. This scheme introduces linear interpolation of cell values on either side of the upstream or downstream face. Using this scheme can lead to poorer convergence properties, but gives accuracy as good as or better than the first-order scheme.
- MUSCL 3rd-order/CD: Hybrid MUSCL third-order/central-differencing. Adds the Bounded Differencing sub-node.
- Flow Boundary Diffusion
- When activated, this property includes the flow-boundary diffusion fluxes (or viscous fluxes for flow models) as given by Eqn. (899). This property is activated by default.
- Secondary Gradients
- There are two sources of secondary gradients in
Simcenter STAR-CCM+ flow solvers:
- boundary secondary gradients for diffusion
- interior secondary gradients for diffusion at cell faces
Use this property to control which gradients are included in the solver. On gives both gradients while Off excludes them. Interior Only and Boundaries Only select the corresponding gradients.
Model Controls
- Bounded Differencing
- Sub-node that becomes available when you set Convection to MUSCL 3rd-order/CD.
Material Properties
- Thermal Conductivity
- Specifies the thermal conductivity of the fluid.
Reference Values
- Maximum Allowable Temperature
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The largest temperature value that is permitted anywhere in the continuum.
The Energy models (Coupled Energy, Coupled Solid Energy, Segregated Solid Energy, Segregated Fluid Enthalpy, Segregated Fluid Isothermal, Segregated Fluid Temperature) limit temperature corrections such that the corrected value does not exceed this maximum. If this occurs, a message is printed to the Output window.
- Minimum Allowable Temperature
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The smallest temperature value that is permitted anywhere in the continuum.
The Energy models (Coupled Energy, Coupled Solid Energy, Segregated Solid Energy, Segregated Fluid Enthalpy, Segregated Fluid Isothermal, Segregated Fluid Temperature) limit temperature corrections such that the corrected value does not go below this minimum. If this occurs, a message is printed to the Output window.
Initial Conditions
- Static Temperature
- Sets the initial static temperature in the continuum.
Boundary Settings
Note | Boundary types that do not require setting any conditions or values are not listed. |
- Mass Flow Inlet, Stagnation Inlet
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- Total Temperature
- The total temperature at the boundary.
- Velocity Inlet, Pressure Outlet, Free Stream
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- Static Temperature
- The static temperature at the boundary.
- Wall
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- Circumferential Averaging of Energy
- When On, activates averaging of
the heat flux between a boundary and its region with
relative rotation between them—for example, a stationary
boundary and a fluid in a rotating region. See Energy Averaging for Rotating Fluids with Stationary Wall Boundaries. The default is Off.
This option becomes available only when the tangential velocity of the wall boundary is different from the angular velocity of the fluid region. This velocity difference can be achieved by one of the following:
- The wall boundary is associated with a reference frame different from the Region Reference Frame and the rotation vector (= rotation axis x rotation rate) between the two reference frames is different. The fluid region can rotate by defining a moving reference frame. For more information, see Reference Frames.
- The wall boundary is associated with the same reference frame as the fluid region, but Tangential Velocity Specification is set to a different velocity.
This setting is not compatible with the Circumferential Heat Flux Averaging model, Porous Media models, or Eulerian multiphase models except for the Volume of Fluid (VOF) model.
- Thermal Specification
- Allows you to determine how the energy flow across the boundary is specified.
- User Wall Heat Flux Coefficient Specification
- Controls whether to specify the heat flux relationship at the boundary.
- Baffle Interface Boundary, Porous Baffle Interface Boundary, Contact Interface Boundary
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- User Wall Heat Flux Coefficient Specification
- As for Wall.
- Mapped Contact Interface Boundary
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- Static Temperature
- Automatically sets the static temperature for use with the temperature thermal boundary condition. Uses the Mapped Temperature method.
Region Settings
The following region values and conditions apply to fluid and porous regions (SFE, SFT):
- Heat Exchanger UAL
- For a Fluid-Solid Type Dual Stream Heat Exchanger, represents the local (or cell) heat exchange rate, that may either be specified as a constant or a function of the fluid properties. The specified value is added to the source term of the fluid energy equation and subtracted from the source term of the solid energy equation.
- Heat Exchanger Exit Temperature Specification
- Allows you to specify the temperature at the outlet.
- Energy Source Option
- Specifies whether you want to enter an energy source term, and of which type. The energy source corresponds to in Eqn. (1657).
The following values apply to porous regions (SFE, SFT):
- Solid Density
- Specifies the solid density in Eqn. (1846). The fluid density in Eqn. (1846) is the density property that is specified for the fluid continuum. It is entered as a scalar profile.
- Solid Specific Heat
- Specifies the solid specific heat in Eqn. (1840). It is entered as a scalar profile.
