Best Of
Re: fluent dpm - particle track -view options
You might disable that under File>Preferences then graphics

Re: DEFINE_SDOF_PROPERTIES
The Customization manual does contain an example which you can use for your case. Example 3 If I remember correctly.

Re: How to get solution solved faster in 2D Explicit Dynamics
In ANSYS Help, Mechancial APDL, there is the Material Reference section. In there are many material models. Some of them include Failure Criteria. You will need to do some research and find a material model suitable for brittle fracture. I can't help you more on this. Perhaps someone from ANSYS can answer this question.

Re: How to automate Fluent simulation: First 100 iterations are steady case and next 1000 are Unsteady?
Using Journal File and/ or Automatic Case Changes and Modifications

Re: Workbench: Measure simulation time?
After a Structural model has solved in Mechanical, click on the Solution Information folder and under the first line, select Solution Statistics. The window will show Time to Solve. You can also find the Elapsed Time on the last line of the Solve.out file which shows up in Mechanical in Solution Output.
I generally figure out how long a single design point takes and don't expect them to differ by much so I just multiply the time for one by the number of design points to get an estimate of the total time. If you are doing geometry updates, that can be a significant overhead compared with the solution time if the solution time is very short.

Re: gradient adaption
When you adapt the mesh you more-or-less half the cell length (look at the adaption section in the User's and Theory Guide), this obviously has implications for the courant number. At the same time the refined mesh may pick up some new flow features further reducing the time step required for stable solving. Have a look at the flow field and reduce the time step to suit. Adaptive time stepping can work in some cases, but with dynamic adaption you may find it changes too quickly for the solution: fixed tends to be a little slower but much more stable.

Re: Journal file UDF
Yes for sure. You need to just record the journal and navigate in TUI to execute the commands. The finalized journal can be then used to automate it.

Re: What is the difference between Elastic Support & Ground-body Spring connection?
Rigid and Deformable only applies to a Spring. It doesn't apply to Elastic Support. Elastic Support is like Deformable in that no extra stiffness is added to the model in addition to the spring rate.
Elastic Support is simply a a spring rate per unit area. If you had a face with an area of 16 mm^2 and you wanted a spring rate for the whole face of 2 N/mm then you would use an elastic support with a spring rate of 32 N/mm^3. If you edit the geometry and cut the face area in half, the elastic support will end up being equivalent to a single spring of 4 N/mm.
Here is a good example of an elastic support: https://forum.ansys.com/discussion/19500/how-to-model-a-beam-on-elastic-foundation

Re: Air Lubrication on Ship Hull
I would recommend to do what @Rob mentioned and to focus on 3D runs in order to avoid having uncertainties in dealing with inter-facial scales using 2D solver.

Re: Air Lubrication on Ship Hull
Read through the multiphase & wall film sections of the documentation, and then tell us which model(s) you think you should use and why.
