Altair nanoFluidX 2022 Release Notes

Highlights

Heat Transfer Coefficient (HTC) calculation and export: One of the main motivations for drivetrain oiling simulations is to understand the oil supply and cooling capacity available for different components. Previously, nanoFluidX relied on coupling with AcuSolve to provide this information. This release adds calculation of time-averaged heat transfer coefficients (HTC) directly on the geometry. Thermal analysis is now more convenient and the turn-around time of the process is faster.

Direct export of heat transfer coefficient (HTC): nanoFluidX does have a built in transient thermal solver, but a direct conjugate heat transfer simulation in nanoFluidX is prohibitively expensive. The different timescales of thermal and fluid dynamics mean it is essentially impossible to reach a steady state condition.; Previously, to avoid this time-scale issue nanoFluidX exported a time-averaged flow field to AcuSolve. A conjugate heat transfer simulation was then executed to determine the quasi-steady-state temperatures.; This approach does have limitations, so an option to export time-averaged heat transfer coefficients (HTC) directly on the geometry has been provided. Such an approach makes the thermal analysis more convenient and speeds up the overall turn-around time of the process.

Add ParaView 5.10 State file support: ParaView State files written from nanoFluidX and nFX[c] are now fully compatible with ParaView 5.10.
Run to run reproducibility: Some discrepancies were observed when running a simulation multiple times. Investigation revealed the root cause to be certain GPU programming libraries used by nanoFluidX. This meant the process of addition was not repeated in the same order from run-to-run, leading to round-off errors being accumulated. The latest version of nanoFluidX can enforce order operation and allow for run to run reproducibility, provided the same hardware and software platform.
Use a wrapper file for solver input: nanoFluidX can now accept a .zip file containing the input files (.cfg, .prtl, .txt) as the input in place of separate files.
Removing SPHERE and CUBOID type impose regions: nanoFluidX 2022 deprecates the SPHERE and CUBOID type impose regions, which are superseded by PARALLELEPIPED and CYLINDER shape setups. Considerable background restructuring of these features has taken place, however the UI has been maintained.
Removing legacy inlets and outlets: For a long time nanoFluidX required inlets and outlets to be specified on the domain boundary. This was changed several versions ago and these features are officially being deprecated and replaced by the inlet and outlet regions.

Adhesion coefficient: Adhesion coefficient for the SINGLE_PHASE surface tension model needs to be calibrated against experimental results or visually estimated. Using the Tartakovsky single phase surface tension model is supposed to get around this by using a physical value of the surface tension.

Fix VTK format output for large datasets: Binary output is appended to the file and the position of each property is managed via an offset variable (in bytes). This is handled internally by a 32bit signed integer. This can break when the amount of data is large (>2GB per file), which can happen with a lot of particles per GPU and/or many output variables. The offset counter was updated to 64bit integer to fix this issue. The VTI writer (for interpolated output) and VTP writer (for surface extractor) have also been updated.