Fluent runs on a Windows HPC Cluster with several compute nodes.
If a critical number cores are used the time per iteration increases.
With the same critical number of cores the saving of a dat file can take several hours.
Make sure that Hyperthreading is disabled on all nodes of the cluster.
Depending on the case it is possible that Hyperthreading almost doubles the time for each iteration compared with a simulation with half the number of cores (e.g. 72 HT-cores compared to 36 real cores).
The time to write a dat file during a simulation should not change much if Hyperthreading is disabled.
Active Hyperthreading can increase the time to write a dat file on a cluster by a factor between 4 and 50.
This behavior with active Hyperthreading can only be observed when a sufficient number of cores is used. The exact number may depend on the case and the cluster configuration.
It is recommended to disable Hyperthreading for all Fluent calculations.