Altair ultraFluidX 2020 Release Notes

New Features

New wall modeling framework: Offering a new shear-based wall modeling framework with a two-way coupled interaction of the LBM solver and algebraic and ODE-based wall models, with and without consideration of pressure gradient effects.

Rotating overset grids: Introducing a first version of overset grids for the simulation of truly rotating geometries. The feature can be applied for rotationally symmetric overset grid regions that rotate around one of the principal axes.

User Interface

Introduction of passive parts: Providing a new option to define passive parts that will not be considered in the calculation of aerodynamic coefficients and in the calculation of the projected front surface. The sectional coefficients output is also adjusted accordingly.
Allow reading of multiple STL files: Providing the option to read multiple input STL files via the input solver deck.

Modeling

Part-wise definition of wall model intensity for one-way coupled wall models: When using a one-way coupled version of the ultraFluidX wall model, you can now specify a part-wise intensity parameter to fine-tune the wall model behavior.

Optional user-defined adjustment of the wall model coupling position: Additional expert parameters have been introduced to add more control over the coupling position of the wall model, in cases when manual adjustments are required.

Exposition of additional turbulence modeling parameters: Now offering access to additional physical parameters of the turbulence modeling approaches in the bulk and at the wall.

Revision of the turbulence generator: The turbulence generator extents are now defined via parameters in the input deck and the thickness of the turbulence generation zone is restricted to one voxel. An STL-based definition is not supported anymore.

Output

Enhanced aerodynamic coefficients output: The aerodynamic coefficients file has been updated to a new layout with additional output variables, including separate pressure and friction contributions and the pitch, roll and yaw moments. The file header also now contains additional information.

Option to output surface mesh in STL format after triangle splitting: The surface mesh now can be exported in STL format after the ultraFluidX-internal triangle splitting.

Additional output options for the surface and volume probes: Surface and volume probes now provide the option to choose the variables that are written per probe, in the same manner as the EnSight output. Additional variables have also been introduced.

EnSight export of the probe locations: ultraFluidX now exports additional EnSight files to visualize the probe locations. The respective files contain the voxels (for volume probes) or triangles (for surface probes) that are used for the output.

Calculation of Reynolds stresses: The option to compute and output the time-averaged Reynolds stress tensor has been added.

Output of probe locations and user-defined probe output precision: ultraFluidX now adds the position of the probes that were used to generate the output (i.e., omitting points located in solid regions) to the probe output folder. It is also now possible to switch the probe output to scientific notation and to choose the output precision.

Include automatically generated parts in the partial surface output: Parts that have been created inside ultraFluidX are now included in the partial surface output, if applicable. If, for example, a baffle part is requested in the partial surface output, then its automatically generated inverse part will be included in the corresponding partial surface output.

Monitoring surfaces: The new monitoring surface feature provides an option to monitor field variables on user defined STL surfaces.

Revised selection of output variables: The selection process of output variables via the input deck has been revised. The output of window-averaged quantities has been deactivated by default.

More flexible sectional coefficients output: You can now optionally specify the start and end coordinates of the sectional coefficients output.

Meshing

New threshold for voxels that are very close to the surface: Below a certain minimum wall distance, voxels that are very close to the surface are treated as solid. The threshold value has been optimized to improve the mesh quality.

Other

Improved default MCA parameters for Open MPI: Update of the openmpi-mca-params.conf file with improved values.

Ill-conditioned Smagorinsky turbulence model implementation for very high refinement levels.
Boundary nodes that were not touching the surface might have had a zero normal vector.
Segmentation fault when using too many probes.
Incorrect calculation of sub-grid distances for several specific cases.
Periodic boundary condition sets no-slip boundaries as default at the intersection with the object (if any).
Some probes were not connected to the correct voxels.
No triangle splitting for inverse baffle parts.
Incorrect time scale calculation in the exponential averaging.
Sectional coefficient output did not match the object length in case of object-domain intersections.
Potentially inaccurate normal vectors for under-resolved simulations of non-smooth geometries.
Potential division by zero in turbulence generator.