New Functionality in Version 4
- A new Conjugate Heat Transfer multiphysics interface (fluid flow, fluid heat transfer, and solid heat transfer) for modeling electronic cooling and heat sinks, for example.
- A new physics interface for Heat Transfer in Porous Media accounts for the effect of a tortuous path, which results in the additional convective thermal dispersion perpendicular to the main flow. The temperature field is thus more accurately described compared to previous implementations.
- A new physics interface for Radiation in Participating Media introduces the effect of absorption of energy in a media subjected to radiation. The radiation pattern from one surface to another then depends on the media present between the radiating or reflecting surfaces.
- The new physics interface for Low-Reynolds Number k-ε Turbulence Model yields a higher accuracy in the description of the flow and heat transfer close to walls.
- The new Open Boundary condition is useful for modeling an open boundary where heat can flow out from the domain or into the domain with a specified exterior temperature.
- Improved stabilization yields increased robustness and higher accuracy for a given computational cost compared to previous versions.
Backward Compatibility vs. 3.5a
k-ε Turbulence Model
The new wall functions have the potential to deliver higher accuracy than the formulation used in 3.5a. They may however require finer wall resolution. Hence, a 3.5a turbulence model can often benefit from an additional boundary layer mesh or refined boundary layer mesh when imported into 4.0a.
k-ω Turbulence Model
The k-ω turbulence model physics interface is not yet implemented in version 4.0a. It is planned for the CFD Module in version 4.1.
Version 4.0a includes automatic translation of models built with the previous k-ω turbulence model. When opened, the full model including initial values and boundary conditions, is converted into using the k-ε turbulence model. Once opened the model can also be also be changed into using the Low-Reynolds k-e turbulence model interface. The latter interface present an excellent alternative for higher accuracy in models including confined flows.
Turbulent Flow with Wall Functions and Heat Transfer in Conjugate Heat Transfer
Highly conductive layers on the interface between a solid and a fluid are not yet fully implemented and give incorrect results when used in combination with wall functions in turbulent flow. This is caused by the incorrect definition of the wall temperature as the average of the solid and fluid temperature in these physics interfaces.
In some case, you can correct this in equation view. Please contact technical support if you run into problems with such a model.
Momentum transport Wall Functions are translated into the revised Wall Functions in 4.0a. The Heat equation Wall Functions are also translated, but the translated formulation uses the default turbulence modeling constants, regardless of the values that were defined in Physics>Scalar Variables in 3.5a.
Surface-to-surface radiation in combination with Turbulent Flow and Heat Transfer
It is currently not possible to include surface-to-surface radiation in models using the coupled turbulent flow and heat transfer interfaces. The reason for this is that the wall temperature is incorrectly defined as the average of the fluid temperature and the solid temperature in version 4.0a.