- Solid Thermal Conductivity
- Specifies in Eqn. (1846). The fluid thermal conductivity in Eqn. (947) is extracted from the property that is specified for the fluid continuum. It is entered as a tensor profile.
Interface Settings
- Baffle Interface, Porous Baffle Interface
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- Baffle Thermal Option
- Specifies whether the baffle conducts energy.
- Energy Source Option
- Provides energy source options for the interface.
- Blower Interface
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- Blower Heat Generation Rate
- Specifies the heat that is generated by the blower per unit time. This heat is added to the flow that exits the blower.
- Fan Curve Temperature Scaling
- Scales the fan performance curve using data temperature. See Specifying the Fan Curve Temperature Scaling.
- Fan Interface
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- Fan Curve Temperature Scaling
- Scales the fan performance curve using data temperature. See Specifying the Fan Curve Temperature Scaling.
- Fully Developed Interface
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- Fully Developed Energy Option
- Specifies the energy option at the interface.
- Inflow Temperature Specification
- Specifies the temperature option at the interface.
- Contact Interface
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- Thermal Specification
- Allows you to specify the thermal conditions at the interface.
- Energy Source Option
- Provides energy source options for the interface.
- Mapped Contact Interface
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- Energy Coupling Option
- Specifies implicit or explicit coupling of the energy equation across the interface.
- Energy Source Option
- As for Contact Interface.
- Heat Exchanger Interface
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- Heat Exchanger Method
- Specifies the dual stream heat exchanger approach. See The Basic and Actual Dual Stream Heat Exchanger Options.
- Heat Exchanger Data Specification
- For a fluid-fluid type heat exchanger, allows you to set the heat transfer rate. See Heat Exchanger Data Specification Reference.
- Hot Stream Inlet Temperature Specification
- For a fluid-fluid type heat exchanger, allows you to set a target heat rejection rate for the heat exchanger without setting the temperature at the hot inlet. Simcenter STAR-CCM+ then predicts the temperature that is required at the inlet to sustain the heat rejection rate. See Target Heat Rejection.
Segregated Energy Solver Properties
The Segregated Energy solver controls the solution update for the Segregated Fluid Energy model and for the Segregated Solid Energy model.
The following solver and solver options are available:
- Segregated Energy
Fluid Under Relaxation Ramp
Solid Under Relaxation Ramp
AMG Linear Solver
- When the Concentrated Electrolyte electrochemistry model is activated, the segregated energy is solved by the third party Hypre linear equation solver. Hypre provides some of the most commonly-used Krylov-based iterative methods to be used in conjunction with its scalable preconditioners. For more information, see HYPRE.
- Segregated Energy
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- Fluid Under-Relaxation Factor, Solid Under-Relaxation Factor
- In order to promote convergence, these properties are used to under-relax changes of the solution during the iterative process. If residuals show solution divergence and do not decrease, reduce the under-relaxation factors.
- Solver Frozen
- When On, the solver does not update any quantity during an iteration. It is Off by default. This is a debugging option that can result in non-recoverable errors and wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.
- Reconstruction Frozen
- When On, Simcenter STAR-CCM+ does not update reconstruction gradients with each iteration, but rather uses gradients from the last iteration in which they were updated. Activate Temporary Storage Retained in conjunction with this property. This property is Off by default.
- Reconstruction Zeroed
- When On, the solver sets reconstruction gradients to zero at the next iteration. This action means that face values used for upwinding (Eqn. (905)) and for computing cell gradients (Eqn. (917) and Eqn. (918)) become first-order estimates. This property is Off by default. If you turn this property Off after having it On, the solver recomputes the gradients on the next iteration.
- Temporary Storage Retained
- When On, Simcenter STAR-CCM+ retains additional field data that the solver generates during an iteration. The particular data retained depends on the solver, and becomes available as field functions during subsequent iterations. Off by default.
- Enable High-Accuracy Temporal Discretization
- Provides the option of doing 2nd-order time discretization with four or five time levels. See Setting High-Accuracy Temporal Discretization.
Reports
- Heat Exchanger (Dual Stream)
- Uses calculations with an interface between two regions. This technique involves the heat exchange between a cold fluid stream and a hot fluid stream. These streams are modeled as two different physics continua (each having different material properties). See Heat Exchanger.
- Heat Exchanger (Single Stream)
- Uses calculations with one region. By this method, one stream is assumed to have a uniform temperature and the other stream is modeled by specifying the heat exchanger enthalpy source. See Heat Exchanger.
- Heat Transfer
- Reports the total heat transfer at a boundary in W. See Heat Transfer.
- Isentropic Efficiency
- Reports the isentropic efficiency of a process between an inlet boundary (or boundaries) and outlet boundary (or boundaries). See Isentropic Efficiency Report.
- Temperature Correction
- Reports the scaled correction to the temperature calculation at the end of each iteration. See Temperature Correction