Heat Transfer Module
New and Improved Functionality in Version 6.4
Performance Improvements for the Discrete Ordinates Method
In the Radiation in Participating Media and Radiation in Absorbing–Scattering Media interfaces, a new Jacobian Contribution section has been added when the Radiation discretization method is set to Discrete ordinates method. To display this new section, click the Show More Options button and select Advanced Physics Options in the Show More Options dialog.
The checkbox in this section, Use reduced Jacobian, can be used to activate or deactivate the contributions of several terms to the Jacobian matrix. When it is selected (the default), in combination with the improved solver settings of version 6.4, CPU time and memory requirements are significantly decreased, especially for quadrature sets with many directions. The previously used approach remains available by disabling Use reduced Jacobian. To benefit from the new default solver settings for models created in previous versions, reset the solvers to default.
Because this new approach is drastically different and shows great improvements, the Performance index option has been deprecated. The Stabilization section has been renamed Inconsistent Stabilization, and the Use alternative solver with stabilization option now does not have any effect on the solver sequence; it has therefore been renamed Isotropic diffusion since it only adds a stabilization term.
Weighted Sum of Gray Gases Model
In the Radiation in Participating Media interface, a new option, Weighted sum of gray gases model, has been added to the Wavelength dependence of radiative properties input. This option enables modeling of nongray gases as a sum of gray gases. Its main application is in the domain of combustion.
Because of the underlying hypotheses of the model, not all features of the Radiation in Participating Media interface are available with this option.
Handling of refraction in Surface-to-Surface Radiation Interfaces
In the Surface-to-Surface Radiation and Orbital Thermal Loads interfaces, refraction is now handled by the already-existing Semitransparent Surface feature and the new Refractive Interface and Dielectric Window features. When these features are applied on boundaries between domains of different refractive indices, the change of angle of the incident radiation is calculated through Snell’s law. For the Refractive Interface and Dielectric Window features, the directional dependence of surface properties is automatically calculated from the Fresnel relations.
Anisotropic thermal turbulence models
In the Nonisothermal Flow and Reacting Flow multiphysics couplings as well as in the High Mach Number Flow interfaces, it is now possible to use anisotropic thermal turbulence models. The Generalized Gradient-Diffusion Hypothesis (GGDH) model, and its high-order extension (HO-GGDH) are now available to model the anisotropy of the turbulence with respect to the heat equation. These models rely on the Reynolds stress tensor and therefore require a RANS-RSM model to account for turbulence anisotropy in the momentum equation. The RANS-RSM models and anisotropic thermal turbulence models are available with the CFD Module.
Radiation Shield feature for surface-to-surface radiation Interfaces
In the Surface-to-Surface Radiation and Orbital Thermal Loads interfaces, it is now possible to use the Radiation Shield feature. This feature makes it possible to model single-layer and multilayer radiation insulation. Typical application is for modeling shielding of spacecraft and cryogenic systems.
Dielectric Window feature for surface-to-surface radiation Interfaces
In the Surface-to-Surface Radiation and Orbital Thermal Loads interfaces, it is now possible to use the Dielectric Window feature when the Surface-to-surface radiation method is set to Ray shooting. This feature makes it possible to model thin dielectric layers that reflect, absorb, and transmit radiation depending on the angle of incidence. Refraction is also handled by this feature. A typical application is for modeling the wavelength-dependent transmission and loss through windows that can be present in ovens, furnaces, spacecraft, and the built environment.
Improvement of the Reacting Flow multiphysics coupling
In the Reacting Flow multiphysics coupling feature, the definition of the chemical reaction heat source has been updated, simplifying the setup of nonisothermal reacting flow models. This new approach removes the previous limitation on the number of Reaction Source features used in the coupled Transport of Concentrated Species interface and increases modeling flexibility. The total reaction heat source can now either be user defined or automatically synchronized with the Chemistry interface.
Additionally, the Reacting Flow interface now includes heat contributions from equilibrium reactions defined using the Equilibrium Reaction features within the Transport of Concentrated Species interface.
API backward compatibility is not maintained for models that include the Transport of Concentrated Species interface with Reaction Source features in combination with the Reacting Flow coupling.
Miscellaneous Improvements
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In the Heat Transfer interfaces, energy and heat balance variables evaluated on the material frame are now available. For models where the spatial and material frames are different — for example, when a Moving Mesh interface or a physics interface controlling the deformation is used — the balance variables of the material frame are more representative of the computation than the spatial frame’s balance variables. When the frames are identical, so are these two sets of variables.
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In the Surface-to-Surface Radiation and Orbital Thermal Loads interfaces, new variables and Results Templates are available to help with checking the consistency of the model and the details of the radiation method, such as the number of adaptions required by the Hemicube method. These help variables can be found in the list of predefined quantities, in the Consistency check and Radiation method sections, when entering an expression for a plot.
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In the Orbital Thermal Loads interface, new Results Templates have been added to facilitate the analysis of results, showing the orbit in different planes.