ANSYS, Inc. Release Notes
CFX |
ANSYS, Inc. Release Notes
This sections highlights differences in the behavior between Release 13.0 and Release 14.0 of ANSYS CFX and CFD-Post.
The Release 14.0 version of CFX-Solver is compatible with the Release 14.0 license server but is not compatible with the Release 13.0 license server.
CFX Distributed Parallel in ANSYS CFX 13 uses HP-MPI while CFX Distributed Parallel in ANSYS CFX 14 uses PCMPI. These different installations of MPI can have a conflict when installed on the same Windows machine. To avoid such a conflict, be sure to follow the installation instructions that appear during Platform MPI installation.
Below is a list of numerics improvements and other changes made for the CFX-Solver in Release 14.0. The changes are believed to be generally helpful and should be reverted only in the event of a problem.
Multiphase Flow
In order to mitigate against convergence difficulties encountered in some multiphase flow problems, the value of the expert parameter ggi ap relaxation is multiplied internally by 0.75. This occurs in the following situation only
Multiphase flow
Non-trivial turbulence dispersion force included
Coupled volume fraction solution algorithm.
Thus, the default value of 1.0 is converted internally to 0.75. If you override the default by a smaller value, then the new value is also multiplied internally by 0.75. This ensures that you retain some control over this parameter. The above restrictions ensure that the numerics changes are focused on a narrow range of problems, hence do not deteriorate convergence of other classes of problems. The changes occur in CS 44468.
Miscellaneous
A bug has been fixed that could cause convergence differences depending on the solver internal memory structure.
A bug has been fixed which could influence the convergence behavior of cases with CEL expressions based on the shear strain rate.
Boundary Conditions/GGI Interfaces
A new default for the intersection method: ‘Direct’ instead of ‘Bitmap’.
The usage of the discernible area fraction parameter has been modified for the direct intersector. This can cause small differences for GGI cases.
Multiphase
A bug has been fixed that permitted coalescence of certain size groups in the MUSIG model. This bug is platform-dependent. The fix can be reverted by setting the expert parameter: ”musig mass coalescence tolerance = 0.0”.
Properties
The default value for the expert parameter 'alternate saturation clipping' has been changed to true. This resolves some incorrect behavior when inverting property tables in which the saturation curve passes through the 2d table, and may lead to different results for cases involving phase change (for example, real gas cavitation and equilibrium phase change).
Miscellaneous
The accuracy of the units [debye,D], [rankine,R] and [revolution,rev] in etc/units.cfx has been improved. This can have an influence on the results if those units are used in the CCL file.
A bug has been fixed in the Bounded CDS advection scheme.
Parallel
The coupled partitioning method has been improved. The requirement that each partition owns at least one core vertex in each domain no longer exists. This can be reverted by setting the following expert parameter: “part_multizone_core_vertex = T”.
This section describes the operational changes, the procedural changes (actions that have to be done differently in this release to get an outcome available in previous releases), and the support changes (functionality that is no longer supported) in Release 14.0 of CFD-Post.
Operational Changes
In Release 13.0, forces at interfaces or cut planes were approximated by adding pressure and mass flow force. However, this calculation will not balance the forces at walls. Release 14.0 has a more accurate calculation of the approximate force, which is derived by subtracting the mass flow force from the pressure force at interfaces and cut planes.
In FLUENT there is an option to have additional post-processing variables written to FLUENT DAT files. There is a change in behavior in the reading of variables from FLUENT files. In Release 13, when selecting to output additional variables in a DAT file in FLUENT (via the Data File Quantities panel), you had to choose only the variables that were not automatically output to DAT file. Otherwise, the chosen variable would show up in CFD-Post with a numerical suffix (for example, you will see 'Velocity 1' in addition to 'Velocity'). As an alternative, you could use the CDAT file format to specify exactly which variables to output to CFD-Post. As of Release 14, when a variable is written to the user-specified section of a DAT file, CFD-Post will check to see if the same variable is available in the basic section of the DAT file. If so, the variable from the basic section will not be read in CFD-Post, only the variables from the user-specified section of the DAT file will be read.
Reading of 13.0 FLUENT cases that have multi-configuration information
can fail in CFD-Post 14.0. A workaround is to set the FLUENT_MULTICONFIG_OFF=1 environment variable before
running CFD-Post.
Procedural Changes
There are no procedural changes in this release.
Support Changes
There are no support changes in this release.